Search

International audience; Introduction The use of paclitaxel in pregnant cancer patients is feasible in terms of fetal safety, but little is known about the effects of paclitaxel on the placenta. Using three experimental models, we aimed to assess the effects of paclitaxel on the expression of placental drug transporters. Methods In the in vitro model (human primary trophoblast culture), trophoblasts were isolated from normal term placentas and subsequently exposed to paclitaxel. The transcriptional regulation of 84 genes encoding for drug transporters, and the protein expression of ABCB1/P-gp and ABCG2/BCRP were assessed. In the in vivo model, placental tissues isolated from pregnant cancer patients treated with paclitaxel were analyzed to assess the protein expression of ABCB1/P-gp and ABCG2/BCRP. The same parameters were assessed in extracts from human placental cotyledons perfused ex vivo with paclitaxel. Results In the in vitro model, the expression of twelve drug-transporters genes was found to be significantly down-regulated after exposure to paclitaxel, including ABCC10, SLC28A3, SLC29A2, and ATP7B (involved in the transport of taxanes, antimetabolites, and cisplatin, respectively). The protein expression of ABCB1/P-gp increased by 1.3-fold after paclitaxel administration. Finally, the protein expression of ABCB1/P-gp and ABCG2/BCRP was higher in cotyledons from mothers treated with multiple doses of paclitaxel during pregnancy than in cotyledons perfused with a single dose of paclitaxel. Discussion Paclitaxel modulates the expression of placental drug transporters involved in the disposition of various anticancer agents. Further studies will be needed to assess the impact of repeated or prolonged exposure to paclitaxel on the expression and function of placental drug transporters.

Placental functioning relies on the appropriate differentiation of progenitor villous cytotrophoblasts (CTBs) into extravillous cytotrophoblasts (EVCTs), including invasive EVCTs, and the multinucleated syncytiotrophoblast (ST) layer. This is accompanied by a general move away from a proliferative, immature phenotype. Genome-scale expression studies have provided valuable insight into genes that are associated with the shift to both an invasive EVCT and ST phenotype, whereas genome-scale DNA methylation analysis has shown that differentiation to ST involves widespread methylation shifts, which are counteracted by low oxygen. In the current study, we sought to identify DNA methylation variation that is associated with transition from CTB to ST in vitro and from a noninvasive to invasive EVCT phenotype after culture on Matrigel. Of the several hundred differentially methylated regions that were identified in each comparison, the majority showed a loss of methylation with differentiation. This included a large differentially methylated region (DMR) in the gene body of death domain-associated protein 6 (DAXX ), which lost methylation during both CTB syncytialization to ST and EVCT differentiation to invasive EVCT. Comparison to publicly available methylation array data identified the same DMR as among the most consistently differentially methylated genes in placental samples from preeclampsia pregnancies. Of interest, in vitro culture of CTB or ST in low oxygen increases methylation in the same region, which correlates with delayed differentiation. Analysis of combined epigenomics signatures confirmed DAXX DMR as a likely regulatory element, and direct gene expression analysis identified a positive association between methylation at this site and DAXX expression levels. The widespread dynamic nature of DAXX methylation in association with trophoblast differentiation and placenta-associated pathologies is consistent with an important role for this gene in proper placental development and function.-Novakovic, B., Evain-Brion, D., Murthi, P., Fournier, T., Saffery, R. Variable DAXX gene methylation is a common feature of placental trophoblast differentiation, preeclampsia, and response to hypoxia.

Placental development is particularly altered in trisomy of chromosome 21 (T21)–affected pregnancies. We previously described in T21-affected placentae an abnormal paracrine crosstalk between the villus mesenchymal core and villus trophoblasts. T21-affected placentae are known to be characterized by their hypovascularity. However, the causes of this anomaly remain not fully elucidated. Therefore, the hypothesis of an abnormal paracrine crosstalk between fetal mesenchymal core and placental endothelial cells (PLECs) was evocated. Villus mesenchymal cells from control (CMCs) and T21 placentae (T21MCs) were isolated and grown in culture to allow their characterization and collection of conditioned media for functional analyses (CMC-CM and T21MC-CM, respectively). Interestingly, PLEC proliferation and branching ability were less stimulated by T21MC-CM than by CMC-CM. Protein array analysis identified secreted proangiogenic growth factors in CMC-CM, which were reduced in T21MC-CM. Combined mass spectrometry and biochemical analysis identified spondin-2 as a factor decreased in T21MC-CM compared with CMC-CM. We found that exogenous spondin-2 stimulated PLEC proliferation and established that T21MC-CM supplemented with spondin-2 recovered conditioned media ability to induce PLEC proliferation and angiogenesis. Hence, this study demonstrates a crosstalk between villus mesenchymal and fetal endothelial cells, in which spondin-2 secreted from mesenchymal cells plays a central role in placental vascular functions. Furthermore, our results also suggest that a reduction in spondin-2 secretion may contribute to the pathogenesis of T21 placental hypovascularity.

Homeobox genes regulate embryonic and placental development, and are widely expressed in the human placenta, but their regulatory control by DNA methylation is unclear. DNA methylation analysis was performed on human placentae from first, second and third trimesters to determine methylation patterns of homeobox gene promoters across gestation. Most homeobox genes were hypo-methylated throughout gestation, suggesting that DNA methylation is not the primary mechanism involved in regulating HOX genes expression in the placenta. Nevertheless, several genes showed variable methylation patterns across gestation, with a general trend towards an increase in methylation over gestation. Three genes (TLX1, HOXA10 and DLX5) showed inverse gains of methylation with decreasing mRNA expression throughout pregnancy, supporting a role for DNA methylation in their regulation. Proteins encoded by these genes were primarily localised to the syncytiotrophoblast layer, and showed decreased expression later in gestation. siRNA mediated downregulation of DLX5, TLX1 and HOXA10 in primary term villous cytotrophoblast resulted in decreased proliferation and increased expression of differentiation markers, including ERVW-1. Our data suggest that loss of DLX5, TLX1 and HOXA10 expression in late gestation is required for proper placental differentiation and function.

