The effects of growth factors on human normal placental cytotrophoblast cell proliferation

Chemical mixture that targets the epidermal growth factor pathway impairs human trophoblast cell functions

Pregnant women are exposed to complex chemical mixtures, many of which reach the placenta. Some of these chemicals interfere with epidermal growth factor receptor (EGFR) activation, a receptor tyrosine kinase that modulates several placenta cell functions. We hypothesized that a mixture of chemicals (Chem-Mix) known to reduce EGFR activation (polychlorinated biphenyl (PCB)-126, PCB-153, atrazine, trans-nonachlor, niclosamide, and bisphenol S) would interfere with EGFR-mediated trophoblast cell functions. To test this, we determined the chemicals' EGFR binding ability, EGFR and downstream effectors activation, and trophoblast functions (proliferation, invasion, and endovascular differentiation) known to be regulated by EGFR in extravillous trophoblasts (EVTs). The Chem-Mix competed with EGF for EGFR binding, however only PCB-153, niclosamide, trans-nonachlor, and BPS competed for binding as single chemicals. The effects of the Chem-Mix on EGFR phosphorylation were tested by exposing the placental EVT cell line, HTR-8/SVneo to control (0.1% DMSO), Chem-Mix (1, 10, or 100 ng/ml), EGF (30 ng/ml), or Chem-Mix + EGF. The Chem-Mix - but not the individual chemicals - reduced EGF-mediated EGFR phosphorylation in a dose dependent manner, while no effect was observed in its downstream effectors (AKT and STAT3). None of the individual chemicals affected EVT cell invasion, but the Chem-Mix reduced EVT cell invasion independent of EGF. In support of previous studies that have explored chemicals targeting a specific pathway (estrogen/androgen receptor), current findings indicate that exposure to a chemical mixture that targets the EGFR pathway can result in a greater impact compared to individual chemicals in the context of placental cell functions.

Dual role of TGF-β in early pregnancy: clues from tumor progression

TGF-β signaling in the endometrium is active during the implantation period and has a pivotal role in regulating endometrial receptivity and embryo implantation. During embryo implantation, both apoptosis and proliferation of endometrial cells happen at the same time and it seems TGF-β is the factor that controls both of these processes. As shown in cancer cells, in special conditions this cytokine can have a dual effect and switch the action from apoptosis to proliferation. Owing to the similarity between embryo implantation and cancer development and also unusual pattern of proliferation and remodeling in the uterus, in this review we suggest the existence of such a switching in endometrium during the early pregnancy. Moreover, we address some potential mechanisms that could regulate the switching. A better understanding of the molecular mechanisms regulating TGF-β action and signaling during the implantation period could pave the way for introducing novel therapeutic strategies in order to solve implantation-associated issues such as repeated implantation failure.

HTR-8/SVneo: A model for epithelial to mesenchymal transition in the human placenta

INTRODUCTION

The placenta is a transitory organ essential for proper fetal maturation and growth. Trophoblasts, the main cell type of the placenta, differentiate along the villous or extravillous pathways. The ability of villous cytotrophoblasts to undergo an epithelial-to-mesenchymal transition to form the invasive extravillous trophoblasts is vital for a successful pregnancy outcome. Many trophoblastic cell lines, including HTR-8/SVneo, have been widely used to investigate extravillous trophoblast biology and functions. We have previously reported that HTR-8/SVneo cell line contains a mixed populations of epithelial and mesenchymal cells. Uncovering the mechanisms underlying this heterogeneity is essential for the proper study of normal and pathological placental function.

METHODS

HTR-8/SVneo was subjected to monoclonal isolation, spheroid formation assay and cell sorting to isolate pure epithelial and mesenchymal populations. These fractions were maintained in culture and assessed for expression of epithelial and mesenchymal markers using quantitative real-time PCR and immunofluorescence. In addition, the implication of TGFβ in the EMT process was investigated using a selective inhibitor of TGF-βR1 (A83-01).

RESULTS

Passaging of the pure epithelial population maintained under normal culture condition resulted in a shift to a mesenchymal phenotype. This transition was reduced upon inhibiting TGF-βR1. Similarly, E-cadherin positive HTR-8/SVneo spheroids plated in 2D culture resulted in the emergence of streams of invading mesenchymal cells.

DISCUSSION

HTR-8/SVneo cell line is undergoing EMT under normal culture condition and TGFβ is a key mediator of this process. Our results raise the possibility of using HTR-8/SVneo cell line as a model to investigate EMT in extravillous trophoblast cells.

The effect of maternal NODAL on STOX1 expression in extravillous trophoblasts is mediated by IGF1

The number of molecules identified to be involved in communication between placenta and decidua is fast expanding. Previously, we showed that NODAL expressed in maternal endometrial stromal cells is able to affect NODAL and STOX1 expression in placental extravillous trophoblasts. The effect of maternal NODAL on placental NODAL expression is achieved via Activin A, while preliminary data suggests that maternal NODAL affects STOX1 expression in trophoblasts potentially via IGF1. In the current study, T-HESC endometrial stromal cells were treated with siRNAs against NODAL after which IGF1 mRNA expression was determined by quantitative RT-PCR, while IGF1 secretion was measured by ELISA. Recombinant IGF1 and inhibitors of the MAPK and PI3K/AKT pathways were added to SGHPL-5 extravillous trophoblasts after which the effects on STOX1 mRNA and STOX1 protein expression were determined. The effect of IGF1 and the MAPK and PI3K/AKT inhibitors on the invasive capacity of SGHPL-5 cells was investigated by performing invasion assays. We found that T-HESC cells treated with NODAL siRNAs showed significant upregulation of IGF1 mRNA expression and IGF1 protein secretion. Addition of IGF1 to SGHPL-5 cell media significantly upregulated STOX1 mRNA and protein expression. Using inhibitors of the PI3K/AKT and MAPK pathway showed that the effect of IGF1 on STOX1 expression is accomplished via MAPK signaling. Secondly, PI3K inhibition independently leads to reduced STOX1 expression which can be rescued by adding IGF1. IGF1 was unable to influence the invasive capacity of SGHPL-5 cells, while inhibiting the PI3K/AKT pathway did reduce the invasion of these cells. To conclude, here we show that downregulated NODAL expression in endometrial stromal cells, previously associated with pre-eclampsia like symptoms in mice, increases IGF1 secretion. Increased levels of IGF1 lead to increased expression levels of STOX1 in extravillous trophoblasts via the MAPK pathway, hereby identifying a novel signaling cascade involved in maternal-fetal communication.

