Modeling collective cell migration on substrates with topological defects

Collective migration of cell monolayers is important for both wound healing and development, and an example of active matter physics in biology. Recent experiments have highlighted the importance of liquid crystal order and topological defects within these layers, in particular suggesting that +1 defects have a role in organizing tissue morphogenesis. In this work we perform 2D active Monte Carlo simulations to investigate cell arrangements and motion on a substrate patterned with ridges that induce a +1 defect. We model different cell types as self-propelled deformable ellipses that interact via Gay-Berne potential. We find that, consistent with experiments from the Serra group, cells are denser and more isotropic toward the center of the defect. This density change is controlled by the stiffness of the cells and their preferred aspect ratio.