Cardiomyogenic potential of porcine skeletal muscle-derived interstitial progenitor cells (PICs). (A): Immunocytochemistry of PIC-derived cardiospheres reveals positive staining for the cardiac stem-progenitor markers MEF2C, c-kit, and Nkx2.5 after 4 days of differentiation. (B): Immunocytochemistry, performed after 14 days of myocardial differentiation, reveals positive staining for the cardiac-specific markers, α-sarcomeric actin, Nkx2.5, cardiac troponin I, and connexin-43. Scale bars = 50 μm. (C): Quantitative real-time polymerase chain reaction (qRT-PCR) analysis at day 14 confirms upregulation of CONNEXIN-43, ACTC1, and MLC2V together with downregulation of stemness transcripts, following myocardial differentiation, relative to undifferentiated controls, two-way analysis of variance. *, p < .05. Abbreviations: α-sarc, α-sarcomeric actin; DAPI, 4′,6-diamidino-2-phenylindole.