mechanisms of airway remodeling in asthma

Asthma is a chronic inflammatory disease characterized by reversible airflow limitation and airway hyperresponsiveness. Persistent inflammation in airway tissues may lead to structural changes known as airway remodeling and consequently airway obstruction that is not fully reversible and progressive loss of lung function over time. It is generally accepted that airway remodeling is closely related to progression of airway hyperresponsiveness, and the severity of asthma. The structural changes observed in chronic persistent asthma, which includes airway smooth muscle hypertrophy and hyperplasia, collagen deposition to sub-epithelial basement membrane, hyperplasia of goblet cells, thickening of airway mucosa and an increase in vascularity, are derived from airway inflammation. For instance, the thickened airway mucosa might be produced by cytokines and growth factors released from inflammatory cells and airway epithelial cells, and associated with bronchial hyperreactivity and asthma severity. To date, many studies have identified candidate mechanisms and mediators for these observed structural changes, which are thus potential targets in the treatment of asthma. In this review, we describe the recent knowledge of the mechanisms and clinical implications of airway remodeling in asthma.