Oxidative stress and oocyte microenvironment


Females inherit a reservoir of around 300,000 primordial follicles, with primary oocytes arrested at the first meiotic division. They attain maturation into the functional phase toward diversity periodically every month by regulators that govern them to survive or lead them toward apoptosis. As a consequence, few attain completion and reach ovulation to be fertilized by male gametes. In order to complete the development, a number of genetic, epigenetic, and cytoplasmic modifications occur before fertilization. Preservation of the ovarian pool is thus a very important factor that is subject to insult by a number of extrinsic and intrinsic factors.

Redox environment of the ovaries

The free radical theory of aging implies that reactive chemical species are indispensable for the prevention of oxidative damage with increasing age, leading to atresia of the follicles and aged oocytes. Oxidative imbalance due to mitochondrial dysfunction may result in chromosomal segregation disorders, fertilization failures, formation of fragmented oocytes, and fragmentation of the embryos. The normal mechanism of the male and female reproductive systems requires a controlled redox activity and an increase in reactive oxygen species (ROS) may lead to subfertility.

Oxidant and antioxidant system

The moderate escalation of ROS acts favorably for oocyte maturity. Nevertheless, higher levels worsen the oocyte quality, thus impacting the reproductive capability. Free radicals are continually released by the mitochondria during the process of energy production. The preservation of the oxidative environment is essential for the natural development of oocytes, cell integrity, and hormonal activities. Free radical oxidation can contribute to follicular atresia and aged oocytes.

OS and ovarian reserve

The increase in age and psychological stress are the two most important factors that influence the fertilizing capacity of the oocytes. With the approach of menopause, there is a decline of the ovarian reserve that affects the normal cyclic hormonal process and the functional capacity of the oocytes required for fertility.

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