Reactive oxygen species attenuation improves the quality of vitrified-warmed bovine embryos

The aim of this study was to investigate the effects of modulating reactive oxygen species (ROS) in vitrified bovine in vitro produced (IVP) embryos. In experiment I we compared ROS production in fresh and vitrified-warmed blastocysts. In experiment II we evaluated the effects of antioxidant supplementation (100 μM of 2-mercaptoethanol; BME; 0 h to 2 h during warming) on ROS levels in vitrified-warmed blastocysts, and in experiment III we compared the development of fresh and vitrified-warmed blastocysts in the presence (BME) or absence (Control) of antioxidant (100 μM BME; 0 h to 48 h during warming). Higher ROS production (Fresh: 68.48 ± 7.92 vs Vitrified: 123.53 ± 13.15; P<0.05) and lower cell number was observed in vitrified compared to fresh embryos (Fresh: 123.01 ± 5.67 vs Vitrified: 103.04 ± 4.25; P<0.05). Antioxidant supplementation reduced ROS levels (Vitrified: 38.24 ± 1.27 vs. Vitrified/BME: 33.54 ± 1.08; P<0.05) and increased cell number in treated embryos (Vitrified: 100.65 ± 3.98 vs. Vitrified/BME: 112.95 ± 3.72; P<0.05). No differences were observed in the re-expansion rates of vitrified embryos cultured in the absence and presence of BME at 0, 2, and 4 h after warming (P>0.05). The embryo hatching rate did not differ (P>0.05) among embryos from the fresh, vitrified and vitrified/BME groups. However, the total cell numbers were higher (P<0.05) in vitrified embryos supplemented with BME (143.02 ± 6.97) than in vitrified embryos without BME (113.25 ± 5.09) but similar (P>0.05) to that observed in fresh embryos cultured with (150.54 ± 8.99) and without BME (142.71 ± 13.60). It was concluded that the vitrification and warming processes increased ROS levels in blastocysts and its attenuation with BME antioxidant improved embryonic quality.