Winter-associated downregulation of ovarian NR5A2 correlates with impaired follicle development in the striped hamster (Cricetulus barabensis)

To investigate the role of Nuclear receptor subfamily 5, group A, member 2 (NR5A2) in the seasonal regulation of follicle development in striped hamsters (Cricetulus barabensis), we collected 32 adult females, eight individuals from each season (spring, summer, autumn, and winter). Hematoxylin and eosin (H&E) staining was performed to quantify seasonal variations in follicle numbers across distinct developmental stages. Serum concentrations of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), as well as fecal concentrations of estradiol (E2) and progesterone (P4), were measured using enzyme-linked immunosorbent assay (ELISA). Ovarian NR5A2 mRNA levels were quantified by real-time quantitative PCR (qPCR). Spearman's correlation analyses were conducted to examine associations between ovarian NR5A2 mRNA levels and follicle counts at each developmental stage, as well as between NR5A2 mRNA levels and serum and fecal reproductive hormone concentrations. The numbers of follicles at different developmental stages and ovarian NR5A2 mRNA levels exhibit pronounced seasonal variation (P < 0.01). Specifically, primary follicle counts peak in winter, whereas secondary and antral follicle numbers reach their seasonal minima during this period. Concurrently, ovarian NR5A2 mRNA levels in winter are significantly lower than those in spring, summer, and autumn (P < 0.01). Serum concentrations of GnRH, FSH, and LH, as well as fecal concentrations of E2 and P4, also display significant seasonal differences, all five hormones being markedly lower in winter compared with the other three seasons (P < 0.01). Furthermore, NR5A2 mRNA levels and fecal E2 and P4 concentrations were negatively correlated with primary follicle number but positively correlated with secondary and antral follicle numbers, suggesting that NR5A2, E2, and P4 collectively facilitate the transition from the primary to more advanced follicle stages. These findings indicate that winter environmental conditions suppress overall follicle development in striped hamsters, and the concomitant downregulation of ovarian NR5A2, correlating significantly with follicle counts, suggests a functionally relevant role for this transcription factor in seasonal follicle development. These results provide a theoretical foundation for ecologically sustainable population management strategies, supporting the rational design of targeted interventions, such as pharmacological agents, that selectively modulate population size in the target species while minimizing off-target effects on non-target organisms.