Effect of Hydrostatic Pressure on In Vitro Maturation of Mouse Oocytes

Examining of the effect of hydrostatic pressure on in vitro maturation of mouse oocytes. Female NMRI mice 6-8-week-old was selected. Antral follicles with diameter of 500μm were isolated from ovaries. Then follicles were divided into control and experiment groups. In experiment group, follicles were transferred to pressure chamber and subjected to 20 mm pressure for 30 min. Follicles without pressure exposure used ascontrol. Each follicle cultured individually in 100 μl α-MEM supplemented with 5% FBS, 100 mIU/ml rFSH, 10 ng/ml rEGF and 7.5 IU/ml HCG for in vitro maturation, under mineral oil. Follicles from two groups were cultured for 48 h and evaluated in vitro maturation of oocyteby the percentage of oocytes in GV, GVBD and MII. Viability of oocytes and cumulus cells was assessed with nuclear vital staining (propidium iodide and bisbensamide). The results showed that, exposure to hydrostatic pressure improved the oocyte in vitro maturation. After 24 h the percentage of GVBD and metaphase (MII) oocytes increased in hydrostatic pressure treated follicles compared to control (P<0.05). After 48 h, the percentage of metaphase (MII) oocytes increased in hydrostatic pressure treated follicles compared to control (P<0.05). Furthermore, a significant increase in the cumulus cells was observed (P<0.05). Hydrostatic pressure had no effect on oocyte viability. It seems that hydrostatic pressure can be a cell death inducer in cumulus cells. Hydrostatic pressure may play a role in oocyte maturation and fertilization by improving in releasing and mediating signals to oocyte by increasing cell death in cumulus cells.