Asthma is a chronic inflammatory disorder characterised by three hallmark features: airway inflammation, remodelling and hyperresponsiveness. Pathological airway remodelling in asthma is typically described as increased smooth muscle bulk, mucus hypersecretion and heightened ECM deposition and reorganisation, which together with other features, propagate narrowing of the airway lumen and airflow obstruction. The ECM was previously thought to be an inert tissue and cellular scaffold, but it is now recognised as a highly dynamic structure which is intertwined with the immune system. For decades, research into asthma pathology has primarily focused on the underlying changes to the immune system rather than the mechanisms driving structural changes leading to irreversible lung function decline. Chitinase-like proteins (CLPs) are highly upregulated during allergic airway pathology and have been associated with the development of asthma, poor disease control, neutrophilic inflammation and airway remodelling. Generally, CLPs regulate aspects of immunity, tissue repair and physically interact with ECM components. Despite the notable upregulation of CLPs during allergic airway pathology, the mechanistic function of CLPs here has remained largely unexplored. The aim of this research project was to investigate how the lung immuno-matrix environment changes following pathology and whether CLPs influence ECM remodelling. We firstly aimed to characterise the human lung immuno-matrix during disease. Using human lung resection material, distinct cellular matrix environments in the lung were spatially defined and found to be differentially altered across healthy, asthma and COPD settings. Specifically, macrophages and fibroblasts were spatially rearranged relative to ECM components such as fibronectin and collagen IV. Using these human lung sections, we also demonstrated that human CLP YKL-40 was expressed by many lung cells which underwent spatial reorganisation in different pathological settings including macrophages, neutrophils and fibroblasts. To investigate the relationship between CLPs and the lung immuno-matrix in greater detail, manipulatable murine models were employed. By using a mixed-allergen model in novel CLP-deficient mice, we demonstrated that knockout of Ym1 and Ym2, the dominant murine CLPs, had no clear impact on the generation of an allergic immune response. Yet, allergen-induced airway remodelling did not develop to the same extent in Ym1-deficient mice compared to wild-type mice, as assessed by immuno-staining for ECM markers, airway smooth muscle and fibroblasts. We then demonstrated that CLP-deficient mice exhibited transcriptional changes to genes associated with ECM regulation as well as altered spatial organisation of stromal cells by utilising flow cytometry, spatial single cell analysis and transcriptomic analysis. Collectively, data presented in this thesis highlighted that the human lung had distinct immuno-matrix environments which were altered under different pathological conditions. Amongst cells which were spatially reorganised during disease were many which expressed human CLP YKL-40. Further investigation into murine CLPs Ym1 and Ym2 demonstrated that CLPs regulate ECM remodelling around the airway in response to inhaled allergens. Detailed spatial and transcriptomic analysis highlighted that during CLP deficiency, the organisation of stromal cells was altered as well as the expression of matrisome-associated genes in the lung. These data cement that the specific mechanisms by which CLPs regulate ECM deposition around the airway requires further exploration to understand the development of airway remodelling during disease and ways in which the lung immuno-matrix can be reverted to a healthy state.
- Allergic Inflammation
- Airway Remodelling
- Chitinase-like proteins
- Asthma
- Extracellular Matrix
Investigating the influence of chitinase-like proteins on lung extracellular matrix remodelling during allergic airway inflammation.
Tompkins, H. (Author). 1 Aug 2025
Student thesis: Phd