Vitrification of Mouse Blastocysts by Open or Closed System and Warming in Sucrose-containing or Sucrosefree Diluent

BACKGROUND: Cryopreservation of embryos is of considerable relevance for the implementation of embryo transfer programs and the establishment of embryo banks in several mammalian species. OBJECTIVE: The present investigation compares two different vitrification systems and two different warming solutions. MATERIALS AND METHODS: Vitrification was performed using "Open Pulled St raw (OPS) or CVM RingFibre plug™ (CVM) devices. Warming was carried out either in a warming solution containing 0.33 M sucrose or in a solution devoid of sucrose. RESULTS: Differences between vitrification systems were not significant. Warming in sucrose-containing diluent resulted in an expansion rate of 64%, as compared to 86% in a solution devoid of sucrose; reported hatching rates were 45% vs. 9%, respectively (p<0.05). Upon transfer, implantation rates for OPS- and CVM were 50% and 27%, respectively, compared with 55% for freshly collected embryos. The implantation rate after warming was 43% for sucrose-containing and 33% for sucrose-free medium. CONCLUSION: a) both vitrification systems are suitable for vitrifying mouse blastocysts; b) warming in sucrose-free diluent yields better embryo survival rates than in diluent containing 0.33 M sucrose.