Recognizing that cells “feel” and respond to their mechanical environment, recent studies demonstrate that many cells exhibit a phenomenon of “mechanical memory” in which features induced by prior mechanical cues persist after the mechanical stimulus has ceased. While there is a general recognition that different cell types exhibit different responses to changes in extracellular matrix stiffening, the phenomenon of mechanical memory within myocardial cell types has received little attention to date. To probe the dynamics of mechanical memory in cardiac fibroblasts (CFs) and cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CMs), we employed a magnetorheological elastomer (MRE) cell culture substrate with tunable and reversible stiffness spanning the range from normal to diseased myocardium. In CFs, using increased cell area and increases in α-smooth muscle actin as markers of cellular responses to matrix stiffening, we found that induction of mechanical memory required seven days of stiff priming. Both induction and maintenance of persistent CF activation were blocked with the F-actin inhibitor cytochalasin D, while inhibitors of microtubule detyrosination had no impact on CFs. In iPSC-CMs, mechanical memory was invoked after only 24 h of stiff priming. Moreover, mechanical memory induction and maintenance were microtubule-dependent in CMs with no dependence on F-actin. Overall, these results identify the distinct temporal dynamics of mechanical memory in CFs and iPSC-CMs with different cytoskeletal mediators responsible for inducing and maintaining the stiffness-activated phenotype. Due to its flexibility, this model is broadly applicable to future studies interrogating mechanotransduction and mechanical memory in the heart and might inform strategies for attenuating the impact of load-induced pathology and excess myocardial stiffness.

最近的研究认识到细胞“感觉”并对其机械环境做出反应，表明许多细胞表现出一种“机械记忆”现象，即在机械刺激停止后，先前的机械线索诱导的特征仍然存在。虽然人们普遍认识到不同的细胞类型对细胞外基质硬化的变化表现出不同的反应，但迄今为止，心肌细胞类型内的机械记忆现象很少受到关注。为了探究源自人诱导多能干细胞 (iPSC-CM) 的心脏成纤维细胞 (CF) 和心肌细胞 (iPSC-CM) 的机械记忆动态，我们采用了磁流变弹性体 (MRE) 细胞培养基质，其刚度可调节且可逆，范围从正常到患病的心肌。在 CF 中，使用增加的细胞面积和 α-平滑肌肌动蛋白的增加作为细胞对基质硬化反应的标记，我们发现机械记忆的诱导需要 7 天的僵硬启动。 F-肌动蛋白抑制剂细胞松弛素 D 可以阻断持续 CF 激活的诱导和维持，而微管去酪氨酸抑制剂对 CF 没有影响。在 iPSC-CM 中，机械记忆在严格启动仅 24 小时后就被激活。此外，CM 中机械记忆的诱导和维持依赖于微管，而不依赖于 F-肌动蛋白。总体而言，这些结果确定了 CF 和 iPSC-CM 中机械记忆的不同时间动态，以及负责诱导和维持刚度激活表型的不同细胞骨架介质。由于其灵活性，该模型广泛适用于未来研究心脏中的机械转导和机械记忆，并可能为减轻负荷引起的病理和过度心肌僵硬度的影响提供策略。