Curling of epithelial monolayers reveals coupling between active bending and tissue tension

Significance Epithelial monolayers are sheet-like tissues composed of cells connected to one another that line the surface of all organs. These tissues change shape and bend during developmental morphogenesis or early in tumor formation. Yet, the amplitude of bending forces and how they integrate with tensile and compressive forces within the plane of the tissue remain largely unknown. By revealing the ability of epithelial monolayers to curl, we demonstrate that the polarization of contractile molecular motors within the tissue thickness generates high spontaneous curvature of the sheet. We quantify the corresponding torques and show that stretch and compression within the tissue plane can substantially impact curling. Such mechanical coupling could be at play during epithelial morphogenesis.