Effects of Re-Vitrification of Mouse Morula and Early Blastocyst Stages on Apoptotic Gene Expression and Developmental Potential

Objectives: Re-vitrification of embryos immediately after thawing or after a culture period could be used to preserve the extra embryos after embryo transfer. This study aims to clarify the effect of re-vitrification on Bax and Bcl-2 gene expressions of compact and early blastocyst stage embryos.

Materials and methods: This experimental study was performed on mouse embryos. We collected 8-cell stage embryos (n=400) from female mature mice, 60-62 hoursafter injection of human chorionic gonadotropin (hCG). The embryos were divided into 5 groups: fresh (n=80), vitrified at the 8-cell stage (n=80), vitrified at the blastocyst stage (n=80), vitrified at the 8-cell stage, and re-vitrified at the compact (n=80) and early blastocyst stages (n=80). Embryos were vitrified by cryolock. We analyzed the developmental rates of the vitrified-warmed embryos with the chi-square test. Quantitative polymerase chain reaction (qPCR) data were analyzed with SPSS version 16 using one-way analysis of variance (ANOVA) followed by Tukey's post hoc test. P<0.05 were considered statistically significant.

Results: The expanded blastocyst formation rate showed a significant difference in re-vitrified embryos compared with fresh embryos (P<0.05). However, this result was similar between the two re-vitrified groups. Our data showed a significant difference in expression of the Bax and Bcl-2 genes between re-vitrified and fresh embryos (P<0.05). Expressions of the Bax and Bcl-2 genes showed no significant difference between the two re-vitrified groups.

Conclusions: Based on our study, re-vitrification could affect developmental rate and expressions of the Bax and Bcl2 genes.