Eur. Phys. J. E (2021) 44: 137
https://doi.org/10.1140/epje/s10189-021-00141-7

Regular Article - Living Systems

Collective motility and mechanical waves in cell clusters

¹ Center for Theoretical Biological Physics, Rice University, 77030-1402, Houston, TX, USA
² Applied Physics Graduate Program, Rice University, 77005-1827, Houston, TX, USA
³ Department of Physics, Northeastern University, 02115, Boston, MA, USA
⁴ Department of Physics, University of Michigan, 48109-1040, Ann Arbor, MI, USA
⁵ Center for the Study of Complex Systems, University of Michigan, 48109-1107, Ann Arbor, MI, USA

^d lsander@umich.edu

Received: 16 June 2021
Accepted: 11 October 2021
Published online: 15 November 2021

Abstract

Epithelial cell clusters often move collectively on a substrate. Mechanical signals play a major role in organizing this behavior. There are a number of experimental observations in these systems which await a comprehensive explanation. These include: the internal strains are tensile even for clusters that expand by proliferation; the tractions on the substrate are often confined to the edges of the cluster; there can exist density waves within the cluster; and for cells in an annulus, there is a transition between expanding clusters with proliferation and the case where cells fill the annulus and rotate around it. We formulate a mechanical model to examine these effects. We use a molecular clutch picture which allows “stalling”—inhibition of cell contraction by external forces. Stalled cells are passive from a physical point of view and the un-stalled cells are active. By attaching cells to the substrate and to each other, and taking into account contact inhibition of locomotion, we get a simple picture for many of these findings as well as predictions that could be tested.