At the end of my thesis I would like to thank all those people who made this thesis possible and an unforgettable experience for me.

First of all, I would like to express my deepest sense of gratitude to my supervisor Prof. Thanks to Tchilalo Boukpessi; TP at 8:00 Am was a good chance for me to catch some of your experience in teaching, and i am happy to work with you in GSE article.

Thanks to Elvire Le Norcy; 6 months in the orthodontics department at Charles Foix (Ivrysur-Seine) hospital was very useful for me especially with your experience. I would like to thank Anne Polliard, Claire Bardet, Sandy Ribes, Julie Lesieur, Benjamin Salmon, Jeremy Sadoine, Benoît Vallée, Sibylle Vital, Céline Gaucher, Marjolaine Gosset, Bernard Pellat, Jean-Louis Saffar, Marie-Laure Colombier, and Philippe Bouchard.

Cedric Mauprivez and Caroline Gorin, we are at the end of our thesis so I hope that everything will be OK.

Thanks to Elisabeth Jimenez for her help in all my administrative problems.

I am thankful to all in EA 2496: Anne-Margaux Collignon, Benjamin Coyac, Maxime Ghighi, Frederic Chamieh, Laurent Detzen, Jean-Baptiste Souron, Annie Llorens, Aurélien Vernon, Cyril Willig, Maheva Garcia, Anita Novais, Sonia Pezet, Tania Selbonne, and Alexandra Benoist.

Special thanks to Jiyar Naji, Xuan Vinh Tran, Soledad Acuña Mendosa, Francesca Mangione, Yong Wu, and Bassam Hassan; you are completely different and I am so happy to work with you.

Thanks to Jotyar Khlaf Arif for his help.

I am thankful to Syrian government who gives me the grant to continue my study in France.

These acknowledgments would not be complete without thanking my family for their constant support and care. Very special thanks to my parents, despite they can't read these words but they know how i appreciate their efforts and their times spent for me.

Finally, I would like to mention two other people who are very important in my life: My wife, Khawla and my little daughter, Nada. I thank Khawla for her encouragement and support, especially in the hardest time. I thank my little daughter for making me so happy with her cute smile which gives me the hope at the most difficult moments. 11 : Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D. [START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure 12 : Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from [START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF] Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from [START_REF] Chaussain | Dentin Matrix Degradation by Host Matrix Metalloproteinases: Inhibition and Clinical Perspectives toward Regeneration[END_REF] Immunostaining with EMMPRIN antibody on sagittal section of the mandible shows that the secretory ameloblasts, the stratum intermedium and odontoblasts are positive for EMMPRIN (A and B). By contrast, no staining is observed in the post-secretory ameloblast (C). Am: ameloblast; s-Am: secretory ameloblast; pos-Am: post-secretory ameloblast; Od: odontoblast; D: dentin; pD: predentin; pm-E: premature enamel; Si: stratum intermedium; fm: forming matrix. From [START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF] 25: TEM analysis was performed on M1 and M2 germs of new born mice. In the KO M2 germs, a cell polarization delay is observed in both pre-ameloblasts and pre-odontoblasts localized at the tip of the cusps (b). In the WT, well-organized ameloblast and odontoblast palisades are seen, with a basal localization of the nuclei and long cell processes (arrowheads) (a), whereas in the KO, cells are seen proliferating with centrally localized nucleus (b). At higher magnification, the basement membrane (black arrows) is partially degraded in WT (white arrows) (c), but appears still intact in the KO (d). In M1germ, the basement membrane which can no longer be detected in the WT (e) is partially degraded in the KO (arrow) (f). Dentin matrix (black arrow-heads) is secreted in both mice models (e-f-g-h) but at a higher rate in the WT (e) where a greater amount of fibrillated collagen is seen associated with hydroxyapatite crystals (white arrow heads). In addition, mineralizing enamel matrix can already be observed at the secreting pole of WT ameloblasts localized at the tip of the cusp (g) but is not detectable in the KO (h). pam: pre-ameloblast; pod: pre-odontoblast; am: ameloblast; od: odontoblast; fde: forming dentin; fen: forming enamel. (own data). ............. 73

Table of figures

General introduction and specific objectives

Tooth development results from reciprocal inductive interactions between the ectomesenchyme and oral epithelium and proceeds through a series of well-defined stages including the initiation, bud, cap and bell stages [START_REF] Ruch | Determinants of morphogénesis and cytodifferentiations of dental anloges in mice[END_REF][START_REF] Slavkin | Embryonic Tooth Formation. A Tool for Developmental Biology[END_REF][START_REF] Catón | Current Knowledge of Tooth Development: Patterning and Mineralization of the Murine Dentition[END_REF][START_REF] Miletich | Normal and Abnormal Dental Development[END_REF]I Thesleff and Hurmerinta 1981;[START_REF] Mitsiadis | Genetic Basis for Tooth Malformations: From Mice to Men and Back Again[END_REF]. At the bell stage which is the last step of tooth crown formation, signals from the dental epithelium (i.e., inner enamel epithelium) instruct dental mesenchymal cells to differentiate into odontoblasts. Differentiated odontoblasts signal back to inner enamel epithelial cells and induce their differentiation into ameloblasts, which are responsible for enamel matrix synthesis. Ameloblast terminal differentiation necessitates the presence of an extracellular matrix that is secreted by odontoblasts and forms the predentin (Zeichner- [START_REF] Zeichner-David | Control of Ameloblast Differentiation[END_REF]. The degradation of the basement membrane (BM) separating the dental epithelium from the mesenchyme is a key step in this process that allows direct contact of ameloblasts with both odontoblasts and the unmineralized dentin matrix [START_REF] Catón | Current Knowledge of Tooth Development: Patterning and Mineralization of the Murine Dentition[END_REF][START_REF] Olive | Does the Basement Membrane Control the Mitotic Activity of the Inner Dental Epithelium of the Embryonic Mouse First Lower Molar[END_REF]. Matrix metalloproteinases (MMPs) are involved in all stages of tooth formation [START_REF] Bourd-Boittin | Matrix Metalloproteinase Inhibition Impairs the Processing, Formation and Mineralization of Dental Tissues during Mouse Molar Development[END_REF][START_REF] Chaussain-Miller | The Role of Matrix Metalloproteinases (MMPs) in Human Caries[END_REF]. At the bell stage, MMPs have a major role in BM degradation [START_REF] Heikinheimo | Expression of Basement Membrane Type IV Collagen and Type IV Collagenases (MMP-2 and MMP-9) in Human Fetal Teeth[END_REF]Sahlberg et al. 1992a), thus allowing direct cross-talk between odontoblasts and ameloblasts [START_REF] Heikinheimo | Expression of Basement Membrane Type IV Collagen and Type IV Collagenases (MMP-2 and MMP-9) in Human Fetal Teeth[END_REF]Sahlberg et al. 1999). It has been shown that at more advanced stages MMPs also regulate the processing of dental extracellular matrix (ECM) proteins prior to mineralization. Indeed, it has been demonstrated that MMPs regulate amelogenin (AMEL) cleavage by enamelysin (MMP-20) during early enamel maturation [START_REF] Bourd-Boittin | Matrix Metalloproteinase Inhibition Impairs the Processing, Formation and Mineralization of Dental Tissues during Mouse Molar Development[END_REF][START_REF] Bourd-Boittin | Immunolocalization of Enamelysin (Matrix Metalloproteinase-20) in the Forming Rat Incisor[END_REF][START_REF] Lu | Functions of KLK4 and MMP-20 in Dental Enamel Formation[END_REF][START_REF] Nagano | Mmp-20 and Klk4 Cleavage Site Preferences for Amelogenin Sequences[END_REF][START_REF] Turk | MMP-20 Is Predominately a Tooth-Specific Enzyme with a Deep Catalytic Pocket That Hydrolyzes Type V Collagen[END_REF][START_REF] Simmer | Expression, Structure, and Function of Enamel Proteinases[END_REF][START_REF] Bartlett | Proteinases in Developing Dental Enamel[END_REF]. The notion of direct epithelial-mesenchymal (or epithelio-stromal) interactions was first introduced in the cancer field when EMMPRIN, a membrane glycoprotein also known as CD147, was identified as a MMP inducer present at the cell surface of tumor cells which can activate stromal cells through direct contact and signal them to increase MMP production [START_REF] Toole | Emmprin (CD147), a Cell Surface Regulator of Matrix Metalloproteinase Production and Function[END_REF]. Recently accumulating data also advocate a role for EMMPRIN in modulating MMP expression during non-tumorigenic pathological conditions as well as in physiological situations such as tissue remodeling and cytodifferentiation events (Gabison, Hoang-Xuan, et al. 2005;Huet, Gabison, et al. 2008;[START_REF] Mohamed | Extracellular Matrix Metalloproteinase Inducer (EMMPRIN/CD147) as a Novel Regulator of Myogenic Cell Differentiation[END_REF][START_REF] Kato | Basigin/CD147 Promotes Renal Fibrosis after Unilateral Ureteral Obstruction[END_REF][START_REF] Nabeshima | Emmprin (basigin/CD147): Matrix Metalloproteinase Modulator and Multifunctional Cell Recognition Molecule That Plays a Critical Role in Cancer Progression[END_REF][START_REF] Liu | The Temporal Expression and Localization of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) during the Development of Perio-Dontitis in an Animal Model[END_REF][START_REF] Gabison | Direct Epithelial-stromal Interaction in Corneal Wound Healing: Role of EMMPRIN/CD147 in MMPs Induction and beyond[END_REF][START_REF] Zhu | CD147: A Novel Modulator of Inflammatory and Immune Disorders[END_REF] . The expression of EMMPRIN in the developing tooth germs was previously described [START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF][START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]. EMMPRIN expression was shown to increase gradually in the forming molar germ in mice from E14 to P1 [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF].

However, the in vivo role of EMMPRIN in tooth development and homeostasis is still unknown. In this PhD, our first specific objective was to investigate EMMPRIN functions in tooth formation using EMMPRIN KO mice by exploring the modifications occurring in their dental phenotype and the consequences on EMMPRIN's molecular targets, in particular on MMPs.

In parallel, EMMPRIN has been shown to be involved in the repair process of different injured tissues. Indeed, the role of EMMPRIN in wound healing through MMP induction and increase in myofibroblast contractile activity has been established [START_REF] Gabison | Differential Expression of Extracellular Matrix Metalloproteinase Inducer (CD147) in Normal and Ulcerated Corneas[END_REF][START_REF] Huet | Extracellular Matrix Metalloproteinase inducer/CD147 Promotes Myofibroblast Differentiation by Inducing Α-Smooth Muscle Actin Expression and Collagen Gel Contraction: Implications in Tissue Remodeling[END_REF]). As our team has developed several pulp injury models to follow-up the repair process, and as we had access to EMMPRIN KO mice it was tempting to study the repair process in this model. Therefore, our second specific objective was to investigate for a potential role of EMMPRIN in the pulp dentin repair process by comparing the healing of injured pulps of EMMPRIN KO and WT mice.

MMPs were shown to be expressed during tooth development and to be necessary for normal dentin formation [START_REF] Bourd-Boittin | Matrix Metalloproteinase Inhibition Impairs the Processing, Formation and Mineralization of Dental Tissues during Mouse Molar Development[END_REF]. After dentin mineralization, they remain trapped in the calcified matrix either under active or proenzyme forms [START_REF] Palosaari | Expression Profile of Matrix Metalloproteinases (MMPs) and Tissue Inhibitors of MMPs in Mature Human Odontoblasts and Pulp Tissue[END_REF], which may explain their persistent presence within the dentin of adult teeth [START_REF] Mazzoni | Zymographic Analysis and Characterization of MMP-2 and -9 Forms in Human Sound Dentin[END_REF][START_REF] Tjäderhane | The Activation and Function of Host Matrix Metalloproteinases in Dentin Matrix Breakdown in Caries Lesions[END_REF]. The role of these trapped MMPs in the progression of the carious process within dentin matrix has been proposed by several studies [START_REF] Tjäderhane | The Activation and Function of Host Matrix Metalloproteinases in Dentin Matrix Breakdown in Caries Lesions[END_REF][START_REF] Sulkala | The Effects of MMP Inhibitors on Human Salivary MMP Activity and Caries Progression in Rats[END_REF]. Indeed, MMPs have been proposed to have an important role in the dentin organic matrix degradation following demineralization by bacterial acids [START_REF] Tjäderhane | The Activation and Function of Host Matrix Metalloproteinases in Dentin Matrix Breakdown in Caries Lesions[END_REF][START_REF] Chaussain-Miller | The Role of Matrix Metalloproteinases (MMPs) in Human Caries[END_REF]. Cariogenic bacteria are essential to initiate the carious process but they cannot degrade the dentin organic matrix. After dissolution of the mineral part, the organic part of dentin becomes exposed to degradation by host-derived enzymes, including salivary and dentinal MMPs, and cysteine cathepsins [START_REF] Nascimento | Cysteine Cathepsins in Human Carious Dentin[END_REF][START_REF] Van Strijp | Host-Derived Proteinases and Degradation of Dentine Collagen in Situ[END_REF]. Because MMPs have been suggested to contribute to dentin caries progression, the hypothesis that MMP inhibition would affect dentin caries progression is appealing. This hypothesis was supported by in vivo studies in rat caries models where dentin caries progression was delayed by intra-oral administration of chemical MMP inhibitors, modified tetracylines and zoledronate [START_REF] Sulkala | The Effects of MMP Inhibitors on Human Salivary MMP Activity and Caries Progression in Rats[END_REF][START_REF] Tjäderhane | The Effect of MMP Inhibitor Metastat on Fissure Caries Progression in Rats[END_REF]. Several natural molecules have been previously reported to have MMP inhibitory properties. Grape-seed extracts (GSE) have been shown to suppress lipopolysaccharide-induced MMP secretion by macrophages and to inhibit MMP-1 and MMP-9 activities in periodontitis [START_REF] La | Grape Seed Extract Suppresses Lipopolysaccharide-Induced Matrix Metalloproteinase (MMP) Secretion by Macrophages and Inhibits Human MMP-1 and -9 Activities[END_REF]). The MMP-inhibitory effects of these natural substances suggest, therefore, that they could be effective in inhibiting dentin caries progression. Recently, a new daily mouthrinse composed of grape-seed extracts and amine fluoride has been developed. As grape-seed extracts are known to be natural inhibitors of MMPs, our last specific objective was to evaluate the capacity of these natural agents to prevent the degradation of demineralized dentin matrix by MMP-3.

Introduction 1.Tooth description

Tooth is the hardest organ of the mammalian body and it provides several functions such as mastication, and phonation.

Anatomically, tooth structure can be distinguished in a visible part (crown) and a hidden part embedded in the alveolar bone of the jaw (root) (Figure 1). Instead of a considerably different shape and size (e.g., an incisor compared with a molar), teeth are histologically similar. Tooth consists of several layers: enamel, dentine, cement, and dental pulp. The enamel is a hard, and acellular structure formed by epithelial cells and supported by dentin. This less mineralized, more resilient, and vital hard connective tissue, is formed and supported by the dental pulp, a soft connective tissue (Figure 1).

In mammals, teeth are attached to the bones of the jaw by the periodontium, consisting of the cementum, periodontal ligament (PDL) and alveolar bone, which provide an attachment with enough flexibility to withstand the forces of mastication.

Human and most of the mammals have two generations of teeth, primary and permanent; since the size of teeth cannot increase after formation, the primary dentition becomes inadequate and must be replaced by more and larger teeth (permanent dentition).

Otherwise, mice have only one generation highly reduced dentition having one incisor, separated from three molars by an edentulous region in each semi-maxilla (Figure 2

.A).

Incisor growth is continuous throughout the animal's life (Figure 2.B).

Tooth development

Since toothed vertebrate have conserved tooth development process stages, data obtained from rodents studies may provide a lot of information about dental development in diverse species, including humans [START_REF] Streelman | The Cusp of Evolution and Development: A Model of Cichlid Tooth Shape Diversity[END_REF].

