Figure 13.

ET‐1–ETA axis has a pivotal role in pathological deterioration in HCM iPSC‐derived cardiomyocytes. A, Immunostaining for cardiac troponin‐T (cTnT) of the single cardiomyocytes derived from HCM 1, HCM 2, and HCM 3 iPSC‐derived cardiomyocytes. The single cardiomyocytes at 60 days were cultured for 7 days with ETA‐b and/or ETB‐b in the presence or absence of ET‐1. B, Cell surface areas of 809 to 825 randomly chosen cTnT‐positive cardiomyocytes in each condition were measured (1‐way ANOVA with Steel's multiple comparison post‐test). C, The percentages of cardiomyocytes with myofibrillar disarray were assessed by immunostaining for cTnT of the single cardiomyocytes. N=880 to 995 (per each condition). †P<0.0001 vs ET‐1 condition (χ² test). D, Electron microscopic observation of beating EBs at 60 days cultured with ETA‐b or ETB‐b in the presence of ET‐1. Scale bars, 200 nm. E, Lower magnified electron microscopic images corresponding with (D). F and G, Nuclear translocation of NFATc4 was assessed by immunostaining for NFATc4 and cTnT. The single cardiomyocytes at 60 days were cultured for 7 days with ETA‐b and/or ETB‐b in the presence of ET‐1. Scale bars, 20 μm. N=391 to 751 (per each culture condition). ^†P<0.0001 vs ET‐1 condition (χ² test). EBs indicates embryoid bodies; ET‐1, endothelin‐1; ETA‐b, endothelin receptor type A blocker; ETB‐b, endothelin receptor type B blocker; HCM, hypertrophic cardiomyopathy; iPSC, induced pluripotent stem cell; NFAT, nuclear factor of activated T cells.