Normal Syncytiotrophoblast Research Articles

Expression levels of cyclooxygenase-2, tumor necrosis factor-α and inducible NO synthase in placental tissue of normal and preeclamptic pregnancies

Objective: Although preeclampsia (PE) is one of the most important problems affecting pregnant women, etiologic factors in its development are still unclear. We aimed to investigate the expression levels of cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α) and inducible NO synthase (iNOS) in preeclamptic and healthy control placentas. Patients and methods: Placental tissue samples were obtained after delivery from patients diagnosed with PE and from normal-term pregnants and analyzed for COX-2, TNF-α and iNOS expression by immunohistochemistry. Results: A strong expression of COX-2 was observed in syncytiotrophoblast cells of preeclamptic placentas, which was significantly higher than that of normal placentas (p = 0.005). A mild expression of TNF-α in both normal and preeclamptic syncytiotrophoblasts was seen (p = 0.435). In addition, a strong expression of iNOS in normal syncytiotrophoblasts was found, but the intensity of the iNOS expression was highly reduced in preeclamptic placentas (p = 0.001). No correlation was detected between COX-2, TNF-α and iNOS expression levels. Conclusion: The findings of a decrease of iNOS expression and an increase of COX-2 expression in placenta suggest the existence of functional roles of iNOS and COX-2 in the pathophysiology of PE, probably by contributing to the reduced placental blood flow and increased resistance to flow in the fetomaternal circulation.

P45NF-E2 represses Gcm1 in trophoblast cells to regulate syncytium formation, placental vascularization and embryonic growth

Absence of the leucine zipper transcription factor p45NF-E2 results in thrombocytopenia, impaired placental vascularization and intrauterine growth restriction (IUGR) in mice. The mechanism underlying the p45NF-E2-dependent placental defect and IUGR remains unknown. Here, we show that the placental defect and IUGR of p45NF-E2 (Nfe2) null mouse embryos is unrelated to thrombocytopenia, establishing that embryonic platelets and platelet-released mediators are dispensable for placentation. Rather, p45NF-E2, which was hitherto thought to be specific to hematopoietic cells, is expressed in trophoblast cells, where it is required for normal syncytiotrophoblast formation, placental vascularization and embryonic growth. Expression of p45NF-E2 in labyrinthine trophoblast cells colocalizes with that of Gcm1, a transcription factor crucial for syncytiotrophoblast formation. In the absence of p45NF-E2, the width of syncytiotrophoblast layer 2 and the expression of Gcm1 and Gcm1-dependent genes (Synb and Cebpa) are increased. In vitro, p45NF-E2 deficiency results in spontaneous syncytiotrophoblast formation, which can be reversed by Gcm1 knockdown. Increased Gcm1 expression in the absence of p45NF-E2 is dependent on enhanced protein acetylation, including post-translational modification of Gcm1. Increasing and inhibiting acetylation in the placenta of wild-type control embryos phenocopies and corrects, respectively, the changes observed in p45NF-E2-deficient embryos. These studies identify a novel function of p45NF-E2 during placental development: in trophoblast cells, p45NF-E2 represses Gcm1 and syncytiotrophoblast formation via acetylation.

Reduced l-arginine Level and Decreased Placental eNOS Activity in Preeclampsia

Nitric oxide is produced enzymatically by the nitric oxide synthase (NOS), which converts L-arginine in the presence of oxygen to L-citrulline and NO. Moreover, it has been reported that asymmetric dimethylarginine (ADMA) acts as is an endogenous inhibitor of endothelial NOS (eNOS) by competing with the enzyme for L-arginine. In this study, we measured L-arginine and ADMA in normal and preeclamptic women, and also investigated the association between the Glu298Asp eNOS gene polymorphism and preeclampsia. Finally, we assessed eNOS expression levels in the placentas of both normal and preeclamptic patients, using Western blot and immunohistochemistry. L-arginine levels were found to be significantly lower in the preeclamptic women than in the normal pregnant women (p=0.02) but there were no significant differences in ADMA levels between the normal and preeclamptic women. We also determined there to be no association between the Glu298Asp eNOS gene and preeclampsia. With regard to placental eNOS expression, we detected a lower degree of eNOS expression in the preeclamptic syncytiotrophoblasts than in the normal syncytiotrophoblasts. We suggest that reduced L-arginine levels, rather than increased ADMA levels, contribute to the development of preeclampsia, and also that decreased placental eNOS expression constitutes a characteristic finding in preeclamptic placentas.

