Zeinab Neshati, Department of Biology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Leiden, The Netherlands.
J Appl Physiol (1985). 2020 Mar 1;128(3):545-553. doi: 10.1152/japplphysiol.00420.2019. Epub 2020 Jan 30.
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 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 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 of 306 ± 39 vs. 148 ± 18 ms, APD 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 ( = 82), while the control group showed 4.3% tachyarrhythmias ( = 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. 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.
不同的因素可能触发病变心脏的心律失常，包括纤维化、心肌细胞肥大、缺氧和炎症。这使得确定它们各自对心律失常发生的相对贡献变得困难。因此，在这项研究中，我们使用一种病理性心肌肥厚（PCH）的体外模型来研究其致心律失常特征及其与纤维化或其他 PCH 相关过程无关的潜在机制。用佛波醇 12-肉豆蔻酸 13-醋酸酯（PMA）处理新生大鼠心室肌细胞（nr-vCMC）单层以建立 PCH 的体外模型。在培养的第 3 天，通过光学映射分析 PMA 处理和对照单层的电生理特性。PMA 处理导致细胞大小和总蛋白含量显著增加。它还导致肌浆网/内质网 Ca ATPase 2 水平降低（32%）和利钠肽 A（42%）和α1-骨骼肌肌动蛋白（34%）水平升高，表明 PMA 诱导的肥厚反应确实是病理性的。PMA 处理的单层表现出动作电位持续时间（APD）和 APD 离散度增加，以及传导速度（CV；APD 为 306±39 对 148±18 ms，APD 离散度为 85±19 对 22±7 和 CV 为 10±4 对 21±2 cm/s 在对照中）降低。在局部 1-Hz 刺激下，基于触发活动，53.6%的 PMA 处理培养物显示局灶性心动过速（=82），而对照组显示 4.3%心动过速（=70）。因此，PMA 处理的 nr-vCMC 培养物可能代表一种可很好控制的体外模型，可用于测试针对肥厚相关心律失常特定方面的新治疗干预措施。佛波醇 12-肉豆蔻酸 13-醋酸酯（PMA）处理新生大鼠心室肌细胞（nr-vCMCs）导致许多病理性心肌肥厚（PCH）的显著特征被诱导，包括动作电位持续时间延长和离散度增加，这为早期后除极（EAD）诱导的局灶性心动过速形成提供了足够的时间和去极化力。PMA 处理的 nr-vCMCs 代表一种可很好控制的体外模型，它主要类似于中度左心室肥厚（LVH）而不是严重的 LVH，其中折返的产生是其心律失常的潜在机制。
