Charlène Martin

Mathilde Bergamelli

Cécile E Malnou
email: cecile.malnou@univ-tlse3.fr

Gisela D'angelo
email: gisela.dangelo@curie.fr

Placental extracellular vesicles in maternal-fetal communication during pregnancy

published or not. The documents may come

Placental extracellular vesicles in maternal-fetal communication during pregnancy

Introduction

Extracellular vesicles (EVs) are membrane-bound vesicles released from virtually all cells into the extracellular space [START_REF] Van Niel | Shedding light on the cell biology of extracellular vesicles[END_REF]. EVs comprise vesicles that originate from the endosomal network (exosomes) or from the outward budding of the plasma membrane (microparticles, oncosomes, or microvesicles, collectively referred to as ectosomes). Due to lack of specificity of EV markers and overlap in size between these categories, they are currently classified on the basis of their physical characteristics into small EVs (sEVs; up to or around 100 nm, encompassing both exosomes and small ectosomes) and large EVs (lEVs; above 100 nm) [START_REF] Théry | Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines[END_REF].

Both EV subtypes carry a variety of proteins, lipids and genetic material that can be transferred to local and distant target cells and trigger a broad range of cellular activities and biological responses to modulate their fate and behavior [START_REF] Van Niel | Challenges and directions in studying cell-cell communication by extracellular vesicles[END_REF]. They are now increasingly viewed as important mediators of intercellular communication in numerous physiological and pathological processes, including development, immune responses, viral pathogenesis, pregnancy, and cancer progression [START_REF] Van Niel | Shedding light on the cell biology of extracellular vesicles[END_REF].

During pregnancy the placenta plays a pivotal role ensuring the transfer of nutrients and oxygen between mother and fetus. This is achieved by an intimate communication mediated by soluble factors but also by means of EVs [START_REF] Mitchell | Placental exosomes in normal and complicated pregnancy[END_REF][START_REF] Sarker | Placenta-derived exosomes continuously increase in maternal circulation over the first trimester of pregnancy[END_REF][START_REF] Tannetta | Syncytiotrophoblast extracellular vesicles -Circulating biopsies reflecting placental health[END_REF]. The different placental cell types (i.e., syncytiotrophoblasts, cytotrophoblasts, extravillous cytotrophoblasts) release a wide range of EVs (small and large) into maternal circulation and fetal compartments (amniotic fluid and fetal circulation), which gradually increase in concentration during pregnancy and stop after delivery [START_REF] Sarker | Placenta-derived exosomes continuously increase in maternal circulation over the first trimester of pregnancy[END_REF][START_REF] Sadovsky | Placental small extracellular vesicles: Current questions and investigative opportunities[END_REF][START_REF] Czernek | Exosomes as Messengers Between Mother and Fetus in Pregnancy[END_REF][START_REF] Miranda | Placental exosomes profile in maternal and fetal circulation in intrauterine growth restriction -Liquid biopsies to monitoring fetal growth[END_REF]. However, to avoid possible confusion and for simplification, we will use the general term trophoblastic EVs in this review article. Placental-derived EVs play key roles in regulating maternal-fetal communication in both normal and pathologic conditions including gestational diabetes mellitus (GDM) [START_REF] Salomon | Gestational Diabetes Mellitus Is Associated With Changes in the Concentration and Bioactivity of Placenta-Derived Exosomes in Maternal Circulation Across Gestation[END_REF], preeclampsia (PE) [START_REF] Tannetta | Update of syncytiotrophoblast derived extracellular vesicles in normal pregnancy and preeclampsia[END_REF], and during viral infections [START_REF] Delorme-Axford | Human placental trophoblasts confer viral resistance to recipient cells[END_REF] (Figure 1). The nature of this communication appears to be dependent on specific proteins and microRNAs (miRNAs) enclosed and conveyed by placental EVs (Table 1). Among others, placental EVs harbor the placental alkaline phosphatase (PLAP), an integral membrane protein (enzyme) unique to the placenta [START_REF] Sarker | Placenta-derived exosomes continuously increase in maternal circulation over the first trimester of pregnancy[END_REF]. They also contain proteins with immunological functions, such as human leukocyte antigen G (HLA-G), MHC class I chain-related protein A and B (MIC-A and -B), and syncytin-1, that respectively modulate maternal immune tolerance and reduce the secretion of proinflammatory cytokines to protect fetal tissue from maternal immune cell attack and prevent fetal rejection [START_REF] Kshirsagar | Immunomodulatory molecules are released from the first trimester and term placenta via exosomes[END_REF][START_REF] Holder | Immune cell activation by trophoblast-derived microvesicles is mediated by syncytin 1[END_REF][START_REF] Than | Galectins: guardians of eutherian pregnancy at the maternal-fetal interface[END_REF]. Placental EVs also contain functional placentaspecific miRNAs, including the C19MC cluster of miRNAs [START_REF] Luo | Human Villous Trophoblasts Express and Secrete Placenta-Specific MicroRNAs into Maternal Circulation via Exosomes1[END_REF][START_REF] Donker | The expression profile of C19MC microRNAs in primary human trophoblast cells and exosomes[END_REF] that confers viral resistance to recipient cells [START_REF] Delorme-Axford | Human placental trophoblasts confer viral resistance to recipient cells[END_REF]. However, in pathological pregnancies, the release of placental EVs was shown to be affected by the microenvironment to which cells are exposed. Studies have also demonstrated that changes in the microenvironment alter not only placental EV secretion, but also their associated cargos and their bioactivity.

In this review, we describe current knowledge and gaps regarding placental EVs and their roles in normal pregnancy and selected examples of gestational complications.

