HDAC2-Specific Inhibitor Santacruzamate A Inhibits Mouse Preantral Folliculogenesis Through Granulosa Cell Apoptosis and Oocyte Meiosis Interference

Histone deacetylase 2 (HDAC2)-mediated epigenetic modifications play a crucial role in oogenesis, yet the regulatory mechanisms of HDAC2 throughout the entire process of folliculogenesis remain elusive. In the present study, the localization and expression of HDAC2 were detected in mouse ovaries at distinct postnatal ages and after gonadotropin treatment. The effects and molecular mechanisms of Santacruzamate A (SCA), a selective HDAC2 inhibitor, on folliculogenesis were investigated via an in vitro 3D culture model of mouse preantral follicles. The results showed that HDAC2 was localized in the nuclei of both ovarian granulosa cells and oocytes. Its expression was gradually increased with ovarian development in mice aged from postnatal day 7 to 21, and significantly decreased after 12 h hCG treatment. In follicles cultured in vitro, HDAC2 expression peaked on day 4 of culture. SCA exerted stage-specific and dose-dependent regulatory effects on folliculogenesis. SCA significantly suppressed follicular growth, blocked antrum formation, and triggered follicular atresia. Mechanistically, SCA promoted ovarian granulosa cell apoptosis via increases in pro-apoptotic genes BAX and Caspase-3 levels, and a decrease in anti-apoptotic gene BCL-2 level. Furthermore, SCA disrupted the structural integrity of the follicular microfilament cytoskeleton, interfered with the levels of genes related to oocyte–granulosa cell communication including CX37 and GDF9, caused abnormalities in oocyte spindle structure, chromosome alignment, mitochondrial distribution, and decreased mitochondrial membrane potential (ΔΨm). In conclusion, HDAC2 participates in the transcriptional regulation of mouse folliculogenesis through dynamically changing expression at distinct developmental stages. HDAC2 exerts stage-specific regulatory effects on follicular growth and oocyte maturation, and its mechanisms are associated with maintaining granulosa cell survival, ensuring cytoskeletal integrity, and preserving oocyte mitochondrial function. This study advances our understanding of epigenetic regulation of folliculogenesis and provides novel targets and an experimental basis for optimizing in vitro follicular culture systems and regulating female reproductive performance.