Sonic hedgehog signalling as a potential endobronchial biomarker in COPD

The disruptive effects of COPD exacerbation-associated factors on epithelial repair responses

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.

HDAC6-selective inhibitor CAY10603 ameliorates cigarette smoke-induced small airway remodeling by regulating epithelial barrier dysfunction and reversing

BACKGROUND

Small airway remodelling is a vital characteristic of chronic obstructive pulmonary disease (COPD), which is mainly caused by epithelial barrier dysfunction and epithelial-mesenchymal transition (EMT). Recent studies have indicated that histone deacetylase 6 (HDAC6) plays an important role in the dysregulation of epithelial function. In this study, we investigated the therapeutic effects and underlying mechanisms of an inhibitor with high selectivity for HDAC6 in COPD.

METHODS

Cigarette smoke (CS) exposure was used to establish a CS-induced COPD mouse model. CAY10603 at doses of 2.5 and 10 mg/kg was injected intraperitoneally on alternate days. The protective effects of CAY10603 against CS-induced emphysema, epithelial barrier function and small airway remodeling were evaluated using hematoxylin and eosin (H&E) staining, Masson's trichrome staining, immunohistochemical staining, and western blot. The human lung bronchial epithelial cell line (HBE) was used to elucidate the underlying molecular mechanism of action of CAY10603.

RESULTS

HDAC6 levels in the lung homogenates of CS-exposed mice were higher than that those in control mice. Compared to the CS group, the mean linear intercept (MLI) of the CAY10603 treatment group decreased and the mean alveolar number (MAN)increased. Collagen deposition was reduced in groups treated with CAY10603. The expression of α-SMA was markedly upregulated in the CS group, which was reversed by CAY10603 treatment. Conversely, E-cadherin expression in the CS group was further downregulated, which was reversed by CAY10603 treatment. CAY10603 affects the tight junction protein expression of ZO-1 and occludin. ZO-1 and occludin expression were markedly downregulated in the CS group. After CAY10603treatment, the protein expression level of ZO-1 and occludin increased significantly. In HBE cells, Cigarette smoke extract (CSE) increased HDAC6 levels. CAY10603 significantly attenuated the release of TGF-β1 induced by CSE. CAY10603 significantly increased the E-cadherin levels in TGF-β1 treated HBE cells, while concurrently attenuated α-SMA expression. This effect was achieved through the suppression of Smad2 and Smad3 phosphorylation. CAY10603 also inhibited TGF-β1 induced cell migration.

CONCLUSIONS

These findings suggested that CAY10603 inhibited CS induced small airway remodelling by regulating epithelial barrier dysfunction and reversing EMT via the TGF-β1/Smad2/3 signalling pathway.

Lung Fibroblasts from Chronic Obstructive Pulmonary Disease Subjects Have a Deficient Gene Expression Response to Cigarette Smoke Extract Compared to Healthy

Background and aim

Cigarette smoking is the most common cause of chronic obstructive pulmonary disease (COPD) but more mechanistic studies are needed. Cigarette smoke extract (CSE) can elicit a strong response in many COPD-related cell types, but no studies have been performed in lung fibroblasts. Therefore, we aimed to investigate the effect of CSE on gene expression in lung fibroblasts from healthy and COPD subjects.

Patients and methods

Primary lung fibroblasts, derived from six healthy and six COPD subjects (all current or ex-smokers), were either unstimulated (baseline) or stimulated with 30% CSE for 4 h prior to RNA isolation. The mRNA expression levels were measured using the NanoString nCounter Human Fibrosis V2 panel (760 genes). Pathway enrichment was assessed for unique gene ontology terms of healthy and COPD.

Results

At baseline, a difference in the expression of 17 genes was found in healthy and COPD subjects. Differential expression of genes after CSE stimulation resulted in significantly less changes in COPD lung fibroblasts (70 genes) than in healthy (207 genes), with 51 genes changed in both. COPD maintained low NOTCH signaling throughout and upregulated JUN >80%, indicating an increase in apoptosis. Healthy downregulated the Mitogen-activated protein kinase (MAPK) signaling cascade, including a ≥50% reduction in FGF2, CRK, TGFBR1 and MEF2A. Healthy also downregulated KAT6A and genes related to cell proliferation, all together indicating possible cell senescence signaling.

