Turku Bioscience Centre, University of Turku and Åbo Akademi University, Turku FI-20520, Finland.
Misvik Biology Oy, Turku FI-20520, Finland.
Proc Natl Acad Sci U S A. 2023 Oct 24;120(43):e2304288120. doi: 10.1073/pnas.2304288120. Epub 2023 Oct 16.
Integrin-dependent adhesion to the extracellular matrix (ECM) mediates mechanosensing and signaling in response to altered microenvironmental conditions. In order to provide tissue- and organ-specific cues, the ECM is composed of many different proteins that temper the mechanical properties and provide the necessary structural diversity. Despite most human tissues being soft, the prevailing view from predominantly in vitro studies is that increased stiffness triggers effective cell spreading and activation of mechanosensitive signaling pathways. To address the functional coupling of ECM composition and matrix rigidity on compliant substrates, we developed a matrix spot array system to screen cell phenotypes against different ECM mixtures on defined substrate stiffnesses at high resolution. We applied this system to both cancer and normal cells and surprisingly identified ECM mixtures that support stiffness-insensitive cell spreading on soft substrates. Employing the motor-clutch model to simulate cell adhesion on biochemically distinct soft substrates, with varying numbers of available ECM-integrin-cytoskeleton (clutch) connections, we identified conditions in which spreading would be supported on soft matrices. Combining simulations and experiments, we show that cell spreading on soft is supported by increased clutch engagement on specific ECM mixtures and even augmented by the partial inhibition of actomyosin contractility. Thus, "stiff-like" spreading on soft is determined by a balance of a cell's contractile and adhesive machinery. This provides a fundamental perspective for in vitro mechanobiology studies, identifying a mechanism through which cells spread, function, and signal effectively on soft substrates.
整合素依赖性细胞黏附到细胞外基质（ECM）介导的机械感受和信号转导，以响应改变的微环境条件。为了提供组织和器官特异性的线索，细胞外基质由许多不同的蛋白质组成，这些蛋白质可以调节机械性能并提供必要的结构多样性。尽管大多数人体组织是柔软的，但主要来自于体外研究的普遍观点是，增加刚度可以触发有效的细胞铺展和机械敏感信号通路的激活。为了解决细胞外基质组成和基质刚度在顺应性基底上的功能耦合，我们开发了一种基质斑点阵列系统，以在高分辨率下针对不同的细胞外基质混合物筛选不同基底刚度的细胞表型。我们将该系统应用于癌症细胞和正常细胞，令人惊讶的是，我们确定了支持在软基底上刚度不敏感细胞铺展的细胞外基质混合物。采用马达离合器模型模拟在生化性质不同的软基底上的细胞黏附，随着可用的细胞外基质-整合素-细胞骨架（离合器）连接数量的变化，我们确定了在软基质上支持铺展的条件。通过模拟和实验相结合，我们表明，在特定的细胞外基质混合物上增加离合器结合可以支持细胞在软基质上的铺展，甚至可以通过部分抑制肌动球蛋白收缩性来增强。因此，软基质上的“刚性样”铺展是由细胞的收缩和黏附机制的平衡决定的。这为体外力学生物学研究提供了一个基本的视角，确定了一种机制，通过该机制，细胞可以有效地在软基底上铺展、功能和信号转导。
