α5β1 integrin mediates pulmonary epithelial cyst formation.

Background: Formation of the epithelial cyst involves the establishment of apical-basolateral polarity through a series of cellular interactions that are in part mediated by the extracellular matrix (ECM). We report that in a three-dimensional multi-cellular self-assembly model of lung development, 5 integrin regulates epithelial cyst formation through organization of soluble fibronectin matrix into insoluble fibrils through a process called fibrillogenesis. Results: Dissociated murine embryonic lung cells self-assemble into three-dimensional pulmonary bodies that are dependent on 51 integrin mediated fibrillogenesis for cell-cell mediated self-assembly: compaction and epithelial cyst formation. Knockdown of 5 integrin resulted in a significant increase in another mediator of fibrillogenesis, V integrin. Compensatory increased expression of another mediator of fibrillogenesis, V integrin, was not sufficient to normalize epithelial cyst formation. Loss of 5 integrin-mediated fibrillogenesis perturbed the ability of clustered epithelial cells to establish clear polarity, loss of epithelial cell pyramidal shape, and disrupted apical F-actin-rich deposition. Lack of rich central epithelial localization of F-actin cytoskeleton and Podocalyxin suggests that loss of 5 integrin-mediated fibrillogenesis interferes with the normal cytoskeleton organization that facilitates epithelial cysts polarization. Conclusions: We conclude that lung epithelial cyst formation in development is mediated in part by 51 integrin dependent fibrillogenesis. Developmental Dynamics 246:475-484, 2016. (c) 2017 Wiley Periodicals, Inc.