Figure 1.

Stochastic lattice spring model predicts increased cell spreading at low initial stiffness on viscoelastic substrates that exhibit stress relaxation relative to elastic substrates. (a) Schematic depicting model of cell spreading on elastic or viscoelastic substrates. Actin polymerization at the leading edge of the cell is coupled to the substrate through molecular clutches, and these clutches inhibit retrograde flow of the actin driven by myosin motors. The substrate is modeled as an array of nodes connected by either Hookean springs, representing an elastic substrate, or Burgers model elements, representing a viscoelastic substrate exhibiting stress relaxation. (b) Simulation results for cell spreading area on elastic substrates as a function of initial substrate stiffness and adhesion ligand density. (c) Simulation results for cell spreading area on substrates with stress relaxation as a function of initial substrate stiffness and adhesion ligand density. Voigt damping coefficient, η₁, was 5x10⁻¹³, and Maxwell damping coefficient, η₂, was 1x10⁻¹³ for this set of simulations (See Supplementary Information). (d) Difference in cell spreading area for cells on substrates with stress relaxation relative to elastic substrates. Greater spreading on substrates with stress relaxation is observed for all conditions at low substrate stiffness.