Rajashekhar G
Email Address
obggrs@nus.edu.sg
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Publication Over-expression and secretion of angiogenin in intrauterine growth retardation placenta(2003-04-01) Rajashekhar, G.; Loganath, A.; Roy, A.C.; Wong, Y.C.; OBSTETRICS & GYNAECOLOGYHuman angiogenin is a potent inducer of neovascularization. There is a strong evidence to suggest that it might be involved in morphological and angiogenic changes in the placenta, that are necessary for a successful fetal outcome during pregnancy. However, its precise role in the pathogenesis of abnormal pregnancies is yet unknown. Intrauterine growth retardation (IUGR), an abnormal pregnancy is not a specific disease entity per se, but rather a manifestation of many possible fetal and maternal disorders. In this study, we demonstrated, for the first time, that placental explants in vitro secrete significantly elevated levels of angiogenin in placental tissues from patients with IUGR. We also observed enhanced mRNA expression in placenta from these patients. In addition, using the immunohistochemical methods, we observed identical staining of angiogenin to villous syncytiotrophobalst and fetal endothelial cells in both IUGR and normal placenta. Functionally active placental explants were used to detect immunoreactive angiogenin in conditioned media of all the samples from IUGR placenta and normal term group. The mean levels of angiogenin secreted by IUGR placenta were 1.4-, 1.6-, and 1.3-fold higher (P < 0.01) than normal term samples at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and IUGR cases are in agreement with its mRNA levels and immunoblot analysis. In conclusion, the significant elevated levels of angiogenin in IUGR placenta may provide a molecular mechanism for the abnormal placental development. © 2003 Wiley-Liss, Inc.Publication Estrogen receptor alpha gene PvuII polymorphism and polycystic ovary syndrome.(2004) Aradhana, R.; Rajashekhar, G.; Roy, A.C.; Annapoorna, V.; Dramusic, V.; Choolani, M.; Wong, P.C.; OBSTETRICS & GYNAECOLOGYPublication Expression and secretion of the vascular cell adhesion molecule-1 in human placenta and its decrease in fetal growth restriction(2003) Rajashekhar, G.; Loganath, A.; Roy, A.C.; Wong, Y.C.; OBSTETRICS & GYNAECOLOGYObjective: The vascular cell adhesion molecule-1 (VCAM-1) is a member of the immunoglobulin gene superfamily and is expressed principally on endothelial cells. The present study was undertaken to compare the expression and secretion of VCAM-1 from normal pregnancies and those complicated by fetal growth restriction (FGR). Methods: Placentas from first-trimester (FT) (n = 17), normal term (n = 19), and FGR (n = 16) patients were collected immediately after elective cesarean delivery. VCAM-1 mRNA expression profiles by reverse transcriptase polymerase chain reaction, protein levels by enzyme-linked immunosorbent assay using explant culture in vitro, and its cellular localization by confocal microscopy were compared between FGR and normal placentas. Results: Functionally active placental explants were used to detect immunoreactive VCAM-1 in conditioned media of all the samples from the three groups. The mean levels of VCAM-1 produced by FT villi were found to be 1.9-, 1.7-, and 1.5-fold higher (P < .02) than term villi at 24, 48, and 72 hours of culture, respectively. Conversely, the respective mean levels of VCAM-1 produced by FGR placental villi were 2.3-, 2.5-, and 2.0-fold lower than levels of the normal term placental villi (P < .05). The secretion profiles of VCAM-1 from FT, term, and FGR villi correlated well with the mRNA levels; the amount secreted in FT villi was twice that of term villi. Moreover, mRNA transcripts from FGR pregnancies showed significantly decreased expression, in conformity with explant results. Conclusions: The presence of VCAM-1 in placental villi and down-regulation of its production at term indicate that VCAM-1 production is specific to developmental stage. The decreased VCAM-1 expression in FGR pregnancy could be attributed to the uteroplacental deficiency that is characteristic of this condition. Copyright © 2003 by the Society for Gynecologic Investigation.Publication Resistance to Fas-mediated cell death in BeWo and NJG choriocarcinoma cell lines: Implications in immune privilege(2003) Rajashekhar, G.; Loganath, A.; Roy, A.C.; Mongelli, J.M.; OBSTETRICS & GYNAECOLOGYObjective. An immune privileged site occurs when the allogenic tissue grafts have the propensity for prolonged survival in the host tissue. In this context, the survival and proliferation of malignant trophoblasts in the gravid uterus are currently unclear. In a previous study, we documented that Fas and FasL are coexpressed in choriocarcinoma [Gynecol. Oncol. (2003)]. This study was conducted to examine the role of the Fas/FasL pathway in immune privilege of BeWo and NJG choriocarcinoma cells in culture. Methods. The ability of anti-Fas mAb (CH-11) to sensitize choriocarcinoma cell lines to Fas-mediated cytotoxicity was assessed by MTT assays. Coculture experiments with