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Background/aim: Cigarette smoke has been shown to induce a phenotype in humans known as "acquired cystic fibrosis". This occurs because the cystic fibrosis transmembrane conductance regulator (CFTR) functions are impaired systemically due to the deleterious effects of smoke components. Elucidation of cigarette smoke effects on the tracheal epithelium is important. The aim of this study was to develop an ex vivo sheep tracheal model to investigate tracheal ion function. In this model, the epithelial sodium channel (ENaC) is inhibited after exposure to cigarette smoke extract (CSE) as a proof of principle., Materials and Methods: Tracheas were isolated from healthy sheep and the tracheal epithelium was surgically excised. Tissues were mounted in Ussing chambers and the short circuit current (I sc ) was measured after incubation with 5% CSE in PBS or PBS alone for 30 min. The function of ENaC was investigated by the addition of amiloride (10 -5 M) apically. Western blot analysis was performed to assess differences in ENaC quantity after CSE exposure. Some specimens were stained with H&E for detection of histological alterations., Results: The amiloride effect on normal epithelium led to a significant decrease in I sc [ΔI=33±5.92 μA/cm 2 ; p<0.001 versus control experiments (ΔI=1.44±0.71 μA/cm 2 )]. After incubation with CSE, ENaC I sc was significantly reduced (ΔI=14.80±1.96 μA/cm 2 ; p<0.001). No differences in αENaC expression were observed between CSE-exposed and normal tracheal epithelium. Histological images post CSE incubation revealed decreases in the height of the epithelium, with basal cell hyperplasia and loss of ciliated cells., Conclusion: Reduced ENaC inhibition by amiloride after CSE incubation could be due to alterations in the tracheal epithelium., (Copyright © 2024, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Emerging evidence has reported that acute lung injury (ALI), characterized by inflammation and oxidative stress in airway epithelium, is regulated by programmed cell death. Ferroptosis, a regulated form of cell death spurred by uncontrolled lipid peroxidation, has been proven to implicate various diseases. Inhibiting ferroptosis represents a feasible strategy for ALI through the suppression of lipid peroxidation, while the mechanism remains to be further elucidated. Here, we identified Sequestosome 1 (SQSTM1) as a negative regulator of airway epithelium ferroptosis during ALI. SQSTM1 knockdown cells manifested higher sensitivity to ferroptosis. Mechanistically, SQSTM1 was found to directly interact with vitamin D receptor (VDR) through its nuclear receptor (NR) box motif, facilitating its nuclear translocation and initiating autophagy at the transcriptional level. To further validate these findings, an in vivo preventive model utilizing spermidine, a proven inducer of SQSTM1 was established. The results consistently demonstrated that spermidine supplementation significantly induced SQSTM1 and ameliorated ALI by mitigating airway epithelial ferroptosis. Notably, these effects were abrogated in the absence of SQSTM1. Taken together, this study identified SQSTM1 as a negative regulator of airway epithelium ferroptosis in a VDR-mediated autophagy manner, making it a potential therapeutic target for the treatment of ALI., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Lung cancer is the most common cause of cancer death worldwide and poses an immediate health threat. Despite decades of basic and clinical research, the 5-year survival rate for lung cancer patients is less than 10%.The most important drawbacks in efficient treatment of lung cancer are delayed diagnosis and absence of effective screening. Detection and study of precancerous lesions of the bronchial mucosa might be one of the turning points in understanding of neoplastic transformation. Therefore, it would be the most effective prevention and early treatment modality. We report a case of high-grade intraepithelial neoplasia of the bronchial mucosa in which a neoplastic growth in the lumen of intrinsic segment in the upper lobe of the left lung was detected on electronic bronchoscopy, and biopsy confirmed squamous papillary hyperplasia with high-grade intraepithelial neoplasia., Case Presentation: A 74-year-old male was admitted to the hospital due to a mass lesion in his left lung. After admission, computed tomography scan of the chest showed an intraluminal mass in the intrinsic segment of the upper lobe of the left lung and an enlarged left hilum., Conclusions: High-grade intraepithelial neoplasia of the bronchial mucosa is rare in the respiratory system. We report a case that can provide useful information for early diagnosis and treatment of the disease., (© 2024. The Author(s).)

Background: The interplay between airway epithelium and macrophages plays a pivotal role in Chronic Obstructive Pulmonary Disease (COPD) pathogenesis. Exosomes, which transport miRNA cargo, have emerged as novel mediators of intercellular communication. MicroRNA-125a-5p (miR-125a-5p) has been implicated in macrophage polarization.This study aims to investigate the role of exosomal miR-125a-5p in the dysfunctional epithelium-macrophage cross-talk in cigarette smoke (CS)-induced COPD., Methods: In cell models, THP-1 monocytic cells were differentiated into macrophages (M0). Human bronchial epithelial cells treated with CS extract (CSE) were co-cultured with M0. Exosomes were isolated from culture media using commercial kits and characterized using nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). Exosomes labeled with PKH26 red fluorescent cell linker kits were incubated with macrophages. Luciferase reporter assay was used to confirm the target gene of miR-125a-5p. In mouse experiments, inhibiting miR-125a-5p was utilized to examine its role in macrophage polarization. Furthermore, the underlying mechanism was explored., Results: In vitro results indicated that CSE treatment led to upregulation of miR-125a-5p in HBE cells, and exosomes contained miR-125a-5p. PKH26-labeled exosomes were internalized by macrophages. Co-culture experiments between bronchial epithelial cells and miR-125a-5p mimic resulted in significant increase in M1 macrophage markers (TNF-α, iNOS-2, IL-1β) and decrease in M2 markers (IL-10 and Arg-1). In COPD mouse models, miR-125a-5p inhibitor reduced levels of TNF-α, IL-1β, and IL-6. Luciferase assays revealed that miR-125a-5p inhibitors enhanced the relative luciferase activity of IL1RN. Mechanistic experiments demonstrated that HBE-derived exosomes transfected with miR-125a-5p mimics promoted upregulation of MyD88, TRAF6, p65, iNOS-2, and downregulation of Arg-1., Conclusion: This study suggests that exosomal miR-125a-5p may act as a mediator in the cross-talk between airway epithelium and macrophage polarization in COPD. Exosomal miR-125a-5p targeting IL1RN may promote M1 macrophage polarization via the MyD88/NF-κB pathway., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Epithelial cells play a crucial role in asthma, contributing to chronic inflammation and airway hyperresponsiveness. m6A modification, which involves key proteins such as the demethylase fat mass and obesity-associated protein (FTO), is crucial in the regulation of various diseases, including asthma. However, the role of FTO in epithelial cells and the development of asthma remains unclear. In this study, we investigated the demethylase activity of FTO using a small-molecule inhibitor FB23 in epithelial cells and allergic inflammation in vivo and in vitro. We examined the FTO-regulated transcriptome-wide m6A profiling by methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA-seq under FB23 treatment and allergic inflammation conditions. Immunofluorescence staining was performed to assess the tissue-specific expression of FTO in asthmatic bronchial mucosa. We demonstrated that FB23 alleviated allergic inflammation in IL-4/IL-13-treated epithelial cells and house dust mite (HDM)-induced allergic airway inflammation mouse model. The demethylase activity of FTO contributed to the regulation of TNF-α signaling via NF-κB and epithelial-mesenchymal transition-related pathways under allergic inflammation conditions in epithelial cells. FTO was expressed in epithelial, submucosal gland, and smooth muscle cells in human bronchial mucosa. In conclusion, FB23-induced inhibition of FTO alleviates allergic inflammation in epithelial cells and HDM-induced mice, potentially through diverse cellular processes and epithelial-mesenchymal transition signaling pathways, suggesting that FTO is a potential therapeutic target in asthma management., (© 2024 Federation of American Societies for Experimental Biology.)