The placenta is a transient organ essential for fetal development. During human placental development, chorionic villi grow in coordination with a large capillary network resulting from both vasculogenesis and angiogenesis. Angiogenin is one of the most potent inducers of neovascularisation in experimental modelsin vivo. We and others have previously mapped angiogenin expression in the human term placenta. Here, we explored angiogenin involvement in early human placental development. We studied, angiogenin expression byin situhybridisation and/or by RT-PCR in tissues and primary cultured trophoblastic cells and angiogenin cellular distribution by coimmunolabelling with cell markers: CD31 (PECAM-1), vascular endothelial cadherin (VE-cadherin), vascular endothelial growth factor receptor-2 (VEGF-R2), Tie-2, von Willebrand factor, CD34, erythropoeitin receptor (Epo-R), alpha-smooth muscle actin, CD45, cytokeratin 7, and Ki-67. Extravillous and villous cytotrophoblasts, isolated and differentiatedin vitro, expressed and secreted angiogenin. Angiogenin was detected in villous trophoblastic layers, and structured and nascent fetal vessels. In decidua, it was expressed by glandular epithelial cells, vascular cells and macrophages. The observed pattern of angiogenin expression is compatible with a role in blood vessel formation and in cross-talk between trophoblasts and endothelial cells. In view of angiogenin properties, we suggest that angiogenin may participate in placental vasculogenesis and organogenesis.

With more than 830,000 live births in France, a great number of pregnant women are concerned by a treatment during pregnancy and many questions revolve around appreciating medication-related risks during pregnancy. The human placenta is the interface between mother and fetus and remains difficult to study for ethical reasons. Placental transfer of drugs from mother to fetus is dependent on their physicochemical properties, maternal and fetal factors and placental factors. The human placental perfusion model is the only experimental model to study human placental transfer of drugs in organized placental tissue. In vitro models utilizing cell cultures are mostly limited to the investigation of cellular toxicity along pregnancy or specific transfer mechanisms, such as their interaction with transporters. Taking advantage of the complementarity of these models, it will be possible to develop a rational use of drugs during this period.

Human idiopathic fetal growth restriction (FGR) is associated with placental insufficiency. Previously, we reported that the expression of homeobox gene Distal-less 3 (DLX3) is increased in idiopathic FGR placentae and is a regulator of villous trophoblast differentiation. Here, we identify the downstream targets of DLX3 in trophoblast-derived cell lines. We modelled the high levels of DLX3 in FGR using an over-expression plasmid construct and complemented this using short-interference RNA (siRNA) for inactivation in cultured cells. Using a real-time PCR-based gene profiling, candidate target genes of DLX3 over-expression and inactivation were identified as regulators of trophoblast differentiation; GATA2 and PPARγ. The expression of GATA2 and PPARγ were further assessed in placental tissues and showed increased mRNA and protein levels in FGR-affected tissues compared with gestation-matched controls. We conclude that DLX3 orchestrates the expression of multiple regulators of trophoblast differentiation and that expression of these regulatory genes is abnormal in FGR.

Abnormal trophoblast function is associated with human fetal growth restriction (FGR). Targeted disruption of homeobox gene transforming growth β-induced factor (TGIF-1) results in placental dysfunction in the mouse. The role of human TGIF-1 in placental cell function is unknown. The aims of this study were to determine the expression of TGIF-1 in human idiopathic FGR-affected placentae compared with gestation-matched controls (GMC), to elucidate the functional role of TGIF-1 in trophoblasts and to identify its downstream targets. Real-time PCR and immunoblotting revealed that TGIF-1 mRNA and protein expression was significantly increased in FGR-affected placentae compared with GMC (n = 25 in each group P < 0.05). Immunoreactive TGIF-1 was localized to the villous cytotrophoblasts, syncytiotrophoblast, microvascular endothelial cells and in scattered stromal cells in both FGR and GMC. TGIF-1 inactivation in BeWo cells using two independent siRNA resulted in significantly decreased mRNA and protein of trophoblast differentiation markers, human chorionic gonadotrophin (CGB/hCG), syncytin and 3β-hydroxysteroid dehydrogenase/3β-honest significant difference expression. Our data demonstrate that homeobox gene TGIF-1 is a potential up-stream regulator of trophoblast differentiation and the altered TGIF-1 expression may contribute to aberrant villous trophoblast differentiation in FGR.

Placental functioning relies on the appropriate differentiation of progenitor villous cytotrophoblasts (CTBs) into extravillous cytotrophoblasts (EVCTs), including invasive EVCTs, and the multinucleated syncytiotrophoblast (ST) layer. This is accompanied by a general move away from a proliferative, immature phenotype. Genome-scale expression studies have provided valuable insight into genes that are associated with the shift to both an invasive EVCT and ST phenotype, whereas genome-scale DNA methylation analysis has shown that differentiation to ST involves widespread methylation shifts, which are counteracted by low oxygen. In the current study, we sought to identify DNA methylation variation that is associated with transition from CTB to ST

The effects of fluid shear stress (FSS) on the human syncytiotrophoblast and its biological functions have never been studied. During pregnancy, the syncytiotrophoblast is the main source of placental growth factor (PlGF), a proangiogenic factor involved in the placental angiogenesis and the vascular adaptation to pregnancy. The role of FSS in regulating PlGF expression in syncytiotrophoblasts is unknown. We investigated the impact of FSS on the production and secretion of the PlGF by the human syncytiotrophoblasts in primary cell culture. Laminar and continuous FSS (1 dyn cm −2 ) was applied to human syncytiotrophoblasts cultured in a parallel-plate flow chambers. Secreted levels of PlGF, sFlt-1 (soluble fms-like tyrosin kinase-1), and prostaglandin E2 were tested by immunologic assay. PlGF levels of mRNA and intracellular protein were examined by RT-PCR and Western blot, respectively. Intracellular cAMP levels were examined by time-resolved fluorescence resonance energy transfer cAMP accumulation assay. Production of cAMP and PlGF secretion was significantly increased in FSS conditions compared with static conditions. Western blot analysis of cell extracts exposed to FSS showed an increased phosphorylation of protein kinase A substrates and cAMP response element-binding protein on serine 133. FSS-induced phosphorylation of cAMP response element-binding protein and upregulation of PlGF were prevented by inhibition of protein kinase A with H89 (3 μmol/L). FSS also triggers intracellular calcium flux, which increases the synthesis and release of prostaglandin E2. The enhanced intracellular cAMP in FSS conditions was blocked by COX1/COX2 (cyclooxygenase) inhibitors, suggesting that the increase in prostaglandin E2 production could activate the cAMP/protein kinase A pathway in an autocrine/paracrine fashion. FSS activates the cAMP/protein kinase A pathway leading to upregulation of PlGF in human syncytiotrophoblast.

