Cell collision outcomes in suspended fiber environments as controlled by physical and geometric factors

Cell migrations and interactions are essential for many physiological processes and pathologies, and are usually studied through cellular motion and collisions on 2D flat substrates, where colliding cells reverse directions and move away from contact (termed contact inhibition of locomotion or CIL). Unlike 2D surfaces, suspended nanofibers closely resembling extracellular matrix provide a more biologically native environment for cell-cell collisions, whose outcomes are more various than classical CIL, such as cells sticking to or walking past each other while crawling along fibers. Inspired by experiments, we use a phase-field model to numerically simulate two-cell collisions in fiber geometries, especially the effects of cellular mechanics and geometric factors on their outcomes. We focus on cell behaviors on two parallel fibers, showing that greater abilities of cells to deform and polarize, in addition to larger fiber spacing, can lead to more walk-past rather than sticking together upon collision. This is consistent with a simple linear stability analysis on the cell-cell interface at collision. Our results illustrate the roles of both cell-cell and cell-matrix interactions in controlling cell motility.