Abstract

The quality of in vitro produced bovine embryos is lower than those obtained in vivo. The reduction-oxidation (REDOX) state within the embryo in vitro affects not only the energy production required for development, but also the activity of REDOX-sensitive transcription factors, which may alter gene expression patterns. New evidences indicate that induction of oxidative stress with hydrogen peroxide (H2O2) in embryos at the zygote stage results in a significant increase in blastocyst rate. This effect may be related to the selective expression of genes involved in the regulation of cell REDOX. The objective of this work was to determine the rate of embryo development after exposure of bovine oocytes at different concentration of hydrogen peroxide. Therefore, oocytes from slaughterhouse ovaries were matured in TCM-199 supplemented medium for 22-24 hours, at 38.5 ºC, 5% CO2 and humidity at saturation. At the end of the 22-24 hours, the following treatments were applied for 1 hour: 0, 50, 100 and 200 μM H2O2. In vitro fertilization was carried out co-incubating oocytes for 18 hours with a final concentration of 1x106 sperm/mL. The presumptive zygotes were denuded and cultured in KSOM medium-0,4% BSA, to 38.5 °C in an atmosphere of low tension of O2 (5% O2, 5% CO2 and 90% N2) and humidity at saturation. Preliminary results show that the induction of oxidative stress by H2O2 produces a positive effect with 50 μM H2O2 in the embryo development, in comparison to the control. Determining a method for obtaining embryos of better quality and more resistant to oxidative stress could allow a higher survival to the processes of cryopreservation, which generates high levels of oxidative stress in embryos. Acknowledgments: This research was provided by CONICYT-Chile, grant FONDECYT 1130888. Pia Loren’s Doctoral Fellowship by Universidad de la Frontera, Chile.