Alternation of apoptotic and implanting genes expression of mouse embryos after re-vitrification

Background: Nowadays, oocytes and embryos vitrification has become a routine technique. Based on clinical judgment, re-vitrification maybe required. But little is known about re-vitrification impact on genes expression.
Objective: The impact of re-vitrification on apoptotic and implanting genes, Bax, Bcl-2 and ErbB4, at compaction stage embryos were evaluated in this study.
Materials and Methods: In this experimental study, 8 cell embryos (n=240) were collected from female mature mice, 60-62 hr post HCG injection. The embryos were divided randomly to 3 groups included: fresh (n=80), vitrified at 8 cell stage (n=80), vitrified at 8 cell stage thawed and re-vitrified at compaction stage (n=80). Embryos were vitrified by using cryolock, (open system) described by Kuwayama. Q-PCR was used to examine the expression of Bax, Bcl2 ErbB4 genes in derived blastocysts.
Results: Our result showed that expanded blastocyst rate was similar between vitrified and re-vitrified groups, while re-vitrified embryos showed significant decrease in expanded blastocyst rate comparing with fresh embryos (p=0.03). In addition, significant difference was observed on apoptotic gene expression when comparing re-vitrified and fresh embryos (p=0.004), however expression of Bax and Bcl-2 (apoptotic) genes didn't demonstrate a significant difference between re-vitrified and vitrified groups. The expression rate of ErbB4, an implantation gene was decreased in re-vitrified embryos comparing with fresh embryos (p=0.003), but it was similar between re-vitrified and vitrified embryos.
Conclusion: Re-vitrification can alter the expression of Bax, Bcl-2 and ErbB4 genes and developmental rate of mouse embryos in compaction stage.