Idiopathic Pulmonary Fibrosis: A Genetic Disease That Involves Mucociliary Dysfunction of the Peripheral Airways

Emerging cell and molecular targets for treating mucus hypersecretion in asthma

Mucus provides a protective barrier that is crucial for host defense in the lungs. However, excessive or abnormal mucus can have pathophysiological consequences in many pulmonary diseases, including asthma. Patients with asthma are treated with agents that relax airway smooth muscle and reduce airway inflammation, but responses are often inadequate. In part, this is due to the inability of existing therapeutic agents to directly target mucus. Accordingly, there is a critical need to better understand how mucus hypersecretion and airway plugging are affected by the epithelial cells that synthesize, secrete, and transport mucus components. This review highlights recent advances in the biology of mucin glycoproteins with a specific focus on MUC5AC and MUC5B, the chief macromolecular components of airway mucus. An improved mechanistic understanding of key steps in mucin production and secretion will help reveal novel potential therapeutic strategies.

Genomic Profiling for Predictive Treatment Strategies in Fibrotic Interstitial Lung Disease

Idiopathic pulmonary fibrosis (IPF) has traditionally been considered the archetype of progressive fibrotic interstitial lung diseases (f-ILDs), but several other f-ILDs can also manifest a progressive phenotype. Integrating genomic signatures into clinical practice for f-ILD patients may help to identify patients predisposed to a progressive phenotype. In addition to the risk of progressive pulmonary fibrosis, there is a growing body of literature examining how pharmacogenomics influences treatment response, particularly regarding the efficacy and safety profiles of antifibrotic and immunomodulatory agents. In this narrative review, we discuss current studies in IPF and other forms of pulmonary fibrosis, including systemic autoimmune disorders associated ILDs, sarcoidosis and hypersensitivity pneumonitis. We also provide insights into the future direction of research in this complex field.

Pulmonary Fibrosis Ferret Model Demonstrates Sustained Fibrosis, Restrictive Physiology, and Aberrant Repair

Rationale

The role of MUC5B mucin expression in IPF pathogenesis is unknown. Bleomycin-exposed rodent models do not exhibit sustained fibrosis or airway remodeling. Unlike mice, ferrets have human-like distribution of MUC5B expressing cell types and natively express the risk-conferring variant that induces high MUC5B expression in humans. We hypothesized that ferrets would consequently exhibit aberrant repair to propagate fibrosis similar to human IPF.

Methods

Bleomycin (5U/kg) or saline-control was micro-sprayed intratracheally then wild-type ferrets were evaluated through 22 wks. Clinical phenotype was assessed with lung function. Fibrosis was assessed with µCT imaging and comparative histology with Ashcroft scoring. Airway remodeling was assessed with histology and quantitative immunofluorescence.

Results

Bleomycin ferrets exhibited sustained restrictive physiology including decreased inspiratory capacity, decreased compliance, and shifted Pressure-Volume loops through 22 wks. Volumetric µCT analysis revealed increased opacification of the lung bleomycin-ferrets. Histology showed extensive fibrotic injury that matured over time and MUC5B-positive cystic structures in the distal lung suggestive of honeycombing. Bleomycin ferrets had increased proportion of small airways that were double-positive for CCSP and alpha-tubulin compared to controls, indicating an aberrant 'proximalization' repair phenotype. Notably, this aberrant repair was associated with extent of fibrotic injury at the airway level.

Conclusions

Bleomycin-exposed ferrets exhibit sustained fibrosis through 22 wks and have pathologic features of IPF not found in rodents. Ferrets exhibited proximalization of the distal airways and other pathologic features characteristic of human IPF. MUC5B expression through native cell types may play a key role in promoting airway remodeling and lung injury in IPF.

Mapping the genetic architecture of idiopathic pulmonary fibrosis: Meta-analysis and epidemiological evidence of case-control studies

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a rare and devastating fibrotic lung disorder with unknown etiology. Although it is believed that genetic component is an important risk factor for IPF, a comprehensive understanding of its genetic landscape is lacking. Hence, we aimed to highlight the susceptibility genes and pathways implicated in IPF pathogenesis through a two-staged systematic literature search of genetic association studies on IPF, followed by meta-analysis and pathway enrichment analysis.

METHODS

This study was performed based on PRISMA guidelines (PROSPERO, registration number: CRD42022297970). The first search was performed (using PubMed and Web of Science) retrieving a total of 5642 articles, of which 52 were eligible for inclusion in the first stage. The second search was performed (using PubMed, Web of Science and Scopus) for ten polymorphisms, identified from the first search, with 2 or more studies. Finally, seven polymorphisms, [rs35705950/MUC5B, rs2736100/TERT, rs2609255/FAM13A, rs2076295/DSP, rs12610495/DPP9, rs111521887/TOLLIP and rs1800470/TGF-β1] qualified for meta-analyses. The epidemiological credibility was evaluated using Venice criteria.

RESULTS

From the systematic review, 222 polymorphisms in 118 genes showed a significant association with IPF susceptibility. Meta-analyses findings revealed significant association of rs35705950/T [OR = 3.92(3.26-4.57)], rs2609255/G [OR = 1.50(1.18-1.82)], rs2076295/G [OR = 1.19(0.82-1.756)], rs12610495/G [OR = 1.28(1.12-1.44)], rs2736100/C [OR = 0.68(0.54-0.82), rs111521887/G [OR = 1.34(1.06-1.61)] and suggestive evidence for rs1800470/T [OR = 1.08(0.82-1.34)] with IPF susceptibility. Four polymorphisms- rs35705950/MUC5B, rs2736100/TERT, rs2076295/DSP and rs111521887/TOLLIP, exhibited substantial epidemiological evidence supporting their association with IPF risk. Gene ontology and pathway enrichment analysis performed on IPF risk-associated genes identified a critical role of genes in mucin production, immune response and inflammation, host defence, cell-cell adhesion and telomere maintenance.

CONCLUSIONS

Our findings present the most prominent IPF-associated genetic risk variants involved in alveolar epithelial injuries (MUC5B, TERT, FAM13A, DSP, DPP9) and epithelial-mesenchymal transition (TOLLIP, TGF-β1), providing genetic and biological insights into IPF pathogenesis. However, further experimental research and human studies with larger sample sizes, diverse ethnic representation, and rigorous design are warranted.

High sucrose intake exacerbates airway inflammation through pathogenic Th2 and Th17 response in ovalbumin (OVA)-induced acute allergic asthma in C57BL/6 mice

Asthma is an inflammatory disease characterized by chronic inflammation in lung tissues and excessive mucus production. High-fat diets have long been assumed to be a potential risk factor for asthma. However, to date, very few direct evidence indicating the involvement of high sucrose intake (HSI) in asthma progression exists. In this study, we investigate the effect of HSI on ovalbumin (OVA)-sensitized allergic asthma mice. We observed that HSI increased the expression of inflammatory genes (IL-1β, IL-6, TNF-α) in adipose tissues and led to reactive oxygen species generation in the liver and lung. In addition, HSI accelerated the TLR4/NF-κB signaling pathway leading to MMP9 activation, which promotes the chemokines and TGF-β secretion in the lungs of OVA-sensitized allergic asthma mice. More importantly, HSI significantly promoted the pathogenic Th2 and Th17 responses. The increase of IL-17A secretion by HSI increased the expression of chemokines (MCP-1, CXCL1, CXCL5, CXCL8). It resulted in eosinophil and mast cell infiltration in the lung and trachea. We also demonstrated that HSI increased mucus hypersecretion, which was validated by increased main mucin protein (MUC5AC) secreted in the lungs. Our findings suggest that HSI exacerbates the development of Th2/Th17-predominant asthma by upregulating the TLR4-mediated NF-κB pathway, leading to excessive MMP9 production.

Exploring noncoding variants in genetic diseases: from detection to functional insights

Previous studies on genetic diseases predominantly focused on protein-coding variations, overlooking the vast noncoding regions in the human genome. The development of high-throughput sequencing technologies and functional genomics tools has enabled the systematic identification of functional noncoding variants. These variants can impact gene expression, regulation, and chromatin conformation, thereby contributing to disease pathogenesis. Understanding the mechanisms that underlie the impact of noncoding variants on genetic diseases is indispensable for the development of precisely targeted therapies and the implementation of personalized medicine strategies. The intricacies of noncoding regions introduce a multitude of challenges and research opportunities. In this review, we introduce a spectrum of noncoding variants involved in genetic diseases, along with research strategies and advanced technologies for their precise identification and in-depth understanding of the complexity of the noncoding genome. We will delve into the research challenges and propose potential solutions for unraveling the genetic basis of rare and complex diseases.

