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

Objective: To explore the roles of osteopontin and beta 3 integrin in successful implantation. Study design: In 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 beta 3 integrin on the endometrium was measured by immunohistochemistry, RT-PCR, and western blot. The function of OPN and beta 3 integrin in implantation was investigated by intrauterine injection of OPN and beta 3 integrin antibody. Results: We 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 beta 3 integrin were co-expressed in luminal epithelium and their levels dynamically changed from day 4 to days of pregnancy with peak expression on day 5. The percentages of OPN and beta 3 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 beta 3 integrin significantly inhibited implantation. Conclusions: This study suggests that co-expression of OPN and beta 3 integrin is a biological marker for good endometrial receptivity and that both proteins play a crucial role in blastocyst implantation. (C) 2013 Elsevier Ireland Ltd. All rights reserved.