Therapeutic targets in lung tissue remodelling and fibrosis

Increased myofibroblasts in the small airways, and relationship to remodelling and functional changes in smokers and COPD patients: potential role of epithelial-mesenchymal transition

Introduction

Previous reports have shown epithelial-mesenchymal transition (EMT) as an active process that contributes to small airway fibrotic pathology. Myofibroblasts are highly active pro-fibrotic cells that secrete excessive and altered extracellular matrix (ECM). Here we relate small airway myofibroblast presence with airway remodelling, physiology and EMT activity in smokers and COPD patients.

Methods

Lung resections from nonsmoker controls, normal lung function smokers and COPD current and ex-smokers were stained with anti-human α-smooth muscle actin (SMA), collagen 1 and fibronectin. αSMA⁺ cells were computed in reticular basement membrane (Rbm), lamina propria and adventitia and presented per mm of Rbm and mm² of lamina propria. Collagen-1 and fibronectin are presented as a percentage change from normal. All analyses including airway thickness were measured using Image-pro-plus 7.0.

Results

We found an increase in subepithelial lamina propria (especially) and adventitia thickness in all pathological groups compared to nonsmoker controls. Increases in αSMA⁺ myofibroblasts were observed in subepithelial Rbm, lamina propria and adventitia in both the smoker and COPD groups compared to nonsmoker controls. Furthermore, the increase in the myofibroblast population in the lamina propria was strongly associated with decrease in lung function, lamina propria thickening, increase in ECM protein deposition, and finally EMT activity in epithelial cells.

Conclusions

This is the first systematic characterisation of small airway myofibroblasts in COPD based on their localisation, with statistically significant correlations between them and other pan-airway structural, lung function and ECM protein changes. Finally, we suggest that EMT may be involved in such changes.

Substance P-induced lung inflammation in mice is mast cell dependent

BACKGROUND

Allergic asthma is a common inflammatory lung disease and a major health problem worldwide. Mast cells (MCs) play a key role in the early-stage pathophysiology of allergic asthma. Substance P (SP) functions in neurogenic inflammation by activating MCs, and therefore, it may to participate in the occurrence and development of asthma.

OBJECTIVE

We examined the relationship between SP and lung inflammation, and also whether SP can directly trigger asthma.

METHODS

We measured the number of peripheral blood eosinophils, neutrophils and basophils and evaluated the levels of IgE and SP in blood samples of 86 individuals with allergic asthma. Serum IgE and SP levels were also determined in 29 healthy individuals. C57BL/6 mice were subjected to different doses of SP, and bronchoalveolar lavage fluid (BALF) was collected to count the inflammatory cells. Lung tissues were analysed using histopathological methods to evaluate lung peribronchial inflammation, fibrosis and glycogen deposition. Levels of IgE, interleukin (IL)-1, IL-2, IL-4, IL-5, IL-13, IL-17 and IFN-γ were determined in mouse serum.

RESULTS

Substance P levels were increased in the serum samples of patients with asthma. SP induced mouse lung peribronchial inflammation, fibrosis and glycogen deposition, with high levels of Th2-related cytokines such as IL-4, IL-5 and IL-13 observed in the BALF. Furthermore, low level of total IgE was noted in the serum, and SP had little effect on MC-deficient kit^W-sh/W-sh mice.

CONCLUSIONS & CLINICAL RELEVANCE

Substance P levels increased significantly in serum of asthmatic patients and independently associated with the risk of asthma. Furthermore, SP induced Th2 lung inflammation in mice, which was dependent on MCs.

Tezepelumab: A Potential New Biological Therapy for Severe Refractory Asthma

Thymic stromal lymphopoietin (TSLP) is an innate cytokine, belonging to the group of alarmins, which plays a key pathogenic role in asthma by acting as an upstream activator of cellular and molecular pathways leading to type 2 (T2-high) airway inflammation. Released from airway epithelial cells upon tissue damage induced by several noxious agents including allergens, viruses, bacteria, and airborne pollutants, TSLP activates dendritic cells and group 2 innate lymphoid cells involved in the pathobiology of T2-high asthma. Tezepelumab is a fully human monoclonal antibody that binds to TSLP, thereby preventing its interaction with the TSLP receptor complex. Preliminary results of randomized clinical trials suggest that tezepelumab is characterized by a good safety and efficacy profile in patients with severe, uncontrolled asthma.