Fig. 4
Mesoderm prepotentiation imparts calcium handling resilience. (A) Fluo-4 staining of iPS cardiomyocytes at 15 d of differentiation allowed assessment of calcium handing. (B) Cells were paced with an external field stimulation of 0.5 Hz to 2 Hz. T primed cells were able to maintain calcium transient morphology with up to 2 Hz external field stimulation whereas untransfected cells exhibited compromised calcium handling (B inset). (C) T transfected cells were able to appropriately shorten transient width70, reflecting the time needed to reach a 70% return to baseline, with increasing external field stimulation rate. Mesoderm induction before differentiation promoted greater calcium handling as shown by increased transient amplitudes (D) and transient area (E). T transfected cells exhibited faster kinetics as shown by a greater maximum upstroke velocity (F) and lower decay constant, tau (G). T + CHIR denotes cells transfected with T that undergo biphasic Wnt modulation for cardiac differentiation. CHIR denotes untransfected cells that are differentiated with Wnt modulation. *p < 0.05, **p < 0.01, ***p < 0.001, ## no CHIR cells were able to maintain transient morphology with 2 Hz external field stimulation.
