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PubMed1999

Hepatocyte growth factor stimulates trophoblast invasion: a potential mechanism for abnormal placentation in preeclampsia.

Hepatocyte growth factor (HGF) is a cytokine that is produced in the placental villous core and acts in a paracrine manner on trophoblasts that express the HGF receptor Met. Because HGF stimulates the invasion of many epithelial cell types, villous core HGF could regulate placental trophoblast invasion. As preeclampsia is characterized by inadequate trophoblast invasion, we investigated the hypothesis that decreased placental HGF production is a mechanism for inadequate trophoblast invasion in this disease. Placental villous explant HGF production over 24 h was 25% lower in patients with preeclampsia (n = 5; 7.29 +/- 0.8 ng/mL) than in normal patients (n = 5; 9.76 +/- 0.5 ng/mL; P < 0.05). The human first trimester trophoblast cell line (ED27) used in subsequent invasion studies was found to express c-met messenger ribonucleic acid by RT-PCR and Met protein by Western analysis, and underwent phosphorylation of tyrosine residues on Met with HGF exposure. A Boyden chamber invasion assay using collagen type I showed that HGF caused a specific dose-response increase in trophoblast invasion first seen at 10 ng/mL (2.2-fold increase; P < 0.05). The stimulation of trophoblast invasion by HGF may in part be due to the 2-fold induction of 92-kDa collagenase as determined by zymogram analysis of the trophoblast-conditioned medium. These studies suggest that HGF has an important role in placental trophoblast invasion through the activation of Met and the subsequent induction of 92-kDa collagenase in these cells. In addition, decreased placental production of HGF in preeclampsia provides a potential mechanism for the lack of trophoblast invasion that is seen in this pregnancy disorder.

Blotting, Western↗
PubMed2000

Peroxisome proliferator-activated receptor-gamma modulates differentiation of human trophoblast in a ligand-specific manner.

The ligand-dependent nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) regulates the differentiation of several tissues and cell types. PPARgamma was recently determined to be essential for murine placental development and differentiation. We therefore assessed the influence of PPARgamma on differentiation of human placental trophoblasts. We initially used immunohistochemistry to examine term human placentas for PPARgamma expression and found that PPARgamma is present in syncytiotrophoblasts and cytotrophoblasts in placental villi. We correlated the expression of PPARgamma with differentiation of primary human trophoblasts and found that 8-bromo-cAMP, a known enhancer of trophoblast differentiation, stimulates PPARgamma activity, but has no effect on PPARgamma expression. We demonstrated that the PPARgamma ligand 15-deoxy-delta12,14-prostaglandin J2 (15deltaPGJ2) and the thiazolidinedione troglitazone stimulate PPARgamma activity in the trophoblast cell line BeWo. Importantly, whereas exposure of cultured primary trophoblasts to troglitazone enhances biochemical and morphological trophoblast differentiation, 15deltaPGJ2 diminishes trophoblast differentiation. Furthermore, 15deltaPGJ2, but not troglitazone, up-regulates p53 expression and promotes trophoblast apoptosis. These data indicate that PPARgamma is expressed in human placental trophoblasts, and that ligand-specific activation of PPARgamma results in opposing effects on trophoblast differentiation. Our results suggest that PPARgamma plays an important role in placental differentiation during human pregnancy.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

Paracrine activities of porcine trophoblastic interferons.

Interferon-gamma (IFN-gamma) and a type I IFN (spI IFN) are transiently coexpressed by trophoblastic cells of pig conceptuses at implantation between day 12 and day 20 of gestation. The local effects of these trophoblastic IFNs were examined on endometrial cells and on trophoblast by measuring antiviral activity and the induction of (2',5')-oligoadenylate synthetase activity. Trophoblastic vesicles were shown to be susceptible to infection by vesicular stomatitis virus and transmissible gastroenteritis virus. Vesicular stomatitis virus multiplied by about 1000 times in trophoblastic vesicles, and endogenous trophoblastic IFNs or exogenous recombinant IFN-gamma or spI IFN had no effect on virus production. No (2',5')-oligoadenylate synthetase activity could be measured on the trophoblast, even after treatment with IFN-gamma or spI IFN. These results clearly show that trophoblastic IFNs cannot induce antiviral resistance or (2',5')-oligoadenylate synthetase activity in the trophoblast, suggesting that these IFNs have no autocrine function. Endometrial epithelial and stromal cells in primary cultures displayed distinct sensitivity to the antiviral effect of IFN-gamma and spI IFN. Stromal fibroblasts were highly sensitive to spI IFN but weakly sensitive to IFN-gamma; epithelial cells were sensitive to both IFNs. The same sensitivity pattern was obtained when measuring the (2',5')-oligoadenylate synthetase activity. Flushing fluid, containing IFN-gamma and type I IFN, was a potent inducer of antiviral effect and (2',5')-oligoadenylate synthetase activity. It is therefore postulated that the endometrial epithelium is the most likely target of trophoblastic IFNs. It is possible that these IFNs play a role in the viral protection of conceptuses.