Characterization of transient and progressive pulmonary fibrosis by spatially correlated phase contrast microCT, classical histopathology and atomic force microscopy

Pulmonary fibrosis (PF) is a severe and progressive condition in which the lung becomes scarred over time resulting in pulmonary function impairment. Classical histopathology remains an important tool for micro-structural tissue assessment in the diagnosis of PF. A novel workflow based on spatial correlated propagation-based phase-contrast micro computed tomography (PBI-microCT), atomic force microscopy (AFM) and histopathology was developed and applied to two different preclinical mouse models of PF - the commonly used and well characterized Bleomycin-induced PF and a novel mouse model for progressive PF caused by conditional Nedd4-2 KO. The aim was to integrate structural and mechanical features from hallmarks of fibrotic lung tissue remodeling. PBI-microCT was used to assess structural alteration in whole fixed and paraffin embedded lungs, allowing for identification of fibrotic foci within the 3D context of the entire organ and facilitating targeted microtome sectioning of planes of interest for subsequent histopathology. Subsequently, these sections of interest were subjected to AFM to assess changes in the local tissue stiffness of previously identified structures of interest. 3D whole organ analysis showed clear morphological differences in 3D tissue porosity between transient and progressive PF and control lungs. By integrating the results obtained from targeted AFM analysis, it was possible to discriminate between the Bleomycin model and the novel conditional Nedd4-2 KO model using agglomerative cluster analysis. As our workflow for 3D spatial correlation of PBI, targeted histopathology and subsequent AFM is tailored around the standard procedure of formalin-fixed paraffin-embedded (FFPE) tissue specimens, it may be a powerful tool for the comprehensive tissue assessment beyond the scope of PF and preclinical research.

Thin-Section CT in the Categorization and Management of Pulmonary Fibrosis including Recently Defined Progressive Pulmonary Fibrosis

While idiopathic pulmonary fibrosis (IPF) is the most common type of fibrotic lung disease, there are numerous other causes of pulmonary fibrosis that are often characterized by lung injury and inflammation. Although often gradually progressive and responsive to immune modulation, some cases may progress rapidly with reduced survival rates (similar to IPF) and with imaging features that overlap with IPF, including usual interstitial pneumonia (UIP)-pattern disease characterized by peripheral and basilar predominant reticulation, honeycombing, and traction bronchiectasis or bronchiolectasis. Recently, the term progressive pulmonary fibrosis has been used to describe non-IPF lung disease that over the course of a year demonstrates clinical, physiologic, and/or radiologic progression and may be treated with antifibrotic therapy. As such, appropriate categorization of the patient with fibrosis has implications for therapy and prognosis and may be facilitated by considering the following categories: (a) radiologic UIP pattern and IPF diagnosis, (b) radiologic UIP pattern and non-IPF diagnosis, and (c) radiologic non-UIP pattern and non-IPF diagnosis. By noting increasing fibrosis, the radiologist contributes to the selection of patients in which therapy with antifibrotics can improve survival. As the radiologist may be first to identify developing fibrosis and overall progression, this article reviews imaging features of pulmonary fibrosis and their significance in non-IPF-pattern fibrosis, progressive pulmonary fibrosis, and implications for therapy. Keywords: Idiopathic Pulmonary Fibrosis, Progressive Pulmonary Fibrosis, Thin-Section CT, Usual Interstitial Pneumonia © RSNA, 2024.

Integrating mechanical cues with engineered platforms to explore cardiopulmonary development and disease

Mechanical forces provide critical biological signals to cells during healthy and aberrant organ development as well as during disease processes in adults. Within the cardiopulmonary system, mechanical forces, such as shear, compressive, and tensile forces, act across various length scales, and dysregulated forces are often a leading cause of disease initiation and progression such as in bronchopulmonary dysplasia and cardiomyopathies. Engineered in vitro models have supported studies of mechanical forces in a number of tissue and disease-specific contexts, thus enabling new mechanistic insights into cardiopulmonary development and disease. This review first provides fundamental examples where mechanical forces operate at multiple length scales to ensure precise lung and heart function. Next, we survey recent engineering platforms and tools that have provided new means to probe and modulate mechanical forces across in vitro and in vivo settings. Finally, the potential for interdisciplinary collaborations to inform novel therapeutic approaches for a number of cardiopulmonary diseases are discussed.

ADRB2 inhibition combined with antioxidant treatment alleviates lung fibrosis by attenuating TGFβ/SMAD signaling in lung fibroblasts

Idiopathic pulmonary fibrosis is a progressive and fatal interstitial lung disease with a poor prognosis and limited therapeutic options, which is characterized by aberrant myofibroblast activation and pathological remodeling of the extracellular matrix, while the mechanism remains elusive. In the present investigation, we observed a reduction in ADRB2 expression within both IPF and bleomycin-induced fibrotic lung samples, as well as in fibroblasts treated with TGF-β1. ADRB2 inhibition blunted bleomycin-induced lung fibrosis. Blockage of the ADRB2 suppressed proliferation, migration, and invasion and attenuated TGF-β1-induced fibroblast activation. Conversely, the enhancement of ADRB2 expression or functionality proved capable of inducing fibroblast-to-myofibroblast differentiation. Subsequent mechanistic investigation revealed that inhibition of ADRB2 suppressed the activation of SMAD2/3 in lung fibroblasts and increased phos-SMAD2/3 proteasome degradation, and vice versa. Finally, ADRB2 inhibition combined with antioxidants showed increased efficacy in the therapy of bleomycin-induced lung fibrosis. In short, these data indicate that ADRB2 is involved in lung fibroblast differentiation, and targeting ADRB2 could emerge as a promising and innovative therapeutic approach for pulmonary fibrosis.

Molecular and Genetic Biomarkers in Idiopathic Pulmonary Fibrosis: Where Are We Now?

Idiopathic pulmonary fibrosis (IPF) represents a chronic progressive fibrotic interstitial lung disease of unknown cause with an ominous prognosis. It remains an unprecedent clinical challenge due to its delayed diagnosis and unpredictable clinical course. The need for accurate diagnostic, prognostic and predisposition biomarkers in everyday clinical practice becomes more necessary than ever to ensure prompt diagnoses and early treatment. The identification of such blood biomarkers may also unravel novel drug targets against IPF development and progression. So far, the role of diverse blood biomarkers, implicated in various pathogenetic pathways, such as in fibrogenesis (S100A4), extracellular matrix remodelling (YKL-40, MMP-7, ICAM-1, LOXL2, periostin), chemotaxis (CCL-18, IL-8), epithelial cell injury (KL-6, SP-A, SP-D), autophagy and unfolded protein response has been investigated in IPF with various results. Moreover, the recent progress in genetics in IPF allows for a better understanding of the underlying disease mechanisms. So far, the causative mutations in pulmonary fibrosis include mutations in telomere-related genes and in surfactant-related genes, markers that could act as predisposition biomarkers in IPF. The aim of this review is to provide a comprehensive overview from the bench to bedside of current knowledge and recent insights on biomarkers in IPF, and to suggest future directions for research. Large-scale studies are still needed to confirm the exact role of these biomarkers.

