Forced collapse of the blastocoel enhances survival of cryotop vitrified bovine hatching/hatched blastocysts derived from in vitro fertilization and somatic cell nuclear transfer

Freezing of bovine blastocysts has been widely used to improve the feasibility of cattle production by the embryo transfer technique. However, the low survival of vitrified-warmed embryos and their further development are crucial problems. Particularly, the production of offspring in vitrified-warmed bovine hatching/hatched blastocysts derived from in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT) is very low. Thus, we examined the effects of forced blastocoel collapse (FBC) before vitrification of bovine IVF- and SCNT-derived hatching/hatched embryos on the survival rate and apoptosis index after warming. Under optimal conditions, the overall survival rates in vitrified-warmed bovine IVF- and SCNT-derived hatching/hatched blastocysts were higher in FBC groups than in non-FBC groups (p < 0.05). The total cell numbers of vitrified-warmed hatching/hatched blastocysts were higher in FBC groups than in non-FBC groups (p < 0.05). Otherwise, the number of apoptotic positive cells of vitrified-warmed hatching/hatched blastocysts was lower in FBC groups than in non-FBC groups (p < 0.05). Taken together, these findings suggest that forced collapse of the blastocoel using a pulled Pasteur pipette is an effective pretreatment technique for vitrification of bovine IVF- and SCNT-derived hatching/hatched blastocysts.