Investigation of the Effect of Crowding Stress on Mice Oocyte Parameters and Reproductive Organs

Background and Aim: Stress is known to affect many reproductive variables, including gonadotropins and sex steroid levels. Stressors such as crowding can alter the normal function of the ovaries, fallopian tubes, and uterine cycles. In the this study, we investigated the effect of crowding stress on mice oocyte parameters and reproductive organs. Materials and Methods: Mice were divided into control, low & high- density crowding stress groups, and kept under stres condition for one month. Superovulation was induced in the mice in all groups by pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG). The mice were sacrificed 15 hours after hCG injection. Grade I and IV oocytes were stained with the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method after collection and evaluation. Ovarian, fallopian tubes and uterine horns tissues were evaluated after staining with hematoxylin and eosin (H&E). Data were analyzed by ANOVA. p-value ≤0.05 was considered significant. Results: The number of grade I and the size of grades I and IV oocytes in the high-density crowding stress group were significantly decreased compared to those in the control group. The rate of DNA fragmentation of grade I and IV oocytes in the low and high- density crowding stress groups demonstrated a significant increase compared to that in the control group. The number of monolayer primary follicles and the height of the fallopian tube epithelium significantly decreased in the high- density crowding stress group compared to those in the control group (p≤0.05). Conclusion: Crowding as an environmental stress can affect DNA fragmentation by inducing irregularities in follicular and oocyte development.