SARS-CoV-2 Infection of Pluripotent Stem Cell-derived Human Lung Alveolar Type 2 Cells Elicits a Rapid Epithelial-Intrinsic Inflammatory Response

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>The most severe and fatal infections with SARS-CoV-2 result in the acute respiratory distress syndrome, a clinical phenotype of coronavirus disease 2019 (COVID-19) that is associated with virions targeting the epithelium of the distal lung, particularly the facultative progenitors of this tissue, alveolar epithelial type 2 cells (AT2s). Little is known about the initial responses of human lung alveoli to SARS-CoV-2 infection due in part to inability to access these cells from patients, particularly at early stages of disease. Here we present an <jats:italic>in vitro</jats:italic> human model that simulates the initial apical infection of the distal lung epithelium with SARS-CoV-2, using AT2s that have been adapted to air-liquid interface culture after their derivation from induced pluripotent stem cells (iAT2s). We find that SARS-CoV-2 induces a rapid global transcriptomic change in infected iAT2s characterized by a shift to an inflammatory phenotype predominated by the secretion of cytokines encoded by NF-kB target genes, delayed epithelial interferon responses, and rapid loss of the mature lung alveolar epithelial program. Over time, infected iAT2s exhibit cellular toxicity that can result in the death of these key alveolar facultative progenitors, as is observed <jats:italic>in vivo</jats:italic> in COVID-19 lung autopsies. Importantly, drug testing using iAT2s confirmed the efficacy of TMPRSS2 protease inhibition, validating putative mechanisms used for viral entry in human alveolar cells. Our model system reveals the cell-intrinsic responses of a key lung target cell to infection, providing a platform for further drug development and facilitating a deeper understanding of COVID-19 pathogenesis.</jats:p>

Adult Stem Cell-derived Complete Lung Organoid Models Emulate Lung Disease in COVID-19

“…These findings are consistent with the well-established notion that ALI conditions favor growth as pseudo-stratified mucociliary epithelium (Dvorak et al, 2011;Prytherch et al, 2011). As an alternative model for use as monolayers for viral infection, we developed hiPSC-derived AT2 cells and alveolospheres (Fig 3C), using established protocols (Huang et al, 2020). Because they were grown in the presence of CHIR99021 (an aminopyrimidine derivate that is a selective and potent Wnt agonist) (Abdelwahab et al, 2019;, which probably inhibits the AT2→AT1 differentiation, these monolayers were enriched for AT2 and devoid of AT1 cells (Fig 3D).…”

“…Although somewhat unexpected, the role of AT1 pneumocytes in mounting innate immune responses has been documented before in the context of bacterial pneumonia (Wong and Johnson, 2013;Yamamoto et al, 2012). In work (Huang et al, 2020) that was published during the preparation of this manuscript, authors used long-term ALI models of hiPSC-derived AT2 monolayers (in growth conditions that inhibit AT2→AT1 differentiation, as we did here for our AT2 model) and showed that SARS-CoV-2 induces iAT2-intrinsic cytotoxicity and inflammatory response, but failed to induce type 1 interferon pathways (IFN α/β). It is possible that prolonged culture of iAT2 pneumocytes gives rise to some DATPs but cannot robustly do so in the presence of inhibitors of AT1 differentiation.…”

“…To model respiratory infections such as COVID-19, it is necessary for pathogens to be able to access the apical surface. Many groups have modeled such access by dissociating 3D organoids into single cells and plating them as 2D-monolayers (Duan et al, 2020;Han et al, 2020;Huang et al, 2020;Mulay et al, 2020;. Because the loss of dimensionality can have a major impact on cellular proportions and impact disease-modeling in unpredictable ways, we assessed the impact of the 3D-to-2D conversion on cellularity by RNA seq analyses.…”

Identifying and repurposing antiviral drugs against severe acute respiratory syndrome coronavirus 2 with in silico and in vitro approaches

“…In line with this argument, examining drug activity in physiologically relevant cells is essential for prospecting in vivo antiviral efficacy. Human airway epithelial cells in an air-liquid interface culture [ 86 ] and human induced pluripotent stem cell-derived lung epithelial cells [ 87 , 88 ] will provide more physiological relevance to the study of SARS-CoV-2 infections. In addition, human organoids of a variety of tissues such as lung, intestine, blood vessel, kidney, liver, and brain were reported to be susceptible to infection by SARS-CoV-2 or its pseudovirus [ [89] , [90] , [91] , [92] , [93] , [94] , [95] , [96] ].…”

Human Induced Pluripotent Stem Cell-Derived Lung Epithelial System for SARS-CoV-2 Infection Modeling and Its Potential in Drug Repurposing

“…Based on available literature [7], we employed the directed differentiation technique to derive lung epithelial lineage from human induced pluripotent stem cells (hiPSC), to serve as a human model, using a three-step protocol (Fig. 1A) [8,9].…”