ABSTRACT
OBJECTIVE: Vitrification requires a high concentration of cyroprotectant (CPA) and an elevated cooling speed to avoid ice crystal formation. We have evaluated the effect of different combinations of cooling rate and CPA on embryonic integrity (developmental competence) in order to increase the efficiency of vitrification without impairing embryo viability. We hypothesized that the combination of CPA or the increase of cooling rates can reduce the concentration of toxic CPA for vitrification. As consequently, we performed experiments to evaluate the effect of various composition of CPA or slush nitrogen (SN2) on the mouse embryonic development following vitrification using low CPA concentration. METHODS: Vitrification of mouse embryos was performed with EM grid using liquid nitrogen (LN2) or SN2 and different composition of CPAs, ethylene glycol (EG) and dimethylsulfoxide (DMSO). After vitrification-warming process, their survival and blastocyst formation rates were examined. For analyzing long-term effect, these blastocysts were transferred into the uterus of foster mothers. RESULTS: Survival and blastocyst formation rates of vitrified embryos were higher in EG+DMSO group than those in EG only. Furthermore, the group using SN2 with a lower CPA concentration showed a higher survival of embryos and developmental rates than group using LN2. CONCLUSION: The combination of EG and DMSO as CPAs may enhance the survival of mouse embryos and further embryonic development after vitrification. SN2 can generate high survival and developmental rate of vitrified/warmed mouse embryos when a lower concentration of CPA was applied. Therefore, these systems may contribute in the improvement of cryopreservation for fertility preservation.