Rigorous Phenotyping of Cardiac iPSC Preparations Requires Knowledge of Their Resting Potential(s).

In a recent “Biophysical Letter” (1), voltage-sensitive dye methods were used to record action potentials from populations of human-induced pluripotent stem-cell-derived cardiac myocytes (iPSC-CMs) that had been maintained in defined cell culture conditions. The main goal of this study was to determine whether chamber-specific (i.e., atrial versus ventricular) action potential waveforms (2) could be identified consistently from these cardiocytes. The data shows that the action potential waveforms depend strongly on cell culture density.