Linking cell mechanics and 3D cell morphology in confluent tissues

Two-dimensional mechanical models of confluent tissues link the mechanical state of cell monolayers to cell shape anisotropy, predicting whether the material behaves as a solid or loses rigidity. However, in contrast to 2D model predictions, in vitro experiments with MDCK epithelial cells reveal that mechanically solid tissues display cells with significant anisotropy characteristic of a fluid-like state according to these models. We hypothesize that this discrepancy arises from the disregard of mechanical effects along the apical-basal axis, primarily from actin stress fibers located near the basal membrane. To capture these effects, we introduce a 3D continuum mechanics model of an epithelial cell as an elastic cylindrical shell with boundary conditions that account for basal fiber bundles. This approach provides analytical solutions that predict characteristic variations of a cell's cross section along the apical-basal axis, in agreement with experimental micrographs. These findings provide new insights into subcellular morphological cues and contribute to a refined understanding of elasticity at the cellular and tissue scales. By reshaping our view of how active tissues balance stiffness and integrity, this work affects diagnostic strategies that infer tissue function from tissue structure.