Ovarian stimulation makes a disruption of imprinting genes of mouse oocyte and placenta

Abstract

OBJECTIVE: To investigate the effect of ovarian stimulation (OS) on the expression of imprinting genes of oocytes and placenta. DESIGN: A randomized controlled study based on mouse model. MATERIALS AND METHODS: Eight-week-old C57 female mice were injected with pregnant mares' serum gonadotropin (PMSG) in different dose (0, 10, 20, 30 IU), and 10 IU human chorionic gonadotropin (HCG). Serum estradiol and FSH level were detected. MII oocytes were harvested at 14 hours post HCG injection. RNA extraction and RT-real time PCR were conducted in oocytes and ovarian tissues. C57 female mice were divided into OS group, which were injected with 10 IU PMSG and 10 IU HCG, and control group, whose estrous cycle were evaluated by vaginal smear, and was injected with 10 IU HCG at estrus day. The presence of a vaginal plug was designated at 0.5 day post coitum (dpc). Placentas and embryos were collected at 15dpc. Placentas were examined by gene microarrays, and RT-real time PCR was conducted to verify the expression of Kdm1b, Impact, Igf2, H19, Zac1, Grb10, Mest, and Snrpn. RESULTS: The serum estradiol and FSH level increased PMSG-dose-dependently. The expression of Zac1, H19 and Snrpn were increased, while Mest and Grb10 were decreased in 20 IU-PMSG-treated ovaries significantly. 10 IU PMSG treatment exhibited the best ovarian response (25 ± 2 oocytes/mouse), but 20 IUi PMSG dose resulted in decreased ovarian response (7 ± 1). Microarrays of placentas revealed up-regulation of more than 400 genes and down-regulation of approximately 200 genes in OS group than in control group. Following RT-real time PCR showed significantly increased expression of Igf2, H19, Zac1, and Grb10. The arrest of embryo development was increased, and the live birth rate was decreased significantlyin OS group than in control group. CONCLUSION: Ovarian stimulation makes a disruption of imprinting genes of mousue oocytes and placenta, and may adversely affect the developing potential of oocytes and embryos.