The involvement of osteopontin and β3 integrin in implantation and endometrial receptivity in an early mouse pregnancy model

ObjectiveTo explore the roles of osteopontin and β3 integrin in successful implantation.Study designIn this study, an early pregnant mouse model was established by peritoneal injection of pregnant mare serum gonadotropin and human chorionic gonadotropin (PMSG + hCG). The expression of osteopontin (OPN) and β3 integrin on the endometrium was measured by immunohistochemistry, RT-PCR, and western blot. The function of OPN and β3 integrin in implantation was investigated by intrauterine injection of OPN and β3 integrin antibody.ResultsWe found that PMSG + hCG injection significantly increased the number of blastocysts during implantation as well as the concentration of estradiol and progesterone in serum and endometrium tissues. OPN and β3 integrin were co-expressed in luminal epithelium and their levels dynamically changed from day 4 to day 8 of pregnancy with peak expression on day 5. The percentages of OPN and β3 integrin positive cells in the luminal epithelium were significantly higher in PMSG + hCG-stimulated mice on day 5 than in control mice. Functional blockade of OPN and β3 integrin significantly inhibited implantation.ConclusionsThis study suggests that co-expression of OPN and β3 integrin is a biological marker for good endometrial receptivity and that both proteins play a crucial role in blastocyst implantation.