2',5'-Oligoadenylate Synthetase↗
PubMed1994

Involvement of epidermal growth factor (EGF)/EGF receptor autocrine and paracrine mechanism in human trophoblast cells: functional differentiation in vitro.

We have studied the expression of epidermal growth factor (EGF) and EGF receptors (EGF-R) in isolated human trophoblast cells at various stages of differentiation and also the biological significance of the EGF/EGF-R autocrine and paracrine mechanism. Cytotrophoblast cells were isolated from human placental tissues of 6-9 weeks of gestation. Trophoblast cells underwent morphological and functional differentiation during in vitro culture. The expression of EGF and EGF-R protein and mRNA was studied in trophoblast cells cultured for 0-5 days, using immunocytochemical staining, and reverse transcription and polymerase chain reaction. Monoclonal antibodies (mAbs) against EGF and EGF-R showed specific staining in trophoblast cells at all stages of differentiation. Both EGF and EGF-R gene transcripts were detected in RNA samples isolated from trophoblast cells at all stages. These data suggest the presence of an EGF/EGF-R autocrine and paracrine mechanism in human trophoblast cells. Next, we examined the biological significance of this mechanism on trophoblast cell differentiation in vitro. EGF added to the culture medium significantly increased human chorionic gonadotrophin-beta (hCG-beta) secretion and, more importantly, anti-EGF neutralizing mAbs significantly reduced both hCG-beta and human placental lactogen secretion from trophoblast cells in culture. All these results suggest that human trophoblast cells express both EGF and EGF-R, and that EGF may play an important role in the functional differentiation of human trophoblast cells.

Base Sequence↗
PubMed1990

Identification of class I MHC mRNA in human first trimester trophoblast cells by in situ hybridization.

Special gestation-related regulatory mechanisms for the expression of class I Ag by trophoblast cells directly exposed to maternal blood and tissues may be required for semiallogeneic pregnancy to be successful. Analysis of class I MHC mRNA by in situ hybridization and class I MHC Ag by immunohistology has revealed two phenotypically distinct subpopulations of trophoblast cells in term placentas and extraplacental membranes. Trophoblast cells external to the placenta are mRNA +/Ag+. They contain class I mRNA and express class I Ag that differ serologically from HLA-A,B,C. In contrast, trophoblast cells forming the syncytial layer of placental villi are mRNA-/Ag-. By immunohistology, trophoblast cells in 1st trimester placental tissues are similar to those in term tissues. In our study, in situ hybridization was used to determine if patterns of trophoblast cell class I mRNA were the same or different. Trophoblast cells external to the placental villi in 1st trimester tissues contained class I mRNA as would be predicted from the results with term tissues. Unexpectedly, class I mRNA was found in villous trophoblast cells. Thus, these studies identified an mRNA+/Ag- trophoblast cell subpopulation. The results suggest that tissue-specific mechanisms may interfere with translation of class I mRNA in 1st trimester villous trophoblast cells and/or that the protein products of the mRNA are not identified by available mAb.

Female↗
PubMed1989

Trophoblast invasion during implantation of the mouse embryo.

