Fig. 2

A Immunostaining images of NKX2.5 and TNNT2 in differentiated cells treated by IWP-2 or nicotinamide (Nam) at day 30 of differentiation. Scale bar, 50 μm. B Representative flow cytometric analyses showing the proportion of TNNT2 at day 30 of differentiation. Gray line indicates the level of isotype control. Data are representative of three independent experiments. C Representative confocal microscopy images of α-Actinin and DAPI in the cardiomyocytes derived by IWP-2 3 μM or nicotinamide 20 mM after 25 days of differentiation. Scale bar, 10 μm. D Quantification of sarcomere length using LAS X software. (Data shown are mean ± SD, n = 38−40 cells, *p < 0.05 compared with IWP-2 group). E Heatmap showing the gene expression profiles of cardiomyocytes induced by IWP-2 or nicotinamide (Nam) at day 25. The differentiated cells were harvested at day 25, and the relative expression level of genes was analyzed by qPCR. Results shown are average of three independent experiments, and represent log10 of gene expression levels relative to TBP. F Representative recordings of active potential in nicotinamide or IWP-2-derived cardiomyocytes. G Action potential (AP) duration 50%, 90% (APD50, APD90), and frequency were analyzed. (Data shown are mean ± SD, n = 24−26 cells, *p < 0.05 compared with IWP-2 group). H Oxygen consumption rate (OCR) of IWP-2 or nicotinamide-induced cardiomyocytes was measured using Mito Stress Test. I Basal respiration, maximal respiration, ATP production, and spare respiratory capacity of cardiomyocytes were calculated. (Data shown are mean ± SD, n = 3−4, *p < 0.05 compared with IWP-2 group).