Higher endometrial receptivity caused by Letrozole in antagonist protocol-stimulated mouse uterus

Abstract

Background: The implantation rate of IVF remains low due to the adverse effect of ovarian stimulation on endometrial receptivity. Integrin β3, E-cadherin and Leukemia Inhibitory Factor (LIF) are the best markers known for endometrial receptivity evaluation. In this study, the effect of adding Letrozole to antagonist protocol based on the expression of integrin β3, E-cadherin and LIF level during implantation window was investigated. Letrozole is an inhibitor of aromatase that can prevent the supraphysiological estrogen level. The goal of the study was to prove that adding Letrozole to IVF antagonist protocol can increase the expression of Integrin β3, E-cadherin, and LIF concentration of mice uterine. Methods: This is an experimental study with a post-test only group design using Balb/c mice mimicked ovarian stimulated IVF. Antagonist protocol was applied to one group as ovarian stimulation, while the other group received the combination of Letrozole and antagonist protocol.  Uterus samples were collected 48 hours after ovarian stimulation. Integrin β3 and E-cadherin expression were detected by immunohistochemistry technique and LIF level assay by ELISA. Normality test was carried out using Shapiro-Wilk, and homogeneity test by Levene’s T. Comparison between integrin β3 and E-cadherin expression were tested by Mann-Whitney and Fisher's exact, while comparison of LIF was tested by Mann- Whitney, with p<0.05 considered as significant. Path analysis was done to measure each variable contribution.Results: The Letrozole + GnRH antagonist treated mice showed significantly higher integrin β3 (2.71 + 0.61 vs 1.04 + 0.08, p<0.05) and E-cadherin (3.73 + 0.28 vs 1.16 + 0.29, p<0.05) expression in endometrium. It also showed significantly higher level of uterine LIF (1.78 + 0.13 vs 1.66 + 0.17 ng/ml, p<0.05) during implantation window than GnRH antagonist treated mice alone. Expression of integrin β3 (c2= 22.91, p<0.05) and E-cadherin (c2=36.00, p<0.05) were significantly higher in Letrozole group compared to control.Conclusion: Letrozole caused higher expression of Integrin β3, e-cadherin, and, LIF concentration in Mice uterine stimulated by antagonist protocol. Letrozole had the highest contribution to the increase of E-cadherin.  Integrin β3 together with E-cadherin and Letrozole had 31.4% contribution to the increase of LIF.Â