Impulse initiation in engrafted pluripotent stem cell-derived cardiomyocytes can stimulate the recipient heart.
Transplantation of pluripotent stem cell-derived cardiomyocytes is a novel promising cell-based therapeutic approach for patients with heart failure. However, engraftment arrhythmias are a predictable life-threatening complication and represent a major hurdle for clinical translation. Catheter-based electrophysiological analysis suggested that the ventricular arrhythmias were caused by an automaticity of the transplanted cells, but whether impulse generation by transplanted cardiomyocytes can propagate to the host myocardium and override the recipient rhythm has not been directly assessed experimentally. We used optogenetics to specifically activate engrafted cardiomyocytes, which resulted in impulse generation in the engrafted cardiomyocytes and stimulated the recipient heart (4/9 hearts). Thus, our study shows that transplanted cardiomyocytes can electrically couple to the host myocardium and stimulate the recipient heart, providing experimental evidence that cardiomyocyte automaticity can serve as a trigger for ventricular arrhythmias.