Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NWO - ZonMw (VIDI grant 016.176.340 to JL) Dutch Heart Foundation (ERA-CVD JTC2018 grant 2018T094; Dr. Dekker Program grant 2015T082 to JL) The Netherlands Cardio Vascular Research Initiative (CVON): the Dutch Heart Foundation, Dutch Federation of University Medical Center, the Netherlands Organization for Health Research and Development and the Royal Netherlands Academy of Sciences (CVON-eDETECT 2015-12 and CVON-PREDICT2 2018-30 to TvV). Background Patients with arrhythmogenic cardiomyopathy (ACM), an inherited progressive cardiac disease, mostly remain asymptomatic until the occurrence of life-threatening arrhythmias. Previous research identified disturbed calcium handling as a potential disease-initiating mechanism [1], but how this translates to arrhythmogenesis and cardiac mechanical dysfunction remains unknown. Purpose To characterize disturbed molecular regulators of intracellular calcium (Ca2+) handling in patients with ACM and predict their effects on action potential (AP), calcium transient (CaT) and tension development in both left and right ventricles (LV, RV) using a computer model of cellular electromechanics. Methods We performed gene expression (qPCR) and protein level (Western blot) analysis using LV and RV tissue samples obtained from 5 ACM patients who underwent heart transplant and 5 controls with no history of cardiac disease. Changes in protein levels were implemented in our recent human electromechanical cardiomyocyte computer model [2]. CaT, AP and tension traces were simulated and compared to control. Clinical data (age, sex, genetics, ECG, echocardiography) were related to the simulation outcome. Results Measured protein levels varied significantly between the 5 patients and between individual LV and RV samples. Exemplary results for one ACM patient are shown in the figure below. In the LV, AP duration was shorter than control (221ms vs. 255ms), CaT peak was increased (0.52µM vs. 0.39µM) but CaT amplitude was reduced due to increased diastolic Ca2+ (0.26µM vs. 0.060µM). Relaxation was also impaired, as shown by a longer CaT and tension duration (965ms vs. 640ms), and an increased diastolic tension (10mN vs. 4.8mN). In the RV, AP duration was shortened, and CaT and tension peak were lower than in the LV (0.37µM and 13.6mN). Diastolic levels were elevated compared to control, and CaT and tension development were prolonged. This can be related to the measured Ca2+ changes: in the LV, a lower activity of the sodium-calcium exchanger (NCX) (22% of control) and SERCA pump (52%) combined with an increased ryanodine receptor (RyR) activity (96%) may impair the extrusion of Ca2+, leading to accumulation of Ca2+ and increased diastolic Ca2+ levels. In the RV, milder changes in NCX (48% of control) and RyR (11%) may explain the larger Ca2+ extrusion, leading to lower CaT peak and diastolic levels. The patient showed a normal LV size, a severely dilated RV, as well as a poor LV fractional shortening suggesting increased ventricular stiffness, in line with the potential impaired relaxation shown by the simulations. Conclusion By integrating protein level data from ACM patients into a computational model of cellular electromechanics, we quantified the electromechanical effects of patient-specific Ca2+ handling changes. Future whole-heart extensions of this work have the potential to identify and understand proarrhythmic mechanisms in ACM patients.

中文翻译：

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计算模型确定了心律失常性心肌病患者细胞内钙处理中断的细胞机电效应

资金致谢 资金来源类型：公共拨款——仅限国家预算。主要资金来源：NWO - ZonMw（VIDI 赠款 016.176.340 至 JL）荷兰心脏基金会（ERA-CVD JTC2018 赠款 2018T094；Dekker 博士计划赠款 2015T082 至 JL）荷兰心脏血管研究计划 (CVON)：荷兰心脏基金会、荷兰大学医学中心联合会、荷兰卫生研究与发展组织和荷兰皇家科学院（CVON-eDETECT 2015-12 和 CVON-PREDICT2 2018-30 转至 TVV）。背景 致心律失常性心肌病 (ACM) 是一种遗传性进行性心脏病，在发生危及生命的心律失常之前，大多数患者都没有症状。先前的研究确定干扰钙处理是一种潜在的疾病引发机制 [1]，但这如何转化为心律失常和心脏机械功能障碍仍然未知。目的 描述 ACM 患者细胞内钙 (Ca2+) 处理的受干扰分子调节因子，并使用计算机预测它们对左右心室 (LV、RV) 动作电位 (AP)、钙瞬变 (CaT) 和张力发展的影响细胞机电模型。方法 我们使用从 5 名接受心脏移植的 ACM 患者和 5 名无心脏病史的对照获得的 LV 和 RV 组织样本进行基因表达 (qPCR) 和蛋白质水平 (Western blot) 分析。在我们最近的人体机电心肌细胞计算机模型中实现了蛋白质水平的变化 [2]。模拟猫、AP 和张力轨迹并与对照进行比较。临床数据（年龄、性别、遗传学、心电图、超声心动图）与模拟结果有关。结果 5 名患者之间以及单个 LV 和 RV 样本之间测量的蛋白质水平显着不同。下图显示了一名 ACM 患者的示例性结果。在 LV，AP 持续时间比对照组短（221ms 对 255ms），CaT 峰值增加（0.52μM 对 0.39μM），但由于舒张期 Ca2+ 增加，CaT 幅度降低（0.26μM 对 0.060μM）。放松也受到损害，如更长的 Cat 和张力持续时间（965 毫秒对 640 毫秒）和舒张压增加（10 百万对 4.8 百万）所示。在 RV 中，AP 持续时间缩短，CaT 和张力峰值低于 LV（0.37µM 和 13.6mN）。与对照组相比，舒张压水平升高，CaT 和张力发展延长。这可能与测量的 Ca2+ 变化有关：在 LV 中，钠-钙交换剂 (NCX) (对照的 22%) 和 SERCA 泵 (52%) 的活性较低以及兰尼碱受体 (RyR) 活性的增加 (96%) 可能会损害 Ca2+ 的排出，导致Ca2+ 和舒张期 Ca2+ 水平升高。在 RV 中，NCX（对照组的 48%）和 RyR（11%）的较温和变化可以解释较大的 Ca2+ 挤出，导致较低的 CaT 峰值和舒张水平。患者显示出正常的 LV 大小、严重扩张的 RV 以及不良的 LV 缩短分数，表明心室僵硬增加，这与模拟显示的潜在松弛受损一致。结论通过将 ACM 患者的蛋白质水平数据整合到细胞机电计算模型中，我们量化了患者特定 Ca2+ 处理变化的机电效应。