The interaction between trophoblastic and maternal cells was analysed by electron microscopy on days 6, 7 and 8 of pregnancy, in the mouse. Special emphasis was given to phagocytic activity and invasiveness by the trophoblast. On the sixth day of pregnancy, the trophoblast cells are in contact with the epithelial cells of the implantation crypt, with the basal lamina of the crypt, and with cells of the antimesometrial decidua. On the seventh and eighth days of pregnancy, the trophoblastic cells interact with those of the antimesometrial decidua. The giant trophoblastic cells engulf epithelial cells, maternal blood cells and decidual cells although the pattern of phagocytosis of these structures differs. Both whole epithelial cells and blood cells were ingested. The epithelial cells were deteriorated whereas the blood cells had a normal morphology; the decidual cells were ingested following a severe process of deterioration. Processes of trophoblastic cells interposed between the epithelium of the implantation crypt and its basal lamina seem to contribute to the displacement of the epithelial cells. The invasion of the endometrium by the trophoblast begins with the penetration by processes of trophoblastic cells between the decidual cells. The contact between the surface of both cell types may be very close: adherens type junctions and focal contacts are formed between trophoblastic cells and healthy decidual cells. Trophoblastic cells ingest deteriorated or fragmented cells and gradually occupy the spaces left by the latter.

Animals↗
PubMed1987

Normal trophoblasts resist induction of class I HLA.

Very few types of normal cells fail entirely to express class I human leukocyte antigens (HLA), and many of those cells (sperm, fetal amnion epithelial cells, and fetal trophoblasts) are related to the process of reproduction. Susceptibility of sperm to modulation of class I antigens has not been examined, but it has recently been demonstrated that amnion cells respond to exposure to IFN-gamma with readily detectable levels of class I antigens. In addition, one of two trophoblast cell lines (BeWo) has been shown to exhibit enhanced expression of class I HLA in response to IFN-gamma. Expression by a second trophoblast cell line (Jar) was not inducible. Findings in the present study included demonstration of IFN-gamma-enhanced class I-specific mRNA synthesis in JEG-3 cells, which are derived from BeWo, and failure of synthesis by Jar cells. Those results eliminated trivial explanations for the preceding findings and confirmed the responsiveness of some but not all cells of trophoblast origin to IFN-gamma. When successful modulating conditions for amnion and malignant trophoblast cells were applied to normal tissues, third trimester term chorionic cytotrophoblasts and first trimester villous syncytial and cytotrophoblasts failed to exhibit class I HLA. Neither malignant nor normal trophoblasts expressed class II HLA under any condition of testing. Failure of induction of HLA expression by normal trophoblasts could not be attributed to either loss of viability by tissue explants or failure of modulating reagents to reach the trophoblasts. The results demonstrate that regulation of expression of histocompatibility antigens by major populations of normal trophoblasts and one of two choriocarcinoma cell lines differs markedly from that of other fetal and adult cells. Uncommon regulatory mechanisms may be essential to maintenance of the trophoblast as an immunologically inert barrier between the mother and her antigenically disparate fetus.

Antigens, Neoplasm↗
PubMed1994

Expression of c-erb B-2 oncogene product in persistent gestational trophoblastic disease.

OBJECTIVE: Much debate exists on the initiation of chemotherapy for women at risk for persistent gestational trophoblastic disease. This is a result of a lack of early predictors for the development of persistent gestational trophoblastic disease after evacuation of a complete hydatidiform mole, because the only current reliable method of detection and diagnosis lies in persistent or rising postmolar beta-human chorionic gonadotropin values. We used immunocytochemical techniques to retrospectively study the expression of the c-erb B-2 oncogene product in formalin-fixed, paraffin-embedded trophoblastic tissues as a potential indicator of the development of persistent gestational trophoblastic disease. STUDY DESIGN: In this retrospective study 56 trophoblastic tumors were examined by means of immunocytochemical techniques to stain for the oncogene product for evidence of c-erb B-2 expression. Our 56 cases included original tissue from 20 cases of complete mole that progressed to persistent gestational trophoblastic disease, seven cases of choriocarcinoma after term pregnancy or abortion, and 29 cases of hydatidiform mole representing postevacuation, spontaneously regressing disease (including one partial mole). We also studied 11 cases of first-trimester trophoblast and 15 cases of term placenta as additional controls. RESULTS: Our results showed positive immunostaining for c-erb B-2 gene product in one case of persistent gestational trophoblastic disease, with negative staining in all other cases in the study groups and controls. CONCLUSION: Analysis for the significance of c-erb B-2 expression in persistent gestational trophoblastic disease showed that this correlation between c-erb B-2 expression and persistent gestational trophoblastic disease is not significant, suggesting that future efforts should be directed at the involvement of different oncoproteins.

