Induction of oxidative stress does not increase the cryotolerance of vitrified embryos.

Short-term treatment of mammalian oocytes with different stressors induces stress tolerance of embryos derived from these oocytes. The aims of this study were to evaluate effects on embryo development when there was treatment of oocyte complexes (COCs) used to derive the embryos with hydrogen peroxide (HO).The COCs were not incubated with HO: control (0 μM), or were incubated with 25, 50, 75, or 100 μM concentrations of HO for 1 h prior to in vitro fertilization, and presumptive zygotes were cultured until day 7. Blastocysts at day 7 of development derived from HO-treated (25 μM treatment concentration) COCs were vitrified. Percentage of embryos undergoing cleavage was not affected by any treatment, while percentage of embryos developing to the blastocyst stage was less when there was treatment of COCs with 100 μM of HO. Embryo quality was less when COCs used to derive blastocysts were treated with 50, 75, or 100 μM concentrations of HO. There were lesser relative abundances of some mRNA transcripts of interest in blastocysts when there was treatment of COCs with HO. After vitrification, there were no differences in embryo re-expansion and hatching rates compared with fresh and vitrified blastocysts of the control group and those derived from COCs treated with 25 μM HO. In conclusion, treatment of COCs used to derive blastocysts with HO does not induce stress tolerance in vitrified embryos of cattle; however, the viability of these blastocysts is similar to those of the control group.