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

ABSTRACT: 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 in vitro 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 in vivo 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.

SUBMITTER: Huang J

PROVIDER: S-EPMC7337394 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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

Huang Jessie J Hume Adam J AJ Abo Kristine M KM Werder Rhiannon B RB Villacorta-Martin Carlos C Alysandratos Konstantinos-Dionysios KD Beermann Mary Lou ML Simone-Roach Chantelle C Lindstrom-Vautrin Jonathan J Olejnik Judith J Suder Ellen L EL Bullitt Esther E Hinds Anne A Sharma Arjun A Bosmann Markus M Wang Ruobing R Hawkins Finn F Burks Eric J EJ Saeed Mohsan M Wilson Andrew A AA Mühlberger Elke E Kotton Darrell N DN

bioRxiv : the preprint server for biology 20200806

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, particula ...[more]

PMID: 32637964

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Project description:The coronavirus disease 2019 (COVID-19) pandemic has affected nearly 700 million and claimed more than 6 million lives. However, the large heterogeneity in disease susceptibility and severity of illness (SOI) remains poorly understood. A growing body of evidence suggests that alveolar epithelial cell type 2 (AT2), which constitute 10-15% of all alveolar cells and are critical for alveolar homeostasis, are the primary targets of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and damage to AT2s may directly contribute to disease severity and poor prognosis in COVID-19 patients. Our in-vitro modeling of SARS-CoV-2 infection, in well-characterized, highly uniform, (r2 at 95% CI = 0.92 ± 0.03), induced pluripotent stem cell (iPSC) derived AT2s from 10 participants of our Mexican American Family Study, showed interindividual variability in infection susceptibility and the post-infection cellular viral load. To understand the underlying mechanism of the AT2’s capacity to regulate SARS-CoV-2 infection and cellular viral load, we performed a systematic characterization of the pre- and post-SARS-CoV-2 challenged AT2 transcriptomes. A total of 1,393 genes were found significantly (Oneway ANOVA FDR corrected p ≤ 0.05; FC abs ≥ 2.0) differentially expressed (DE) between pre- and post-SARS-CoV-2 infection-challenged AT2 and suggest significant upregulation of viral infection-related cellular innate immune response pathways (p-value ≤ 0.05; activation z-score ≥ 3.5), whilst the cholesterol and xenobiotic related metabolic pathways were significantly downregulated (p-value ≤ 0.05; activation z-score ≤ - 3.5). Interestingly, pre-infection expression of 238 DE genes showed a high correlation with the post-infection SARS-CoV-2 viral load (FDR corrected p-value ≤ 0.05, and r2-absolute ≥ 0.57). The 85 genes whose expression was negatively correlated with the viral load showed significant enrichment in viral recognition and cytokine-mediated innate immune GO biological processes (p-value range: 4.65x10-10 to 2.24x10-6). The 153 genes whose expression was positively correlated with the viral load showed significant enrichment in cholesterol homeostasis, extracellular matrix, and MAPK/ERK pathway-related GO biological processes (p-value range: 5.06x10-5 to 6.53x10-4). Overall, our results strongly suggest that AT2s pre-infection innate immunity and metabolic state affects their susceptibility to SARS-CoV-2 infection and viral load.

Project description:Lung regeneration is dependent on the availability of progenitor lung cells. Large numbers of self-renewing, patient-specific induced pluripotent stem cell-derived alveolar epithelial cells (iPSC-AECs) are needed to adequately recellularize whole-organ constructs. Prior methods to generate functional iPSC-AECs are not feasible for large-scale cell production. We present a novel protocol to produce iPSC-AECs, which is scalable for whole-organ regeneration. Differentiation of iPSCs was performed with genetically modified iPSCs with fluorescent reporters, which underwent differentiation in a stepwise protocol mimicking lung development. Cells were purified, sorted, and embedded in a liquid Matrigel precursor either to form adherent droplets or to form cell-laden Matrigel spheroids, which were subsequently transferred to spinner flasks with media as floating droplets. After culture, monolayer spheres of iPSC-AECs were isolated to form single cell suspensions. Equal numbers of iPSC-AECs from the two culture conditions were seeded into decellularized lung scaffolds. IPSC-AECs cultured in floating droplets were significantly more proliferative than those in adherent droplets, with significantly higher total cell counts and Ki67 expression. Equivalent expression of the distal lung markers was observed for both culture conditions. Lungs recellularized from both culture groups had similar histological appearance. Media changes took significantly less time with the floating droplet method and was more cost effective. The floating droplet culture method demonstrated enhanced proliferative capacity, stable distal lung epithelial phenotype, and reduced resources compared with prior culture methods. In this study, we provide a means for iPSC-AEC production for regeneration of whole-lung constructs. Impact statement We describe a novel culture method for induced pluripotent stem cell-derived alveolar epithelial cell (AEC) expansion with enhanced proliferative capacity and reduced resource requirements compared with previously described methods. This method is scalable for human whole-lung regeneration bioengineering or could be automated for commercial cell production. This culture method may have implications for the differentiation of type I AECs from type II AECs.

Project description:BackgroundSARS-CoV-2 infects through the respiratory route and triggers inflammatory response by affecting multiple cell types including type II alveolar epithelial cells. SARS-CoV-2 triggers signals via its Spike (S) protein, which have been shown to participate in the pathogenesis of COVID19.AimAim of the present study was to investigate the effect of SARS-CoV2 on type II alveolar epithelial cells, focusing on signals initiated by its S protein and their impact on the expression of inflammatory mediators.ResultsFor this purpose A549 alveolar type II epithelial cells were exposed to SARS CoV2 S recombinant protein and the expression of inflammatory mediators was measured. The results showed that SARS-CoV-2 S protein decreased the expression and secretion of IL8, IL6 and TNFα, 6 hours following stimulation, while it had no effect on IFNα, CXCL5 and PAI-1 expression. We further examined whether SARS-CoV-2 S protein, when combined with TLR2 signals, which are also triggered by SARS-CoV2 and its envelope protein, exerts a different effect in type II alveolar epithelial cells. Simultaneous treatment of A549 cells with SARS-CoV-2 S protein and the TLR2 ligand PAM3csk4 decreased secretion of IL8, IL6 and TNFα, while it significantly increased IFNα, CXCL5 and PAI-1 mRNA expression. To investigate the molecular pathway through which SARS-CoV-2 S protein exerted this immunomodulatory action in alveolar epithelial cells, we measured the induction of MAPK/ERK and PI3K/AKT pathways and found that SARS-CoV-2 S protein induced the activation of the serine threonine kinase AKT. Treatment with the Akt inhibitor MK-2206, abolished the inhibitory effect of SARS-CoV-2 S protein on IL8, IL6 and TNFα expression, suggesting that SARS-CoV-2 S protein mediated its action via AKT kinases.ConclusionThe findings of our study, showed that SARS-CoV-2 S protein suppressed inflammatory responses in alveolar epithelial type II cells at early stages of infection through activation of the PI3K/AKT pathway. Thus, our results suggest that at early stages SARS-CoV-2 S protein signals inhibit immune responses to the virus allowing it to propagate the infection while in combination with TLR2 signals enhances PAI-1 expression, potentially affecting the local coagulation cascade.

Dataset Information

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

Publications

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

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