Reconstituting Stratified Epithelial Branching Morphogenesis by Engineering Cell Adhesion

During embryogenesis, many organs undergo branching morphogenesis to form tree-like hierarchical structures. However, it remains unclear what drives branching in stratified epithelia, such as in embryonic salivary gland and pancreas. Here, we performed live-organ imaging of mouse embryonic salivary glands at single-cell resolution to reveal branching driven by expansion and folding of an epithelial surface cell sheet characterized by strong cell-matrix adhesion and weak cell-cell adhesion. We successfully reconstituted this early developmental process by experimentally suppressing E-cadherin expression and inducing basement membrane formation in 3D spheroid cultures of engineered cells. Reconstituted branching required integrin-mediated cell-matrix adhesions and was promoted by elevating cell-matrix adhesion strength. Thus, stratified epithelial branching is driven by the combination of strong cell-matrix adhesion and weak cell-cell adhesion of peripheral epithelial cells.