Diminished ovarian reserve induced by chronic unpredictable stress in C57BL/6 mice

Chronic psychological stress has been considered to be a remarkable contributor to diminished ovarian reserve (DOR). However, there is a lack of a psychological stress-induced DOR animal model. We aim to validate the effects of an 8-week chronic unpredictable stress (CUS) paradigm on the ovarian reserve and reproductive hormone secretion of C57BL/6 mice. We found that after an 8-week CUS exposure, the numbers of primordial and preantral follicles and corpus luteum were significantly decreased in CUS model mice. Model mice also presented higher serum follicle-stimulating hormone, corticosterone levels and lower luteinizing hormone, estradiol, testosterone, anti-Müllerian hormone levels compared to those of control mice. Furthermore, we found that FSH receptor and AMH proteins were downregulated in model mouse ovaries. Although a significant litter size difference between the two groups was not found, the ovarian reserve remained significantly lower in the model group 6 weeks after CUS exposure. These results validated the hypothesis that the 8-week CUS paradigm that we adopted could induce the DOR phenotype in C57BL/6 mice and probably had a long-term adverse effect on ovarian reserve. Therefore, our results indicate that we have successfully established an animal model of psychological stress-induced DOR that can be used for further study.