Effect of double activation on the development of frozen-thawed oocytes after intracytoplasmic sperm injection

Abstract

To investigate the influence on developmental potential of frozen-thawed rabbit oocytes with double assisted activation followed by intracytoplasmic sperm injection (ICSI). A total of rabbit oocytes were collected and thawed after vitrification cryopreservation. Among all oocytes were cultured for 1 hour followed by ICSI. 156 Survived oocytes were divided into 5 groups randomly. I0634 single activation: 30 oocytes were added with calcium ionomycin (I0634) at 5 micromol/L for 5 minutes; SrCl(2) single activation: 26 oocytes were added with strontium chloride at 10 mmol/L for 10 minutes; I0634 double activation: 33 oocytes were activated by I0634 twice; SrCl(2) double activation: 28 oocytes were activated by strontium chloride twice. 39 oocytes were not added with any activators. The rate of fertilization, cleavage and blastocysts formation were observed and compared between various groups. The rates of fertilization, cleavage and blastocysts formation were in group of SrCl(2) single activation were higher than those of I0634 single activation group without statistical difference (54% vs.33%, 27% vs. 17%, 8% vs. 3%, P < 0.05). However, those above rates in double activation by I0634 were higher significantly than those of single I0634 activation (82% vs. 33%, 55% vs. 17%, 15% vs. 3%, P < 0.05). The rates of fertilization (61%) was higher and the rate of cleavage (21%) and blastocysts formation (7%) were lower in group of SrCl(2) double activation in comparison with group of SrCl(2) single activation without reaching statistical difference (P < 0.05). Notably, the rates of fertilization, cleavage and blastocysts formation in I0634 double activation group were higher than those in group of SrCl(2) double activation with statistical difference (82% vs. 61%, 55% vs. 21%, 15% vs. 7%, P < 0.05). It might enhance the potential of fertilization of oocytes and early embryo development treated by double activation following ICSI, however, those activated oocytes demonstrate rapid cleavage.