Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, North Brabant, Netherlands; Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, Eindhoven, The Netherlands.
Department of Engineering, University of Cambridge, Cambridge, United Kingdom.
Biophys J. 2019 May 21;116(10):1994-2008. doi: 10.1016/j.bpj.2019.04.003. Epub 2019 Apr 10.
Contact guidance-the widely known phenomenon of cell alignment induced by anisotropic environmental features-is an essential step in the organization of adherent cells, but the mechanisms by which cells achieve this orientational ordering remain unclear. Here, we seeded myofibroblasts on substrates micropatterned with stripes of fibronectin and observed that contact guidance emerges at stripe widths much greater than the cell size. To understand the origins of this surprising observation, we combined morphometric analysis of cells and their subcellular components with a, to our knowledge, novel statistical framework for modeling nonthermal fluctuations of living cells. This modeling framework is shown to predict not only the trends but also the statistical variability of a wide range of biological observables, including cell (and nucleus) shapes, sizes, and orientations, as well as stress-fiber arrangements within the cells with remarkable fidelity with a single set of cell parameters. By comparing observations and theory, we identified two regimes of contact guidance: 1) guidance on stripe widths smaller than the cell size (w ≤ 160 μm), which is accompanied by biochemical changes within the cells, including increasing stress-fiber polarization and cell elongation; and 2) entropic guidance on larger stripe widths, which is governed by fluctuations in the cell morphology. Overall, our findings suggest an entropy-mediated mechanism for contact guidance associated with the tendency of cells to maximize their morphological entropy through shape fluctuations.
接触导向——即细胞沿着各向异性的环境特征发生定向排列的现象，是贴壁细胞进行组织排列的重要步骤，但细胞实现这种定向有序排列的机制仍不清楚。在这里，我们将成纤维细胞接种到纤维连接蛋白条纹微图案化的基质上，观察到接触导向出现在宽度远大于细胞尺寸的条纹上。为了理解这一令人惊讶的观察结果的起源，我们结合了细胞及其亚细胞成分的形态测量分析，以及我们所知的用于模拟活细胞非热波动的新颖统计框架。该建模框架不仅可以预测细胞（和细胞核）形状、大小和取向等广泛生物学可观察量的趋势，还可以预测其统计可变性，以及细胞内应力纤维排列的趋势和统计可变性，其预测结果与一组细胞参数具有惊人的一致性。通过比较观察结果和理论，我们确定了接触导向的两种模式：1）在小于细胞尺寸的条纹宽度上的导向（w ≤ 160 μm），这伴随着细胞内的生化变化，包括增加的应力纤维极化和细胞伸长；2）在较大的条纹宽度上的熵导向，由细胞形态的波动所控制。总的来说，我们的发现表明，接触导向存在一种熵介导的机制，与细胞通过形状波动来最大化其形态熵的趋势有关。
