α-Lipoic acid supplementation during in vitro maturation improves bovine oocyte developmental competence and...

Oxidative stress during in vitro maturation (IVM) impairs oocyte quality, thereby limiting fertilization and embryonic development in bovine in vitro embryo production. This study investigated whether α-lipoic acid (ALA) supplementation during IVM modulates the intracellular redox and mitochondrial status of bovine oocytes and whether these changes are associated with subsequent developmental competence and blastocyst quality. Cumulus-oocyte complexes were matured with 0, 50, 100, or 200 μM ALA, followed by in vitro fertilization and culture. Intracellular reactive oxygen species, glutathione levels, mitochondrial membrane potential, mitochondrial content, and early apoptosis were assessed in matured oocytes, while blastocyst development, apoptosis, ICM and TE cell numbers, and gene expression were evaluated after embryo culture. Treatment with 50 μM ALA significantly reduced intracellular reactive oxygen species and increased glutathione levels. It also increased mitochondrial membrane potential and mitochondrial content while reducing early apoptosis. Blastocyst formation significantly increased in the 50 μM group, whereas 200 μM ALA impaired oocyte maturation, fertilization, and subsequent embryo development. At the blastocyst stage, embryos derived from 50 μM ALA-treated oocytes exhibited an increased inner cell mass cell number and reduced apoptosis. These improvements were accompanied by increased expression of BCL2, BIRC5, GPX1, SOX2, and GLUT1. Collectively, these findings show that the improved developmental competence associated with ALA supplementation during bovine IVM is accompanied by favorable changes in oocyte redox and mitochondrial status, reduced apoptosis, and improved subsequent blastocyst quality.