Organogenesis results from three fundamental processes: I) initiation, within positional information are provided and interpreted to initiate organ formation at the right place; II) morphogenesis, in which cells build up a rudimental organ; finally, III) differentiation where cells form organ-specific structures.

As also showed in mouse tooth development model (Irma Thesleff and Nieminen 1996), teeth are vertebrate-specific structures which, like many other organs, develop through a series of reciprocal interactions between two adjacent tissues, an epithelium and a mesenchyme (I Thesleff, Vaahtokari, and Partanen 1995). Tissue-recombination experiments have shown that the oral epithelium isolated from the mandibular arch of a mouse embryo, between embryonic day 9.0 and 11.5 (E9.0-E11.5), can stimulate a non-dental neural crest-derived mesenchyme to form a tooth. After E11.5, the odontogenic potential subsequently shifts from the epithelium to the mesenchyme, which can induce dental formation when combined with a non-dental epithelium, whereas the dental epithelium has lost this ability [START_REF] Mina | The Induction of Odontogenesis in Non-Dental Mesenchyme Combined with Early Murine Mandibular Arch Epithelium[END_REF][START_REF] Lumsden | Spatial Organization of the Epithelium and the Role of Neural Crest Cells in the Initiation of the Mammalian Tooth Germ[END_REF].

Stages of tooth development

Tooth development takes place through a series of well-defined stages: epithelial thickening of the dental lamina, bud, cap and bell.

Dental lamina Stage

The thickening of the mouse oral epithelium is first visible at around E11.5 (Figure 3). The epithelial thickening forms the dental and vestibular lamina on the lingual and buccal aspect, respectively. The vestibular lamina forms a sulcus between the cheek and the teeth, and the dental lamina gives rise to the teeth. During this stage, dental lamina expresses several important signaling molecules such as (Sonic Hedgehog) Shh that increases cell proliferation at the tooth development site [START_REF] Hardcastle | The Shh Signalling Pathway in Tooth Development: Defects in Gli2 and Gli3 Mutants[END_REF].

Bud stage

After the dental lamina stage, an epithelial structure that has a bud shape results from proliferating and invagination of the epithelium within the underlying ectomesenchyme. The bud is clearly formed at E13.5 and it consists in several layers: the dental follicle made by condensed mesenchymal cells, oriented in a radial pattern and encasing the dental papilla and the enamel organ; enamel organ, in which the internal epithelial cells meets the external epithelial cells and form a structure called the cervical loop; finally, dental papilla, which is a ball of densely packed ectomesenchyme (Figure 4).

Cap stage

Around E14.5, the condensing mesenchyme signals back to the enamel organ and induces the formation of a specific group of signaling epithelial cells known as the enamel knot which takes control of odontogenesis processes (Irma Thesleff, Keranen, and Jernvall 2001). The enamel knot is visible as a bulge in the center of the inner enamel epithelium at the cap stage (Figure 5). Enamel knot expresses a host of signaling molecules, such as Shh, Fgf4, Bmp4 and Wnt10b [START_REF] Vaahtokari | The Enamel Knot as a Signaling Center in the Developing Mouse Tooth[END_REF][START_REF] Sarkar | Expression of Wnt Signalling Pathway Genes during Tooth Development[END_REF].

Then, in multi-cusped teeth, secondary enamel knots guides the differentiation at each cusp tip, during the bell and crown formation stages (Irma Thesleff, Keranen, and Jernvall 2001;[START_REF] Matalova | Cell Lineage of Primary and Secondary Enamel Knots[END_REF].

Bell stage

During this stage (EI7.0 for incisor and by E17.5-18.0 for molars), dental papilla cells differentiate into odontoblasts, beginning in the most anterior mesenchymal cells (Figure 7).

The external dental epithelial cells thickness decreases and becomes a one or two cuboidal cell layer.

The preameloblasts about double in height and differentiate into ameloblasts and their nuclei peripherally placed, this differentiation firstly occurs in the most anterior regions. The lingual side of the incisors does not become coated with enamel because that the internal dental epithelial cells do not differentiate into ameloblasts on this side. At El7.0 these nondifferentiating internal dental epithelial cells, diminish and become cuboidal in shape in subsequent stages of development, then merge with adjacent connective tissue cells.

By EI8 in the incisors and El9 in molars, odontoblasts begin to secrete predentin (Figure 7).

After 24 hours of development, the predentin starts mineralizing and enamel matrix will be secreted by ameloblasts. Mineralization of the enamel matrix is postnatal and the incisors and the first molar erupt by day 20 after birth (P20). Tooth shape will be established when mineralization of dentin and enamel starts.

Second and Third Molar Development

When the jaws elongate enough, the second and third molars start developing. Second molar development starts with the dental lamina, which can be seen at E15.5 forming as an outgrowth of the first molar tooth germ epithelium. By E18.5 the second molar is at the cap stage and erupts approximately at P25. The lamina of the third molar appears at P4, reaches the cap stage by P7-9 and the bell stage by P10, the third molar erupts by P35 [START_REF] Rossant | Mouse Development: Patterning, Morphogenesis, and Organogenesis[END_REF].

Basement membrane

The basement membranes (BM) are the first extracellular matrices to appear and they are critical for organ formation and tissue repair [START_REF] Martin | Laminin and Other Basement Membrane Components[END_REF][START_REF] Kleinman | Basement Membrane Complexes with Biological Activity[END_REF]).

They act like scaffolds for cells and play an essential role in morphogenesis that affects cell adhesion, migration, proliferation, and differentiation.

The structure and components of BMs vary among tissues, resulting in tissue-specific structures and functions. BMs consist of supramolecular structure which is formed by reciprocal interaction of collagen IV, laminin, perlecan, nidogen/entactin, and other molecules [START_REF] Martin | Laminin and Other Basement Membrane Components[END_REF][START_REF] Kleinman | Basement Membrane Complexes with Biological Activity[END_REF].

BM components play an important role in tooth development. They control proliferation, polarity, attachment and determine tooth germ size and morphology (I. Thesleff et al. 1981;[START_REF] Fukumoto | Review: Extracellular Matrix Regulates Tooth Morphogenesis[END_REF][START_REF] Fukumoto | Laminin α5 Is Required for Dental Epithelium Growth and Polarity and the Development of Tooth Bud and Shape[END_REF].

For example, laminin α5 (Lama5), is a component of the major laminin chain in tooth basement membranes. Absence of Lama5 in KO mice lead to a small tooth germ with no cusps, in which the inner dental epithelium is not polarized and enamel knot formation is defective [START_REF] Fukumoto | Laminin α5 Is Required for Dental Epithelium Growth and Polarity and the Development of Tooth Bud and Shape[END_REF].

Another laminins such as laminin α2 (Lama2) are expressed in odontoblasts during the late stage of germ development [START_REF] Yuasa | Laminin α2 Is Essential for Odontoblast Differentiation Regulating Dentin Sialoprotein Expression[END_REF][START_REF] Salmivirta | Glioma Cell Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) (CD147) Stimulates Production of Membrane-Type Matrix Metalloproteinases and Activated Gelatinase A in Co-Cultures with Brain-Derived Fibroblasts[END_REF]. Its deficiency in mice manifests in thin dentin and defective dentinal tube structure [START_REF] Yuasa | Laminin α2 Is Essential for Odontoblast Differentiation Regulating Dentin Sialoprotein Expression[END_REF]). These phenotypes are similar to dentinogenesis imperfecta (DI) in humans. It was found that laminin-2, increases dentin sialoprotein expression in odontoblasts in cell culture, but its deficiency in mutant mice, reduces dentin sialoprotein expression in odontoblasts, suggesting that Lama2 is required for odontoblast differentiation.

Dentin

Dentin structure

Dentin has a complex structure, similar to bone for mineralization ratio of about 70% mineral. In contrast with bone, dentin is not vascularized, and has not remodeling process.

During the secretory stage, odontoblasts polarize, elongate and start to display two distinct parts: a cell body and a process. During the next step of evolution, the cell bodies stay outside the mineralized dentin, along the border of the mineralization front and the processes occupy the lumen of dentin tubules. Tubule diameter varies between 2 and 4 micrometers and its number is about 18 000 and 21 000 tubules per mm 2 [START_REF] Schilke | Comparison of the Number and Diameter of Dentinal Tubules in Human and Bovine Dentine by Scanning Electron Microscopic Investigation[END_REF]. They are more numerous in the inner third layer than the outer third layer of the dentin.

Outer mantel dentin layer

Outer mantel dentin is a thin atubular layer with thickness of 15-30µm, at the periphery of coronal region. It is less mineralized than the rest of dentin and consequently the resilient mantle dentin allow dentin to dissipate pressures which otherwise would induce enamel fissures and detachment of the fragmented enamel from the dentin-enamel junction(R. Z. [START_REF] Wang | Strain-Structure Relations in Human Teeth Using Moiré Fringes[END_REF].

Circumpulpal dentins

The circumpulpal dentin appears as a thin layer at initial stages of dentinogenesis, its thickness continuously increases at the expense of the pulp and then it becomes the largest part of the dentin layer. The circumpulpal dentin is formed by circles of peritubular dentin around the lumen of the tubules separated by the intertubular dentin. The ratio between inter and peritubular dentin is species dependent, it is about 50% in horses and about 10-20% in humans, and in the continuously growing rodent incisors no peritubular dentin can be found.

Several differences in the structure and composition of these two types of dentin are found. In the intertubular dentin, the major protein is type I collagen (90%), whereas in the peritubular dentin no collagen is observed. The differences in the composition of noncollagenous proteins (NCPs) of the two types of dentin have been reported. (M. [START_REF] Goldberg | Effect of 2 methods of demineralization on the on the preservation of glycoproteins and proteoglycans in the intertubular and peritubular dentin in the horse[END_REF][START_REF] Weiner | Peritubular Dentin Formation: Crystal Organization and the Macromolecular Constituents in Human Teeth[END_REF][START_REF] Gotliv | The Composition and Structure of Bovine Peritubular Dentin: Mapping by Time of Flight Secondary Ion Mass Spectroscopy[END_REF][START_REF] Gotliv | Peritubular Dentin, a Vertebrate Apatitic Mineralized Tissue without Collagen: Role of a Phospholipid-Proteolipid Complex[END_REF].

Intertubular dentin (Figure 9) results from transformation of predentin into dentin (Figure 8).

It is compound of dense network of collagen fibrils, coated by NCPs, where needle likecrystallites locate at the collagen fibrils parallel to their axes and other crystallites fill interfibrillar spaces (M. [START_REF] Goldberg | Lipids and Biomineralizations[END_REF]. Adapted from [START_REF] Vital | Tooth Dentin Defects Reflect Genetic Disorders Affecting Bone Mineralization[END_REF] Peritubular dentin result from a passive deposit of serum-derived molecules along the tubule walls and the crystals form a ring around the tubules lumen (Figure 9). In this type of dentin no collagen fibrils are detectable, but a thin network of non-collagenous proteins and phospholipids are visible (M. [START_REF] Goldberg | Effect of 2 methods of demineralization on the on the preservation of glycoproteins and proteoglycans in the intertubular and peritubular dentin in the horse[END_REF][START_REF] Gotliv | Peritubular Dentin, a Vertebrate Apatitic Mineralized Tissue without Collagen: Role of a Phospholipid-Proteolipid Complex[END_REF]; M. [START_REF] Goldberg | Lipids and Biomineralizations[END_REF].

Dentin proteins

Collagens

In the dentin ECM, collagens form a 3D scaffold which is very important in dentinogenesis.

Type I collagen is the major type in dentin matrix collagens (90%), other types of collagen were identified but at lower levels (1-3%) like types III and V collagens [START_REF] Goldberg | CELLS AND EXTRACELLULAR MATRICES OF DENTIN AND PULP: A BIOLOGICAL BASIS FOR REPAIR AND TISSUE ENGINEERING[END_REF][START_REF] Vital | Tooth Dentin Defects Reflect Genetic Disorders Affecting Bone Mineralization[END_REF].

Collagen I formed by gathering of two α1 (I) chains and one α2 (I) chain. These chains entwine to form a triple helix of coiled coil framework [START_REF] Rest | Collagen Family of Proteins[END_REF]. The odontoblasts secrete thin collagen fibril subunits at their apical pole. Lateral fibril subunits assembly leads to fibrillar growth and then straight integration leads to the collagen lengthening.

Noncollagenous proteins (NCPs)

Noncollagenous proteins (NCPs) constitute the remaining 10% of the ECM scaffold and play an essential role in the regulation of bone and dentin mineralization. NCPs are divided into phosphorylated and nonphosphorylated NCPs.

Phosphorylated NCPs

SIBLINGs (Small Integrin Binding LIgand N-linked Glycoproteins), are a phosphoprotein family in which mutations are associated with abnormal phenotypes in the mineralization of bone and/or dentin [START_REF] Qin | Post-Translational Modifications of Sibling Proteins and Their Roles in Osteogenesis and Dentinogenesis[END_REF][START_REF] Vital | Tooth Dentin Defects Reflect Genetic Disorders Affecting Bone Mineralization[END_REF]. This family includes dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP1), bone sialoprotein (BSP), matrix extracellular phosphorylated glycoprotein (MEPE), and osteopontin (OPN).

All SIBLINGs were identified in dentin and bone ECM, but a high rate of DSPP expression was shown to be specific to dentin. The SIBLING members carry an arginineglycineaspartate cell adhesion domain (RGD) and a highly conserved acidic serine and aspartaterich motif (ASARM) (P. S. [START_REF] Rowe | MEPE, a New Gene Expressed in Bone Marrow and Tumors Causing Osteomalacia[END_REF][START_REF] Fisher | Six Genes Expressed in Bones and Teeth Encode the Current Members of the SIBLING Family of Proteins[END_REF]. Noteworthy, the function of ASARM domain in bone and teeth mineralization (apatite crystals nucleator or inhibitor) is at present debated by the scientific community, in particular its implication in pathological processes such as inherited rickets [START_REF] Addison | ASARM Mineralization Hypothesis: A Bridge to Progress[END_REF][START_REF] David | ASARM Mineralization Hypothesis: A Bridge Too Far?[END_REF] Quarles 2010; P. S. N. Rowe 2012). It is of interest that, in addition to binding integrins SIBLINGs, may also specifically bind and activate several MMPs in the ECM suggesting that they could be involved in dentin matrix degradation [START_REF] Fedarko | Three Small Integrin-Binding Ligand N-Linked Glycoproteins (SIBLINGs) Bind and Activate Specific Matrix Metalloproteinases[END_REF]).

Nonphosphorylated NCPs

The second group of NCPs is nonphosphorylated proteins, such as osteonectin (SPARC protein or BM40) and proteins with gamma-carboxylated glutamates (Gla) residues (osteocalcin and matrix Gla protein-MGP-). While osteonectin may contribute to the mineralization process, osteocalcin and MGP have been suggested to regulate HAP crystal nucleation [START_REF] Bronckers | Studies of Osteocalcin Function in Dentin Formation in Rodent Teeth[END_REF][START_REF] Onishi | Hyper-Expression of Osteocalcin mRNA in Odontoblasts of Hyp Mice[END_REF][START_REF] Kaipatur | Matrix Gla Protein Inhibition of Tooth Mineralization[END_REF].

The small leucine-rich proteoglycans (SLRPs), such as decorin, biglycan, fibromodulin, lumican, and osteoadherin, have also been identified in predentin and dentin (M. [START_REF] Goldberg | Glycoconjugates in Dentinogenesis and Dentine[END_REF][START_REF] Goldberg | Proteoglycans in Predentin: The Last 15 Micrometers before Mineralization[END_REF]. They are thought to be involved in the transport of collagen fibrils through the predentin and in collagen fibrillogenesis (M. Goldberg et al. 2003). Predentin is also rich in dermatan and chondroitin sulphate-containing (PG). It is of interest that adjacent to the mineralization front, predentin contains a large quantity of keratan sulphate-containing PG associated with a dramatic decrease in dermatan and chondroitin sulphate-containing PG. This switch in the proteoglycan type was attributed to MMP-3, which is closely related to a control of the dentin mineralization process [START_REF] Hall | Stromelysin-1 (MMP-3) in Forming Enamel and Predentine in Rat Incisor-Coordinated Distribution with Proteoglycans Suggests a Functional Role[END_REF].