During pregnancy, the placenta ensures multiple functions, which are directly involved in the initiation, fetal growth and outcome of gestation. The placental tissue involved in maternal-fetal exchanges and in synthesis of pregnancy hormones is the mononucleated villous cytotrophoblast (VCT) which aggregates and fuses to form and renew the syncytiotrophoblast (ST). Knowledge of the gene expression pattern specific to this endocrine and exchanges tissue of human placenta is of major importance to understand functions of this heterogeneous and complex tissue. Therefore, we undertook a global analysis of the gene expression profiles of primary cultured-VCT (n = 6) and in vitro-differentiated-ST (n = 5) in comparison with whole term placental tissue from which mononucleated VCT were isolated. A total of 880 differentially expressed genes (DEG) were observed between VCT/ST compared to whole placenta, and a total of 37 and 137 genes were significantly up and down-regulated, respectively, in VCT compared to ST. The 37 VCT-genes were involved in cellular processes (assembly, organization, and maintenance), whereas the 137 ST-genes were associated with lipid metabolism and cell morphology. In silico, all networks were linked to 3 transcriptional regulators (PPARγ, RARα and NR2F1) which are known to be essential for trophoblast differentiation. A subset of six DEG was validated by RT-qPCR and four by immunohistochemistry. To conclude, recognition of these pathways is fundamental to increase our understanding of the molecular basis of human trophoblast differentiation. The present study provides for the first time a gene expression signature of the VCT and ST compared to their originated term human placental tissue.

The effects of fluid shear stress (FSS) on the human syncytiotrophoblast and its biological functions have never been studied. During pregnancy, the syncytiotrophoblast is the main source of placental growth factor (PlGF), a proangiogenic factor involved in the placental angiogenesis and the vascular adaptation to pregnancy. The role of FSS in regulating PlGF expression in syncytiotrophoblasts is unknown. We investigated the impact of FSS on the production and secretion of the PlGF by the human syncytiotrophoblasts in primary cell culture. Laminar and continuous FSS (1 dyn cm−2) was applied to human syncytiotrophoblasts cultured in a parallel-plate flow chambers. Secreted levels of PlGF, sFlt-1 (soluble fms-like tyrosin kinase-1), and prostaglandin E2 were tested by immunologic assay. PlGF levels of mRNA and intracellular protein were examined by RT-PCR and Western blot, respectively. Intracellular cAMP levels were examined by time-resolved fluorescence resonance energy transfer cAMP accumulation assay. Production of cAMP and PlGF secretion was significantly increased in FSS conditions compared with static conditions. Western blot analysis of cell extracts exposed to FSS showed an increased phosphorylation of protein kinase A substrates and cAMP response element-binding protein on serine 133. FSS-induced phosphorylation of cAMP response element-binding protein and upregulation of PlGF were prevented by inhibition of protein kinase A with H89 (3 μmol/L). FSS also triggers intracellular calcium flux, which increases the synthesis and release of prostaglandin E2. The enhanced intracellular cAMP in FSS conditions was blocked by COX1/COX2 (cyclooxygenase) inhibitors, suggesting that the increase in prostaglandin E2 production could activate the cAMP/protein kinase A pathway in an autocrine/paracrine fashion. FSS activates the cAMP/protein kinase A pathway leading to upregulation of PlGF in human syncytiotrophoblast.

The peroxisome proliferator-activated receptor-γ (PPARγ) is a member of the nuclear receptor superfamily that controls in a ligand-dependent manner the expression of a large array of genes involved in the control of energy homeostasis and in cell differentiation, proliferation, apoptosis, and the inflammatory process. Unexpectedly, genetic studies performed in mice established that PPARγ is essential for placental development. In the human placenta, PPARγ is specifically expressed in the trophoblast, both endocrine villous and invasive extravillous cytotrophoblasts (EVCT). Activation of PPARγ induces accumulation of lipids, villous trophoblast differentiation and inhibits trophoblast invasiveness. Oxidized LDLs that contain potential PPARγ ligands, but not native LDL, induce PPARγ transcriptional activity and inhibit trophoblast invasion in vitro. Recently, human cytomegalovirus (HCMV) was shown to activate trophoblastic PPARγ for its own replication and consequently inhibits invasiveness of infected cytotrophoblasts. Analysis of PPARγ target genes revealed trophoblastic factors described to control trophoblast invasiveness and surprisingly chorionic gonadotropin hormone (hCG), known to be mainly produced by the endocrine villous trophoblast. Analysis of hCG gene expression revealed opposite regulation by PPARγ in the two trophoblast subtypes. Finally, a hyperglycosylated form of hCG (hCG-H) only produced by invasive EVCT was shown to promote trophoblast invasion. Together, these data underscore the major role of PPARγ and its target genes, such as hCG, in the control of human trophoblast differentiation and invasion, and suggest that over-activation of this nuclear receptor following HCMV infection or by excess of ligands at the maternal–fetal interface could impair implantation and placentation and therefore embryonic development.

RESUME Le role du placenta au cours de la grossesse normale et pathologique reste encore trop mal connu. Cependant au cours de ces dernieres annees de nouveaux aspects de la biologie du trophoblaste ont ete reveles. D’une part l’environnement en oxygene et des proteines d’enveloppe retrovirale, specifiquement exprimees dans le trophoblaste, semblent jouer un role fondamental dans sa differenciation morphologique et fonctionnelle. D’autre part, les fonctions hormonales trophoblastiques evoluent qualitativement et quantitativement, d’un role paracrine au premier trimestre de la grossesse vers plus tardivement un role endocrine impliques dans la placentation et la quiescence uterine. Ces elements ouvrent de nouvelles perspectives diagnostiques et therapeutiques des pathologies de la grossesse d’origine placentaire.

During pregnancy, the placenta ensures multiple functions, which are directly involved in the initiation, outcome of gestation and fetal growth. Human implantation involves a major invasion of the uterus wall and a complete remodeling of the uterine arteries by the extravillous cytotrophoblasts (EVCT) during the first trimester of pregnancy. Abnormality of these early steps of placental development leads to poor placentation, fetal growth defects and is very often associated with preeclampsia, a major and frequent complication of human pregnancy. Unexpectedly, genetic studies performed in mice established that the peroxisome proliferator-activated receptor-gamma (PPARgamma) is essential for placental development. In the human placenta, PPARgamma is specifically expressed in the villous cytotrophoblast (VCT) and the syncytiotrophoblast (ST) as well as in the EVCT along their invasive pathway. To study the mechanisms that control human trophoblast invasion during early placental development and to provide new insight in the understanding of preeclampsia, we have developed in vitro models of human invasive trophoblasts. We observed that activation of the ligand-activated nuclear receptor PPARgamma agonists inhibits the trophoblastic invasion process in a concentration-dependent manner. Analysis of PPARgamma-target genes revealed that placental growth hormone, the protease PAPP-A and the human chorionic gonadotropin hormone (hCG) might be involved in the PPARgamma-mediated effect in an autocrine manner. The presence of oxidized-LDLs at the maternofetal interface suggests that oxidized-LDLs from maternal sera might be a source of potential PPARgamma ligands for the trophoblasts. Indeed, oxidized-LDLs decrease trophoblast invasion in vitro and analysis of their content revealed that they contain potent PPARgamma agonists such as eicosanoids, but also oxysterols, which are ligands for another nuclear receptor, the liver X Receptor (LXR). LXRbeta was found to be expressed in trophoblast and LXR agonists shown to inhibit trophoblast invasion. Together, these data underscore a major role for PPARgamma in the control of human trophoblast invasion during early placental development and suggest that ligands such as oxidized-LDLs at the implantation site might contribute to the modulation of trophoblast invasion through activation of PPARgamma and LXRbeta, two nuclear receptors that modulate the human trophoblastic cell invasion process.

