Expression of αVβ3 integrin in rat endometrial epithelial cells and its functional role during implantation

The alpha(v)beta(3) integrin as a marker of endometrial receptivity has been well established in human and other mammalian species; however, its expression is still not known in rats. Our objective was to establish the expression Of alpha(v)beta(3) integrin as a marker of endometrial receptivity in rat and to further prove its role in implantation by function-blocking studies in this species. Immunocytochemical mica immunohistochemical and flow-cytometric studies were performed in rat endometrial epithelial cells (EEC) to demonstrate the expression Of alpha(v)beta(3) integrin during non-receptive, pre-receptive and receptive phases of the uterus. Results revealed positive immunocytochemical staining for alpha(v) and beta(3) subunits on the surface of EEC of days 4 and 5 p.c. (post-coitum), but the intensity was higher in cells of day 5 p.c. Flow-cytometric study revealed higher level of alpha(v)beta(3) on day 5 p.c. as compared to day 4 p.c. and non-pregnant animals. Immunohistochemical analysis of uterine tissue also revealed that the alpha beta(3) expression in LE was higher on day 5 p.c. morning as compared to that observed on day 4 p.c. In addition, the expression of beta(3) subunit was not evident in rats receiving ormeloxifene, an agent known to inhibit the uterine receptivity. Immunoblotting experiments also revealed higher expression of uterine beta(3) on day 5 p.c. On day 6, expression of beta(3) was high in implantation sites than on inter-implantation sites. In immature ovariectomized rats, alpha(v)beta(3) was up-regulated by progesterone and by a combination of estrogen and progesterone. The expression of alpha(v)beta(3) was also up-regulated in EEC co-cultured with blastocysts. All the agents used for function-blocking studies showed significant reduction in the number of implantation sites in treated horn as compared to sham control horn. The present study has successfully demonstrated the expression of alpha(v)beta(3) in rat EEC as a marker of endometrial receptivity and showed that this molecule is indispensable for the process of implantation in this species. (C) 2008 Elsevier Inc. All rights reserved.