Neutrophil dynamics in idiopathic pulmonary fibrosis

Crowley, Louise Elizabeth ORCID: 0000-0001-6261-5041 (2025). Neutrophil dynamics in idiopathic pulmonary fibrosis. University of Birmingham. Ph.D.

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Abstract

Introduction: The pathophysiological drivers of epithelial damage and fibrosis in idiopathic pulmonary fibrosis (IPF) remain poorly understood. Novel therapeutic targets need to be identified to improve patient management. Neutrophils are the most common immune cells in the body and are critical responders to tissue injury; housing an array of enzymes critical for repair and remodelling. However, the role of neutrophils in IPF development and progression remains unknown.

Hypotheses: This thesis describes experiments which explored the following three hypotheses: 1) does the pro-fibrotic cytokine, transforming growth factor-beta 1 (TGFβ1), drive neutrophil chemotaxis; 2) do circulating neutrophils from patients with IPF display a primed phenotype and altered migratory and effector functions; 3) are neutrophils and their products resident in fibrotic lung tissue.

Results: Chapter Four demonstrates using ex vivo neutrophil migration and chemotaxis assays (validated in Chapter Three) that TGFβ1 increases neutrophil chemokinesis (direction independent movement), but not chemotaxis. This likely represents neutrophils transitioning into a primed state, with TGFβ1 also amplifying movement responses to classical chemoattractants.

Chapter Five outlines the development of the prospective cohort study entitled ‘The Hypoxic Burden in Interstitial Lung Diseases (HYBRID)’, which allowed the assessment of phenotype and function of circulating neutrophils derived from IPF patients, as well as the measurement of day and nighttime oximetry. The latter was of relevance as hypoxia has been implemented in neutrophil dysfunction in this disease. The 16 control and 26 IPF participants recruited to this study were well matched. IPF participants were mostly of mild to moderate disease severity and experienced an increased frequency of episodic hypoxaemia.

Chapter Six describes the characterisation of circulating neutrophils derived from IPF and control participants of the HYBRID study. IPF patients had a greater circulating neutrophil count than control participants and a higher percentage of CD10 negative neutrophils, suggesting an expansion of immature neutrophil populations and emergency granulopoiesis. There was no evidence that IPF derived neutrophils were in a primed state. However, TGFβ1 appeared to drive IPF neutrophils to move less directly than control neutrophils. Furthermore, provisional analysis of bronchoalveolar lavage fluid samples was suggestive of increased NETs in IPF samples. Further expansion of this project is needed to improve the statistical power of this work.

Chapter Seven describes the development of a multiplex immunofluorescence panel to allow the localisation of neutrophils within IPF lung tissue. Descriptive analyses of the staining is described here; confirming the presence of neutrophils and their contents (neutrophil elastase and neutrophil extracellular traps) in the alveolar spaces and interstitium of IPF lung tissue.

Conclusions: This thesis highlights for the first time that there appears to be alterations in the phenotype of circulating neutrophils in IPF patients, and confirms the presence of neutrophils within fibrotic lung tissue using state-of-the-art multiplex technology. Future IPF research requires detailed characterisation of neutrophil activity in the pulmonary environment, for example using multiplex technology as described here, to aid discovery of novel therapeutic targets for this condition.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):