Biomedical subjects

D Evain-Brion

Publications and source records attributed to D Evain-Brion.

At least 19 recordsLinked to original sources

PubMed2006

PPARs and the placenta.

The discovery of the peroxisome proliferator-activated receptors (PPARs) in 1990s provided new insights in understanding the mechanisms involved in the control of energy homeostasis and in cell differentiation, proliferation, apoptosis and the inflammatory process. The PPARs became thus an exciting therapeutic target for diabetes, metabolic syndrome, atherosclerosis, and cancer. Unexpectedly, genetic studies performed in mice established that PPARgamma are essential for placental development. After a brief description of structural and functional features of PPARs, we will summarize in this review the most recent results concerning expression and the role of PPARs in placenta and of PPARgamma in human trophoblastic cells in particular.

Animals↗

PubMed2006

Expression of the fusogenic HERV-FRD Env glycoprotein (syncytin 2) in human placenta is restricted to villous cytotrophoblastic cells.

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.

Cells, Cultured↗

PubMed2006

Human chorionic gonadotropin expression in human trophoblasts from early placenta: comparative study between villous and extravillous trophoblastic cells.

Human trophoblast differentiates into two pathways: extravillous cytotrophoblasts (EVCT) that invade the uterus wall and villous cytotrophoblasts (VCT) that fuse to form the syncytiotrophoblast (ST) involved in placental exchanges and endocrine function. It is established that hCG is produced and secreted by the ST into the maternal compartment where it plays a key endocrine role and stimulates ST formation in an autocrine manner. Herein, we investigated hCG expression in early placentas by immunohistochemistry using different antibodies. We then compared hCG secretion by primary cultures of VCT and EVCT isolated from the same first trimester human chorionic villi. In situ hCG was immunodetected in EVCT all along their invasive differentiating pathway except in cells near the stromal core of the proximal column. hCG expression was confirmed in vitro by immunocytochemistry and hCG secretion quantified in cell supernatants. Interestingly, whereas hCG secretion increased during VCT differentiation into ST (from 60 to 350UI/L/microg DNA), EVCT secretion remained constant and at a high level during the same culture period (160UI/L/microg DNA). Our data demonstrated that in addition to the ST, invasive EVCT also expressed and secreted high levels of hCG, suggesting a specific paracrine and/or autocrine role for hCG from EVCT origin.

Animals↗

PubMed2006

Modulation of PAPP-A expression by PPARgamma in human first trimester trophoblast.

Pregnancy-associated plasma protein-A (PAPP-A) is a metzincin metalloproteinase that cleaves the insulin-like growth factor (IGF)-dependent binding protein-4 and increases in maternal serum during pregnancy. In human placenta PAPP-A is expressed both in villous cytotrophoblasts (VCT) that cover the chorionic villi and in extravillous cytotrophoblasts (EVCT) of the anchoring villi. Due to the key role of PPARgamma in human trophoblast differentiation such as syncytiotrophoblast formation and EVCT invasion, we studied the effect of PPARgamma activation on PAPP-A expression using our in vitro model of EVCT and VCT primary cultures isolated from the same first trimester chorionic villi. First, we demonstrated that invasive EVCT expressed and secreted 10 times more PAPP-A than VCT did. Then, we showed that activation of PPARgamma inhibited PAPP-A gene expression and secretion in EVCT, whereas it had no effect in VCT. Since we have previously shown that PPARgamma agonist inhibits EVCT invasion in vitro, we suggest that PPARgamma-mediated inhibition of PAPP-A might decrease the amount of bioactive IGFII, a factor known to promote trophoblast invasion.

Chorionic Villi↗

PubMed2005

Expression of HERV-W Env glycoprotein (syncytin) in the extravillous trophoblast of first trimester human placenta.

Although the extravillous trophoblastic invasion has a critical role in human placental development, nothing is known about HERV-W expression in the extravillous phenotype. The aim of the present study was to localize in first trimester placenta the expression of HERV-W Env glycoprotein and its receptor all along the differentiation pathway of the extravillous phenotype. In addition using an in vitro model of extravillous cytotrophoblastic cell isolation and invasion we investigated the presence of HERV-W transcripts and envelope glycoprotein in cultured extravillous trophoblastic cells. Using monoclonal and polyclonal antibodies, the glycoprotein was immunolocalized in all the cell types of the extravillous phenotype lineage: cytotrophoblastic cells of the column, interstitial extravillous trophoblastic cells, multinucleated giant cells and endovascular trophoblast. Furthermore, using a polyclonal antibody, the D mammalian virus receptor was also localized in the various extravillous trophoblastic phenotypes. In addition, the presence of HERV-W transcripts and protein was demonstrated in cultured extravillous trophoblastic cells. HERV-W Env glycoprotein expressed in villous and extravillous trophoblast can be considered as a specific marker of the human trophoblast.