Fas-sensitive Jurkat cells were used to demonstrate functional FasL from choriocarcinoma. RT-PCR was used to assess the expression of cFLIP. Results. The mean cell viability of BeWo and NJG cells declined to about 58 and 63% compared to controls after 72 h of culture in the presence of anti-Fas mAb (CH-11) while the Fas-sensitive Jurkat cells showed viability of only 10%. This resistance to Fas-mediated apoptosis in choriocarcinoma cells is reversed in the presence of cycloheximide (0.5 μg/ml) which further decreased the viability to 36 and 32%, respectively, at a dose of 300 ng/ml (P < 0.05). The observed resistance to Fas-mediated apoptosis therefore could be attributed to the short-lived endogenous inhibitor, cFLIP as demonstrated by the RT-PCR technique. In coculture experiments, FasL from choriocarcinoma cells induced apoptosis in the Fas-sensitive Jurkat cells, thereby indicating the capacity to evade immune attack. Conclusion. Decreased sensitivity to Fas-mediated apoptosis and counterattacking the lymphocytes may impart immune privilege in these malignant trophoblasts for prolonged survival in the host. © 2003 Elsevier Inc. All rights reserved.Publication Co-expression of Fas (APO-1, CD95)/Fas ligand by BeWo and NJG choriocarcinoma cell lines(2003) Rajashekhar, G.; Loganath, A.; Roy, A.C.; Mongelli, J.M.; OBSTETRICS & GYNAECOLOGYObjective. Fas (CD95) is a transmembrane protein of the tumor necrosis factor receptor superfamily that induces apoptosis in susceptible cells on crosslinking by its ligand (FasL). The Fas loss of function and concurrent expression of its ligand (FasL) have been associated with malignant phenotype. In this study, we sought to investigate the hitherto undescribed expression of Fas and FasL on the immortalized human choriocarcinoma cell lines BeWo and NJG. Methods. Receptor and ligand expression was demonstrated using specific antibodies and multiple techniques including immunocytochemistry, confocal immunofluorescence microscopy, flow cytometry, immunoblots, and reverse transcription polymerase chain reaction (RT-PCR). Results. Data from this study indicate that human choriocarcinoma cell subtypes co-express both Fas and FasL. A specific cytoplasmic and membranous pattern of immunoreactivity was noted that was further confirmed at mRNA transcripts by RT-PCR. In addition, we provide evidence using flow cytometry that the Fas receptors are downregulated. The mean fluorescence intensities for NJG and BeWo were 1.47 ± 0.5 and 1.59 ± 0.4, while that for Fas-positive Jurkat cells was 25.6 ± 3.1. Conclusions. To our knowledge, this is the first report on the identification and constitutive co-expression of Fas and FasL in BeWo and NJG choriocarcinoma cells. Choriocarcinoma cells evade immune attack by downregulating the Fas receptor and by killing lymphocytes through expression of FasL. Taken together, our investigations suggest that the Fas/FasL system may represent a mechanism by which malignant trophoblasts become resistant to apoptosis, escape immune surveillance, and metastasize. © 2003 Elsevier Inc. All rights reserved.Publication Hypoxia up-regulated angiogenin and down-regulated vascular cell adhesion molecule-1 expression and secretion in human placental trophoblasts(2005-07) Rajashekhar, G.; Loganath, A.; Roy, A.C.; Chong, S.S.; Wong, Y.C.; PAEDIATRICS; OBSTETRICS & GYNAECOLOGYOBJECTIVE: Many processes that are involved in cellular invasion, including blastocyst implantation, placental development, and rapidly growing tumors, occur in reduced oxygen environments. It has been surmised that oxygen tension could regulate the cytotrophoblast ability to differentiate and, as a consequence, to express proteins that are critical for placentation. The objective of the current investigation was therefore to test the hypothesis that placental tissues and trophoblast cells in culture, under low oxygen tension, release angiogenic factors that could affect vascular behavior and invasive potential, thus providing a link between abnormal placentation and maternal vascular abnormality. METHODS: Functionally active term placental explant culture and trophoblast cultures were used to demonstrate the secretion profiles of angiogenin and vascular cell adhesion molecule-1 (VCAM-1), and the real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique was employed to demonstrate the mRNA expression under both normoxic and hypoxic conditions. RESULTS: A significant increase in the secretion (P <.01) and mRNA expression (P <.01) of angiogenin and a significant decrease in the secretion (P <.04) and mRNA expression (P <.03) of VCAM-1 from both term placental explants and trophoblast cultures subjected to hypoxia in vitro were observed. CONCLUSION: Because the primary defect in uteroplacental insufficiency is placental maldevelopment probably associated with hypoxia in situ, this study provides molecular evidence to indicate that the differential expression and secretion of angiogenic factors may play an important role in these pathologic conditions. Copyright © 2005 by the Society for Gynecologic Investigation.