Fig. 5.

Collective motion, mechanics, and dewetting of cell monolayers. (A) Snapshot of a globally polarized, collectively migrating cell monolayer. (B) Rescaled average polarity $\sqrt{N}{P}_N$ of a monolayer of $N$ cells for different CIL repolarization rates $\psi$ at a cell–cell adhesion ${\overline{W}}_c=0.7$. $\sqrt{N}{P}_N=1$ corresponds to randomly oriented cells. CIL induces a global polarity ($\sqrt{N}{P}_N>1$) that gives rise to collective motion. The appearance of several polarity domains reduces the average polarity of large cell groups. The transition to the active polar liquid state (circles in Fig. 2) is defined by the condition that the maximum of $\sqrt{N}{P}_N$ is at $N=75$. (C) Average cell–cell potential energy ${\overline{E}}_p=E_p/(2R{F}_m)$ as a function of cell–cell adhesion ${\overline{W}}_c$ and CIL repolarization rate $\psi$. CIL-associated repulsion induces tensile stresses (${\overline{E}}_p>0$) in cell monolayers. (D) Average distance between contacting cells ${⟨{\overline{d}}_{ij}⟩}_c={⟨d_{ij}⟩}_c/(2R)$ as a function of ${\overline{W}}_c$ and $\psi$. The transition between cell monolayers and 3D aggregates is predicted to occur at a vanishing average cell–cell force (dashed line) and is identified by the condition ${⟨d_{ij}⟩}_c=3R/2$ (solid line, crosses in Fig. 2).