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

## TL;DR

This study compares Calu-3 cells in submerged and air-liquid interface conditions to better understand lung infection modeling.

## Contribution

The study provides the first profiling of proteome and transcriptome changes in Calu-3 cells transitioning to polarized air-liquid interface conditions.

## Key findings

- Polarized Calu-3 cells show higher activation of energy production and immune molecule expression.
- Protein quality control and antigen processing are upregulated in polarized cells.
- SARS-CoV-2 infection in polarized cells leads to increased cell death linked to higher ACE2 expression.

## Abstract

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.