Roth, Z., Department of Animal Science, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, 76100, Israel
Aroyo, A., Department of Animal Science, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, 76100, Israel, Institute of Animal Science, Agricultural Research Organization, the Volcani Center, P.O. Box 6, BetDagan 50250, Israel
Yavin, S., Department of Animal Science, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, 76100, Israel, Institute of Animal Science, Agricultural Research Organization, the Volcani Center, P.O. Box 6, BetDagan 50250, Israel
Arav, A., Institute of Animal Science, Agricultural Research Organization, the Volcani Center, P.O. Box 6, BetDagan 50250, Israel

Hyperthermia-induced oxidative stress is one of the mechanisms suggested to underlie loss of developmental competence in mouse embryos. In this study, we examined whether pretreatment with the antioxidant epigallocatechin gallate (EGCG) can alleviate the negative effects of hyperthermia on developmental competence of the ovarian pool of oocytes and improve embryonic development. Female mice (CB6F1) were synchronized (eCG + hCG) and injected with 0.4 ml EGCG (100 mg/kg body weight) or with saline. Both EGCG- and saline-treated mice were exposed to heat stress (HS; 40 °C, 65% RH) or kept under normothermal conditions (Control; 22 °C, 45% RH). In vivo-derived zygotes were recovered 20 h after hCG administration and cultured in vitro. Maternal hyperthermia attenuated embryonic cleavage rate in association with further disruption in embryonic early cleavage and subsequently, with embryonic development. While pretreatment with EGCG did not affect the proportion of zygotes that cleaved to the two-cell stage, it appeared to moderate the effect of hyperthermia on both cleavage timing and developmental rate, as reflected by an increased rate of early cleaved embryos and blastocyst formation. Blastocyst developmental competence was also improved, as indicated by the increased total cell number and percentage of embryos that underwent hatching, in association with reduced apoptotic status, as reflected by the percentage of TUNEL-positive cells and intensity of caspase activity for the HS-EGCG embryos vs. HS-saline ones. In summary, while hyperthermia disrupts the competence of the follicle-enclosed oocyte, in vivo administration of the antioxidant EGCG improves developmental competence and the quality of the embryos that develop from these oocytes. © 2008.