Ultrastructural study on human placenta from intrauterine growth retardation cases

A morphological study was performed on 27 human placentas from normal gestations (Group 1) and compared with those from eight cases of intrauterine growth restriction (IUGR) (Group 2). Semithin section light microscopy, transmission, and scanning electron microscopy were carried out on trophoblastic terminal villi, carefully identified under the stereomicroscope. In growth retardation cases, villi appear longer, thinner, and less vascularized, compared to the normal condition. Fibrinoid, an extracellular material of hematic origin, frequently fills villar stroma. The density of apical microvilli appears considerably reduced and occasional microvilli-free areas are observed in growth retardation cases. Moreover, the underlying basal membrane appears significantly thicker than that of normal syncytiotrophoblast. Recently, particular attention has been paid to apoptosis as a possible cell deletion mechanism in growth restriction. In our study, a majority of typical apoptotic features appear indifferently in both IUGR and normal pregnancy. Our data hints that growth retardation might be correlated with a complex of structural changes, suggestive of maternofetal traffic downregulation, but further studies are required to understand the underlying functional mechanisms.

The Human Endogenous Retrovirus ERV-3 Is Upregulated in Differentiating Placental Trophoblast Cells

The single copy endogenous retrovirus locus ERV-3 is known to be primarily expressed in the placenta. The absence of expression of this gene in choriocarcinoma cell lines has led to speculation that this may be a defect associated with this abnormality. We show here that ERV-3 is not normally expressed in the cytotrophoblast from which these tumour cells are derived but is expressed in normal syncytiotrophoblast. The conservation of the ERV-3 open reading frame for env in ape and old world monkey species and its tight regulation and site of expression suggest a functional role for this gene in this tissue.

Monoclonal antibody defining a human syncytiotrophoblastic polypeptide immunologically related to mammalian retrovirus structural protein p30

Antigenic material previously detected in human placental trophoblastic cells by immunoperoxidase staining using a goat antiserum against the feline RD114 retrovirus structural protein p30 was isolated by immunochromatography from normal syncytiotrophoblast. The antigen was used to immunize mice, and of the monoclonal antibodies produced by murine hybridomas an IgG1 was selected which reacted in enzyme immunoassay with the syncytiotrophoblast antigen and with purified RD114. This antibody, designated HPS-1, stained normal and neoplastic syncytiotrophoblasts in a manner similar to that of the goat antibodies, detected in immunoblotting a Mr = 130 000 polypeptide in cultured human choriocarcinoma cells and reacted in spot immunoblotting tests with purified preparations of mammalian retroviruses but not with an avian retrovirus. The polypeptide antigen may represent activation of human endogenous retroviral genes in syncytiotrophoblast.

Immunohistochemical demonstration of relaxin in gynecologic tumors.

The immunoperoxidase technique was utilized to study the occurrence and localization of relaxin in malignant and nonmalignant trophoblastic disease and nontrophoblastic gynecologic cancer. Tissue specimens were studied from normal placenta at various weeks of gestation (N = 10), hydatidiform mole (N = 10), invasive mole (N = 10), choriocarcinoma (N = 10), normal endometrium (N = 28), decidua (N = 5), adenocarcinoma of the endocervix (N = 10), of the endometrium (N = 10), corpus luteum (N = 2), ovarian serous papillary cystadenocarcinoma (N = 10), and mucinous cystadenocarcinoma (N = 10). Relaxin was identified in the syncytiotrophoblast of normal placenta at all stages of gestation and also, for the first time, in hydatidiform mole, invasive mole, and choriocarcinoma. No relaxin was found in any nontrophoblastic cancer, including secretory-type adenocarcinoma. The absence of relaxin in the secretory-type endometrial adenocarcinoma is intriguing in light of the finding of relaxin in the normal secretory endometrium. The difference may be due to absence of the relaxin-producing corpus luteum in cancer patients or to loss of relaxin synthesis in the malignant endometrium. The results of this study suggest that relaxin may be synthesized by the normal syncytiotrophoblast and trophoblastic tumors, although differential absorption of relaxin produced in another site cannot be excluded.

Luteinizing hormone-releasing factor increases release of human chorionic gonadotrophin in isolated cell columns of normal and malignant trophoblasts.

The effect of synthetic luteinizing hormone-releasing factor (LRF) on release of human chorionic gonadotrophin (hCG) was studied by isolated cell columns of normal syncytiotrophoblasts and choriocarcinoma (BeWo) cells. After LRF stimulation the release of hCG by the normal trophoblasts increased up to 4-fold and release by the malignant trophoblasts increased up to 6-fold, indicating a specific effect of LRF on normal and malignant trophoblast cells.

Electron microscopy of human choriocarcinoma transplanted into hamster liver

Human choriocarcinoma was transplanted into the liver of 26 hamsters in order to study the ultrastructure of tumor and junction zone. Two types of tumor cells were observed. The first type resembled the cytotrophoblast of the normal placenta, but the cells were larger and contained large irregular mitochondria with few cristae. The second type resembled the normal syncytiotrophoblast, and some exhibited phagocytotic activity. Liver nuclei and cytoplasmic components of liver cells were observed in some of the trophoblastic cells. Liver cells adjacent to tumor showed proliferation of the agranular reticulum and the presence of polyribosomes resembling those of the tumor cells. Desmosomes (submicroscopic bindings) were observed connecting tumor cells to liver cells. On the basis of present and past observations, a comparison is made between invasion by choriocarcinoma and implantation by the normal fertilized egg.