Exploring the role and mechanism of Astragalus membranaceus and radix paeoniae rubra in idiopathic pulmonary fibrosis through network pharmacology and experimental validation

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrotic disease with an unclear etiology and no effective treatment. This study aims to elucidate the pathogenic mechanism networks involving multiple targets and pathways in IPF. Extracts and metabolites of Astragalus membranaceus (AM) and Radix paeoniae rubra (RPR), two well-known traditional Chinese medicines, have demonstrated therapeutic effects on IPF. However, the underlying mechanisms of AM and RPR remain unclear. Utilizing network pharmacology analysis, differentially expressed genes (DEGs) associated with IPF were obtained from the GEO database. Targets of AM and RPR were identified using the TCM Systems Pharmacology Database and Analysis Platform and SwissTargetPrediction. A protein-protein interaction (PPI) network was subsequently constructed and analyzed using the STRING database and Cytoscape software. Gene ontology enrichment analysis and kyoto encyclopedia of genes and genomes analysis were conducted using Metascape. Additionally, a component-target-pathway network and a Sankey diagram were employed to identify the main active components, and molecular docking was performed between these components and proteins encoded by key targets. Finally, in vivo studies were conducted based on network pharmacology. A total of 117 common targets between DEGs of IPF and drug targets were identified and included in the PPI network, in which AKT1, MAPK3, HSP90AA1, VEGFA, CASP3, JUN, HIF1A, CCND1, PTGS2, and MDM2 were predicted as key targets. These 117 targets were enriched in the PI3K-AKT pathway, HIF-1 signaling pathway, apoptosis, and microRNAs in cancer. Astragaloside III, (R)-Isomucronulatol, Astragaloside I, Paeoniflorin, and β-sitosterol were selected as the main active components. Docking scores ranged from - 4.7 to - 10.7 kcal/mol, indicating a strong binding affinity between the main active compounds and key targets. In vivo studies have indeed shown that AM and RPR can alleviate the pathological lung fibrotic damage caused by bleomycin treatment. The treatment with AM and RPR resulted in a reduction of mRNA levels for key targets AKT1, HSP90AA1, CASP3, MAPK3, and VEGFA. Additionally, the protein expression levels of AKT1, HSP90AA1, and VEGFA were also reduced. These results support the therapeutic potential of AM and RPR in ameliorating pulmonary fibrosis and provide insight into the molecular mechanisms involved in their therapeutic effects.

Properties of Pleural Mesothelial Cells in Idiopathic Pulmonary Fibrosis and Cryptogenic Organizing Pneumonia

BACKGROUND

Profibrotic properties of pleural mesothelial cells may play an important role in the fibrosis activity in idiopathic pulmonary fibrosis (IPF). The purpose of this study was to compare the expression of pleural mesothelial cell markers in IPF and cryptogenic organizing pneumonia (COP), with an assumption that increased expression implies increase in fibrosis.

METHODS

Twenty IPF lung samples were stained by immunohistochemistry for the pleural mesothelial cell markers: leucine rich repeat neuronal 4 (LRRN4), uroplakin 3B, CC-chemokine ligand 18, and laminin-5. Nine COP lung samples were used as controls. A semi-quantitative analysis was performed to compare markers expression in IPF and COP.

RESULTS

LRRN4 expression was found in epithelial lining cells along the honeycombing and fibroblastic foci in IPF, but not in the fibrotic interstitial lesion and airspace filling fibrous tufts in COP. We found a significant decrease in baseline forced vital capacity when LRRN4 expression was increased in honeycombing epithelial cells and fibroblastic foci.

CONCLUSION

LRRN4 expression patterns in IPF are distinct from those in COP. Our findings suggest that mesothelial cell profibrotic property may be an important player in IPF pathogenesis and may be a clue in the irreversibility of fibrosis in IPF.

The Presence of T Allele (rs35705950) of the MUC5B Gene Predicts Lower Baseline Forced Vital Capacity and Its Subsequent Decline in Patients with Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) is an exposure-related interstitial lung disease with two phenotypes-fibrotic and non-fibrotic. Genetic predisposition is an important factor in the disease pathogenesis and fibrosis development. Several genes are supposed to be associated with the fibrosing cascade in the lungs. One of the best-recognized and most prevalent is the common MUC5B gene promoter region polymorphism variant rs35705950. The aim of our study was to establish the frequency of the minor allele of the MUC5B gene in the population of patients with HP and to find the relationship between the MUC5B promoter region polymorphism and the development of lung fibrosis, the severity of the disease course, and the response to the treatment in patients with HP. Eighty-six consecutive patients with HP were tested for the genetic variant rs35705950 of the MUC-5B gene. Demographic, radiological, and functional parameters were collected. The relationship between the presence of the T allele and lung fibrosis, pulmonary function test parameters, and the treatment response were analyzed. The minor allele frequency in the study group was 17%, with the distribution of the genotypes GG in 69.8% of subjects and GT/TT in 30.2%. Patients with the GT/TT phenotype had significantly lower baseline forced vital capacity (FVC) and significantly more frequently had a decline in FVC with time. The prevalence of lung fibrosis in high-resolution computed tomography (HRCT) was not significantly increased in GT/TT variant carriers compared to GG ones. The patients with the T allele tended to respond worse to immunomodulatory treatment and more frequently received antifibrotic drugs. In conclusions: The frequency of MUC5B polymorphism in HP patients is high. The T allele may indicate a worse disease course, worse immunomodulatory treatment response, and earlier need for antifibrotic treatment.

Betulin and Crinum asiaticum L. bulbs extract attenuate pulmonary fibrosis by down regulating pro-fibrotic and pro-inflammatory cytokines in bleomycin-induced fibrosis mice model

Background

Pulmonary fibrosis (PF) is a lung disease characterized by scaring of lung tissue that impairs lung functions. The estimated survival time of patients with pulmonary fibrosis is 3-5 years. Bleomycin (BLM) is used clinically in the treatment of Hodgkin lymphoma and testicular germ-cell tumors. Bleomycin's mechanism of action is the inhibition of DNA and protein synthesis. This happens when leukocytes induce the release of cytokines and chemokines which increase the pro-fibrotic and pro-inflammatory cytokines such as IL-6, TNF-alpha, IL-13, IL-1β and transforming growth factor-beta 1 (TGF-β). Crinum asiaticum L. bulbs (CAE) are widely found in parts of Africa, Asia and Indian Ocean Island. It is also prevalent in southern part of Ghana and traditionally used by the indigenes to treat upper respiratory tract infections, and for wound healing. Betulin (BET) is found in the bulbs of Crinum asiaticum L. but widely isolated from the external bark of birches and sycamore trees. Betulin as a lupine type triterpenes has been researched for their pharmacological and biological activities including anticancer, anti-inflammatory, antimicrobial activities and anti-liver fibrosis effects.Aim of the study: The aim was to study the anti-pulmonary fibrosis effect of Crinum asiaticum L. bulbs extract and betulin in bleomycin-induced pulmonary fibrosis in mice.

Materials and method

There was a single oropharyngeal administration of bleomycin (80 mg/kg) in mice followed by the treatment of CAE and BET after 48 h of exposure to BLM.

Results

There was increased survival rate in CAE and BET treatment groups compared to the BLM induced group. There was a marked decreased in the levels of hydroxyproline, collagen I and III in the CAE and BET treatment groups compared to BLM-treated group. The treatment groups of CAE and BET significantly down regulated the levels of pro-fibrotic and pro-inflammatory cytokines concentrations such as TGF-β1, MMP9, IL-6, IL-1β and TNF-alpha compared to an increased in the BLM treated groups. The histological findings of the lungs suggested the curative effects of CAE and BET following BLM induced pulmonary fibrosis in mice, the study showed improved lung functions with wide focal area of viable alveolar spaces and few collagen fibers deposition on lungs of treatment groups.

Conclusion

CAE and BET attenuated pulmonary fibrosis by down regulating pro-fibrotic and pro-inflammatory cytokines as well as improving lung function. This could be a lead in drug discovery where compounds with anti-fibrotic effects could be developed for the treatment of lung injury.

The causal relationship between gastro-oesophageal reflux disease and idiopathic pulmonary fibrosis: a bidirectional two-sample Mendelian randomisation study

BACKGROUND

Gastro-oesophageal reflux disease (GORD) is associated with idiopathic pulmonary fibrosis (IPF) in observational studies. It is not known if this association arises because GORD causes IPF or because IPF causes GORD, or because of confounding by factors, such as smoking, associated with both GORD and IPF. We used bidirectional Mendelian randomisation (MR), where genetic variants are used as instrumental variables to address issues of confounding and reverse causation, to examine how, if at all, GORD and IPF are causally related.

METHODS

A bidirectional two-sample MR was performed to estimate the causal effect of GORD on IPF risk and of IPF on GORD risk, using genetic data from the largest GORD (78 707 cases and 288 734 controls) and IPF (4125 cases and 20 464 controls) genome-wide association meta-analyses currently available.

RESULTS

GORD increased the risk of IPF, with an OR of 1.6 (95% CI 1.04-2.49; p=0.032). There was no evidence of a causal effect of IPF on the risk of GORD, with an OR of 0.999 (95% CI 0.997-1.000; p=0.245).

CONCLUSIONS

We found that GORD increases the risk of IPF, but found no evidence that IPF increases the risk of GORD. GORD should be considered in future studies of IPF risk and interest in it as a potential therapeutic target should be renewed. The mechanisms underlying the effect of GORD on IPF should also be investigated.

