RESUMO
Cryopreservation of embryos is a crucial component of current assisted reproductive technologies (ART). While the ART outcomes for many species have been greatly improved by the introduction of minimum volume vitrification devices, these devices can be difficult to handle and load. To reduce this problem, we recently developed a vitrification carrier which has a highly absorbent surface so that it simply and rapidly removes excess free vitrification solution from the specimen before the cooling step. This Kitasato Vitrification System (KVS) gives excellent results for human and mouse embryo vitrification. This study aimed to determine whether the KVS would also be effective for bovine blastocyst vitrification by comparing outcomes for the control device that was the KVS without excess vitrification solution absorber. The effect of varying the length of time spent in the first equilibration solution (0-10 min) was also evaluated. Vitrification with the KVS resulted in significantly higher survival and hatching rates than with the control device loaded with the same volume of vitrification solution (survival: 98.6% vs 87.6%, hatching at 72 h post warming: 87.3% vs 66.7%, respectively). The best outcomes were obtained with a 10 min equilibration step prior to exposure to the vitrification solution for 30 s. We also evaluated the effect of embryo quality on blastocyst viability when using the KVS. Survival rates of high- and low-quality embryos were comparable but low quality embryos had significantly lower hatching rates. Overall, the results indicate that the KVS vitrification device is effective for bovine blastocyst vitrification.