Background: Respiratory epithelial adenomatoid hamartoma (REAH) is a benign lesion commonly occurring in the nasal cavity and sinuses. It is often accompanied by nasal polyps (NP). While the histological features of these two conditions have been studied, there is limited knowledge about their differences in the underlying immunopathology., Methods: Nasal tissue specimens were collected from 8 patients with concurrent REAH and NP and 10 controls. The expression levels of inflammatory cytokines, tight junctions (TJ), and epithelial-mesenchymal transition (EMT)-related factors in the tissues were analyzed. The mRNA expression of the aforementioned factors was measured using qRT-PCR, while the expression of TJ and EMT-related proteins was analyzed through Western blotting and immunohistochemistry., Results: Compared to the control group, levels of inflammatory cytokines (IFN-α, IL-5, IL-17A, IL-31, IL-33, and TNF-α) and EMT-related factors (α-SMA, COL1A1, MMP9, TGF-β1, and Vimentin) were significantly increased in both REAH and NP tissues. Conversely, E-Cadherin and TJ-related factors (Claudin-4 and Occludin) significantly decreased. When comparing REAH with NP, it was observed that the expression of IL-4, IL-5, and IL-33 was lower in REAH, while TNF-ɑ; was higher. Regarding TJ-related factors, the expression of Occludin was lower in REAH. Furthermore, in terms of EMT-related factors, except for E-Cadherin, the expressions of ɑ-SMA, COL1A1, CTGF, MMP9, TGF-β11, and Vimentin were higher in REAH., Conclusion: REAH and NP exhibit different immunopathological mechanisms. NP demonstrates a more severe inflammatory response, whereas REAH is characterized by a more pronounced TJ and EMT breakdown than NP.

The non-ciliated bronchiolar cell, also referred to as "club cell", serves as a significant multifunctional component of the airway epithelium. While the club cell is a prominent epithelial type found in rodents, it is restricted to the bronchioles in humans. Despite these differences, the club cell's importance remains undisputed in both species due to its multifunctionality as a regulatory cell in lung inflammation and a stem cell in lung epithelial regeneration. The objective of this review is to examine different aspects of club cell morphology and physiology in the lung epithelium, under both normal and pathological conditions, to provide a comprehensive understanding of its importance in the respiratory system., (©The Author(s) 2024. Open Access. This article is licensed under a Creative Commons CC-BY International License.)

The interactions between immune cells and epithelial cells influence the progression of many respiratory diseases, such as chronic obstructive pulmonary disease (COPD). In vitro models allow for the examination of cells in controlled environments. However, these models lack the complex 3D architecture and vast multicellular interactions between the lung resident cells and infiltrating immune cells that can mediate cellular response to insults. In this study, three complementary microphysiological systems are presented to delineate the effects of cigarette smoke and respiratory disease on the lung epithelium. First, the Transwell system allows the co-culture of pulmonary immune and epithelial cells to evaluate cellular and monolayer phenotypic changes in response to cigarette smoke exposure. Next, the human and mouse precision-cut lung slices system provides a physiologically relevant model to study the effects of chronic insults like cigarette smoke with the dissection of specific interaction of immune cell subtypes within the structurally complex tissue environment. Finally, the lung-on-a-chip model provides an adaptable system for live imaging of polarized epithelial tissues that mimic the in vivo environment of the airways. Using a combination of these models, a complementary approach is provided to better address the intricate mechanisms of lung disease., (© 2023 The Authors. Advanced Biology published by Wiley‐VCH GmbH.)

Fine particulate matter (PM 2.5 ) can damage airway epithelial barriers. The anion transport system plays a crucial role in airway epithelial barriers. However, the detrimental effect and mechanism of PM 2.5 on the anion transport system are still unclear. In this study, airway epithelial cells and ovalbumin (OVA)-induced asthmatic mice were used. In transwell model, the adenosine triphosphate (ATP)-induced transepithelial anion short-circuit current (I sc ) and airway surface liquid (ASL) significantly decreased after PM 2.5 exposure. In addition, PM 2.5 exposure decreased the expression levels of P2Y2R, CFTR and cytoplasmic free-calcium, but ATP can increase the expressions of these proteins. PM 2.5 exposure increased the levels of Th2-related cytokines of bronchoalveolar lavage fluid, lung inflammation, collagen deposition and hyperplasisa of goblet cells. Interestingly, the administration of ATP showed an inhibitory effect on lung inflammation induced by PM 2.5 . Together, our study reveals that PM 2.5 impairs the ATP-induced transepithelial anion I sc through downregulating P2Y2R/CFTR pathway, and this process may participate in aggravating airway hyperresponsiveness and airway inflammation. These findings may provide important insights on PM 2.5 -mediated airway epithelial injury., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

The production of nanoparticles has recently surged due to their varied applications in the biomedical, pharmaceutical, textile, and electronic sectors. However, this rapid increase in nanoparticle manufacturing has raised concerns about environmental pollution, particularly its potential adverse effects on human health. Among the various concerns, inhalation exposure to nanoparticles poses significant risks, especially affecting the respiratory system. Airway epithelial cells play a crucial role as the primary defense against inhaled particulate matter and pathogens. Studies have shown that nanoparticles can disrupt the airway epithelial barrier, triggering inflammatory responses, generating reactive oxygen species, and compromising cell viability. However, our understanding of how different types of nanoparticles specifically impact the airway epithelial barrier remains limited. Both in vitro cell culture and in vivo murine models are commonly utilized to investigate nanoparticle-induced cellular responses and barrier dysfunction. This review discusses the methodologies frequently employed to assess nanoparticle toxicity and barrier disruption. Furthermore, we analyze and compare the distinct effects of various nanoparticle types on the airway epithelial barrier. By elucidating the diverse responses elicited by different nanoparticles, we aim to provide insights that can guide future research endeavors in assessing and mitigating the potential risks associated with nanoparticle exposure.

Virus-induced cell death is a key contributor to COVID-19 pathology. Cell death induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is well studied in myeloid cells but less in its primary host cell type, angiotensin-converting enzyme 2 (ACE2)-expressing human airway epithelia (HAE). SARS-CoV-2 induces apoptosis, necroptosis, and pyroptosis in HAE organotypic cultures. Single-cell and limiting-dilution analysis revealed that necroptosis is the primary cell death event in infected cells, whereas uninfected bystanders undergo apoptosis, and pyroptosis occurs later during infection. Mechanistically, necroptosis is induced by viral Z-RNA binding to Z-DNA-binding protein 1 (ZBP1) in HAE and lung tissues from patients with COVID-19. The Delta (B.1.617.2) variant, which causes more severe disease than Omicron (B1.1.529) in humans, is associated with orders of magnitude-greater Z-RNA/ZBP1 interactions, necroptosis, and disease severity in animal models. Thus, Delta induces robust ZBP1-mediated necroptosis and more disease severity.

Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Patients with cystic fibrosis (CF) experience severe lung disease, including persistent infections, inflammation, and irreversible fibrotic remodeling of the airways. Although therapy with transmembrane conductance regulator (CFTR) protein modulators reached optimal results in terms of CFTR rescue, lung transplant remains the best line of care for patients in an advanced stage of CF. Indeed, chronic inflammation and tissue remodeling still represent stumbling blocks during treatment, and underlying mechanisms are still unclear. Nowadays, animal models are not able to fully replicate clinical features of the human disease and the conventional in vitro models lack a stromal compartment undergoing fibrotic remodeling. To address this gap, we show the development of a 3D full-thickness model of CF with a human bronchial epithelium differentiated on a connective airway tissue. We demonstrated that the epithelial cells not only underwent mucociliary differentiation but also migrated in the connective tissue and formed gland-like structures. The presence of the connective tissue stimulated the pro-inflammatory behaviour of the epithelium, which activated the fibroblasts embedded into their own extracellular matrix (ECM). By varying the composition of the model with CF epithelial cells and a CF or healthy connective tissue, it was possible to replicate different moments of CF disease, as demonstrated by the differences in the transcriptome of the CF epithelium in the different conditions. The possibility to faithfully represent the crosstalk between epithelial and connective in CF through the full thickness model, along with inflammation and stromal activation, makes the model suitable to better understand mechanisms of disease genesis, progression, and response to therapy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Two benign adenomatous lesions are commonly recognized within the sinonasal tract, namely respiratory epithelial adenomatoid hamartoma (REAH) and seromucinous hamartoma (SH). We present 10 hitherto unrecognized benign polypoid nasal and sinonasal tumoriform lesions having in average 3.6 cm in largest dimension, which are histogenetically related to SH and REAH. In addition to typical structures of REAH and SH, these lesions contained an additional characteristic and slightly atypical adenomatous component, which we termed atypical sinonasal glands arising in SH (ASGSH). ASGSH often produced deep red colored secretion with peripheral clearing similar to that seen in thyroid follicles. In contrast to SH, ASGSH was endowed by both secretory and myoepithelial layers and had mostly angulated shapes with snout-like protrusions into the lumens. Both layers were formed by an irregular, disorganized, and often incomplete cell lining, which had slightly atypical cytological features without mitoses. In 3 cases, ASGSHs revealed sebaceous differentiation, and in 3 cases the stroma produced a well-differentiated cartilage. Neoplastic nature of ASGSH was supported by finding of various mutations as revealed by next generation sequencing in five cases. In two cases each, we found identical mutations in BRAF gene (Val600Glu), and RET gene (Arg912Trp), respectively and in one case FAT1 gene alteration (Pro1665Leu)., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Epithelial polarity is fundamental in maintaining barrier integrity and tissue protection. In cystic fibrosis (CF), apicobasal polarity of the airway epithelium is altered, resulting in increased apical fibronectin deposition and enhanced susceptibility to bacterial infections. Here, we evaluated the effect of highly effective modulator treatment (HEMT) on fibronectin apical deposition and investigated the intracellular mechanisms triggering the defect in polarity of the CF airway epithelium. To this end, primary cultures of CF (F508del variant) human airway epithelial cells (HAECs) and a HAEC line, Calu-3, knocked down for CFTR (CF transmembrane conductance regulator) were compared with control counterparts. We show that CFTR mutation in primary HAECs and CFTR knockdown cells promote the overexpression and oversecretion of TGF-β1 and DKK1 when cultured at an air-liquid interface. These dynamic changes result in hyperactivation of the TGF-β pathway and inhibition of the Wnt pathway through degradation of β-catenin leading to imbalanced proliferation and polarization. The abnormal interplay between TGF-β and Wnt signaling pathways is reinforced by aberrant Akt signaling. Pharmacological manipulation of TGF-β, Wnt, and Akt pathways restored polarization of the F508del CF epithelium, a correction that was not achieved by HEMT. Our data shed new insights into the signaling pathways that fine-tune apicobasal polarization in primary airway epithelial cells and may provide an explanation to the mitigated efficacy of HEMT on lung infection in people with CF.

Acute lung injury (ALI) is a devastating clinical syndrome caused by different factors, with high morbidity and mortality. Lung injury and inflammation caused by lipopolysaccharide (LPS) can be modulated by NLRP3 inflammasome activation, yet its exact function within the airway epithelium is still unknown. Meanwhile, glucose transporter protein 1 (GLUT1) contributes to a number of inflammatory illnesses, including ALI. The present study aimed to assess GLUT1's function in NLRP3 inflammasome activation of airway epithelium in LPS-induced acute lung injury. BALB/c mice and BEAS-2B cells were exposed to LPS (5 mg/kg and 200 μg/mL, respectively), with or without GLUT1 antagonists (WZB117 or BAY876). LPS up-regulated pulmonary expression of NLRP3 and GLUT1 in mice, which could be blocked by WZB117 or BAY876. Pharmacological inhibition of GLUT1 in vivo significantly attenuated lung tissue damage, neutrophil accumulation, and proinflammatory factors release (TNF-α, IL-6, and IL-1β) in LPS-exposed mice. Meanwhile, the activation markers of NLRP3 inflammasome (ASC, caspase-1, IL-1β, and IL-18) induced by LPS were also suppressed. In cultured BEAS-2B cells, LPS induced an increase in GLUT1 expression and triggered activation of the NLRP3 inflammasome, both of which were inhibited by GLUT1 antagonists. These results illustrate that GLUT1 participates in LPS-induced ALI and promotes the activation of the NLRP3 inflammasome in airway epithelial cells., Competing Interests: Disclosure Statement None declared., (Copyright © 2024 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

A primary orbital respiratory cyst is a congenital choristoma that presents in the orbit and with different signs and symptoms depending on the location, which might also change the surgical approach. The aim of this report is to describe 2 new cases of primary respiratory epithelial cysts and to review the literature on presentation, management, and risk factors with different surgical approaches and complications. Two cases presenting with gradually increased proptosis had a confirmed diagnosis of a respiratory epithelial cyst. CT and MRI imaging revealed a thin-walled intraconal cystic lesion. Complete surgical removal was not possible and an incisional biopsy of the wall was performed. Rarely, orbital respiratory epithelium cysts are primary lesions. The high risk of breaking the capsule during surgery and the presence of residual epithelial cells within the orbit may cause cyst's recurrence. Indeed, we recommend careful attention during dissection maneuvers and a long-term follow-up., Competing Interests: The authors have no financial or conflicts of interest to disclose., (Copyright © 2024 The American Society of Ophthalmic Plastic and Reconstructive Surgery, Inc.)

Background and Purpose: Airway epithelial cells (AECs) regulate the activation of epithelial-mesenchymal trophic units (EMTUs) during airway remodelling through secretion of signalling mediators. However, the major trigger and the intrinsic pathogenesis of airway remodelling is still obscure., Experimental Approach: The differing expressed genes in airway epithelia related to airway remodelling were screened and verified by RNA-sequencing and signalling pathway analysis. Then, the effects of increased cathepsin K (CTSK) in airway epithelia on airway remodelling and EMTU activation were identified both in vitro and in vivo, and the molecular mechanism was elucidated in the EMTU model. The potential of CTSK as an an effective biomarker of airway remodelling was analysed in an asthma cohort of differing severity. Finally, an inhibitor of CTSK was administered for potential therapeutic intervention for airway remodelling in asthma., Key Results: The expression of CTSK in airway epithelia increased significantly along with the development of airway remodelling in a house dust mite (HDM)-stressed asthma model. Increased secretion of CTSK from airway epithelia induced the activation of EMTUs by activation of the PAR2-mediated pathway. Blockade of CTSK inhibited EMTU activation and alleviated airway remodelling as an effective intervention target of airway remodelling., Conclusion and Implications: Increased expression of CTSK in airway epithelia is involved in the development of airway remodelling in asthma through EMTU activation, mediated partly through the PAR2-mediated signalling pathway. CTSK is a potential biomarker for airway remodelling, and may also be a useful intervention target for airway remodelling in asthma patients., (© 2024 British Pharmacological Society.)

