Expression pattern of various cardiogenic markers in GFP-BMSCs/ECMs containing myotube constructs by confocal microscopy. Immunostaining of key cardiac myocyte phenotypic markers of day 21 embryonic cardiac myocytes (ECMs) and green fluorescent protein labeled bone marrow stromal cells (GFP-BMSCs) tube co-cultures in basal medium demonstrated the expression of contractile proteins, α/β-MHC (A-C), cTnI (G-I), the adherent junction protein, N cadherin (D-F) and GFP (A, C, D, F, G, I). The transdifferentiated GFP-BMSCs were delineated by their co-localization signals (yellow). Nuclei of these cells were large and either oval or elongated and fusiform in appearance and were centrally placed. Cells were also stained for nuclei (blue, DAPI) and GFP-BMSCs (green, GFP). Images (G-I) show a projection representing 16 sections collected at 10 μm intervals (150 μm). Merged images (A-I). (A-I scale bar 50 μm).