Endoglin pathway genetic variation in preeclampsia: A validation study in Norwegian and Latina cohorts

OBJECTIVE

The purpose of this study was to validate our previous genetic association findings related to the endoglin (ENG) pathway from an American Caucasian preeclampsia cohort in independent preeclampsia cohorts. We also sought to explore the ENG pathway for new genetic associations in these independent cohorts.

STUDY DESIGN

We used a tagging single nucleotide (tSNP) approach to assess genetic variability across five ENG pathway genes (ENG, TGFβ1, TGFβR1, ALK1, and TGFβR2) in a Caucasian cohort from Norway (n = 77 preeclampsia cases & n = 63 normotensive controls) and a White Hispanic cohort from Southern California (n = 69 preeclampsia cases & n = 106 normotensive controls).

MAIN OUTCOME MEASURES

Univariate analyses (Chi Square, Fisher's Exact) and multivariate logistic regression were conducted to evaluate the association between tSNP genotype distributions and pregnancy outcome in each cohort. Logistic regression models were adjusted for maternal age at delivery, infant sex, parity, smoking during pregnancy, and pre-pregnancy BMI.

RESULTS

Although we were unable to replicate our previous SNP-specific findings (ENG rs11792480, rs10121110; TGFβR2 rs6550005; p's > 0.05), we found that genetic variation in TGFβR1[ALK5] (rs6478974) and TGFβR2 (rs11129420, rs6802220, rs1155708, rs3773640, rs3773663) was significantly associated with preeclampsia in the Norwegian cohort and genetic variation in ALK1 (rs706819) and TGFβR2 (rs9843942) was significantly associated with preeclampsia in the Latina cohort.

CONCLUSION

Overall, our results provide further support for the involvement and investigation of the endoglin pathway in preeclampsia.

Establishment and characterization of cell lines derived from complete hydatidiform mole

Gestational trophoblastic diseases (GTDs) are a group of diseases characterized by abnormal cellular proliferation of atypical trophoblasts. A hydatidiform mole is an abnormal pregnancy caused by genetic fertilization disorders, and it can be classified as a complete hydatidiform mole (CHM) or a partial hydatidiform mole. The aim of this study was to establish cell lines from CHMs and to characterize the cells for future studies concerning GTD. HMol1-2C, HMol1-3B, HMol1-8 and HMol3-1B were established from primary cultures of CHM explants following the introduction of different combinations of genes including human telomerase reverse transcriptase (hTERT), a mutant form of CDK (CDK4R24C), cyclin D1, p53C234, MYC and HRAS. HMol1-2C, HMol1-3B, and HMol3-1B were confirmed to originate from trophoblasts of androgenic, homozygous CHMs. These three cell lines exhibited low human chorionic gonadotropin secretion, low migration and invasion abilities, and the potential to differentiate into syncytiotrophoblastic cells via forskolin treatment. These results suggest that these cells exhibit characteristics of trophoblastic cells, especially cytotrophoblastic cells. HMol1-8 was found to consist of diploid cells and originated from maternal cells, suggesting that they were derived from decidual cells. In conclusion, we successfully established three cell lines from CHMs by introduction of hTERT and other genes. Analysis revealed that the genetic origin of each cell line was identical with that of the original molar tissue, and the cell lines exhibited characteristics of trophoblastic cells, which are similar to undifferentiated cytotrophoblasts.

Epithelial-mesenchymal transition during extravillous trophoblast differentiation

A successful pregnancy depends on the intricate and timely interactions of maternal and fetal cells. Placental extravillous cytotrophoblast invasion involves a cellular transition from an epithelial to mesenchymal phenotype. Villous cytotrophoblasts undergo a partial epithelial to mesenchymal transition (EMT) when differentiating into extravillous cytotrophoblasts and gain the capacity to migrate and invade. This review summarizes our current knowledge regarding known regulators of EMT in the human placenta, including the inducers of EMT, upstream transcription factors that control EMT and the downstream effectors, cell adhesion molecules and their differential expression and functions in pregnancy pathologies, preeclampsia (PE) and fetal growth restriction (FGR). The review also describes the research strategies that were used for the identification of the functional role of EMT targets in vitro. A better understanding of molecular pathways driven by placental EMT and further elucidation of signaling pathways underlying the developmental programs may offer novel strategies of targeted therapy for improving feto-placental growth in placental pathologies including PE and FGR.

Epidermal growth factor: Porcine uterine luminal epithelial cell migratory signal during the peri-implantation period of pregnancy

The majority of early conceptus mortality in pregnancy occurs during the peri-implantation period, suggesting that this period is important for conceptus viability and the establishment of pregnancy. Successful establishment of pregnancy in all mammalian species depends on the orchestrated molecular events that transpire at the conceptus-uterine interface during the peri-implantation period of pregnancy. This maternal-conceptus interaction is especially crucial in pigs because they have a non-invasive epitheliochorial placentation during a protracted peri-implantation period. During the pre-implantation period of pregnancy, conceptus survival and the establishment of pregnancy depend on the developing conceptus receiving an adequate supply of histotroph which contains a wide range of nutrients and growth factors. Evidence links epidermal growth factor (EGF) to embryogenesis or implantation in various mammalian species. EGF exhibits potential growth-promoting activities on the conceptus and endometrium; however, in the case of pigs, little is known its functions, especially their regulatory mechanisms at the maternal-conceptus interface. EGF receptor (EGFR) mRNA and protein are abundant in endometrial luminal (LE) and glandular (GE) epithelia and conceptus trophectoderm on Days 13-14 of pregnancy, suggesting that EGF provides an autocrine signal to uterine LE and GE just prior to implantation. Therefore, the objectives of this study were to determine: 1) the potential intracellular signaling pathways responsible for the activities of EGF in porcine uterine LE (pLE) cells; and 2) the changes in cellular activities induced by EGF. EGF treatment of pLE cells increased the abundance of phosphorylated (p)-ERK1/2, p-P70RSK and p-RPS6 compared to that for control cells. Furthermore, EGF-stimulated phosphorylation of ERK1/2 MAPK was inhibited in pLE cells transfected with an EGFR siRNA compared with control siRNA-transfected pLE cells. Moreover, EGF stimulated migration of pLE cells, but this stimulatory effect was blocked by U0126, a pharmacological inhibitor or ERK1/2 MAPK. Collectively, these results provide new insights into mechanisms whereby EGF regulates development of the peri-implantation uterine LE at the fetal-maternal interface. These results indicate that endometrial- and/or conceptus derived EGF effects migration of uterine LE and that those stimulatory effects are regulated via the ERK1/2 MAPK pathway during early pregnancy in pigs.

