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Emphysema and chronic obstructive pulmonary disease (COPD) most commonly result from the effects of environmental exposures in genetically susceptible individuals. Genome-wide association studies have implicated ADGRG6 in COPD and reduced lung function, and a limited number of studies have examined the role of ADGRG6 in cells representative of the airway. However, the ADGRG6 locus is also associated with DLCO/VA, an indicator of gas exchange efficiency and alveolar function. Here, we sought to evaluate the mechanistic contributions of ADGRG6 to homeostatic function and disease in type 2 alveolar epithelial cells. We applied an inducible CRISPR interference (CRISPRi) human induced pluripotent stem cell (iPSC) platform to explore ADGRG6 function in iPSC-derived AT2s (iAT2s). We demonstrate that ADGRG6 exerts pleiotropic effects on iAT2s including regulation of focal adhesions, cytoskeleton, tight junctions, and proliferation. Moreover, we find that ADGRG6 knockdown in cigarette smoke-exposed iAT2s alters cellular responses to injury, downregulating apical complexes in favor of proliferation. Our work functionally characterizes the COPD GWAS gene ADGRG6 in human alveolar epithelium. [Display omitted] ADGRG6 variants are implicated by GWASs in chronic obstructive pulmonary disease pathogenesis. Here, we investigated the function of ADGRG6 using a CRISPR-interference system in induced pluripotent stem cell-derived type 2 alveolar epithelial cells. ADGRG6 exerts pleiotropic effects on cell adhesion, cytoskeletal arrangement, proliferation, and response to cigarette smoke injury. [ABSTRACT FROM AUTHOR]

The article focuses on determining the function of nine genes implicated in COPD by GWAS in induced pluripotent stem cell–derived type 2 alveolar epithelial cells (iAT2s) by applying CRISPR. Topics discussed include biology of potential genetic contributors in the lung to COPD, including genome-wide association studies (GWAS) genes, and CRISPRi-mediated knockdown of COPD GWAS genes alters the iAT2 transcriptional program.

To protect against the constant threat of inhaled pathogens, the lung is equipped with cellular defenders. In coordination with resident and recruited immune cells, this defence is initiated by the airway and alveolar epithelium following their infection with respiratory viruses. Further support for viral clearance and infection resolution is provided by adjacent endothelial and stromal cells. However, even with these defence mechanisms, respiratory viral infections are a significant global health concern, causing substantial morbidity, socioeconomic losses, and mortality, underlining the need to develop effective vaccines and antiviral medications. In turn, the identification of new treatment options for respiratory infections is critically dependent on the availability of tractable in vitro experimental models that faithfully recapitulate key aspects of lung physiology. For such models to be informative, it is important these models incorporate human-derived, physiologically relevant versions of all cell types that normally form part of the lungs anti-viral response. This review proposes a guideline using human induced pluripotent stem cells (iPSCs) to create all the disease-relevant cell types. iPSCs can be differentiated into lung epithelium, innate immune cells, endothelial cells, and fibroblasts at a large scale, recapitulating in vivo functions and providing genetic tractability. We advocate for building comprehensive iPSC-derived in vitro models of both proximal and distal lung regions to better understand and model respiratory infections, including interactions with chronic lung diseases. [ABSTRACT FROM AUTHOR]

Frequent, severe wheezy lower respiratory tract viral infections and allergic sensitisation in early life are independently associated with the onset of asthma, and positively interact to markedly increase asthma risk. We have developed a model to interrogate this synergy by inoculating neonatal BALB/c mice with low dose pneumonia virus of mouse (PVM; 1pfu) then exposure to a submaximal dose of cockroach antigen (CRE, 1 μg) 3 days post infection (dpi). CRE exposure following viral infection reduced antiviral immunity (IFN-α, IFN-λ, IL-12p40) and increased viral load in the airway epithelium. Moreover, plasmacytoid dendritic cells stimulated in vitro with CRE exhibited impaired antiviral function. Furthermore, co-exposure to PVM and CRE promoted type 2 inflammation (elevated IL-33, recruitment of eosinophils and type 2 ILCs) and airway remodelling (airway smooth muscle and collagen deposition) at 10 dpi, compared with PVM infection alone. Immunoneutralisation of IL-33 prevented the induction of ILC2s, eosinophilia and importantly inhibited airway remodelling in co-exposed mice. Furthermore, exposure to CRE in early life significantly altered the immune response to the virus and allergen in reinfection. Asthma pathology (airway hyperresponsiveness, airway remodelling, eosinophilia, mast cell hyperplasia) following PVM reinfection (at day 49) and CRE challenge (at days 52, 59, 66 and 80) in later life was significantly elevated in co-exposed neonates. IL-33 blockade in primary and secondary infection significantly reduced all hallmark features of asthma. Our findings demonstrate that by reducing antiviral immunity, allergen exposure early in life increases viral load, and primes toward a Th2 response that drives the progression of asthma in reinfection. Furthermore, we highlight a critical role for IL-33 underlying this virus-allergen synergy and are able to prevent disease onset by targeting this pathway. [ABSTRACT FROM AUTHOR]

