Viscous dissipation in the rupture of cell-cell contacts.

Cell-cell adhesions mediated by adherens junctions, structures connecting cells to each other and to the cortical cytoskeleton, are essential for epithelial physical and biological integrity. Nonetheless, how such structures resist mechanical stimuli that prompt cell-cell rupture is still not fully understood. Here we challenge the conventional views on cell-cell adhesion stability, highlighting the importance of viscous dissipation at the cellular level. Using microdevices to measure the rupture energy of cell-cell junctions and synthetic cadherins to discriminate cadherin binding energy from downstream cytoskeletal regulation, we demonstrate that the balance between cortical tension and cell shape recovery time determines a transition from ductile to brittle fracture in cell-cell contact. These findings suggest that junction toughness, defined as the junction disruption energy, is a more accurate measure of junctional stability, challenging the current emphasis on bond energy and tension. Overall, our results highlight the role and the regulation of energy dissipation through the cytoskeleton during junction deformation for epithelial integrity.