Epidermal growth factor stimulates proliferation and migration of porcine trophectoderm cells through protooncogenic protein kinase 1 and extracellular-signal-regulated kinases 1/2 mitogen-activated protein kinase signal transduction cascades during early pregnancy

For successful implantation and establishment of early epitheliochorial placentation, porcine conceptuses require histotroph, including nutrients and growth factors, secreted by or transported into the lumen of the uterus. Epidermal growth factor (EGF), an essential component of histotroph, is known to have potential growth-promoting activities on the conceptus and uterine endometrium. However, little is known about its effects to transactivate cell signaling cascades responsible for proliferation, growth and differentiation of conceptus trophectoderm. In the present study, therefore, we determined that EGFR mRNA and protein were abundant in endometrial luminal and glandular epithelia, stratum compactum stroma and conceptus trophectoderm on days 13-14 of pregnancy, but not in any other cells of the uterus or conceptus. In addition, primary porcine trophectoderm (pTr) cells treated with EGF exhibited increased abundance of phosphorylated (p)-AKT1, p-ERK1/2 MAPK and p-P90RSK over basal levels within 5min, and effect that was maintained to between 30 and 120min. Immunofluorescence microscopy revealed abundant amounts of p-ERK1/2 MAPK and p-AKT1 proteins in the nucleus and, to a lesser extent, in the cytoplasm of pTr cells treated with EGF as compared to control cells. Furthermore, the abundance of p-AKT1 and p-ERK1/2 MAPK proteins was inhibited in control and EGF-treated pTr cells transfected with EGFR siRNA. Compared to the control siRNA transfected pTr cells, pTr cells transfected with EGFR siRNA exhibited an increase in expression of IFND and TGFB1, but there was no effect of expression of IFNG. Further, EGF stimulated proliferation and migration of pTr cells through activation of the PI3K-AKT1 and ERK1/2 MAPK-P90RSK cell signaling pathways. Collectively, these results support the hypothesis that EGF coordinately activates multiple cell signaling pathways critical to proliferation, migration and survival of trophectoderm cells that are critical to development of porcine conceptuses during implantation and placentation.

The tyrosine phosphatase SHP-1 negatively regulates cytotrophoblast proliferation in first-trimester human placenta by modulating EGFR activation

Insulin-like growth factors (IGFs) influence placental cell (cytotrophoblast) kinetics. We recently reported that the protein tyrosine phosphatase (PTP) SHP-2 positively regulates IGF actions in the placenta. In other systems, the closely related PTP, SHP-1, functions as a negative regulator of signaling events but its role in the placenta is still unknown. We examined the hypothesis that SHP-1 negatively regulates IGF actions in the human placenta. Immunohistochemical (IHC) analysis demonstrated that SHP-1 is abundant in cytotrophoblast. SHP-1 expression was decreased in first-trimester placental explants using siRNA; knockdown did not alter IGF-induced proliferation but it significantly enhanced proliferation in serum-free conditions, revealing that placental growth is endogenously regulated. Candidate regulators were determined by using antibody arrays, Western blotting, and IHC to examine the activation status of multiple receptor tyrosine kinases (RTKs) in SHP-1-depleted explants; amongst the alterations observed was enhanced activation of EGFR, suggesting that SHP-1 may interact with EGFR to inhibit proliferation. The EGFR tyrosine kinase inhibitor PD153035 reversed the elevated proliferation seen in the absence of SHP-1. This study demonstrates a role for SHP-1 in human trophoblast turnover and establishes SHP-1 as a negative regulator of EGFR activation. Targeting placental SHP-1 expression may provide therapeutic benefits in common pregnancy conditions with abnormal trophoblast proliferation.

Leukaemia inhibitory factor mediated proliferation of HTR-8/SVneo trophoblast cells is dependent on activation of extracellular signal-regulated kinase 1/2

Leukaemia inhibitory factor (LIF) is one of the cytokines that is indispensable for embryo implantation. The aim of the present study was to investigate the role of activation of extracellular signal-regulated kinase (ERK) 1/2 in LIF-mediated proliferation of HTR-8/SVneo cells. Stimulation of HTR-8/SVneo cells with LIF (50 ng mL(-1)) resulted in an increase in cell proliferation (P < 0.05) via increased transition of cells to the G(2)/M phase of cell cycle. Stimulation with LIF resulted in the activation of both signal transducer and activator of transcription (STAT) 3 Tyr(705) and ERK1/2, but inhibition of ERK1/2 signalling by pretreatment of cells with U0126 (10 µM) for 2h resulted in abrogation of LIF-mediated increases in G(2)/M transition, with a significant decrease (P < 0.05) in absolute cell numbers compared with control. Although STAT3 silencing had no effect on LIF-dependent proliferation of HTR-8/SVneo cells, it did result in an increase in cell apoptosis, which increased further upon inhibition of ERK1/2 activation irrespective of LIF stimulation. Stimulation of cells with LIF increased the Bcl-2/Bax ratio, whereas ERK1/2 inhibition decreased the Bcl-2/Bax ratio, even after LIF stimulation. Hence, it can be inferred that ERK1/2 activation is essential for LIF-mediated increases in proliferation and that both STAT3 and ERK1/2 activation are important for the survival of HTR-8/SVneo cells.

