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

Cells respond collectively to diverse physical stimuli such as substrate stiffness, shear stress, and geometric confinement. Confluent epithelial sheets display complex dynamics, including swirls, oscillations, long-range correlations, and density-dependent jamming. Despite extensive studies on substrate stiffness and shear stress, the role of confinement and obstacle length scale in regulating epithelial collectivity has remained unclear. Here, we investigate how physical confinement affects the migration of Madin-Darby Canine Kidney (MDCK) II epithelial monolayers by introducing regularly spaced adhesive micropillars as stiff obstacles. Optical flow analysis shows that micropillars disrupt collective motion, progressively reducing spatial correlation and directionality. To probe the role of junctional integrity, we monitored MDCK II mutants deficient in tight junction (TJ) proteins ZO-1/2 or the adherens junction (AJ) protein E-cadherin. TJ loss, associated with elevated apical contractility, promotes jamming and strongly diminishes collectivity, while AJ deficiency causes a milder reduction in velocity and correlation. Overall, we identify a critical confinement length scale (<80 μ m) at which coordinated migration breaks down, giving rise to slower, more diffusive, and uncorrelated motion.