Effects of oxygen concentration and antioxidants on the in vitro developmental ability, production of reactive oxygen species (ROS), and DNA fragmentation in porcine embryos

Abstract

After in vitro maturation and fertilization of porcine oocytes, the fertilized embryos were cultured under 5 or 20% oxygen (O 2) for 7 days. In embryos cultured under 5% O 2 versus 20% O 2, development to the blastocyst stage was higher (36.3% versus 22.5%, P<0.05); the hydrogen peroxide (H 2O 2) content as a reactive oxygen species was lower (92 pixels versus 111 pixels, P<0.05); and fragmentation of DNA in 8- to 16-cell stage embryos (estimated by the comet assay) resulted in a shorter ( P<0.05) DNA tail (36 μm versus 141 μm). Antioxidants such as β-mercaptoethanol (β-ME) and Vitamin-E (Vit-E) suppressed oxidative damage in the embryos and improved their developmental ability. For embryos cultured under 20% O 2, there were the following differences ( P<0.05) between embryos exposed to 0 μM versus 50 μM β-ME: 28% versus 57% developed to the blastocyst stage; 125 pixels versus 98 pixels per embryo in H 2O 2 content; and a DNA tail of 209 μm versus 105 μm. In addition, for embryos cultured under 20% O 2, there were also differences ( P<0.05) between those exposed to 0 μM versus 50 μM of Vit-E: 28% versus 40% rate of development to the blastocyst stage; 28.9 cells versus 35.9 cells in the expanded blastocyst; 122 pixels versus 95 pixels per embryo (H 2O 2 content); and 215 μm versus 97 μm length of the DNA tail. Therefore, a low O 2 concentration during in vitro culture of porcine embryos decreased the H 2O 2 content and, as a consequence, reduced DNA fragmentation, and, thereby, improved developmental ability.