Abstract

Introduction The qualities of embryos generated by in vitro methods are lower than those embryos derived in in vivo procedures. The reduction-oxidation state (REDOX) affects not only energy production required for embryonic development, but also transcription factors that can alter the pattern of gene expression. Induction of oxidative stress with hydrogen peroxide (H2O2) in mature oocytes generates an increase in the blastocyst rate. This effect would be related to the selective expression of genes involved in the regulation of cellular redox. The aim of this study was to determine the rate of embryonic development after exposure of bovine oocytes at different concentrations of H2O2. Methods Bovine oocytes from slaughterhouse ovaries were matured in TCM-199 medium supplemented for 22 hours at 38.5°C, 5% CO2 and humidified atmosphere. At the end of 22 hours, the following treatments were applied for 1 hour: 0, 50, 100 and 200 μM H2O2. The in vitro fertilization was performed co-incubating oocytes 18 hours with a final concentration of 1×106 sperm/mL. The presumptive zygotes were denuded and cultured in KSOM-0.4% FAF-BSA medium at 38.5°C under low O2 tension (5% O2, 5% CO2 and 90% N2) and humidified atmosphere. Results Induction of stress with H2O2 did not produce differences in cleavage rate at 72 hrs using 50 and 100 μMH2O2 compared to control, whereas 200 μMH2O2 generated a significant decrease in assessing the rate of blastocyst (7 days) no differences was observed when using 50 μMH2O2 compared to control. However, when using 100 and 200 μM, blastocyst rate decreases dramatically. Conclusion The induction of oxidative stress with 50 μM H2O2 maintaining a proper embryonic development. It is possible that these embryos resistant to oxidative stress it can have a higher survival cryopreservation processes that generate high levels of reactive oxygen species in embryos. Grants: Supported by FONDECYT 1130888, CONICYT, Gobierno de Chile, Chile.