The number of adults living with cystic fibrosis (CF) has already increased significantly because of drastic improvements in life expectancy attributable to advances in treatment, including the development of highly effective modulator therapy. Chronic airway inflammation in CF contributes to morbidity and mortality, and aging processes like inflammaging and cell senescence influence CF pathology. Our results show that single-cell RNA sequencing data, human primary bronchial epithelial cells from non-CF and CF donors, a CF bronchial epithelial cell line, and Cftr-knockout (Cftr-/-) rats all demonstrated increased cell senescence markers in the CF bronchial epithelium. This was associated with upregulation of fibroblast growth factor receptors (FGFRs) and mitogen-activated protein kinase (MAPK) p38. Inhibition of FGFRs, specifically FGFR4 and to some extent FGFR1, attenuated cell senescence and improved mucociliary clearance, which was associated with MAPK p38 signaling. Mucociliary dysfunction could also be improved using a combination of senolytics in a CF ex vivo model. In summary, FGFR/MAPK p38 signaling contributes to cell senescence in CF airways, which is associated with impaired mucociliary clearance. Therefore, attenuation of cell senescence in the CF airways might be a future therapeutic strategy improving mucociliary dysfunction and lung disease in an aging population with CF.

Mucus plugs occlude airways to obstruct airflow in asthma. Studies in patients and in mouse models show that mucus plugs occur in the context of type 2 inflammation, and studies in human airway epithelial cells (HAECs) show that IL-13-activated cells generate pathologic mucus independently of immune cells. To determine how HAECs autonomously generate pathologic mucus, we used a magnetic microwire rheometer to characterize the viscoelastic properties of mucus secreted under varying conditions. We found that normal HAEC mucus exhibited viscoelastic liquid behavior and that mucus secreted by IL-13-activated HAECs exhibited solid-like behavior caused by mucin cross-linking. In addition, IL-13-activated HAECs shows increased peroxidase activity in apical secretions, and an overlaid thiolated polymer (thiomer) solution shows an increase in solid behavior that was prevented by peroxidase inhibition. Furthermore, gene expression for thyroid peroxidase (TPO), but not lactoperoxidase (LPO), was increased in IL-13-activated HAECs and both TPO and LPO catalyze the formation of oxidant acids that cross-link thiomer solutions. Finally, gene expression for TPO in airway epithelial brushings was increased in patients with asthma with high airway mucus plug scores. Together, our results show that IL-13-activated HAECs autonomously generated pathologic mucus via peroxidase-mediated cross-linking of mucin polymers.

Rationale: Pseudomonas aeruginosa is the major bacterial pathogen colonizing the airways of adult patients with cystic fibrosis (CF) and causes chronic infections that persist despite antibiotic therapy. Intracellular bacteria may represent an unrecognized reservoir of bacteria that evade the immune system and antibiotic therapy. Although the ability of P. aeruginosa to invade and survive within epithelial cells has been described in vitro in different epithelial cell models, evidence of this intracellular lifestyle in human lung tissues is currently lacking. Objectives: To detect and characterize intracellular P. aeruginosa in CF airway epithelium from human lung explant tissues. Methods: We sampled lung explant tissues from patients with CF undergoing lung transplantation and non-CF lung donor control tissue. We analyzed lung tissue sections for the presence of intracellular P. aeruginosa using quantitative culture and microscopy, in parallel to histopathology and airway morphometry. Measurements and Main Results: P. aeruginosa was isolated from the lungs of seven patients with CF undergoing lung transplantation. Microscopic assessment revealed the presence of intracellular P. aeruginosa within airway epithelial cells in three of the seven patients analyzed at a varying but low frequency. We observed those events occurring in lung regions with high bacterial burden. Conclusions: This is the first study describing the presence of intracellular P. aeruginosa in CF lung tissues. Although intracellular P. aeruginosa in airway epithelial cells is likely relatively rare, our findings highlight the plausible occurrence of this intracellular bacterial reservoir in chronic CF infections.

Introduction: Exacerbations of chronic obstructive pulmonary disease (COPD) increase mortality risk and can lead to accelerated loss of lung function. The increased inflammatory response during exacerbations contributes to worsening of airflow limitation, but whether it also impacts epithelial repair is unclear. Therefore, we studied the effect of the soluble factor micro-environment during COPD exacerbations on epithelial repair using an exacerbation cocktail (EC), composed of four factors that are increased in COPD lungs during exacerbations (IL-1β, IL-6, IL-8, TNF-α)., Methods: Mouse organoids (primary CD31-CD45-Epcam+ cells co-cultured with CCL206 fibroblasts) were used to study epithelial progenitor behavior. Mature epithelial cell responses were evaluated using mouse precision cut lung slices (PCLS). The expression of epithelial supportive factors was assessed in CCL206 fibroblasts and primary human lung fibroblasts., Results: EC exposure increased the number and size of organoids formed, and upregulated Lamp3 , Muc5ac and Muc5b expression in day 14 organoids. In PCLS, EC imparted no effect on epithelial marker expression. Pre-treatment of CCL206 fibroblasts with EC was sufficient to increase organoid formation. Additionally, the expression of Il33 , Tgfa and Areg was increased in CCL206 fibroblasts from EC treated organoids, but these factors individually did not affect organoid formation or size. However, TGF-α downregulated Foxj1 expression and upregulated Aqp5 expression in day 14 organoids., Conclusions: EC exposure stimulates organoid formation and growth, but it alters epithelial differentiation. EC changes the epithelial progenitor support function of fibroblasts which contributes to observed effects on epithelial progenitors., Competing Interests: RK, JB, and RG receive unrestricted research funds from Boehringer Ingelheim to the institution. KG-K is an employee of Boehringer Ingelheim. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Kortekaas, Geillinger-Kästle, Fuentes-Mateos, van Orsoy, Al-Alyan, Burgess and Gosens.)

Objectives: Tracheal transplantation is an ideal option for the reconstruction of long-segment circumferential tracheal defects. Our group performed the first successful vascularized single-staged tracheal transplantation in January 2021. Although a rigid biocompatible structure is necessary for a functioning tracheal replacement, the importance of ciliated epithelium, which allows for critical mucociliary clearance, is now being appreciated. Here, we examined the histological changes of the first single-staged human tracheal transplant from serial endoscopic biopsies., Methods: Biopsies of the tracheal mucosa were serially obtained since the time of the tracheal transplantation. Samples were examined via hematoxylin and eosin, electron microscopy, and immunohistochemistry., Results: One week after transplantation, there is loss of ciliated epithelium and seromucinous cells, with only a basal layer of epithelium remaining. By 2 weeks, however, the epithelium begins to recover, albeit differently depending on the location of the biopsy. Near the site of tracheal anastomosis, there is epithelial proliferation, with the appearance of early ciliated cells. However, in the midgraft, there appears to be evidence of squamous metaplasia. Over time, however, normal ciliated epithelium and mucous cells appear without signs of chronic inflammation., Conclusions: Critically, the tracheal allograft regained normal appearing respiratory epithelium after initial ischemic injury. The histologic differences at the midgraft versus anastomosis may suggest unique mechanisms of reepithelialization. At the recipient-donor interface, there may be a faster direct migration of recipient-derived epithelial cells, in line with preclinical studies. The midgraft, in contrast, responds with epithelial proliferation from the donor basal cells or dedifferentiated mucous cells., Level of Evidence: N/A Laryngoscope, 134:2664-2671, 2024., (© 2023 The American Laryngological, Rhinological and Otological Society, Inc.)