Cytokines and Growth Factors in Implantation

Implantation failure is the most important rate limiting factor in the success of assisted reproductive techniques like In vitro fertilization–embryo transfer (IVF-ET). Cytokines are multifunctional signaling molecules having an implicit role in the human implantation process. This review focuses on the redundant roles of cytokines during the various stages of implantation. It also indicates that levels of cytokines in biological fluids like serum and follicular fluid obtained during oocyte retrieval might act as determinants of implantation potential of the blastocyst. Thus a holistic, metabolomic approach of analyzing biological fluids may provide a simpler approach to study the hitherto enigmatic process rather than the proteomic and genomic approach.

Epidermal growth factor (EGF) induces motility and upregulates MMP-9 and TIMP-1 in bovine trophoblast cells

Differentiation and restricted invasion/migration of trophoblast cells are crucial for feto-maternal communication in the synepitheliochorial placenta of cattle. EGF is expressed in the bovine placenta and likely regulates these cell properties. As cell migration and motility rely on the degradation of extracellular matrix we hypothesize that EGF is involved in the regulation of the MMP-9/TIMP-1 balance and thus could influence trophoblast migration, tissue remodeling, and the release of the fetal membranes after parturition. The aim of this in vitro study was to examine EGF-mediated effects on cell motility, proliferation, and MMP-9 and TIMP-1 expression in cultured bovine trophoblast cells. We used a trophoblast cell line (F3) derived from bovine placentomes to examine the influence of EGF on MMP-9 and TIMP-1 expression by semiquantitative RT-PCR and MMP activity by zymography. Migration assays were performed using a Boyden chamber and cell motility was measured by time-lapse analyses. To identify the involved signaling cascades, phosphorylation of mitogen-activated protein kinase (MAPK) 42/44 and Akt was detected by Western blot. EGF treatment increased both the abundance of MMP-9 and TIMP-1 mRNAs and the proteolytic activity of MMP-9. Furthermore, EGF stimulated proliferation and migration of F3 cells. Addition of specific inhibitors of MAPK (PD98059) and/or PI3K (LY294002) activation abolished or reduced EGF-induced effects in all experiments. In conclusion, EGF-mediated effects stimulate migration and proliferation of bovine trophoblast cells and may be involved in bovine placental tissue remodeling and postpartum release of fetal membranes.

Down syndrome screening: imagining the screening test of the future

Prenatal screening for Down syndrome (DS) is performed by risk calculation based on biochemical and biometric parameters. This way, approximately 75-85% of all DS cases can be detected. A way to improve detection rates is to search for new screening markers. Since the majority of biomarkers used in current DS screening are predominantly produced by the placenta, and the presence of an extra chromosome (as in DS) complicates placental development and function, it is plausible to assume that new potential screening markers may also originate from the placenta. Any alterations in these markers can be attributed to abnormal placental development and function. This article focuses on normal early placental development and function compared with that in DS pregnancies. Using this knowledge, we reason towards candidate biomarkers that may be useful in screening for DS.

Prostasin regulates human placental trophoblast cell proliferation via the epidermal growth factor receptor signaling pathway

BACKGROUND

Prostasin is a glycosylphosphatidylinositol-anchored extracellular serine protease with a role in epidermal growth factor receptor (EGFR) signal modulation. EGFR signaling has been shown to be important for regulating cytotrophoblast (CT) cell proliferation in human placenta. We investigated the impact of prostasin expression regulation on this cellular function as well as the molecular mechanisms involved in human cytotrophoblastic cells.

METHODS

An immortalized normal human CT cell line (B6Tert-1) was used as an in vitro cell model. Prostasin expression in B6Tert-1 cells was knocked down by transfection of a short interfering RNA. Lentivirus-mediated expression of recombinant human prostasin under tetracycline regulation was performed to obtain stable B6Tert-1 cell sublines that over-expressed prostasin. Changes in cell proliferation and EGFR signaling were evaluated by immunocytochemistry for Ki67 and western blot analysis, respectively, in B6Tert-1 cells with knocked-down or increased prostasin expression.

RESULTS

Prostasin knock-down in B6Tert-1 cells resulted in inhibition of cell proliferation, in association with down-regulated EGFR protein expression (both P < 0.05 versus control) as well as reduced phosphorylation of c-raf, mitogen-activated protein kinase (MAPK) kinases (MEK1/2) and extracellular signal-regulated kinases (Erk1/2) (all P < 0.05 versus control). Over-expression of prostasin led to up-regulation of the EGFR protein, but had no effect on cell proliferation or phosphorylation of MAPK signaling molecules in the B6Tert-1 cells.

CONCLUSIONS

Prostasin may regulate trophoblast cell proliferation via modulating the EGFR-MAPK signaling pathway.

The role of growth factors and cytokines during implantation: endocrine and paracrine interactions

Implantation, a critical step for establishing pregnancy, requires molecular and cellular events resulting in uterine growth and differentiation, blastocyst adhesion, invasion, and placental formation. Successful implantation requires a receptive endometrium, a normal and functional embryo at the blastocyst stage, and a synchronized dialogue between maternal and embryonic tissues. In addition to the well-characterized role of sex steroids, the complexity of embryo implantation and placentation is exemplified by the number of cytokines and growth factors with demonstrated roles in these processes. Disturbances in the normal expression and action of these cytokines result in an absolute or partial failure of implantation and abnormal placental formation in mice and human. Members of the gp130 cytokine family, interleukin-11 (IL-11) and leukemia inhibitory factor, the transforming growth factor beta superfamily, the colony-stimulating factors, and the IL-1 and IL-15 systems are crucial molecules for a successful implantation. Chemokines are also important, both in recruiting specific cohorts of leukocytes to the implantation site and in trophoblast trafficking and differentiation. This review provides discussion of the embryonic and uterine factors that are involved in the process of implantation in autocrine, paracrine, and/or juxtacrine manners at the hormonal, cellular, and molecular levels.