Biomarkers, Tumor↗
PubMed1997

Role of VEGF receptor-1 (Flt-1) in mediating calcium-dependent nitric oxide release and limiting DNA synthesis in human trophoblast cells.

Vascular endothelial growth factor (VEGF) receptor KDR (kinase-insert-domain-containing receptor) is linked to endothelial cell proliferation, and VEGF receptor Flt-1 (fms-like tyrosine kinase) is essential for the organization of embryonic vasculature. Flt-1 is also known to be expressed on adult endothelial and trophoblast cells, although its function has not yet been established. Herein we report that human trophoblast and endothelial cells contain functional Flt-1 receptors for VEGF that trigger the synthesis and release of nitric oxide (NO) by the activation of constitutive NO synthase (cNOS). In first-trimester human trophoblast cells isolated by chorionic villous sampling, VEGF165 stimulated NO release in a concentration- and time-dependent manner, with a maximal increase of 60% (in comparison to basal release levels) occurring within 30 minutes (basal: 1342 pmol/ml; VEGF (10 ng/ml): 2162 pmol/ml; p < 0.001), as measured by an NO chemiluminescence analyzer. VEGF20, a peptide fragment that is composed of the first 20 amino acids at N-terminus, displayed properties of a partial agonist. VEGF165- and VEGF20-mediated NO biosynthesis was attenuated by NG-nitro-L-arginine in a concentration-dependent fashion, indicating NOS activation. VEGF-neutralizing anti-VEGF monoclonal antibody significantly inhibited VEGF-mediated NO release (p < 0.001), and the addition of a neutralizing anti-Flt-1 antibody inhibited the response by 79.6% +/- 7.59%, an effect found to be reversible with higher concentrations of VEGF. In contrast, anti-KDR antibody had no significant inhibitory effect. RT-PCR confirmed the presence of mRNA encoding the Flt-1 and KDR receptors as well as the endothelial form of cNOS in trophoblast cells. VEGF165-stimulated NO release was inhibited by genistein (5 microM; p < 0.001) as well as by the removal of calcium from the extracellular environment (p < 0.001), which suggests the contingency of this process on tyrosine phosphorylation and extracellular calcium, respectively. Addition of sodium nitroprusside, an NO donor, inhibited trophoblast DNA synthesis in a concentration-dependent manner, as measured by [3H]thymidine incorporation, without affecting cell viability. VEGF under maximal NO production had no mitogenic activity, suggesting that trophoblast-derived NO may limit trophoblast proliferation. Endogenous trophoblast DNA synthesis increased 3-fold in the presence of anti-Flt-1 antibody but not in the presence of anti-KDR antibody, suggesting that Flt-1 functions as a growth suppressive receptor to counteract the proliferative actions of KDR. Levels of immunoreactive endothelial cNOS were markedly increased in growth-restricted placentae (n = 4) in comparison to those of normal (n = 5) placentae, which may account for the relatively small-sized placentae associated with intrauterine growth restriction. VEGF165 stimulated NO release via phosphorylation of the Flt-1 receptor, indicating that VEGF may be an autocrine regulator of NO biosynthesis by aiding trophoblast penetration into spinal arterioles during the first trimester and preventing platelet aggregation within the placenta. Finally, the activation of Flt-1 receptor suppressed trophoblast DNA synthesis within the placenta via NO.

Calcium↗
PubMedDate not supplied

Mouse trophoblastic cell lines: I--Relationship between invasive potential and TGF-beta 1.

