Inhibition of Follicular Development Induced by Chronic Unpredictable Stress Is Associated with Growth and Differentiation Factor 9 and Gonadotropin in Mice1

Abstract

Chronic psychosocial stress negatively affects ovarian function. Ovarian follicular development is regulated by both pituitary-derived gonadotropins and intraovarian regulatory factors. To date, the suppressive effects of chronic stress on the ovary have been observed to be manifested mainly as an inhibition of gonadotropin release. It is not clear whether there are any other intraovarian regulatory mechanisms involved in this process. Growth and differentiation factor 9 (GDF9) is an important, oocyte-specific paracrine regulator required for follicular development. In this study, the chronic unpredictable mild stress model was used to produce psychosocial stress in mice. The number of different developmental stages of follicles was counted on ovarian sections stained with hematoxylin and eosin. Real-time PCR and Western blotting were used to detect the mRNA and protein levels, respectively, of GDF9. The results show that chronic unpredictable stress inhibits follicular development, increases follicular atresia, and suppresses GDF9 expression. Exogenous gonadotropin treatment partly restores the repressed antral follicular development, but has no effect on the repressed secondary follicular development associated with chronic stress. Treatment with recombinant GDF9 restores secondary follicular development. Cotreatments with GDF9 and gonadotropins restore both secondary and antral follicular development in stressed mice. These findings demonstrate that inhibition of follicular development induced by chronic unpredictable stress is associated with GDF9 and gonadotropin.

Chronic Unpredictable Stress Decreases Expression of Brain-Derived Neurotrophic Factor (BDNF) in Mouse Ovaries: Relationship to Oocytes Developmental Potential

“…The open field activity of the mice in our study implicated that the mice were in an anxious emotional and psychological state after chronic unpredictable stress. These data is consistent with our previous study [9], [15]. Consistent with the previous report [14], the animal model in our study also showed signs of increased activity in the HPA axis, including increased CRH neurons in PVN of hypothalamus and corticosterone hypersecretion from adrenal.…”

“…Previous studies by our group [9] and others [10] had found that chronic stress leads to follicular maldevelopment [9], [10]. A growing body of evidence demonstrated that chronic stress decreases the expression of BDNF in limbic structures in the central nervous system, which may contribute to mood disorder[11]–[13].…”

“…However, this does not occur when rodents are exposed to unpredictable stress. A classic stressed model was induced by chronic unpredictable mild stress [9], [14], [15]. The study was conducted in compliance with Ethics Committees on Animal Research of Anhui Provincial Hospital Affiliated to Anhui Medical University.…”

“…the initial activity of a animal placed in novel surroundings has long been taken as an indicator of its emotional and psychological state [17]. Protocols of open field test were previously approved [9]. The open field test was performed 12 h after ceasing the chronic stress procedure between the second and fifth hours of the dark phase.…”

“…The expression of BDNF was quantified by measuring the average optical density (OD) in different stages of follicles. The follicles were classified into four stages according to the modified Oktay system [9]: ‘primordial follicle’  = an oocyte that was encapsulated by flattened pre-granulosa cells; ‘primary follicle’ = when at least one of the pre-granulosa cells has become columnar or cubic until they form a single layer of cubic granulosa cells; ‘secondary follicle’ = when the oocyte is encapsulated by two or more layers of granulosa cells without antrum formation; and ‘antral follicle’ = when the oocyte is encapsulated by more than two layers of granulosa cells and an antrum has formed. Total areas of follicles were analyzed, including areas of granulosa cells, the antrum and oocyte.…”