Collective migration of cells in confinement - contact following and contact inhibition of locomotion

Collective cell migration, in which cells crawl in a coordinated, coherent way, is crucial in embryonic development and cancer metastasis. The extent of collective migration is controlled by how cells interact, which is often studied in cell pairs. When crawling cells collide head-on, some perform contact inhibition of locomotion (CIL), repolarizing away from contact and separating. However, recent work has established that cells may induce cells in contact with their back to follow them - "contact following of locomotion" (CFL). We build a model for CIL and CFL within the phase-field approach, which treats cells as continuously deformable objects. We hypothesize that cells can sense their velocity and repolarize to align to it over a finite timescale. With this assumption, we are able to reproduce the observed CIL within narrow linear confinement. We show the probability of CIL outcomes depends on the strength of alignment between cell velocity and polarity. We can also capture the experimental CFL behavior of cells migrating into Y-junctions. We show that the outcome of a train of cells meeting a Y-junction depends on junction geometry, strength of alignment and cell-cell adhesions.