Conclusion

Overall, COPD lung fibroblasts responded to CSE stimulation with a very different and deficient expression profile compared to healthy. Highlighting that stimulated healthy cells are not an appropriate substitute for COPD cells which is important when investigating the mechanisms of COPD.

Sonic Hedgehog Signaling Is Essential for Pulmonary Ionocyte Specification in Human and Ferret Airway Epithelia

Pulmonary ionocytes express high levels of cystic fibrosis transmembrane conductance regulator (CFTR), an anion channel that is critical for hydration of the airways and mucociliary clearance. However, the cellular mechanisms that govern ionocyte specification and function remain unclear. We observed that increased abundance of ionocytes in cystic fibrosis (CF) airway epithelium was associated with enhanced expression of Sonic Hedgehog (SHH) effectors. In this study, we evaluated whether the SHH pathway directly impacts ionocyte differentiation and CFTR function in airway epithelia. Pharmacological HPI1-mediated inhibition of SHH signaling component GLI1 significantly impaired human basal cell specification of ionocytes and ciliated cells but significantly enhanced specification of secretory cells. By contrast, activation of the SHH pathway effector smoothened (SMO) with the chemical agonist SAG significantly enhanced ionocyte specification. The abundance of CFTR+ BSND+ ionocytes under these conditions had a direct relationship with CFTR-mediated currents in differentiated air-liquid interface (ALI) airway cultures. These findings were corroborated in ferret ALI airway cultures generated from basal cells in which the genes encoding the SHH receptor PTCH1 or its intracellular effector SMO were genetically ablated using CRISPR-Cas9, causing aberrant activation or suppression of SHH signaling, respectively. These findings demonstrate that SHH signaling is directly involved in airway basal cell specification of CFTR-expressing pulmonary ionocytes and is likely responsible for enhanced ionocyte abundance in the CF proximal airways. Pharmacologic approaches to enhance ionocyte and reduce secretory cell specification after CFTR gene editing of basal cells may have utility in the treatment of CF.

Hedgehog pathway and its inhibitors in chronic obstructive pulmonary disease (COPD)

COPD affects millions of people and is now ranked as the third leading cause of death worldwide. This largely untreatable chronic airway disease results in irreversible destruction of lung architecture. The small lung hypothesis is now supported by epidemiological, physiological and clinical studies. Accordingly, the early and severe COPD phenotype carries the most dreadful prognosis and finds its roots during lung growth. Pathophysiological mechanisms remain poorly understood and implicate individual susceptibility (genetics), a large part of environmental factors (viral infections, tobacco consumption, air pollution) and the combined effects of those triggers on gene expression. Genetic susceptibility is most likely involved as the disease is severe and starts early in life. The latter observation led to the identification of Mendelian inheritance via disease-causing variants of SERPINA1 - known as the basis for alpha-1 anti-trypsin deficiency, and TERT. In the last two decades multiple genome wide association studies (GWAS) identified many single nucleotide polymorphisms (SNPs) associated with COPD. High significance SNPs are located in 4q31 near HHIP which encodes an evolutionarily highly conserved physiological inhibitor of the Hedgehog signaling pathway (HH). HHIP is critical to several in utero developmental lung processes. It is also implicated in homeostasis, injury response, epithelial-mesenchymal transition and tumor resistance to apoptosis. A few studies have reported decreased HHIP RNA and protein levels in human adult COPD lungs. HHIP^+/- murine models led to emphysema. HH pathway inhibitors, such as vismodegib and sonidegib, are already validated in oncology, whereas other drugs have evidenced in vitro effects. Targeting the Hedgehog pathway could lead to a new therapeutic avenue in COPD. In this review, we focused on the early and severe COPD phenotype and the small lung hypothesis by exploring genetic susceptibility traits that are potentially treatable, thus summarizing promising therapeutics for the future.

