Successful cryopreservation of mouse and human blastocysts using vitrification solution without sucrose and Ficoll

Purpose of Investigation: This study investigated whether cryopreservation of mouse and human blastocysts using vitrification solutions formulated with or without sucrose and Ficoll affects survival rate and pregnancy outcome. Materials and Methods: Two-cell mouse embryos were retrieved from C57BL/CBA females aged 5 weeks and cultured to the blastocyst stage. Artificial shrinkage of blastocysts was performed by blastocoel fluid aspiration before vitrification and then exposed to and vitrified-warmed in one of four different vitrification solutions: 1) 25% glycerol, 25% ethylene glycol, 20% SSS and PBS without sucrose and Ficoll (G25E25), 2) G25E25 with 0.5 M sucrose (G25E25S0.5), 3) G25E25 with 10 mg/mL Ficoll (G25E25F10), and 4) G25E25 with 0.5 M sucrose and 10mg/mL Ficoll (G25E25S0.5F10). Second, in 435 infertile women undergoing in vitro fertilization and embryo transfer (IVF-ET), artificially shrunken blastocysts were vitrified-warmed either in G25E25 (n = 206) and G25E25S0.5F10 (n = 229). Results: In the mouse series, in vitro survival rates of post-warm blastocysts were 93, 91, 90, and 90% in G25E25, G25E25S0.5, G25E25F10, and G25E25S0.5F10, respectively. No significant differences among four groups were found. In the human series, in vitro survival rates and clinical pregnancy rate of blastocysts vitrified-warmed in G25E25 were 96 and 53.3%, respectively, which were similar to those in G25E25S0.5F10 (92 and 51.9%, respectively). Conclusions: Sucrose- and Ficoll-free vitrification solutions can be successfully cryopreserved mouse and human blastocysts without compromising survival rate and pregnancy outcome.