Sodium Butyrate Promotes In Vitro Development of Mouse Preantral Follicles and Improves Oocyte Quality by Regulating Steroidogenesis, Oxidative Stress, and Cytoskeleton Remodeling

Sodium butyrate (NaBu), a common feed additive, has been shown to enhance reproductive performance in livestock and poultry. However, whether NaBu exerts this effect by directly regulating follicular development remains unclear. In this study, a three-dimensional (3D) in vitro culture system of mouse preantral follicles was used to investigate the effects of NaBu on follicular growth, hormone secretion, maturation of oocytes, and subsequent embryonic development. Preantral follicles were treated with different doses of NaBu on the fourth day of culture. Subsequently, the mature oocytes (MII stage) were released from the follicles on the ninth day and subjected to parthenogenetic activation for developmental assessment. The results showed that 0.10 mM NaBu treatment could significantly promote follicular growth, antral formation, and oocyte maturation. Furthermore, NaBu also significantly increased estradiol (E₂) secretion, improved follicular structure, and maintained cellular viability. qPCR analysis revealed that NaBu significantly increased the mRNA levels of <i>STAR</i>, <i>CYP11A1</i>, and <i>CYP1B1</i>. In addition, it significantly enhanced the distribution and organization of F-actin, with increases in the mRNA levels of <i>GDF9</i>, <i>BMP15</i>, and <i>CX37</i>. NaBu treatment significantly reduced intracellular ROS levels and increased the mRNA levels of <i>NRF2</i> and <i>SOD1</i>, while <i>SOD2</i> and <i>GSR</i> showed increasing trends without significant differences. NaBu significantly improved oocyte cytoskeletal organization and the morphology of the spindle, but it did not lead to a significant increase in the rates of cleavage and blastocyst formation after parthenogenetic activation. Collectively, these findings indicate that NaBu promotes follicular development and improves oocyte quality, at least partly, by enhancing steroidogenesis, alleviating oxidative stress, and maintaining cytoskeletal integrity, providing insight into its potential application for improving reproductive performance in livestock and poultry.