National Heart and Lung Institute, Imperial College London, UK.
Department of Cell and Molecular Physiology, Loyola University Chicago, USA.
J Mol Cell Cardiol. 2020 Apr;141:11-16. doi: 10.1016/j.yjmcc.2020.03.007. Epub 2020 Mar 19.
Determining transmural mechanical properties in the heart provides a foundation to understand physiological and pathophysiological cardiac mechanics. Although work on mechanical characterisation has begun in isolated cells and permeabilised samples, the mechanical profile of living individual cardiac layers has not been examined. Myocardial slices are 300 μm-thin sections of heart tissue with preserved cellular stoichiometry, extracellular matrix, and structural architecture. This allows for cardiac mechanics assays in the context of an intact in vitro organotypic preparation. In slices obtained from the subendocardium, midmyocardium and subepicardium of rats, a distinct pattern in transmural contractility is found that is different from that observed in other models. Slices from the epicardium and midmyocardium had a higher active tension and passive tension than the endocardium upon stretch. Differences in total myocyte area coverage, and aspect ratio between layers underlined the functional readouts, while no differences were found in total sarcomeric protein and phosphoprotein between layers. Such intrinsic heterogeneity may orchestrate the normal pumping of the heart in the presence of transmural strain and sarcomere length gradients in the in vivo heart.
确定心脏的透壁力学特性为理解生理和病理生理心脏力学提供了基础。尽管在分离细胞和通透样本中已经开始进行力学特性研究，但尚未检查活的个体心脏层的力学特征。心肌切片是厚度为 300μm 的心脏组织切片，具有保留的细胞化学计量、细胞外基质和结构架构。这允许在完整的体外器官型制剂中进行心脏力学测定。在从大鼠的心内膜下、心肌中层和心外膜获得的切片中，发现了一种与其他模型观察到的不同的透壁收缩性的明显模式。在拉伸时，心外膜和心肌中层的切片的主动张力和被动张力均高于心内膜。层间的总心肌细胞面积覆盖率和纵横比的差异突出了功能读数，而层间的总肌节蛋白和磷酸蛋白没有差异。这种内在异质性可能在体内心脏存在透壁应变和肌节长度梯度的情况下协调心脏的正常泵血。
