The role of bronchoconstriction in the development of airway remodelling and its effects upon lung function

Project background

Asthma is an inflammatory disease of the airways affecting approximately 5.4 million people in the UK. The severity of the disease varies in patients with the majority able to adequately manage symptoms, however there is a subset of patients with severe asthma that are unresponsive to current treatments. One of the key features of severe asthma is the development of structural changes in the airways, termed airway remodelling, but the causes of airway remodelling are poorly understood. Animal models of asthma, typically mice and rats, are often used to further understanding of the disease, particularly when testing potential therapeutics and treatments. These animals do not develop asthma spontaneously so asthma must be induced by administration of an inhaled allergen.

Why we funded it

This David Sainsbury Fellowship aims to reduce the number of mice or rats needed in the study of airway remodelling by using either an ex vivo lung slice culture model or non-invasive imaging techniques to assess both lung function and airway remodelling in animal models of asthma.

The induction of an asthma-like response through administration of an inhaled allergen is classified as a moderate procedure under the Animals (Scientific Procedures) Act. For the study of a single inhibitor, approximately 24 mice would be required for the analysis of four treatment groups where six animals are needed per group for statistical significance. The use of the ex vivo lung slice culture means approximately 30 lung slices can be obtained from a single mouse lung. This allows the study of multiple inhibitors and controls to be analysed using a single animal. Further reduction is possible using imaging techniques as lung function and airway remodelling can be assessed in the same animal, which was previously not possible. The traditional methods of using immunohistochemistry and plethysmography would require a total of 80 animals for one study whereas imaging requires only ten animals per study.

Research methods

Bronchoconstriction, a key feature of asthma, is thought to promote airway remodelling. To investigate this, functional MRI and high-resolution CT imaging will be used in conjunction in rats, allowing the measuring of lung function and lung imaging to be performed in the same animal. Dr Tatler’s research indicates specific integrins have a role in promoting airway remodelling through enhanced TGF-β activation, which will be investigated using the lung slice culture model.1 The precision cut ex vivo lung slice model retains the microstructure of airways and allows for bronchoconstriction to be visualised by microscopy. The lung slices will be stimulated with bronchoconstrictors and assessed for TGF-β activity via Western blot. Protein expression studies and immunohistochemistry will also be used to assess extracellular matrix protein expression, as increased deposition of these proteins contributes to airway remodelling in asthmatic patients. The effect of bronchodilators commonly used clinically on contraction-induced TGF-β and other relevant signalling pathways will also be analysed.

1 Tatler A et al (2011). Integrin αvβ5-mediated TGF-β activation by airway smooth muscle cells in asthma. J Immunol 187(11): 6094-107. doi: 10.4049/jimmunol.1003507.

Hill MR et al. (2018). A theoretical model of inflammation- and mechanotransduction-driven asthmatic airway remodelling. Biomechanics and Modeling in Mechanobiology 17(5):1451-1470. doi: 10.1007/s10237-018-1037-4

John AE et al. (2017). Methods for the Assessment of Active Transforming Growth Factor-β in Cells and Tissues. Methods in molecular biology (Clifton, N.J.) 1627:351-365. doi: 10.1007/978-1-4939-7113-8_23

John AE et al. (2016). Loss of epithelial Gq and G11 signaling inhibits TGFβ production but promotes IL-33-mediated macrophage polarization and emphysema. Science Signaling 9(451):ra104. doi: 10.1126/scisignal.aad5568

Tatler AL et al. (2016). Caffeine inhibits TGFβ activation in epithelial cells, interrupts fibroblast responses to TGFβ, and reduces established fibrosis in ex vivo precision-cut lung slices. Thorax 71(6):565-7. doi: 10.1136/thoraxjnl-2015-208215

Tatler AL et al. (2016). Reduced Ets domain-containing protein Elk1 promotes pulmonary fibrosis via increased Integrin αvβ6 expression. J Biol Chem 291(18):9540-53. doi: 10.1074/jbc.M115.692368

Clifford RL et al. (2015). CXCL8 histone H3 acetylation is dysfunctional in airway smooth muscle in asthma: regulation by BET.  Am J Physiol Lung Cell Mol Physiol 308(9):L962-72. doi: 10.1152/ajplung.00021.2015 

Lilburn DM et al. (2015). Investigating lung responses with functional hyperpolarized xenon-129 MRI in an ex vivo rat model of asthma. Magn Reson Med 2015 Oct 28. doi: 10.1002/mrm.26003

Tatler AL, Jenkins G (2015). Reducing affinity of αvβ8 interactions with latent TGFβ: dialling down fibrosis. Ann Transl Med 3(Suppl 1): S31. doi: 10.3978/j.issn.2305-5839.2015.02.18

Tatler AL, Jenkins G (2015). Sphingosine-1-phosphate metabolism: can its enigmatic lyase promote the autophagy of fibrosis? Thorax 70(12):1106-7. doi: 10.1136/thoraxjnl-2015-207974

Noble PB et al. (2014). Airway smooth muscle in asthma: linking contraction and mechanotransduction to disease pathogenesis and remodelling. Pulm Pharmacol Ther 29(2):96-107. doi: 10.1016/j.pupt.2014.07.005 

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Fellowship

Status

Closed

Principal investigator

Dr Amanda Tatler

Institution

University of Nottingham

Grant reference number

NC/K500501/1

Award date

Nov 2012 - Oct 2015

Grant amount

£195,000