Hydroxyapatite nanoparticles improve vitrified bovine MII oocyte developmental competence by reducing ultrastructural...

Area of Science:

• Reproductive Biology
• Nanotechnology in Animal Science
• Cryobiology

Background:

• Vitrification is a common method for preserving bovine oocytes.
• Cryoprotective agents (CPAs) and nanoparticles can mitigate cryoinjury.
• Optimizing nanoparticle-supplemented vitrification solutions is crucial for improving developmental competence.

Purpose of the Study:

• To investigate the impact of hydroxyapatite (HA) nanoparticles and cryoprotectant concentrations on bovine oocyte ultrastructure, developmental competence, and gene expression post-vitrification.
• To determine optimal HA nanoparticle conditions for enhancing oocyte survival and development.
• To evaluate the synergistic effects of HA nanoparticles and CPAs on oocyte quality and gene expression.

Main Methods:

• Bovine oocytes at metaphase II were vitrified using solutions with varying HA nanoparticle sizes (20, 40, 60 nm) and concentrations (0.01%, 0.05%, 0.1%).
• Survival rates, mitochondrial membrane potential (MMP), and developmental competence (cleavage and blastocyst rates) were assessed.
• Ultrastructural integrity, MMP, and expression of specific genes (ND5, ATPase8, ZP3, KRT8, COX1) were analyzed under optimal and synergistic conditions.

Main Results:

• The optimal condition identified was 40 nm HA nanoparticles at 0.05% concentration, significantly improving MMP, cleavage, and blastocyst rates compared to controls.
• The VS1-HA group (17.5% EG, 17.5% DMSO, with HA) showed the highest cleavage (43.67%) and blastocyst rates (15.19%), with reduced ultrastructural damage.
• Significant increases in mRNA levels for mitochondrial genes ND5 and ATPase8, and ZP3 were observed in the VS1-HA group compared to the vitrification solution (VS) group.

Conclusions:

• Hydroxyapatite nanoparticles effectively mitigate cryoinjury in vitrified bovine oocytes.
• Optimized HA nanoparticle supplementation and cryoprotectant formulations improve oocyte ultrastructure, mitochondrial function, and developmental potential.
• HA nanoparticles enhance the expression of key genes involved in mitochondrial function and zona pellucida formation, contributing to improved cryopreservation outcomes.