心律失常时单个心肌细胞水平的微尺度力学机制研究

Rapid arrhythmias, particularly atrial fibrillation(AF) and ventricular tachycardia/fibrillation (VT/VF) are a major public health concern. Rapid force changes in nonuniform heart muscle may cause cardiac arrhythmias, but until recently no mechanical mechanism studies at single cardiomyocyte level have been performed to confirme the mechanical load leading to cardiac dysfunction and arrhythmias.In this study, we employ our imaging system of AFM combined with fast confocal microscopy to study the in situ characterization of nanomechanical dynamics,cellular membrane potential and calcium signal of living single cardiomyocytes of spontaneously hypertensive rats with chronic mechanical load and culture neonate rat with acute mechanical load. Ca2+ and Na+ signal transduction pathways related to mechanical force are examined by F?rster resonance energy transfer(FRET) technique to investigate the mechanical mechanisms of cardiac arrhythmias at micro scales. In addition, we study the effects of antiarrhythmic drugs such as propafenone, metoprolol, dronedarone and verapamil on the above-mentioned targets of living single cardiomyocyte,in which we explore the mechanical mechanisms of some drugs treating arrhythmias. This would possibly open a door on screening and developing new drugs which have a potential effect for curing cardiac arrhythmias.

以房颤和室速/室颤为代表的快速性心律失常是公众关注的重大健康问题。心脏不一致心肌收缩力的迅速改变可引起心律失常，但目前还缺乏在单个心肌细胞水平上去阐明机械负荷引起心肌功能异常和心律失常的机制。此项研究拟通过我们自行构建的AFM和快速激光共聚焦显微镜联合成像系统，对来自慢性机械负荷的自发性高血压大鼠以及急性机械负荷条件下培养新生大鼠的单个心肌细胞进行细胞微区机械力学、细胞膜膜电位和细胞内Ca2+信号变化的原位联合表征与测定。并采用FRET技术观察机械负荷对细胞内Ca2+、Na+信号通路影响,以探讨心律失常发生的微尺度机械力学机制；除此，观察心肌细胞暴露于临床抗心律失常药普罗帕酮、美托洛尔、决奈达隆、维拉帕米对上述指标的影响,以探讨某些抗心律失常药在治疗快速性心律失常时的可能机械力学机制，并可能为筛选或研发新的抗心律失常药开辟一条新的研究途径。

高血压心肌肥厚时心律失常的发生率增加，但其发生机制还不完全清楚。心脏不一致心肌收缩力的迅速改变可引起心律失常，但目前还缺乏在单个心肌细胞水平上去阐明机械负荷引起心律失常的机制。此项研究采用我们自行构建的原子力显微镜和快速激光共聚焦显微镜联合成像系统，对急性分离的不同周龄（12~25周龄）自发性高血压大鼠与其正常同源常压大鼠的心室肌细胞，在单个心肌细胞水平进行细胞微区力学、细胞膜膜电位和细胞内Ca2+信号变化的原位联合表征与测定。研究发现：（1）高血压发生心肌肥厚时心室肌细胞力学性质发生改变，即杨氏模量变大，细胞刚度增加，并且随着心肌肥厚严重程度逐渐加剧，可导致传导性相伴减小，促进微折返环的形成，可能参与心律失常的发生和维持；（2）高血压致肥厚心室肌细胞机械敏感性较高，使其在有机械刺激存在的情况下细胞内钙离子浓度更易升高，从而促进心律失常的发生；（3）高血压致肥厚心室肌细胞的牵张激活性离子通道数量增多或活性增强，可能参与了高血压致心律失常的发生和维持。