Department of Medicine and Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Smillow TRC 11-101, Philadelphia, PA, 19104, USA.
Department of Molecular Physiology and Biophysics, University of Vermont's Larner College of Medicine, Burlington, VT, USA.
Basic Res Cardiol. 2022 Aug 25;117(1):41. doi: 10.1007/s00395-022-00952-5.
The mechanical environment of the myocardium has a potent effect on cardiomyocyte form and function, yet an understanding of the cardiomyocyte responses to extracellular stiffening remains incomplete. We therefore employed a cell culture substrate with tunable stiffness to define the cardiomyocyte responses to clinically relevant stiffness increments in the absence of cell-cell interactions. When cultured on substrates magnetically actuated to mimic the stiffness of diseased myocardium, isolated rat adult cardiomyocytes exhibited a time-dependent reduction of sarcomere shortening, characterized by slowed contraction and relaxation velocity, and alterations of the calcium transient. Cardiomyocytes cultured on stiff substrates developed increases in viscoelasticity and microtubule detyrosination in association with early increases in the α-tubulin detyrosinating enzyme vasohibin-2 (Vash2). We found that knockdown of Vash2 was sufficient to preserve contractile performance as well as calcium transient properties in the presence of extracellular substrate stiffening. Orthogonal prevention of detyrosination by overexpression of tubulin tyrosine ligase (TTL) was also able to preserve contractility and calcium homeostasis. These data demonstrate that a pathologic increment of extracellular stiffness induces early, cell-autonomous remodeling of adult cardiomyocytes that is dependent on detyrosination of α-tubulin.
心肌的力学环境对心肌细胞的形态和功能有很强的影响，但人们对心肌细胞对外界基质硬度增加的反应仍了解不足。因此，我们采用了一种可调节硬度的细胞培养基质，在不存在细胞间相互作用的情况下，定义了心肌细胞对临床相关硬度增加的反应。当在模拟病变心肌硬度的磁场激活基质上培养时，分离的成年大鼠心肌细胞表现出时程依赖性的肌节缩短减少，其特征为收缩和舒张速度减慢，以及钙瞬变的改变。在硬基质上培养的心肌细胞表现出粘弹性增加和微管去酪氨酸化，同时早期α-微管去酪氨酸酶血管抑素-2（Vash2）增加。我们发现，在细胞外基质硬度增加的情况下，敲低 Vash2 足以维持收缩性能和钙瞬变特性。通过过表达微管酪氨酸连接酶（TTL）来阻止去酪氨酸化也能够维持收缩性和钙稳态。这些数据表明，细胞外基质硬度的病理性增加会诱导成年心肌细胞的早期、自主重塑，这依赖于α-微管的去酪氨酸化。