This is an author-produced version of a manuscript accepted for publication in The Journal of Immunology (The JI). The American Association of Immunologists, Inc. (AAI), publisher of The JI, holds the copyright to this manuscript. This version of the manuscript has not yet been copyedited or subjected to editorial proofreading by The JI; hence, it may differ from the final version published in The JI (online and in print). AAI (The JI) is not liable for errors or omissions in this author-produced version of the manuscript or in any version derived from it. The final, citable version of record can be found at www.jimmunol.org.; International audience; Spontaneous preterm delivery is linked to intrauterine inflammation. Fetal membranes are involved in the inflammatory process as an important source of mediators, and the chorion leave produces high levels of the proinflammatory cytokine TNF-alpha when stimulated by LPS. The transcription factor NF-kappaB is the main regulator of this inflammatory process and controls the production of cytokines by the chorion leave. Phosphodiesterase 4 inhibitors are recognized for their anti-inflammatory and myorelaxant effects. The purpose of this study was to investigate whether PDE4 inhibition affects the LPS signaling in human cultured chorionic cells. We showed that these cells express TLR4, the main LPS receptor, and exhibit a predominant PDE4 activity. Upon LPS challenge, PDE4 activity increases concomitantly to the induction of the specific isoform PDE4B2 and chorionic cells secrete TNF-alpha. LPS induces the nuclear translocation of the NF-kappaB p65 subunit and the activation of three different NF-kappaB complexes in chorionic cells. The presence of the PDE4 inhibitor rolipram reduces the TNF-alpha production and the activation of the three NF-kappaB complexes. These data indicate that the PDE4 family interacts with the LPS signaling pathway during the inflammatory response of chorionic cells. PDE4 selective inhibitors may thus represent a new therapeutic approach in the management of inflammation-induced preterm delivery.

Recently, the expression of a human endogenous retrovirus HERV-FRD, able to encode a fusogenic envelope protein (syncytin 2), has been observed in human placenta. The aim of the present study was to localize the expression of syncytin 2 in first trimester placenta. In addition, we investigated the presence of HERV-FRD transcripts during the in vitro differentiation of isolated villous and extravillous trophoblastic cells from first trimester chorionic villi. Using a monoclonal antibody specifically raised against the HERV-FRD Env protein, syncytin 2 was immunolocalized only in the villous trophoblast of the chorionic villi, at the level of cytotrophoblastic cells. Interestingly, immunostaining was not observed in all cells but only in some of them, and was detected, more frequently, at the membrane level at the interface between the cytotrophoblastic cells and syncytiotrophoblast. Labeling was observed neither in the syncytiotrophoblast nor in the mesenchymal core of the villi nor in the extravillous trophoblast. In vitro detection of HERV-FRD transcripts was restricted to villous trophoblastic cells and decreased significantly with time in culture. These results suggest that syncytin 2 might play a role in human trophoblastic cell fusion.

International audience; Annexin-A5 (AnxA5) is the smallest member of the annexins, a group of soluble proteins that bind to membranes containing negatively-charged phospholipids, principally phosphatidylserine, in a Ca 2+-dependent manner. AnxA5 presents unique properties of binding and self-assembling on membrane surfaces, forming highly ordered two-dimensional (2D) arrays. We showed previously that AnxA5 plays a central role in the machinery of cell membrane repair of murine perivascular cells, promoting the resealing of membrane damages via the formation of 2D protein arrays at membrane disrupted sites and preventing the extension of membrane ruptures. As the placenta is one of the richest source of AnxA5 in humans, we investigated whether AnxA5 was involved in membrane repair in this organ. We addressed this question at the level of human trophoblasts, either mononucleated cytotrophoblasts or multinucleated syncytiotrophoblasts, in choriocarcinoma cells and primary trophoblasts. Using established procedure of laser irradiation and fluorescence microscopy, we observed that both human cytotrophoblasts and syncytiotrophoblasts repair efficiently a μm 2-size disruption. Compared to wild-type cells, AnxA5-deficient trophoblasts exhibit severe defect of membrane repair. Through specifically binding to the disrupted site as early as a few seconds after membrane wounding, AnxA5 promotes membrane resealing of injured human trophoblasts. In addition, we observed that a large membrane area containing the disrupted site was released in the extracellular milieu. We propose mechanisms ensuring membrane resealing and subsequent lesion removal in human trophoblasts. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

International audience; In addition to nourishing the embryo, extra-embryonic tissues (EETs) contribute to early em-bryonic patterning, primitive hematopoiesis, and fetal health. These tissues are of major importance for human medicine, as well as for efforts to improve livestock efficiency, but they remain incompletely understood. In bovines, EETs are accessible easily, in large amounts, and prior to implantation. We took advantage of this system to describe, in vitro and in vivo, the cell types present in bovine EETs at Day 18 of development. Specifically, we characterized the gene expression patterns and phenotypes of bovine extra-embryonic ectoderm (or trophoblast; bTC), endoderm (bXEC), and mesoderm (bXMC) cells in culture and compared them to their respective in vivo micro-dissected cells. After a week of culture, certain characteristics (e.g., gene expression) of the in vitro cells were altered with respect to the in vivo cells, but we were able to identify "cores" of cell-type-specific (and substrate-independent) genes that were shared between in vitro and in vivo samples. In addition, many cellular phenotypes were cell-type-specific with regard to extracellular adhesion. We evaluated the ability of individual bXMCs to migrate and spread on micro-patterns, and observed that they easily adapted to diverse environments, similar to in vivo EE mesoderm cells, which encounter different EE epithelia to form chorion, yolk sac, and allantois. With these tissue interactions , different functions arose that were detected in silico and corroborated in vivo at D21-D25. Moreover, analysis of bXMCs allowed us to identify the EE cell ring surrounding the embryonic disc (ED) at D14-15 as mesoderm cells, which had been hypothesized but not shown prior to this study. We envision these data will serve as a major resource for the future in the analysis of peri-implanting phenotypes in response to the maternal metabolism and contribute to subsequent studies of placental/fetal development in eutherians.

