Abstract：
Eukaryotic cell rheology has important consequences for vital processes such as adhesion, migration, and differentiation. Experiments indicate that cell cytoplasm can exhibit both elastic and viscous characteristics in different regimes, while the transport of fluid (cytosol) through the cross-linked filamentous scaffold (cytoskeleton) is reminiscent of mass transfer by diffusion through a porous medium. To gain insights into this complex rheological behaviour, we construct a computational model for the cell cytoplasm as a poroviscoelastic material formulated on the principles of nonlinear continuum mechanics, where we model the cytoplasm as a porous viscoelastic scaffold with an embedded viscous fluid flowing between the pores to model the cytosol. Baseline simulations (neglecting the viscosity of the cytosol) indicate that the system exhibits seven different regimes across the parameter space spanned by the viscoelastic relaxation timescale of the cytoskeleton and the poroelastic diffusion timescale; these regimes agree qualitatively with experimental measurements. Furthermore, the theoretical model also allows us to elucidate the additional role of pore fluid viscosity, which enters the system as a distinct viscous timescale. We show that increasing this viscous timescale hinders the passage of the pore fluid (reducing the poroelastic diffusion) and makes the cytoplasm rheology increasingly incompressible, shifting the phase boundaries between the regimes.
摘要：
真核细胞流变学对重要的过程，如粘附，迁移,和差异化。实验表明，细胞质在不同的状态下可以同时表现出弹性和粘性特征，而流体（胞质溶胶）通过交联的丝状支架（细胞骨架）的运输让人想起通过多孔介质扩散的传质。为了深入了解这种复杂的流变行为，我们构建了一个计算模型的细胞质作为多孔粘弹性材料的非线性连续介质力学的原理，其中我们将细胞质建模为多孔粘弹性支架，其中嵌入的粘性流体在孔之间流动以模拟细胞质。基线模拟（忽略细胞溶胶的粘度）表明，该系统在参数空间上表现出七个不同的状态，该状态由细胞骨架的粘弹性松弛时间尺度和多孔弹性扩散时间尺度所跨越；这些状态与实验测量在质量上一致。此外，理论模型还使我们能够阐明孔隙流体粘度的附加作用，它以独特的粘性时间尺度进入系统。我们表明，增加这种粘性时间尺度会阻碍孔隙流体的通过（减少多孔弹性扩散），并使细胞质流变学越来越不可压缩，改变政权之间的相位边界。
