Effects of Vitamin C, Rosmarinic Acid, or Quercetin on Fertilisation-Related Gene Expression in Porcine Cumulus-Oocyte Complexes During In Vitro Maturation.

Antioxidant supplementation during in vitro maturation (IVM) has been proposed as a strategy to influence transcriptional responses in oocytes and cumulus-oocyte complexes. In this study, we investigated whether vitamin C, rosmarinic acid, or quercetin influence the expression of key fertilisation-associated genes (CD9, ITGA6, MFGE8, ZP2, and ZP3) in porcine cumulus-oocyte complexes (COCs). COCs were classified into three intrinsic quality groups (I-III) and matured in the presence or absence of antioxidants. Gene expression was quantified by RT-qPCR and analysed using a two-way ANOVA model to assess the effects of COC quality and treatment. ZP2 and ZP3 transcript levels were consistently lower in class II and III COCs than in class I controls (p < 0.001). Antioxidant supplementation was associated with treatment- and quality-dependent differences in gene expression. Quercetin was associated with the most pronounced upregulation, with Q I increasing ZP2 expression to 2.95-fold and ZP3 to 2.43-fold relative to class I controls (p < 0.001). Vitamin C was also associated with increased transcript abundance across several treatment groups, including class II and class III COCs, whereas rosmarinic acid exhibited more moderate and gene-specific effects. In contrast, MFGE8 expression, which was elevated in lower-quality COCs, was reduced in antioxidant-treated class II and III complexes. These findings provide transcript-level evidence that antioxidant exposure during IVM is associated with treatment- and quality-dependent changes in fertilisation-related gene expression in porcine COCs.