Introduction: Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have been used to as a cellular model of cardiac disorders including dilated cardiomyopathy (DCM) demonstrating excellent recapitulation of single cell phenotype. The most common approach to unmasking DCM phenotype at the single cell level is treatment with adrenergic agonists such as norepinephrine (NE). It is unknown if activation of other pathways implicated in DCM, such as rise of late sodium current (INaL) causing sodium/calcium dysregulation, can transform iPSC-CMs towards DCM phenotype and serve as an adequate model to study non-adrenergic signaling pathways in DCM.
Hypothesis: Activation of INaL in iPSC-CMs can unmask DCM phenotype.
Methods: iPSCs from control and DCM patients (TNNT2 R173W) were used for this study. iPSC were differentiated into cardiomyocytes using a chemically defined monolayer protocol. Day 30-40 cells were treated for 7 days with INaL activator, anemone toxin II (ATX II), NE, and a combination of each drug with the INaL blocker ranolazine. Contraction velocities of iPSC-CMs were measured using high resolution microscopy (SI8000 Cell Motion Imaging System). Calcium transients was measured using confocal microscopy. Immunofluorescence staining and gene expression analysis were performed on cells from each drug treatment group.
Results: DCM iPSC-CMs treated with NE and ATX II demonstrate reduction in contraction velocity (Figure), diminished calcium amplitude, and decreased maximum rising rate. These changes correlate with systolic dysfunction, which is associated with DCM phenotype. Treatment with ranolazine ameliorated the NE or ATX II mediated decrease in systolic dysfunction. Additionally, drug treatment with NE and ATX II induced sarcomeric and gene expression changes consistent with DCM phenotype.
Conclusions: iPSC-CMs can recapitulate DCM phenotype via ATX II activation of INaL, providing a disease model for future investigations.