Dentinogenesis

At the early stage of tooth development, the dental mesenchyme originates from the neural crest-derived mesenchyme migrate to the oral cavity under the oral epithelium and contribute to the tooth bud formation. During the last mitosis of the proliferate mesenchymal cells the cell located in contact with the basement membrane become preodontoblasts, whereas the daughter cells away from the basement membrane form the Hoehl's layer which constitutes a reservoir for replacing the damaged odontoblasts. After the differentiation odontoblasts become polarized and start to secret the extra cellular matrix components which will be the scaffold for hydroxyapatite (HAP) crystals deposition to form at the end the dentin.

Another classification showed that there are four dentins: Primary dentin, which is formed by odontoblasts which secret this dentin until the tooth becomes functional. Secondary dentin, is secreted by odontoblasts immediately after the end of primary dentin secretion (when the contact of antagonistic cusps is established), and continues throughout life. The major difference between primary and secondary dentins is morphological; in the secondary dentin the S-curve of the tubules is more accentuated. Tertiary reactionary dentin, is synthesized by odontoblasts or, if these cells are destroyed, by the subjacent cells of the Höehl's layer, as a reaction to carious decay, to abrasion or as a response to the release of some components of dental material fillings. Depending the severity and speed of the carious lesion, the age of the patient and the progression of the reaction, it appears as a layer of the osteodentin type, or as a tubular or atubular orthodentin. Tertiary reparative dentin is formed by pulp progenitors, implicated in the formation of a bone-like or in structure-less mineralization (pulp diffuse mineralization or pulp stones). These structures are closer to bone (osteodentin) rather than to dentin (Michel [START_REF] Goldberg | Dentin: Structure, Composition and Mineralization[END_REF]).

Enamel

Enamel is the hardest and outer layer of tooth crown that protects the mammalian tooth from external chemical and physical effects. Enamel properties are associated with its special structural organization and connection with underlying dentin.(Janet Moradian-Oldak 2012).

Mature enamel consists of approximately 4% water and organic material and 96% inorganic materials (Table 1). Enamel inorganic content is a crystalline calcium phosphate (hydroxyapatite) which also is found in dentin, cementum, bone, and calcified cartilage (Antonio Nanci and Cate 2013). The principal structural units of enamel are the rods (prisms) and interrod enamel (interprismatic substance) (Figure 10).

Amelogenin

Amelogenin gene exists only on the X chromosome in rodents [START_REF] Snead | Construction and Identification of Mouse Amelogenin cDNA Clones[END_REF][START_REF] Chapman | Linkage of Amelogenin (Amel) to the Distal Portion of the Mouse X Chromosome[END_REF], while it exists on both X and Y chromosomes In human and cow [START_REF] Lau | Human and Mouse Amelogenin Gene Loci Are on the Sex Chromosomes[END_REF].

Amelogenin constitutes more than 90% of the enamel protein content. It is secreted as a variety of isoforms because of alternative splicing of the amelogenin gene and processing of the parent molecules (C. W. [START_REF] Gibson | Identification of the Leucine-Rich Amelogenin Peptide (LRAP) as the Translation Product of an Alternatively Spliced Transcript[END_REF][START_REF] Lau | Alternative Splicing of the Mouse Amelogenin Primary RNA Transcript Contributes to Amelogenin Heterogeneity[END_REF], the major isoform is about 25 kDa. Amelogenin has a bipolar nature: it contains highly hydrophobic domains and hydrophilic N-and C-terminal sequences and this bipolar nature allows amelogenin monomers by self-assembly to form supramolecular resulting in the formation of nanospheres which regulate crystal spacing [START_REF] Fincham | Self-Assembly of a Recombinant Amelogenin Protein Generates Supramolecular Structures[END_REF][START_REF] Fincham | Amelogenin Proteins of Developing Dental Enamel[END_REF]. The Nterminal A-domain is involved in the formation of nanospheres, whereas the carboxyterminal B-domain prevents their fusion to larger assemblies (J. [START_REF] Moradian-Oldak | Self-Assembly Properties of Recombinant Engineered Amelogenin Proteins Analyzed by Dynamic Light Scattering and Atomic Force Microscopy[END_REF].

Amelogenin has signaling activities (Carolyn W. [START_REF] Gibson | The Amelogenin 'Enamel Proteins' and Cells in the Periodontium[END_REF][START_REF] Veis | Amelogenin Gene Splice Products: Potential Signaling Molecules[END_REF], especially the small isoform; leucine-rich amelogenin peptide (LRAP) [START_REF] Warotayanont | Leucine-Rich Amelogenin Peptide Induces Osteogenesis in Mouse Embryonic Stem Cells[END_REF]). Because of its potential to promote cell differentiation and its interaction with bone cells, it has been used in periodontal regenerative therapies. Amelogenin is not essential for the initiation of mineralization, but is essential for the elongation of enamel crystals and the achievement of proper enamel formation, because in spite of its absence in KO mice, a thin layer of mineralized enamel is formed.

Ameloblastin

Ameloblastin constitutes about 5% of enamel protein. Its expression significantly decrees during enamel maturation. The isolation of this protein is so difficult for several reasons, the limitations in expression and hydrolysis by enamel proteinase MMP-20 as soon as secreted [START_REF] Iwata | Processing of Ameloblastin by MMP-20[END_REF][START_REF] Yamakoshi | Proteomic Analysis of Enamel Matrix Using a Two-Dimensional Protein Fractionation System[END_REF]). In the ameloblastin KO mice, ameloblasts detach from the surface of the developing teeth, suggesting a potential role for ameloblastin in ameloblasts adhesion to the forming enamel [START_REF] Fukumoto | Ameloblastin Is a Cell Adhesion Molecule Required for Maintaining the Differentiation State of Ameloblasts[END_REF]).

Enamelin

Enamelin is the largest enamel protein and constitutes about (3-5%) of enamel proteins. It is a phosphorylated, glycosylated protein and is rapidly cleaved following its secretion. The intact protein is only observed at the mineralization front, so it proposed to be implicated in crystal elongation (C. C. [START_REF] Hu | Cloning and Characterization of Porcine Enamelin mRNAs[END_REF]C. C. Hu et al. 2000).

Enam gene mutations cause an autosomal dominant forms of amelogenesis imperfecta AI [START_REF] Hart | Exclusion of Candidate Genes in Two Families with Autosomal Dominant Hypocalcified Amelogenesis Imperfecta[END_REF] and no true enamel layer is formed in the Enam KO mice(J. C.-C. Hu et al.

2008).

Recently, it was reported that a large increase or decrease in enamelin expression impairs the production of enamel crystals and the prism structure (J. C.-C. [START_REF] Hu | Enamelin Is Critical for Ameloblast Integrity and Enamel Ultrastructure Formation[END_REF].

Enamelin and ameloblastin appear to have similar roles like crystallite initiation and elongation, whereas amelogenin appears to form a framework to allow the continued elongation of the already initiated crystallites (John D. [START_REF] Bartlett | Dental Enamel Development: Proteinases and Their Enamel Matrix Substrates[END_REF].

Tuftelin

Tuftelin is expressed early at the bud stage of tooth development (several days befor the onset of mineralisation) so it is suggested to play a nucleator role during crystals formation. Its expression is also detected in several organs kidney, lung, liver, and testis [START_REF] Zeichner-David | Timing of the Expression of Enamel Gene Products during Mouse Tooth Development[END_REF][START_REF] Macdougall | Cloning, Characterization, and Tissue Expression Pattern of Mouse Tuftelin cDNA[END_REF]).

Sulfated enamel proteins

Sulfated enamel proteins constitute an acidic nature family of proteins with unknown roles.

They are difficult to be detected because of their presence in a small amount (C. E. [START_REF] Smith | Enamel Matrix Protein Turnover during Amelogenesis: Basic Biochemical Properties of Short-Lived Sulfated Enamel Proteins[END_REF].

Amelotin

Amelotin is a glycoprotein recently discovered, its role is not yet clear [START_REF] Iwasaki | Amelotin-a Novel Secreted, Ameloblast-Specific Protein[END_REF].

It is expressed during the secretory stage of enamel development [START_REF] Gao | Distribution of Amelotin in Mouse Tooth Development[END_REF].

Alternatively spliced variants lead to several isoform of amelotin.

Biglycan

Biglycan expression is in the dentin and the enamel [START_REF] Septier | Immunoelectron Microscopic Visualization of pro-and Secreted Forms of Decorin and Biglycan in the Predentin and during Dentin Formation in the Rat Incisor[END_REF]. It is expressed by ameloblasts during tooth development, (M. [START_REF] Goldberg | Biglycan Is a Repressor of Amelogenin Expression and Enamel Formation: An Emerging Hypothesis[END_REF], where it acts as an amelogenin expression repressor (M. [START_REF] Goldberg | Biglycan Is a Repressor of Amelogenin Expression and Enamel Formation: An Emerging Hypothesis[END_REF]M. Goldberg et al. 2005b).

Enamel proteinases

Enamel proteinases are so important for the digestion of enamel proteins and enamel maturation. It was found that some of these proteinases have an ameloblast differentiationdependent expression [START_REF] Lu | Functions of KLK4 and MMP-20 in Dental Enamel Formation[END_REF]).

Matrix metalloproteinase 20 (MMP-20)

Enamelysin (MMP-20) is expressed by ameloblasts and odontoblasts (J. D. [START_REF] Bartlett | Molecular Cloning and mRNA Tissue Distribution of a Novel Matrix Metalloproteinase Isolated from Porcine Enamel Organ[END_REF][START_REF] Fukae | Degradation of Enamel Matrix Proteins in Porcine Secretory Enamel[END_REF], it is expressed from the beginning of secretion stage through the beginning of maturation stage of enamel and cleaves amelogenin, enamelin, and ameloblastin into stable intermediate products [START_REF] Lacruz | Chymotrypsin C (Caldecrin) Is Associated with Enamel Development[END_REF]. In vitro studies showed that Mmp-20 stimulates the formation of nanorod structures formed by co-assembly of the parent amelogenin with its proteolytic products (X. [START_REF] Yang | Amelogenin 'Nanorods' Formation During Proteolysis by Mmp-20[END_REF]. Such assembly alteration was proposed to be related with the elongated growth of apatite crystals. It has been proposed that Mmp-20 activity produces protein intermediate products that will stimulate phase transformation of amorphous calcium phosphate nanoparticles into mineralized hydroxyapatite [START_REF] Kwak | Role of 20-kDa Amelogenin (P148) Phosphorylation in Calcium Phosphate Formation in Vitro[END_REF]).

Kallikrein-4 (KLK4)

Klk-4 is expressed from the end of secretory stage and throughout the maturation stage of enamel [START_REF] Lacruz | Chymotrypsin C (Caldecrin) Is Associated with Enamel Development[END_REF]. Its function is to digest the intermediate products of amelogenin, enamelin and ameloblastin resulting from the MMP-20 action and facilitates enamel proteins removal which is necessary for enamel maturation and hardening (O. [START_REF] Ryu | Porcine Kallikrein-4 Activation, Glycosylation, Activity, and Expression in Prokaryotic and Eukaryotic Hosts[END_REF]. KLK-4 digests the 32-kDa enamelin fragment which is resistant to Mmp-20 action, (Yasuo [START_REF] Yamakoshi | How Do Enamelysin and Kallikrein 4 Process the 32-kDa Enamelin?[END_REF]) and its activity is not affected like MMP-20 by the presence of apatite crystals in vitro (Z. [START_REF] Sun | Apatite Reduces Amelogenin Proteolysis by MMP-20 and KLK4 in Vitro[END_REF]).

Other proteinases 1.2.4.2.3.1 Caldecrin (Ctrc)

Caldecrin Ctrc expression pattern in enamel is similar to Klk4, but lower, and it is predominantly expressed in the maturation stage of amelogenesis [START_REF] Lacruz | Chymotrypsin C (Caldecrin) Is Associated with Enamel Development[END_REF]).

MMP-2

It has been demonstrated that recombinant MMP-2 cleave amelogenin into several fragments in vitro [START_REF] Caron | Gelatinase A (MMP-2) in Developing Tooth Tissues and Amelogenin Hydrolysis[END_REF]. MMP-2 also degraded most forms of amelogenin, suggesting that MMP-2 can participate, with MMP-20, to achieve complete amelogenin processing [START_REF] Bourd-Boittin | Matrix Metalloproteinase Inhibition Impairs the Processing, Formation and Mineralization of Dental Tissues during Mouse Molar Development[END_REF].

MMP-9

Recently, it was proposed that MMP-9 involved in enamel formation and controlling the processing of amelogenin [START_REF] Feng | Binding of Amelogenin to MMP-9 and Their Co-Expression in Developing Mouse Teeth[END_REF]

Enamel formation

Pre-secretory stage

At this stage, ameloblasts start expressing very small amounts of enamel proteins even before the basement membrane break up and send cytoplasmic projections through the gaps directly after basement membrane disintegrate. With the disappearance of the basement membrane, dentin starts to mineralize and the apical surfaces of ameloblasts connect with the superficial collagen fibrils of the mantle dentin [START_REF] Meckel | Structure of Mature Human Dental Enamel as Observed by Electron Microscopy[END_REF][START_REF] Cevc | The Caries Resistance of Human Teeth Is Determined by the Spatial Arrangement of Hydroxyapatite Microcrystals in the Enamel[END_REF] (Figure 12).

Secretory Stage

At the beginning, ameloblasts secrete enamel proteins on top of and around existing dentin crystals initially and then around enamel crystals and into the space of disappeared basement membrane (Figure 11.A). With the continued secretion of enamel matrix, ameloblasts move back to create the necessary space for continuous deposition of enamel end this moment we can distinguish the initial enamel layer which is aprismatic (not separated into rod and interrod enamel) Secretory ameloblasts develop a novel cell extension called Tomes' process at their apical (secretory) ends. This extension which has secretory and nonsecretory regions provides the architectural basis for organizing enamel crystals into rod and interrod enamel, [START_REF] Meckel | Structure of Mature Human Dental Enamel as Observed by Electron Microscopy[END_REF][START_REF] Cevc | The Caries Resistance of Human Teeth Is Determined by the Spatial Arrangement of Hydroxyapatite Microcrystals in the Enamel[END_REF].

Secretory ameloblasts secrete enamel proteins which concentrate along the ameloblast secretory membrane and form a mineralization front (there is no pre-enamel like the predentin in dentin or osteoid in bone). The mineralization front retreats with the Tomes' process as the enamel crystals grow in length (4µm/day) [START_REF] Risnes | Enamel Apposition Rate and the Prism Periodicity in Human Teeth[END_REF], and the ameloblasts continue their secretion of enamel proteins (Figure 12). During this stage enamel crystals grow primarily in length and the enamel layer thickens. [START_REF] Smith | Cellular and Chemical Events During Enamel Maturation[END_REF]. This process is necessary to have a harde and mature enamel layer, and is directed by modulating ameloblasts that cycle through smooth and ruffle-ended phases.

During maturation stage a basal lamina is secreted at the base of the ameloblasts (Figure 12). Recently amelotin ( AMTN ) has been identified as one of the components of this basal lamina [START_REF] Iwasaki | Amelotin-a Novel Secreted, Ameloblast-Specific Protein[END_REF][START_REF] Moffatt | Cloning of Rat Amelotin and Localization of the Protein to the Basal Lamina of Maturation Stage Ameloblasts and Junctional Epithelium[END_REF]. Adapted from [START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]

Matrix MetalloProteinases MMPs

MMPs is subdivided into soluble and membrane-type MMPs (MT-MMPs). The soluble MMPs are expressed as pro-enzymes that will be activated in the extracellular environment.

MT-MMPs are intracellularly activated and identified as activators of soluble MMPs and were shown to be able to degrade extracellular matrix proteins ECM [START_REF] Hamacher | Extrazelluläre Matrix -von der Grundlagenforschung zur klinischen Bedeutung: Eine Übersicht unter besonderer Berücksichtigung der Matrix Metalloproteinasen[END_REF].

