Effects of blastocyst artificial collapse prior to vitrification on hatching and survival rates and the expression of klf4 gene in mouse embryos.

Although the rate of blastocysts implantation of embryos is higher than previous stages but their survival rate is lower than them, which could be attributed to the completely filled blastocoel cavity with liquid and increased possibility of the formation of ice crystals. This liquid could prevent the penetration of cryoprotecting materials into the embryos. In this study, we reduced the volume of blastocoel before vitrification and compared survival rate and quality of in vitro embryos through klf4 gene expression with control group. In vitro mouse blastocysts were divided into three groups. In group 1, the blastocoel volume of blastocysts were reduced before vitrification and warming. In group 2, blastocysts were just vitrified and warmed and the blastocysts of group 3 (control group) were not undergone any specific treatment and were not vitrified. The expression of klf4 gene was assessed using real-time PCR technique. Data were statistically analyzed using one-way ANOVA and Duncan's post hoc tests. Our results showed that blastocoel volume reduction before vitrification significantly increased the hatching rate of the blastocysts from the zona pellucida and klf4 gene expression compared to vitrified group. Blastocoel volume reduction before vitrification could be used as an efficient method for improving the rate of in vitro fertilization.