Mechanical behavior of a migrating cell monolayer.

Collective cell migration contributes to morphogenesis, wound healing or tumor metastasis. Culturing epithelial monolayers on a substrate is an in vitro configuration suitable to quantitatively characterize such
tissue migration by measuring cell velocity, density and cell-substrate interaction force.

We perform migration experiments of Madin-Darby Canine Kidney (MDCK) epithelial cells over a day or more. We observe spontaneous velocity waves, or induce a heterogeneous cell flow around an obstacle to observe cell shape changes and neighbor rearrangements. We quantify the space and time heterogeneity precisely enough to discriminate between models. We also explored the role of the boundaries conditions on the migration.

Together, our experiments and model disantangle the respective contributions of active velocity and of proliferation in monolayer migration. They highlight the importance of strain-polarity coupling and density in long-range information propagation, and show that both elastic and viscous effects can have comparable contributions in the process of collective cell migration. Finally, we discuss the link with in vivo cell migration.