Artificial stimulation of mouse oocyte, in the absence of sperm contribution, can induce its parthenogenic activation of oocyte. Ultrasound is one of the newest methods for artificial activation of mammal oocytes, and its successful utilization in pig oocyte activation has been recently reported. Our objective was to assess the effect of ultrasound on mouse oocyte activation.
Our groups included1 control group, 3 experimental groups consisting of 1, 2 and 3 repetitions of ultrasound exposure, and 3 sham groups handled similar to experimental groups but ultrasound system was off during treatments. In experimental groups, adult female NMRI mice at the interval between pregnant mare serum gonadotropin (PMSG) and human corionic gonadotropin (hCG) injections, were exposed to continuous ultrasound with 3.28 MHz frequency and peak intensity (Ipk) = 355 mW/cm2. Sixteen hours after injection of hCG, the mice were euthanized and their oocytes were collected; thereafter, parthenogenic oocytes were counted.
Data analysis using the ANOVA test shows a significant increase in the number of parthenogenic oocytes in mice with 3 overall exposures to ovarian ultrasound (p<0.05). A significant decrease in the number of metaphase II (MII) oocytes numbers was also seen in mice treated with ultrasound (p<0.05).
Ultrasound is thought to induce pores generation in oocyte membranes and provides an easier inward transport of Ca++ into oocytes. This phenomenon can induce meiosis resumption in immature oocytes. With increased exposure repetitions from 1 to 3 times and greater Ca++ arrival, oocytes can be parthenogenetically activated.