Adult↗

PubMed2004

Large variability of trophoblast gene expression within and between human normal term placentae.

Human placenta extracts are widely used in clinical and fundamental research, particularly to study the hormonal and exchange functions of the placenta. However, very little is known about the distribution of the main hormone mRNAs in the placenta as a whole. Total placenta extracts are heterogeneous in their cellular components, as they contain material of both fetal and maternal origin, and in their structure. Results vary greatly depending upon the location of the biopsy and the number of biopsies performed. We used real-time quantitative RT-PCR to determine whether transcripts corresponding to the main hormones secreted by the human placenta (e.g. hCG, HPL and PGH) are equally distributed within and between term placentae. We also measured cytokeratin 7 transcripts, which are specifically expressed in the trophoblast, and transcripts corresponding to nuclear receptors PPARgamma and RXRalpha. A comparison of the results obtained with 12 different samples from each of four normal term placentae revealed that the amounts of transcripts differ considerably within and between each placenta. This emphasizes the need to study large numbers of samples when looking for significant differences in gene expression.

Analysis of Variance↗

PubMed2004

Impact of trisomy 21 on human trophoblast behaviour and hormonal function.

Although trisomy 21 (T21) is the most frequent genetic abnormality and some maternal serum markers for this fetoplacental aneuploidy are of placental origin, little is known of its impact on placental development. We therefore studied the influence of T21 on trophoblast behaviour. Using cultured cells from 46 human T21 pregnancies, we confirmed the defective morphological and functional differentiation of the villous cytotrophoblast in this setting; indeed, villous cytotrophoblast cells aggregate normally but fuse inefficiently to form the syncytiotrophoblast. This is in part related to the abnormal oxidative status of the T21 cytotrophoblast, characterized by a gene dosage-related increase in SOD-1 (copper-zinc superoxide dismutase) expression and activity. This was associated with a significant (P < 0.01) increase in catalase activity but no significant change in glutathione peroxidase activity. On the basis of these in vitro findings and studies of large panels of maternal serum, we propose a pathophysiological explanation for trisomy 21 maternal serum markers of placental origin.

Adult↗

PubMed2004

Trophoblast production of a weakly bioactive human chorionic gonadotropin in trisomy 21-affected pregnancy.

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.

Antigens, CD↗

PubMed2003

Evidence of a limited contribution of feto-maternal interactions to trophoblast differentiation along the invasive pathway.

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: alpha6 integrin subunit, E-cadherin, EGF receptor, Ki 67 and connexin 40 were localized in the proximal part of the TCC, while alpha5beta1 and alpha1 integrins, c-erb B2, hPL and HLA-G were expressed by invasive cytotrophoblasts. The cyclin-dependent kinase inhibitors p16 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.

Biomarkers↗

PubMed2003

Expression of pregnancy-associated plasma protein-A (PAPP-A) during human villous trophoblast differentiation in vitro.

Pregnancy-associated placental protein-A (PAPP-A), first isolated from maternal serum, has been identified as a metalloprotease cleaving insulin-like growth factor binding protein-4 (IGFBP-4). The source of PAPP-A during pregnancy is unclear. We therefore investigated PAPP-A expression during in vitro human villous cytotrophoblast cell (CT) differentiation into syncytiotrophoblast (ST). CT were isolated from normal first trimester, second trimester and term placentae (n=10) and cultured to form ST. PAPP-A mRNA was quantified by real-time PCR, and PAPP-A protein expression was studied by immunocytochemistry and TRACE technology with specific monoclonal antibodies. PAPP-A mRNA expression in total placental extracts increased during the course of pregnancy. PAPP-A protein was detected in the cytoplasm of both CT and ST. ST formation in vitro was associated with a 19-fold increase in PAPP-A mRNA expression and an 8-fold increase in PAPP-A secretion into the culture medium. No significant difference in PAPP-A production was observed between cultured cells isolated from early and term placentae. In conclusion, PAPP-A production in vitro, is associated to the differentiation of villous cytotrophoblast cells into syncytiotrophoblast, independently of the age of gestation.