Simultaneous differentiation of endothelial and trophoblastic cells derived from human embryonic stem cells

Here we present a simple two-step in vitro model of vascularized trophoblastic tissue derived from human embryonic stem (hES) cells. The first step is the formation of cystic embryoid bodies (EBs) in suspension in a semisolid methyl cellulose medium, within which an endothelial platelet/endothelial cell adhesion molecule-1 (PECAM-1(+)) cell network develops. In a second step, deposition of these EBs on the bottom of nontreated, polystyrene tissue culture plates, leads by centrifugal outgrowth of the EB to the emergence of an adherent cell layer, with which a PECAM-1(+) network is associated. Cells of this adherent layer expressed VE-cadherin (CD144), PECAM-1 (CD31), and alpha-fetoprotein (alpha-FP). Trophoblastic differentiation was strongly suggested by the secretion of beta-human chorionic gonadotropin (beta-hCG) and by the presence of the cytotrophoblast and syncytiotrophoblast marker GB25. The INSL4 gene, a cyto and syncytio-trophoblast marker, was also highly expressed in the adherent layer, as well as other trophoblast genes such as CGA, CDX1, CDX2, and HAND1, compared to hES cell gene expression taken as reference. In contrast, expression of self-renewal genes, such as TERT, POU5F1, ZFP42, GDF3, and NODAL were decreased. No ectodermal or endodermal genes were expressed, but the mesodermal genes PECAM-1 and GATA2 were. The possibility of removing the EBs during the second step would permit analysis of their relative contribution to angiogenesis or possible hemangioblast formation, compared to that of the trophoblastic adherent layer. This primitive vascularized trophoblastic model could also provide a tool to study early steps of normal and pathological placental development.

TGF-β superfamily expression and actions in the endometrium and placenta

Transforming growth factor β (TGFβ) superfamily members are closely associated with tissue remodelling events and reproductive processes. This review summarises the current state of knowledge regarding the expression and actions of TGFβ superfamily members in the uterus, during the menstrual cycle and establishment of pregnancy. TGFβs and activin β subunits are abundantly expressed in the endometrium, where roles in preparation events for implantation have been delineated, particularly in promoting decidualisation of endometrial stroma. These growth factors are also expressed by epithelial glands and secreted into uterine fluid, where interactions with preimplantation embryos are anticipated. Knockout models and embryo culture experiments implicate activins, TGFβs, nodal and bone morphogenetic proteins (BMPs) in promoting pre- and post-implantation embryo development. TGFβ superfamily members may therefore be important in the maternal support of embryo development. Following implantation, invasion of the decidua by fetal trophoblasts is tightly modulated. Activin promotes, whilst TGFβ and macrophage inhibitory cytokine-1 (MIC-1) inhibit, trophoblast migration in vitro, suggesting the relative balance of TGFβ superfamily members participate in modulating the extent of decidual invasion. Activins and TGFβs have similar opposing actions in regulating placental hormone production. Inhibins and activins are produced by the placenta throughout pregnancy, and have explored as a potential markers in maternal serum for pregnancy and placental pathologies, including miscarriage, Down’s syndrome and pre-eclampsia. Finally, additional roles in immunomodulation at the materno-fetal interface, and in endometrial inflammatory events associated with menstruation and repair, are discussed.

Dual effect of transforming growth factor β1 on cell adhesion and invasion in human placenta trophoblast cells

Transforming growth factor β (TGFβ) has been shown to be a multifunctional cytokine required for embryonic development and regulation of trophoblast cell behaviors. In the present study, a non-transformed cell-line representative of normal human trophoblast (NPC) was used to examine the effect of TGFβ1 on trophoblast cell adhesion and invasion.In vitroassay showed that TGFβ1 could significantly promote intercellular adhesion, while inhibiting cell invasion across the collagen I-coated filter. Reverse transcription (RT)-PCR and gelatin zymography demonstrated that TGFβ1 evidently repressed the mRNA expression and proenzyme production of matrix metalloproteinase (MMP)-9, but exerted no effect on mRNA expression and secretion of MMP-2. On the other hand, both the mRNA and protein expression of epithelial-cadherin and β-catenin were obviously upregulated by TGFβ1 in dose-dependent fashion, as revealed by RT-PCR and western-blot analysis. What is more, one of the critical TGFβ signaling molecules – Smad2 was notably phosphorylated in TGFβ1-treated NPC cells. The data indicates that cell invasion and adhesion are coordinated processes in human trophoblasts and that there exists paracrine regulation on adhesion molecules and invasion-associated enzymes in human placenta.

Expression of inhibins, activins, insulin-like growth factor-I and steroidogenic enzymes in the equine placenta

In this study, the expression patterns of inhibins, activins, insulin-like growth factor-I (IGF-I) and steroidogenic enzymes in equine placentae recovered during the latter two-thirds of gestation were examined. Concentrations of inhibin A and inhibin pro-alphaC in endometrial and fetal placental tissue homogenates were very low during the period examined, whereas these tissues contained high concentrations of activin A. In both maternal endometrial and fetal placental tissues, activin A levels decreased as pregnancy progressed. Expression of inhibin alpha-subunit was not observed in the placenta using either immunohistochemistry or in situ hybridization. Inhibin/activin betaA-subunit and its mRNA were confined to maternal endometrial glands, whereas immunopositive betaB-subunit was not detected in either endometrial glands or microcotyledons. Cytochrome P450 side chain cleavage enzyme was detected by immunohistochemistry in both endometrial glands and microcotyledons, whereas cytochrome P450 17alpha-hydroxylase/lyase was absent in these tissues. Immunopositive signals for 3beta-hydroxysteroid dehydrogenase and cytochrome P450 aromatase were localized in microcotyledons but not in endometrial glands. Immunohistochemistry revealed that IGF-I was highly expressed in microcotyledons around Day 130, and decreased as pregnancy progressed. Changes in the expression of IGF-I were correlated with the number of PCNA positive cells in the placenta. The present study demonstrated the presence and localized the site of expression of activin, IGF-I and steroidogenic enzymes in equine placental tissues during the latter two-thirds of gestation; the results suggest that activin and IGF-I may be involved in the regulation of placental development.