Monitoring small airway dysfunction in connective tissue disease-related interstitial lung disease: a retrospective and prospective study

BACKGROUND

Small airway dysfunction (SAD), a hallmark of early lung function abnormality, is a major component of several chronic respiratory disorders. The role of SAD in patients with connective tissue disease-related interstitial lung disease (CTD-ILD) has not been explored.

METHODS

We conducted a two-parts (retrospective and prospective) study to collect pulmonary function tests from CTD-ILD patients. SAD was defined as at least two of the three measures (MMEF, FEF 50%, and FEF 75%) must be 65% of predicted values. Spearman correlation coefficient was used to evaluate association between SAD and other pulmonary function parameters. Mixed effects regression modeling analysis was used to assess response to treatment.

RESULTS

CTD-ILD patients with SAD and without SAD were compared in this study. In the retrospective study, pulmonary function tests (PFTs) from 491 CTD-ILD patients were evaluated, SAD were identified in 233 (47.5%). CTD-ILD patients with SAD were less smokers (17.6% vs. 27.9%, p = 0.007) and more females (74.3% vs. 64.0%, p = 0.015) than those without SAD. CTD-ILD patients with SAD had lower vital capacity (% predicted FVC, 70.4 ± 18.3 vs. 80.0 ± 20.9, p < 0.001) and lower diffusion capacity (% predicted DLCO, 58.8 ± 19.7 vs. 63.8 ± 22.1, p = 0.011) than those without SAD. Among 87 CTD-ILD patients prospectively enrolled, significant improvement in % predicted FVC was observed at 12-months follow-up (6.37 ± 1.53, p < 0.001 in patients with SAD; 5.13 ± 1.53, p = 0.002 in patients without SAD), but not in diffusion capacity and SAD parameters.

CONCLUSION

In our cohort, about half of CTD-ILD patients have SAD, which is less frequent in smokers and more common in female patients. CTD-ILD patients with SAD have worse pulmonary function compared to those without SAD. Improvement of FVC but no improvement of SAD was observed in CTD-ILD patients after treatment.

T cells in idiopathic pulmonary fibrosis: crucial but controversial

Idiopathic pulmonary fibrosis (IPF) has been extensively studied in recent decades due to its rising incidence and high mortality. Despite an abundance of research, the mechanisms, immune-associated mechanisms, of IPF are poorly understood. While defining immunopathogenic mechanisms as the primary pathogenesis is controversial, recent studies have verified the contribution of the immune system to the fibrotic progression of IPF. Extensive evidence has shown the potential role of T cells in fibrotic progression. In this review, we emphasize the features of T cells in IPF and highlight the controversial roles of different subtypes of T cells or even two distinct effects of one type of T-cell in diverse settings, and multiple chemokines and cell products are discussed. Furthermore, we discuss the potential development of treatments targeting the immune molecules of T cells and the feasibility of immune therapies for IPF in clinical practice.

Effects of Pirfenidone on Idiopathic Pulmonary Fibrosis Progression and Safety: Results of Multicenter Prospective Observational Study

The aim of this study was to determine the effectiveness of pirfenidone in patients with idiopathic pulmonary fibrosis (IPF) seen in clinical practice. Fifty-five adults with IPF were enrolled in this multicenter, open-label, non-randomized, non-controlled, interventional clinical study. All patients received pirfenidone 2403 mg/day (three 267 mg capsules three times daily) for 26 weeks. After 26 weeks of treatment, the mean change in absolute forced vital capacity (FVC) was 128.8 mL (95% confidence interval [CI] -26.8, 284.4) and the mean change in relative predicted FVC was -0.10% (95% CI -3.18, 2.99). Stable disease (defined as improvement of ≥0% or a decline of <10% to 0% of the corresponding FVC value) was observed in most patients (relative FVC, 90.9%; absolute FVC, 83.6%). There was no statistically significant change in the mean high-resolution computed tomography fibrosis score or lung opacity score at week 26 compared with baseline. Treatment-emergent adverse events were reported in 80% of patients during the treatment period; most of them were mild or moderate in severity. No serious pirfenidone-related adverse events were observed during the study period. Pirfenidone was generally safe and effective for controlling functional decline and stabilizing disease in patients with IPF encountered in clinical practice in Russia.

What role for asbestos in idiopathic pulmonary fibrosis? Findings from the IPF job exposures case-control study

BACKGROUND

Asbestos has been hypothesised as the cause of the recent global increase in the incidence of 'idiopathic' pulmonary fibrosis (IPF). Establishing this has important diagnostic and therapeutic implications. The association between occupational asbestos exposure and IPF, and interaction with a common (minor allele frequency of 9% in European populations) genetic variant associated with IPF, MUC5B rs35705950, is unknown.

METHODS

Multicentre, incident case-control study. Cases (n=494) were men diagnosed with IPF at 21 UK hospitals. Controls (n=466) were age-matched men who attended a hospital clinic in the same period. Asbestos exposure was assessed at interview using a validated job exposure matrix and a source-receptor model. The primary outcome was the association between asbestos exposure and IPF, estimated using logistic regression adjusted for age, smoking and centre. Interaction with MUC5B rs35705950 was investigated using a genetic dominant model.

RESULTS

327 (66%) cases and 293 (63%) controls ever had a high or medium asbestos exposure risk job; 8% of both cases and controls had cumulative exposure estimates ≥25 fibre ml⁻¹ years. Occupational asbestos exposure was not associated with IPF, adjusted OR 1.1 (95% CI 0.8 to 1.4; p=0.6) and there was no gene-environment interaction (p=0.3). Ever smoking was associated with IPF, OR 1.4 (95% CI 1 to 1.9; p=0.04) and interacted with occupational asbestos exposure, OR 1.9 (95% CI 1 to 3.6; p=0.04). In a further non-specified analysis, when stratifying for genotype there was significant interaction between smoking and work in an exposed job (p<0.01) for carriers of the minor allele of MUC5B rs35705950.

CONCLUSION

Occupational asbestos exposure alone, or through interaction with MUC5B rs35705950 genotype, was not associated with IPF. Exposure to asbestos and smoking interact to increase IPF risk in carriers of a common genetic variant, the minor allele of MUC5B rs35705950.

TRIAL REGISTRATION NUMBER

NCT03211507.

Recent advances in the treatment of systemic sclerosis associated interstitial lung disease

Connective tissue diseases (CTDs) are a heterogenous group of systemic inflammatory disorders. The development of connective tissue disease-associated interstitial lung disease (CTD-ILD) is a key complication associated with significant morbidity and mortality. The aim of this review is to explore the pathogenesis of CTD-ILD and summarize the recent evidence from clinical trials for novel treatment options, including the role of antifibrotics and immunomodulatory therapies with a focus on systemic sclerosis associated ILD. Further clinical trials are ongoing to explore combination therapies and more targeted therapeutic options. Clinicians remain faced with the difficult challenge of appropriately selecting patients who will benefit from the available therapies and timing the start of therapy at the most suitable part of the disease course.

Immune Responses at Host Barriers and Their Importance in Systemic Autoimmune Diseases

Host barriers such as the skin, the lung mucosa, the intestinal mucosa and the oral cavity are crucial at preventing contact with potential threats and are populated by a diverse population of innate and adaptive immune cells. Alterations in antigen recognition driven by genetic and environmental factors can lead to autoimmune systemic diseases such rheumatoid arthritis, systemic lupus erythematosus and food allergy. Here we review how different immune cells residing at epithelial barriers, host-derived signals and environmental signals are involved in the initiation and progression of autoimmune responses in these diseases. We discuss how regulation of innate responses at these barriers and the influence of environmental factors such as the microbiota can affect the susceptibility to develop local and systemic autoimmune responses particularly in the cases of food allergy, systemic lupus erythematosus and rheumatoid arthritis. Induction of pathogenic autoreactive immune responses at host barriers in these diseases can contribute to the initiation and progression of their pathogenesis.

MUC5B promoter variant rs35705950, rare but significant susceptibility locus in rheumatoid arthritis-interstitial lung disease with usual interstitial pneumonia in Asian populations

BACKGROUND

MUC5B variant rs35705950 is the common and most significant risk variant for rheumatoid arthritis-interstitial lung disease (RA-ILD) in Western populations. However, little is known about its significant association with RA-ILD in Asian populations. We here investigate the association of rs35705950 with Korean patients with RA-ILD.

