Figure 5

Differentiation of iPSK3 cells into cardiac cells. A) Immunocytochemistry revealed that clusters of contracting cells expressed cardiac markers including GATA4 in the cells nuclei, detected by DAPI staining, and cardiac-specific Troponin T. High-resolution images revealed a striated pattern of Troponin T staining as expected for a protein associated with myofibrils (Scale bar = 100 μm). B) Intracellular calcium concentration measurements using the fluo-4 AM fluorescent indicator identified rhythmic oscillation correlating with cardiac cell contraction (0.7s between each picture; see movie S2 in supplemental data). C) Contracting cells within the cluster exhibit both an atrial-like calcium transient (cell 1 and 2, lower left panel) and a ventricular-like calcium transient (cell 3 and 4, lower right panel).