Background: Submucosal hypervascularity is part of airway remodeling in patients with asthma; however, its existence in the small airways and its contribution to airflow limitation remain controversial.
Methods: We investigated bronchial wall vascularity and angiogenic cells between medium airways (inner diameter, 2 to 5 mm) and small airways (inner diameter, < 2 mm) in patients with asthma (n = 9) and COPD (n = 11), and in 8 control subjects. The lung specimens obtained during surgery were immunostained to detect CD31, CD34, vascular endothelial growth factor, and basic fibroblast growth factor.
Results: The number of vessels in both the medium and small airways in patients with asthma was significantly (p < 0.01) increased compared to those in patients with COPD and control subjects, and the percentage of vascularity was significantly (p < 0.01) increased in the medium airways in asthma patients and in the small airways in COPD patients. Patients with moderate asthma showed a greater increase in vascularity than those with mild asthma (p < 0.01), and the number of angiogenic factor-positive cells increased in asthma patients compared with control subjects. In asthmatic subjects, inverse correlations were found between FEV(1) percentage of predicted and the number of vessels (r = -0.85; p < 0.01), or the percentage of vascularity (r = -0.72; p < 0.03) in the inner area of the medium airways, but they were not found for the small airways. In COPD patients, no correlations were demonstrated.
Conclusions: The number of vessels in the medium and small airways in asthma patients shows a greater increase than those in COPD patients, and the vascular area in the small airways is increased in COPD patients but not in asthma patients. Enhanced vascularity in the inner area of the medium airways, but not in the small airways, might contribute to airflow limitation in asthma patients.