In the present study five mouse trophoblastic cell lines were used, SM9-1, SM9-2 and SM10 from outbred (Swiss) mice, and HLA-B1 and HLA-B3 from inbred transgenic (HLA-B27) mice placentas generated in the laboratory of Dr. Joan S Hunt (K U Medical Center, Kansas City, KS). All of the cell lines demonstrated a basic set of characteristics that are strongly associated with and probably exclusive to trophoblast cells. Successful propagation of normal trophoblast cell lines with distinct phenotypes cultured in vitro provides an excellent model for the study of mechanisms regulating trophoblast invasion very similar to invasion by tumor cells. Application of these cells to in vitro invasion assay has uncovered some of the molecular mechanisms responsible for trophoblast invasiveness and its control. Using the in vitro invasion assay SM9-2 and SM-10 were identified as the most invasive and least invasive cell lines, respectively. By using RT-PCR we have shown that all lines express TNF-alpha mRNA and this level is high in HLA-B derived cell lines. Other experiments has revealed that only Swiss mice derived cell lines (SM9-1, SM9-2 and SM-10) express the TGF-beta 1 mRNA and among these lines SM9-2 has the highest level. In TGF-beta 1 activity assay, secreted conditioned medium of these cell lines further showed that SM9-2 line has the highest inhibitory activity on Mv-1-Lu cell line. Exogenous TGF-beta 1 down-regulates invasion as well as mRNA level in SM9-2 trophoblasts. However, neutralizing TGF-beta 1 antibody in this cell line up-regulates invasion minimally. Late gestational trophoblast cells show a major reduction of invasive ability which is an autocrine type negative regulation of trophoblast invasion, and is possibly mediated by TGF-beta 1 production by the trophoblasts. Thus trophoblast TGF-beta 1 could be implicated in the invasion of these cells and this invasive phenotype is retained with complete fidelity during their further propagation in culture.

Alkaline Phosphatase↗
PubMed1988

Cross-reactivity of monoclonal antibodies directed against lymphocyte markers with trophoblast cells of normal placenta, hydatidiform mole, and gestational choriocarcinoma.

The current study was undertaken to characterize the expression of trophoblast-lymphocyte cross-reactive antigens on normal, molar, and malignant trophoblast. A panel of monoclonal antibodies directed against lymphoid cell markers were tested in immunofluorescence assay on cryostat sections of placenta and mole and on monolayers of choriocarcinoma cells. NKH-1, a monoclonal antibody to natural killer cells, reacted with both molar and placental villous trophoblast and with two choriocarcinoma cell lines. NKH-2, a monoclonal antibody reactive with a subset of natural killer cells, did not react with placental villous trophoblast but reacted with molar villous trophoblast in three of five moles tested and with both choriocarcinoma cell lines. B5, a monoclonal antibody which reacts with activated B cells, reacted with both choriocarcinoma cell lines but did not react with normal placental or molar trophoblast. MY7, a monoclonal antibody to myeloid colony-forming cells, reacted with only one of the choriocarcinoma cell lines. Trophoblast-lymphocyte cross-reactive antigens may be important in the immunobiology of gestational trophoblastic disease by modulating interactions between the trophoblast and the maternal immune system.

Antibodies, Monoclonal↗
PubMed2000

[Pathology of gestational trophoblastic tumors].

Gestational trophoblastic tumours result from an abnormal proliferation of different types of trophoblasts. The morphological pattern, together with the immunohistochemical aspect, the cytogenetic data and the clinical profile, helps identify each pathological entity. Hydatiform moles represent malformed placentas caused by genetic aberrations of the villous trophoblast. A complete hydatiform mole displays an hydropic degeneration of all the chorionic villi with a more or less marked proliferation of trophoblasts. A partial hydatiform mole is made up of molar vesicles interspersed with normal chorionic villi. In an invasive hydatiform mole or chorioma destruens, molar vesicles penetrate the myometrium giving rise to a mass distorting the uterine wall. A choriocarcinoma is a malignant proliferation of atypical villous trophoblasts without villi formation. Necrosis, haemorrhage, vascular invasion and distant metastases strongly compromise its outcome. A trophoblastic implantation site tumor, clearly less frequent, results from a proliferation of extravillous trophoblasts, particular for their secretion of human placental lactogen hormone (hPL). This tumour, exceptionally malignant, should be differentiated from the exaggerated placental site and its variants. Except for the placental site trophoblastic tumour, and whatever the outcome (benign or malignant), all gestational trophoblastic tumours secrete the beta-subunit of the chorionic gonadotropic hormone (beta-hCG) more or less abundantly. The serum or urinary level of this unit is proportional to the tumour volume and represents a fundamental basis for the follow-up of these tumours. Multidisciplinary care of high-risk cases allows us to cure the disease, and helps the patient recover her reproductive uterine function.

Chorionic Gonadotropin, beta Subunit, Human↗
PubMed2002

Molecular basis of gestational trophoblastic diseases.

