arXiv 2501.059712025-01-10cond-mat.softphysics.bio-ph

由活性丝束引导的湍流所涌现的细胞动力学

Cellular dynamics emerging from turbulent flows steered by active filaments

Mehrana R. Nejad, Julia M. Yeomans, Sumesh P Thampi

AI总结：

提出含两个张量序参量的连续介质理论，揭示活性丝束流动排列参数如何调控上皮细胞层的活性湍流、细胞取向及拓扑缺陷运动。

摘要：

我们建立了一套连续介质理论，用以描述可变形上皮细胞的集体动力学；该理论采用两个张量序参量，将细胞内产生力的活性丝束与细胞形状区分开来。理论展示了活性流动如何创建各向异性细胞的向列相畴、驱动活性湍流并产生拓扑缺陷。我们表明，丝束流动排列参数 $λ_{\ ens{Q}}$ 是一个流变学量，决定丝束对活性流动中速度梯度的响应；它在决定拉伸与压缩活性流动的模式方面发挥了迄今未被重视的重要作用。在收缩性细胞层中，局部流动预期会使细长细胞垂直于活性丝束排列。然而，随着 $λ_{\ ens{Q}}$ 增大，活性湍流流场中的长程关联导致出现延伸区域，在这些区域中这种排列变为平行，正如最近在融合 MDCK 细胞层实验中观察到的那样。此外，双序参量形式体系使我们能够区分丝束指向矢场中的缺陷与形状指向矢场中的缺陷：前者贡献于活性驱动，后者在实验中被测量并由活性流动平流输运。通过考虑形状与丝束的相对取向，我们能够解释收缩性细胞层中缺陷朝向其头部运动这一令人惊讶的观察结果。

英文摘要：

We develop a continuum theory to describe the collective dynamics of deformable epithelial cells, using two tensor order parameters to distinguish the force-generating active filaments in the cells from their shape. The theory demonstrates how active flows create nematic domains of anisotropic cells, drive active turbulence, and create topological defects. We show that the filament flow-aligning parameter, $λ_{\tens{Q}}$, a rheological quantity that determines the response of the filaments to velocity gradients in the active flows, plays a significant, to date unappreciated, role in determining the pattern of extensional and compressional active flows. In a contractile cell layer, local flows are expected to align elongated cells perpendicular to the active filaments. However, with increasing $λ_{\tens{Q}}$, long-range correlations in the active turbulent flow field lead to extended regions where this alignment is parallel, as recently observed in experiments on confluent MDCK cell layers. Further, the two order parameter formalism allows us to distinguish defects in the filament director field, which contribute to the active driving, and those in the shape director field, measured in experiments, which are advected by the active flows. By considering the relative orientations of shape and filaments we are able to explain the surprising observation of defects moving towards their heads in contractile cell layers.

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