The Role of Membrane Capacitance in Cardiac Impulse Conduction: An Optogenetic Study With Non-excitable Cells Coupled to Cardiomyocytes
The Role of Membrane Capacitance in Cardiac Impulse Conduction: An Optogenetic Study With Non-excitable Cells Coupled to Cardiomyocytes
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DOI：
10.3389/fphys.2020.00194
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发表时间：
2020-03-26
影响因子：
4
通讯作者：
Rohr, Stephan
中科院分区：
文献类型：
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作者：
De Simone, Stefano Andrea;Moyle, Sarah;Rohr, Stephan
不可兴奋细胞（NECs），如与心肌细胞电张力偶联的心肌成纤维细胞，通过表现电容性负荷（CL：增加的膜被充电）和电阻性负荷（RL：偶联心肌细胞的部分去极化）来影响传导速度（θ）。在这项研究中，我们解开了两种负荷方式对nec依赖性心律失常传导减慢的相对贡献。通过光激活基于盐紫红质的超极化膜电压致动器eNpHR3.0-eYFP（增强黄色荧光蛋白）来可逆地去除RL成分，从而实现CL和RL的区分，eNpHR3.0-eYFP（增强黄色荧光蛋白）在具有通信能力的成纤维细胞样NIH3T3细胞（3T3（HR）细胞）中表达，作为耦合NECs的模型。实验采用以3T3（HR）细胞增加密度包被的新生大鼠心室心肌细胞链。用多电极阵列评估了2.5 Hz刺激下沿制备的脉冲传导。3T3（HR）细胞的相对密度是通过显示eYFP荧光的面积除以心肌细胞覆盖的面积来确定的[覆盖因子（CF）]。与心肌细胞相比，3T3（HR）细胞表现出去极化膜电位（-34 mV），在盐紫质激活过程中转移到-104 mV。在没有光照的情况下，3T3（HR）细胞将θ从330 mm/s（对照心肌细胞链）减慢到100 mm/s （CF = 0.6）。该制备的光照增加了电图振幅，并诱导了在CF > 0.3时θ波的部分恢复。计算机模拟表明，在照明期间观察到的θ亏缺完全归因于耦合3T3（HR）电池所代表的CL， θ与电容呈幂律关系，指数为-0.78（模拟）和-0.99（实验）。CL和RL对传导减慢的相对贡献随CF的变化而变化，在CF 0.5时CL占主导地位。RL不影响CFs时的θ
Non-excitable cells (NECs) such as cardiac myofibroblasts that are electrotonically coupled to cardiomyocytes affect conduction velocity (theta) by representing a capacitive load (CL: increased membrane to be charged) and a resistive load (RL: partial depolarization of coupled cardiomyocytes). In this study, we untangled the relative contributions of both loading modalities to NEC-dependent arrhythmogenic conduction slowing. Discrimination between CL and RL was achieved by reversibly removing the RL component by light activation of the halorhodopsin-based hyperpolarizing membrane voltage actuator eNpHR3.0-eYFP (enhanced yellow fluorescent protein) expressed in communication-competent fibroblast-like NIH3T3 cells (3T3(HR) cells) that served as a model of coupled NECs. Experiments were conducted with strands of neonatal rat ventricular cardiomyocytes coated at increasing densities with 3T3(HR) cells. Impulse conduction along preparations stimulated at 2.5 Hz was assessed with multielectrode arrays. The relative density of 3T3(HR) cells was determined by dividing the area showing eYFP fluorescence by the area covered with cardiomyocytes [coverage factor (CF)]. Compared to cardiomyocytes, 3T3(HR) cells exhibited a depolarized membrane potential (-34 mV) that was shifted to -104 mV during activation of halorhodopsin. Without illumination, 3T3(HR) cells slowed theta along the preparations from similar to 330 mm/s (control cardiomyocyte strands) to similar to 100 mm/s (CF = similar to 0.6). Illumination of the preparation increased the electrogram amplitudes and induced partial recovery of theta at CF > 0.3. Computer simulations demonstrated that the theta deficit observed during illumination was attributable in full to the CL represented by coupled 3T3(HR) cells with theta showing a power-law relationship to capacitance with an exponent of -0.78 (simulations) and -0.99 (experiments). The relative contribution of CL and RL to conduction slowing changed as a function of CF with CL dominating at CF 0.5. The finding that RL did not affect theta at CFs