METHODS

In this cross-sectional study, we genotyped rs35705950 in 2444 patients with RA. Among them, 683 patients with RA who have chest CT were divided into RA-ILD and RA-noILD. RA-ILD was classified as usual interstitial pneumonia (UIP) and other than UIP. The associations of rs35705950 with RA-ILD and its subtype were analysed using multivariable regression adjusted for age at RA diagnosis. Meta-analysis of a previously reported Japanese dataset and Korean dataset obtained for this study was conducted.

RESULTS

The minor allele (T) frequency of rs35705950 was 0.37%, 1.43% and 2.38% in 2444 patients with RA, 105 patients with RA-ILD and 63 patients with UIP, respectively. Genotypic association of rs35705950 with RA-ILD was insignificant (OR 2.49, 95% CI 0.64 to 9.69, p=0.187), but showed significant association with UIP (OR 4.90, 95% CI 1.23 to 19.59, p=0.024) compared with RA-noILD. In meta-analysis (123 UIP and 878 RA-noILD) combining our data with previously reported Japanese data, this variant was found to be significantly associated with UIP (OR 3.51, 95% CI 1.19 to 10.37, p=0.023).

CONCLUSION

MUC5B variant rs35705950 is a rare but significant risk factor for Asian patients with RA-ILD with UIP, suggesting a sharing of the genetic background between Asian and Western populations.

Interstitial lung disease in rheumatoid arthritis: A multidisciplinary problem in rheumatology and pulmonology

Rheumatoid arthritis (RA) is an immune-mediated rheumatic disease (IMRDs) characterized by chronic erosive arthritis and systemic damage to internal organs, leading to early disability and reduced life expectancy in patients. A particularly important place among the systemic manifestations of RA is occupied by interstitial lung diseases (ILD) – the most severe form of pulmonary pathology in RA, defined as RA-ILD, which is pathogenetically associated with risk factors (smoking, etc.) and autoimmune mechanisms underlying RA. RA-ILD is a subtype of RA characterized by a severe course and a poor prognosis и неблагоприятным прогнозом. The review presents new data regarding risk factors and biomarkers for RA-ILD; modern diagnostic capabilities based on the use of functional lung tests, high-resolution computed tomography, ultrasound examination of the lungs. Particular attention is paid to the efficacy and safety of pharmacotherapy, including methotrexate, biologics, JAK inhibitors, and antifibrotic therapy. An algorithm for the pharmacotherapy of RA-ILD has been proposed.

The Genetic and Epigenetic Footprint in Idiopathic Pulmonary Fibrosis and Familial Pulmonary Fibrosis: A State-of-the-Art Review

Idiopathic pulmonary fibrosis (IPF) is a rare disease of the lung with a largely unknown etiology and a poor prognosis. Intriguingly, forms of familial pulmonary fibrosis (FPF) have long been known and linked to specific genetic mutations. There is little evidence of the possible role of genetics in the etiology of sporadic IPF. We carried out a non-systematic, narrative literature review aimed at describing the main known genetic and epigenetic mechanisms that are involved in the pathogenesis and prognosis of IPF and FPF. In this review, we highlighted the mutations in classical genes associated with FPF, including those encoding for telomerases (TERT, TERC, PARN, RTEL1), which are also found in about 10-20% of cases of sporadic IPF. In addition to the Mendelian forms, mutations in the genes encoding for the surfactant proteins (SFTPC, SFTPA1, SFTPA2, ABCA3) and polymorphisms of genes for the mucin MUC5B and the Toll-interacting protein TOLLIP are other pathways favoring the fibrogenesis that have been thoroughly explored. Moreover, great attention has been paid to the main epigenetic alterations (DNA methylation, histone modification and non-coding RNA gene silencing) that are emerging to play a role in fibrogenesis. Finally, a gaze on the shared mechanisms between cancer and fibrogenesis, and future perspectives on the genetics of pulmonary fibrosis have been analyzed.

The Idiopathic Pulmonary Fibrosis-Associated Single Nucleotide Polymorphism RS35705950 Is Transcribed in a MUC5B Promoter Associated Long Non-Coding RNA (AC061979.1)

LncRNAs are involved in regulatory processes in the human genome, including gene expression. The rs35705950 SNP, previously associated with IPF, overlaps with the recently annotated lncRNA AC061979.1, a 1712 nucleotide transcript located within the MUC5B promoter at chromosome 11p15.5. To document the expression pattern of the transcript, we processed 3.9 TBases of publicly available RNA-SEQ data across 27 independent studies involving lung airway epithelial cells. Epithelial lung cells showed expression of this putative pancRNA. The findings were independently validated in cell lines and primary cells. The rs35705950 is found within a conserved region (from fish to primates) within the expressed sequence indicating functional importance. These results implicate the rs35705950-containing AC061979.1 pancRNA as a novel component of the MUC5B expression control minicircuitry.

Prevalence and Mechanisms of Mucus Accumulation in COVID-19 Lung Disease

Rationale: The incidence and sites of mucus accumulation and molecular regulation of mucin gene expression in coronavirus (COVID-19) lung disease have not been reported. Objectives: To characterize the incidence of mucus accumulation and the mechanisms mediating mucin hypersecretion in COVID-19 lung disease. Methods: Airway mucus and mucins were evaluated in COVID-19 autopsy lungs by Alcian blue and periodic acid-Schiff staining, immunohistochemical staining, RNA in situ hybridization, and spatial transcriptional profiling. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected human bronchial epithelial (HBE) cultures were used to investigate mechanisms of SARS-CoV-2-induced mucin expression and synthesis and test candidate countermeasures. Measurements and Main Results: MUC5B and variably MUC5AC RNA concentrations were increased throughout all airway regions of COVID-19 autopsy lungs, notably in the subacute/chronic disease phase after SARS-CoV-2 clearance. In the distal lung, MUC5B-dominated mucus plugging was observed in 90% of subjects with COVID-19 in both morphologically identified bronchioles and microcysts, and MUC5B accumulated in damaged alveolar spaces. SARS-CoV-2-infected HBE cultures exhibited peak titers 3 days after inoculation, whereas induction of MUC5B/MUC5AC peaked 7-14 days after inoculation. SARS-CoV-2 infection of HBE cultures induced expression of epidermal growth factor receptor (EGFR) ligands and inflammatory cytokines (e.g., IL-1α/β) associated with mucin gene regulation. Inhibiting EGFR/IL-1R pathways or administration of dexamethasone reduced SARS-CoV-2-induced mucin expression. Conclusions: SARS-CoV-2 infection is associated with a high prevalence of distal airspace mucus accumulation and increased MUC5B expression in COVID-19 autopsy lungs. HBE culture studies identified roles for EGFR and IL-1R signaling in mucin gene regulation after SARS-CoV-2 infection. These data suggest that time-sensitive mucolytic agents, specific pathway inhibitors, or corticosteroid administration may be therapeutic for COVID-19 lung disease.

A MUC5B Gene Polymorphism, rs35705950-T, Confers Protective Effects Against COVID-19 Hospitalization but Not Severe Disease or Mortality

Rationale: A common MUC5B gene polymorphism, rs35705950-T, is associated with idiopathic pulmonary fibrosis (IPF), but its role in severe acute respiratory syndrome coronavirus 2 infection and disease severity is unclear. Objectives: To assess whether rs35705950-T confers differential risk for clinical outcomes associated with coronavirus disease (COVID-19) infection among participants in the Million Veteran Program (MVP). Methods: The MUC5B rs35705950-T allele was directly genotyped among MVP participants; clinical events and comorbidities were extracted from the electronic health records. Associations between the incidence or severity of COVID-19 and rs35705950-T were analyzed within each ancestry group in the MVP followed by transancestry meta-analysis. Replication and joint meta-analysis were conducted using summary statistics from the COVID-19 Host Genetics Initiative (HGI). Sensitivity analyses with adjustment for additional covariates (body mass index, Charlson comorbidity index, smoking, asbestosis, rheumatoid arthritis with interstitial lung disease, and IPF) and associations with post-COVID-19 pneumonia were performed in MVP subjects. Measurements and Main Results: The rs35705950-T allele was associated with fewer COVID-19 hospitalizations in transancestry meta-analyses within the MVP (N_cases = 4,325; N_controls = 507,640; OR = 0.89 [0.82-0.97]; P = 6.86 × 10^-3) and joint meta-analyses with the HGI (N_cases = 13,320; N_controls = 1,508,841; OR, 0.90 [0.86-0.95]; P = 8.99 × 10^-5). The rs35705950-T allele was not associated with reduced COVID-19 positivity in transancestry meta-analysis within the MVP (N_cases = 19,168/N_controls = 492,854; OR, 0.98 [0.95-1.01]; P = 0.06) but was nominally significant (P < 0.05) in the joint meta-analysis with the HGI (N_cases = 44,820; N_controls = 1,775,827; OR, 0.97 [0.95-1.00]; P = 0.03). Associations were not observed with severe outcomes or mortality. Among individuals of European ancestry in the MVP, rs35705950-T was associated with fewer post-COVID-19 pneumonia events (OR, 0.82 [0.72-0.93]; P = 0.001). Conclusions: The MUC5B variant rs35705950-T may confer protection in COVID-19 hospitalizations.

