P-121: Which Developmental Stage is Suitable for Re-vitrification? Compact Stage Re-vitrification or Early Blastocyst Stage Re-vitrification

Background: The aim of this study was evaluation of developmental rate and Bax, Bcl-2 and ErbB4 genes expression following re-vitrification in compact and early blastocysts stages. Materials and Methods: 5-8 cell embryos were collected from female mature mice, 60-62 hours post hCG injection. The embryos were divided to five groups including: fresh, vitrified at 5-8 cells, vitrified at blastocyst stage, vitrified 5-8 cells and re-vitrified at compact or early blastocyst stage. Embryos were vitrified by using cryolock, as described by Kuwayama et al. Development of embryos were recorder daily. Results were analyzed by using Chi square. QPCR has been used to examine the expression of Bax, Bcl2 ErbB4 genes in derived blastocysts. The data was analyzed with ANOVA. Results: Blastocyst formation rates showed no significant differences between vitrified and re-vitrified groups, although there was significant difference between re-vitrified and fresh embryos (p<0.05). Also it showed no significant differences between two re-vitrified groups. Our data showed that expression of Bax, Bcl- 2 and ErbB4 genes had a significant difference (p<0.05) between re-vitrified and fresh embryos. Although there was no significant difference between re-vitrified and vitrified embryos regarding genes expression. Expression of Bax, Bcl-2 and ErbB4 genes showed no significant difference between two re-vitrified groups. Conclusion: Based on our study, re-vitrified embryos in compact and blastocyst stage are nearly equal in developmental rate and expression of Bax, Bcl2 and ErbB4 genes, although this amount of genes expression is altered significantly compared with fresh embryos. Therefore, we can re-vitrify embryos in compact or blastocyst stage.