Expression pattern of various cardiomyogenic markers in CCCs (hiPSC-ECMs culture) by confocal scanning laser microscopy. Localization of key cardiac myocyte phenotypic markers of day 14 hiPSC-ECMs CCC cultures in myocyte maintenance medium (maintenance medium, iCell) demonstrated the expression of cardiac specific structural, contractile, and functional proteins: muscle-specific intermediate filament, desmin (A), cardiac troponin, cTnI (B), cardiac myosin heavy chains, α/β-MHC (C), gap junction proteins, connexon, Cx45 (D), transcription factor, GATA4 (E), and peptide hormone, BNP (F). Immunostaining of hiPSC-ECMs CCC cultures in myocyte medium showed foci of typical elongated strap-like cells with periodic cross-striations, and by means of cellular condensation these myocytes were organized into multilayered functional syncytium (A–F). In some foci, these myocytes were aligned and overlapping with each other in an orderly manner (A–F). Nuclei of these cells were large and either oval or round in appearance, and were centrally positioned. Cells were also stained for nuclei (blue, DAPI). Merged images (A–F). (A–F, scale bar 100 μm).