*2.7. Measurement of Cardiomyocyte Size*

The size of iPSC-derived cardiomyocytes was evaluated by measuring the cell area. Twenty days after cardiac induction, the spontaneously beating embryoid bodies were dissociated into single cells using Accutase™ (STEMCELL Technologies). These cells were then plated onto gelatin-coated dishes for further experiments and analysis. Subsequently, the cellular images of cTnT-positive cells were recorded at days 30, 40 and 60 post-induction of differentiation using FV10i confocal microscope (Olympus, Tokyo, Japan). The pixel area of cTnT-positive cells was measured and analyzed using ImageJ software package (NIH). About total two hundred cells were analyzed in five independent experiments.