The Nicotinic Receptor Polymorphism rs16969968 Is Associated with Airway Remodeling and Inflammatory Dysregulation in COPD Patients

Genome-wide association studies unveiled the associations between the single nucleotide polymorphism rs16969968 of CHRNA5, encoding the nicotinic acetylcholine receptor alpha5 subunit (α5SNP), and nicotine addiction, cancer, and COPD independently. Here, we investigated α5SNP-induced epithelial remodeling and inflammatory response in human COPD airways. We included 26 α5SNP COPD patients and 18 wild-type α5 COPD patients in a multi-modal study. A comparative histologic analysis was performed on formalin-fixed paraffin-embedded lung tissues. Isolated airway epithelial cells from bronchial brushings were cultivated in the air-liquid interface. Broncho-alveolar fluids were collected to detect inflammatory mediators. Ciliogenesis was altered in α5SNP COPD bronchial and bronchiolar epithelia. Goblet cell hyperplasia was exacerbated in α5SNP small airways. The broncho-alveolar fluids of α5SNP COPD patients exhibited an increase in inflammatory mediators. The involvement of the rs16969968 polymorphism in airway epithelial remodeling and related inflammatory response in COPD prompts the development of innovative personalized diagnostic and therapeutic strategies.

Hedgehog Signaling: Linking Embryonic Lung Development and Asthmatic Airway Remodeling

The development of the embryonic lung demands complex endodermal–mesodermal interactions, which are regulated by a variety of signaling proteins. Hedgehog (Hh) signaling is vital for lung development. It plays a key regulatory role during several morphogenic mechanisms, such as cell growth, differentiation, migration, and persistence of cells. On the other hand, abnormal expression or loss of regulation of Hh signaling leads to airway asthmatic remodeling, which is characterized by cellular matrix modification in the respiratory system, goblet cell hyperplasia, deposition of collagen, epithelial cell apoptosis, proliferation, and activation of fibroblasts. Hh also targets some of the pathogens and seems to have a significant function in tissue repairment and immune-related disorders. Similarly, aberrant Hh signaling expression is critically associated with the etiology of a variety of other airway lung diseases, mainly, bronchial or tissue fibrosis, lung cancer, and pulmonary arterial hypertension, suggesting that controlled regulation of Hh signaling is crucial to retain healthy lung functioning. Moreover, shreds of evidence imply that the Hh signaling pathway links to lung organogenesis and asthmatic airway remodeling. Here, we compiled all up-to-date investigations linked with the role of Hh signaling in the development of lungs as well as the attribution of Hh signaling in impairment of lung expansion, airway remodeling, and immune response. In addition, we included all current investigational and therapeutic approaches to treat airway asthmatic remodeling and immune system pathway diseases.

[Take-home messages from the COPD 2021 biennial of the French Society of Respiratory Diseases. Understanding to so as to better innovate]

INTRODUCTION

The first COPD biennial organized by the French Society of Respiratory Diseases (SPLF) took place on 17 December 2021.

STATE OF THE ART

The objective of the biennial was to discuss current knowledge regarding COPD pathophysiology, current treatments, research development, and future therapeutic approaches.

PERSPECTIVES

The different lecturers laid emphasis on the complexity of pathophysiologic mechanisms including bronchial, bronchiolar and parenchymal alterations, and also dwelt on the role of microbiota composition in COPD pathenogenesis. They pointed out that addition to inhaled treatments, ventilatory support and endoscopic approaches have been increasingly optimized. The development of new therapeutic pathways such as biotherapy and cell therapy (stem cells…) call for further exploration.

CONCLUSIONS

The dynamism of COPD research was repeatedly underlined, and needs to be further reinforced, the objective being to "understand so as to better innovate" so as to develop effective new strategies for treatment and management of COPD.