Placental EVs in physiological pregnancy

Placenta establishment

The success of human pregnancy highly depends on very early developmental processes, among which the placenta establishment is crucial. After implantation of the blastocyst into the endometrium, the outer layer of the embryo's trophectoderm begins to invade maternal endometrium and differentiates into syncytiotrophoblasts and cytotrophoblasts (villous and extravillous) [START_REF] Shahbazi | Deconstructing and reconstructing the mouse and human early embryo[END_REF]. These primitive structures will develop into a mature placenta allowing exchanges between maternal blood and embryo/fetal blood. The placenta itself evolves during pregnancy allowing an adaptive balance of the utero-placental-fetal circulation according to the age of pregnancy.

Trophoblastic EVs have been shown to contribute locally to maternal-embryo communication. Through their miRNA content, trophoblastic EVs modify the transcriptome of maternal endometrial cells, including pathways essential for placental invasion (extracellular matrix remodeling), thereby facilitating subsequent placental development [START_REF] Godakumara | Trophoblast derived extracellular vesicles specifically alter the transcriptome of endometrial cells and may constitute a critical component of embryo-maternal communication[END_REF][START_REF] Szuszkiewicz | Early steps of embryo implantation are regulated by exchange of extracellular vesicles between the embryo and the endometrium[END_REF]. Trophoblastic EVs also activate signaling pathways necessary for successful invasion of the extravillous trophoblast (including matrix metalloproteinases and mitogen-activated protein kinases) [START_REF] Salomon | Role of Exosomes in Placental Homeostasis and Pregnancy Disorders[END_REF]. Control of oxygen (O2) levels is also crucial for the efficiency of the implantation/invasion process in humans. Under conditions of reduced O2 levels (e.g., hypoxia), the bioactivity of trophoblastic EVs is altered, promoting increased proliferation and migration of extravillous cytotrophoblasts [START_REF] Salomon | Hypoxia-induced changes in the bioactivity of cytotrophoblast-derived exosomes[END_REF]. In addition to these local effects, placental EVs in the maternal circulation modulate endothelial cell migration and may contribute to the vascular adaptation of women to pregnancy state (including hypervolemia) [START_REF] Salomon | A gestational profile of placental exosomes in maternal plasma and their effects on endothelial cell migration[END_REF]. Placental EVs may also be involved in physiological pregnancies to limit adverse outcomes such as the pro-inflammatory environment caused by air pollution, therefore playing a major potential role is maintaining healthy fetal development [START_REF] Ferrari | Extracellular vesicles and their miRNA contents counterbalance the pro-inflammatory effect of air pollution during physiological pregnancy: A focus on Syncytin-1 positive vesicles[END_REF]. Immune tolerance Since the fetus and its placenta are considered as a semi-allogenic graft within the maternal host during a natural conception, complex interactions operate at the maternal-fetal interface to allow adaptation and tolerance of the maternal immune system [START_REF] Mor | The unique immunological and microbial aspects of pregnancy[END_REF][START_REF] Erlebacher | Immunology of the Maternal-Fetal Interface[END_REF][START_REF] Prabhudas | Immune mechanisms at the maternal-fetal interface: perspectives and challenges[END_REF]. Among the various mechanisms involved, many roles of placental EVs have been documented via their transfer to maternal immune cells [START_REF] Czernek | Exosomes as Messengers Between Mother and Fetus in Pregnancy[END_REF][START_REF] Tong | Immunological effects of placental extracellular vesicles[END_REF][START_REF] Morelli | Extracellular vesicles and immune response during pregnancy: A balancing act*[END_REF][START_REF] Bai | Placenta-Derived Exosomes as a Modulator in Maternal Immune Tolerance During Pregnancy[END_REF][START_REF] Nair | Extracellular vesicles and their immunomodulatory functions in pregnancy[END_REF][START_REF] Mincheva-Nilsson | Immunosuppressive Protein Signatures Carried by Syncytiotrophoblast-Derived Exosomes and Their Role in Human Pregnancy[END_REF][START_REF] Favaro | Immunomodulatory properties of extracellular vesicles in the dialogue between placental and immune cells[END_REF], at a local level or by disseminating in the maternal circulation towards systemic lymphoid cells. Placental EVs have been described to act mostly on Natural Killer (NK) cells [START_REF] Hedlund | Human Placenta Expresses and Secretes NKG2D Ligands via Exosomes that Down-Modulate the Cognate Receptor Expression: Evidence for Immunosuppressive Function[END_REF][START_REF] Gutierrez-Franco | Characterization of B7H6, an endogenous ligand for the NK cell activating receptor NKp30, reveals the identity of two different soluble isoforms during normal human pregnancy[END_REF][START_REF] Ishida | Maternal peripheral blood natural killer cells incorporate placenta-associated microRNAs during pregnancy[END_REF], monocytes, macrophages [START_REF] Atay | Human Trophoblast-Derived Exosomal Fibronectin Induces Pro-Inflammatory Il-1β Production by Macrophages[END_REF][START_REF] Atay | Trophoblast-Derived Exosomes Mediate Monocyte Recruitment and Differentiation[END_REF][START_REF] Bai | Human placental exosomes induce maternal systemic immune tolerance by reprogramming circulating monocytes[END_REF] and T cells [START_REF] Kovács | Unravelling the Role of Trophoblastic-Derived Extracellular Vesicles in Regulatory T Cell Differentiation[END_REF][START_REF] Lokossou | Endogenous retrovirus-encoded Syncytin-2 contributes to exosome-mediated immunosuppression of T cells †[END_REF][START_REF] Hedlund | Human Placenta Expresses and Secretes NKG2D Ligands via Exosomes that Down-Modulate the Cognate Receptor Expression: Evidence for Immunosuppressive Function[END_REF][START_REF] Stenqvist | Exosomes Secreted by Human Placenta Carry Functional Fas Ligand and TRAIL Molecules and Convey Apoptosis in Activated Immune Cells, Suggesting Exosome-Mediated Immune Privilege of the Fetus[END_REF][START_REF] Sabapatha | Specific Isolation of Placenta-Derived Exosomes from the Circulation of Pregnant Women and Their Immunoregulatory Consequences1[END_REF], notably via their internalization and the delivery of associated components.