Mucins MUC5AC and MUC5B Are Variably Packaged in the Same and in Separate Secretory Granules

Rationale: MUC5AC (mucin 5AC, oligomeric gel-forming) and MUC5B (mucin 5B, oligomeric gel-forming) are the predominant secreted polymeric mucins in mammalian airways. They contribute differently to the pathogenesis of various muco-obstructive and interstitial lung diseases, and their genes are separately regulated, but whether they are packaged together or in separate secretory granules is not known. Objectives: To determine the packaging of MUC5AC and MUC5B within individual secretory granules in mouse and human airways under varying conditions of inflammation and along the proximal-distal axis. Methods: Lung tissue was obtained from mice stimulated to upregulate mucin production by the cytokines IL-1β and IL-13 or by porcine pancreatic elastase. Human lung tissue was obtained from donated normal lungs, biopsy samples of transplanted lungs, and explanted lungs from subjects with chronic obstructive pulmonary disease. MUC5AC and MUC5B were labeled with antibodies from different animal species or, in mice only, by transgenic chimeric mucin-fluorescent proteins and imaged using widefield deconvolution or Airyscan fluorescence microscopy. Measurements and Main Results: In both mouse and human airways, most secretory granules contained both mucins interdigitating within the granules. Smaller numbers of granules contained MUC5B alone, and even fewer contained MUC5AC alone. Conclusions: MUC5AC and MUC5B are variably stored both in the same and in separate secretory granules of both mice and humans. The high fraction of granules containing both mucins under a variety of conditions makes it unlikely that their secretion can be differentially controlled as a therapeutic strategy. This work also advances knowledge of the packaging of mucins within secretory granules to understand mechanisms of epithelial stress in the pathogenesis of chronic lung diseases.

Dysregulated Cell-Cell Communication Characterizes Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of older adults characterized by fibrotic replacement of functional gas exchange units in the lung. The strongest risk factor for IPF is a genetic variantin the promoter region of the gel-forming mucin, MUC5B. To better understand how the MUC5B variant influences development of fibrosis, we used the NicheNet R package and leveraged publicly available single-cell RNA sequencing data to identify and evaluate how epithelia participating in gas exchange are influenced by ligands expressed in control, MUC5B variant, and fibrotic environments. We observed that loss of type-I alveolar epithelia (AECI) characterizes the single-cell RNA transcriptome in fibrotic lung and validated the pattern of AECI loss using single nuclear RNA sequencing. Examining AECI transcriptomes, we found enrichment of transcriptional signatures for IL6 and AREG, which we have previously shown to mediate aberrant epithelial fluidization in IPF and murine bleomycin models. Moreover, we found that the protease ADAM17, which is upstream of IL6 trans-signaling, was enriched in control MUC5B variant donors. We used immunofluorescence to validate a role for enhanced expression of ADAM17 among MUC5B variants, suggesting involvement in IPF pathogenesis and maintenance.

Small airway dysfunction in idiopathic pulmonary fibrosis

It is generally accepted that the pathophysiology of idiopathic pulmonary fibrosis (IPF) can be attributed to impaired lung interstitium and alveoli, while airway involvement has rarely been reported. In the present study, we aimed to investigate the actual occurrence of IPF comorbid small airway dysfunction (SAD) and its impact on survival. Data from inpatients diagnosed with IPF at Shanghai Pulmonary Hospital (Shanghai, China) from 2011 to 2021 were retrospectively collected and analyzed. Lung function parameters were used to assess SAD. A total of 243 IPF patients were included in this retrospective study, and 84 cases (84/243, 34.57%) were diagnosed with SAD. The lung histopathology showed that all 48 cases undergoing lung transplantation presented various degrees of airway lesions, of which 18 patients (18/48, 37.5%) diagnosed with SAD before lung transplantation had a higher proportion of airway distortion and obliteration. The possible risk factors associated with IPF comorbid SAD were smoking, male, younger age, and high CT fibrosis and emphysema scores. By univariate Fine-Grey regression, the hazard ratio (HR) of IPF comorbid SAD was 1.725 (95% CI 1.071, 2.777, p < 0.05). After adjusting the CTPF model and GAP model, the value of HR was 1.714 (95% CI 1.043, 2.816, p < 0.05) and 1.731 (95% CI 1.074, 2.788, p < 0.05), respectively. These findings suggested that IPF comorbid SAD was an independent risk factor for the mortality of IPF patients.

The significance of elevated tumor markers among patients with interstitial lung diseases

The clinical implication of using serum tumor markers in patients with interstitial lung disease (ILD) is inconclusive. In this retrospective study, we analyzed the data of 1176 subjects (294 with ILDs and 882 healthy controls). Eligible patients were who had at least one or more available tumor marker results [carbohydrate antigen (CA) 19-9, CA 125, and carcinoembryonic antigen (CEA)] with no evidence of malignancies or other benign diseases that could be related to the increasing concentration of the values. The healthy controls selected from a health screening program were also screened for the presence of active cancer, and matched at a ratio of 1:3 with age and sex. The proportion of patients with abnormal values in the ILD group (121, idiopathic pulmonary fibrosis (IPF); 173, non-IPF-ILDs) was higher than in the matched control group (CEA, 21.5% vs. 5.5%; CA 19-9, 27.9% vs. 4.0%; CA 125, 36.4% vs. 2.0%). In the multivariable analysis, higher CEA levels were associated with shorter survival after adjusting for age, sex, lung function, and ILD subtypes (hazard ratio: 2.323, 95% confidence interval: 1.271–4.248, P = 0.006). In subgroup analysis, CEA remained a prognostic factor in patients with non-IPF-ILDs, but not in those with IPF.

Differential modulation of lung aquaporins among other pathophysiological markers in acute (Cl2 gas) and chronic (carbon nanoparticles, cigarette smoke) respiratory toxicity mouse models

Inhaled toxic chemicals and particulates are known to disrupt lung homeostasis causing pulmonary toxicity and tissue injury. However, biomarkers of such exposures and their underlying mechanisms are poorly understood, especially for emerging toxicants such as engineered nanoparticles and chemical threat agents such as chlorine gas (Cl₂). Aquaporins (AQPs), commonly referred to as water channels, are known to play roles in lung homeostasis and pathophysiology. However, little is known on their regulation in toxicant-induced lung injuries. Here, we compared four lung toxicity models namely, acute chemical exposure (Cl₂)-, chronic particulate exposure (carbon nanotubes/CNT)-, chronic chemical exposure (cigarette smoke extract/CSE)-, and a chronic co-exposure (CNT + CSE)- model, for modulation of lung aquaporins (AQPs 1, 3, 4, and 5) in relation to other pathophysiological endpoints. These included markers of compromised state of lung mucosal lining [mucin 5b (MUC5B) and surfactant protein A (SP-A)] and lung-blood barrier [protein content in bronchoalveolar lavage (BAL) fluid and, cell tight junction proteins occludin and zona-occludens]. The results showed toxicity model-specific regulation of AQPs measured in terms of mRNA abundance. A differential upregulation was observed for AQP1 in acute Cl₂ exposure model (14.71-fold; p = 0.002) and AQP3 in chronic CNT exposure model (3.83-fold; p = 0.044). In contrast, AQP4 was downregulated in chronic CSE model whereas AQP5 showed no significant change in any of the models. SP-A and MUC5B expression showed a decreasing pattern across all toxicity models except the acute Cl₂ toxicity model, which showed a highly significant upregulation of MUC5B (25.95-fold; p = 0.003). This was consistent with other significant pathophysiological changes observed in this acute model, particularly a compromised lung epithelial-endothelial barrier indicated by significantly increased protein infiltration and expression of tight junction proteins, and more severe histopathological (structural and immunological) changes. To our knowledge, this is the first report on lung AQPs as molecular targets of the study toxicants. The differentially regulated AQPs, AQP1 in acute Cl₂ exposure versus AQP3 in chronic CNT nanoparticle exposure, in conjunction with the corresponding differentially impacted pathophysiological endpoints (particularly MUC5B) could potentially serve as predictive markers of toxicant type-specific pulmonary injury and as candidates for future investigation for clinical intervention.