Our aim was to study the toxicity of benzo(a)pyrene (BaP), an environmental pollutant that can reach placenta, on two human placental models in order to propose biomarkers in risk assessment for pregnancy. Ex vivo human placental cells isolated from term placenta and JEG-3 cancer cell line were incubated with BaP at 0.1-10 μM for 48 h or 72 h. BaP induced neither loss of cell viability nor apoptosis in ex vivo placental cells. To go further, we performed experiments on JEG-3 cell line that provides near-unlimited cells. The results we obtained in JEG-3 cells confirmed that BaP, in our experimental conditions, is neither necrotic nor apoptotic for placental cells. BaP toxicity on placental cells resulted in cell cycle arrest (G2/M phase) associated with inhibition of cell proliferation. Besides, we observed that BaP remodeled the protein content of membrane microdomains via increased expression of ZO-1, caveolin-1 and P2X7 cell degenerescence receptor. In conclusion, we identified nuclear and membrane potential biomarkers of risks for placenta and then pregnancy. These potential biomarkers detected on placental cell lines could represent useful tools for toxicological studies.

Superoxide dismutases' (SODs) expression is altered in several diseases including Alzheimer, atherosclerosis, cancer and psoriasis. Previously, we reported a marked increase in Mn-SOD and Cu,Zn-SOD functional activity in human dermal psoriatic fibroblasts. As retinoic acid (RA) has been used in the treatment of psoriasis and a mechanism for its beneficial effects is not understood, we investigated the effects of RA on SOD mRNA and protein expression levels in human normal and psoriatic fibroblasts. Prior to RA exposure, Cu,Zn-SOD protein and mRNA levels were similar in normal compared to psoriatic fibroblasts while Mn-SOD protein and mRNA levels were increased in psoriatic cells. However, in contrast to normal fibroblasts, exposure of psoriatic fibroblasts to 1 microM RA down-regulated Mn-SOD mRNA, and also decreased Mn-SOD activity by approximately 80% with no change in Mn-SOD protein levels. In contrast, Cu,Zn-SOD protein and enzymatic activity were modestly reduced by RA treatment in both normal and psoriatic fibroblasts. Furthermore, RA treatment of psoriatic fibroblasts also caused a decrease in Cu,Zn-SOD steady-state mRNA levels. These results indicate that RA can serve as a regulatory agent to down-regulate the steady-state levels of both Mn-SOD and Cu,Zn-SOD in psoriatic cells. These findings offer a new model for the antiinflammatory activity of RA when used in the treatment of psoriasis.

Human embryonic implantation involves major invasion of the uterine wall and remodeling of the uterine arteries by extravillous cytotrophoblast cells (EVCT). Abnormalities in these early steps of placental development lead to poor placentation and fetal growth defects and are frequently associated with preeclampsia, a major complication of human pregnancy. We recently showed that oxidized low-density lipoproteins (oxLDLs) are present in situ in EVCT and inhibit cell invasion in a concentration-dependent manner. The aim of the present study was to better understand the mechanisms by which oxLDL modulate trophoblast invasion. We therefore investigated the presence of oxLDL receptors in our cell culture model of human invasive primary EVCT. We found using immunocytochemistry and immunoblotting that the lectin-like oxLDL receptor-1 was the scavenger receptor mainly expressed in EVCT and was probably involved in oxLDL uptake. We next examined the effect of low-density lipoprotein oxidative state on trophoblast invasion in vitro using EVCT cultured on Matrigel-coated Transwell. We demonstrated that only oxLDL containing a high proportion of oxysterols and phosphatidylcholine hydroperoxide derivatives that provide ligands for liver X receptor (LXR) and peroxisomal proliferator-activated receptor γ (PPARγ), respectively, reduced trophoblast invasion. We next investigated the presence and the role of these nuclear receptors and found that in addition to PPARγ, human invasive trophoblasts express LXRβ, and activation of these nuclear receptors by specific synthetic or natural ligands inhibited trophoblast invasion. Finally, using a PPARγ antagonist, we suggest that LXRβ, rather than PPARγ, is involved in oxLDL-mediated inhibition of human trophoblast invasion in vitro.

Human implantation involves a major invasion of the uterine wall and remodeling of the uterine arteries by trophoblastic cells. Abnormalities in these early steps of placental development lead to poor placentation, fetal growth defects and are frequently associated with pre-eclampsia, a serious disease specific to human pregnancy. Lipid metabolism is altered during human pregnancy, with low-density lipoproteins (LDL) becoming more susceptible to oxidation. The aim of this study was to localize oxidized LDL (oxLDL) at the implantation site and to investigate the role of oxLDL in human trophoblast invasion in vitro. We showed by immunohistochemistry that oxLDL was present in cytotrophoblasts of villous and extravillous origin in sections of first trimester human placenta. We purified primary invasive extravillous cytotrophoblasts isolated from the chorionic villi of human first trimester placenta and cultured them on Matrigel-coated transwells. We demonstrated using this invasion assay that oxLDL, but not native LDL, inhibited cell invasion in a concentration-dependent manner. These results suggest that human trophoblast invasion may be modulated by oxLDL in vivo and provide new insights into the pathophysiology of pre-eclampsia associated with oxidative stress and defective trophoblast invasion.

Total human chorionic gonadotropin (hCG) is high in maternal serum at 14-18 wk of trisomy 21 (T21)-affected pregnancy, despite low placental hCG synthesis. We sought an explanation for this paradox. We first observed that, in T21-affected pregnancies, maternal serum hCG levels peaked at around 10 wk and then followed the same pattern throughout pregnancy as in controls, albeit at a higher (2.2-fold) level. After delivery, hCG clearance was not significantly different from that in controls. We isolated cytotrophoblasts from 29 T21-affected placentas (12-25 wk) and 13 gestational age-matched control placentas and cultured them for 3 d. In this large series, we confirmed that, in the culture medium of trophoblasts isolated from T21 placentas, hCG secretion was significantly lower (P < 0.003) than in controls, in contrast to the high hCG in maternal serum of the same patients. In T21 cultured trophoblasts, transcripts of sialyltransferase-1 and fucosyltransferase-1 were abnormally high. In corresponding culture medium, hCG was abnormally glycosylated; highly acidic [isoelectric points (pHi) = 4.5] as shown by isoelectric focusing, immunoblotting, and lectin binding; and weakly bioactive (46% of control) as determined using the Leydig cell model. In conclusion, T21 trophoblast cells produced hCG that was weakly bioactive and abnormally glycosylated but whose maternal clearance was unaltered.

