In vitro Development of Zona Pellucida-free Porcine Zygotes Cultured Individually after Vitrification.

BACKGROUND Cryopreservation of zona pellucida (ZP)-free embryos provides more options for somatic cell nuclear transfer, particularly during handmade cloning. OBJECTIVE This study investigated whether the removal of the ZP affects the development of porcine zygotes after vitrification and warming. MATERIALS AND METHODS We determined the appropriate volume of the corresponding medium for the individual culture of ZP-intact and -free embryos and evaluated the protection effect of ZP during cryopreservation on the resulting development of the vitrified-warmed zygotes. RESULTS The volume of culture medium influenced the development of ZP-intact zygotes, and a volume of 15 µL was most suitable for their development. However, the volume of culture medium did not modify the development of ZP-free zygotes. The removal of the ZP before vitrification did not adversely affect embryonic development or quality of the resulting blastocysts. CONCLUSION Our results suggest that the removal of the ZP does not cause detrimental effects to the development of vitrified-warmed zygotes.