Abstract:
BACKGROUND: The outcome of a successful pregnancy depends on the initial attachment of the blastocyst to the endometrial epithelium, invasion of the epithelium into the decidua and subsequent placentation to establish a nutrient supply. The attachment of the trophoblast cells to the endometrium requires the formation of intimate contacts between the foreign fetal tissue and the maternal epithelium, the molecular basis of which is not well understood. Significant changes to the immune system at the cellular and molecular level are required at the onset of pregnancy to facilitate blastocyst attachment. Little is known about these molecular changes which occur in the endometrial epithelium at the time of implantation. The aim of this project was to develop an in vitro model of blastocyst implantation to test the hypothesises that Embryo attachment is regulated by steroid hormones and would lead to altered cytokine production by the epithelium. The endometrial epithelium acts in an immunomodulatory manner at the time of blastocyst attachment to initiate immune tolerance signals in the decidua. METHODS: In vitroblastocyst attachment models were established using human endometrial epithelial (RL95-2, HES, Ishikawa and AN3-CA) and trophoblast(JAR, JEG-3, HTR-8/SVneo and ED27)cell lines.The model has been used to look at spheroid attachment on different endometrial epithelial cell lines and their response to steroid hormones estrogen and progesterone. Expressions of immune modulatory factors in the system were assessed using RealtimePCR. RESULTS:The data imply that spheroid attachment is significantly increased in endometrial epithelial cell lines Ishikawa, HES and AN3-CA and significantly decreased in RL95 cells in response to steroid hormones. Expression of trophoblast factors by JEG-3 cells implies that it is the most appropriate cell line to represent blastocyst among the cell lines used. Co-culture of JEG-3 spheroids with epithelial cells resulted in significant changes in trophoblastassociated molecules B7-H1, HCG and HLA-G. Results regarding the immunoresponsiveness of endometrial epithelial cell lines HES and Ishikawa are inconclusive. CONCLUSION:Data from this study imply that JEG-3 spheroids could be used as model blastocyst in an in-vitro setting. Despite being popular, RL95-2 cells are not an appropriate model of the endometrial epithelium and further experimentation is required to evaluate theappropriateness of other endometrial epithelial cell lines.