The syncytiotrophoblast is the principal component of the human placenta involved in feto-maternal exchanges and hormone secretion. The syncytiotrophoblast arises from the fusion of villous cytotrophoblasts. We recently showed that functional gap junctional intercellular communication(GJIC) is an important prerequisite for syncytiotrophoblast formation and that connexin 43 (Cx43) is present in cytotrophoblasts and in the syncytiotrophoblast. To determine whether Cx43 is directly involved in trophoblast fusion, we used an antisense strategy in primary cultures of human villous cytotrophoblasts that spontaneously differentiate into the syncytiotrophoblast by cell fusion. We assessed the morphological and functional differentiation of trophoblasts by desmoplakin immunostaining, by quantifying hCG (human chorionic gonadotropin) production and by measuring the expression of specific trophoblast genes (hCG and HERV-W). Furthermore, we used the gap-FRAP (fluorescence recovery after photobleaching) method to investigate functional GJIC. Cytotrophoblasts treated with Cx43 antisense aggregated and fused poorly. Furthermore, less HERV-W env mRNA, hCGβ mRNA and hCG secretion were detected in Cx43 antisense-treated cytotrophoblasts than in cells treated with scrambled antisense. Treatment with Cx43 antisense dramatically reduced the percentage of coupled trophoblast cells. Taken together, these results suggest that Cx43 is directly involved in human trophoblast cell-cell communication, fusion and differentiation.

The placenta is a unique, autonomous and transient organ. It ensures maternal-fetal exchanges and is also involved in maternal tolerance of feto-paternal antigens. The human placenta is characterized by the major invasion of the trophoblast, which comes in contact with the maternal blood, and by the intensity and the specificity of its endocrine functions. Placental hormones are required for the establishment and maintenance of pregnancy, adaptation of the maternal organism to pregnancy, fetal growth and well being, and development of the mechanisms involved in parturition. The endocrine tissue of the placenta is the syncytiotrophoblast, which covers the chorionic villi, and arises from the fusion of the cytotrophoblasts. In this review we will summarize the particulars of human syncytiotrophoblast development and endocrine functions.

Trophoblast differentiation is a key event in human placental development. During extravillous trophoblast (EVT) differentiation, stem cells from the anchoring villi detach from their basement membrane and proliferate to form aggregates called trophoblast cell columns (TCCs). They subsequently invade the decidua and differentiate into interstitial and endovascular trophoblasts. The influence of the decidua on EVT differentiation is controversial. We therefore compared the pattern of trophoblast differentiation marker expression in viable intrauterine and tubal pregnancies, as decidual cell markers (prolactin [PRL] and insulin-like growth factor binding Protein-1 [IGFBP1]) were only expressed in endometrial implantation sites. Extravillous trophoblast differentiation in anchoring villi from uterine and ectopic pregnancies exhibited a comparable phenotypical switch: α6 integrin subunit, E-cadherin, EGF receptor, Ki 67 and connexin 40 were localized in the proximal part of the TCC, while α5βl and αl integrins, c-erb B2, hPL and HLA-G were expressed by invasive cytotrophoblasts. The cyclin-dependent kinase inhibitors pl6 and p57 were mainly detected in invasive cytotrophoblasts some distance from the columns. However, the TCC was markedly longer in tubal pregnancy than in intrauterine pregnancy. These findings suggest that the decidua is not necessary to trigger EVT invasion, but that it is likely to limit the extent of the TCC and to accelerate the onset of EVT migration.

We recently demonstrated that the product of the HERV-W env gene, a retroviral envelope protein also dubbed syncytin, is a highly fusogenic membrane glycoprotein inducing the formation of syncytia on interaction with the type D mammalian retrovirus receptor. In addition, the detection of HERV-W Env protein (Env-W) expression in placental tissue sections led us to propose a role for this fusogenic glycoprotein in placenta formation. To evaluate this hypothesis, we analyzed the involvement of Env-W in the differentiation of primary cultures of human villous cytotrophoblasts that spontaneously differentiate by cell fusion into syncytiotrophoblasts in vitro. First, we observed that HERV-W env mRNA and glycoprotein expression are colinear with primary cytotrophoblast differentiation and with expression of human chorionic gonadotropin (hCG), a marker of syncytiotrophoblast formation. Second, we observed that in vitro stimulation of trophoblast cell fusion and differentiation by cyclic AMP is also associated with a concomitant increase in HERV-W env and hCG mRNA and protein expression. Finally, by using specific antisense oligonucleotides, we demonstrated that inhibition of Env-W protein expression leads to a decrease of trophoblast fusion and differentiation, with the secretion of hCG in culture medium of antisense oligonucleotide-treated cells being decreased by fivefold. Taken together, these results strongly support a direct role for Env-W in human trophoblast cell fusion and differentiation.

The human insulin-family genes regulate cell growth, metabolism, and tissue-specific functions. Among these different members, only INSL4 gene shows a predominant placenta-specific expression. Here, we show that the human INSL4 gene is tightly clustered with three other members of the human insulin superfamily (RLN1, RLN2, and INSL6) within a 176-kilobase genomic segment on chromosome region 9p23.3‐p24.1. We also report evidence that INSL4 is probably the only insulin-like growth factor gene to be primate-specific. We identified an unexpected human endogenous retrovirus (HERV) element inserted into the human INSL4 promoter with a sequence similar to that of env gene, flanked by two long terminal repeats(LTRs). The emergence of INSL4 gene and genomic insertion of HERV appear to have occurred after the divergence of New World and Old World monkeys (;45 million years ago). Transient transfection experiments showed that the placenta-specific expression of INSL4 is mediated by the 39 LTR of the HERV element, and that the latter may have a major role in INSL4 up-regulation during human cytotrophoblast differentiation into syncytiotrophoblast. Finally, we identified an INSL4 alternatively spliced mRNA species that encodes putative novel INSL4-like peptides. These data support the view that ancient retroviral infection may have been a major event in primate evolution, especially in the functional evolution of the human placenta. gene regulation, insulin, placenta, pregnancy, relaxin

The human placenta is characterized by extensive trophoblast invasion of the uterus. Indeed, extravillous cytotrophoblast cells invade the decidua and the upper third of uterine spiral arteries in the myometrium. This invasion is reflected in situ by the expression of specific markers. In order to study this invasion process, we have established an in vitro culture model of human extravillous trophoblast isolated from first trimester chorionic villi. The aim of this study was to investigate the effect of a composite matrix, the Matrigel required for the culture of this homogenous population of extravillous trophoblasts (EVCT), on their in vitro differentiation. The effect of Matrigel was studied on different markers characterized by immunocytochemistry and by real-time polymerase chain reaction assay of transcripts. In addition, the expression of 12 different matrix metalloproteases and their inhibitors were investigated. We show that human extravillous cytotrophoblasts acquire an invasive phenotype on Matrigel associated with a specific pattern of protease gene expression. This in vitro model will be of interest to study the cellular mechanisms involved in abnormal trophoblast invasion observed in poor placentation and preeclampsia.