Foregut duplication cyst is most commonly seen in the posterior mediastinum without communication with adjacent organs or presence of other malformations and typically shows ectopic gastric or respiratory epithelium. The finding of ectopic pancreatic tissue is extremely rare. A 15-year-old female patient presented with elevated blood pressure, intermittent right flank pain for 18 months. An abdominal MRI revealed a 4 cm right cystic retroperitoneal mass, initially thought to arise from the right adrenal gland. Intraoperatively, the mass was centered in the retroperitoneum between the right adrenal gland and kidney, without attachments to these organs and no communication with other structures, and it was completely excised. Gross examination revealed a 3.5 cm well-circumscribed solid and cystic mass with orange-white cut surface and cloudy fluid surrounded by variable amounts of adipose tissue. On microscopic examination, the cysts were lined by respiratory and gastric antral/oxyntic-type mucosa, surrounded by muscularis mucosae, submucosal tissue, muscularis propria, and perienteric tissue. Within the muscular propria, exocrine pancreatic tissue was also noted. The patient is well with 7-months of follow up. This case is the first one reporting gastric, respiratory, and pancreatic epithelia., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Chronic exposure to environmental hazards causes airway epithelial dysfunction, primarily impaired physical barriers, immune dysfunction, and repair or regeneration. Impairment of airway epithelial function subsequently leads to exaggerated airway inflammation and remodeling, the main features of chronic obstructive pulmonary disease (COPD). Mitochondrial damage has been identified as one of the mechanisms of airway abnormalities in COPD, which is closely related to airway inflammation and airflow limitation. In this review, we evaluate updated evidence for airway epithelial mitochondrial damage in COPD and focus on the role of mitochondrial damage in airway epithelial dysfunction. In addition, the possible mechanism of airway epithelial dysfunction mediated by mitochondrial damage is discussed in detail, and recent strategies related to airway epithelial-targeted mitochondrial therapy are summarized. Results have shown that dysregulation of mitochondrial quality and oxidative stress may lead to airway epithelial dysfunction in COPD. This may result from mitochondrial damage as a central organelle mediating abnormalities in cellular metabolism. Mitochondrial damage mediates procellular senescence effects due to mitochondrial reactive oxygen species, which effectively exacerbate different types of programmed cell death, participate in lipid metabolism abnormalities, and ultimately promote airway epithelial dysfunction and trigger COPD airway abnormalities. These can be prevented by targeting mitochondrial damage factors and mitochondrial transfer. Thus, because mitochondrial damage is involved in COPD progression as a central factor of homeostatic imbalance in airway epithelial cells, it may be a novel target for therapeutic intervention to restore airway epithelial integrity and function in COPD.

Introduction: Environmental pollutants injure the mucociliary elevator, thereby provoking disease progression in chronic obstructive pulmonary disease (COPD). Epithelial resilience mechanisms to environmental nanoparticles in health and disease are poorly characterised., Methods: We delineated the impact of prevalent pollutants such as carbon and zinc oxide nanoparticles, on cellular function and progeny in primary human bronchial epithelial cells (pHBECs) from end-stage COPD (COPD-IV, n=4), early disease (COPD-II, n=3) and pulmonary healthy individuals (n=4). After nanoparticle exposure of pHBECs at air-liquid interface, cell cultures were characterised by functional assays, transcriptome and protein analysis, complemented by single-cell analysis in serial samples of pHBEC cultures focusing on basal cell differentiation., Results: COPD-IV was characterised by a prosecretory phenotype (twofold increase in MUC5AC + ) at the expense of the multiciliated epithelium (threefold reduction in Ac-Tub + ), resulting in an increased resilience towards particle-induced cell damage (fivefold reduction in transepithelial electrical resistance), as exemplified by environmentally abundant doses of zinc oxide nanoparticles. Exposure of COPD-II cultures to cigarette smoke extract provoked the COPD-IV characteristic, prosecretory phenotype. Time-resolved single-cell transcriptomics revealed an underlying COPD-IV unique basal cell state characterised by a twofold increase in KRT5 + ( P =0.018) and LAMB3 + ( P =0.050) expression, as well as a significant activation of Wnt-specific ( P =0.014) and Notch-specific ( P =0.021) genes, especially in precursors of suprabasal and secretory cells., Conclusion: We identified COPD stage-specific gene alterations in basal cells that affect the cellular composition of the bronchial elevator and may control disease-specific epithelial resilience mechanisms in response to environmental nanoparticles. The identified phenomena likely inform treatment and prevention strategies., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Squamous cell lung cancer (SCLC) occurs as a result of dysregenerative changes in the bronchial epithelium: basal cell hyperplasia (BCH), squamous cell metaplasia (SM), and dysplasia. We previously suggested that combinations of precancerous changes detected in the small bronchi of patients with SCLC may reflect various "scenarios" of the precancerous process: isolated BCH→stopping at the stage of hyperplasia, BCH+SM→progression of hyperplasia into metaplasia, SM+dysplasia→progression of metaplasia into dysplasia. In this study, DNA methylome of various forms of precancerous changes in the bronchial epithelium of SCLC patients was analyzed using the genome-wide bisulfite sequencing. In BCH combined with SM, in contrast to isolated BCH, differentially methylated regions were identified in genes of the pathogenetically significant MET signaling pathway (RNMT, HPN). Differentially methylated regions affecting genes involved in inflammation regulation (IL-23, IL-23R, IL12B, IL12RB1, and FIS1) were detected in SM combined with dysplasia in comparison with SM combined with BCH. The revealed changes in DNA methylation may underlie various "scenarios" of the precancerous process in the bronchial epithelium., (© 2024. Springer Science+Business Media, LLC, part of Springer Nature.)

