The airway longitudinal elastic fiber network and mucosal folding in patients with asthma

A submucosal network of elastic fibers in a collagen and myofibroblast matr ix form discrete longitudinal bundles (LB) in the bronchial tree. The LB ma y affect airway function by altering the mechanical properties of the airwa y wall or by changing the folding behavior of the airway mucosa. The area a nd number of LB were quantified from 12 cases each of fatal asthma (FA), no nfatal asthma (NF), and nonasthmatic (NA) control cases on elastic-trichrom e stained airways. The effects of group, sex, age, and smoking were examine d using multiple linear regression. The area fraction of LB increased (p < 0.05) approximately twofold in cases of FA compared with NA control cases i n both large and small airways. The areas of LB were increased in smokers, older subjects, and men (p < 0.05). The number of mucosal folds was related to the number of longitudinal bundles in asthmatics and nonasthmatics and was not different between groups. Collagen and myofibroblasts were increase d (p < 0.05) in LB of FA and NF cases compared with NA control cases. The i ncreased size and altered composition of LB in asthma may influence airway function; however, excessive airway narrowing in asthma is not due to alter ed numbers of mucosal folds.