Developing methods to study tissue mechanics and myofibroblast activation may lead to new targets for therapeutic treatments that are urgently needed for fibrotic disease. Microtissue arrays are a promising approach to conduct relatively high-throughput research into fibrosis as they recapitulate key biomechanical aspects of the disease through a relevant 3D extracellular environment. In early work, our group developed a device called the MVAS-force to stretch microtissues while enabling simultaneous assessment of their dynamic mechanical behavior. Here, we investigated TGF-β1-induced fibroblast to myofibroblast differentiation in microtissue cultures using our MVAS-force device through assessing α-SMA expression, contractility and stiffness. In doing so, we linked cell-level phenotypic changes to functional changes that characterize the clinical manifestation of fibrotic disease. As expected, TGF-β1 treatment promoted a myofibroblastic phenotype and microtissues became stiffer and possessed increased contractility. These changes were partially reversible upon TGF-β1 withdrawal under a static condition, while, in contrast, long-term cyclic stretching maintained myofibroblast activation. This pro-fibrotic effect of mechanical stretching was absent when TGF-β1 receptors were inhibited. Furthermore, stretching promoted myofibroblast differentiation when microtissues were given latent TGF-β1. Altogether, these results suggest that external mechanical stretch may activate latent TGF-β1 and, accordingly, might be a powerful stimulus for continued myofibroblast activation to progress fibrosis. Further exploration of this pathway with our approach may yield new insights into myofibroblast activation and more effective therapeutic treatments for fibrosis.

中文翻译：

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机械拉伸通过潜在的 TGF-β1 激活维持微组织中的肌成纤维细胞表型和功能。

开发研究组织力学和肌成纤维细胞活化的方法可能会为纤维化疾病迫切需要的治疗提供新的靶点。微组织阵列是一种对纤维化进行相对高通量研究的有前途的方法，因为它们通过相关的 3D 细胞外环境概括了疾病的关键生物力学方面。在早期的工作中，我们的团队开发了一种称为 MVAS-force 的设备来拉伸微组织，同时能够同时评估它们的动态机械行为。在这里，我们使用我们的 MVAS 力装置通过评估 α-SMA 表达、收缩性和刚度来研究 TGF-β1 诱导的成纤维细胞向肌成纤维细胞分化。在这样做，我们将细胞水平的表型变化与表征纤维化疾病临床表现的功能变化联系起来。正如预期的那样，TGF-β1 处理促进了肌成纤维细胞表型，并且微组织变得更硬并具有增加的收缩性。这些变化在静态条件下 TGF-β1 退出后部分可逆，而相反，长期循环拉伸维持肌成纤维细胞活化。当 TGF-β1 受体被抑制时，机械拉伸的这种促纤维化作用不存在。此外，当微组织被给予潜伏的 TGF-β1 时，拉伸促进了肌成纤维细胞的分化。总而言之，这些结果表明外部机械拉伸可能激活潜在的 TGF-β1，因此，可能是持续激活肌成纤维细胞以进展纤维化的有力刺激。