Reentrant Activity in Cultured Cardiac Cell Monolayers

描述(申请人提供)：折返机制在许多类型的心律失常中起主要作用。功能性折返，以螺旋波的形式，是许多心动过速和纤颤的基础，但螺旋波的稳定性和解体的动力学特性仍然没有得到很好的描述。我们实验室以前的工作已经证明，在培养的新生大鼠心室细胞单层中可以诱导并系统地研究持续的螺旋波活动。这项工作的重点将放在螺旋波的特性上，特别是它们如何受到组织异质性孤岛的影响，这些异质性包括离子通道表达的改变、缝隙连接耦合和异位焦点。将利用组织工程方法对特定位置的不同类型的异质性进行系统评估。我们建议使用电压和钙敏感的染料和多点光学映射来跟踪心肌细胞单层中的折返活动。我们将检验这些假设，(1)细胞膜性质的区域差异可以锚定折返波并改变周期长度，(2)组织微观结构的异质性导致不连续的传播并放大解剖障碍的锚定效应，(3)再入过程中的块状线源于微观异质性，其长度受兴奋性、波长和组织各向异性的调节，(4)离子通道表达改变的孤岛可能足以引发螺旋波破裂，特别是在细胞-细胞耦合减少的情况下，以及(5)触发的活动和后去极化可以导致螺旋波破裂，但需要临界质量和临界耦合。这些目的是利用培养的细胞单层的特性作为一种控制良好的、通用的和定量的实验模型，用于临床上重要的、基于折返的心律失常的基础研究。

DESCRIPTION (provided by applicant): Reentrant mechanisms play a primary role in many types of cardiac arrhythmias. Functional reentry, in the form of spiral waves, underlies many tachycardias as well as fibrillation, but the dynamic properties of spiral wave stability and breakup are still not well characterized. Previous work from our lab has demonstrated that sustained spiral wave activity can be induced and systematically studied in monolayers of cultured neonatal rat ventricular cells. The focus of this work will be on the properties of spiral waves, and particularly how they are influenced by islands of tissue heterogeneities that include altered ion channel expression, gap junctional coupling, and ectopic foci. Tissue engineering approaches will be utilized to permit a systematic evaluation of different types of heterogeneities at specified locations. We propose to use voltage- and calcium-sensitive dyes and multi-site optical mapping to track the reentrant activity in cardiac cell monolayers. We will test the hypotheses, (1) Regional differences in cellular membrane properties can anchor reentrant waves and alter cycle length, (2) Heterogeneities in tissue microstructure result in discontinuous propagation and amplify the anchoring effects of anatomical obstacles, (3) Lines of block during reentry originate from microheterogeneities, and their length is modulated by excitability, wavelength and tissue anisotropy, (4) Islands of altered ion channel expression may suffice to initiate spiral wave breakup, particularly under conditions of reduced cell-cell coupling, and (5) Triggered activity and afterdepolarizations can cause spiral wave breakup but require critical mass and critical coupling. These aims exploit the properties of the cultured cell monolayer as a well-controlled, versatile and quantitative experimental model for basic studies of clinically important, reentry-based arrhythmias.