Adult↗

PubMed2002

Human placental growth hormone--a review.

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.

Adult↗

PubMed2001

Post-translational modifications of the regulatory subunits of cAMP-dependent protein kinases during G1/S progression.

During the G1/S transition of the cell cycle variations in the labelling by 8-N3-[32P]cAMP of the protein kinase A regulatory subunits RI and RII, used as a probe to monitor post-translational modifications that may regulate cAMP binding, were observed in synchronized HeLa cells. A decrease in 8-N3-[32P]cAMP labelling of RI, RII and RII phosphorylated by the catalytic subunit of PKA was correlated with the increased percentage of cells in phases G1. An increase in 8-N3-[32P]cAMP incorporated into the 54-kDa RII subunit during progression from G1 to S was correlated with an increase in intracellular cAMP. A transient increase in Mn-SOD activity was detected in cells arrested at the G1/S transition using two different techniques, suggesting that oxidative modulation of regulatory subunits by free radicals may modify cAMP binding sites during the cell cycle. Decreased photoaffinity labelling by 8-N3-[32P]cAMP of RI, RII and autophosphorylated RII subunits was found to be an inherent characteristic of PKA in the G1/S transition.

Azides↗

PubMed2001

Characterization of human villous and extravillous trophoblasts isolated from first trimester placenta.

Trophoblasts of the human placenta differentiate along two pathways to give either extravillous cytotrophoblasts (EVCT) with invasive properties and that are implicated in the implantation process, or villous cytotrophoblasts (VCT) that by cell fusion form multinucleated syncytiotrophoblasts. We report the first isolation and purification of these two cell types from the same chorionic villi of first trimester human placenta. We also studied their differentiation in vitro. Electron microscopy showed that in contrast to VCT, EVCT had no microvilli but contained large fibrinoid inclusions. EVCT cultures required a matrix to invade, and as previously established, VCT cultured on plastic dishes aggregated and fused to form syncytiotrophoblasts. These differentiation processes were characterized by a particular pattern of gene expression as assessed by real-time PCR and confirmed by immunocytochemical analysis of the corresponding proteins. EVCT cultured in vitro expressed high levels of HLA-G, c-erbB2, human placental lactogen, and very little human chorionic gonadotropin. Interestingly, TGFbeta2 was a marker of EVCT in vitro and in situ. These data offer a new tool for cell biologists to study the molecular mechanisms involved in human placental development and its pathology.

Cell Differentiation↗

PubMed2001

Defect of syncytiotrophoblast formation and human chorionic gonadotropin expression in Down's syndrome.

The syncytiotrophoblast (ST) is a major component of the human placenta as it is involved in feto-maternal exchanges and the secretion of pregnancy-specific hormones. We have studied the formation and function of the ST in normal and trisomy 21 (T21)-affected placenta using the in vitro model of cytotrophoblast differentiation into ST. Cytotrophoblast cells were isolated from first trimester, second trimester and term placentae. In vitro cytotrophoblast cells isolated from normal placenta fused to form the ST. This was associated with an increase in the transcript levels and the secretion of human chorionic gonadotropin (hCG). However, the secretion of hCG decreased through pregnancy. In T21-affected placentae, we observed a defect (or a delay) in ST formation and a dramatic decrease in the synthesis and secretion of this hormone compared with cultured cells isolated from control age-matched placentae. These results were confirmed by a significant (P < 0.05) decrease in transcript levels of alpha and beta subunits of hCG in total homogenates of T21-affected placentae compared with controls. These results suggest a decrease in functional mass of ST in T21 placenta, and therefore a decrease in production of placental pregnancy-specific polypeptide hormones.

Adult↗

PubMed2001

The molecular basis of embryo implantation in humans.

The implantation of the human embryo is a double paradox, immunological and biological. The immunological paradox is that it consists of a heterologous graft in which the uterine immune system (via the cytokines) and the embryo's antigenicity (HLAG) collaborate to make possible both implantation and the maintenance of the pregnancy. The biological paradox arises because several different mechanisms must be successively implemented for these two epithelia to fuse and then for one to allow invasion by the other (that is, the for the endometrium to be decidualized by the trophoblast): preparation of the endometrium throughout the menstrual cycle under the influence of estrogens and then progesterone, with the involvement of growth factors (EGF, TGF and IGF), neoangiogenesis (estradiol, FGF and VEGF), recognition by the trophoblastic cells of the various components of the decidua and of the extracellular matrix (integrins and cadherin) and the progressive invasion of the decidua, to the depth of the spiral arteries (by the trophoblastic secretion of metalloproteases). A defective or excessive trophoblastic invasion can result in complications of pregnancy: early spontaneous miscarriage, preeclampsia and growth retardation of vascular origin in the case of defects, placenta accreta or percreta in the case of excess.

