Effect of vitrification and beta-mercaptoethanol on reactive oxygen species activity and in vitro development of oocytes vitrified before or after in vitro fertilization

Objective: To investigate the effect of vitrification and beta-mercaptoethanol (beta-ME) on reactive oxygen species (ROS) activity and in vitro development of oocytes vitrified before or after in vitro fertilization (IVF). Design: Randomized prospective study. Setting: University-based assisted reproductive technology laboratory. Animals(s): Abattoir-derived porcine ovaries. Interventions(s): Oocytes were vitrified either before or 4 hours after the end of IVF by solid surface vitrification (SSV) without centrifugation and/or delipation procedure. beta-ME was used to inhibit ROS activity. Main Outcome Measures(s): Viability was evaluated by membrane integrity and esterase enzyme activity using fluorescein diacetate staining while ROS activity was assessed by 2',7'-dichlorofluorescein assay. Result(s): Vitrification increased the ROS activity and decreased the viability and in vitro development of vitrified oocytes. Addition of beta-ME to vitrification and culture medium partially annihilated the ROS activity but did not improve the viability of vitrified-warmed oocytes. Furthermore, beta-ME had no effect on improving the fertilization ability of oocytes vitrified at metaphase II stage but significantly increased their ability to cleave. beta-ME also increased the rate of cleavage and blastocyst formation ability of oocytes vitrified 4 hours after the end IVF. Conclusion(s): Vitrification increases ROS activity in oocytes that can be partially annihilated by beta-ME to obtain enhanced embryonic development. (Fertil Steril (R) 2010; 93: 2602-7. (C) 2010 by American Society for Reproductive Medicine.)