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The flavonoid-based compound isorhamnetin (ISO) is a 3'-methoxylated derivative of quercetin. This study investigated the effects of various concentrations of ISO on in vitro maturaion (IVM) of porcine oocytes exposed to oxidative stress (200 μM hydrogen peroxide). We examined oxidative stress level, maturation efficiency, cumulus cell expansion, and expression of maturation-related factors during oocyte maturation and subsequent embryo developmental competence and blastocyst quality. Treatment with 2 μM ISO (2 ISO) increased the percentages of surviving oocytes, and cleaved embryos on day 2 and blastocysts on day 7. The glutathione level and mRNA expression of antioxidant-related genes (NFE2L2 and SOD2) were increased in the 2 ISO-treated group, while the reactive oxygen species level was decreased. Treatment with 2 ISO increased mRNA expression of a cumulus cell expansion-related gene (SHAS2) and improved chromosomal alignment. mRNA expression of maternal genes (CCNB1, MOS, BMP15, and GDF9) and MAPK activity were increased in the 2 ISO-treated group. The total cell number per blastocyst and percentage of apoptotic cells were increased and decreased in the 2 ISO-treated group, respectively. Treatment with 2 ISO increased mRNA expression of development-related genes (SOX2, NANOG, and POU5F1) and anti-apoptotic genes (BCL2L1, BIRC5, and BRIC3), and decreased that of pro-apoptotic genes (CASP3 and FAS). These results demonstrate that 2 ISO improves the quality of porcine oocytes by protecting them against oxidative stress during IVM and enhances subsequent embryo development in vitro. Therefore, we propose that ISO is a useful supplement for IVM of porcine oocytes.
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