In addition to the inhibition by endogenous inhibitors (tissue inhibitor of MMPs TIMP) or to the proteolytic activation of pro-MMPs, MMPs are regulated by cytokines or growth factors transcriptionally [START_REF] Tsuruda | Matrix Metalloproteinases: Pathways of Induction by Bioactive Molecules[END_REF] MMPs are implicated in inflammation by regulating the availability and the activity of cytokines, chemokines, and growth factors, as well as integrity of tissue barriers. MMPs are also involved in tumors [START_REF] Nissinen | Matrix Metalloproteinases in Inflammation[END_REF].

MMPs and teeth

In physiological processes (development)

Several MMPs have been detected in developing tooth tissues [START_REF] Goldberg | Immunohistochemical Localization of MMP-2, MMP-9, TIMP-1, and TIMP-2 in the Forming Rat Incisor[END_REF].

They play a central role in the disruption of basement membrane. MMPs are also implicated in the functional regulation of growth factors and their receptors, cytokines and chemokines, adhesion receptors and cell surface proteoglycans, and a variety of enzymes (H. [START_REF] Li | The role of matrix metalloproteinases in extracellular matrix remodelling in chronic obstructive pulmonary disease rat models[END_REF]. MMPs participate in the remodeling of the ECM during tooth development to facilitate the migration of cells and the mesenchymal condensation [START_REF] Chin | Matrix Metalloproteinases Regulate Morphogenesis, Migration and Remodeling of Epithelium, Tongue Skeletal Muscle and Cartilage in the Mandibular Arch[END_REF] and participate in the regulation of the mineralization process of dental hard tissues by cleaving the matrix proteins of the dentin and the enamel matrix [START_REF] Simmer | Expression, Structure, and Function of Enamel Proteinases[END_REF][START_REF] Fanchon | Involvement of Matrix Metalloproteinases in the Onset of Dentin Mineralization[END_REF]).

MMP-1, -2, -3, -9 and MT1-MMP have been detected during tooth development, indicating that these MMPs have roles in tooth morphogenesis and eruption [START_REF] Chin | Matrix Metalloproteinases Regulate Morphogenesis, Migration and Remodeling of Epithelium, Tongue Skeletal Muscle and Cartilage in the Mandibular Arch[END_REF]Sahlberg et al. 1992b;[START_REF] Caron | Expression and Localization of Membrane Type 1 Matrix Metalloproteinase in Tooth Tissues[END_REF][START_REF] Randall | Temperospatial Expression of Matrix Metalloproteinases 1, 2, 3, and 9 during Early Tooth Development[END_REF][START_REF] Yoshiba | Temporospatial Gene Expression and Protein Localization of Matrix Metalloproteinases and Their Inhibitors during Mouse Molar Tooth Development[END_REF].

In pathological processes

Periodontitis

High MMPs levels were detected in the periodontitis and apical periodontitis leading to accelerated matrix degradation, (de Paula e [START_REF] Paula E Silva | High Matrix Metalloproteinase Activity Is a Hallmark of Periapical Granulomas[END_REF][START_REF] Garcia | Matrix Metalloproteinase Expression in Teeth with Apical Periodontitis Is Differentially Modulated by the Modality of Root Canal Treatment[END_REF]. Collagenases (MMP-1, MMP-8, and MMP-13) and gelatinases (MMP-2 and MMP-9) are implicated in the digestion of collagen in the bone and periodontal ligament [START_REF] Andonovska | Matrix Metalloproteinases (MMP-1, -8, -13) in Chronic Periapical Lesions[END_REF][START_REF] Corotti | Immunolocalization of Matrix Metalloproteinases-2 and -9 during Apical Periodontitis Development[END_REF].

In the caries process

We developed this point (Figure 13) in Chaussain, Boukpessi, Khaddam et al, 2013 (end of introduction). EMMPRIN (Basigin) has four isoforms (basigin-1 to -4), caused by alternative transcription initiation and variation in splicing (Figure 14) [START_REF] Belton | Basigin-2 Is a Cell Surface Receptor for Soluble Basigin Ligand[END_REF]) and the major isoform is basigin-2. EMMPRIN is highly glycosylated, Its protein portion is 27 kDa, and its glycosylated form is 43 to 66 kDa [START_REF] Miyauchi | Basigin, a New, Broadly Distributed Member of the Immunoglobulin Superfamily, Has Strong Homology with Both the Immunoglobulin V Domain and the β-Chain of Major Histocompatibility Complex Class II Antigen[END_REF]) and the nonglycosylated form has the ability to induce MMP expression in fibroblasts as the glycosylated form [START_REF] Belton | Basigin-2 Is a Cell Surface Receptor for Soluble Basigin Ligand[END_REF]) The extracellular domain has two immunoglobulin domains (a N-terminally located D1 domain and a more C-terminally located D2 domain) (Figure 15) and three potential Asparagine (Asn)-glycosylation sites; one in D1 domain and two in D2 domain [START_REF] Miyauchi | Basigin, a New, Broadly Distributed Member of the Immunoglobulin Superfamily, Has Strong Homology with Both the Immunoglobulin V Domain and the β-Chain of Major Histocompatibility Complex Class II Antigen[END_REF][START_REF] Miyauchi | The Basigin Group of the Immunoglobulin Superfamily: Complete Conservation of a Segment in and around Transmembrane Domains of Human and Mouse Basigin and Chicken HT7 Antigen[END_REF].

Structure

Transmembrane form

The transmembrane domain has glutamic acid in its center, and is completely conserved between human, mouse and chicken [START_REF] Miyauchi | The Basigin Group of the Immunoglobulin Superfamily: Complete Conservation of a Segment in and around Transmembrane Domains of Human and Mouse Basigin and Chicken HT7 Antigen[END_REF], this domain is important for interactions with other proteins in the same membrane. [START_REF] Gabison | Direct Epithelial-stromal Interaction in Corneal Wound Healing: Role of EMMPRIN/CD147 in MMPs Induction and beyond[END_REF].

Soluble form

The soluble form of CD147 has been detected in conditioned media as:

 full-length protein (Taylor et al. 2002)  or as part of shed microvesicles [START_REF] Sidhu | The Microvesicle as a Vehicle for EMMPRIN in Tumor-stromal Interactions[END_REF]  as well as in forms lacking the transmembrane and cytoplasmic domain derived from MMP mediated cleavage of CD147 from the cell surface [START_REF] Haug | Oxidized Low-Density Lipoproteins Stimulate Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) Release by Coronary Smooth Muscle Cells[END_REF]Y. Tang et al. 2006;[START_REF] Egawa | Membrane Type 1 Matrix Metalloproteinase (MT1-MMP/MMP-14) Cleaves and Releases a 22-kDa Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) Fragment from Tumor Cells[END_REF]

Phenotypes of EMMPRIN knock out (KO) mice

EMMPRIN KO mice have a low reproduction level which is at a much lower frequency than that expected by Mendelian segregation, KO embryos develop normally during blastocyst stage but at the time of implantation, about 75% of the null embryos are lost [START_REF] Igakura | A Null Mutation in Basigin, an Immunoglobulin Superfamily Member, Indicates Its Important Roles in Peri-Implantation Development and Spermatogenesis[END_REF]) and half of the surviving mice had interstitial pneumonia and died within 4 weeks after birth [START_REF] Igakura | A Null Mutation in Basigin, an Immunoglobulin Superfamily Member, Indicates Its Important Roles in Peri-Implantation Development and Spermatogenesis[END_REF]. EMMPRIN KO mice have a defect in the capability of implantation of the uterus (female), arrested spermatogenesis (male) [START_REF] Igakura | A Null Mutation in Basigin, an Immunoglobulin Superfamily Member, Indicates Its Important Roles in Peri-Implantation Development and Spermatogenesis[END_REF][START_REF] Kuno | Female Sterility in Mice Lacking the Basigin Gene, Which Encodes a Transmembrane Glycoprotein Belonging to the Immunoglobulin Superfamily[END_REF], abnormal behavior [START_REF] Naruhashi | Abnormalities of Sensory and Memory Functions in Mice LackingBsgGene[END_REF], deficits in vision [START_REF] Hori | Retinal Dysfunction in Basigin Deficiency[END_REF] and a decreased response to odor [START_REF] Igakura | Roles of Basigin, a Member of the Immunoglobulin Superfamily, in Behavior as to an Irritating Odor, Lymphocyte Response, and Blood-Brain Barrier[END_REF].

EMMPRIN interactions

Three possible EMMPRIN interactions were descriped (Figure 16):

-Homophilic cis interaction between EMMPRIN molecules within the plasma membrane of the same tumor cell [START_REF] Yoshida | Homo-Oligomer Formation by Basigin, an Immunoglobulin Superfamily Member, via Its N-Terminal Immunoglobulin Domain[END_REF].

-Homophilic trans interaction between EMMPRIN molecules on tumoral cells.(J. Sun EMMPRIN has multiple binding partners, one of them, a family of monocarboxylic acid transporters (MCTs) [START_REF] Kirk | CD147 Is Tightly Associated with Lactate Transporters MCT1 and MCT4 and Facilitates Their Cell Surface Expression[END_REF][START_REF] Halestrap | The Monocarboxylate Transporter family-Structure and Functional Characterization[END_REF]) which transport monocarboxylic acids such as lactate, pyruvate and ketone bodies into and from the cells. Among the four MCTs (MCT1, MCT2, MCT3 and MCT4), EMMPIN binds to MCT1, MCT3 and MCT4 in the same membrane, and is essential for their transfer to the cell surface. An EMMPRIN dimer binds two MCT1 [START_REF] Wilson | Fluorescence Resonance Energy Transfer Studies on the Interaction between the Lactate Transporter MCT1 and CD147 Provide Information on the Topology and Stoichiometry of the Complex in Situ[END_REF].

Integrins

It was shown that EMMPRIN associates with integrin α3 β1 and α6 β1 in the same membrane [START_REF] Berditchevski | Generation of Monoclonal Antibodies to Integrin-Associated Proteins EVIDENCE THAT α3β1 COMPLEXES WITH EMMPRIN/BASIGIN/OX47/M6[END_REF], for example in extraembryonic membrane apposition in D. melanogaster [START_REF] Reed | Integrin-Dependent Apposition of Drosophila Extraembryonic Membranes Promotes Morphogenesis and Prevents Anoikis[END_REF]) and in the visual system of D. melanogaster [START_REF] Curtin | Basigin (EMMPRIN/CD147) Interacts with Integrin to Affect Cellular Architecture[END_REF].

Caveolin-1

Caveolin is a family of proteins form the major constituents of caveolae, within the plasma membranes of most cells that mediate the transcytosis of macromolecules in a clathrinindependent manner [START_REF] Williams | Caveolin-1 in Oncogenic Transformation, Cancer, and Metastasis[END_REF] and comprised of three isoforms (caveolins 1, 2 and 3), only one of them caveolin-1 has been shown to associate with EMMPRIN. The association starts within the Golgi apparatus, where caveolin-1 binds to and guard the lower glycosylated forms of EMMPRIN to the plasma membrane, thus prevents the formation of, highly glycosylated species of EMMPRIN by the self-aggregating, which is responsible for MMP production (W. [START_REF] Tang | Links between CD147 Function, Glycosylation, and Caveolin-1[END_REF].

Caveolin-1 serves as a negative regulator of EMMPRIN; by the direct association with the second Ig domain of EMMPRIN which decrease EMMPRIN clustering and resulted in decreased MMP production (W. Tang and Hemler 2004).

Recently, an opposite effect of caveolin-1 is demonstrated. The increased caveolin-1 expression results in an increased proportion of highly glycosylated EMMPRIN relative to the lower glycosylated form and increased production of MMP-11 and higher invasiveness.

In the same study down-regulation of caveolin-1 resulted in a decrease in highly glycosylated EMMPRIN [START_REF] Jia | Caveolin-1 up-Regulates CD147 Glycosylation and the Invasive Capability of Murine Hepatocarcinoma Cell Lines[END_REF]. Regardless of the outcome of these studies, the expression of EMMPRIN glycosylation forms is functionally linked with caveolin-1 expression.

EMMPRIN interactions with external molecules

Cyclophilin

Cyclophilin A is secreted from cells exhibit high level chemotactic activity to leukocytes and is involved in the inflammation, so it is the target protein of an immunosuppressive drug, cyclosporine A. Several studies confirmed that EMMPRIN is the receptor for cyclophilin A (V. [START_REF] Yurchenko | Cyclophilin-CD147 Interactions: A New Target for Anti-Inflammatory Therapeutics[END_REF][START_REF] Yurchenko | Active Site Residues of Cyclophilin A Are Crucial for Its Signaling Activity via CD147[END_REF], and for cyclophilin B (V. [START_REF] Yurchenko | Cyclophilin-CD147 Interactions: A New Target for Anti-Inflammatory Therapeutics[END_REF]. The affinity between cyclophilin A and the extracellular region of EMMPRIN is weak, but it is strong with the transmembrane region [START_REF] Schlegel | Solution Characterization of the Extracellular Region of CD147 and Its Interaction with Its Enzyme Ligand Cyclophilin A[END_REF]).

EMMPRIN

Recently it has shown that nonglycosylated EMMPRIN ectodomains form dimer, and then interact with EMMPRIN on target cells [START_REF] Belton | Basigin-2 Is a Cell Surface Receptor for Soluble Basigin Ligand[END_REF]. During internalization, EMMPRIN associates with another form of EMMPRIN (basigin-3 [START_REF] Belton | Basigin-2 Is a Cell Surface Receptor for Soluble Basigin Ligand[END_REF].

Platelet glycoprotein VI (GPVI)

Recently, platelet glycoprotein VI (GPVI) has been identified as a novel receptor for EMMPRIN and can mediate platelet rolling via [START_REF] Seizer | EMMPRIN (CD147) Is a Novel Receptor for Platelet GPVI and Mediates Platelet Rolling via GPVI-EMMPRIN Interaction[END_REF]).

EMMPRIN functions

In physiological processes

Tissue repair/remodeling

The balance between MMP-induced stromal remodeling/restoration and stromal destruction is so delicate. EMMPRIN has been proposed as a mediator for this balance directly via a feedback mechanism that links the affected epithelial cells with neighboring fibroblasts (Gabison, Hoang-Xuan, et al. 2005).

In corneal ulcerations the protective epithelial barrier of the eye is damaged, leaving eye open to infection by bacteria, viruses and fungi and, if left untreated, they can result in blindness.

EMMPRIN has been detected in both healthy and ulcerated corneas but was found at greater levels within ulcerated specially at the areas of greater MMP expression [START_REF] Gabison | Differential Expression of Extracellular Matrix Metalloproteinase Inducer (CD147) in Normal and Ulcerated Corneas[END_REF]. Within the cardiovascular system, the balance is also delicate. MMP expression is critical for the prevention of hypertension and, at the same time, implicated in the progression of congestive heart failure (CHF) [START_REF] Spinale | A Matrix Metalloproteinase Induction/Activation System Exists in the Human Left Ventricular Myocardium and Is Upregulated in Heart Failure[END_REF][START_REF] Ergul | Downregulation of Vascular Matrix Metalloproteinase Inducer and Activator Proteins in Hypertensive Patients[END_REF]).

Chaperone functions

It was shown that In MCT-transfected cells, the MCT1 and MCT4 expressed protein accumulated in a perinuclear compartment, and it was found that co-transfection with CD147 enabled plasma membrane expression of active MCT1 or MCT4. Showing that EMMPRIN facilates proper expression of MCT1 and MCT4 at the cell surface and have a chaperone function [START_REF] Kirk | CD147 Is Tightly Associated with Lactate Transporters MCT1 and MCT4 and Facilitates Their Cell Surface Expression[END_REF].

Implantation

Since MMPs are required in implantation [START_REF] Alexander | Expression and Function of Matrix Metalloproteinases and Their Inhibitors at the Maternal-Embryonic Boundary during Mouse Embryo Implantation[END_REF][START_REF] Werb | ECM and Cell Surface Proteolysis: Regulating Cellular Ecology[END_REF], defective implantation result from mis-regulation of MMP production due to lack of EMMPRIN stimulation in EMMPRIN KO mice.