Animals↗

PubMed2001

PPAR gamma/RXR alpha heterodimers are involved in human CG beta synthesis and human trophoblast differentiation.

Recent studies performed with null mice suggested a role of either RXR alpha or PPAR gamma in murine placental development. We report here that both PPAR gamma and RXR alpha are strongly expressed in human villous cytotrophoblasts and syncytiotrophoblasts. Moreover, specific ligands for RXRs or PPAR gamma (but not for PPAR alpha or PPAR delta) increase both human CG beta transcript levels and the secretion of human CG and its free beta-subunit. When combined, these ligands have an additive effect on human CG secretion. Pan-RXR and PPAR gamma 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, PPAR gamma/RXR alpha heterodimers are functional units during cytotrophoblast differentiation into the syncytiotrophoblast in vitro. Elements located in the regulatory region of the human CG beta gene (beta 5) were found to bind RXR alpha and PPAR gamma from human cytotrophoblast nuclear extracts, suggesting that PPAR gamma/RXR alpha heterodimers directly regulate human CG beta transcription. Altogether, these data show that PPAR gamma/RXR alpha heterodimers play an important role in human placental development.

Cell Differentiation↗

PubMed2001

Overexpression of copper zinc superoxide dismutase impairs human trophoblast cell fusion and differentiation.

The syncytiotrophoblast is the major component of the human placenta, involved in feto-maternal exchanges and secretion of pregnancy-specific hormones. Multinucleated syncytiotrophoblast arises from fusion of mononuclear cytotrophoblast cells. In trisomy 21-affected placentas, we recently have shown that there is a defect in syncytiotrophoblast formation and a decrease in the production of pregnancy-specific hormones. Due to the role of oxygen free radicals in trophoblast cell differentiation, we investigated the role of the key antioxidant enzyme, copper/zinc superoxide dismutase, encoded by chromosome 21 in in vitro trophoblast differentiation. We first observed that overexpression of superoxide dismutase in normal cytotrophoblasts impaired syncytiotrophoblast formation. This was associated with a significant decrease in mRNA transcript levels and secretion of hCG and other hormonal markers of syncytiotrophoblast. We confirmed abnormal cell fusion by overexpression of green fluorescence protein-tagged superoxide dismutase in cytotrophoblasts. In addition, a significant decrease in syncytin transcript levels was observed in superoxide dismutase-transfected cells. We then examined superoxide dismutase expression and activity in isolated trophoblast cells from trisomy 21-affected placentas. Superoxide dismutase mRNA expression (P < 0.05), protein levels (P < 0.01), and activity (P < 0.05) were significantly higher in trophoblast cells isolated from trisomy 21-affected placentas than in those from normal placentas. These results suggest that superoxide dismutase overexpression may directly impair trophoblast cell differentiation and fusion, and superoxide dismutase overexpression in Down's syndrome may be responsible at least in part for the failure of syncytiotrophoblast formation observed in trisomy 21-affected placentas.

Cell Differentiation↗

PubMed2001

PPARgamma/RXRalpha heterodimers control human trophoblast invasion.

The ligand-dependent nuclear receptors PPARgamma and RXRalpha/beta 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 PPARgamma/RXRalpha heterodimers in human invasive trophoblasts. We first report that in human first trimester placenta, PPARgamma and RXRalpha are highly expressed in cytotrophoblasts at the feto-maternal interface, especially in the extravillous cytotrophoblasts involved in uterus invasion. The coexpression of PPARgamma and RXRalpha 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 PPARgamma/RXRalpha heterodimers in vitro, and we showed that both synthetic (rosiglitazone) and natural [15-deoxy-delta-(12,14)PGJ(2)] PPARgamma agonists inhibit extravillous cytotrophoblast invasion in a concentration-dependent manner and synergize with pan-RXR agonists. Conversely, PPARgamma or pan-RXR antagonists promoted extravillous cytotrophoblast invasion. Furthermore, the pan-RXR antagonist abolished the inhibitory effect of the PPARgamma agonists. Together these data underscore an important function of PPARgamma/RXRalpha heterodimers in the modulation of trophoblast invasion.

Cell Differentiation↗