Impact of stress on oocyte quality and reproductive outcome

Abstract

Stress is an important factor that affects physical and mental status of a healthy person disturbing homeostasis of the body. Changes in the lifestyle are one of the major causes that lead to psychological stress. Psychological stress could impact the biology of female reproduction by targeting at the level of ovary, follicle and oocyte. The increased level of stress hormone such as cortisol reduces estradiol production possibly by affecting the granulosa cell functions within the follicle, which results deterioration in oocyte quality. Adaptation of lifestyle behaviours may generate reactive oxygen species (ROS) in the ovary, which further affects female reproduction. Balance between level of ROS and antioxidants within the ovary are important for maintenance of female reproductive health. Physiological level of ROS modulates oocyte functions, while its accumulation leads to oxidative stress (OS). OS triggers apoptosis in majority of germ cells within the ovary and even in ovulated oocytes. Although both mitochondria- as well as death-receptor pathways are involved in oocyte apoptosis, OS-induced mitochondria-mediated pathway plays a major role in the elimination of majority of germ cells from ovary. OS in the follicular fluid deteriorates oocyte quality and reduces reproductive outcome. On the other hand, antioxidants reduce ROS levels and protect against OS-mediated germ cell apoptosis and thereby depletion of germ cells from the ovary. Indeed, OS is one of the major factors that has a direct negative impact on oocyte quality and limits female reproductive outcome in several mammalian species including human.

Keywords: Female reproductive outcome; Oocyte quality; Oxidative stress; ROS; Stress.

Fig. 1

Schematic diagram showing the impact of stress on reproductive outcome. Environmental changes, pressure and demands and several other factors generate psychological stress. The psychological stress induces lifestyle changes and cortisol production from adrenal gland which directly and indirectly affect the ovarian physiology. The lifestyle changes including alcohol consumption and smoking leads to increase level of ROS. The increased level of ROS results an oxidative stress. The increased cortisol as well as oxidative stress levels affects granulosa cell functions possibly by inducing apoptosis. The granulosa cell apoptosis results in reduced estradiol 17ß biosynthesis in the ovary, which reduces growth and development of follicular oocytes and induces oocyte apoptosis. Apoptosis deteriorates oocyte quality leading to poor reproductive outcome in mammals including human