Abstract
Background: Recently, myocardial sheets consisting of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) have been used to clarify the mechanisms of inherited arrhythmias and to evaluate the efficacy of antiarrhythmic drugs. However, whether the electrophysiological properties of the hiPSC-CM are the same as those of the original human cardiomyocytes (hCM) remains unclear. Indeed, hiPSC-CM has automaticity, longer action potential duration (APD), smaller action potential amplitude (APA), and positively shifted diastolic potential (DP). Methods: To clarify this issue, we constructed in silico models of hCM and hiPSC-CM sheets based on the experimental data, and performed simulations of spiral wave (SW) reentry. Then we analyzed the SW behaviors in the in silico myocardial sheets, and also evaluated the effects of IKr blockade. Results: ( 1 )The in silico model of hiPSC-CM had spontaneous activations 0.5-1 Hz, longer APD, smaller APA, and DP positively shifted by∼15 mV. ( 2 )Conduction velocity (CV) in the hiPSC-CM sheet was∼5 cm/s, which was only∼1/10 of the CV in the hCM sheet. ( 3 )Mean cycle length (mCL) of excitations during SW reentry in the hiPSC-CM sheet was∼0.9 Hz, whereas that in the hCM sheet was∼5 Hz and identical to that of human VF. ( 4 )Both CV and mCL during SW reentry in the model of hiPSC-CM sheet were highly consistent with previous experimental data. ( 5 )The mCL of SW reentry in hCM sheet was markedly prolonged by IKr blockade, whereas that in hiPSC-CM sheet was shortened. Conclusion: The SW behavior and the antiarrhythmic drug efficacy in the in silico models of hCM and hiPSC-CM sheets are different. Our findings suggest that such in silico analytical approach might fill the gap between hCM and hiPSC-CM when we apply the hiPSC-CM sheet to clinical practice.
