Molecular Characterization of Calu‑3 Cells from Submerged to Air–Liquid Interface to Model Lung Infections

The air–liquid interface (ALI) model using Calu-3 cells has been used to model lung diseases. In ALI, Calu-3 polarizes and changes to a mucus-producing cell. Polarized Calu-3 similarity with primary cells has been proven; however, no studies have been focusing on the pathways differentially expressed in ALI. Here, we profiled the proteome and transcriptome of Calu-3 from submerged (nonpolarized) to ALI (polarized) conditions, and in the omics data, we observed an increase in cell replication in the nonpolarized condition while polarized cells presented higher activation of cellular energy production, protein maturation and recycle, and expression of immune molecules. Moreover, the omics findings showed upregulation of different biological processes related to the protein quality control system and antigen processing presentation in polarized cells. Immunoblot and fluorescence microscopy confirmed increased expression of bronchial epithelium integrity components such as mucus and tight junctions in polarized cells and revealed a characteristic protein expression and cellular organization found in normal lung epithelium. Furthermore, SARS-CoV-2 infection in polarized cells revealed increased cell death associated with the higher expression of ACE2. The differences observed in this study give us a better understanding of how ALI can mimic human bronchial-epithelial cells and its applications in different contexts of lung diseases.