Biotechnology Center, Technische Universität Dresden, Dresden, Germany.
Biophys J. 2018 Jan 23;114(2):419-424. doi: 10.1016/j.bpj.2017.11.014.
Tuning of active prestress, e.g., through activity of molecular motors, constitutes a powerful cellular tool to adjust cellular stiffness through nonlinear material properties. Understanding this tool is an important prerequisite for our comprehension of cellular force response, cell shape dynamics, and tissue organization. Experimental data obtained from cell-mechanical measurements often show a simple linear dependence between mechanical prestress and measured differential elastic moduli. Although these experimental findings could point to stress-induced structural changes in the material, we propose a surprisingly simple alternative explanation in a theoretical study. We show how geometrical effects can give rise to increased cellular force response of cells in the presence of active prestress. The associated effective stress-stiffening is disconnected from actual stress-induced changes of the elastic modulus, and should therefore be regarded as an apparent stiffening of the material. We argue that new approaches in experimental design are necessary to separate this apparent stress-stiffening due to geometrical effects from actual nonlinearities of the elastic modulus in prestressed cellular material.
主动预应力的调节，例如通过分子马达的活动，可以通过非线性材料特性来调整细胞的硬度，这是一种强大的细胞工具。理解这个工具是我们理解细胞力响应、细胞形状动力学和组织形成的重要前提。从细胞力学测量中获得的实验数据通常显示机械预应力和测量的差分弹性模量之间存在简单的线性关系。尽管这些实验结果可能指向材料中的应力诱导结构变化，但我们在理论研究中提出了一个令人惊讶的简单替代解释。我们展示了在存在主动预应力的情况下，几何效应如何导致细胞的细胞力响应增加。相关的有效应力硬化与实际的弹性模量的应力诱导变化无关，因此应被视为材料的表观硬化。我们认为，有必要在实验设计中采用新方法，将由于几何效应而导致的这种表观应力硬化与预应力细胞材料中弹性模量的实际非线性分开。
