Air-Liquid Interface Induced Epithelial Delamination

Many epithelial tissues reside at air-liquid interfaces, as exemplified by the ocular epithelium, oral mucosa, and alveolar epithelium. The interfacial tension across the epithelial tissues imposes a mechanical challenge to the homeostasis of the tissue. However, the interplay between interfacial properties and homeostasis in biological samples has been overlooked due to a lack of suitable measurement methods and theoretical developments. Here we described a surprising observation in which the surface energy at cell-air interface is sufficient to delaminate a stratified ocular epithelium from its substrate. We demonstrated that the interfacial tension at the epithelium-fluid interfaces can be measured using a modified Schultz method. The measured value is conceptually and numerically distinctive to the tensile modulus measured by deformation-based methods, such as micropippeting and tissue surface tensiometers. Furthermore, a mechanical analysis at the cell-air-liquid triple line during the delamination process revealed a strain hardening behavior of the epithelial layers. Finally, perturbations on different junctional protein complexes revealed that a delicate balance among cortical tension, focal adhesion, and cell-liquid interfacial tension is required for the epithelial tissue mechanical stability.