Antifreeze protein type I preserves mitochondrial activity in in vivo-derived sheep embryos after cryopreservation: a stage-dependent effect

This study assessed, in sheep, the effects of antifreeze protein (AFP) type I on redox balance at different embryonic stages by measuring mitochondrial activity (MITO), reactive oxygen species (ROS), and glutathione (GSH) levels in the same embryos immediately before cryopreservation and after warming. A total of 45 GI-GII embryos were divided into morulae (MO; n = 18) and blastocysts (BL; n = 27), and then, each group was subjected to slow freezing in a solution containing 0.1 μg/mL AFP I or not. In the MO-CONT group, cryopreservation reduced (P < 0.05) GSH levels and MITO, whereas ROS levels remained unchanged. In contrast, no differences (P > 0.05) were observed between pre- and post-cryopreservation in the MO-AFP group. Interestingly, the MO-AFP exhibited higher (P < 0.05) MITO than the MO-CONT group. In blastocysts, cryopreservation led to reductions (P < 0.05) in ROS, GSH levels, and MITO. In conclusion, AFP I supplementation preserved MITO in sheep morula embryos following cryopreservation, suggesting a stage-dependent protective effect.