They act mainly by promoting the suppression of maternal immune function at different levels. Hence, several ligands of the NKG2D activating receptor of NK cells are released by trophoblastic sEVs, including MIC-A and -B [START_REF] Mincheva-Nilsson | Placenta-Derived Soluble MHC Class I Chain-Related Molecules Down-Regulate NKG2D Receptor on Peripheral Blood Mononuclear Cells during Human Pregnancy: A Possible Novel Immune Escape Mechanism for Fetal Survival[END_REF] and ULBP1-5 [START_REF] Hedlund | Human Placenta Expresses and Secretes NKG2D Ligands via Exosomes that Down-Modulate the Cognate Receptor Expression: Evidence for Immunosuppressive Function[END_REF]. Interaction of NKG2D with sEVs harboring these ligands leads to its down regulation at the surface of NK cells, CD8 and gd T cells, inhibiting their cytotoxic activity in vitro [START_REF] Hedlund | Human Placenta Expresses and Secretes NKG2D Ligands via Exosomes that Down-Modulate the Cognate Receptor Expression: Evidence for Immunosuppressive Function[END_REF]. Similarly, another NK activating receptor, NKp30, is suspected to be inhibited by sEVs presenting B7H6, an endogenous ligand of NKp30, widely expressed by trophoblasts, which may act as a decoy substrate [START_REF] Gutierrez-Franco | Characterization of B7H6, an endogenous ligand for the NK cell activating receptor NKp30, reveals the identity of two different soluble isoforms during normal human pregnancy[END_REF]. Importantly, placental sEVs also carry the pro-apoptotic death messengers FasL (Fas ligand) and TRAIL at their surface, inducing apoptosis of T cells and peripheral blood mononuclear cells (PBMCs) in vitro [START_REF] Stenqvist | Exosomes Secreted by Human Placenta Carry Functional Fas Ligand and TRAIL Molecules and Convey Apoptosis in Activated Immune Cells, Suggesting Exosome-Mediated Immune Privilege of the Fetus[END_REF], as well as the immunomodulatory molecule PD-L1, responsible for down regulating the signaling CD3-z molecule at the cell surface, inhibiting T cell activation [START_REF] Sabapatha | Specific Isolation of Placenta-Derived Exosomes from the Circulation of Pregnant Women and Their Immunoregulatory Consequences1[END_REF]. Two other trophoblastic proteins carried by placental sEVs exert immunomodulatory functions on T cells: Syncitin-2, by decreasing the secretion of Th1 cytokines, by activating PBMCs [START_REF] Lokossou | Endogenous retrovirus-encoded Syncytin-2 contributes to exosome-mediated immunosuppression of T cells †[END_REF] and HSPE1, and by promoting the expansion and differentiation of T reg in vitro [START_REF] Kovács | Unravelling the Role of Trophoblastic-Derived Extracellular Vesicles in Regulatory T Cell Differentiation[END_REF]. Finally, circulating monocytes are also down modulated by trophoblastic sEVs, notably via the action of miR-29a-3p, promoting the expression of PD-L1 on their surface, which will further favor systemic immune tolerance [START_REF] Bai | Human placental exosomes induce maternal systemic immune tolerance by reprogramming circulating monocytes[END_REF].

In addition to promoting maternal immune tolerance, EVs play an important role in providing a mild inflammatory environment conducive to tissue remodeling and embryo implantation [START_REF] Mor | Inflammation and pregnancy: the role of the immune system at the implantation site[END_REF][START_REF] Morelli | Extracellular vesicles and immune response during pregnancy: A balancing act*[END_REF]. In these pro-inflammatory events, placental EVs also act at different levels, as a chemoattractant for monocytes in vitro [START_REF] Atay | Trophoblast-Derived Exosomes Mediate Monocyte Recruitment and Differentiation[END_REF], inducing their production of pro-inflammatory cytokines [START_REF] Atay | Trophoblast-Derived Exosomes Mediate Monocyte Recruitment and Differentiation[END_REF][START_REF] Atay | Human Trophoblast-Derived Exosomal Fibronectin Induces Pro-Inflammatory Il-1β Production by Macrophages[END_REF], and also promoting the secretion of decidual cell of immune modulators via TNFα [START_REF] Taylor | Cytotrophoblast extracellular vesicles enhance decidual cell secretion of immune modulators via TNFα[END_REF]. In addition, when incubated with monocytes and B cells, placental lEVs induce TNFα, MIP-1α, IL-1α, IL-1β, IL-6, IL-8 cytokines release [START_REF] Southcombe | The immunomodulatory role of syncytiotrophoblast microvesicles[END_REF]. Finally, placental lEVs have also been shown to activate neutrophils by triggering the generation of extracellular traps in the intervillous space [START_REF] Gupta | Induction of Neutrophil Extracellular DNA Lattices by Placental Microparticles and IL-8 and Their Presence in Preeclampsia[END_REF].

Antiviral role

The remodeling of the immune system at the maternal-fetal interface could favor the development of viral and bacterial infections during this period of immunomodulation.

However, several mechanisms limit fetal rejection while simultaneously avoid pathogen infection. These include the presence of immune cells from the maternal decidua, the selective physical barrier represented by the placenta, but also the presence of a chemical barrier that establishes a hostile environment for pathogens, notably provided by the secretion of cytokines, interferons and placental EVs [START_REF] Megli | Infections at the maternal-fetal interface: an overview of pathogenesis and defence[END_REF][START_REF] Hoo | Innate Immune Mechanisms to Protect Against Infection at the Human Decidual-Placental Interface[END_REF].

It has been widely proposed that placental EVs exhibit antiviral function [START_REF] Kalluri | The biology, function, and biomedical applications of exosomes[END_REF][START_REF] Brakhage | Host-derived extracellular vesicles for antimicrobial defense[END_REF].