Why is UIP peripheral?

INTRODUCTION

The radiology pattern associated with IPF is called UIP. It is unique because unlike any other form of fibrosis it is peripheral in its distribution. We investigated the peripheral nature of UIP and why it was a key feature of IPF the deadliest of the ILDS.

AREAS COVERED

It is not enough to say that UIP is peripheral but instead as scientists we must ask ourselves why it is peripheral. This review dives into the published hypothesis that includes vascular insult, tensile forces, microaspiration, and inflammation and looks at the pros and cons for each argument, and ultimately comes to its own conclusion. PubMed searches using the below keywords were used to identify papers that described pathogenesis of IPF with regard to a particular theory.

EXPERT OPINION

In this paper, we will review four ideas that support why UIP is peripheral and propose the most likely explanation given what is currently known about the pathophysiology of IPF.

Human pluripotent stem cell-derived macrophages and macrophage-derived exosomes: therapeutic potential in pulmonary fibrosis

Pulmonary fibrosis (PF) is a fatal chronic disease characterized by accumulation of extracellular matrix and thickening of the alveolar wall, ultimately leading to respiratory failure. PF is thought to be initiated by the dysfunction and aberrant activation of a variety of cell types in the lung. In particular, several studies have demonstrated that macrophages play a pivotal role in the development and progression of PF through secretion of inflammatory cytokines, growth factors, and chemokines, suggesting that they could be an alternative therapeutic source as well as therapeutic target for PF. In this review, we describe the characteristics, functions, and origins of subsets of macrophages involved in PF and summarize current data on the generation and therapeutic application of macrophages derived from pluripotent stem cells for the treatment of fibrotic diseases. Additionally, we discuss the use of macrophage-derived exosomes to repair fibrotic lung tissue.

Muc5b plays a role in the development of inflammation and fibrosis in hypersensitivity pneumonitis induced by Saccharopolyspora rectivirgula

Previously we have shown that a gain-of-function MUC5B promoter variant (rs35705950) is the strongest risk factor for the development of idiopathic pulmonary fibrosis. We have also found that Muc5b overexpression reduces mucociliary clearance in mice, potentially leading to recurrent injury to the bronchoalveolar epithelia. Hypersensitivity pneumonitis (HP) is induced by inhalation of numerous causative antigens that may be affected by mucociliary clearance. We conducted this study to determine the role of Muc5b in a mouse model of HP induced by Saccharopolyspora rectivirgula (SR) antigen. We used Muc5b-deficient and wild-type (WT) mice to determine whether Muc5b plays a role in inflammation and fibrosis at 3 and 6 wk in an SR model of HP. We measured cell concentrations and MUC5B expression in whole lung lavage (WLL) and quantified fibrosis using hydroxyproline assay and second harmonic generation. Muc5b expression in WLL fluid was significantly increased in SR-exposed WT mice compared with saline controls. WT mice challenged with SR developed more inflammation and lung fibrosis at 6 wk compared with 3 wk postexposure. Moreover, we found that 6 wk following challenge with SR, Muc5b-deficient mice had less lung inflammation and less lung fibrosis than Muc5b WT mice. Furthermore, Muc5b-deficient mice had significantly lower concentrations of TGF-β1 in the WLL compared with Muc5b WT mice at 6 wk of exposure. Muc5b appears to play a role in fibrosis in the animal model of HP and this may have implications for HP in humans.

Aberrant Multiciliogenesis in Idiopathic Pulmonary Fibrosis

We previously identified a novel molecular subtype of idiopathic pulmonary fibrosis (IPF) defined by increased expression of cilium-associated genes, airway mucin gene MUC5B, and KRT5 marker of basal cell airway progenitors. Here we show the association of MUC5B and cilia gene expression in human IPF airway epithelial cells, providing further rationale for examining the role of cilium genes in the pathogenesis of IPF. We demonstrate increased multiciliogenesis and changes in motile cilia structure of multiciliated cells both in IPF and bleomycin lung fibrosis models. Importantly, conditional deletion of a cilium gene, Ift88 (intraflagellar transport 88), in Krt5 basal cells reduces Krt5 pod formation and lung fibrosis, whereas no changes are observed in Ift88 conditional deletion in club cell progenitors. Our findings indicate that aberrant injury-activated primary ciliogenesis and Hedgehog signaling may play a causative role in Krt5 pod formation, which leads to aberrant multiciliogenesis and lung fibrosis. This implies that modulating cilium gene expression in Krt5 cell progenitors is a potential therapeutic target for IPF.

Research Progress in the Molecular Mechanisms, Therapeutic Targets, and Drug Development of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease. Recent studies have identified the key role of crosstalk between dysregulated epithelial cells, mesenchymal, immune, and endothelial cells in IPF. In addition, genetic mutations and environmental factors (e.g., smoking) have also been associated with the development of IPF. With the recent development of sequencing technology, epigenetics, as an intermediate link between gene expression and environmental impacts, has also been reported to be implicated in pulmonary fibrosis. Although the etiology of IPF is unknown, many novel therapeutic targets and agents have emerged from clinical trials for IPF treatment in the past years, and the successful launch of pirfenidone and nintedanib has demonstrated the promising future of anti-IPF therapy. Therefore, we aimed to gain an in-depth understanding of the underlying molecular mechanisms and pathogenic factors of IPF, which would be helpful for the diagnosis of IPF, the development of anti-fibrotic drugs, and improving the prognosis of patients with IPF. In this study, we summarized the pathogenic mechanism, therapeutic targets and clinical trials from the perspective of multiple cell types, gene mutations, epigenetic and environmental factors.

La fibrose pulmonaire idiopathique

La fibrose pulmonaire idiopathique (FPI) est une maladie pulmonaire chronique, évolutive et mortelle dont l’origine est inconnue. Elle se caractérise par une cicatrisation aberrante de l’épithélium alvéolaire aboutissant à une accumulation de matrice extracellulaire (MEC). Les foyers fibroblastiques, constitués de fibroblastes et de myofibroblastes, sont responsables de la production excessive de MEC. Les deux seules molécules thérapeutiques disponibles sur le marché permettent seulement de ralentir l’évolution de la maladie. Dans cette revue, nous présentons les mécanismes impliqués dans la progression de la maladie, ses traitements et les modèles d’étude.

Corticotropin releasing hormone as an identifier of bronchiolitis obliterans syndrome

Lung transplantion (LTx) recipients have low long-term survival and a high incidence of bronchiolitis obliterans syndrome (BOS), an inflammation of the small airways in chronic rejection of a lung allograft. There is great clinical need for a minimally invasive biomarker of BOS. Here, 644 different proteins were analyzed to detect biomarkers that distinguish BOS grade 0 from grades 1–3. The plasma of 46 double lung transplant patients was analyzed for proteins using a high-component, multiplex immunoassay that enables analysis of protein biomarkers. Proximity Extension Assay (PEA) consists of antibody probe pairs which bind to targets. The resulting polymerase chain reaction (PCR) reporter sequence can be quantified by real-time PCR. Samples were collected at baseline and 1-year post transplantation. Enzyme-linked immunosorbent assay (ELISA) was used to validate the findings of the PEA analysis across both time points and microarray datasets from other lung transplantation centers demonstrated the same findings. Significant decreases in the plasma protein levels of CRH, FERC2, IL-20RA, TNFB, and IGSF3 and an increase in MMP-9 and CTSL1 were seen in patients who developed BOS compared to those who did not. In this study, CRH is presented as a novel potential biomarker in the progression of disease because of its decreased levels in patients across all BOS grades. Additionally, biomarkers involving the remodeling of the extracellular matrix (ECM), such as MMP-9 and CTSL1, were increased in BOS patients.