There is an urgent need to understand how SARS-CoV-2 infects the airway epithelium and in a subset of individuals leads to severe illness or death. Induced pluripotent stem cells (iPSCs) provide a near limitless supply of human cells that can be differentiated into cell types of interest, including airway epithelium, for disease modeling. We present a human iPSC-derived airway epithelial platform, composed of the major airway epithelial cell types, that is permissive to SARS-CoV-2 infection. Subsets of iPSC-airway cells express the SARS-CoV-2 entry factors angiotensin-converting enzyme 2 (ACE2), and transmembrane protease serine 2 (TMPRSS2). Multiciliated cells are the primary initial target of SARS-CoV-2 infection. On infection with SARS-CoV-2, iPSC-airway cells generate robust interferon and inflammatory responses, and treatment with remdesivir or camostat mesylate causes a decrease in viral propagation and entry, respectively. In conclusion, iPSC-derived airway cells provide a physiologically relevant in vitro model system to interrogate the pathogenesis of, and develop treatment strategies for, COVID-19 pneumonia. [ABSTRACT FROM AUTHOR]

Type-2 immunity elicits tissue repair and homeostasis, however dysregulated type-2 responses cause aberrant tissue remodelling, as observed in asthma. Severe respiratory viral infections in infancy predispose to later asthma, however, the processes that mediate tissue damage-induced type-2 inflammation and the origins of airway remodelling remain ill-defined. Here, using a preclinical mouse model of viral bronchiolitis, we find that increased epithelial and mesenchymal high-mobility group box 1 (HMGB1) expression is associated with increased numbers of IL-13-producing type-2 innate lymphoid cell (ILC2s) and the expansion of the airway smooth muscle (ASM) layer. Anti-HMGB1 ablated lung ILC2 numbers and ASM growth in vivo, and inhibited ILC2-mediated ASM cell proliferation in a co-culture model. Furthermore, we identified that HMGB1/RAGE (receptor for advanced glycation endproducts) signalling mediates an ILC2-intrinsic IL-13 auto-amplification loop. In summary, therapeutic targeting of the HMGB1/RAGE signalling axis may act as a novel asthma preventative by dampening ILC2-mediated type-2 inflammation and associated ASM remodelling. Author summary: Asthma can start at any time in life, although most often begins in early childhood. Wheezy viral bronchiolitis is a major independent risk factor for subsequent asthma. However, key knowledge gaps exist in relation to the sequelae of severe viral bronchiolitis and the pathogenic processes that promote type-2 inflammation and airway wall remodelling, cardinal features of asthma. Our study addresses this gap by identifying high-mobility group box 1 as a pathogenic cytokine that contributes to group 2 innate lymphoid cell-induced airway smooth muscle growth. [ABSTRACT FROM AUTHOR]

Poor maternal diet during pregnancy is a risk factor for severe lower respiratory infections (sLRIs) in the offspring, but the underlying mechanisms remain elusive. Here, we demonstrate that in mice a maternal low-fiber diet (LFD) led to enhanced LRI severity in infants because of delayed plasmacytoid dendritic cell (pDC) recruitment and perturbation of regulatory T cell expansion in the lungs. LFD altered the composition of the maternal milk microbiome and assembling infant gut microbiome. These microbial changes reduced the secretion of the DC growth factor Flt3L by neonatal intestinal epithelial cells and impaired downstream pDC hematopoiesis. Therapy with a propionate-producing bacteria isolated from the milk of high-fiber diet-fed mothers, or supplementation with propionate, conferred protection against sLRI by restoring gut Flt3L expression and pDC hematopoiesis. Our findings identify a microbiome-dependent Flt3L axis in the gut that promotes pDC hematopoiesis in early life and confers disease resistance against sLRIs. [Display omitted] • The milk microbiota of high-fiber diet-fed dams increases infant gut propionate levels • Propionate induces intestinal epithelial cell expression of Flt3L, a DC growth factor • Gut-derived Flt3L promotes DC hematopoiesis in the bone marrow in early life • pDCs confer protection against severe respiratory infection via Treg cell expansion Maternal diet influences infant susceptibility to severe lower respiratory infection, the leading cause of childhood mortality. Sikder et al. demonstrate that a high-fiber diet promotes microbiota that transiently induce Flt3L in the infant gut. Intestinal Flt3L drives neonatal dendritic cell hematopoiesis, subsequent Treg expansion, and disease resistance in early life. [ABSTRACT FROM AUTHOR]

Asthma is a chronic inflammatory disease. Although many patients with asthma develop type-2 dominated eosinophilic inflammation, a number of individuals develop paucigranulocytic asthma, which occurs in the absence of eosinophilia or neutrophilia. The aetiology of paucigranulocytic asthma is unknown. However, both respiratory syncytial virus (RSV) infection and mutations in the receptor for advanced glycation endproducts (RAGE) are risk factors for asthma development. Here, we show that RAGE deficiency impairs anti-viral immunity during an early-life infection with pneumonia virus of mice (PVM; a murine analogue of RSV). The elevated viral load was associated with the release of high mobility group box-1 (HMGB1) which triggered airway smooth muscle remodelling in early-life. Re-infection with PVM in later-life induced many of the cardinal features of asthma in the absence of eosinophilic or neutrophilic inflammation. Anti-HMGB1 mitigated both early-life viral disease and asthma-like features, highlighting HMGB1 as a possible novel therapeutic target. [ABSTRACT FROM AUTHOR]