Delorme-Axford et al. have proposed an EV-mediated transfer of antiviral resistance from primary human trophoblasts to non-placental cells infected with a large variety of viruses from different families [START_REF] Delorme-Axford | Human placental trophoblasts confer viral resistance to recipient cells[END_REF]. This phenomenon was attributed to a family of 46 miRNAs, all deriving from the largest miRNA cluster found on chromosome 19 (i.e. the C19MC cluster), that is exclusively expressed in the placenta. This primate-specific miRNA cluster, highly enriched in trophoblastic EVs, confers viral resistance by inducing autophagy once delivered to recipient cells [START_REF] Malnou | Imprinted MicroRNA Gene Clusters in the Evolution, Development, and Functions of Mammalian Placenta[END_REF][START_REF] Donker | The expression profile of C19MC microRNAs in primary human trophoblast cells and exosomes[END_REF][START_REF] Bortolin-Cavaillé | C19MC microRNAs are processed from introns of large Pol-II, non-protein-coding transcripts[END_REF]. Although the miRNA profile was similar between the different EV populations, the antiviral effect was specifically attributed to sEVs [START_REF] Ouyang | Isolation of human trophoblastic extracellular vesicles and characterization of their cargo and antiviral activity[END_REF]. sEV from pregnant women's plasma, abundantly found in maternal blood, and enriched in C19MC cluster also conferred this antiviral resistance [START_REF] Ouyang | Isolation of human trophoblastic extracellular vesicles and characterization of their cargo and antiviral activity[END_REF]. Some miRNAs in particular seem to be responsible for this resistance (i.e. miR-517-3p), either because they are abundantly expressed in EVs, or because they display an antiviral effect when expressed ectopically [START_REF] Bayer | Human trophoblasts confer resistance to viruses implicated in perinatal infection[END_REF]. It should be noted, however, that all these studies were carried out in models of term placenta. Whether the antiviral resistance also occurs at the beginning of pregnancy remains to be determined.

Taken together, this evidence indicates that placental EVs display widespread effects on normal pregnancy development. Placental EVs and associated content, once released into target cells, regulate tissue remodeling for embryo implantation, the balance between maternal tolerance towards the fetus and placenta, and pro-inflammatory events allowing implantation and maintenance of the embryo. They also play a pivotal role in antiviral protection, explained at least in part by their miRNA content, mainly from the C19MC cluster.

Placental EVs in pathological pregnancy

Gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a frequent metabolic disorder during pregnancy, affecting around 15% of pregnant women [START_REF] Zhu | Prevalence of Gestational Diabetes and Risk of Progression to Type 2 Diabetes: a Global Perspective[END_REF]. It is defined as an abnormality of glucose metabolism occurring or detected for the first-time during pregnancy. GDM is associated with pronounced insulin resistance and hyperglycemia in mother and fetus, leading to risks of gestational hypertension, premature delivery, fetal macrosomia amongst others, and a higher risk of developing type 2 diabetes as well as cardiovascular diseases several years after delivery for the mother and her offspring [START_REF] Xiong | Gestational diabetes mellitus: prevalence, risk factors, maternal and infant outcomes[END_REF][START_REF] Kim | Maternal outcomes and follow-up after gestational diabetes mellitus[END_REF][START_REF] Nijs | Gestational Diabetes Mellitus and the Long-Term Risk for Glucose Intolerance and Overweight in the Offspring: A Narrative Review[END_REF].

During GDM, placental EVs have been shown to be dysregulated, in term of abundance, composition and function compared to normal pregnancies [START_REF] Czernek | Exosomes as Messengers Between Mother and Fetus in Pregnancy[END_REF][START_REF] Bai | Placenta-Derived Exosomes as a Modulator in Maternal Immune Tolerance During Pregnancy[END_REF][START_REF] Bathla | Extracellular vesicles in gestational diabetes mellitus: A scoping review[END_REF][START_REF] James-Allan | Extracellular vesicles and their role in gestational diabetes mellitus[END_REF]. First, the concentration of circulating total and placental sEVs is higher by nearly two-fold in maternal circulation during GDM pregnancies compared to healthy pregnancies [START_REF] Salomon | Gestational Diabetes Mellitus Is Associated With Changes in the Concentration and Bioactivity of Placenta-Derived Exosomes in Maternal Circulation Across Gestation[END_REF]. Second, miRNA composition is also modified in circulating sEVs, notably miRNA involved in insulin regulation and glucose pathways [START_REF] Gillet | miRNA Profiles in Extracellular Vesicles From Serum Early in Pregnancies Complicated by Gestational Diabetes Mellitus[END_REF][START_REF] Thamotharan | Circulating extracellular vesicles exhibit a differential miRNA profile in gestational diabetes mellitus pregnancies[END_REF]. Placental EVs secreted from tissue explants also show a dysregulation of their miRNA content, with gene ontology analysis indicating alterations in pathways regulating cell migration and carbohydrate metabolism [START_REF] Nair | Human placental exosomes in gestational diabetes mellitus carry a specific set of miRNAs associated with skeletal muscle insulin sensitivity[END_REF]. In term of protein content, a proteomic study identified 78 differentially expressed proteins in GDM-derived sEVs isolated from maternal circulation compared to healthy pregnant women [START_REF] Jayabalan | Quantitative Proteomics by SWATH-MS Suggest an Association Between Circulating Exosomes and Maternal Metabolic Changes in Gestational Diabetes Mellitus[END_REF]. These differentially regulated proteins are primarily associated with energy production, inflammation, and metabolism. It has also been shown that trophoblastic sEVs express 8-fold more DiPeptidyl Peptidase IV (DPPIV) during GDM than in healthy pregnancy, an expression that is retrieved in peripheral plasma [START_REF] Kandzija | Placental extracellular vesicles express active dipeptidyl peptidase IV; levels are increased in gestational diabetes mellitus[END_REF].