Human trophoblast function during the implantation process

The implantation process involves complex and synchronized molecular and cellular events between the uterus and the implanting embryo. These events are regulated by paracrine and autocrine factors. Trophoblast invasion and migration through the uterine wall is mediated by molecular and cellular interactions, controlled by the trophoblast and the maternal microenvironment. This review is focused on the molecular constituents of the human trophoblast, their actions and interactions, including interrelations with the uterine endometrium.

Cytokines, chemokines and growth factors in endometrium related to implantation

The complexity of the events of embryo implantation and placentation is exemplified by the number and range of cytokines with demonstrated roles in these processes. Disturbance of the normal expression or action of these cytokines results in complete or partial failure of implantation and abnormal placental formation in mice or humans. Of known importance are members of the gp130 family such as interleukin-11 (IL-11) and leukaemia inhibitory factor (LIF), the transforming growth factor beta (TGFbeta) superfamily including the activins, the colony-stimulating factors (CSF), the IL-1 system and IL-15 system. New data are also emerging for roles for a number of chemokines (chemoattractive cytokines) both in recruiting specific cohorts of leukocytes to implantation sites and in trophoblast differentiation and trafficking. This review focuses on those cytokines and chemokines whose expression pattern in the human endometrium is consistent with a potential role in implantation and placentation and for which some relevant actions are known. It examines what is known of their regulation and action along with alterations in clinically relevant situations.

Down-regulation and promoter methylation of tissue inhibitor of metalloproteinase 3 in choriocarcinoma

OBJECTIVE

To assess the differential gene expression in neoplastic and normal trophoblastic cells and evaluate the effect of methylation on tissue inhibitor of metalloproteinase 3 (TIMP3) expression in choriocarcinoma (CCA) cells.

METHODS

The Atlas Human Cancer 1.2 Array (Clontech) was used to compare differential gene expression in a trophoblastic cell line (B6) established from first term placenta with two choriocarcinoma cell lines (JAR and JEG-3). The differentially expressed candidate genes in the placental and malignant trophoblastic cells in these cell lines were confirmed by real-time polymerase chain reaction (PCR), Western blotting and immunohistochemistry. Differential expression of a specific gene, TIMP3, was confirmed by immunohistochemistry using clinical specimens of choriocarcinoma and placenta. The involvement of promoter methylation in suppression of TIMP3 expression in choriocarcinoma was examined using methylation-specific PCR (MSP) and demethylation treatment.

RESULTS

Differential expression of 23 genes was observed in choriocarcinoma cell lines compared to the placental trophoblastic cells using the cDNA array analysis (Atlas Human Cancer Array, Clontech). Among these differentially expressed genes, down-regulation of TIMP3, PLAB, IGFBP3 and up-regulation of CCNB1 were confirmed by real-time PCR determination. Reduced expression of TIMP3 was further confirmed in clinical samples of choriocarcinoma by immunohistochemical staining. Methylation of TIMP3 promoter was detected in choriocarcinoma cell lines and clinical samples of choriocarcinoma. Treatment with a demethylation drug, 5-aza-2'-deoxycytidine, in choriocarcinoma cell lines restored TIMP3 expression.

CONCLUSION

Down-regulation of TIMP3, PLAB, IGFBP3 and up-regulation of CCNB1 were observed in choriocarcinoma cells compared to placental trophoblasts. Down-regulation of TIMP3 expression was confirmed in clinical specimens of choriocarcinoma and may play a role in its pathogenesis. Promoter methylation of the TIMP3 is involved in suppression of TIMP3 expression. Differentiation expression of TIMP3 in choriocarcinoma may have potential application in clinical diagnosis and patient treatment.

Three-dimensional spheroidal culture of cytotrophoblast cells mimics the phenotype and differentiation of cytotrophoblasts from normal and preeclamptic pregnancies

Normal placental development is dependent on the orchestrated differentiation of cytotrophoblast (CTB) cells. This study was aimed at studying cytotrophoblast cells from normal and preeclamptic pregnancies in a three-dimensional spheroid-based cell culture model. First trimester cytotrophoblast cells cultured as spheroids maintain their high proliferative and invasive phenotype and respond to different cytokines upon stimulation in a three-dimensional invasion assay. In contrast, third trimester cytotrophoblast spheroids maintain their quiescent nonproliferating phenotype and invasion can only be induced by EGF. Contrasting the regular spheroidal arrangement of cytotrophoblast cells from normal third trimester pregnancies, spheroidal organization of preeclamptic cytotrophoblast cells is disturbed and the cells downregulate CD105 in vivo and in vitro. Furthermore, the invasion of both normal and preeclamptic third trimester, but not first trimester cytotrophoblast cells, is inhibited by pro-inflammatory cytokines. Plasma samples from pregnant women with preeclampsia significantly stimulate the invasion of first trimester cytotrophoblast cells and the sprouting of human umbilical vein endothelial cells (HUVECs) compared to plasma samples from healthy pregnant women. Taken together, the data establish the spheroidal cytotrophoblast model as a powerful system to mimic the in vivo phenotype of first and third trimester and preeclamptic cytotrophoblast cells and demonstrate that plasma-derived factors modulate the differentiation of cytotrophoblast cells.

Trophoblast 'pseudo-tumorigenesis': significance and contributory factors

Trophoblast cells of the human placenta proliferate, migrate, and invade the pregnant uterus and its vasculature in order to nourish the developing fetus, in a way that is imitated by malignant tumors. Many similarities exist between embryo implantation and the growth of cancer cells. We begin this article by reviewing decades of studies that have helped unearth the mechanisms that contribute to the tumor-like phenotype of human trophoblast cells. Interestingly, these attributes are only transient in nature, with stringent spatial and temporal confines. The importance of intrinsic molecular controls that effectively circumscribe the extent and duration of trophoblast incursion, becomes increasingly evident in abnormal pregnancies that are characterized by aberrant trophoblast proliferation/invasion. We summarize and discuss the significance of abnormalities in these regulatory mechanisms, and finally, speculate about the use of human trophoblastic cells as model systems for the study of a variety of cellular processes. While on one hand, human placental cells are bestowed with a capacity to proliferate indefinitely and invade extensively, on the other, these cells are also replete with mechanisms to regulate these tumor-like attributes and eventually progress to a senescent apoptotic state. This is therefore, a 'well-behaved' tumor. The comparison in the present review is between the invasive cytotrophoblastic cell type and the tumor cell type.