Spermatogenesis

EMMPRIN is strongly expressed in spermatocytes [START_REF] Igakura | A Null Mutation in Basigin, an Immunoglobulin Superfamily Member, Indicates Its Important Roles in Peri-Implantation Development and Spermatogenesis[END_REF]) and its absence in EMMPRIN KO mice, leads to arrest spermatogenesis at the stage of differentiation of primary spermatocytes into secondary spermatocytes at the metaphase of the first meiosis [START_REF] Igakura | A Null Mutation in Basigin, an Immunoglobulin Superfamily Member, Indicates Its Important Roles in Peri-Implantation Development and Spermatogenesis[END_REF].

Retinal development and maintenance

EMMPRIN mediates MCTs transport to the plasma membrane so MCT1, MCT3 and MCT4 were found to be deficient at the plasma membrane of the retinal pigment epithelia, which leads abnormal photoreceptor function and blindness [START_REF] Hori | Retinal Dysfunction in Basigin Deficiency[END_REF][START_REF] Philp | Loss of MCT1, MCT3, and MCT4 Expression in the Retinal Pigment Epithelium and Neural Retina of the 5A11/Basigin-Null Mouse[END_REF].

Cell interactions

EMMPRIN mediates the adhesive cell interactions, like in the embryonic retinal cell aggregation and influences glial cell maturation [START_REF] Fadool | 5A11 Antigen Is a Cell Recognition Molecule Which Is Involved in Neuronal-Glial Interactions in Avian Neural Retina[END_REF].

Hematopoetic cell activation and erythrocytes circulation

It was found that EMMPRIN plays a role in hematopoietic cell activation as during dendritic cell differentiation [START_REF] Cho | The Functional Interactions between CD98, β1-Integrins, and CD147 in the Induction of U937 Homotypic Aggregation[END_REF][START_REF] Spring | The Oka Blood Group Antigen Is a Marker for the M6 Leukocyte Activation Antigen, the Human Homolog of OX-47 Antigen, Basigin and Neurothelin, an Immunoglobulin Superfamily Molecule That Is Widely Expressed in Human Cells and Tissues[END_REF]). Furthermore, It has been shown that EMMPRIN is expressed in erythrocyte lineage cells, including mature erythrocytes and blocking EMMPRIN by the injection of a monoclonal antibody in the mice causes selective trapping of erythrocytes in the spleen [START_REF] Coste | Unavailability of CD147 Leads to Selective Erythrocyte Trapping in the Spleen[END_REF].

Other

EMMPRIN is implicated in other several physiological processes like neural network formation and development [START_REF] Schlosshauer | Neurothelin: Molecular Characteristics and Developmental Regulation in the Chick CNS[END_REF][START_REF] Fadool | 5A11 Antigen Is a Cell Recognition Molecule Which Is Involved in Neuronal-Glial Interactions in Avian Neural Retina[END_REF], restriction of synaptic bouton size [START_REF] Besse | The Ig Cell Adhesion Molecule Basigin Controls Compartmentalization and Vesicle Release at Drosophila Melanogaster Synapses[END_REF], calcium transport (J. L. [START_REF] Jiang | The Involvement of HAb18G/CD147 in Regulation of Store-Operated Calcium Entry and Metastasis of Human Hepatoma Cells[END_REF]), neutrophil chemotaxis (Vyacheslav Yurchenko et al. 2002), and blood -brain barrier development [START_REF] Schlosshauer | The Blood-Brain Barrier: Morphology, Molecules, and Neurothelin[END_REF].

In pathological processes

Cancer

High levels of EMMPRIN were reported in numerous malignant tumors including bladder, skin, lung and breast carcinoma, and lymphoma [START_REF] Polette | Tumor Collagenase Stimulatory Factor (TCSF) Expression and Localization in Human Lung and Breast Cancers[END_REF][START_REF] Bordador | Expression of EMMPRIN by Oral Squamous Cell Carcinoma[END_REF][START_REF] Thorns | EMMPRIN (CD 174) Is Expressed in Hodgkin's Lymphoma and Anaplastic Large Cell Lymphoma. An Immunohistochemical Study of 60 Cases[END_REF], and were also associated with poor prognosis [START_REF] Kanekura | Basigin (cd147) Is Expressed on Melanoma Cells and Induces Tumor Cell Invasion by Stimulating Production of Matrix Metalloproteinases by Fibroblasts[END_REF][START_REF] Davidson | Matrix Metalloproteinases (MMP), EMMPRIN (extracellular Matrix Metalloproteinase Inducer) and Mitogen-Activated Protein Kinases (MAPK): Co-Expression in Metastatic Serous Ovarian Carcinoma[END_REF][START_REF] Davidson | EMMPRIN (extracellular Matrix Metalloproteinase Inducer) Is a Novel Marker of Poor Outcome in Serous Ovarian Carcinoma[END_REF][START_REF] Ishibashi | CD147 and Matrix Metalloproteinase-2 Protein Expression as Significant Prognostic Factors in Esophageal Squamous Cell Carcinoma[END_REF].

EMMPRIN induces several malignant properties associated with cancer. These include:

MMPs

Tumorigenic cells expressing EMMPRIN induce MMP expression by neighboring stromal cells (Figure 17) [START_REF] Biswas | Tumor Cell Stimulation of Collagenase Production by Fibroblasts[END_REF][START_REF] Kataoka | Tumor Cell-Derived Collagenase-Stimulatory Factor Increases Expression of Interstitial Collagenase, Stromelysin, and 72-kDa Gelatinase[END_REF][START_REF] Biswas | The Human Tumor Cell-Derived Collagenase Stimulatory Factor (Renamed EMMPRIN) Is a Member of the Immunoglobulin Superfamily[END_REF] and regulates MMP production at the transcription level by a mitogen activated protein kinase(MAPK) p38 pathway [START_REF] Lim | Tumor-Derived EMMPRIN (extracellular Matrix Metalloproteinase Inducer) Stimulates Collagenase Transcription through MAPK p38[END_REF][START_REF] Lai | Differential Regulation of Lipopolysaccharide-Induced Monocyte Matrix Metalloproteinase (MMP)-1 and MMP-9 by p38 and Extracellular Signal-Regulated Kinase 1/2 Mitogen-Activated Protein Kinases[END_REF]. Both recombinant EMMPRIN and tumoral EMMPRIN have been shown to induce the expression of collagenase I (MMP-1), gelatinase A (MMP-2), stromelysin-1 (MMP-3), and membrane type 1-and type 2-MMPs (MT1-and MT2-MMP) by fibroblasts [START_REF] Cao | Expression of Extracellular Matrix Metalloproteinase Inducer and Enhancement of the Production of Matrix Metalloproteinase-1 in Tongue Squamous Cell Carcinoma[END_REF]J. Sun and Hemler 2001;R. Li et al. 2001;[START_REF] Salmivirta | Glioma Cell Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) (CD147) Stimulates Production of Membrane-Type Matrix Metalloproteinases and Activated Gelatinase A in Co-Cultures with Brain-Derived Fibroblasts[END_REF].

In situ hybridization analyses of both tumor and peri-tumoral fibroblasts in different organs like breast, colon, lung, skin and head/neck tumors showed that EMMPRIN expression is primarily tumor associated, while MMP expression is fibroblast associated [START_REF] Pyke | Localization of Messenger RNA for Mr 72,000 and 92,000 Type IV Collagenases in Human Skin Cancers by in Situ Hybridization[END_REF][START_REF] Majmudar | Increased Expression of Matrix Metalloproteinase-3 (stromelysin-1) in Cultured Fibroblasts and Basal Cell Carcinomas of Nevoid Basal Cell Carcinoma Syndrome[END_REF][START_REF] Noël | Coordinate Enhancement of Gelatinase A mRNA and Activity Levels in Human Fibroblasts in Response to Breast-Adenocarcinoma Cells[END_REF][START_REF] Heppner | Expression of Most Matrix Metalloproteinase Family Members in Breast Cancer Represents a Tumor-Induced Host Response[END_REF][START_REF] Polette | Tumor Collagenase Stimulatory Factor (TCSF) Expression and Localization in Human Lung and Breast Cancers[END_REF].

EMMPRIN can induce EMMPRIN and MMP expression in far stromal cells by its soluble form which result from proteolytic cleavage of the carboxy terminus, and is thought to help metastasis to distant sites (Y. Tang et al. 2004).

Recently, another mechanism for MMP stimulation in distant cells was described. It was found that EMMPRIN expressed by malignant testicular cells by membrane vesicles (MVs) secreted from these cells, can exert its MMP inducing effect on distant cells within the tumor microenvironment to promote tumor invasion [START_REF] Milia-Argeiti | EMMPRIN/CD147-Encriched Membrane Vesicles Released from Malignant Human Testicular Germ Cells Increase MMP Production through Tumor-Stroma Interaction[END_REF]).

These properties make EMMPRIN a good target in cancer therapy. It has been shown that antibodies to EMMPRIN can decrease MMP expression leading to an inhibition of tumor cell invasion [START_REF] Bordador | Expression of EMMPRIN by Oral Squamous Cell Carcinoma[END_REF]J. Sun and Hemler 2001;[START_REF] Kanekura | Basigin (cd147) Is Expressed on Melanoma Cells and Induces Tumor Cell Invasion by Stimulating Production of Matrix Metalloproteinases by Fibroblasts[END_REF]. VEGF works as a major regulator of the angiogenic process in different circumstances, including tumor formation. EMMPRIN, in addition to increasing tumor invasion through MMP induction, it induces angiogenesis by the up-regulation VEGF expression (Y. Tang et al. 2005) as well as the stimulation of cell survival signaling, including Akt, Erk and FAK, through the increased production of the pericellular polysaccharide hyaluronan [START_REF] Toole | Hyaluronan, CD44 and Emmprin: Partners in Cancer Cell Chemoresistance[END_REF]. EMMPRIN regulates VEGF production in tumor and fibroblast cells via the PI3K-Akt pathway (Y. Tang et al. 2006).

HIF-1α and MCT

The increase of tumor size makes the tumor microenvironment suffering from hypoxia and induce the hypoxia inducible factor, HIF-1 α , a transcription factor which has been shown to induce MCT-4 gene expression in cells [START_REF] Moeller | Cytosolic Action of Thyroid Hormone Leads to Induction of Hypoxia-Inducible Factor-1α and Glycolytic Genes[END_REF][START_REF] Moeller | Thyroid Hormone Mediated Changes in Gene Expression Can Be Initiated by Cytosolic Action of the Thyroid Hormone Receptor ? Through the Phosphatidylinositol 3-Kinase Pathway[END_REF]. Up-regulation of MCTs in tumor cells is necessary for tumor survival and increase lactic acid concentration in the tumoral extracelluar microenvironment. This excess lactic acid inhibits peritumoral cytotoxic T cell function, and permitting continued uncontroled growth of the tumor [START_REF] Fischer | Inhibitory Effect of Tumor Cell-derived Lactic Acid on Human T Cells[END_REF]). MCT up-regulation is coordinated with EMMPRIN up-regulation which induces MMP production by peritumoral fibroblasts resulting in the extracellular matrix degradation and a favorable environment for tumor metastasis.

Rheumatoid arthritis

In rheumatoid arthritis (RA), Cyclophilin A (Cyp-A) up-regulates the expression of MMP-9 via the EMMPRIN signaling pathway through direct binding to EMMPRIN (Y. [START_REF] Yang | Cyclophilin A up-Regulates MMP-9 Expression and Adhesion of Monocytes/macrophages via CD147 Signalling Pathway in Rheumatoid Arthritis[END_REF]. And recently, it was found that EMMPRIN induces up-regulation of HIF-1α and VEGF in RA fibroblast-like synoviocytes, which promotes angiogenesis, and leads to the persistence of synovitis (C. [START_REF] Wang | CD147 Induces Angiogenesis through a Vascular Endothelial Growth Factor and Hypoxia-Inducible Transcription Factor 1αmediated Pathway in Rheumatoid Arthritis[END_REF].

Ischemic disease

The oxygen level decreases in the heart during myocardial infarction and in the brain during stroke. Because of hypoxia and ischemia cells become dependent upon glycolysis for energy metabolism, for continued cell viability the EMMPRIN associated lactate transporters MCT-1 and MCT-4 will be necessary [START_REF] Kirk | CD147 Is Tightly Associated with Lactate Transporters MCT1 and MCT4 and Facilitates Their Cell Surface Expression[END_REF]. High levels of MCT and EMMPRIN expression are detected under ischemic conditions in cardiac and neuronal cells (F. Zhang et al. 2005;[START_REF] Han | MCT-4, A511/basigin and EF5 Expression Patterns during Early Chick Cardiomyogenesis Indicate Cardiac Cell Differentiation Occurs in a Hypoxic Environment[END_REF], and it has been reported that EMMPRIN/Cyclofilin A association protects neurons from ischemia and hypoxia [START_REF] Boulos | Evidence That Intracellular Cyclophilin A and Cyclophilin A/CD147 Receptor-Mediated ERK1/2 Signalling Can Protect Neurons against in Vitro Oxidative and Ischemic Injury[END_REF]).

Graft-versus-host disease

Using monoclonal antibody to EMMPRIN as a treatment for patients exhibiting acute graftversus-host disease, shows promising efficacy, this effect due to suppression of leukocyte activation [START_REF] Deeg | Treatment of Steroid-Refractory Acute Graft-versus-Host Disease with Anti-CD147 Monoclonal Antibody ABX-CBL[END_REF]

Other diseases

Role of EMMPRIN is reported in other processes like atherosclerosis (L. [START_REF] Liang | Characterization of the Promoter of Human Extracellular Matrix Metalloproteinase Inducer (EMMPRIN)[END_REF], heart failure (Y. Y. [START_REF] Li | Interplay of Matrix Metalloproteinases, Tissue Inhibitors of Metalloproteinases and Their Regulators in Cardiac Matrix Remodeling[END_REF][START_REF] Spinale | A Matrix Metalloproteinase Induction/Activation System Exists in the Human Left Ventricular Myocardium and Is Upregulated in Heart Failure[END_REF], lung injury [START_REF] Foda | Ventilator-Induced Lung Injury Upregulates and Activates Gelatinases and EMMPRIN: Attenuation by the Synthetic Matrix Metalloproteinase Inhibitor, Prinomastat (AG3340)[END_REF], viral infection [START_REF] Pushkarsky | CD147 Facilitates HIV-1 Infection by Interacting with Virus-Associated Cyclophilin A[END_REF]), Alzheimer's disease [START_REF] Zhou | CD147 Is a Regulatory Subunit of the ?-Secretase Complex in Alzheimer's Disease Amyloid ?-Peptide Production[END_REF], chronic liver disease [START_REF] Shackel | Insights into the Pathobiology of Hepatitis C Virus-Associated Cirrhosis[END_REF] and in lymphocyte migration and activation [START_REF] Koch | T Cell Activation-Associated Epitopes of CD147 in Regulation of the T Cell Response, and Their Definition by Antibody Affinity and Antigen Density[END_REF][START_REF] Renno | A Role for CD147 in Thymic Development[END_REF]X. Zhang et al. 2002) .

EMMPRIN and tooth

In physiological processes

During tooth development, in cap stage, EMMPRIN expression was detected in the cell membranes of the inner enamel epithelium, stratum intermedium cells of the enamel organ and the dental papilla cells underlying the inner epithelium (Figure 18.a) [START_REF] Kumamoto | Immunohistochemical Detection of MT1-MMP, RECK, and EMMPRIN in Ameloblastic Tumors[END_REF][START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF][START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]S.-Y. Yang et al. 2012). In bell stage, it was detected in ameloblasts, stratum intermedium, and in odontoblasts (Figure 18.b) [START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF][START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]S.-Y. Yang et al. 2012). [START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF] EMMPRIN variability during tooth development was investigated, and it was found that EMMPRIN mRNA expression was higher in E13.0 mouse mandible than that in E11.0 (Figure 19.a). and was higher in P1 mouse tooth germ than that in E14.0 (Figure 19.b) [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]. [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF] At the root formation stage of tooth development, EMMPRIN was expressed strongly in the follicular cells overlaying the occlusal region of the rat molar germs. But, the expression was not region-specific and was weak in the follicular tissues in molar germs at the cap stage. So it was suggested that EMMPRIN play role in dental hard tissue maturation and the formation of an eruption pathway (S.-Y. [START_REF] Yang | Differential Expression of Cyclophilin A and EMMPRIN in Developing Molars of Rats[END_REF].

