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.