The Impact of Reactive Oxygen Species on Early Human Embryos: A Systematic Review of the Literature
Sajal Gupta, Jashoman Banerjee, Ashok Agarwal
Abstract: Oocytes and embryos are constantly exposed to oxidative stress which influences their developmental competence. But, the antioxidants present in the reproductive tissues protect the embryos in vivo. The effects of oxidative stress in Assisted Reproductive Technology (ART) is amplified by lack of physiological defense by the antioxidants and also due to abundance of potential sources that can generate Reactive Oxygen Species (ROS) in culture media. Certain levels of ROS are necessary for sperm function,normal activity in the ovarian follicle, normal sperm-oocyte interaction and sperm capacitation. But, excessive levels may have adverse effects on sperm DNA, fertilization and embryo quality. ROS not only accelerate apoptosis in the cell by direct DNA damage, but also affect the DNA repair mechanisms along with alterations in important check points in cell cycle. In-vitro developmental arrests are documented in mammalian embryos that are exposed to oxidative stress. Hence blastocyst development in vitro lags behind blastocyst development in vivo. Sperm DNA damage caused by elevated ROS levels results in embryo development arrest and poor fertility outcomes with ART. This article reviews the literature on the sources of ROS generation in ART setting and enumerates strategies to overcome oxidative stress.
