Force Localization in Contracting Cell Layers

CM Edwards and US Schwarz

Phys. Rev. Lett. 107, 128101 (2011)

Epithelial cell layers on soft elastic substrates or pillar arrays are
commonly used as model systems for investigating the role of force in
tissue growth, maintenance, and repair. Here we show analytically that
the experimentally observed localization of traction forces to the
periphery of the cell layers does not necessarily imply increased
local cell activity, but follows naturally from the elastic problem of
a finite-sized contractile layer coupled to an elastic foundation. For
homogeneous contractility, the force localization is determined by one
dimensionless parameter interpolating between linear and exponential
force profiles for the extreme cases of very soft and very stiff
substrates, respectively. If contractility is sufficiently increased
at the periphery, outward directed displacements can occur at
intermediate positions. We also show that anisotropic extracellular
stiffness can lead to force localization in the stiffer direction, as
observed experimentally.