These changes in miRNA and protein content in sEVs during GDM pregnancies impinge on their biological functions. For example, placental sEVs from GDM women decrease insulinstimulated migration and glucose uptake in primary skeletal muscle cells from healthy patients [START_REF] Nair | Human placental exosomes in gestational diabetes mellitus carry a specific set of miRNAs associated with skeletal muscle insulin sensitivity[END_REF]. sEVs isolated from the plasma of GDM pregnant women induce insulin resistance and glucose intolerance when injected in mice [START_REF] James-Allan | Regulation of glucose homeostasis by small extracellular vesicles in normal pregnancy and in gestational diabetes[END_REF]. The increase of DPPIV expression observed on GDM sEVs also favors insulin-resistance by decreasing circulating glucagon-like peptide-1 [START_REF] Kandzija | Placental extracellular vesicles express active dipeptidyl peptidase IV; levels are increased in gestational diabetes mellitus[END_REF].

Finally, first-trimester trophoblastic sEVs have been shown to induce the release of cytokines (IL-4, IL-6, IL-8, interferon-γ, and TNF-α) from endothelial cells upon glucose incubation [START_REF] Rice | The Effect of Glucose on the Release and Bioactivity of Exosomes From First Trimester Trophoblast Cells[END_REF].

Thus, placental EVs in the context of GDM may contribute to the pathophysiology of the disease at multiple levels, targeting different cell types and functions.

Recently, studies performed on urinary sEVs report a specific increase in the damages associated molecular pattern S100A9 protein at the 20 th week of pregnancy [START_REF] Ramachandrarao | Proteomic analyses of Urine Exosomes reveal New Biomarkers of Diabetes in Pregnancy[END_REF] and a decrease in the level of several C19MC miRNAs at the third trimester of gestation during GDM compared to healthy pregnancy [START_REF] Herrera-Van Oostdam | Placental exosomes isolated from urine of patients with gestational diabetes exhibit a differential profile expression of microRNAs across gestation[END_REF], indicating that urinary sEVs could be interesting sources of biomarkers for GDM.

Pre-eclampsia

In early pregnancy, abnormalities during trophoblastic development and the implantation process can lead to pre-eclampsia (PE). PE is characterized by systemic maternal symptoms (high blood pressure, proteinuria) that can lead to eclampsia and maternal death if untreated. The lack of blood flow between mother and fetus can also induce intra uterine growth restriction and other adverse effects on the fetus [START_REF] Chappell | Pre-eclampsia[END_REF]. As the exact etiology of PE remains unknown, treatments are mainly symptomatic as they are not specific to this disease. In addition, there is a high risk of very rapid deterioration of the maternal state and biomarkers to monitor the evolution of placental condition during PE are lacking. In this context, placental EVs have been extensively studied in PE both in disease pathophysiology and as potential biomarkers.

During PE, the total load of placental EVs increases and their composition is altered compared with EVs from control pregnant women [START_REF] Han | Syncytiotrophoblast-Derived Extracellular Vesicles in Pathophysiology of Preeclampsia[END_REF]. Trophoblastic EVs from patients with PE are enriched in active neprilysin compared to control patients, which may contribute to the maternal hypertension observed during PE [START_REF] Gill | Placental Syncytiotrophoblast-Derived Extracellular Vesicles Carry Active NEP (Neprilysin) and Are Increased in Preeclampsia[END_REF]. The overall lipidomic profile of trophoblastic EVs is also altered during PE with differences in certain lipid classes involved in oxidative stress, apoptosis, immune response, and coagulation [START_REF] Baig | Lipidomic analysis of human placental syncytiotrophoblast microvesicles in adverse pregnancy outcomes[END_REF]. Placental EVs from pregnant women with PE appear to imbalance macrophage polarization compared to healthy pregnancies and may therefore be an "self-promoter" of preeclamptic state in patients with PE [START_REF] Liu | Trophoblast-Derived Extracellular Vesicles Promote Preeclampsia by Regulating Macrophage Polarization[END_REF].

In an animal model, the administration of placental EVs purified from peripheral blood of pregnant women with PE induced PE-like disease in pregnant mice with vascular defects including disruption of the vascular endothelium and vasoconstriction [START_REF] Han | Placenta-derived extracellular vesicles induce preeclampsia in mouse models[END_REF]. Awoyemi et al. recently described that trophoblastic EVs purified by lobal perfusion of late PE placenta limit the pro-inflammatory immune response compared to healthy pregnancy and early PE trophoblastic EVs [START_REF] Awoyemi | Syncytiotrophoblast Extracellular Vesicles From Late-Onset Preeclampsia Placentae Suppress Pro-Inflammatory Immune Response in THP-1 Macrophages[END_REF]. This suggests that the disruption of the balance between pro/anti-inflammatory process evolves during pregnancy. Placental EVs are also found in amniotic fluid where they participate in maternal-fetal communication [START_REF] Czernek | Exosomes as Messengers Between Mother and Fetus in Pregnancy[END_REF]. EVs from amniotic fluid during PE show an altered phenotype compared to healthy pregnancy and display an antiangiogenic effect that may play a role in the development of PE [START_REF] Gebara | Single extracellular vesicle analysis in human amniotic fluid shows evidence of phenotype alterations in preeclampsia[END_REF].

