Endometrial beta3 Integrin profile reflects endometrial receptivity defects in women with unexplained recurrent pregnancy loss

BACKGROUND The pathophysiology of recurrent pregnancy loss (RPL) is still unknown in 50% of the cases. Herein we measure the expression of beta3 integrin subunit, a well-known implantation marker, in women with or without RPL and correlate it with the histological dating of the endometrial tissue. METHODS LH-timed endometrial biopsies were obtained from cases (RPL; n = 21, age 33.9+/-4.7) and healthy controls (n = 29; age 29.8+/-4.1) during the mid-secretory phase (post ovulatory day: 8 to 10). Endometrial samples were timed histologically according to Noyes' criteria and underwent immunohistochemical staining for beta3 integrin expression. For statistical analysis the semi-quantitative HSCORE was assessed. Type I (beta3 negative in an out-of-phase endometrium) and Type II defect (beta3 negative in an in-phase endometrium) were also analysed. Statistical analysis was done with Student t-test, Mann Whitney U test, ANCOVA and chi square for trend. Significance was set as P < 0.05. RESULTS The mean (SD) age in controls was lower compared to cases [(29.8 (4.1) vs. 33.9 (4.7) - P = 0.001; Student t-test)]. The median (range) expression of beta3 integrin in controls and cases was 1.94 (0 to 3.5) vs. 0.82 (0 to 3.6), respectively (P = 0.001; Mann Whitney U test). Significance was still significant after adjusting for age (P = 0.03;ANCOVA). The normal positive staining > =0.7 of beta3 integrin subunit and in-phase endometrium was seen in 24 out of 29 (82.8%) controls, but in only 6 out of 21 (28.6%) of cases with RPL; Type I and II defects were seen in 10.3 and 6.9% of controls, while present in 52.4 and 19.1% of cases, respectively (P = 0.0005; chi-square). CONCLUSIONS Women with unexplained RPL had significantly reduced integrin expression compared to controls. Our findings underline the need for further molecular analysis of endometrial tissue in affected women.