Generation of high purity human iPS cell-derived constructs. A, Human cardiomyocytes were generated from the IMR90-iPS cell line at a purity of over 70% by cardiac troponin T (cTnT) flow cytometric analysis. B, The cardiomyocytes displayed robust sarcomeric organization by α-actinin immunostaining (green), as well as nuclear expression of the cardiomyocyte transcription factor Nkx2.5 (red). C, Primitive intercalated disc-like structures containing fascia adherens junctions and desmosomes (arrow) are present in the engineered heart tissue. Nuc: nucleus, Glyc: glycogen. Immunofluorescent staining for cardiac troponin T of iPS cells-derived human bioengineered cardiac tissues under NS, D, and SS, E, and SE, F, conditioning, shows greater alignment in the SS and SE tissue constructs.