Hedgehog Signaling Pathway Orchestrates Human Lung Branching Morphogenesis

The Hedgehog (HH) signaling pathway plays an essential role in mouse lung development. We hypothesize that the HH pathway is necessary for branching during human lung development and is impaired in pulmonary hypoplasia. Single-cell, bulk RNA-sequencing data, and human fetal lung tissues were analyzed to determine the spatiotemporal localization of HH pathway actors. Distal human lung segments were cultured in an air-liquid interface and treated with an SHH inhibitor (5E1) to determine the effect of HH inhibition on human lung branching, epithelial-mesenchymal markers, and associated signaling pathways in vitro. Our results showed an early and regulated expression of HH pathway components during human lung development. Inhibiting HH signaling caused a reduction in branching during development and dysregulated epithelial (SOX2, SOX9) and mesenchymal (ACTA2) progenitor markers. FGF and Wnt pathways were also disrupted upon HH inhibition. Finally, we demonstrated that HH signaling elements were downregulated in lung tissues of patients with a congenital diaphragmatic hernia (CDH). In this study, we show for the first time that HH signaling inhibition alters important genes and proteins required for proper branching of the human developing lung. Understanding the role of the HH pathway on human lung development could lead to the identification of novel therapeutic targets for childhood pulmonary diseases.

Impaired Ciliary Beat Frequency and Ciliogenesis Alteration during Airway Epithelial Cell Differentiation in COPD

Chronic obstructive pulmonary disease (COPD) is a frequent respiratory disease. However, its pathophysiology remains partially elucidated. Epithelial remodeling including alteration of the cilium is a major hallmark of COPD, but specific assessments of the cilium have been rarely investigated as a diagnostic tool in COPD. Here we explore the dysregulation of the ciliary function (ciliary beat frequency (CBF)) and differentiation (multiciliated cells formation in air-liquid interface cultures) of bronchial epithelial cells from COPD (n = 17) and non-COPD patients (n = 15). CBF was decreased by 30% in COPD (11.15 +/- 3.37 Hz vs. 7.89 +/- 3.39 Hz, p = 0.037). Ciliary differentiation was altered during airway epithelial cell differentiation from COPD patients. While the number of multiciliated cells decreased (p < 0.005), the number of primary ciliated cells increased (p < 0.05) and primary cilia were shorter (p < 0.05). Altogether, we demonstrate that COPD can be considered as a ciliopathy through both primary non-motile cilia modifications (related to airway epithelial cell repair and remodeling) and motile cilia function impairment (associated with decrease sputum clearance and clinical respiratory symptoms). These observations encourage considering cilia-associated features in the complex COPD physiopathology and highlight the potential of cilia-derived biomarkers for diagnosis.

Primary ciliogenesis is a crucial step for multiciliated cell determinism in the respiratory epithelium

The alteration of the mucociliary clearance is a major hallmark of respiratory diseases related to structural and functional cilia abnormalities such as chronic obstructive pulmonary diseases (COPD), asthma and cystic fibrosis. Primary cilia and motile cilia are the two principal organelles involved in the control of cell fate in the airways. We tested the effect of primary cilia removal in the establishment of a fully differentiated respiratory epithelium. Epithelial barrier integrity was not altered while multiciliated cells were decreased and mucous-secreting cells were increased. Primary cilia homeostasis is therefore paramount for airway epithelial cell differentiation. Primary cilia-associated pathophysiologic implications require further investigations in the context of respiratory diseases.

CiliOPD: a ciliopathy-associated COPD endotype

The pathophysiology of chronic obstructive pulmonary disease (COPD) relies on airway remodelling and inflammation. Alterations of mucociliary clearance are a major hallmark of COPD caused by structural and functional cilia abnormalities. Using transcriptomic databases of whole lung tissues and isolated small airway epithelial cells (SAEC), we comparatively analysed cilia-associated and ciliopathy-associated gene signatures from a set of 495 genes in 7 datasets including 538 non-COPD and 508 COPD patients. This bio-informatics approach unveils yet undescribed cilia and ciliopathy genes associated with COPD including NEK6 and PROM2 that may contribute to the pathology, and suggests a COPD endotype exhibiting ciliopathy features (CiliOPD).