초자화동결법을 이용한 생쥐배아 발달단계별 동결성적의 비교
초자화동결법 발달단계별 동결성적;
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Objectives : We tried to find out the optimal freezing time in terms of developmental stage of mouse embryo and the effectiveness of vitrification method for freezing them. Methods : Superovulation induction was performed with the ICR female mice (5-6 weeks old) using PMSG and hCG, and they were mated with male mice aged 12 weeks or more. Total 1,437 mouse embryos (vitrification group: 743, slow-freezing group: 694) were obtained and cultured with the T6 containing 0.4% BSA medium. Each developmental stage of embryos (1-, 2-, 4-, 8-cell, morula & blastocyst) were cryopreserved by vitrification and also by slow freezing method for comparison of the results. After thawing, the recovery rate, the survival rate and the blastocyst developmental rate (rate of development to blastocyst) were analysed. We compared the stages in two different settings. Results : The survival and developmental rates at all subgroups of vitrification method were significantly higher than those of slow-freezing groups, but the recovery rates did not show significant differences. In vitrification group, the survival rate and the blastocyst developmental rate were highest when frozen at morula stage, 98.4% and 86.4%, respectively. In slow-freezing group, the survival rate was highest when frozen at morula stage, 87.2% and the blastocyst developmental rate was highest when frozen at 8-cell stage, 78.1%. Conclusions : The vitrification method is more efficient for mouse embryo freezing compared with slow freezing one. Among various developmental stages of mouse embryos, morula stage seems to be the most optimal stage for cryopreservation, whatever the freezing method applied. Therefore, we recommend embryo freezing at morula stage by vitrification method.