Epithelial monolayers develop density and effective temperature differentials to migrate across confined matrices

Abstract

Collective migration of epithelial cells across heterogeneous environments regulates vital physiological and pathological processes, such as embryogenesis, wound healing, tissue regeneration, and cancer metastasis. In response to matrix stiffness and topography, epithelial monolayers undergo jamming-unjamming transitions. Although previous studies have shown different migration phenotypes separately in confined and unconfined environment, physical transitions required for collective cell populations to negotiate confined regions remain unknown. To address this question, we fabricated PDMS substrates with contiguous wide (200 μm) and narrow (50 μm) microchannels, and studied collective migration of MCF10A (WT) epithelial cells. We found that cells develop a density differential in wide regions, relative to narrow channels, which could generate enough pressure for their eventual migration into confinement. To understand whether cell-cell cohesivity alters this requirement of density differential, we used cells with constitutively-active RhoA (+RhoA) for higher cohesivity and overexpressed ErbB2 (+ErbB2) for cancer-like reduced cohesion. We found that more cohesive cells (+RhoA) developed higher density differential relative to less cohesive cells for migration across confinement. While confined channels allowed for faster migration in WT cells, this confinement sensitivity was diminished for both alternations in cell cohesivity. With migration into confinement, cells deformed their shapes and increased their effective temperature, calculated by treating cells as a granular thermodynamic system. Further, more cohesive cells (+RhoA) and those in confined regions were effectively warmer. Overall, our results show that collective cell populations build a pressure differential between narrow and wide matrices to enter confined environments and these requirements vary for cell types of varying cohesivity. These findings show that collective cell migration across confinements can be interpreted in terms of basic physical principle of pressure and temperature of granular matter, which could inform our understanding of more complex living systems.