PPAR-gamma/RXR heterodimers play a key regulatory role in murine placental development. We report here that PPAR-gamma and RXR-alpha are highly expressed in cultured primary extravillous cytotrophoblasts (EVCT) isolated from human first-trimester placenta. Using this cell culture model, we showed that PPAR-gamma agonists inhibit EVCT invasion, whereas PPAR-gamma or pan-RXR antagonists promoted EVCT invasion by themselves and abolished PPAR-gamma agonist-mediated effect. Together these data underscore an important function of PPAR/RXR heterodimers in the modulation of trophoblast invasion.

Placental growth hormone (PGH) is the product of the GH-V gene, predominantly expressed in the syncytiotrophoblast layer of the human placenta. PGH differs from pituitary growth hormone by 13 amino acids and possesses one glycosylation site. It has high somatogenic and low lactogenic activities. In the maternal circulation from 12-20 weeks up to term, PGH gradually replaces pituitary growth hormone, which becomes undetectable. PGH is secreted by the placenta in a non-pulsatile manner. This continuous secretion appears to have important implications for physiological adjustment to gestation and especially in the control of maternal IGF1 levels. PGH secretion is regulated in vitro and in vivo by glucose. Lower maternal levels of PGH are observed in pregnancies with fetal growth retardation. PGH is one example of a trophoblast hormone, which allows maternal metabolic adaptation to pregnancy. In addition, our recent data on its expression in invasive extravillous trophoblasts suggest that the physiological role of PGH might also include a direct influence of this hormone on placental development via an autocrine or paracrine mechanism.

RESUME La preeclampsie est une complication majeure de la grossesse. Son diagnostic est clinique au deuxieme trimestre de la grossesse; il est caracterise par l’association d’une hypertension arterielle et d’une proteinurie. L’etiologie de la preeclampsie est d’origine placentaire. Le primum movens de cette maladie specifique a l’espece humaine est un defaut deplacentation, caracterise par une invasion insuffisante du trophoblaste uterin, et notamment de la paroi des arteres spiralees uterines. Dans cette etude, nous avons developpe un modele de culture des cellules trophoblastiques humaines impliquees dans l’implantation (cellules trophoblastiques extravilleuses) et teste in vitro leur propriete de cellules invasives. Nous revelons pour la premiere fois qu’un gene directement implique dans le developpement placentaire, le PPARγ est un acteur potentiel de la pathogenie de la preeclampsie. En effet, l'activation de ce recepteur nucleaire par des ligands naturels inhibe l’invasion de la cellule trophoblastique humaine. Or, les ligands naturels de ce recepteur semblent presents a l’interface fœto-maternelle.

International audience; Cell fusion occurs as part of the differentiation of some cell types, including myotubes in muscle and osteoclasts in remodeling bone. In the human placenta, mononuclear cytotrophoblasts in a human chorionic gonadotropin (hCG)-driven process fuse to form multinucleated syncytia that allow the exchange of nutrients and gases between the maternal and fetal circulation. Experiments in which protein kinase A (PKA) is displaced from A-kinase anchoring proteins (AKAPs), or in which specific AKAPs are depleted by siRNA-mediated knockdown, point to ezrin as a scaffold required for hCG-, cAMP-and PKA-mediated regulation of the fusion process. By a variety of immunoprecipitation and immunolocalization experiments, we show that ezrin directs PKA to a molecular complex of connexin 43 (Cx43, also known as GJA1) and zona occludens-1 (ZO-1, also known as TJP1). A combination of knockdown experiments and reconstitution with ezrin or Cx43 with or without the ability to bind to its interaction partner or to PKA demonstrate that ezrin-mediated coordination of the localization of PKA and Cx43 is necessary for discrete control of Cx43 phosphorylation and hCG-stimulated gap junction communication that triggers cell fusion in cytotrophoblasts.

While acting upon chromatin compaction, histone post-translational modifications (PTMs) are involved in modulating gene expression through histone–DNA affinity and protein–protein interactions. These dynamic and environment-sensitive modifications are constitutive of the histone code that reflects the transient transcriptional state of the chromatin. Here we describe a global screening approach for revealing epigenetic disruption at the histone level. This original approach enables fast and reliable relative abundance comparison of histone PTMs and variants in human cells within a single LC-MS experiment. As a proof of concept, we exposed BeWo human choriocarcinoma cells to sodium butyrate (SB), a universal histone deacetylase (HDAC) inhibitor. Histone acid-extracts (n = 45) equally representing 3 distinct classes, Control, 1 mM and 2.5 mM SB, were analysed using ultra-performance liquid chromatography coupled with a hybrid quadrupole time-of-flight mass spectrometer (UPLC-QTOF-MS). Multivariate statistics allowed us to discriminate control from treated samples based on differences in their mass spectral profiles. Several acetylated and methylated forms of core histones emerged as markers of sodium butyrate treatment. Indeed, this untargeted histonomic approach could be a useful exploratory tool in many cases of xenobiotic exposure when histone code disruption is suspected.

The ligand-dependent nuclear receptors PPARγ and RXRα/β were recently determined to be essential for murine placental development and trophoblast differentiation. In the current study we examined the expression and role of the PPARγ/RXRα heterodimers in human invasive trophoblasts. We first report that in human first trimester placenta, PPARγ and RXRα are highly expressed in cytotrophoblasts at the feto-maternal interface, especially in the extravillous cytotrophoblasts involved in uterus invasion. The coexpression of PPARγ and RXRα genes in extravillous cytotrophoblast nuclei were then confirmed by immunocytochemistry, immunoblot, and real-time quantitative PCR using cultured purified primary extravillous cytotrophoblasts. We next examined, using the extravillous cytotrophoblast culture model, the biological role of PPARγ/RXRα heterodimers in vitro, and we showed that both synthetic (rosiglitazone) and natural [15-deoxy-δ-(12,14)PGJ2] PPARγ agonists inhibit extravillous cytotrophoblast invasion in a conc...

