Preclinical validation of the new vitrification device possessing a feature of absorbing excess vitrification solution for the cryopreservation of human embryos

AIM: The cryopreservation of embryos is essential for assisted reproductive technology field. The aim of the present study is to examine the efficacy and ease of use of a new vitrification device, Kitasato Vitrification System (KVS), in cryopreservation of human embryos. METHODS: Human embryos at the cleavage or blastocyst stage were vitrified and warmed by KVS or Cryotop (control device). The survival of cleavage- and blastocyst-stage embryos and the developmental competence of cleavage-stage embryos were evaluated. Four individuals inexperienced in vitrification and warming embryos tested both KVS and Cryotop. The vitrification time and the detachment time of the embryos were evaluated. RESULTS: At the cleavage stage, there were no significant differences in the survival rate and the development rate to the blastocyst stage between KVS and Cryotop (100 vs 96.8% and 63.3 vs 61.3%, respectively). At the blastocyst stage, there was no significant difference in the re-expansion rate between KVS and Cryotop (100 vs 88.9%). The vitrification time was shorter for KVS than Cryotop. There was no significant difference in the detachment time between KVS and Cryotop. CONCLUSION: Kitasato Vitrification System is easy to operate, even for inexperienced users, and the viability of human embryos vitrified by KVS is comparable to that of Cryotop, a widely used vitrification device.