John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA.
Department of Physiology, University of Bern, Bern, Switzerland.
J Mol Cell Cardiol. 2024 Jan;186:71-80. doi: 10.1016/j.yjmcc.2023.11.003. Epub 2023 Nov 11.
Gap junction and ion channel remodeling occur early in Arrhythmogenic Cardiomyopathy (ACM), but their pathogenic consequences have not been elucidated. Here, we identified the arrhythmogenic substrate, consisting of propagation slowing and conduction block, in ACM models expressing two different desmosomal gene variants. Neonatal rat ventricular myocytes were transduced to express variants in genes encoding desmosomal proteins plakoglobin or plakophilin-2. Studies were performed in engineered cells and anisotropic tissues to quantify changes in conduction velocity, formation of unidirectional propagation, cell-cell electrical coupling, and ion currents. Conduction velocity decreased by 71% and 63% in the two ACM models. SB216763, an inhibitor of glycogen synthase kinase-3 beta, restored conduction velocity to near normal levels. Compared to control, both ACM models showed greater propensity for unidirectional conduction block, which increased further at greater stimulation frequencies. Cell-cell electrical conductance measured in cell pairs was reduced by 86% and 87% in the two ACM models. Computer modeling showed close correspondence between simulated and experimentally determined changes in conduction velocity. The simulation identified that reduced cell-cell electrical coupling was the dominant factor leading to slow conduction, while the combination of reduced cell-cell electrical coupling, reduced sodium current and inward rectifier potassium current explained the development of unidirectional block. Expression of two different ACM variants markedly reduced cell-cell electrical coupling and conduction velocity, and greatly increased the likelihood of developing unidirectional block - both key features of arrhythmogenesis. This study provides the first quantitative analysis of cellular electrophysiological changes leading to the substrate of reentrant arrhythmias in early stage ACM.
缝隙连接和离子通道重构在心律失常性心肌病 (ACM) 早期发生，但它们的致病后果尚未阐明。在这里，我们鉴定了致心律失常基质，由传播减慢和传导阻滞组成，在表达两种不同桥粒基因变异体的 ACM 模型中。新生大鼠心室肌细胞被转导表达编码桥粒蛋白桥连蛋白或桥粒斑蛋白-2 的基因变异体。在工程细胞和各向异性组织中进行研究，以量化传导速度、单向传播形成、细胞间电耦联和离子电流的变化。在两种 ACM 模型中，传导速度分别降低了 71%和 63%。糖原合酶激酶-3β抑制剂 SB216763 将传导速度恢复到接近正常水平。与对照相比，两种 ACM 模型都表现出更强的单向传导阻滞倾向，在更高的刺激频率下进一步增加。在两种 ACM 模型中，细胞对的细胞间电导率降低了 86%和 87%。计算机模拟表明，模拟和实验确定的传导速度变化之间存在密切对应关系。该模拟确定，细胞间电耦联减少是导致传导缓慢的主要因素，而细胞间电耦联减少、钠电流和内向整流钾电流减少的组合解释了单向阻滞的发展。两种不同的 ACM 变体的表达明显降低了细胞间电耦联和传导速度，并大大增加了单向阻滞的可能性——这都是心律失常发生的关键特征。这项研究提供了对早期 ACM 中折返性心律失常基质导致的细胞电生理变化的首次定量分析。
