HDAC1 in the Ovarian Granulosa Cells of Tan Sheep Improves Cumulus Cell Expansion and Oocyte Maturation Independently of the EGF-like Growth Factors

Previous research has demonstrated that certain histone deacetylases (HDACs) have varied roles in the regulation of ovarian somatic cell development, oocyte maturation, and early embryonic development across different species, including sheep. This study aimed to determine whether HDAC1 also plays a critical role in regulating oocyte maturation in Tan sheep. The findings revealed that HDAC1 is expressed in the nuclei of both granulosa cells and oocytes within the growing follicles of Tan sheep ovaries. However, LH induction in cultured granulosa cells did not affect HDAC1 levels. Moreover, specific inhibition of HDAC1 using pyroxamide did not significantly alter the expression levels of EGF-like growth factors NSC 696085 in vitro. Still, pyroxamide significantly inhibited both cumulus expansion and oocyte maturation in cultured cumulus-oocyte complexes (COCs). Additionally, the number of histone acetylation sites (H4K5, H4K12, H3K14, and H3K9) in ovarian granulosa cells was significantly increased. In conclusion, the consistent expression of HDAC1 in growing follicles of Tan sheep may be crucial for supporting oocyte growth and maturation, though it may not be closely linked to LH induction or directly impact the expression of EGF-like factors. Our study suggests that different HDACs may have diverse functions in regulating female reproduction in sheep.