AAV-mediated conversion of human pluripotent stem cell-derived pacemaker

Conversion of Unmodified Stem Cells to Pacemaker Cells by Overexpression of Key Developmental Genes

Arrhythmias of the heart are currently treated by implanting electronic pacemakers and defibrillators. Unmodified adipose tissue-derived stem cells (ASCs) have the potential to differentiate into all three germ layers but have not yet been tested for the generation of pacemaker and Purkinje cells. We investigated if-based on overexpression of dominant conduction cell-specific genes in ASCs-biological pacemaker cells could be induced. Here we show that by overexpression of certain genes that are active during the natural development of the conduction system, the differentiation of ASCs to pacemaker and Purkinje-like cells is feasible. Our study revealed that the most effective procedure consisted of short-term upregulation of gene combinations SHOX2-TBX5-HCN2, and to a lesser extent SHOX2-TBX3-HCN2. Single-gene expression protocols were ineffective. Future clinical implantation of such pacemaker and Purkinje cells, derived from unmodified ASCs of the same patient, could open up new horizons for the treatment of arrythmias.

Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes Reveal Bradycardiac Effects Caused by Co-Administration of Sofosbuvir and Amiodarone

Co-administration of sofosbuvir, an anti-hepatitis C virus medication, and antiarrhythmic amiodarone causes symptomatic severe bradycardia in patients and animal models. However, in a few in vitro studies, the combination of sofosbuvir and amiodarone resulted in tachycardiac effects in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). This discrepancy may be attributable to the use of immature hiPSC-CMs in the in vitro studies. To address this, we evaluated the ability of our in-house hiPSC-CMs to assess the interactions between sofosbuvir and amiodarone in vitro. We performed whole-cell patch recordings on hiPSC-CMs to examine the cardiac effect of sofosbuvir and amiodarone, alone or in combination. We found that sofosbuvir and amiodarone caused bradycardiac effects (the beating rate decreased to 75% of the vehicle control, P < 0.001) on our hiPSC-CMs when applied in combination, but they had no significant effect when applied alone. Furthermore, the bradycardiac effect was membrane potential dependent: it increased with depolarization. This raised the possibility that the bradycardiac effects in vivo may originate in nodal cells, which have a more depolarized resting membrane potential compared with ventricular cells. The bradycardiac effects of sofosbuvir plus amiodarone in vitro are consistent with the clinical phenotype and suggest that our hiPSC-CMs may serve as a useful tool in assessing cardiac safety during drug discovery and development process.