Summary
Airway remodelling is a relatively new concept in asthma research. It can be defined as the ‘structural changes in the airways that may affect their functional properties’. The structural changes usually comprise smooth muscle hyperplasia, hypertrophy of mucus glands, subepithelial fibrosis, angiogenesis and changes to the extracellular matrix. One of the most important consequences of these changes is narrowing of the airway lumen. The aetiology of remodelling has not been elucidated fully, but it is clear that there is an important association between remodelling and inflammation. However, the degree to which one process causes the other, and the nature of the causality, is not known. Numerous cells and mediators including epithelial cells, cytokines and growth factors all appear to play a part in the remodelling process, but the precise roles of specific cells and mediators are yet to be defined clearly. Because of the problems in assessing the extent of remodelling in living patients, research into the clinical consequences of this process has been difficult. However, it is clear that the extent of remodelling correlates with the severity of asthma, and patients with extensive remodelling may also be resistant to steroid treatment. It is not clear whether remodelling is generally reversible, although there is evidence that it is in some patients, and this reversal is associated with improvement in symptoms. However, remodelling represents an important target for the development of future drugs to treat asthma, and pharmacological treatment that could reverse the process of remodelling has the potential to play a key role in asthma management.