Controlling mesenchymal stem cell (MSC) differentiation remains a critical challenge in MSCs’ therapeutic application. Numerous biophysical and mechanical stimuli influence stem cell fate; however, their relative efficacy and specificity in mechanically directed differentiation remain unclear. Yes-associated protein (YAP) is one key mechanosensitive protein that controls MSC differentiation. Previous studies have related nuclear mechanics with YAP activity, but we still lack an understanding of what nuclear deformation specifically regulates YAP and its relationship with mechanical stimuli. Here, we report that maximum nuclear curvature is the most precise biophysical determinant for YAP mechanotransduction-mediated MSC differentiation and is a relevant parameter for stem cell-based therapies. We employed traction force microscopy and confocal microscopy to characterize the causal relationships between contractility and nuclear deformation in regulating YAP activity in MSCs. We observed that an increase in contractility compresses nuclei anisotropically, whereby the degree of asymmetric compression increased the bending curvature of the nuclear membrane. We then examined membrane curvature and tension using thin micropatterned adhesive substrate lines and an FRET-based tension sensor, revealing the direct role of curvature in YAP activity driven by both active and passive nuclear import. Finally, we employed micropatterned lines to control nuclear curvature and precisely direct MSC differentiation. This work illustrates that nuclear curvature subsumes other biophysical aspects to control YAP-mediated differentiation in MSCs and may provide a deterministic solution to some of the challenges in mesenchymal stem cell therapies.

中文翻译：

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核曲率决定间充质干细胞Yes相关蛋白的定位和分化

控制间充质干细胞（MSC）分化仍然是间充质干细胞治疗应用中的一个关键挑战。许多生物物理和机械刺激影响干细胞的命运；然而，它们在机械定向分化中的相对功效和特异性仍不清楚。 Yes相关蛋白（YAP）是控制MSC分化的一种关键的机械敏感蛋白。先前的研究已将核力学与 YAP 活性联系起来，但我们仍然缺乏对核变形具体调节 YAP 及其与机械刺激的关系的了解。在这里，我们报告最大核曲率是 YAP 机械转导介导的 MSC 分化的最精确的生物物理决定因素，并且是基于干细胞的治疗的相关参数。我们采用牵引力显微镜和共焦显微镜来表征收缩性和核变形在调节 MSC 中 YAP 活性方面​​的因果关系。我们观察到收缩性的增加会各向异性地压缩核，从而不对称压缩的程度增加了核膜的弯曲曲率。然后，我们使用薄的微图案粘合基底线和基于 FRET 的张力传感器检查了膜曲率和张力，揭示了曲率在主动和被动核输入驱动的 YAP 活性中的直接作用。最后，我们采用微图案线来控制核曲率并精确指导 MSC 分化。这项工作说明核曲率包含其他生物物理方面来控制 YAP 介导的 MSC 分化，并可能为间充质干细胞治疗中的一些挑战提供确定性的解决方案。