Placental EVs are altered in amount and composition during PE [START_REF] Tannetta | Update of syncytiotrophoblast derived extracellular vesicles in normal pregnancy and preeclampsia[END_REF][START_REF] Pillay | Placental exosomes and pre-eclampsia: Maternal circulating levels in normal pregnancies and, early and late onset pre-eclamptic pregnancies[END_REF]. The miRNA composition of placental EVs found in the maternal blood of patients with pre-symptomatic PE who subsequently developed PE is different from that of the control group of healthy pregnant women. This prospective study identified miRNA that may be candidates for the development of biomarkers to identify pregnant women at high risk for developing PE [START_REF] Salomon | Placental Exosomes as Early Biomarker of Preeclampsia: Potential Role of Exosomal MicroRNAs Across Gestation[END_REF]. This active area of research is currently identifying miRNA candidates and analyzing the expression profile of placental EVs in the maternal circulation to develop non-invasive PE biomarker for diagnosis and monitoring [START_REF] Zou | miR-31-5p from placental and peripheral blood exosomes is a potential biomarker to diagnose preeclampsia[END_REF][START_REF] Levine | Syncytiotrophoblast extracellular microvesicle profiles in maternal circulation for noninvasive diagnosis of preeclampsia[END_REF]. Pro-microbial Infections during pregnancy are common and some can lead to serious sequelae for both mother and fetus [START_REF] Kourtis | Pregnancy and Infection[END_REF][START_REF] Leeper | Infections During Pregnancy[END_REF][START_REF] Sappenfield | Pregnancy and Susceptibility to Infectious Diseases[END_REF]. In particular, the pathogens found under the acronym TORCH (Toxoplasma gondii, other (Zika virus, Listeria monocytogenes (Lm) …), Rubella virus, human Cytomegalovirus (hCMV), Herpes Simplex virus) include viruses, bacteria and parasites involved in congenital infections. Transmission occurs mainly vertically across the placenta, and placental EVs participate in the dissemination of the pathogen in several infections and are altered in quantity, composition, and functions.

One example is congenital hCMV infection, which is the most common cause of infectious deafness and brain malformations, affecting 1% of live births [START_REF] Leruez-Ville | Cytomegalovirus infection during pregnancy: state of the science[END_REF]. Our team characterized EVs from first trimester placental tissue explants infected with hCMV and revealed some modifications of their surface markers [START_REF] Bergamelli | Human Cytomegalovirus Infection Changes the Pattern of Surface Markers of Small Extracellular Vesicles Isolated From First Trimester Placental Long-Term Histocultures[END_REF]. Moreover, protein content of EVs isolated from hCMV-infected cytotrophoblasts was modified towards a proviral phenotype, which correlated with their ability to potentiate the infection of naïve recipient fetal cells [START_REF] Bergamelli | Human Cytomegalovirus Modifies Placental Small Extracellular Vesicle Composition to Enhance Infection of Fetal Neural Cells In Vitro[END_REF]. A similar phenomenon has been described in the context of listeriosis infection in the work of Kaletka et al [START_REF] Kaletka | Listeria monocytogenes Infection Alters the Content and Function of Extracellular Vesicles Produced by Trophoblast Stem Cells[END_REF]. Lm is a Gram-positive food borne bacterium with placental tropism, which can in the most serious cases lead to severe infections of the newborn, premature deliveries or even fetal death [START_REF] Vázquez-Boland | Listeria Placental Infection[END_REF][START_REF] Johnson | Human Placental Trophoblasts Infected by Listeria monocytogenes Undergo a Pro-Inflammatory Switch Associated With Poor Pregnancy Outcomes[END_REF]. The infection of trophoblast stem cells by this pathogen lead to a modification of the protein and RNA content of the EVs derived from these cells [START_REF] Kaletka | Listeria monocytogenes Infection Alters the Content and Function of Extracellular Vesicles Produced by Trophoblast Stem Cells[END_REF]. In addition, the functional evaluation of these EVs showed an increased activation of macrophages, which were then in a pro-inflammatory state and more susceptible to infection by this bacterium. These two different examples thus illustrate how pathogens can impact on placental EV composition, which finally favor their dissemination, locally but also toward the fetal compartment.

Other examples are found in the literature, especially concerning Zika, a Flavivirus causing congenital infections that can lead to serious neurosensory sequelae in the fetus [START_REF] Freitas | Congenital Zika syndrome: A systematic review[END_REF]. Trophoblastic EVs see both their size and their composition modified, particularly in terms of proteins where the infection of the cells from which the EVs originate leads to an enrichment in mainly non-structural viral proteins [START_REF] Block | Zika virus impacts extracellular vesicle composition and cellular gene expression in macaque early gestation trophoblasts[END_REF]. Another team demonstrated by histopathology, carried out on human placentas from pregnant women naturally infected with Zika, an enlargement of the vesicles and apoptotic bodies of the syncytiotrophoblasts, associated with an absence of normal secretion of lEVs [START_REF] Rabelo | Zika Induces Human Placental Damage and Inflammation[END_REF].

Altogether, these different data demonstrate the importance of placental EVs during pregnancy pathologies. Dysregulation of their secretion and/or content is observed in most, if not all, gestational diseases. The question of whether this dysregulation is a consequence of the pathology or if it contributes to the pathogenesis of the disease remains to be decipher.

Finally, the fact that these dysregulated EVs are found in abundance in maternal serum during gestation make them interesting candidates as non-invasive biomarkers for pregnancy pathologies.

Perspectives

The field of placental EVs is expanding, with increasing interest and a growing number of studies highlighting their pivotal role across physiological and pathological gestations.

However, some confusions in the studies and the lack of precise terminology make interpretation and comparison of different reports more difficult. Clarification of these issues in the near future will help advance not only the field of placental EVs but also the entire EV field.

• Significant work is underway to define a clear nomenclature for discriminate between the different EV subpopulations. Most of the available data have been conducted on sEVs, but the literature has to be read with caution because some studies have not used the proper terms to identified the specific EV subpopulation considered in the study.

• Although placental EVs are mainly secreted by syncytiotrophoblasts, most studies do not specify the parental/donor cell type secreting EVs. To sort out placental EVs most authors focus on PLAP, syncytin-1 or C19MC miRNAs, which are specifically expressed in placental tissue. However, EVs secreted by embryonic appendages including amnion and umbilical cord) are sometimes mistaken for placental EVs.

