Effect of Ovarian Stimulation on the Endometrial Apoptosis at Implantation Period

Background: Apoptosis is a process that plays an important role during early stage of implantation. The aim of this study was to investigate the incidence of apoptosis in mice endometrium after ovarian stimulation at implantation period. Methods: NMRI female mice were divided into two groups: 1) control group, which were rendered pseudopregnant by vaginal stimulation and 2) experimental group, which were stimulated using an intrapritoneal injection of 10 IU hMG followed by another injection of 10 IU hCG after 48 h. In the evening of the second injection, the mice were rendered pseudopregnant the same as control group. Samples were obtained from 1/3 middle part of uterine horns during implantation period. Apoptosis was assessed in two groups at implantation period using light and electron microscopic studies, TUNEL staining and semiquantitative RT-PCR. Results: Our morphological and ultrastructural results showed apoptosis in both groups, while TUNEL analysis showed that the percentage of TUNEL-positive cells was higher in stimulated group than in the control group (P≤0.05). The expression of P53, Fas and FasL mRNA was similar in two groups but Bax and Bcl2 were much higher in control group than in the stimulated group (P≤0.05). The ratio of Bax/Bcl2 expression was much higher in stimulated group than in the control group (P≤0.05). Conclusion: The ovarian stimulation could change the expression of some apoptosis-related genes and enhance the incidence of endometrial apoptosis at implantation period thus, it could affect on the implantation rate and endometrial receptivity.