Morphology and Motility of Cells on Soft Substrates*

Cells are greatly influenced by the mechanical properties of their environment. To study the cellular response to traction-induced substrate deformations, we extend a cellular Potts model of actively polarizing cells with a coarse description of the viscoelastic substrate. Apart from the influence of substrate stiffness, we demonstrate the importance of dissipative effects in the form of viscous friction.

For low viscous friction, i.e. a small lag between cellular traction stresses and the resulting strain, a soft substrate leads to the reduction of the cell speed and persistence time of directed migration. Furthermore, we observe a profound elongation at the lower end of substrate stiffnesses both in our simulations and for HUVECs on PA gels functionalized with collagen.

In contrast, cells on substrates with a high viscous friction are only slightly affected by the resulting deformations, because they can travel faster than the substrate strain. Here, a softer substrate causes a marginal increase in cell speed.