The MUC5B Promoter Polymorphism is Not Associated With Non-ILD Chronic Respiratory Diseases or Post-transplant Outcome

The MUC5B promoter polymorphism (rs35705950) has been associated with interstitial lung disease (ILD) and with prolonged pre-transplant survival in idiopathic pulmonary fibrosis (IPF), but no information is available regarding its prevalence in other respiratory diseases and its influence on post-transplant outcome. We included the Leuven lung transplantation cohort between 1991 and 2015 (n = 801). We assessed the minor allele frequency (MAF) of the MUC5B variant in the entire study cohort and investigated the influence of recipient MUC5B promoter polymorphism on post-transplant outcome in patients who were transplanted after 2004. MUC5B was successfully genotyped in 746 patients. The MAF was significantly higher in ILD (17.6%) compared to chronic obstructive pulmonary disease (COPD)/emphysema (9.3%), cystic fibrosis (CF)/bronchiectasis (BRECT) (7.5%) and pulmonary hypertension (PHT) (7.4%) (p < 0.001). No association was observed between rs35705950 and chronic lung allograft dysfunction (CLAD)/graft loss in the ILD population [CLAD: HR 1.37 95% CI (0.70-2.68); graft loss: HR 1.02 95% CI (0.55-1.89)], nor the entire study cohort [CLAD: HR 0.96 95% CI (0.69-1.34); graft loss: HR 0.97 95% CI (0.70-1.35)]. The MUC5B promoter polymorphism is a very specific predictive factor for the presence of pulmonary fibrosis as it is only associated with pulmonary fibrosis and not with other chronic respiratory diseases. While the MUC5B promoter variant is associated with better pre-transplant survival among IPF patients, recipient MUC5B promoter variant does not play a role in post-transplant outcome.

Targeting Histone Deacetylases in Idiopathic Pulmonary Fibrosis: A Future Therapeutic Option

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited therapeutic options, and there is a huge unmet need for new therapies. A growing body of evidence suggests that the histone deacetylase (HDAC) family of transcriptional corepressors has emerged as crucial mediators of IPF pathogenesis. HDACs deacetylate histones and result in chromatin condensation and epigenetic repression of gene transcription. HDACs also catalyse the deacetylation of many non-histone proteins, including transcription factors, thus also leading to changes in the transcriptome and cellular signalling. Increased HDAC expression is associated with cell proliferation, cell growth and anti-apoptosis and is, thus, a salient feature of many cancers. In IPF, induction and abnormal upregulation of Class I and Class II HDAC enzymes in myofibroblast foci, as well as aberrant bronchiolar epithelium, is an eminent observation, whereas type-II alveolar epithelial cells (AECII) of IPF lungs indicate a significant depletion of many HDACs. We thus suggest that the significant imbalance of HDAC activity in IPF lungs, with a “cancer-like” increase in fibroblastic and bronchial cells versus a lack in AECII, promotes and perpetuates fibrosis. This review focuses on the mechanisms by which Class I and Class II HDACs mediate fibrogenesis and on the mechanisms by which various HDAC inhibitors reverse the deregulated epigenetic responses in IPF, supporting HDAC inhibition as promising IPF therapy.

In vivo models of mucin biosynthesis and function

The secreted mucus layer that lines and protects epithelial cells is conserved across diverse species. While the exact composition of this protective layer varies between organisms, certain elements are conserved, including proteins that are heavily decorated with N-acetylgalactosamine-based sugars linked to serines or threonines (O-linked glycosylation). These heavily O-glycosylated proteins, known as mucins, exist in many forms and are able to form hydrated gel-like structures that coat epithelial surfaces. In vivo studies in diverse organisms have highlighted the importance of both the mucin proteins as well as their constituent O-glycans in the protection and health of internal epithelia. Here, we summarize in vivo approaches that have shed light on the synthesis and function of these essential components of mucus.

Mammalian Neuraminidases in Immune-Mediated Diseases: Mucins and Beyond

Mammalian neuraminidases (NEUs), also known as sialidases, are enzymes that cleave off the terminal neuraminic, or sialic, acid resides from the carbohydrate moieties of glycolipids and glycoproteins. A rapidly growing body of literature indicates that in addition to their metabolic functions, NEUs also regulate the activity of their glycoprotein targets. The simple post-translational modification of NEU protein targets-removal of the highly electronegative sialic acid-affects protein folding, alters protein interactions with their ligands, and exposes or covers proteolytic sites. Through such effects, NEUs regulate the downstream processes in which their glycoprotein targets participate. A major target of desialylation by NEUs are mucins (MUCs), and such post-translational modification contributes to regulation of disease processes. In this review, we focus on the regulatory roles of NEU-modified MUCs as coordinators of disease pathogenesis in fibrotic, inflammatory, infectious, and autoimmune diseases. Special attention is placed on the most abundant and best studied NEU1, and its recently discovered important target, mucin-1 (MUC1). The role of the NEU1 - MUC1 axis in disease pathogenesis is discussed, along with regulatory contributions from other MUCs and other pathophysiologically important NEU targets.

Emerging Roles of Airway Epithelial Cells in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal disease with incompletely understood aetiology and limited treatment options. Traditionally, IPF was believed to be mainly caused by repetitive injuries to the alveolar epithelium. Several recent lines of evidence, however, suggest that IPF equally involves an aberrant airway epithelial response, which contributes significantly to disease development and progression. In this review, based on recent clinical, high-resolution imaging, genetic, and single-cell RNA sequencing data, we summarize alterations in airway structure, function, and cell type composition in IPF. We furthermore give a comprehensive overview on the genetic and mechanistic evidence pointing towards an essential role of airway epithelial cells in IPF pathogenesis and describe potentially implicated aberrant epithelial signalling pathways and regulation mechanisms in this context. The collected evidence argues for the investigation of possible therapeutic avenues targeting these processes, which thus represent important future directions of research.

Will Host Genetics Affect the Response to SARS-CoV-2 Vaccines? Historical Precedents

Recent progress in genomics and bioinformatics technologies have allowed for the emergence of immunogenomics field. This intersection of immunology and genetics has broadened our understanding of how the immune system responds to infection and vaccination. While the immunogenetic basis of the huge clinical variability in response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is currently being extensively studied, the host genetic determinants of SARS-CoV-2 vaccines remain largely unknown. Previous reports evidenced that vaccines may not protect all populations or individuals equally, due to multiple host- and vaccine-specific factors. Several studies on vaccine response to measles, rubella, hepatitis B, smallpox, and influenza highlighted the contribution of genetic mutations or polymorphisms in modulating the innate and adaptive immunity following vaccination. Specifically, genetic variants in genes encoding virus receptors, antigen presentation, cytokine production, or related to immune cells activation and differentiation could influence how an individual responds to vaccination. Although such knowledge could be utilized to generate personalized vaccine strategies to optimize the vaccine response, studies in this filed are still scarce. Here, we briefly summarize the scientific literature related to the immunogenetic determinants of vaccine-induced immunity, highlighting the possible role of host genetics in response to SARS-CoV-2 vaccines as well.

Management of BMI Is a Potential New Approach for the Prevention of Idiopathic Pulmonary Fibrosis

Aims: Current idiopathic pulmonary fibrosis (IPF) therapies usually show a poor outcome or treatment efficacy. The search for new risk factors has significant implications in preventing, delaying, and treating IPF. The association between obesity and the risk of IPF is not clear. This study aimed to investigate the role of different obesity types in IPF risk, which provides the possibility of weight loss as a new approach for IPF prevention.

Methods: We conducted a two-sample Mendelian randomization (MR) analysis to assess the causal effect of obesity on IPF risk. We collected summary data of genetically determined obesity-related traits, including body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) from large-scale consortia (the sample size ranging from 232,101 to 681,275), and genetic association with IPF from one of the largest meta-analyses including 2,668 cases. A total of 35–469 single nucleotide polymorphisms were selected as instrumental variables for obesity-related traits. We further performed multivariable MR to estimate the independent effect of BMI and WC on the risk of IPF.

Results: Increased BMI and WC were associated with higher risk of IPF [odds ratio (OR) = 1.51, 95% confidence interval (CI) (1.22–1.87), p = 1.27 × 10^–4, and OR = 1.71, 95% CI (1.08–2.72), p = 2.33 × 10^–2, respectively]. Similar results for the BMI and WC were obtained in the replicated analysis. Subsequently, only the result for BMI survived following the multiple testing correction and showed good consistency with the weighted median estimator. Sensitivity analyses indicated that there was no heterogeneity or horizontal pleiotropy for MR estimations. Further multivariable MR suggested that the BMI showed the same direction and similar magnitude with that in the univariable MR analysis. There was little evidence to support the causal role of WHR on the risk of IPF in this study.

Conclusion: Genetically determined BMI demonstrates a causal risk for IPF, which offers a novel insight into probing potential mechanisms. Meanwhile, these results also suggest that weight loss may be beneficial to IPF prevention.