Modelling structural and functional heterogeneity in heart failure reveals arrhythmic impact

项目摘要 心脏是一个高度复杂的生物系统。该项目的总体目标是使用多尺度计算 从分子水平到器官水平的心脏建模，以确定结构性的促炎作用。 和功能异质性，并阐明钙（Ca 2+）波的分子和离子机制，延迟 后除极（DAD）、室性早搏（PVC），以及因此的心室颤动（VF）。一 关键成果将是为抗肿瘤药物开发、基因治疗和 新的治疗策略。该项目建立在我们最近的发现1）异质细胞间耦合 在组织尺度上促进触发性心律失常; 2）异质性兰尼碱受体（RyR）分布 在亚细胞尺度上促进促细胞增殖的Ca 2+火花和波动。这里提出的工作旨在 在弥合组织规模心律失常机制和亚细胞规模之间的知识差距， 心律失常机制，利用多尺度计算建模和最先进的实验 测量心脏详细异质性的方法。目标#1是建立RyR属性之间的联系 和亚细胞Ca 2+动力学。为了做到这一点，我们将扩大这项研究，并研究心力衰竭（HF）细胞， 应该是更异质的。我们将测量正常和HF细胞中的RyR分布， 生理和病理模型来检验我们的假设，即异质性RyR分布促进 Ca 2+波，DAD，PVC，以及局灶性心律失常。我们将在目标1中解决的关键问题是：1）如何 RyR簇的大小和RyR在裂隙空间的空间排列方式对Ca ~（2+）火花的影响; 2）RyR簇如何在裂隙空间中形成 在细胞内的分布促进促钙波。RyR门控，因此Ca 2+火花和波， 也受到翻译后修饰（PTMs）的影响。目的#2是检验PTM进一步 增加与结构RyR异质性相互作用的异质性Ca 2+瞬变。SERCA再摄取是 钙循环的另一个关键因素。增加SERCA泵活性增加SR Ca 2+负荷，这促进 波传播与此同时，增加SERCA泵活性会减少细胞质Ca 2+瞬变，这 抑制波的传播。在目标#3中，我们检验了增加SERCA泵功能具有 双相效应对促钙波倾向的影响。当Ca 2+波发生时，它们使细胞脱钙， 膜，并可导致组织中的触发活动。如果细胞耦合良好，去极化将立即发生。 被周围的细胞吸收。然而，当细胞间耦合减少时，去极化不能被抑制。 被周围细胞吸收，PVC更容易发生。然而，与此同时， 耦合使得波的传播更加困难。因此，我们假设存在最佳的细胞间 用于PVC形成的偶联（目标#4）。本工作将建立一个新的范式，即少量不规则Ca ~（2+） 当心脏异质性在HF和其他心脏疾病中增加时，火花可导致整个心脏心律失常。 病理条件。

PROJECT SUMMARY The heart is a highly complex biological system. The overall goal of this project is to use multiscale computational modeling of the heart from the molecular level to the organ level to identify the pro-arrhythmic effects of structural and functional heterogeneity and elucidate molecular and ionic mechanisms of calcium (Ca2+) waves, delayed afterdepolarizations (DADs), premature ventricular contractions (PVCs), and thus ventricular fibrillation (VF). A key outcome will be to provide physiological bases for antiarrhythmic drug development, gene therapies, and novel therapeutic strategies. The project builds on our recent discoveries 1) heterogeneous cell-to-cell coupling promotes triggered arrhythmias at the tissue scale; 2) heterogeneous ryanodine receptor (RyR) distribution promotes arrhythmogenic Ca2+ sparks and waves at the subcellular scale. The work proposed here is aimed at bridging the knowledge gap between the tissue scale arrhythmia mechanisms and the subcellular scale arrhythmia mechanisms utilizing multiscale computational modeling and the state-of-the-art experimental approaches to measure detailed heterogeneity in the heart. Aim #1 is to establish link between RyR properties and subcellular Ca2+ dynamics. To do this, we will extend this study and investigate heart failure (HF) cells, which are supposed to be more heterogeneous. We will measure RyR distributions in normal and HF cells and build the physiological and pathological models to test our hypothesis that heterogeneous RyR distribution promotes Ca2+ waves, DADs, PVCs, and thus focal arrhythmias. Key questions that we will address in Aim #1 are: 1) how RyR cluster size and spatial arrangements of RyRs at the cleft space affect Ca2+ sparks; 2) how RyR cluster distribution in the cell promotes arrhythmogenic Ca2+ waves. RyR gating, and thus Ca2+ sparks and waves, are also influenced by posttranslational modifications (PTMs). Aim #2 is to test the hypothesis that PTMs further increase heterogeneous Ca2+ transients interacting with structural RyR heterogeneity. SERCA reuptake is another key player in the Ca2+ cycling. Increasing SERCA pump activity increases SR Ca2+ load, which promotes wave propagation. At the same time, increasing SERCA pump activity reduces cytosolic Ca2+ transients, which suppresses wave propagation. In Aim #3, we test the hypothesis that increasing SERCA-pump function has a biphasic effect on propensity of arrhythmogenic Ca2+ waves. When Ca2+ waves occur, they depolarize the cell membrane and can lead to triggered activity in tissue. If cells are well-coupled, depolarization will be immediately absorbed by surrounding cells. However, when cell-to-cell coupling is reduced, depolarization cannot be absorbed by surrounding cells and PVCs occur more easily. However, at the same time, reduced cell-to-cell coupling makes wave propagation more difficult. Therefore, we hypothesize that there is an optimal cell-to-cell coupling for PVC formation (Aim #4). The proposed work will establish a new paradigm that a few irregular Ca2+ sparks can lead to the whole heart arrhythmias when cardiac heterogeneity is increased in HF and other pathological conditions.