Hydroxyapatite Nanoparticles Enhance In Vitro Maturation of Sheep Oocytes by Attenuating Oxidative Stress

Redox homeostasis plays a pivotal role in maintaining the oocyte’s developmental capacity. However, accumulating evidence indicated that an excessive amount of reactive oxygen species (ROS) was produced during oocyte in vitro maturation (IVM). Therefore, it is necessary to develop strategies for further improving the anti-oxidative potential of IVM oocytes. This study aims to investigate the effects of hydroxyapatite (HA) nanoparticles on redox homeostasis maintenance during ovine oocyte IVM. Additionally, the mechanism underlying the protective role of HA against oxidative stress was systematically analyzed. In this study, HA nanoparticles were introduced at concentrations of 0.1%, 0.3%, and 0.5% during the IVM process. The survival rate of oocytes was assessed to identify the maximum concentration of HA nanoparticles without cytotoxicity after a 24 h culture period. The levels of ROS, glutathione (GSH), mitochondrial membrane potential, and early apoptosis were evaluated to determine the impact of HA nanoparticles on the antioxidant capacity of the oocytes. Furthermore, Smart-RNA sequencing technology was utilized to identify differentially expressed mRNAs (DEMs) induced by nanoparticles during the maturation process. The results indicated that 0.3% HA had no adverse effect on the oocyte survival rate, suggesting its potential applicability in IVM. What’s more, antioxidant capacity assessments revealed that 0.3% HA nanoparticles significantly reduced ROS levels, increased GSH levels, and enhanced mitochondrial membrane potential; however, there was no difference in early apoptosis. Furthermore, a total of 928 DEMs were identified, including 377 upregulated and 551 downregulated mRNAs in oocytes treated with HA. Functional enrichment analysis of the DEMs using GO, KEGG, GSEA, and STEM revealed that HA nanoparticles enhanced oocyte maturation by modulating ROS through thermogenesis signaling pathway. Additionally, core genes such as ATP8, NDUFB10, PPARG, and COX5B were predominantly enriched in the thermogenic pathway.