Probing Mechanical Interactions Between Lamellipodia and Surrounding Mechanical Environment

Lamellipodia are sheet-like protrusion formed on the leading edge of cells and play a critical role in cell migration and mechanosensing of surrounding environments. Although the molecular players, architecture, and dynamics of the lamellipodia have been investigated extensively, it remains unclear how the lamellipodia mechanically interact with the underlying substrate via sparsely distributed focal adhesion points. To better understand the mechanical interaction between cells and their surrounding environment, we developed an agent-based model of a branched actin network consisting of F-actin, Arp2/3, actin cross-linking protein, myosin motor, and an underlying substrate. Using the model, we investigated the effect of various parameters on force development/relaxation, actin retrograde flow, substrate deformation, traction force, and focal adhesion dynamics. We found that lifetime of focal adhesion shows a biphasic dependence on its total area. Additionally, we identify the conditions for a steady state actin retrograde flow by imposing disassembly of F-actin in a myosin-induced contracting region and assembly near the leading edge.