Key result
PMA treatment induces focal tachyarrhythmias in ~54% of cultured rat cardiomyocytes, modeling hypertrophy-associated arrhythmias.
Why the study?
Multiple factors trigger arrhythmias in diseased hearts, making it difficult to establish the relative contribution of cardiomyocyte hypertrophy independent of fibrosis or other processes.
PMA treatment of neonatal rat ventricular cardiomyocytes creates a reliable in vitro model of pathological cardiac hypertrophy with distinct proarrhythmic features driven by early afterdepolarizations.
Answers are grounded in this paper and cite their sources.
Provides in vitro model for hypertrophy-linked arrhythmias; hypothesis-generating with translation to human disease unproven.
Different factors may trigger arrhythmias in diseased hearts, including fibrosis, cardiomyocyte hypertrophy, hypoxia, and inflammation. This makes it difficult to establish the relative contribution of each of them to the occurrence of arrhythmias. Accordingly, in this study, we used an in vitro model of pathological cardiac hypertrophy (PCH) to investigate its proarrhythmic features and the underlying mechanisms independent of fibrosis or other PCH-related processes. Neonatal rat ventricular cardiomyocyte (nr-vCMC) monolayers were treated with phorbol 12-myristate 13-acetate (PMA) to create an in vitro model of PCH. The electrophysiological properties of PMA-treated and control monolayers were analyzed by optical mapping at day 9 of culture. PMA treatment led to a significant increase in cell size and total protein content. It also caused a reduction in sarcoplasmic/endoplasmic reticulum Ca 2+ ATPase 2 level (32%) and an increase in natriuretic peptide A (42%) and α1-skeletal muscle actin (34%) levels, indicating that the hypertrophic response induced by PMA was, indeed, pathological in nature. PMA-treated monolayers showed increases in action potential duration (APD) and APD dispersion, and a decrease in conduction velocity (CV; APD 30 of 306 ± 39 vs. 148 ± 18 ms, APD 30 dispersion of 85 ± 19 vs. 22 ± 7 and CV of 10 ± 4 vs. 21 ± 2 cm/s in controls). Upon local 1-Hz stimulation, 53.6% of the PMA-treated cultures showed focal tachyarrhythmias based on triggered activity ( n = 82), while the control group showed 4.3% tachyarrhythmias ( n = 70). PMA-treated nr-vCMC cultures may, thus, represent a well-controllable in vitro model for testing new therapeutic interventions targeting specific aspects of hypertrophy-associated arrhythmias. NEW & NOTEWORTHY Phorbol 12-myristate 13-acetate (PMA) treatment of neonatal rat ventricular cardiomyocytes (nr-vCMCs) led to induction of many significant features of pathological cardiac hypertrophy (PCH), including action potential duration prolongation and dispersion, which provided enough time and depolarizing force for formation of early afterdepolarization (EAD)-induced focal tachyarrhythmias. PMA-treated nr-vCMCs represent a well-controllable in vitro model, which mostly resembles to moderate left ventricular hypertrophy (LVH) rather than severe LVH, in which generation of a reentry is the putative mechanism of its arrhythmias.
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Neshati et al. (2020) studied Pathological cardiac hypertrophy (in vitro model) (n=152). Phorbol 12-myristate 13-acetate (PMA) vs. Control monolayers was evaluated on Focal tachyarrhythmias based on triggered activity upon local 1-Hz stimulation. PMA treatment of neonatal rat ventricular cardiomyocytes induced focal tachyarrhythmias in 53.6% of cultures compared to 4.3% in controls, providing an in vitro model for hypertrophy-associated arrhythmias.
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