Mito-TEMPO ameliorated TCS-induced oxidative stress in porcine oocytes during in vitro maturation (IVM). Oocyte meiotic maturation was investigated by orcein staining of porcine oocytes treated with only 100 μM TCS, only 0.1 μM Mito-TEMPO (MT), and Mito-TEMPO after TCS pretreatment (TCS + MT) (Supplementary Figure S1b). (a) Summarized table of porcine oocyte meiotic maturation after TCS and/or Mito-TEMPO treatment. Data are presented as the mean ± SD. Different superscript letters indicate significant differences (p < 0.05). (b) Changes in cumulus cell expansion percentage in matured porcine COCs following TCS- and/or Mito-TEMPO treatment. Scale bars = 200 µM. (c) mRNA levels of cumulus cell expansion factors such as Ptx3, Tnfaip6, and Has2 in maturing porcine COCs after Mito-TEMPO and/or TCS treatment (non-treated, only TCS, only Mito-TEMPO: MT and TCS + MT) were measured using RT-PCR. Relative fold changes in the levels of genes were detected after normalization to Gapdh level. Data were analyzed using one-way ANOVA followed by Bonferroni’s multiple comparison test. Differences were considered significant at * p < 0.05, ** p < 0.01, and *** p < 0.001 compared with the control group.