Metabolomic and Transcriptomic Changes in Porcine Cumulus–Oocyte Complexes Following Vitrification: Cysteinyl-Glycine as an Antioxidant Enhances the Quality of Vitrified Oocytes

Vitrification is an efficient approach to preserve porcine germinal vesicle (GV)-stage oocytes, yet cryo-induced damage remains a major limitation to subsequent embryonic development. Although previous studies have investigated transcriptomic and proteomic changes in oocytes and cumulus cells (CCs) following vitrification, the metabolic alterations underlying cryoinjury are poorly understood. In this study, metabolomic profiling of vitrified oocytes and CCs following in vitro maturation (IVM) was carried out identify key differential metabolites. Functional validation was further conducted by supplementing candidate metabolites during oocyte maturation. In vitrified oocytes, 19 metabolites were significantly upregulated, and 44 were significantly downregulated. Integrated metabolomic and transcriptomic profiling demonstrated that significantly altered metabolites and genes converged on biological pathways governing energy metabolism, glutathione metabolism, and glycerophospholipid metabolism. In CCs derived from vitrified oocytes, 70 metabolites exhibited marked upregulation, while 21 showed significantly downregulation. Integrated analysis profiling demonstrated that significantly altered metabolites and genes were converged on pathways such as glutathione metabolism and glycerophospholipid metabolism. Notably, oocytes and CCs shared 28 differentially expressed metabolites, among which cysteinyl-glycine (Cys-Gly) was significantly reduced in both oocytes and CCs following vitrification. Supplementing IVM with Cys-Gly improved vitrified oocyte quality, as evidenced by reduced oxidative stress, suppressed excessive apoptosis and aberrant autophagy, enhanced embryonic development, and increased cumulus expansion. Collectively, these findings provide a comprehensive metabolic profile of porcine GV oocytes and CCs after vitrification, offering new insights into the mechanisms of oocyte cryoinjury. Targeting key metabolic pathways or supplementing specific metabolites, such as Cys-Gly, may represent a promising strategy to improve the viability of vitrified porcine oocytes.