Gestational trophoblastic disease (GTD) encompasses a diverse group of lesions with specific pathogenesis, morphological characteristics and clinical features. The modified World Health Organization-classification of GTD includes complete and partial hydatidiform mole, invasive mole, choriocarcinoma, placental site trophoblastic tumor, epithelioid trophoblastic tumor, exaggerated placental site, and placental site nodule. The various forms of gestational trophoblastic disease can be defined and related to discrete pathologic aberrations occurring at different stages of trophoblastic differentiation. Some of these lesions are true neoplasms, whereas others represent abnormally formed placentas with a predisposition for neoplastic transformation of the trophoblast. Except hydatidiform moles in which the cytogenetic studies have been extensively reported, the pathogenesis of other trophoblastic lesions is poorly understood. Recent studies have shed light on the molecular mechanisms of trophoblastic function, especially as it relates to trophoblastic disease. This review will focus on these advances with special emphasis on the pathogenesis of each specific form of GTD. In addition, the morphology and clinical behavior of each of these entities will be briefly discussed.

Blastocyst↗
PubMed1996

[The early placental trophoblast. I. Normal development and endometrial and non-tumor-induced disorders].

The development of the hemochorial placenta requires, that the trophoblast invades the endometrium, penetrating into its deep layers and blood vessels. Placental tissue includes components from two haplodifferent organisms, the mother and the fetus. Early steps in trophoblastic development are the adhesion and apposition. Invasion is an active process and correlations are observed between cellular invasivness and proteinase production, like uPA, tPA and its inhibitors, for example PAI-1. The process of trophoblast invasion is based on a complex interaction between the trophoblastic cells, various types of matrices and decidual as well as endometrial cells. Immunologic processes, like the production of blocking factors, paraimmune mechanisms and other HLA-dependent processes play an important role. During implantation a differentiation of trophoblastic cells takes place. The syncytiotrophoblast is the active cell of the invasive previllous trophoblast. The intermediate trophoblast plays this role concerning the villous trophoblast. The different trophoblastic cells are characterised by distinct morphologic and immunohistochemical features.

Chorionic Villi↗
PubMed1997

Expression of platelet-endothelial cell adhesion molecule-1 (PECAM) by macaque trophoblast cells during invasion of the spiral arteries.

BACKGROUND: Placental development in higher primates is characterized by the invasion of uterine blood vessels by trophoblast cells. These cells proceed to migrate within uterine spiral arteries, opposite to the direction of normal blood flow. Observations indicate adhesion of intra-arterial trophoblast to endothelium as well as to adjacent trophoblast cells. METHODS: Macaque placenta and endometrial tissues were collected from day 15 of pregnancy (implantation begins on day 9) to term. Standard indirect immunoperoxidase methods were used to identify platelet-endothelial cell adhesion molecule-1 (PECAM), cytokeratins, and factor VIII-related antigen. RESULTS: In early specimens arterioles were often nearly occluded by cytokeratin-labeled trophoblast cells. Adjacent sections revealed the presence of PECAM on these trophoblast cells and on the endothelium. After day 30 the invaded arteries usually contained a re-formed lumen, and trophoblast cells were increasingly evident in the modified walls of arteries, where PECAM labeling was often reduced on cells distant from the lumen. Endothelium of both invaded and uninvaded uterine vessels retained PECAM reactivity throughout gestation. Trophoblast cells of the cell columns, cytotrophoblastic shell, and mid- to late-gestation chorionic plate were also reactive for PECAM. Villous cytotrophoblast cells did not express PECAM, but a dense border of PECAM was consistently present on the apical surfaces of syncytial trophoblast. CONCLUSIONS: Because PECAM functions as a counter-ligand for PECAM via homophilic binding, we conclude that this molecule is directly involved in adhesion of trophoblast cells to arterial endothelium in addition to maintaining cohesion between some subpopulations of cytotrophoblast cells.

Animals↗
PubMed1998

Absence of MHC class II antigen expression in trophoblast cells results from a lack of class II transactivator (CIITA) gene expression.

