P-70: The Effect of Hydrostatic Pressure on Parthenogenetic Activation of Mouse Oocytes Derived from In vitro Grown Ovarian Follicles

Background: Parthenogenesis is the production of an embryo from a female gamete in the absence of any contribution from a male gamete, with or without the eventual development into an adult. In vivo, mammalian parthenogenesis is a rare event. Parthenogenesis can be efficiently induced in vitro with a variety of mechanical, chemical, and electrical stimuli in several species. Hydrostatic pressure as a physico-mechanical force is effective in reproduction system. It can act as a mechanical stimulator that rearranges egg contents, leading to new structural or molecular combinations. Alternatively, mechanical stimulation could stimulate a mechanically-gated process, such as the opening or closing of ion channels. Such alterations to ion channels can lead to ionic changes. This study investigated the effect of hydrostatic pressure on parthenogenetic activation of mouse oocytes derived from in vitro grown ovarian follicles. Materials and Methods: Preantral follicles were isolated from 12-day-old female NMRI mice. Each follicle cultured individually in α-MEM culture medium supplemented with 5% FBS, 100 mIU/ml rFSH and 10 ng/ml rEGF, under mineral oil for 12 days. On day 12, follicles with diameter ≥ 500 µm and good quality have been induced using 5 IU/ml HCG for in vitro maturation. Then follicles divided to control and experiment groups. In experiment group, follicles were transferred to pressure chamber and subjected to 20 mmHg pressure for 30 min. Follicles without exposure to pressure were considered as control. Follicles from two groups were cultured for 24-48 hours. The in vitro maturation of oocytes and embryo development were assessed. Results: The results showed that, exposure of follicles to pressure affected the oocyte maturation and the percentage of metaphase oocytes (MII) and 2-cell embryos increased in hydrostatic pressure treated follicles compared to control (p<0.05). After 24 hours, the percentage of MII oocytes and 2-cell embryos in experiment group (11.8% and 8.2%; respectively) were increased compared to control group (4.9% and 2.5%; respectively), (p<0.05). After 48h, the percentage of 2-cell embryos in experiment group (27%) was increased compared to control group (11.1%) (p< 0.05). Conclusion: It is concluded that partenogenetic activation can be induced by hydrostatic pressure in mouse.