• One question remains unanswered regarding the functional role of EVs in pathological pregnancies: is it a simple consequence of organ dysfunction or do placental EVs contribute to pathogenesis?

• The deregulation of placental EVs secretion and composition observed in pathological pregnancies makes them promising biomarkers for the diagnosis, prognosis and monitoring of gestational diseases.

Legend

Figure 1 .

 1 Figure 1. Effects of placental EVs in both physiological and pathological pregnancies. Large and small EVs are symbolized by circles in different shades of blue for the physiological pregnancies, red for the pathological pregnancies. Trophoblastic EVs can act in an autocrine manner on the placenta and in a paracrine manner on the fetal or maternal compartments to regulate different physiological processes indicated next to each compartment on the left of the figure, in blue boxes. They are also implicated in some pathological pregnancies, indicated in red boxes on the right of the figure. Created with Biorender.com.

Acknowledgments

We thank all lab members who participate to our daily work and scientific discussions, allowing the writing of this review

Funding Funding to C.M. doctoral thesis is provided by the Ministry of Education and Research (MESR) and her work is supported by the Villa M foundation. M.B. post-doctoral position is funded by the Horizon 2020 innovation (ERIN) grant (no. EU952516) of the European Commission and Wallenberg Academy Fellow (4-148/2017 and 2021.0188). CEM received financial support from the French Biomedicine Agency (19AMP008), the ANR Corofet grant (ANR-21-CE14-0030), institutional grants from INSERM, CNRS and Toulouse 3 University. Funding to G.D. is provided by the Fondation pour la Recherche Medicale (FRMEQU201903007837), Institut Curie and the Centre National de la Recherche Scientifique (CNRS).

Competing Interests

The authors declare that there are no competing interests associated with the manuscript.

Author Contributions

C.M., M.B., C.E.M and G.D. drafted the manuscript. All authors reviewed and approved the final version.


J.-B Hazo

M Melchior

A Rouquette

A Silini

S Rejaibi

M Zid

I Ben Slema

R Mallekh

N Zoghlami

S Ben Youssef

M Zribi

N Ben Salah

H Aounallah-Skhiri

A Forastiere

F Nobile

M Stafoggia

A Nakamura

L Broseus

J Tost

D Vaiman

S Martins

K Keyes

K Bonello

M Fekom

K Strandberg-Larsen

A.-L Sutter-Dallay

B Heude

J Lepeule

EPP0839 Epidemiological patterns of new psychoactive substances use in Tunisian school adolescents, 2021

est destinée au dépôt

Introduction:

The emergence of New Psycho-active Substances (NPS) such as Synthetic cannabinoid and cathinone, represents a challenging issue for drug policy globally. In order to set up new adjusted measures to limit this phenomenon extension, objective epidemiologic indicators are requested. Objectives: We aimed to determine the prevalence of Synthetic cannabinoid and cathinone consumption in Tunisian adolescents by gender and regional distribution. Methods: Data from the Mediterranean school survey on alcohol and other drugs (MedSPAD III-2021) were used. Based on threestage stratification sampling method, high school teenagers in first and second grades of secondary education, were enrolled. Data collection was performed using a self-administered standardized questionnaire. We examined weighted prevalence estimates of NPS use at least once in a lifetime (Synthetic cannabinoid and cathinone) by gender and regional distribution. Epi data software was used for data entry and all statistical analysis were performed with STATA software. Results: The survey included 6201 adolescents with a mean age of 16.8 years and a sex ratio female/male of 1.5. Synthetic cannabinoid's use was reported by 1.9%, 95% ] of students, with statistically significant difference between boys (4.1%) and girls (0.6%), p-value<10 -4 . This consumption was the highest in Tunis the capital city, the center-east and the north-east (2.7%, 2.2% and 2% respectively). As for synthetic cathinone's use, it was reported by 0.36% 95%CI [0.24-0.56] of our study sample, with statistically significant difference between boys (0.8%) and girls (0.8%), p-value<10 -4 . Conclusions: Our study highlighted an emerging use of NPS among high school students with significant male predominance. Further research on NPS epidemiology is, hence, needed to reinforce evidence-based management strategies aiming at fighting this phenomenon. Sensitization of decision makers to control accessibility, and increasing awareness among adolescents' close family / schoolstaff environment regarding this issue, are strongly recommended.

Disclosure of Interest: None Declared

EPP0840

Long-term exposure to air pollution and traffic noise and incidence of mental disorders: a large administrative cohort of adults Introduction: Air pollution is related to a global increase in mortality and morbidity. The literature on the adverse effects on mental disorders is still limited. Objectives: This study aims to investigate the associations between air pollutants and traffic noise with incidence of different categories of mental disorders and drug prescriptions in a large cohort administrative cohort. Methods: We enrolled 1,739,277 individuals 30þ years living in Rome at 2011 census, and followed them up until 31 st December 2019. We excluded subjects with prevalent mental disorders at baseline to evaluate the incidence of schizophrenia, bipolar, anxiety, personality and substance use disorders, as well as prescriptions of antipsychotics, antidepressants and anticonvulsants. We assigned annual average concentrations of fine particulate matter (PM 2.5 ), nitrogen dioxide (NO 2 ), Black Carbon (BC), ultrafine particles (UFPs) and noise exposure to baseline residential addresses. We applied Cox regression models with adjustment for individual and area-level covariates.

