Equilibrium between anti-oxidants and reactive oxygen species: a requisite for oocyte development and maturation

Abstract

Reactive oxygen species (ROS) are required for cellular functioning and are controlled by anti-oxidants. The ROS influence the follicles, oocytes, endometrium, and their environment. The luteinizing hormone surge initiates a massive recruitment of ROS that modulates major reproductive functions namely, oocyte maturation, ovarian steroidogenesis, corpus luteal function, and luteolysis. The anti-oxidant system balances ROS generation and maintains the cellular functions. Both enzymatic and non-enzymatic anti-oxidants namely, vitamins and minerals are present in the follicles and protect the oocytes from the damaging effects of ROS. The overproduction of ROS leads to oxidative stress that affects the quality of oocytes and subsequent anovulation. Although researchers have tried to establish the role of ROS and anti-oxidants in oocyte development, still this aspect needs to be revisited. This review discusses the importance of the ROS and anti-oxidant balance that is required for the development and maturation of oocytes. There are increasing data on the activity of ROS and anti-oxidants in supporting oocyte development and maturation. However, extensive research is required to identify the safe physiological concentration and duration of both the ROS and anti-oxidants that are required to facilitate oocyte development and maturation during in vitro and in vivo conditions.

Keywords: anovulation; anti‐oxidants; oocyte maturation; ovulation; reactive oxygen species.

Figure 1

Follicular growth during the process of ovulation. (A) A balance in reactive oxygen species (ROS) and anti‐oxidants is required during follicular maturation, follicular atresia, and the growth of the dominant follicle and (B) an imbalance in ROS and anti‐oxidant generation lead to ovulatory dysfunction. GPx, glutathione peroxidase; H₂O₂, hydrogen peroxide; O₂ ⁻, superoxide; SOD, superoxide dismutase