Regular contraction of atrial and ventricular cardiomyocytes differentiated from rat HAP stem cells.

(a-c) Intracellular Ca²⁺ (Fluo-4-AM) imaging of spontaneously beating cardiomyocytes differentiated from HAP stem cells. Lower, calcium transients shown at an expanded timescale taken from the region indicated (•) in the upper. (a) Irregular contractions of non-supplemented cardiomyocytes. (b, c) Representative waveforms of atrial and ventricular cardiomyocytes. (d, e) Dispersion in calcium transient duration of cardiomyocytes differentiated from HAP stem cells. n = 17 for number of standard deviation for non-supplemented cardiomyocytes beats (n = 51 for number of non-supplemented cardiomyocytes beats), n = 25 for number of standard deviation for atrial cardiomyocytes beats (n = 75 for number of atrial cardiomyocytes beats), n = 27 for number of standard deviation for ventricular cardiomyocytes beats (n = 81 for number of ventricular cardiomyocytes beats). Data are presented as mean ± SD. ** P < 0.001, two-sided Mann-Whitney U test. (f, g) Dispersion in calcium transient amplitude of cardiomyocytes differentiated from HAP stem cells. n = 17 for number of standard deviation for non-supplemented cardiomyocytes beats (n = 51 for number of non-supplemented cardiomyocytes beats), n = 25 for number of standard deviation for atrial cardiomyocytes beats (n = 75 for number of atrial cardiomyocytes beats), n = 27 for number of standard deviation for ventricular cardiomyocytes beats (n = 81 for number of ventricular cardiomyocytes beats). Data are presented as mean ± SD. ** P < 0.001, two-sided Welch’s t-test. (h, i) Dispersion in resting calcium concentration of cardiomyocytes differentiated from HAP stem cells. n = 17 for number of standard deviation for non-supplemented cardiomyocytes beats (n = 51 for number of non-supplemented cardiomyocytes beats), n = 27 for number of standard deviation for atrial cardiomyocytes beats (n = 81 for number of atrial cardiomyocytes beats), n = 27 for number of standard deviation for ventricular cardiomyocytes beats (n = 81 for number of ventricular cardiomyocytes beats). Data are presented as mean ± SD. * P < 0.005, two-sided Welch’s t-test.