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived pleiotropic cytokine that regulates T-helper 2 (Th2) immune responses in the lung and plays a major role in severe uncontrolled asthma. Emerging evidence suggests a role for endoplasmic reticulum (ER) stress in the pathogenesis of asthma. In this study, we determined if ER stress and the unfolded protein response (UPR) signaling are involved in TSLP induction in the airway epithelium. For this, we treated human bronchial epithelial basal cells and differentiated primary bronchial epithelial cells with ER stress inducers and the TSLP mRNA and protein expression was determined. A series of siRNA gene knockdown experiments were conducted to determine the ER stress-induced TSLP signaling pathways. cDNA collected from asthmatic bronchial biopsies was used to determine the gene correlation between ER stress and TSLP. Our results show that ER stress signaling induces TSLP mRNA expression via the PERK-C/EBP homologous protein (CHOP) signaling pathway. AP-1 transcription factor is important in regulating this ER stress-induced TSLP mRNA induction, though ER stress alone cannot induce TSLP protein production. However, ER stress significantly enhances TLR3-induced TSLP protein secretion in the airway epithelium. TSLP and ER stress (PERK) mRNA expression positively correlates in bronchial biopsies from participants with asthma, particularly in neutrophilic asthma. In conclusion, these results suggest that ER stress primes TSLP that is then enhanced further upon TLR3 activation, which may induce severe asthma exacerbations. Targeting ER stress using pharmacological interventions may provide novel therapeutics for severe uncontrolled asthma. NEW & NOTEWORTHY TSLP is an epithelial-derived cytokine and a key regulator in the pathogenesis of severe uncontrolled asthma. We demonstrate a novel mechanism by which endoplasmic reticulum stress signaling upregulates airway epithelial TSLP mRNA expression via the PERK-CHOP signaling pathway and enhances TLR3-mediated TSLP protein secretion.

Airway hillocks are stratified epithelial structures of unknown function 1 . Hillocks persist for months and have a unique population of basal stem cells that express genes associated with barrier function and cell adhesion. Hillock basal stem cells continually replenish overlying squamous barrier cells. They exhibit dramatically higher turnover than the abundant, largely quiescent classic pseudostratified airway epithelium. Hillocks resist a remarkably broad spectrum of injuries, including toxins, infection, acid and physical injury because hillock squamous cells shield underlying hillock basal stem cells from injury. Hillock basal stem cells are capable of massive clonal expansion that is sufficient to resurface denuded airway, and eventually regenerate normal airway epithelium with each of its six component cell types. Hillock basal stem cells preferentially stratify and keratinize in the setting of retinoic acid signalling inhibition, a known cause of squamous metaplasia 2,3 . Here we show that mouse hillock expansion is the cause of vitamin A deficiency-induced squamous metaplasia. Finally, we identify human hillocks whose basal stem cells generate functional squamous barrier structures in culture. The existence of hillocks reframes our understanding of airway epithelial regeneration. Furthermore, we show that hillocks are one origin of 'squamous metaplasia', which is long thought to be a precursor of lung cancer., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

GDF15 (growth differentiation factor 15) is a stress cytokine with several proposed roles, including support of stress erythropoiesis. Higher circulating GDF15 levels are prognostic of mortality during acute respiratory distress syndrome, but the cellular sources and downstream effects of GDF15 during pathogen-mediated lung injury are unclear. We quantified GDF15 in lower respiratory tract biospecimens and plasma from patients with acute respiratory failure. Publicly available data from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were reanalyzed. We used mouse models of hemorrhagic acute lung injury mediated by Pseudomonas aeruginosa exoproducts in wild-type mice and mice genetically deficient for Gdf15 or its putative receptor, Gfral . In critically ill humans, plasma levels of GDF15 correlated with lower respiratory tract levels and were higher in nonsurvivors. SARS-CoV-2 infection induced GDF15 expression in human lung epithelium, and lower respiratory tract GDF15 levels were higher in coronavirus disease (COVID-19) nonsurvivors. In mice, intratracheal P. aeruginosa type II secretion system exoproducts were sufficient to induce airspace and plasma release of GDF15, which was attenuated with epithelial-specific deletion of Gdf15 . Mice with global Gdf15 deficiency had decreased airspace hemorrhage, an attenuated cytokine profile, and an altered lung transcriptional profile during injury induced by P. aeruginosa type II secretion system exoproducts, which was not recapitulated in mice deficient for Gfral . Airspace GDF15 reconstitution did not significantly modulate key lung cytokine levels but increased circulating erythrocyte counts. Lung epithelium releases GDF15 during pathogen injury, which is associated with plasma levels in humans and mice and can increase erythrocyte counts in mice, suggesting a novel lung-blood communication pathway.

Introduction: The anti-inflammatory effect of green tea extract (GTE) has been confirmed in asthmatic mice, however, the pharmacological mechanism is not fully elucidated., Methods: To investigate the therapeutic efficacy of GTE in asthma and identify specific pathways, murine model of allergic asthma was established by ovalbumin (OVA) sensitization and the challenge for 4 weeks, with oral treatment using GTE and dexamethasone (DEX). Inflammatory cell counts, cytokines, OVA-specific IgE, airway hyperreactivity, and antioxidant markers in the lung were evaluated. Also, pulmonary histopathological analysis and western blotting were performed. In vitro , we established the model by stimulating the human airway epithelial cell line NCI-H292 using lipopolysaccharide, and treating with GTE and mitogen-activated protein kinases (MAPKs) inhibitors., Results: The GTE100 and GTE400 groups showed a decrease in airway hyperresponsiveness and the number of inflammatory cells in the bronchoalveolar lavage fluid (BALF) compared to the OVA group. GTE treatment also reduced interleukin (IL)-13, IL-5, and IL-4 levels in the BALF, and OVA-specific immunoglobulin E levels in the serum compared to those in the OVA group. GTE treatment decreased OVA-induced mucus secretion and airway inflammation. In addition, GTE suppressed the oxidative stress, and phosphorylation of MAPKs, which generally occurs after exposure to OVA. GTE administration also reduced matrix metalloproteinase-9 activity and protein levels., Conclusion: GTE effectively inhibited asthmatic respiratory inflammation and mucus hyperproduction induced by OVA inhalation. These results suggest that GTE has the potential to be used for the treatment of asthma., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Kim, Kim, Jeong, Kim, Chung, Kim, Hong, Kwon, Ko and Kim.)

Biphenotypic sinonasal sarcoma is a newly established tumor entity that is associated with distinct clinicopathological findings. Biphenotypic sinonasal sarcoma is a rare, low-grade spindle cell sarcoma that arises in middle-aged females, exclusively in the sinonasal tract. A fusion gene involving PAX3 is detected in most biphenotypic sinonasal sarcomas, which aids in its diagnosis. Here, we report a case of biphenotypic sinonasal sarcoma with its cytological findings. The patient was a 73-year-old woman who presented with purulent nasal discharge and dull pain in the left cheek area. Computed tomography showed a mass extending from the left nasal cavity to the left ethmoid sinus, the left frontal sinus, and the frontal skull base. She underwent a combined transcranial and endoscopic approach for en bloc resection with a safety margin. Histologically, spindle-shaped tumor cells have been thought to proliferate mainly in the subepithelial stroma. Here, nasal mucosal epithelial hyperplasia was noted, and the tumor had invaded the bone tissue accompanying the epithelial cells. Fluorescence in situ hybridization (FISH) analysis showed a PAX3 rearrangement, and next-generation sequencing identified a PAX3::MAML3 fusion. Based on FISH, split signals were observed not in respiratory cells but in stromal cells. This indicated that respiratory cells were non-neoplastic. In the diagnosis of biphenotypic sinonasal sarcoma, the inverted growth of the respiratory epithelium can be a diagnostic pitfall. FISH analysis using a PAX3 break-apart probe is helpful not only for an accurate diagnosis but also for detecting the true neoplastic cells., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Key Points: Respiratory epithelial adenomatoid hamartoma (REAH) is easily confused with nasal polyps (NP). The typical manifestation of REAH on CT is the enlargement of bilateral olfactory clefts (OCs). The widening of the OCs in the CT scan is a biomarker for diagnosing REAH associated with NP., (© 2022 ARS-AAOA, LLC.)

