Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland
Cardiovasc Res. 2014 Dec 1;104(3):489-500. doi: 10.1093/cvr/cvu227. Epub 2014 Oct 24.
Myofibroblasts (MFBs) as appearing in the myocardium during fibrotic remodelling induce slow conduction following heterocellular gap junctional coupling with cardiomyocytes (CMCs) in bioengineered tissue preparations kept under isometric conditions. In this study, we investigated the hypothesis that strain as developed during diastolic filling of the heart chambers may modulate MFB-dependent slow conduction.
Effects of defined levels of strain on single-cell electrophysiology (patch clamp) and impulse conduction in patterned growth cell strands (optical mapping) were investigated in neonatal rat ventricular cell cultures (Wistar) grown on flexible substrates. While 10.5% strain only minimally affected conduction times in control CMC strands (+3.2%, n.s.), it caused a significant slowing of conduction in the fibrosis model consisting of CMC strands coated with MFBs (conduction times +26.3%). Increased sensitivity to strain of the fibrosis model was due to activation of mechanosensitive channels (MSCs) in both CMCs and MFBs that aggravated the MFB-dependent baseline depolarization of CMCs. As found in non-strained preparations, baseline depolarization of CMCs was partly due to the presence of constitutively active MSCs in coupled MFBs. Constitutive activity of MSCs was not dependent on the contractile state of MFBs, because neither stimulation (thrombin) nor suppression (blebbistatin) thereof significantly affected conduction velocities in the non-strained fibrosis model.
The findings demonstrate that both constitutive and strain-induced activity of MSCs in MFBs significantly enhance their depolarizing effect on electrotonically coupled CMCs. Ensuing aggravation of slow conduction may contribute to the precipitation of strain-related arrhythmias in fibrotically remodelled hearts.
在纤维化重塑过程中出现在心肌中的肌成纤维细胞（MFB）在生物工程组织准备物中与心肌细胞（CMCs）通过异细胞缝隙连接偶联后会引起缓慢传导，这些组织准备物保持等长条件。在这项研究中，我们假设在心脏腔室舒张充盈过程中产生的应变可能会调节 MFB 依赖性的缓慢传导。
在贴壁生长的新生大鼠心室细胞培养物（Wistar）上，在柔性基底上，使用单细胞电生理学（膜片钳）和图案化生长细胞链（光学映射）来研究应变对单个细胞电生理（膜片钳）和脉冲传导的影响。虽然 10.5%的应变仅使对照 CMC 链的传导时间略有增加（+3.2%，无统计学意义），但在由 CMC 链涂覆 MFB 组成的纤维化模型中，它导致传导显著减慢（传导时间增加 26.3%）。纤维化模型对应变的敏感性增加是由于 CMC 和 MFB 中机械敏感通道（MSCs）的激活加剧了 MFB 依赖性的 CMC 基线去极化。与未受应变的制剂一样，CMC 的基线去极化部分归因于偶联的 MFB 中存在组成性激活的 MSCs。MSCs 的组成性活性不依赖于 MFB 的收缩状态，因为刺激（凝血酶）或抑制（blebbistatin）均不会显著影响非应激纤维化模型中的传导速度。
这些发现表明，MFB 中组成性和应变诱导的 MSCs 活性均显著增强了它们对电偶联 CMC 的去极化作用。随后缓慢传导的恶化可能导致纤维化重塑的心脏中与应变相关的心律失常的发生。
