[Regulatory role and mechanism of HSD3B7 in bovine follicular development]

This study aimed to explore the regulatory effect and mechanism of 3β-hydroxy-Δ⁵-C₂₇-steroid oxidoreductase (HSD3B7) on bovine follicular development. Bovine primary granulosa cells (GCs) with HSD3B7 knockdown and overexpression were constructed, and the proliferation efficiency of GCs was examined by the cell counting kit-8 (CCK-8) method. Annexin V-EGFP/PI double staining was performed to detect the apoptosis level of GCs. The concentration of estradiol (E₂) in the culture medium and that of 2-methoxyestrone in GCs were determined by enzyme-linked immunosorbent assay (ELISA). The relative expression levels of the CCND2, Bim, Caspase-3, CYP19A1 and STAR were determined by qRT-PCR. The protein levels of related genes were determined by Western blotting. The results showed that HSD3B7 knockdown decreased the proliferation efficiency and CCND2 expression level of primary bovine follicular GCs, promoted the apoptosis, and increased Bim and Caspase-3 expression in GCs. Additionally, it decreased E₂ secretion and CYP19A1 and STAR expression, and increased the concentration of 2-methoxyestrone, the main metabolite of E₂. The opposite results were obtained after HSD3B7 overexpression. These results suggested that HSD3B7 positively regulated the development of bovine follicles by promoting the proliferation and E₂ secretion and inhibiting the apoptosis of GCs. The results provide a new theoretical basis for further understanding the molecular regulatory network of bovine follicle development, and also lay a foundation for related research and practical application to improve bovine reproductive efficiency.