The differentiation-dependent co-expression of EMMPRIN with MMPs in the odontoblasts and enamel organ indicates that EMMPRIN plays role in proteolytic enzymes induction in the rat tooth germ [START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF]. And it was found that EMMPRIN colocalizes with caveolin-1 in cell membranes of ameloblasts and in inner enamel epithelial cells [START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF].

EMMPRIN functional role in tooth germ development was investigated, by an EMMPRIN siRNA interference approach. Significant increase in MT1-MMP mRNA expression and a reduction in MMP-2, MMP-3, MMP-9, MMP-13 and MT2-MMP mRNA expression were observed in the mouse mandibles following EMMPRIN abrogation. These results indicate that EMMPRIN could be involved in the early stage of tooth germ development and morphogenesis (Figure 20), possibly by regulating the MMP expression [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]. [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]

In pathological processes

Several reports have pointed to the relation between periodontitis and EMMPRIN (Dong et al. 2009;[START_REF] Xiang | Expression of Matrix Metalloproteinase-1, Matrix Metalloproteinase-2 and Extracellular Metalloproteinase Inducer in Human Periodontal Ligament Cells Stimulated with Interleukin-1beta[END_REF][START_REF] Liu | The Temporal Expression and Localization of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) during the Development of Perio-Dontitis in an Animal Model[END_REF][START_REF] Feldman | Porphyromonas Gingivalis-Mediated Shedding of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) by Oral Epithelial Cells: A Potential Role in Inflammatory Periodontal Disease[END_REF][START_REF] Yang | Temporal Expression of Metalloproteinase-8 and -13 and Their Relationships with Extracellular Matrix Metalloproteinase Inducer in the Development of Ligature-Induced Periodontitis in Rats[END_REF][START_REF] Wang | Expression of Extracellular Matrix Metalloproteinase Inducer Glycosylation and Caveolin-1 in Healthy and Inflamed Human Gingiva[END_REF].

Elevated levels of EMMPRIN have been related to the progression of periodontal disease [START_REF] Dong | Increased Expression of Extracellular Matrix Metalloproteinase Inducer Is Associated with Matrix Metalloproteinase-1 and -2 in Gingival Tissues from Patients with Periodontitis[END_REF]). EMMPRIN expression level increased from day 3 to day 7 and then gradually decreased from day 11 to day 21 (L. [START_REF] Liu | The Temporal Expression and Localization of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) during the Development of Perio-Dontitis in an Animal Model[END_REF][START_REF] Yang | Temporal Expression of Metalloproteinase-8 and -13 and Their Relationships with Extracellular Matrix Metalloproteinase Inducer in the Development of Ligature-Induced Periodontitis in Rats[END_REF].

During periodontitis development EMMPRIN was detected in the interdental gingiva, the gingival epithelium (Figure 21) and adjacent fibroblasts and in the inter-radicular bone. its inflammation-dependent expression was associated with collagen breakdown and alveolar bone loss (L. [START_REF] Liu | The Temporal Expression and Localization of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) during the Development of Perio-Dontitis in an Animal Model[END_REF]. On day 15, immunoreactivity was similar to that seen in the healthy state in the attached gingival epithelium (star in c1). Adapted from (L. [START_REF] Liu | The Temporal Expression and Localization of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) during the Development of Perio-Dontitis in an Animal Model[END_REF] EMMPRIN relation with other proteins during periodontitis was studied, it was found that EMMPRIN is associated with MMP-13 (higher expression level in day 3) but not with MMP-8 (higher MMP-8 expression in day 3) (D. [START_REF] Yang | Temporal Expression of Metalloproteinase-8 and -13 and Their Relationships with Extracellular Matrix Metalloproteinase Inducer in the Development of Ligature-Induced Periodontitis in Rats[END_REF], and it was found that the increased active MMP-1 and proMMP-1 production in the chronic human periodontitis may be associated with elevated HG-EMMPRIN levels (J. [START_REF] Wang | Expression of Extracellular Matrix Metalloproteinase Inducer Glycosylation and Caveolin-1 in Healthy and Inflamed Human Gingiva[END_REF].

Soluble forms of EMMPRIN were shown to be present in gingival crevicular fluid (GCF) of patients with different periodontal diseases for the first time by Emingil et al. These authors showed that elevated EMMPRIN levels in gingival crevicular fluid were related to the enhanced severity of periodontal inflammation, indicating that EMMPRIN may participate in the regulation of periodontal disease progression [START_REF] Emingil | Gingival Crevicular Fluid Matrix Metalloproteinase (MMP)-7, Extracellular MMP Inducer, and Tissue Inhibitor of MMP-1 Levels in Periodontal Disease[END_REF]).

High EMMPRIN level was detected in human ameloblastomas (L.-J. [START_REF] Jiang | Correlations of extrocellular matrix metalloproteinase inducer and microvessel density to invasiveness of ameloblastoma[END_REF][START_REF] Kumamoto | Immunohistochemical Detection of MT1-MMP, RECK, and EMMPRIN in Ameloblastic Tumors[END_REF][START_REF] Er | Neural Cell Adhesion Molecule and Neurothelin Expression in Human Ameloblastoma[END_REF], oral squamous cell carcinoma [START_REF] Bordador | Expression of EMMPRIN by Oral Squamous Cell Carcinoma[END_REF], and odontogenic cysts (L.-J. [START_REF] Jiang | Correlations of extrocellular matrix metalloproteinase inducer and microvessel density to invasiveness of ameloblastoma[END_REF][START_REF] Ali | Expression of Extracellular Matrix Metalloproteinase Inducer in Odontogenic Cysts[END_REF]). EMMPRIN expression was significantly higher in ameloblastomas than in odontogenic cysts, and microvessel density was positively associated with EMMPRIN expression to some extent (L.-J. [START_REF] Jiang | Correlations of extrocellular matrix metalloproteinase inducer and microvessel density to invasiveness of ameloblastoma[END_REF].

No significant difference in EMMPRIN expression was found among tumor types or subtypes [START_REF] Kumamoto | Immunohistochemical Detection of MT1-MMP, RECK, and EMMPRIN in Ameloblastic Tumors[END_REF]. EMMPRIN expression variability in various types of odontogenic cysts was studied and it was found that EMMPRIN expression was significantly higher in the epithelial lining of odontogenic keratocysts than in the dentigerous and periapical cysts [START_REF] Ali | Expression of Extracellular Matrix Metalloproteinase Inducer in Odontogenic Cysts[END_REF]. [START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF].

Supplementary data

Supplementary results

Basement membrane degradation -Transmission electron microscopy

Basement membrane degradation is delayed in the molar germs of EMMPRIN KO when compared to WT mice

Materials and methods

Mandibles of post-natal day 1 mice (3 litter-mate mice per group) were analyzed by conventional transmission electron microscopy (TEM). Heads were fixed in 2% (w/v) glutaraldehyde in 0.15 M cacodylate buffer, pH 7.4, overnight at 4°C. After post-fixation in 2% OsO4 for 1 h and dehydration in graded ethanol series at 4°C, the samples were embedded in Epon 812 (Fluka). Semi-thin sections were stained with toluidine blue and fuchsine. After washing the sections were dried and mounted in Eukitt. Ultrathin sections were stained with uranyl acetate and lead citrate and were examined with a JEOL 1011 electron microscope.

Results

To explore EMMPRIN role in mediating direct ameloblast-odontoblast interactions, we performed transmission electron microscopy analysis on the molar germs of new born mice.

TEM examination of M1 and M2 germs allowed the observation of the cells located at the tip of the cusps which corresponds to the higher differentiation stage (Figure 25). On M2 germs, the cell polarization observed in the WT (Figure 25 The Tb.N in -/-EMMPRIN mice were about the same that of +/+ mice (Figure 30).

Role of EMMPRIN in pulp-dentin regeneration

Background and project aim

EMMPRIN has been shown to be involved in the repair process of different injured tissues.

Indeed, the role of EMMPRIN in wound healing through MMP induction and increase in myofibroblast contractile activity has been established [START_REF] Gabison | Differential Expression of Extracellular Matrix Metalloproteinase Inducer (CD147) in Normal and Ulcerated Corneas[END_REF][START_REF] Huet | Extracellular Matrix Metalloproteinase inducer/CD147 Promotes Myofibroblast Differentiation by Inducing Α-Smooth Muscle Actin Expression and Collagen Gel Contraction: Implications in Tissue Remodeling[END_REF]. Therefore, the aim of this project was to investigate EMMPRIN role in the pulp dentin repair process by comparing the healing of injured pulps of EMMPRIN KO and WT mice.

Materials and methods

Twelve young adult mice (3 month-old) were used ( small cavity was prepared with a carbide bur (Dia 0,04mm) (Komet-France) on the acclusal aspect of the first upper left and right molars, in the centre of the tooth according to the mesio-distal plane until the pulp was visible through the transparency of the dentine floor of the cavity. A pulp exposure was mechanically done using an endodontic hand file of 0.15mm diameter with a 4% taper (C+file®, Dentsply-Maillefer France). Pulp capping was performed using Biodentine cement (septodont France) following the manufacturer's recommendations.

Using the tip of a probe, Biodentine was placed in contact with the pulp, and slightly condensed with a sterile paper point (XX-Fine, Henry Schein, France). Then, the cavity was sealed with glass ionomer cement (GIC). Animals were placed in individual cages until they recovered from anesthesia, and ibuprofen (0.06mg/g/day) was added in their drinking water for 72 hours. Treated animals were sacrificed at increasing time points following the clinical procedure, as follows:

-Six animals at 1 week post-operatively -Six animals at 4 weeks post-operatively Following removal of most of the soft tissues, heads of animals were immersed in 4% para-formaldehyde (PFA) (Sigma) overnight at 4°C. Before demineralization prior to histological analysis, samples were examined by micro-Ct at the same parameters previously reported (page 75, materials and methods.). Micro-Ct data were analyzed using the Osirix software and then Ct-analysis software.

Results

Micro-CT

In order to explore the tooth reparation, we performed Micro-CT on the maxilla of the treated WT and KO mice (Figure 32). Improved dentin repair is seen in KO when compared with WT both at Day 7 (P= 0.007 S) and day 28 (P= 0.157 NS) (Figure 33). This data must now be supported by histological analysis which are ongoing.

Discussion

Tooth development results from reciprocal inductive interactions between the mesenchyme and the oral epithelium and proceeds through a series of well-defined stages [START_REF] Ruch | Determinants of morphogénesis and cytodifferentiations of dental anloges in mice[END_REF][START_REF] Slavkin | Embryonic Tooth Formation. A Tool for Developmental Biology[END_REF][START_REF] Catón | Current Knowledge of Tooth Development: Patterning and Mineralization of the Murine Dentition[END_REF][START_REF] Miletich | Normal and Abnormal Dental Development[END_REF]I Thesleff and Hurmerinta 1981;[START_REF] Mitsiadis | Genetic Basis for Tooth Malformations: From Mice to Men and Back Again[END_REF]. Basement membrane degradation allowing a direct contact between pre-ameloblasts and preodontoblasts and their newly synthesized ECM appeared to be a crucial step of tooth development [START_REF] Meckel | Structure of Mature Human Dental Enamel as Observed by Electron Microscopy[END_REF][START_REF] Cevc | The Caries Resistance of Human Teeth Is Determined by the Spatial Arrangement of Hydroxyapatite Microcrystals in the Enamel[END_REF][START_REF] Zeichner-David | Control of Ameloblast Differentiation[END_REF]. EMMPRIN, a membrane glycoprotein also named CD147, has been shown to play an important role in the direct epithelial-mesenchymal interactions, as highlighted in the cancer field [START_REF] Toole | Emmprin (CD147), a Cell Surface Regulator of Matrix Metalloproteinase Production and Function[END_REF]. The expression of EMMPRIN in the developing tooth germs has been previously described [START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF][START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF], increasing in the forming tooth germ from E14 to P1 [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]. In this thesis, we confirmed that EMMPRIN was first expressed by pre-ameloblats and by the stratum intermedium at the early bell stage. At the late bell stage, EMMRIN labeling decreased on ameloblasts actively secreting enamel proteins, whereas it strongly increased on odontoblasts. Finally, this labeling disappeared in postsecretory ameloblasts whose function is to mature the enamel matrix.

However, at the beginning of this thesis, the in vivo role of EMMPRIN in tooth development and homeostasis was still unknown. By investigating mice KO for EMMPRIN, we showed that EMMPRIN, through the induction of several MMPs, may orchestrate the epithelial-mesenchymal cross-talk necessary for tooth formation, by enabling cleavage of the basement membrane and thus direct cell-cell interactions. Indeed in our mice we showed a delay in basement membrane degradation in KO mice when compared with WT. As a result, we observed a delay in ameloblast differentiation, especially detectable on transmission electron microscopy images (see Figure 25). As a consequence, MMP-3 and MMP-20 expression and activity were decreased and resulted in adults in decreased enamel volume and subtle abnormalities at the DEJ in both molars and incisors. It is noteworthy that we reported for the first time that EMMPRIN regulated the expression of MMP-20. As mice KO for MMP-20 display early enamel shedding and severe tooth alterations, our data suggest however that the quantity of MMP-20 expressed in the absence of EMMPRIN is sufficient to allow correct enamel maturation. Therefore, enamel volume was decreased in EMMPRIN KO mice but the maturation was rather-normal as indicated by nano-indentation experiments.

Surprisingly, in the tooth, EMMPRIN appeared to have no effect on MMP-2 and MMP-9 expression and activity. In several other processed such as corneal wound healing [START_REF] Gabison | Direct Epithelial-stromal Interaction in Corneal Wound Healing: Role of EMMPRIN/CD147 in MMPs Induction and beyond[END_REF], the absence of EMMPRIN was shown to alter gelatinase expression and activity.

Our results therefore suggest that the action of EMMPRIN is organ-dependent.

Previous observations using Si-RNA experiments on mandibles in culture have indicated that EMMPRIN was involved in tooth morphogenesis [START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]. In our study, we showed that tooth phenotype was rather normal in EMMPRIN KO mice, which is not consistent with these previous ex vivo observations. We therefore propose that the direct effect of EMMPRIN on the epithelial-stromal interaction may be limited since it is only allowed between basement membrane degradation allowing direct cell contact and before calcified matrix deposition which constitutes cell barriers, hence limiting EMMPRIN's action (Figure 34). EMMPRIN has been shown to be involved in the repair process of different injured tissues through MMP induction and increase in myofibroblast contractile activity [START_REF] Gabison | Differential Expression of Extracellular Matrix Metalloproteinase Inducer (CD147) in Normal and Ulcerated Corneas[END_REF][START_REF] Huet | Extracellular Matrix Metalloproteinase inducer/CD147 Promotes Myofibroblast Differentiation by Inducing Α-Smooth Muscle Actin Expression and Collagen Gel Contraction: Implications in Tissue Remodeling[END_REF]. We investigate for a potential role of EMMPRIN in the pulp dentin repair process by comparing the healing of injured pulps of EMMPRIN KO and WT mice. The repair process seems to be improved in KO mice but these preliminary data must be repeated and supported by histological analysis.

