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Abstract: Networks of actin filaments and bundles are ubiquitous in cellular cytoskeletons, but the elasticity of the network is not well understood. In this paper, a computational model based on form-finding analysis is proposed to investigate the stiffness of cytoskeleton networks consisting of actin filaments and bundles. The model shows that networks with parallel bundles aligned in the stretching direction are stiffer than those with randomly distributed bundles. The results provide a mechanical explanation for the experimental observation that cells primarily create parallel rather than disordered bundles during cell adhesion and cell motion. The effect of filament undulations on network stiffness is explored briefly. The results show that undulations can soften the network by increasing the bending-dominated deformations in filaments and bundles. Finally, we find that the effect of the relative density of bundles depends on their orientation. Increasing the density of randomly distributed bundles has no effect on the stiffness of cells, but softens the cytoskeleton network. In contrast, the stiffness of networks of parallel bundles first increases, then reduces as the relative density of bundles increases. The stiffest network is a mixture of actin filaments and bundles.

基于找形模型研究微丝束对细胞骨架刚度的影响

研究目的：基于找形分析建立的细胞骨架力学模型研究微丝束对细胞骨架刚度的影响。
创新要点：目前存在的细胞模型很少考虑微丝束对细胞力学特性的重要作用。本文基于细胞找形模型模拟了同时包含微丝和微丝束的细胞骨架网络结构，并且分析了细胞中微丝束的排列方向、微丝束的含量以及微丝波动对细胞刚度的影响。
研究方法：基于找形模型，随机生成由微丝、微丝束（梁单元）以及交联蛋白（索单元）形成的细胞骨架网络结构，依靠非线性有限元计算和样本统计，计算出模型的弹性模量。通过分别改变模型中微丝束的排列方向、微丝束的含量以及模型初始最大位移等参数，得出细胞骨架模型的弹性模量随这些参数的变化趋势，以此来研究微丝束对细胞刚度的影响。
重要结论：细胞骨架网络中微丝的波动会导致细胞刚度降低；与拉伸方向平行排列的微丝束可以显著地提高细胞的刚度，相比之下随机分布的微丝束对细胞刚度没有贡献；在微丝材料总量固定的情况下，细胞刚度随着平行排列微丝束含量的增加呈现出先升高后降低的趋势。
细胞骨架网络；找形模型；弹性模量；微丝束

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