Human airway ex vivo models: new tools to study the airway epithelial cell response to SARS-CoV-2 infection

Airway-liquid interface cultures of primary epithelial cells and of induced pluripotent stem cell-derived airway epithelial cells (ALI and iALI, respectively) are physiologically relevant models for respiratory virus infection studies because they can mimic the in vivo human bronchial epithelium. Here, we investigated gene expression profiles in human airway cultures (ALI and iALI models) infected or not with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using publicly available and our own bulk and single-cell transcriptome datasets. SARS-CoV-2 infection significantly increased the expression of interferon-stimulated genes (IFI44, IFIT1, IFIT3, IFI35, IRF9, MX1, OAS1, OAS3 and ISG15) and inflammatory genes (NFKBIA, CSF1, FOSL1, IL32 and CXCL10) at day 4 post-infection, indicating activation of the interferon and immune responses to the virus. Extracellular matrix genes (ITGB6, ITGB1 and GJA1) also were altered in infected cells. Single-cell RNA sequencing data revealed that SARS-CoV-2 infection damaged the respiratory epithelium, particularly mature ciliated cells. The expression of genes encoding intercellular communication and adhesion proteins also was deregulated, suggesting a mechanism to promote shedding of infected epithelial cells. These data demonstrate that ALI/iALI models help to understand the airway epithelium response to SARS-CoV-2 infection and are a key tool for developing COVID-19 treatments.