Human airway epithelium (HAE) represents the primary site of viral infection for SARS-CoV-2. Comprising different cell populations, a lot of research has been aimed at deciphering the major cell types and infection dynamics that determine disease progression and severity. However, the cell type-specific replication kinetics, as well as the contribution of cellular composition of the respiratory epithelium to infection and pathology are still not fully understood. Although experimental advances, including Air-liquid interface (ALI) cultures of reconstituted pseudostratified HAE, as well as lung organoid systems, allow the observation of infection dynamics under physiological conditions in unprecedented level of detail, disentangling and quantifying the contribution of individual processes and cells to these dynamics remains challenging. Here, we present how a combination of experimental data and mathematical modelling can be used to infer and address the influence of cell type specific infectivity and tissue composition on SARS-CoV-2 infection dynamics. Using a stepwise approach that integrates various experimental data on HAE culture systems with regard to tissue differentiation and infection dynamics, we develop an individual cell-based model that enables investigation of infection and regeneration dynamics within pseudostratified HAE. In addition, we present a novel method to quantify tissue integrity based on image data related to the standard measures of transepithelial electrical resistance measurements. Our analysis provides a first aim of quantitatively assessing cell type specific infection kinetics and shows how tissue composition and changes in regeneration capacity, as e.g. in smokers, can influence disease progression and pathology. Furthermore, we identified key measurements that still need to be assessed in order to improve inference of cell type specific infection kinetics and disease progression. Our approach provides a method that, in combination with additional experimental data, can be used to disentangle the complex dynamics of viral infection and immunity within human airway epithelial culture systems., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Raach et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Respiratory epithelial adenomatoid hamartoma (REAH) is a sinonasal glandular overgrowth arising from the surface respiratory epithelium and invaginating into the stroma. Clinically, it appears as a polypoid mass that may cause nasal obstruction, anosmia, and epistaxis. The presence of cartilaginous and/or osseous areas move the lesion to a chondro-osseous respiratory epithelial (CORE) hamartoma subtype. Scattered small seromucinous glands may be observed between typical REAH glands and when it is the only feature, it represents seromucinous hamartoma (SH). The molecular pathogenesis of REAH has been poorly explored and remains unclear. Given that KRAS, BRAF, and EGFR mutations have been detected in a variety of sinonasal tumors, we aimed to assess these mutations in REAH and SH., Methods: Ten REAH (including one CORE subtype), in addition to two SH cases, were Sanger sequenced by standard techniques. The targeted regions included KRAS exons 2-4 (encompassing hotspots codons 12, 13, 61, and 146), BRAF exons 11 and 15 (spanning the V600 codon), and EGFR exons 19 and 20., Results: All REAH and SH samples showed wild-type sequences for KRAS, BRAF, and EGFR genes., Conclusion: Our results demonstrate a lack of KRAS, BRAF, or EGFR pathogenic variants with further evaluation of REAH and SH needed to elucidate driver genetic events., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The airway surface liquid (ASL) is a thin sheet of fluid that covers the luminal aspect of the airway epithelium. The ASL is a site of several first-line host defenses, and its composition is a key factor that determines respiratory fitness. Specifically, the acid-base balance of ASL has a major influence on the vital respiratory defense processes of mucociliary clearance and antimicrobial peptide activity against inhaled pathogens. In the inherited disorder cystic fibrosis (CF), loss of cystic fibrosis transmembrane conductance regulator (CFTR) anion channel function reduces HCO 3 - secretion, lowers the pH of ASL (pH ASL ), and impairs host defenses. These abnormalities initiate a pathologic process whose hallmarks are chronic infection, inflammation, mucus obstruction, and bronchiectasis. Inflammation is particularly relevant as it develops early in CF and persists despite highly effective CFTR modulator therapy. Recent studies show that inflammation may alter HCO 3 - and H + secretion across the airway epithelia and thus regulate pH ASL . Moreover, inflammation may enhance the restoration of CFTR channel function in CF epithelia exposed to clinically approved modulators. This review focuses on the complex relationships between acid-base secretion, airway inflammation, pH ASL regulation, and therapeutic responses to CFTR modulators. These factors have important implications for defining optimal ways of tackling CF airway inflammation in the post-modulator era.

Respiratory epithelial adenomatoid hamartoma (REAH) is a benign lesion of the nasal cavity and paranasal sinuses. Here, we report the clinicopathological characteristics of REAH identified in 2065 cases with nasal/paranasal polypoid lesions treated with endoscopic sinus surgery (ESS) at our hospital from 2008 to 2021. Cases including the olfactory area were reviewed and 50 patients of REAH were identified pathologically (50/2065, 2.4%). The average age was 58.9 years old and the male/female ratio was 45/5. Grossly, REAH showed a whitish surface and elastic firm consistency. The histopathological characteristics included proliferation of small to medium-sized glands composed of ciliated respiratory epithelium containing goblet cells; thickening of the basement membrane compared to that for inverted papilloma (9.6 ± 2.4 vs. 1.3 ± 1.6 µm, p < 0.001); and no intra-epithelial neutrophilic infiltration. Among the REAH cases, 81% were associated with sinonasal inflammatory polyps. Many olfactory cleft polyps were REAH (38/98, 39%). The rate of REAH found in ESS in the last 7 years was higher than that in the first 7 years (3.17% vs. 1.62%, p = 0.032). Our results in Japanese patients are similar to those found in other countries, including male predominance. REAH is relatively common and that 39% of polyps taken from olfactory clefts are REAH., (© 2022 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.)

Bronchiolitis obliterans (BO) is a debilitating disease of the small airways that can develop following exposure to toxic chemicals as well as respiratory tract infections. BO development is strongly associated with diacetyl (DA) inhalation exposures at occupationally relevant concentrations or severe influenza A viral (IAV) infections. However, it remains unclear whether lower dose exposures or more mild IAV infections can result in similar pathology. In the current work, we combined these two common environmental exposures, DA and IAV, to test whether shorter DA exposures followed by sublethal IAV infection would result in similar airways disease. Adult mice exposed to DA vapors 1 h/day for 5 consecutive days followed by infection with the airway-tropic IAV H3N2 (HKx31) resulted in increased mortality, increased bronchoalveolar lavage (BAL) neutrophil percentage, mixed obstruction and restriction by lung function, and subsequent airway remodeling. Exposure to DA or IAV alone failed to result in significant pathology, whereas mice exposed to DA + IAV showed increased α-smooth muscle actin (αSMA) and epithelial cells coexpressing the basal cell marker keratin 5 (KRT5) with the club cell marker SCGB1A1. To test whether DA exposure impairs epithelial repair after IAV infection, mice were infected first with IAV and then exposed to DA during airway epithelial repair. Mice exposed to IAV + DA developed similar airway remodeling with increased subepithelial αSMA and epithelial cells coexpressing KRT5 and SCGB1A1. Our findings reveal an underappreciated concept that common environmental insults while seemingly harmless by themselves can have catastrophic implications on lung function and long-term respiratory health when combined.

