Innate immune cells, such as macrophages, are trained by the unique microenvironment of the tissue they occupy. This tissue influence can include the extracellular matrix, the presence of inflammatory stimuli or signals and, in some tissues, the microbiota. Most studies, however, have examined such tissue specific training in health whereas little is known about the possibility of immune re-training in the lung following acute inflammation. The lung extracellular matrix is important for mechanical stability and structural support, as well as influencing inflammation via altering cell adhesion, migration, survival, proliferation and differentiation. Matrix alterations are a feature of a number of significant chronic respiratory diseases that carry high clinical unmet need. These include idiopathic pulmonary fibrosis, cystic fibrosis and chronic obstructive pulmonary disease (COPD). On the other hand, the impact on matrix after acute inflammation and whether it is returned to its pre-infection state is relatively unexplored. In murine models, macroscopic examination of the lung following acute inflammation implies a return to a reasonable homeostatic state. However, using more sensitive techniques, we now show that this is not the case. In this thesis we test the premise that a more thorough interrogation of lung extracellular matrix by mass spectrometry will reveal long term alterations that are not visible by histology. After influenza virus infection, we demonstrate that heightened extracellular matrix persists in the lung tissue, often forming structures that were not present in health. Furthermore, basement membrane components, for example collagen IV and laminin, are reduced. In vitro investigations show that individual extracellular matrix components affect lung macrophage activity. For example, hyaluronan and fibronectin alter macrophage expression of microRNA species known to influence toll-like receptor responsiveness and fibrosis. We also describe an alteration in microRNA species in response to influenza virus infection as well as a non-infectious model of pulmonary inflammation using carbon nanotubes. Collectively, this implies that altered matrix composition impacts on the inflammatory tone of the lung innate immune system. It is therefore feasible that such changes following severe lung inflammation could be overcome by targeting abnormal matrix production or degradation.
|Date of Award||1 Aug 2018|
- The University of Manchester
|Supervisor||Mark Travis (Supervisor) & Tracy Hussell (Supervisor)|
- Carbon Nanotubes
- Mass Spectrometry