Results: This study identified variable numbers of incident cases, from 1,280 cases for personality disorders to 200,549 for antidepressants. Each interquartile range increase in PM 2.5 (1.13μg/ m 3 ) was associated with a hazard ratio (HR) of 1.07 (95% confidence interval: 1.017, 1.127) for schizophrenia spectrum disorder, 1.135 (1.086, 1.186) for depression, 1.097 (1.030, 1.168) for anxiety disorders and 1.112 (1.030-1.200) for substance use disorders. Positive associations were also detected for the other exposures and with the three categories of drug prescriptions. In two-exposure models, PM 2.5 , UFPs and noise remained associated with schizophrenia spectrum disorders, depression and antidepressant drugs use. The effects were higher in the age group 30-64 than in the 65þ. Sensitivity analyses generally yielded similar results Conclusions: Long-term exposure to air pollutants and noise was associated with increased risks of schizophrenia spectrum disorders, depression and anxiety disorders. The associations with prescriptions of specific drugs increase the credibility of the results. Objectives: To explore the association of continued aboverecommendation screen use for one year since May 2020 with behaviour problems in the summer of 2021 in children aged 3 to 14 years. Methods: Data came from the French EpiCov cohort study, and were collected in May 2020 and at first (Autumn 2020) and second follow-up (Summer 2021) among 1,089 participants with children aged 3 to 14. Children had a 1-year above-recommendation screen use if their daily mean time exceeded recommendations at the three follow-up times (one hour, for children aged 3-5, two for the older ones). Behaviour problems were assessed using the Strengths and Difficulties Questionnaire (SDQ) and valid cut-offs for Internalizing (emotional or peer problems) and Externalizing (conduct problems or hyperactivity/inattention) problems completed in summer 2021. Data were analysed using adjusted logistic regression. Results: 1-year above-recommendation screen use was not associated with internalizing problems (OR [95% CI]: 1.20 [0.90-1.59]). Regarding the subscales, it was associated with a higher risk of peer problems (1.42 [1.04-1.95]). A higher risk of externalizing problems was found only in 11-14-year-olds (1.63 [1.01-2.63]), especially conduct problems in 11-14-year-olds (1.91 [1.15-3.22]) but not in other age groups.

Disclosure of

Conclusions: This study found that maintaining screen time beyond recommendations for 1 year since the onset of the pandemic was associated with peer problems in children aged 3-14 years and externalizing and conduct problems in 11-14 years. Despite this very specific context, exposure to screens is not trivial. If this situation were to occur again, we would have to anticipate, with prevention messages, by keeping schools open.

Disclosure of Interest: None Declared

EPP0842

Smoking status trajectories, intergenerational socioeconomic mobility and depression: Preliminary results from 107,734 French adults (18 to 75 years) of the CONSTANCES cohort Introduction: Cigarette smoking prevalence is significantly higher among people with mental health problems than among the general population. Smoking accounts for much of the reduction in life expectancy associated with mental illness, why the high co-occurrence of smoking and mental health illness is a major public health concern. Persons belonging to socioeconomical disadvantaged groups have higher risk of mental health conditions and also higher smoking rates. Objectives: In this study we aim to examine smoking trajectories among adult smokers between 2012 and 2020. Furthermore, we aim to investigate differences in smoking trajectories by adult depression by taking into consideration participants intergenerational socioeconomic mobility (ISEM). Methods: Analyses were based on data from CONSTANCES, a French general population cohort conducted from 2012 to 2020. In total were 107,734 participants included after exclusion of never smokers. Depression was measured by the CES-D scale, and depression was classified with a score ≥16. ISEM is based on childhood (maternal and parental occupational grade) and adult socioeconomic position (SEP), and low ISEM includes those with low SEP as child and adult and high ISEM those with consistent high SEP. Group-based trajectories modelling (GBTM) was used to determine smoking status trajectories. To address the association between ISEM and smoking trajectory class we used multinomial logistic regression with former smokers as reference class adjusted for depression, household income, sex and age. Results: We identified five smoking trajectories 1) Former smokers (56.6%), 2) Long-term smokers (26.4%), 3) Intermediate smokers (3.3%), 4) Early quitters (5.0%) and 5) Late quitters (8.7% Conclusions: Preliminary results showed an association between ISEM and smoking trajectories in our study. Persons with low ISEM are more likely to be long-term smokers. Future analysis should consider the effect of depression as a mediating factor on the association between ISEM and smoking trajectories.

Disclosure of Interest: None Declared

EPP0843

Associations between placental DNA methylation and emotional and behavioral outcomes in preschoolers: insights from the EDEN Mother-Child Cohort study Introduction: Behavioral (externalizing) and emotional (internalizing) problems were showed to be associated with the prenatal environment. Changes in placental DNA methylation was identified as a relevant potential mechanism of such association.

  Interest: None Declared EPP0841 1-year above-recommendation screen use and internalizing and externalizing behaviours in French children aged 3 to 14 years A. Descarpentry 1 *, C. Davisse-Paturet 1 , C. Galera 2,3,4 , J.-B. Hazo 5 , M. Melchior 6 and A. Rouquette 1,7Introduction: The context of the COVID-19 pandemic has changed the daily life of families and children. Screen exposure was increased during this period to maintain social relationships, work remotely, and occupy leisure time.

  ). Preliminary results from multinomial logistic regression showed that persons with low ISEM had higher odds of depression (OR [95%CI] =1.91 [1.77;2.06]) than those with high ISEM. Participants with low ISEM had higher odds of being long-term smoking than former smokers compared to those with high ISEM (ORa [95%CI]=1.55 [1.43;1.67]). Furthermore, those with low ISEM had lower odds of being in any of the other smoking trajectory groups vs. former smokers compared to those with high ISEM (ORa [95%CI]=0.82 [0.69;0.97]) for intermediate smokers, ORa [95%CI]=0.75 [0.66;0.85]) for early quitters, and ORa [95%CI]=0.78 [0.70;0.87]) for late quitters).

https://doi.org/10.1192/j.eurpsy.2023.1125 Published online by Cambridge University Press

IPLESP, ERES, INSERM, Sorbonne University, Paris, France *Corresponding author. doi: 10.1192/j.eurpsy.2023.1126