MMPs have been suggested to contribute to dentin caries progression and the hypothesis that MMP inhibition would affect dentin caries progression is clinically interesting. This hypothesis was sustained by in vivo studies in rat caries models where dentin caries progression was delayed by intra-oral administration of chemical MMP inhibitors, modified tetracylines and zoledronate [START_REF] Sulkala | The Effects of MMP Inhibitors on Human Salivary MMP Activity and Caries Progression in Rats[END_REF][START_REF] Tjäderhane | The Effect of MMP Inhibitor Metastat on Fissure Caries Progression in Rats[END_REF]). The MMP-inhibitory effects of Grape-seed extracts (GSE) suggest that these natural substances could be effective in inhibiting dentin caries progression. We therefore evaluated the capacity of these natural agents incorporated in a mouthrinse to prevent the degradation of demineralized dentin matrix by MMP-3. In this study, we selected MMP-3 because we have previously shown that this enzyme was the only MMP among those tested (MMP-2, MMP-3 and MMP-9) that was able to degrade several NCPs (Boukpessi et al., 2008), known to be associated to the collagen fibers in the dentin (Orsini et al., 2006). The removal of these NCPs can then permit further matrix degradation by exposing the collagen fibers to more collagen-specific MMPs such as collagenases and gelatinases (Malla et al., 2008) which are also present in the dentin organic matrix and in the saliva (Tjaderhane et al., 1998).

Our results show that dentin pretreatment with the tested mouthrinse, and with its active principles, inhibited the release by MMP-3 of several NCPs, namely decorin, biglycan and DSP from the matrix and the disorganization along the dentinal tubules induced by MMP-3.

We therefore hypothesized that the inhibition of NCP cleavage by GSE may prevent further matrix degradation by protecting the collagen fibers from collagen-specific MMPs such as collagenases and gelatinases. Indeed, PGs were initially reported as the major substrates of MMP-3. However, the situation may be more complex since PGs are bound to several other proteins in the ECM (Qin et al., 2006), and once the degradation of the dentin ECM is initiated, it may be more susceptible to further degradation by other proteases. Interestingly, amine fluorides appear to have MMP inhibitory properties at a lesser degree than GSEs but at a higher level than NaF. This information is clinically relevant, fluorides being recognized as the most efficient tools for preventing dental caries. However, it requires further investigations to be confirmed.

As general conclusion, proteases and their regulator such as EMMPRIN appear to have a major role in the formation, pathologies and repair of the tooth. Therefore their understanding opens several therapeutic issues, especially for the prevention and the treatment of dentin caries.

Catherine

  Chaussain who offered her continuous advices and encouragement throughout the course of this thesis. I thank her for the systematic guidance and great effort she put into training me in the scientific field. I am very grateful to Prof. Samia Mourah, from Paris Diderot University and Prof. Maria Cristina Manzanares, from Barcelona University for being part of this PhD thesis committee and for accepting being the reviewers of this PhD thesis. I would like to thank Prof. Ariane Berdal, from Paris Diderot University, Dr. Suzanne Menashi from Paris Est Créteil University, Dr. Gael Rochefort from Paris Descartes University, and Dr. Eric Huet from Paris Est Créteil University for accepting to be members of this PhD thesis committee. I am grateful and honored by their participation. I would like to thank Dominique Le-Denmat, Dominique Septier, and Brigitte Baroukh; I learned a lot of things from your scientific and general experiences.

Figure 1 :

 1 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 2 :

 2 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 4 :

 4 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 5 :

 5 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 6 :

 6 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 7 :

 7 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 8 :

 8 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 9 :

 9 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 10 :

 10 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure

  Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

  Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 13 :

 13 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

  Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................Figure 2 : Adult mouse mandible (own data). ........................................................................ Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013) ........................................................................................................................................ Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013) .Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013) ...............................................................................................Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ. Central cells form the stellate reticulum. Adapted from (Antonio Nanci and Cate 2013) ...................Figure 7 : Early bell stage of tooth development (own data) ..................................................Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp. Adapted from (Vital et al. 2012) ........................................................................................................................................Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data) ............................................................................Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D) and perspectives of the rod-interrod relationship when rods are exposed longitudinally (C) or in cross section (D). Interrod enamel surrounds each rod. DEJ: Dentinoenamel junction; IR: interrod; R,rod. Adapted from (Antonio Nanci and Cate 2013) ..............................................Figure11: Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-midmaturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J. D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF] ........ Figure12: Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: post-secretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel. Adapted from[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]..............................................................................................................Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from (Chaussain et al. 2013) ......................................

Figure 14 :

 14 Figure 14: Basigin isoforms. Characteristic features of isoforms are mentioned within blanket. Carbohydrates are shown by light grey color. Adapted from (Takashi Muramatsu 2012) ........................................................................................................................................ 33 Figure 15: Scheme of EMMPRIN structure. EMMPRIN contains an extracellular domain composed of two Ig loops with three Asn-linked oligosaccharides and short single transmembrane domain (TM) and a cytoplasmic domain (Cyt). The first Ig domain is required for counter-receptor activity, involved in MMP induction. Adapted from (Gabison et al. 2009). ....................................................................................................................................... 34 Figure 16: Possible EMMPRIN-mediated interactions stimulating MMP production. (A) Homophilic cis interaction between EMMPRIN molecules within the plasma membrane of a tumor cell. (B) Homophilic trans interaction between EMMPRIN molecules on apposing tumor cells. (C) Heterophilic interactions between EMMPRIN on a tumor cell and a putative EMMPRIN receptor on a fibroblast. Adapted from (Toole 2003)........................................... 35 Figure 17 : Tumor-cell induced activation of adjacent fibroblasts by homophilic EMMPRIN signaling. Adapted from (Joghetaei et al. 2013) ...................................................................... 40 Figure 18 : Immunoreactivity (IR) for EMMPRIN. a Cells of the inner enamel epithelium (cap stage of the enamel organ) show intense EMMPRIN IR (Alexa-coupled). b Ameloblasts as well as odontoblasts (bell stage of the enamel organ) exhibit strong EMMPRIN IR. Note the IR in the borderline between ameloblasts and the stratum intermedium. Mesenchymal cells of the dental papilla are only weakly immunoreactive. Abbreviations: A ameloblast; DL dental lamina; EEE external enamel epithelium; IEE internal enamel epithelium; EO enamel organ; Od odontoblast; SI stratum intermedium; SR stellate reticulum. Adapted from (Schwab et al. 2007) ................................................................................................................ 43 Figure 19 : Transcription level of EMMPRIN in different stages of tooth development. a EMMPRIN mRNA was higher in E13.0 mandible than that in E11.0. b The expression of EMMPRIN mRNA was higher in P1 tooth germ than that in E14.0. Adapted from (Xie et al. 2010) ........................................................................................................................................ 44 Figure 20 : Examination the role of EMMRIN in early tooth germ development using EMMPRIN siRNA in the cultured mandible at E11.0. a After being cultured for 6 days, the tooth germ was found to have developed into the cap stage in mandibles cultured with scramble siRNA. b Dental epithelial bud was observed in the mandible treated with EMMPRIN siRNA after 6 days of culture. c A cap-like mature enamel organ was observed in the mandibles with scrambled siRNA supplement at 8-day culture. d EMMPRIN siRNAtreated mandible explants also showed a bud-like tooth germ at 8-day culture. EMMPRIN siRNA had a specific effect on the morphogenesis of tooth germ. DE dental epithelium, DM dental mesenchyme, DP dental papilla, EO enamel organ, OE oral epithelium, PEK primary enamel knot. Adapted from (Xie et al. 2010) ................................. 45 Figure 21 : Temporal expression and localization of EMMPRIN in the gingival epithelium during ligature-induced periodontitis in the first mandibular molar of rats. (A) On day 0 (health), the immunoreactivity was strong in the basal cells, with a decrease toward the upper layers in the attached gingival epithelium (star in a1). (B) On day 7, immunoreactivity was greatly enhanced in the attached gingiva (star in b1). (C) On day 15, immunoreactivity was

  ....................................................................................... 69 Figure 23 : KLK-4 expression in tooth germs of EMMPRIN KO mice when compared with WT. For mRNA expression, a 33 % increase is observed by qRT-PCR in KO mice. KLK-4 activity is hardly detectable by casein zymography (with 20 mM EDTA in the incubation buffer to inhibit MMP activity). No activity is seen for recombinant MMP-20. From (Khaddam et al. 2014).............................................................................................................. 70 Figure 24 : SEM observation of 3 month-old mouse mandible sections. At M1 level, no difference in the morphology of either the bone or the teeth is detected between WT and KO mice (A, B). Both dentin (E, F) and enamel appear normal and the enamel prisms are normally constituted (C, D). From (Khaddam et al. 2014). .................................................... 71 Figure

Figure 26 :Figure 32 :

 2632 Figure 32: Mouse first upper molar after 7 and 28 days of capping with Biodentine. 7 days post operatively, dentin formation was detected in +/+ and -/-EMMPRIN mice (A,C), but it was more in -/-(brown arrow C) than in +/+ (brown arrow A). 28 days post operatively, dentine bridge was visible, but it was more continuous in -/-(arrow in D) than in +/+ (arrow in B) where it was not continued. e: enamel; d: dentin; GIC: glass ionomer cement; red *: Biodentine. ...............................................................................................................................Figure 33: Percent of dentin volume in volume of interest VOI. Significant increase in dentin density was detected in -/-EMMPRIN mice when compared with +/+ mice at 7 days post operatively................................................................................................................................Figure 34: Recapitulative schema proposing the role of EMMPRIN in tooth formation. At early bell stage, EMMPRIN is expressed by pre-ameloblast (p-Am) and may orchestrate basement membrane degradation (black line) to allow direct contact with pre-odontoblast (p-Od), which is mandatory for the final cell differentiation. At secretory stage, both secreting ameloblasts (s-Am) and odontoblasts (Od) highly express EMMPRIN. This expression may enhance MMP-20 synthesis by ameloblasts allowing for early enamel maturation. At the enamel maturation stage, post-secretory ameloblasts (pos-Am) lose their EMMPRIN expression. The arrows indicate EMMPRIN expression by cells. The red line schematizes the time window where a direct effect of EMMPRIN is allowed by a direct cell contact. D: dentin; pD: predentin; pm-E: premature enamel; E: enamel. ..................................................

Figure 33 :

 33 Figure 32: Mouse first upper molar after 7 and 28 days of capping with Biodentine. 7 days post operatively, dentin formation was detected in +/+ and -/-EMMPRIN mice (A,C), but it was more in -/-(brown arrow C) than in +/+ (brown arrow A). 28 days post operatively, dentine bridge was visible, but it was more continuous in -/-(arrow in D) than in +/+ (arrow in B) where it was not continued. e: enamel; d: dentin; GIC: glass ionomer cement; red *: Biodentine. ...............................................................................................................................Figure 33: Percent of dentin volume in volume of interest VOI. Significant increase in dentin density was detected in -/-EMMPRIN mice when compared with +/+ mice at 7 days post operatively................................................................................................................................Figure 34: Recapitulative schema proposing the role of EMMPRIN in tooth formation. At early bell stage, EMMPRIN is expressed by pre-ameloblast (p-Am) and may orchestrate basement membrane degradation (black line) to allow direct contact with pre-odontoblast (p-Od), which is mandatory for the final cell differentiation. At secretory stage, both secreting ameloblasts (s-Am) and odontoblasts (Od) highly express EMMPRIN. This expression may enhance MMP-20 synthesis by ameloblasts allowing for early enamel maturation. At the enamel maturation stage, post-secretory ameloblasts (pos-Am) lose their EMMPRIN expression. The arrows indicate EMMPRIN expression by cells. The red line schematizes the time window where a direct effect of EMMPRIN is allowed by a direct cell contact. D: dentin; pD: predentin; pm-E: premature enamel; E: enamel. ..................................................

Figure 1 :

 1 Figure 1 : The tooth and its supporting structure. Adapted from (Antonio Nanci and Cate 2013)

Figure 2 :

 2 Figure 2 : Adult mouse mandible (own data).

Figure 3 :

 3 Figure 3 : Dental lamina of tooth development. Adapted from (Antonio Nanci and Cate 2013)

Figure 4 :

 4 Figure 4 : Bud stage of tooth development. Adapted from (Antonio Nanci and Cate 2013)

Figure 5 :

 5 Figure 5 : Cap stage tooth germ showing the position of the enamel knot. Adapted from (Antonio Nanci and Cate 2013)

Figure 6 :

 6 Figure 6 : Cap stage, beginning of cellular differentiation within the enamel organ.Central cells form the stellate reticulum. Adapted from[START_REF] Nanci | Ten Cate's Oral Histology Development, Structure, and Function[END_REF]

Figure 7 :

 7 Figure 7 : Early bell stage of tooth development (own data)

  Perlecan (HSPG2) is a major heparan sulfate proteoglycan in BMs. Its expression in developing teeth, was detected in BMs, intercellular spaces of the enamel organ, and the dental papilla including odontoblasts[START_REF] Ida-Yonemochi | Perlecan, a Basement Membrane-Type Heparan Sulfate Proteoglycan, in the Enamel Organ: Its Intraepithelial Localization in the Stellate Reticulum[END_REF]. Overexpression of perlecan in transgenic mice results in abnormal tooth morphology and deregulation of growth factors such as TGF-b1 and bFGF[START_REF] Ida-Yonemochi | Morphogenetic Roles of Perlecan in the Tooth Enamel Organ: An Analysis of Overexpression Using Transgenic Mice[END_REF]).

Figure 8 :

 8 Figure 8 : Characteristics of dentin formation. Odontoblasts secrete an ECM composed of type I collagen and NCPs. Within the predentin type I collagen molecules are assembled as fibrils. Mineralization occurs at the mineralization front by growth and fusion of calcospherites formed by hydroxyapatite (HAP) crystals. This mineralization process is controlled by NCPs and by mineral ion availability. Cell processes remain entrapped within dentin whereas cell bodies remain at the periphery of the pulp.

Figure 9 :

 9 Figure 9 : Human dentin by scanning electronic microscopy (SEM). A. cutting line is parallel to dentin tubules, B. cutting line is perpendicular to dentin tubules. PtD: peritubular dentin, ItD: intertubular dentin. (Own data)

Figure 10 :

 10 Figure 10 : Scanning electron microscope views of (A) the enamel layer covering coronal dentin, (B) the complex distribution of enamel rods across the layer, (C and D)

Figure 11 :

 11 Figure 11 : Semi-thin (0.5 µm) sections from glutaraldehyde-fixed, decalcified, and plastic embedded mandibular incisors of wild-type mice stained with toluidine blue to illustrate the appearance of enamel and enamel organ cells at mid-secretory stage (A) and near-mid-maturation stage (B) of enamel development. Abbreviations: E, enamel; Am, ameloblast; Si, stratum intermedium; pd, predentin; D, dentin; ae, apical end; be, basal end; bv, blood vessel; as, artifact space; b, bone; c, cementum. Adapted from (J.D.[START_REF] Bartlett | Modulation of Cell-Cell Junctional Complexes by Matrix Metalloproteinases[END_REF]

Figure 12 :

 12 Figure 12 : Schema present incisor enamel and denin formation. p-Am: pre-ameloblast; pOd: pre-odontoblast; s-Am: secreting Ameloblasts; od: odontoblasts; pos-Am: postsecretory ameloblasts; pD: predentin; D: dentin; pm-E: premature enamel; E: enamel.

Figure 13 :

 13 Figure 13 : Schematic representation of MMP activity during the dentin carious process. Cariogenic bacteria present in the caries cavity release acids such as lactic acid that reduce the local pH. The resulting acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva (which bathes the caries cavity). Once the local pH is neutralized by salivary buffer systems, activated MMPs degrade the demineralized dentin matrix. Adapted from(Chaussain et al. 2013)

Figure 14 :

 14 Figure 14: Basigin isoforms. Characteristic features of isoforms are mentioned within blanket. Carbohydrates are shown by light grey color. Adapted from (Takashi Muramatsu 2012)

Figure 15 :

 15 Figure 15: Scheme of EMMPRIN structure. EMMPRIN contains an extracellular domain composed of two Ig loops with three Asn-linked oligosaccharides and short single transmembrane domain (TM) and a cytoplasmic domain (Cyt). The first Ig domain is required for counter-receptor activity, involved in MMP induction. Adapted from[START_REF] Gabison | Direct Epithelial-stromal Interaction in Corneal Wound Healing: Role of EMMPRIN/CD147 in MMPs Induction and beyond[END_REF]).

-

  Heterophilic interactions between EMMPRIN molecule on a tumor cell and a putativeEMMPRIN receptor on a fibroblast.