Although the mechanism(s) underlying the failure of the maternal immune system to reject the semiallogeneic fetus have not been clearly defined, the absence of MHC class II antigen expression by fetal trophoblast cells very likely plays a critical role in the maintenance of normal pregnancy. However, the regulation of class II antigen expression in trophoblast cells is poorly understood. Class II transactivator (CIITA) is a transacting factor that is required for both constitutive and IFN-gamma-inducible class II gene transcription. In this report we demonstrate that the inability of trophoblast cells to express class II antigens is due to a lack of CIITA gene expression. Trophoblast cell lines derived from human, mouse, and rat do not express CIITA, and expression is not inducible by IFN-gamma. The absence of CIITA gene expression in trophoblasts treated with IFN-gamma does not result from a defect in the IFN-gamma receptor or the JAK/STAT pathway, because the classical IFN-gamma inducible gene encoding the guanylate-binding protein is expressed. Transfection of CIITA expression vectors into trophoblast cells results in activation of class II promoters, endogenous class II mRNA expression, and subsequent expression of class II antigens on the cell surface. In contrast, class I mRNA is not expressed in human trophoblast cells transfected with CIITA expression vectors. Thus, trophoblast cells contain all of the DNA binding factors necessary for class II transcription, and ectopic expression of CIITA is sufficient to activate class II, but not class I expression. The failure of trophoblast cells to express CIITA, and therefore class II antigens, provides a potential mechanism by which the fetus is protected from the maternal immune system during pregnancy.

Animals↗
PubMed2001

Trophoblast-specific expression and function of the integrin alpha 7 subunit in the peri-implantation mouse embryo.

For implantation and placentation to occur, mouse embryo trophoblast cells must penetrate the uterine stroma to make contact with maternal blood vessels. A major component of the uterine epithelial basement membrane and underlying stromal matrix with which they interact is the extracellular matrix protein laminin. We have identified integrin alpha 7 beta 1 as a major receptor for trophoblast-laminin interactions during implantation and yolk sac placenta formation. It is first expressed by trophectoderm cells of the late blastocyst and by all trophectoderm descendants in the early postimplantation embryo through E8.5, then disappears except in cells at the interface between the allantois and the ectoplacental plate. Integrin alpha 7 expression is a general characteristic of the early differentiation stages of rodent trophoblast, given that two different cultured trophoblast cell lines also express this integrin. Trophoblast cells interact with at least three different laminin isoforms (laminins 1, 2/4, and 10/11) in the blastocyst and in the uterus at the time of implantation. Outgrowth assays using function-blocking antibodies show that alpha 7 beta 1 is the major trophoblast receptor for laminin 1 and a functional receptor for laminins 2/4 and 10/11. When trophoblast cells are cultured on substrates of these three laminins, they attach and spread on all three, but show decreased proliferation on laminin 1. These results show that the alpha 7 beta 1 integrin is expressed by trophoblast cells and acts as receptor for several isoforms of laminin during implantation. These interactions are not only important for trophoblast adhesion and spreading but may also play a role in regulating trophectoderm proliferation and differentiation.

Alternative Splicing↗
PubMed1998

Expression of metalloproteinases and their inhibitors in human trophoblast continuous cell lines.

Trophoblasts cells which are derived from the outer layer of the blastocyst have developed mechanisms by which they can invade the uterus and tap into the maternal circulation. In contrast to tumor cell invasion trophoblast invasion is precisely regulated, being confined spatially to the uterus and temporally to early pregnancy. The invasive properties manifested by trophoblasts are made possible by the secretion of proteolytic enzymes which can degrade components of the extracellular matrix (ECM). A number of investigators have shown that the matrix metalloproteinases (MMPs) are important mediators of trophoblast invasion. The two type IV collagenases, MMP-2 and MMP-9, which specifically degrade type IV collagen and gelatins have been of particular interest in this respect. In this paper we examine the expression and regulation of MMPs and their inhibitors in a series of trophoblast continuous cell lines. These cell lines, ED27, ED31, ED77, and a choriocarcinoma cell line, BeWo, were initially characterized with respect to various properties, including cytokeratin, hCG, and hPL expression. We have looked at the expression of MMPs and their inhibitors in these cell lines and their in vitro invasive behavior. Using zymography and RT-PCR we show that the trophoblast cell lines produce both MMP-2 and MMP-9, while the BeWo produce only MMP-2. Using an in vitro invasion assay the trophoblast cell lines were shown to be capable of invading while the BeWo were unable to invade. These results suggest that expression of MMP-9 in these cells is crucial for invasion. We have also examined the regulation of MMP expression by cytokines and found that MMP-9 expression could be modulated by IL-1 beta in these cell lines. The data presented in this paper suggest that these trophoblast cell lines present an ideal model system to investigate the regulation of metalloproteinases in trophoblast invasion.

Cell Line↗