Expression of vascular endothelial growth factor in rat uterus during peri-implantation

The first distinct mark of rodent implantation is the increased vascular pe rmeability and significant angiogenesis at the sites of blastocyst implanta tion, but its mechanism is not clearly defined. Vascular endothelial growth factor (VEGF) is the key mediator for angiogenesis during embryogenesis an d adult span and also serves as a vascular permeability factor. The aim of this study is to explore VEGF regulation mechanism and the possible role th at VEGF plays in implantation by studying the VEGF expression and angiogene sis in the rat uterus during estrous cycle, ovarioectomized and peri-implan tation stages using in situ message RNA hybridization and confocal laser sc anning techniques. The results indicated that VEGF was regulated by ovarian steroid hormones. VEGF expression before implantation was localized at lum inal epithelium, shifted to stroma as implantation initiated and extensivel y located at the decidualizing stroma region after implantation. Bandeiraea simplicifolia-1 (BS-1) agglutinin and antibody against von Willebrand fact or (vWF) were used to mark the endothelial cells and blood vessels. The res ults showed that the active angiogenesis occurred during the implantation p rocess and this effect was probably mediated by VEGF. The results suggest t hat under the regulation of ovarian steroid hormones, VEGF plays an essenti al role in angiogenesis and increasing vascular permeability in endometrium , which are necessary for successful implantation.