Several applications of pluripotent stem cell (PSC)-derived cardiomyocytes require elimination of undifferentiated cells. A major limitation for cardiomyocyte purification is the lack of easy and specific cell marking techniques. We found that a fluorescent dye that labels mitochondria, tetramethylrhodamine methyl ester perchlorate, could be used to selectively mark embryonic and neonatal rat cardiomyocytes, as well as mouse, marmoset and human PSC-derived cardiomyocytes, and that the cells could subsequently be enriched (>99% purity) by fluorescence-activated cell sorting. Purified cardiomyocytes transplanted into testes did not induce teratoma formation. Moreover, aggregate formation of PSC-derived cardiomyocytes through homophilic cell-cell adhesion improved their survival in the immunodeficient mouse heart. Our approaches will aid in the future success of using PSC-derived cardiomyocytes for basic and clinical applications.

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Background-Mitochondrial oxidative stress and damage play major roles in the development and progression of left ventricular (LV) remodeling and failure after myocardial infarction (MI). We hypothesized that overexpression of the mitochondrial antioxidant, peroxiredoxin-3 (Prx-3), could attenuate this deleterious process. Methods and Results-We created MI in 12-to 16-week-old, male Prx-3-transgenic mice (TGϩMI, nϭ37) and nontransgenic wild-type mice (WTϩMI, nϭ39) by ligating the left coronary artery. Prx-3 protein levels were 1.8 times higher in the hearts from TG than WT mice, with no significant changes in other antioxidant enzymes. At 4 weeks after MI, LV thiobarbituric acid-reactive substances in the mitochondria were significantly lower in TGϩMI than in WTϩMI mice (meanϮSEM, 1.5Ϯ0.2 vs 2.2Ϯ0.2 nmol/mg protein; nϭ8 each, PϽ0.05). LV cavity dilatation and dysfunction were attenuated in TGϩMI compared with WTϩMI mice, with no significant differences in infarct size (56Ϯ1% vs 55Ϯ1%; nϭ6 each, PϭNS) and aortic pressure between groups. Mean LV end-diastolic pressures and lung weights in TGϩMI mice were also larger than those in WTϩsham-operated mice but smaller than those in WTϩMI mice. Improvement in LV function in TGϩMI mice was accompanied by a decrease in myocyte hypertrophy, interstitial fibrosis, and apoptosis in the noninfarcted LV. Mitochondrial DNA copy number and complex enzyme activities were significantly decreased in WTϩMI mice, and this decrease was also ameliorated in TGϩMI mice. Conclusions-Overexpression of Prx-3 inhibited LV remodeling and failure after MI. Therapies designed to interfere with mitochondrial oxidative stress including the antioxidant Prx-3 might be beneficial in preventing cardiac failure.

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