Collective migration of epithelial cells in the presence of regularly spaced obstacles

Physical confinement plays a crucial role in tissue development, creating a microenvironment and contributing to tumorigenesis. We investigate how physical confinement affects the collective behavior of Madin-Darby Canine Kidney (MDCK) II epithelial monolayers by introducing regularly spaced adhesive micropillars as stiff adhesive obstacles. By utilizing optical flow to quantify velocity fields, we find that micropillars disrupt collective motion and gradually decrease spatial correlation and directionality. The role of cellular junctions is examined by monitoring the dynamics of MDCK II mutants deficient in tight junction (TJ) proteins ZO1/2 and adherens junction (AJ) protein E-cadherin. TJ deficiency goes hand in hand with increased apical contractility and thereby fosters jamming, leading to generally slower, more diffusive, and spatially uncorrelated movement and an even greater reduction in collectivity in the presence of micropillars. Similarly, AJ impairment significantly decreases spatial correlation and cellular velocity but to a lesser extent. Our findings reveal that collective motion is drastically affected at a certain length scale, i.e., an interpillar distance < 80 μm, where cells resort to a more diffusive and spatially uncorrelated migration reminiscent of single-cell migration. These insights advance our understanding of how physical confinement, intercellular junctions and elevated contractility modulate collective dynamics in epithelial cells.