Clustering and ordering in cell assemblies with generic asymmetric aligning interactions

Collective cell migration plays an essential role in various biological processes, such as development or cancer proliferation. While cell-cell interactions are clearly key determinants of collective cell migration, the physical mechanisms that control the emergence of cell clustering and collective cell migration are still poorly understood. Binary cell-cell collisions generally lead to anti-alignment of cell polarities and separation of pairs -- a process called contact inhibition of locomotion (CIL), which is expected to hinder the formation of coherent large scale cell clusters. Here, we report on a joint experimental and theoretical approach in which we determine the large scale dynamics of cell assemblies from elementary pairwise cell-cell interaction rules. We develop a generic equilibrium-like pairwise asymmetric aligning interaction potential that reproduces the CIL phenomenology. We build the corresponding active hydrodynamic theory and show that such asymmetric aligning interaction generically destroys large scale clustering and ordering. We conclude that CIL-like asymmetric interactions in general active systems control cluster sizes and polarity, and can prevent large-scale coarsening and long-range polarity, except in the singular regime of dense confluent systems.