Epidermal growth factor enhances invasive activity of BeWo choriocarcinoma cells by inducing alpha2 integrin expression

The trophoblast, an important component of the mammalian placenta, has several essential biological roles in the maintenance of pregnancy. First, trophoblast cells must attach to the uterine endometrium, and then they must invade to a depth at which the vascular network exists. Here, we investigated the effects of epidermal growth factor (EGF) on alpha2 integrin expression, adhesiveness to collagen, and invasive activity using human BeWo choriocarcinoma cells. EGF induced the expression of alpha2 integrin mRNA and protein, as shown by Northern blotting, Western blotting, and flow cytometry. Human chorionic gonadotropin (hCG) secretion was enhanced by the addition of EGF, which suggests that the BeWo cells functionally differentiated similarly to normal trophoblasts. EGF also dose-dependently stimulated the invasiveness of BeWo cells. Antibody against alpha2 integrin inhibited this effect, suggesting that it may be mediated by an increase of cell surface integrin. EGF had no effect on the adhesiveness of BeWo cells to collagen, whereas it stimulated the chemokinetic activity in a dose-dependent manner. The increase of chemokinetic activity was suppressed by antibody against alpha2 integrin. These results suggest that EGF may induce alpha2 integrin expression in trophoblast cells, thereby enhancing their invasiveness into the endometrium via an increase of their chemokinetic activity.

Effect of supplementation of leukemia inhibitory factor and epidermal growth factor on murine embryonic development in vitro, implantation, and outcome of offspring

OBJECTIVES

To evaluate the supplementation of leukemia inhibitory factor (LIF) or epidermal growth factor (EGF) in a single culture system (IVF50) and a sequential culture system (IVF50-S2) to determine whether they had any additional benefit on embryo development and implantation.

DESIGN

Prospective controlled animal study.

SETTING

University research laboratory.

SUBJECT(S)

Two-cell embryos from F1(CBA x C57BL) mice.

INTERVENTION(S)

Embryos were randomly cultured in different growth factor-treated or untreated in vitro systems.

MAIN OUTCOME MEASURE(S)

Blastocyst formation and morphology, total cell numbers of day 5 blastocysts, birth rates, and characteristics of the offspring.

RESULT(S)

The beneficial effects of LIF or EGF on blastocyst development and morphology were observed only in IVF50 medium but not in sequential IVF50-S2 media. In addition, blastocysts generated from the LIF-supplemented cultures had higher total cell numbers and higher total birth rates after transfer compared to those from IVF50 medium alone. No significant effect on fetal development was observed but pups born after treatment in LIF-supplemented sequential cultures had prolonged gestation and increased birth weights.

CONCLUSION(S)

The beneficial effects of LIF and EGF on in vitro blastocyst development are mainly seen under suboptimal culture conditions (simple medium only) and their effects are masked in an improved in vitro system (sequential culture media). Supplementation of culture media with such factors, however, is still an attractive approach in enhancing embryo viability through increased total cell numbers. The beneficial effect of LIF in improving implantation and subsequent increased birth rates should be further explored.

Glucose regulates insulin mitogenic effect by modulating SHP-2 activation and localization in JAr cells

The glucose effect on cell growth has been investigated in the JAr human choriocarcinoma cells. When JAr cells were cultured in the presence of 6 mm glucose (LG), proliferation and thymidine incorporation were induced by serum, epidermal growth factor, and insulin-like growth factor 1 but not by insulin. In contrast, at 25 mm glucose (HG), proliferation and thymidine incorporation were stimulated by insulin, serum, epidermal growth factor, and insulin-like growth factor 1 to a comparable extent, whereas basal levels were 25% lower than those in LG. HG culturing also enhanced insulin-stimulated insulin receptor and insulin receptor substrate 1 (IRS1) tyrosine phosphorylations while decreasing basal phosphorylations. These actions of glucose were accompanied by an increase in cellular tyrosine phosphatase activity. The activity of SHP-2 in HG-treated JAr cells was 400% of that measured in LG-treated cells. SHP-2 co-precipitation with IRS1 was also increased in HG-treated cells. SHP-2 was mainly cytosolic in LG-treated cells. However, HG culturing largely redistributed SHP-2 to the internal membrane compartment, where tyrosine-phosphorylated IRS1 predominantly localizes. Further exposure to insulin rescued SHP-2 cytosolic localization, thereby preventing its interaction with IRS1. Antisense inhibition of SHP-2 reverted the effect of HG on basal and insulin-stimulated insulin receptor and IRS1 phosphorylation as well as that on thymidine incorporation. Thus, in JAr cells, glucose modulates insulin mitogenic action by modulating SHP-2 activity and intracellular localization.

Smads in human trophoblast cells: expression, regulation and role in TGF-beta-induced transcriptional activity

Smad proteins have recently been shown to be downstream signaling molecules that transduce TGF-beta signals from cell surface to the nucleus. To determine the mechanisms of TGF-beta action in human trophoblast cells, we investigated the expression and regulation of Smad2,3,4, and 7 mRNAs in a normal trophoblast cell line, NPC, and a cell line derived from choriocarcinoma, JEG-3. Messenger RNAs for Smad2,3,4 and 7 were detected in both NPC and JEG-3 cells. TGF-beta1 induced modest increases in Smad2 and Smad4 mRNA levels without affecting Smad3 mRNA expression in both cell lines. Significant increases in Smad7 mRNA levels in both NPC and JEG-3 cells following TGF-beta1 treatment were observed. TGF-beta1 also induced promoter activity of the Smad7 gene, indicating a direct effect at the level of gene transcription. The transcriptional activity of TGF-beta was examined in JEG-3 cells using two TGF-beta responsive reporter constructs, p3TP-Lux and pAR3-Lux. We found that Smad3 and to a lesser extent, Smad2 and Smad4, enhanced, while Smad7 inhibited, TGF-beta1-induced transcriptional activities. The basal and TGF-beta1-induced transcription can be blocked by overexpression of a dominant negative TGF-beta type II receptor. Taken together, these findings demonstrate that in human trophoblast cell lines, the Smad pathway involved in TGF-beta signal transduction is functional and that TGF-beta plays an autocrine role in regulating gene expression.

