Effect of Equilibration Time in Vitrification Solution on Post-Thawed Survival Rate and Development of Mouse Two Cell Embryos

Background and purpose: To assess the effect of equilibration time on the vitrified-warmed two cell mouse embryos. Material and Methods: Two cell embryos were obtained from oviducts of super ovulated female NMRI mice. The embryos were randomly allocated in four groups and vitrified using cryotop and two-step mediaprotocol. The experimental groups were: 1) embryos were equilibrated in vitrification solution (v1) (7.5% EG, 7.5% DMSO, 20% BSA, Ham's F10) for 5 min (n=122), 2) 10 min (n=102), 3), 15 min (n=105), 4), 20 min (n=140). After two weeks, the vitrified embryos were thawed. The survived embryos were cultured in Ham, s F10 medium for 72 hours and the cleavage, blastocyst formation and hatching rates were assessed. Results: The results demonstrated that survival, cleavage, blastocyst formation and hatching rates did not show any significant differences among the embryos in different groups which exposed in first vitrification solution for periods of 5 to 20 minutes. Conclusion: The range of 5 to 20 minutes for equilibration of mouse embryos in the first vitrification solution can be used in the two-step media plus cryotop method for embryo vitrification.