Cellular response to the topography of their environment, known as contact guidance, is a crucial aspect to many biological processes yet remains poorly understood. A prevailing model to describe cellular contact guidance involves the lateral confinement of focal adhesions (FA) by topography as an underlying mechanism governing how cells can respond to topographical cues. However, it is not clear how this model is consistent with the well-documented depth-dependent contact guidance responses in the literature. To investigate this model, we fabricated a set of contact guidance chips with lateral dimensions capable of confining focal adhesions and relaxing that confinement at various depths. We find at the shallowest depth of 330 nm, the model of focal adhesion confinement is consistent with our observations. However, the cellular response at depths of 725 and 1000 nm is inadequately explained by this model. Instead, we observe a distinct reorganization of F-actin at greater depths in which topographically induced cell membrane deformation alters the structure of the cytoskeleton. These results are consistent with an alternative curvature-hypothesis to explain cellular response to topographical cues. Together, these results indicate a confluence of two molecular mechanisms operating at increased induced membrane curvature that govern how cells sense and respond to topography.

中文翻译：

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地形深度揭示了与粘着斑限制不同的接触引导机制

细胞对其环境地形的反应（称为接触引导）是许多生物过程的一个重要方面，但人们仍然知之甚少。描述细胞接触引导的流行模型涉及地形对粘着斑（FA）的横向限制，作为控制细胞如何响应地形提示的基本机制。然而，尚不清楚该模型如何与文献中记录充分的深度依赖接触指导响应相一致。为了研究这个模型，我们制造了一组具有横向尺寸的接触引导芯片，能够限制粘着斑并在不同深度放松这种限制。我们发现在最浅深度 330 nm 处，粘着斑限制模型与我们的观察结果一致。然而，该模型无法充分解释 725 和 1000 nm 深度的细胞反应。相反，我们观察到 F-肌动蛋白在更深处发生了明显的重组，其中地形诱导的细胞膜变形改变了细胞骨架的结构。这些结果与解释细胞对地形线索的反应的替代曲率假设一致。总之，这些结果表明，两种分子机制在诱导膜曲率增加的情况下发挥作用，从而控制细胞如何感知和响应地形。