Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD, USA.
Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, USA.
J Mol Cell Cardiol. 2014 Mar;68:29-37. doi: 10.1016/j.yjmcc.2013.12.025. Epub 2014 Jan 9.
The electrophysiological consequences of cardiomyocyte and myofibroblast interactions remain unclear, and the contribution of mechanical coupling between these two cell types is still poorly understood. In this study, we examined the time course and mechanisms by which addition of myofibroblasts activated by transforming growth factor-beta (TGF-β) influence the conduction velocity (CV) of neonatal rat ventricular cell monolayers. We observed that myofibroblasts affected CV within 30 min of contact and that these effects were temporally correlated with membrane deformation of cardiomyocytes by the myofibroblasts. Expression of dominant negative RhoA in the myofibroblasts impaired both myofibroblast contraction and myofibroblast-induced slowing of cardiac conduction, whereas overexpression of constitutive RhoA had little effect. To determine the importance of mechanical coupling between these cell types, we examined the expression of the two primary cadherins in the heart (N- and OB-cadherin) at cell-cell contacts formed between myofibroblasts and cardiomyocytes. Although OB-cadherin was frequently found at myofibroblast-myofibroblast contacts, very little expression was observed at myofibroblast-cardiomyocyte contacts. The myofibroblast-induced slowing of cardiac conduction was not prevented by silencing of OB-cadherin in the myofibroblasts, and could be reversed by inhibitors of mechanosensitive channels (gadolinium or streptomycin) and cellular contraction (blebbistatin). In contrast, N-cadherin expression was commonly observed at myofibroblast-cardiomyocyte contacts, and silencing of N-cadherin in myofibroblasts prevented the myofibroblast-dependent slowing of cardiac conduction. We propose that myofibroblasts can impair the electrophysiological function of cardiac tissue through the application of contractile force to the cardiomyocyte membrane via N-cadherin junctions.
心肌细胞和成纤维细胞相互作用的电生理后果尚不清楚,这两种细胞类型之间的机械偶联的贡献仍知之甚少。在这项研究中,我们研究了转化生长因子-β(TGF-β)激活的成纤维细胞与心肌细胞接触后影响新生大鼠心室细胞单层传导速度(CV)的时程和机制。我们观察到成纤维细胞在与心肌细胞接触 30 分钟内影响 CV,这些影响与成纤维细胞对心肌细胞膜的变形在时间上相关。成纤维细胞中显性负性 RhoA 的表达损害了成纤维细胞的收缩和成纤维细胞诱导的心脏传导减慢,而组成型 RhoA 的过表达几乎没有影响。为了确定这两种细胞类型之间机械偶联的重要性,我们在成纤维细胞与心肌细胞之间形成的细胞-细胞接触处检查了心脏中两种主要钙粘蛋白(N-和 OB-钙粘蛋白)的表达。尽管 OB-钙粘蛋白经常在成纤维细胞-成纤维细胞接触处发现,但在成纤维细胞-心肌细胞接触处很少表达。在成纤维细胞中沉默 OB-钙粘蛋白并不能阻止成纤维细胞诱导的心脏传导减慢,而机械敏感通道(钆或链霉素)和细胞收缩(blebbistatin)抑制剂可逆转该作用。相比之下,N-钙粘蛋白表达通常在成纤维细胞-心肌细胞接触处观察到,在成纤维细胞中沉默 N-钙粘蛋白可防止成纤维细胞依赖性心脏传导减慢。我们提出,成纤维细胞可以通过 N-钙粘蛋白连接将收缩力施加到心肌细胞膜上来损害心肌组织的电生理功能。