Lee Rachel M, Kelley Douglas H, Nordstrom Kerstin N, Ouellette Nicholas T, Losert Wolfgang
Department of Physics and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD, USA.
New J Phys. 2013 Feb 25;15(2). doi: 10.1088/1367-2630/15/2/025036.
Although understanding the collective migration of cells, such as that seen in epithelial sheets, is essential for understanding diseases such as metastatic cancer, this motion is not yet as well characterized as individual cell migration. Here we adapt quantitative metrics used to characterize the flow and deformation of soft matter to contrast different types of motion within a migrating sheet of cells. Using a Finite-Time Lyapunov Exponent (FTLE) analysis, we find that - in spite of large fluctuations - the flow field of an epithelial cell sheet is not chaotic. Stretching of a sheet of cells (i.e., positive FTLE) is localized at the leading edge of migration and increases when the cells are more highly stimulated. By decomposing the motion of the cells into affine and non-affine components using the metric , we quantify local plastic rearrangements and describe the motion of a group of cells in a novel way. We find an increase in plastic rearrangements with increasing cell densities, whereas inanimate systems tend to exhibit less non-affine rearrangements with increasing density.
尽管了解细胞的集体迁移，如上皮细胞层中所见的迁移，对于理解诸如转移性癌症等疾病至关重要，但这种运动的特征尚未像单个细胞迁移那样得到充分表征。在这里，我们采用用于表征软物质流动和变形的定量指标，以对比迁移细胞层内不同类型的运动。通过有限时间李雅普诺夫指数（FTLE）分析，我们发现——尽管存在较大波动——上皮细胞层的流场并非混沌的。细胞层的拉伸（即正FTLE）局限于迁移的前沿，并且当细胞受到更强刺激时会增加。通过使用该指标将细胞运动分解为仿射和非仿射分量，我们量化了局部塑性重排，并以一种新颖的方式描述了一组细胞的运动。我们发现随着细胞密度增加，塑性重排增加，而无生命系统往往随着密度增加表现出较少的非仿射重排。