A role for the homeobox protein Distal-less 3 in the activation of the glycoprotein hormone alpha subunit gene in choriocarcinoma cells

Synthesis and secretion of chorionic gonadotropin in trophoblast cells of the placenta is required for establishment of early pregnancy in primates. Chorionic gonadotropin is a heterodimeric glycoprotein hormone consisting of alpha and beta subunits. Regulation of the alpha subunit gene within the placenta requires an array of cis elements within the 5'-flanking region of the promoter. Within this array of elements, the junctional regulatory element (JRE) putatively binds a placental-specific transcription factor. The aim of our studies was to determine the identity and role of the transcriptional regulator that binds to the JRE in choriocarcinoma cells (JEG3 cells). Mutations within the JRE resulted in reduction in basal expression of an alpha subunit reporter gene, suggesting that the JRE binding factor was necessary for full basal activity. Using electrophoretic mobility shift assays, we determined that the JRE was capable of serving as a homeobox factor-binding site. The homeobox factor, Distal-less 3 (Dlx 3) was found to be expressed in JEG3 cells and in the trophoblast layer of human chorionic villus but not in a gonadotrope cell line that also expresses the alpha subunit gene. Electrophoretic mobility shift assays revealed that recombinant Dlx 3 could bind specifically to the JRE and endogenous Dlx 3 was present in JRE/JEG3 nuclear protein complexes. Overexpression of Dlx 3 resulted in activation of an alpha subunit reporter gene. A JRE mutation resulted in attenuated activation of the alpha subunit reporter via an adjacent cis element, suggesting that JRE/Dlx 3 interactions may facilitate regulation of the alpha subunit gene at sites immediately upstream of the JRE. Our studies support the conclusion that Dlx 3 is a placental-specific transcriptional regulator that binds to the JRE and contributes to expression of the alpha subunit gene in cells of trophoblast origin.

Endocrinology of the peri-implantation period

Current research suggests that the appearance of endometrial integrins and pinopode appearance signal the opening of the receptive phase of the endometrium. These integrins may be activated by the interleukin-1 system (IL-1). IL-1beta, expressed by the blastocyst, induces vascular endothelial growth factor (VEGF) which, in turn, promotes angiogenesis and integrin expression in endometrial cells. The IL-1 system also triggers the expression of gamma interferon (IFN-gamma) from T lymphocytes. Decidual natural killer (NK) lymphocytes interact with invading trophoblast to generate leukaemia inhibitory factor (LIF). LIF induces uPA and gelatinase, enzymes which play a crucial role in trophoblastic invasion. Progesterone is a potent inhibitor of LIF, while oestrogen is a potent inducer. Oestrogen in serum reflects follicular IL-1beta level and correlates with the outcome of embryo transfer after in vitro fertilization (IVF). Progesterone induces nitric oxide (NO) synthesis in the decidua, and NO promotes local vasodilatation and uterine quiescenceMeasurement of placental protein 14 (PP14, glycodelin-A) in serum may be of value as a screening test for implantation potential. However, human chorionic gonadotrophin (hCG) remains the most reliable predictor of successful implantation and pregnancy viability. An ovulation + 14 hCG level < 50 IU/l is often predictive of a non-viable outcome, while an ovulation + 21 hCG of < 200 IU/l always indicates a non-viable pregnancy. hCG secretion by invading trophoblast appears to be negatively modulated by endothelin-1 (ET-1) and prostaglandin F(2alpha)(PGF2alpha), while tissue growth factors and collagenases are positive modulators of hCG expression.ProalphaC, an inhibin pro-monomer, may have some value in monitoring corpus luteum function. Inhibin A, activin A and follistatin all rises throughout pregnancy and peak at 36 weeks of gestation. Relaxin is another ovarian hormone that may have a role in predicting implantation. Relaxin induces placental protein 14 (PP14, glycodelin-A) expression in a receptive endometrium, and measurement of serum PP14 may be of value as a screening test for implantation potential.

The role of insulin-like growth factor binding protein-1 phosphoisoforms in pregnancies with impaired placental function identified by doppler ultrasound

This study was performed to investigate the hypothesis that insulin-like growth factor binding protein-1 (IGFBP-1) is involved in the pathogenesis of trophoblast invasion and impaired placentation in human pregnancy. The role of total and non-phosphorylated IGFBP-1 in women with fetal growth restriction and in high risk pregnancies identified by uterine artery Doppler ultrasound screening was examined. This was a prospective study of women booked for antenatal care having second trimester anomaly scans and Doppler screening between 22-26 weeks gestation. Women were divided into three groups and compared: normal uterine artery Doppler and normal fetal growth (control group, n = 10); abnormal Doppler and normal fetal growth [bilateral uterine artery notches (BN; n = 16); abnormal Doppler and intrauterine growth restriction (IUGR; n = 8)]. Maternal serum was collected, stored and assayed simultaneously for total and non-phosphorylated IGFBP-1. There was elevated total and non-phosphorylated IGFBP-1 (mean 44.99 +/- 12.19 and 29.61 +/- 10.38 microg/l respectively) in the IUGR group compared with controls (mean 17.96 +/- 3.24 and 12.18 +/- 1.55 microg/l, P < 0.05). This finding suggests that the various IGFBP-1 isoforms, the degree of phosphorylation and the ratios of these different forms locally may be important during trophoblast invasion and may be implicated in clinical manifestations of impaired placentation later in the second trimester.