Background: Chronic Obstructive Pulmonary Disease (COPD), a major cause of mortality and disability, is a complex disease with heterogeneous and ill-understood biological mechanisms. Human induced pluripotent stem cells (hiPSCs) are a promising tool to model human disease, including the impact of genetic susceptibility. Methods: We developed a simple and reliable method for reprogramming peripheral blood mononuclear cells into hiPSCs and to differentiate them into air−liquid interface bronchial epithelium within 45 days. Importantly, this method does not involve any cell sorting step. We reprogrammed blood cells from one healthy control and three patients with very severe COPD. Results: The mean cell purity at the definitive endoderm and ventral anterior foregut endoderm (vAFE) stages was >80%, assessed by quantifying C-X-C Motif Chemokine Receptor 4/SRY-Box Transcription Factor 17 (CXCR4/SOX17) and NK2 Homeobox 1 (NKX2.1) expression, respectively. vAFE cells from all four hiPSC lines differentiated into bronchial epithelium in air−liquid interface conditions, with large zones covered by beating ciliated, basal, goblets, club cells and neuroendocrine cells, as found in vivo. The hiPSC-derived airway epithelium (iALI) from patients with very severe COPD and from the healthy control were undistinguishable. Conclusions: iALI bronchial epithelium is ready for better understanding lung disease pathogenesis and accelerating drug discovery.

SARS-CoV-2, the culprit pathogen of COVID-19, elicits prominent immune responses and cytokine storms. Intracellular Cl - is a crucial regulator of host defense, whereas the role of Cl - signaling pathway in modulating pulmonary inflammation associated with SARS-CoV-2 infection remains unclear. By using human respiratory epithelial cell lines, primary cultured human airway epithelial cells, and murine models of viral structural protein stimulation and SARS-CoV-2 direct challenge, we demonstrated that SARS-CoV-2 nucleocapsid (N) protein could interact with Smad3, which downregulated cystic fibrosis transmembrane conductance regulator (CFTR) expression via microRNA-145. The intracellular Cl - concentration ([Cl - ] i ) was raised, resulting in phosphorylation of serum glucocorticoid regulated kinase 1 (SGK1) and robust inflammatory responses. Inhibition or knockout of SGK1 abrogated the N protein-elicited airway inflammation. Moreover, N protein promoted a sustained elevation of [Cl - ] i by depleting intracellular cAMP via upregulation of phosphodiesterase 4 (PDE4). Rolipram, a selective PDE4 inhibitor, countered airway inflammation by reducing [Cl - ] i . Our findings suggested that Cl - acted as the crucial pathological second messenger mediating the inflammatory responses after SARS-CoV-2 infection. Targeting the Cl - signaling pathway might be a novel therapeutic strategy for COVID-19., (© 2022. The Author(s).)

Introduction: The airway epithelium is a key system within the lung. It acts as a physical barrier to inhaled factors, and can actively remove unwanted microbes and particles from the lung via the mucociliary escalator. On a physiological level, it senses the presence of pathogens and initiates innate immune responses to combat their effects. Hydration of the airways is also controlled by the epithelium. Within the cystic fibrosis (CF) lung, these properties are suboptimal and contribute to the pulmonary manifestations of CF., Areas Covered: In this review, we discuss how various host and microbial factors can contribute to airway epithelium dysfunction in the CF lung focusing on mechanisms relating to the mucociliary escalator and protease expression and function. We also explore how alterations in microRNA expression can impact the behavior of the airway epithelium., Expert Opinion: Notwithstanding the unprecedented benefits that CFTR modulator drugs now provide to the health of CF sufferers, it will be important to delve more deeply into additional mechanisms underpinning CF lung disease such as those illustrated here in an attempt to counteract these aberrant processes and further enhance quality of life for people with CF.

Sinonasal hamartomas are uncommon lesions of nasal and sinus cavities. Based on indigenous cellular components and characteristic histologic features, they are further classified into four entities: respiratory epithelial adenomatoid hamartoma (REAH), seromucinous hamartoma (SH), chondro-osseous and respiratory epithelial hamartoma (CORE), and nasal chondromesenchymal hamartoma (NCH). REAH, SH, and CORE are seen in adult patients, while NCH predominantly occurs in newborns and infants. Morphologically REAH and SH are composed of respiratory epithelium and seromucinous glands, CORE is related to REAH but with additional feature of chondroid and/or osseous tissue, and NCH is composed of chondroid and stromal elements but devoid of epithelial component. All four lesions can present as sinonasal mass lesions and with associated obstructive symptoms. Given the rarity of these lesions, diagnosis can be challenging, especially in unusual clinical scenario. In this study, we report six cases of sinonasal hamartoma, including one case of NCH, one case of CORE, two cases of SH, and two cases of REAH. All cases were from adult patients including four men and two women. We also review the literature of the clinical and pathologic features of these rare lesions.

The respiratory tract surface is protected from inhaled pathogens by a secreted layer of mucus rich in mucin glycoproteins. Abnormal mucus accumulation is a cardinal feature of chronic respiratory diseases, but the relationship between mucus and pathogens during exacerbations is poorly understood. We identified elevations in airway mucin 5AC (MUC5AC) and MUC5B concentrations during spontaneous and experimentally induced chronic obstructive pulmonary disease (COPD) exacerbations. MUC5AC was more sensitive to changes in expression during exacerbation and was therefore more predictably associated with viral load, inflammation, symptom severity, decrements in lung function, and secondary bacterial infections. MUC5AC was functionally related to inflammation, as Muc5ac-deficient (Muc5ac-/-) mice had attenuated RV-induced (RV-induced) airway inflammation, and exogenous MUC5AC glycoprotein administration augmented inflammatory responses and increased the release of extracellular adenosine triphosphate (ATP) in mice and human airway epithelial cell cultures. Hydrolysis of ATP suppressed MUC5AC augmentation of RV-induced inflammation in mice. Therapeutic suppression of mucin production using an EGFR antagonist ameliorated immunopathology in a mouse COPD exacerbation model. The coordinated virus induction of MUC5AC and MUC5B expression suggests that non-Th2 mechanisms trigger mucin hypersecretion during exacerbations. Our data identified a proinflammatory role for MUC5AC during viral infection and suggest that MUC5AC inhibition may ameliorate COPD exacerbations.

To understand protective immune responses against the onset of group A Streptococcus respiratory infection, we investigated whether MyD88 KO mice were susceptible to acute infection through transmission. After commingling with mice that had intranasal group A Streptococcus (GAS) inoculation, MyD88 -/- recipient mice had increased GAS loads in the nasal cavity and throat that reached a mean throat colonization of 6.3 × 10 6 CFU/swab and mean GAS load of 5.2 × 10 8 CFU in the nasal cavity on day 7. Beyond day 7, MyD88 -/- recipient mice became moribund, with mean 1.6 × 10 7 CFU/swab and 2.5 × 10 9 CFU GAS in the throat and nasal cavity, respectively. Systemic GAS infection occurred a couple of days after the upper respiratory infection. GAS infects the lip, the gingival sulcus of the incisor teeth, and the lamina propria of the turbinate but not the nasal cavity and nasopharyngeal tract epithelia, and C57BL/6J recipient mice had no or low levels of GAS in the nasal cavity and throat. Direct nasal GAS inoculation of MyD88 -/- mice caused GAS infection, mainly in the lamina propria of the turbinate. In contrast, C57BL/6J mice with GAS inoculation had GAS bacteria in the nasal cavity but not in the lamina propria of the turbinates. Thus, MyD88 -/- mice are highly susceptible to acute and lethal GAS infection through transmission, and MyD88 signaling is critical for protection of the respiratory tract lamina propria but not nasal and nasopharyngeal epithelia against GAS infection.