Epithelial tissues function as barriers that separate the organism from the environment. They usually have highly curved shapes, such as tubules or cysts. However, the processes by which the geometry of the environment and the cell's mechanical properties set the epithelium shape are not yet known. In this study, we encapsulated two epithelial cell lines, MDCK and J3B1A, into hollow alginate tubes and grew them under cylindrical confinement forming a complete monolayer. MDCK monolayers detached from the alginate shell at a constant rate, whereas J3B1A monolayers detached at a low rate unless the tube radius was reduced. We showed that this detachment is driven by contractile stresses in the epithelium and can be enhanced by local curvature. This allows us to conclude that J3B1A cells exhibit smaller contractility than MDCK cells. Monolayers inside curved tubes detach at a higher rate on the outside of a curve, confirming that detachment is driven by contraction.

Abstract:Epithelial tissues are essential to keep a proper barrier for the organism. They usually have highly curved shapes, such as tubules or cysts. However, interplays between the environment and cell mechanical properties to set the shape are not known. In this study, we encapsulated two epithelial cell lineages, MDCK and J3B1A, into hollow alginate tubes and grew them under cylindrical confinement. Once formed, the epithelial MDCK layer detached from the alginate shell, while J3B1A layer remained adherent. Detachment resulted from contractile forces within cell layers that pulled cells away from the shell. We concluded that J3B1A cells have lower contractility than MDCK cells. As the pulling forces depend on the radius of the tube, we induced detachment of J3B1A cells by reducing the size of the hollow tube by two. Moreover, in bent tubes, detachment was more pronounced on the outer side of the turn, while extrusion occurred in the inner side, further highlighting the coupling between curvature and cell contractility. Introduction: