Effect of Prefertilization Gravity Load to Mouse Secondary Oocytes on In Vitro Fertilization

抄録

In our previous study, we observed decreases in the rate of fertilization and increases in the rate of polyspermy when mouse ova were exposed to hypergravity during in vitro fertilization. Moreover, the structures in mouse ova were changed by hypergravity. However, it was not determined whether the change in the rate of fertilization was caused by gravitational force acting directly on a process during fertilization or by structural changes in the ovum caused by hypergravity. We investigated the effect of prefertilization hypergravity, which excluded the direct acts on a process during fertilization, on in vitro fertilization. The rates of monospermy, polyspermy, and non-fertilization were investigated under various gravity loading conditions: Pre-G group, 3G-load (centrifugal force) for 2 h before insemination; During-G group, 3G-load for 6 h during fertilization; Pre&During-G group, 3G-load for 2 h before insemination and 6 h during fertilization; Non-G group, 3G-load was not performed. The rates of polyspermy in all G-load groups were significantly higher than in the Non-G group. Furthermore, the rate of polyspermy in the Pre-G group was the highest. Two-hour exposure to hypergravity before insemination increased the rate of polyspermy, and this may be due to structural changes in the cytoskeleton of the secondary oocyte.