Basic mechanisms of development of airway structural changes in asthma.

Airway remodelling is a complex process that involves all of the component tissues of the airway from the epithelium to the adventitia. Each of the changes has the potential to alter airway physiology so as to promote airway narrowing, hyperresponsiveness and inflammation. Structural changes, such as epithelial metaplasia, airway fibrosis and airway smooth muscle hyperplasia, have been successfully modelled in animals. These models are being extensively characterised and are providing valuable insights into mechanisms that are likely to be quite relevant to human asthma. Remodelling is induced by factors synthesised and secreted both by inflammatory cells and by structural cells, the latter frequently under the influence of the former. While information concerning the genesis of inflammation is abundant, the precise factors responsible for cellular hyperplasia, hypertrophy and altered matrix deposition are far from resolved. Elucidation of these factors will no doubt lead to novel therapies designed to prevent or reverse these changes.