Figure 16 :(

 16 Figure 16: Possible EMMPRIN-mediated interactions stimulating MMP production. (A) Homophilic cis interaction between EMMPRIN molecules within the plasma membrane of a tumor cell. (B) Homophilic trans interaction between EMMPRIN molecules on apposing tumor cells. (C) Heterophilic interactions between EMMPRIN

Figure 17 :

 17 Figure 17 : Tumor-cell induced activation of adjacent fibroblasts by homophilic EMMPRIN signaling. Adapted from[START_REF] Joghetaei | The Extracellular Matrix Metalloproteinase Inducer (EMMPRIN, CD147) -a Potential Novel Target in Atherothrombosis Prevention?[END_REF]

Figure 18 :

 18 Figure 18 : Immunoreactivity (IR) for EMMPRIN. a Cells of the inner enamel epithelium (cap stage of the enamel organ) show intense EMMPRIN IR (Alexacoupled). b Ameloblasts as well as odontoblasts (bell stage of the enamel organ) exhibit strong EMMPRIN IR. Note the IR in the borderline between ameloblasts and the stratum intermedium. Mesenchymal cells of the dental papilla are only weakly immunoreactive. Abbreviations: A ameloblast; DL dental lamina; EEE external enamel epithelium; IEE internal enamel epithelium; EO enamel organ; Od odontoblast; SI stratum intermedium; SR stellate reticulum. Adapted from[START_REF] Schwab | Immunocytochemical and Biochemical Detection of EMMPRIN in the Rat Tooth Germ: Differentiation-Dependent Co-Expression with MMPs and Co-Localization with Caveolin-1 in Membrane Rafts of Dental Epithelial Cells[END_REF]

Figure 19 :

 19 Figure 19 : Transcription level of EMMPRIN in different stages of tooth development. a EMMPRIN mRNA was higher in E13.0 mandible than that in E11.0. b The expression of EMMPRIN mRNA was higher in P1 tooth germ than that in E14.0. Adapted from

Figure 20 :

 20 Figure 20 : Examination the role of EMMRIN in early tooth germ development using EMMPRIN siRNA in the cultured mandible at E11.0. a After being cultured for 6 days, the tooth germ was found to have developed into the cap stage in mandibles cultured with scramble siRNA. b Dental epithelial bud was observed in the mandible treated with EMMPRIN siRNA after 6 days of culture. c A cap-like mature enamel organ was observed in the mandibles with scrambled siRNA supplement at 8-day culture. d EMMPRIN siRNAtreated mandible explants also showed a bud-like tooth germ at 8day culture. EMMPRIN siRNA had a specific effect on the morphogenesis of tooth germ. DE dental epithelium, DM dental mesenchyme, DP dental papilla, EO enamel organ, OE oral epithelium, PEK primary enamel knot. Adapted from[START_REF] Xie | EMMPRIN (basigin/CD147) Is Involved in the Morphogenesis of Tooth Germ in Mouse Molars[END_REF]

Figure 21 :

 21 Figure 21 : Temporal expression and localization of EMMPRIN in the gingival epithelium during ligature-induced periodontitis in the first mandibular molar of rats. (A) On day 0 (health), the immunoreactivity was strong in the basal cells, with a decrease toward the upper layers in the attached gingival epithelium (star in a1). (B) On day 7, immunoreactivity was greatly enhanced in the attached gingiva (star in b1). (C)

Figure 22 :Figure 24 :

 2224 Figure 22 : EMMPRIN expression in the developing incisor of 3 month-old mice Immunostaining with EMMPRIN antibody on sagittal section of the mandible shows that the secretory ameloblasts, the stratum intermedium and odontoblasts are positive for EMMPRIN (A and B). By contrast, no staining is observed in the post-secretory ameloblast (C). Am: ameloblast; s-Am: secretory ameloblast; pos-Am: post-secretory ameloblast; Od: odontoblast; D: dentin; pD: predentin; pm-E: premature enamel; Si:stratum intermedium; fm: forming matrix. From[START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]

  .A) was not visible in the KO in either the ameloblasts and the odontoblast layer (Figure 25.B). The basement membrane, which separates the pre-ameloblast from the pre-odontoblast compartments, was already partially degraded in the WT allowing for direct cell interactions between the two cellular compartments (Figure 25.C), whereas it was still continuous in the KO (Figure 25.D), suggesting that the differentiation process was delayed in EMMPRIN KO germs. However at a later stage of the development (M1 germ), cells were fully polarized with a palisade organization in both mice (Figure 25.E, F). The basement membrane at the tip of the cusp was no longer detectable in either mice model (Figure 25.G,H). Dentin matrix was actively secreted and mineralized although at a more advanced stage in the WT and mineralizing enamel was already detectable (Figure 25.G).

Figure 25 :

 25 Figure 25: TEM analysis was performed on M1 and M2 germs of new born mice. In the KO M2 germs, a cell polarization delay is observed in both pre-ameloblasts and preodontoblasts localized at the tip of the cusps (b). In the WT, well-organized ameloblast and odontoblast palisades are seen, with a basal localization of the nuclei and long cell processes (arrow-heads) (a), whereas in the KO, cells are seen proliferating with centrally localized nucleus (b). At higher magnification, the basement membrane (black arrows) is partially degraded in WT (white arrows) (c), but appears still intact in the KO (d). In M1 germ, the basement membrane which can no longer be detected in the WT (e) is partially degraded in the KO (arrow) (f). Dentin matrix (black arrow-heads) is secreted in both mice models (e-f-g-h) but at a higher rate in the WT (e) where a greater amount of fibrillated collagen is seen associated with hydroxyapatite crystals (white arrow heads). In addition, mineralizing enamel matrix can already be observed at the secreting pole of WT ameloblasts localized at the tip of the cusp (g) but is not detectable in the KO (h). pam: pre-ameloblast; pod: pre-odontoblast; am: ameloblast; od: odontoblast; fde: forming dentin; fen: forming enamel. (Own data).

Figure

  Figure 27: Alveolar bone density.

Figure 28 :

 28 Figure 28: Percent of bone volume in VOI.

Figure 29 :

 29 Figure 29: Trabecular bone thickness in VOI.

Figure 30 :

 30 Figure 30: Trabecular number in VOI.

Figure 32 :

 32 Figure 32: Mouse first upper molar after 7 and 28 days of capping with Biodentine. 7 days post operatively, dentin formation was detected in +/+ and -/-EMMPRIN mice (A,C), but it was more in -/-(brown arrow C) than in +/+ (brown arrow A). 28 days post operatively, dentine bridge was visible, but it was more continuous in -/-(arrow in D) than in +/+ (arrow in B) where it was not continued. e: enamel; d: dentin; GIC: glass ionomer cement; red *: Biodentine.

Figure 33 :

 33 Figure 33: Percent of dentin volume in volume of interest VOI. Significant increase in dentin density was detected in -/-EMMPRIN mice when compared with +/+ mice at 7 days post operatively.

Figure 34 :

 34 Figure 34: Recapitulative schema proposing the role of EMMPRIN in tooth formation. At early bell stage, EMMPRIN is expressed by pre-ameloblast (p-Am) and may orchestrate basement membrane degradation (black line) to allow direct contact with pre-odontoblast (p-Od), which is mandatory for the final cell differentiation. At secretory stage, both secreting ameloblasts (s-Am) and odontoblasts (Od) highly express EMMPRIN. This expression may enhance MMP-20 synthesis by ameloblasts allowing for early enamel maturation. At the enamel maturation stage, post-secretory ameloblasts (pos-Am) lose their EMMPRIN expression. The arrows indicate EMMPRIN expression by cells. The red line schematizes the time window where a direct effect of EMMPRIN is allowed by a direct cell contact. D: dentin; pD: predentin; pm-E: premature enamel; E: enamel.

Table 1 : Percentage Wet Weight Composition of Rat Incisor Enamel. From (Antonio

 1

	Nanci and Cate 2013)

MOTS CLÉS: FORMATION DE LA DENT, MMPS, INTERACTION CELLULAIRE, PROTÉINES DE L'ÉMAIL.

Acknowledgment:

Results

Role of EMMPRIN in tooth formation

 [START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF]Supplementary Table 1 : PCR gene primers and reference. From [START_REF] Khaddam | EMMPRIN/CD147 Deficiency Disturbs Ameloblast-Odontoblast Cross-Talk and Delays Enamel Mineralization[END_REF].

EMMPRIN expression in the molar germ of mouse embryo

Alveolar bone phenotype

Materials and methods

In order to explore the alveolar bone phenotype in EMMPRIN -/-mice, Half mandibles (n=3 age-matched mice per group) were subjected to a desktop micro-CT, (Skyscan 1172, Skyscan, Aartselaar, Belgium). The micro-CT settings were used as follows: 9 μm resolution, voltage 80 kV; current 100 μA; exposure time 400 ms; 180° rotation; rotation step 0.4 degree; frame averaging 4. The scanning time was approximately 4 hours/sample. A total of 1700 native slice frames per sample were reconstructed using NRecon software (Skyscan, Belgium). Tridimensional images were acquired with an isotropic voxel size of 9.92 μm. Full 3D high-resolution raw data are obtained by rotating both the X-ray source and the flat panel detector 360° around the sample.

Bone volume rendering was measured using the open-source OsiriX imaging software (v3.7.1, distributed under LGPL license, Dr A. Rosset, Geneva, Switzerland) from 2D images.

The microarchitecture of alveolar bone of left mandible was studied. The ventral limit of the volume of interest (VOI) was located at the first section containing the mesial root of the first left molar; the dorsal limit was located 100 sections after, at the level of the alveolar ridge and the buccal surface of the bone jaw (Figure 27). The VOI was designed by drawing interactively polygons on the 2D sections. Several polygons were needed to be drawn (e.g. on the first section, several at the middle, and on the final section) using the free hand tool with "CT analyzer" software (Skyscan, release 1.13.5.1, Kontich, Belgium). The interpolated VOI comprised only basal/alveolar bone. A simple global thresholding was determined interactively to eliminate background noise and to select bone.

The parameters analyzed were: Bone volume fraction BV/TV (%), trabecular thickness Tb.Th (mm), trabecular number Tb.N (1/mm), and trabecular separation Tb.Sp (mm).

Numerical variables were expressed as mean ± standard deviation.

 The separation between bone trabeculae (Tb.Sp) in the VOI.

The Tb.Sp in the -/-EMMPRIN mice were about the same that of +/+ (Figure 31).

Inhibition of MMP-3 and dentin matrix degradation

Tang, Yi, Prabakaran Kesavan, Marian T. Nakada, and Li Yan. 2004

Abstract

Role of EMMPRIN and MMPs in tooth development, dental caries and pulp-dentin regeneration

Tooth development is regulated by a series of reciprocal inductive signalings between the dental epithelium and mesenchyme, which culminates with the formation of dentin and enamel. EMMPRIN/CD147 is an Extracellular Matrix MetalloPRoteinase (MMP) INducer that mediates epithelial-mesenchymal interactions in cancer and other pathological processes and is expressed in developing teeth.

Here we used EMMPRIN knockout (KO) mice to determine the functional role of EMMPRIN on dental tissues formation. We demonstrated that EMMPRIN deficiency results in decreased in MMP-3 and MMP-20 expressions, delayed in basement membrane degradation in tooth germ, delayed in enamel formation well distinguishable in incisor, and in decreased enamel volume and thickness but normal maturation. These results indicate that EMMPRIN is involved in the epithelial-mesenchymal cross-talk during tooth development by regulating the expression of MMPs.

Then we tried to investigate the potential role of EMMPRIN in the pulp dentin repair process by comparing the healing of injured pulps of EMMPRIN KO and WT mice.

Finally, we evaluated the capacity of grape-seed extracts (known to be natural inhibitors of MMPs and used in new daily mouthrinse) to prevent the degradation of human demineralized dentin matrix by MMP-3.

KEY WORDS: TOOTH FORMATION, MMPS, CELL INTERACTION, ENAMEL PROTEINS

Résumé Rôle d'EMMPRIN et MMPS dans le développement dentaire, la carie dentaire et la régénération pulpo-dentinaire

Le développement dentaire est orchestré par une série de signalisations inductives réciproques entre l'épithélium dentaire et le mésenchyme, qui conduit à la formation de la dentine et de l'émail. EMMPRIN/CD147 est un INducteur des MetalloPRoteinases de la Matrice Extracellulaire (MMPs) qui régule les interactions épithéliomésenchymateuses dans le cancer et d'autres processus pathologiques et est exprimé lors du développement dentaire.

Ainsi, nous avons utilisé des souris KO pour EMMPRIN pour déterminer le rôle d'EMMPRIN dans la formation des tissus dentaires. Nous avons démontré que l'absence d'EMMPRIN conduisait dans le germe dentaire à une diminution de l'expression de MMP-3 et de MMP-20, à un retard de la dégradation de la membrane basale, à un retard de la formation de l'émail bien visible dans l'incisive à croissance continue, à une diminution du volume et de l'épaisseur d'émail, mais à une maturation amélaire normale. Ces résultats indiquent qu'EMMPRIN est impliqué dans le dialogue épithélio-mésenchymateuse pendant le développement dentaire, principalement par la régulation de l'expression de certaines MMPS.

Nous avons ensuite essayé d'évaluer le rôle potentiel d'EMMPRIN dans le processus de réparation dentaire en comparant la cicatrisation de blessures pulpaires des souris KO pour EMMPRIN à des souris WT.

Enfin, dans un souci de transfert vers la clinique, nous avons évalué la capacité d'extraits de pépin de raisin (connu pour être des inhibiteurs naturels de MMPs) à empêcher la dégradation de la matrice dentinaire humaine déminéralisée et traitée par MMP-3.

Abstract

Role of EMMPRIN and MMPs in tooth development, dental caries and pulp-dentin regeneration

Tooth development is regulated by a series of reciprocal inductive signalings between the dental epithelium and mesenchyme, which culminates with the formation of dentin and enamel. EMMPRIN/CD147 is an Extracellular Matrix MetalloPRoteinase (MMP) INducer that mediates epithelial-mesenchymal interactions in cancer and other pathological processes and is expressed in developing teeth.

Here we used EMMPRIN knockout (KO) mice to determine the functional role of EMMPRIN on dental tissues formation. We demonstrated that EMMPRIN deficiency results in decreased in MMP-3 and MMP-20 expressions, delayed in basement membrane degradation in tooth germ, delayed in enamel formation well distinguishable in incisor, and in decreased enamel volume and thickness but normal maturation. These results indicate that EMMPRIN is involved in the epithelial-mesenchymal cross-talk during tooth development by regulating the expression of MMPs.

Then we tried to investigate the potential role of EMMPRIN in the pulp dentin repair process by comparing the healing of injured pulps of EMMPRIN KO and WT mice.

Finally, we evaluated the capacity of grape-seed extracts (known to be natural inhibitors of MMPs and used in new daily mouthrinse) to prevent the degradation of human demineralized dentin matrix by MMP-3. Ainsi, nous avons utilisé des souris KO pour EMMPRIN pour déterminer le rôle d'EMMPRIN dans la formation des tissus dentaires. Nous avons démontré que l'absence d'EMMPRIN conduisait dans le germe dentaire à une diminution de l'expression de MMP-3 et de MMP-20, à un retard de la dégradation de la membrane basale, à un retard de la formation de l'émail bien visible dans l'incisive à croissance continue, à une diminution du volume et de l'épaisseur d'émail, mais à une maturation amélaire normale. Ces résultats indiquent qu'EMMPRIN est impliqué dans le dialogue épithélio-mésenchymateuse pendant le développement dentaire, principalement par la régulation de l'expression de certaines MMPS.

Nous avons ensuite essayé d'évaluer le rôle potentiel d'EMMPRIN dans le processus de réparation dentaire en comparant la cicatrisation de blessures pulpaires des souris KO pour EMMPRIN à des souris WT.

Enfin, dans un souci de transfert vers la clinique, nous avons évalué la capacité d'extraits de pépin de raisin (connu pour être des inhibiteurs naturels de MMPs) à empêcher la dégradation de la matrice dentinaire humaine déminéralisée et traitée par MMP-3.