Recent studies performed with null mice suggested a role of either RXRα or PPARγ in murine placental development. We report here that both PPARγ and RXRα are strongly expressed in human villous cytotrophoblasts and syncytiotrophoblasts. Moreover, specific ligands for RXRs or PPARγ (but not for PPARα or PPARδ) increase both human CGβ transcript levels and the secretion of human CG and its free β-subunit. When combined, these ligands have an additive effect on human CG secretion. Pan-RXR and PPARγ ligands also have an additive effect on the synthesis of other syncytiotrophoblast hormones such as human placental lactogen, human placental GH, and leptin. Therefore, in human placenta, PPARγ/RXRα heterodimers are functional units during cytotrophoblast differentiation into the syncytiotrophoblast in vitro. Elements located in the regulatory region of the human CGβ gene (β5) were found to bind RXRα and PPARγ from human cytotrophoblast nuclear extracts, suggesting that PPARγ/RXRα heterodimers directly regulate human CGβ transcription. Altogether, these data show that PPARγ/RXRα heterodimers play an important role in human placental development.

The syncytiotrophoblast (ST) is one of the major components of the human placenta, as it is involved in feto-maternal exchanges and the secretion of pregnancy-specific hormones. The aim of this study was to elucidate the formation and function of the ST in trisomy 21 (Down's syndrome). We first used the in vitro model of cytotrophoblast differentiation into ST. Cytotrophoblasts were isolated from 15 trisomy 21-affected placentas (12-35 weeks gestation) and 10 gestational age-matched control placentas. In vitro cytotrophoblasts isolated from normal placenta fused to form the ST. This was associated with an increase in transcript levels and in the secretion of hCG, human placental lactogen, placental GH, and leptin. In trisomy 21-affected placentas, we observed a defect (or a delay) in ST formation and a dramatic decrease in the synthesis and secretion of these hormones compared to those in cultured cells isolated from control age-matched placentas. These results were confirmed by a significant (P < 0.001) decrease in gene expression in total homogenates of trisomy 21-affected placentas compared to controls. These results will be of help in understanding the maternal hormonal markers of fetal trisomy 21 and the consequences of placental defects for fetal development.

Differences in oxidative damage, as measured by an increase in the carbonylation of macromolecules, were determined in situ with skin biopsies from psoriatic patients and controls. High levels of carbonyl residues were consistently detected in the dermis and never in the epidermis of sections of these skin biopsy samples. The dermis of psoriatic skin without lesions had a higher level of carbonylation than the dermis of normal skin. In this study, we found that there was more oxidative damage in cultured fibroblasts prepared from skin with and without lesions from psoriasis patients than in normal fibroblasts from the skin of age-matched controls. The extent of protein carbonylation in cell extracts was determined by immunoblotting, using an antidinitrophenylhydrazone antibody, and in intact cells was determined by immunocytochemical analysis with the same antibody. The higher level of carbonylation detected was used here as a measure of oxidative stress, and showed that some oxidative damage occurred before the appearance of typical psoriatic plaques. These results suggest that fibroblasts are affected before the onset of psoriasis and that this damage is independent of any inflammatory infiltrate.

Retinoic acid (RA) is an important mediator of cell differentiation. It stimulates hCG secretion by JEG-3 choriocarcinoma cells in vitro after a time lag. The first aim of this study was to characterize which types of retinoid receptors (RARs and RXRs) are present in JEG-3 cells. Using Western blot analysis and immunocytochemistry with specific antibodies as well as Northern blot analysis, we found that JEG-3 cells expressed RAR alpha and RXR alpha, the latter being the predominant receptor. We then analyzed the action on cell proliferation and hCG secretion of the physiological retinoids all-trans RA (RA) and 9 cis RA as well as synthetic retinoids with specific affinity for RAR alpha and RXR alpha. All these retinoids were potent inhibitors of cell growth, maximal inhibition (72 +/- 2%) being observed after 4 days of treatment with Ro 25, a RXR alpha specific ligand. Within 24 h, 9 cis RA and Ro 25 stimulated hCG secretion, and maximal stimulation (1,472 +/- 10%) occurred at 48 h with the RXR alpha-specific ligand. The RAR alpha-specific ligand also stimulated hCG secretion but to a lower extend and after a delay of 48 h. These results suggest a predominant role of RXR alpha in mediating the biological effects of retinoids on JEG-3 cells and the possible induction by RA itself of the metabolic pathway leading to 9 cis RA.

Placental growth hormone (PGH) is the product of the GH-V gene specifically expressed in the syncytiotrophoblast layer of the human placenta. PGH differs from pituitary growth hormone by 13 amino acids. It has high somatogenic and low lactogenic activities. Assays of PGH by specific monoclonal antibodies reveal that in the maternal circulation from 15-20 weeks up to term, PGH gradually replaces pituitary growth hormone which becomes undetectable. It is secreted by the placenta in a non-pulsatile manner. This continuous secretion appears to have important implications for physiological adjustment to gestation and especially in the control of maternal IGF1 levels. PGH secretion is inhibited by glucose in vitro and in vivo, and is significantly decreased in the maternal circulation in cases of pregnancies with intrauterine growth retardation. PGH does not appear to have a direct effect on fetal growth, as this hormone is not detectable in the fetal circulation. However the physiological role of PGH might also include a direct influence on placental development via an autocrine or paracrine mechanism as suggested by the presence of specific GH receptors in this tissue.

To investigate the role of retinoids on human placental development and functions, we characterized the spatial distribution of retinoid receptors in human term chorionic villi. In situ hybridization with 35S labeled sense and antisense probes for the RARs, alpha, beta, gamma and RXRs, alpha, beta, gamma, specifically detected only RAR alpha and RXR alpha. Both RAR alpha and RXR alpha mRNA were preferentially expressed in the trophoblast cell layer. This syncytiotrophoblast expression was confirmed by immunohistochemical analyses using anti-RAR alpha and RXR alpha antibodies. Using trophoblast cells in culture, we then studied the effect on hCG secretion of 0.1 microM RA physiological forms and of selective RAR alpha and RXR alpha synthetic agonists. Only RXR alpha specific ligands such as physiological 9-cis RA and synthetic Ro 25-7386 stimulated hCG secretion (doubled). These results suggest an important role for RXR alpha in human placental development and function.