RGFP966 Exhibits an LH-Like Efficacy in Promoting Tan Sheep Oocyte Maturation and Subsequent Developmental Competence

RGFP966 is a selective inhibitor of histone deacetylase 3 (HDAC3). This study aimed to evaluate whether HDAC3 inhibition could promote in vitro maturation (IVM) and subsequent embryo development in Tan sheep oocytes, and to compare its efficacy with luteinizing hormone (LH). Immunofluorescence analysis revealed that HDAC3 expression was significantly decreased in metaphase II (MII) oocytes compared to the germinal vesicle (GV) stage (P < 0.001). Western blotting verified that RGFP966 suppressed HDAC3 deacetylase activity in Tan sheep granulosa cells, increasing the acetylation of downstream substrates H3K9ac, H3K14ac and H4K5ac (P < 0.01). Treatment with RGFP966 significantly promoted polar body 1 (PB1) extrusion, achieving a maturation rate comparable to the LH-treated group. Mechanistically, RGFP966 treatment significantly enhanced mitochondrial distribution (P < 0.01), upregulated GPX4 expression (P < 0.001), and accordingly reduced intracellular reactive oxygen species (ROS) levels (P < 0.001). Moreover, RGFP966 significantly decreased the rate of spindle/chromosome misalignment (P < 0.001) and reduced early apoptosis (indicated by reduced Annexin-V staining) in MII oocytes (P < 0.001), without inducing additional DNA double strand breaks, as evidenced by unchanged γH2AX levels. Subsequent in vitro fertilization (IVF) demonstrated that the 2-cell cleavage and blastocyst rates of oocytes matured with RGFP966 were comparable to those of the LH group, and the resultant blastocysts exhibited normal expression patterns of lineage markers (CDX2 and SOX2). In conclusion, HDAC3 inhibitor RGFP966 promotes Tan sheep oocyte IVM and subsequent developmental competence with an efficacy equivalent to LH. This process relies on alleviating oxidative stress by enhancing mitochondrial distribution and GPX4 expression, while preserving genomic stability during meiosis. These findings provide a theoretical basis for the potential application of HDAC3 inhibitors as effective additives in ovine IVM systems.