Modeling cell motility at mechanical interfaces

Many animal cells crawl by adhering to and exerting active mechanical forces on elastic extracellular substrates. Experiments with adherent cells show that cells align preferentially at interfaces between soft and stiff regions of the substrate resulting in durotaxis. We use agent-based Brownian dynamics simulations to study the mechanical interactions between motile cells. The cells are modeled as self-propelling agents that exert active force dipoles on the substrate leading to inter-cell and cell boundary interactions. Elastic effects at the interface between soft and stiff regions of the substrate are simulated using appropriate clamped or free boundary conditions. We find that torques due to these boundary interactions strongly align crawling cells at the interface analogous to hydrodynamic torques on swimming bacteria. We systematically investigate the collective motility and density distributions of a collection of model cells that result from these interfacial elastic interactions. We then compare quantitative structural metrics of the patterns that ensue in these systems with full interactions to simulations of cells that interact elastically with the boundary but not with each other.