Myofibroblast and elastic and collagen fiber hyperplasia in the bronchial mucosa: a possible basis for the progressive irreversibility of airway obstruction in chronic asthma.

Considering the role proposed for myofibroblasts in inflammatory and hyperelastotic lung diseases, the possibility arises that these cells are involved in bronchial pathology, including asthma. To address this issue, we have analyzed by light microscopy, histochemistry and immunohistochemistry the structure of extra- and intra-pulmonary bronchi of patient died of asthma. We have demonstrated hyperplasia of connective tissue cells and fibers in the mucosa, all around the lumen of extra- and intra-pulmonary bronchi. The cells were thin and elongated, labeled by anti-actin and anti-vimentin antibodies and interspersed with many elastic and collagen fibers, therefore they were interpreted as myofibroblasts. These findings may explain the rigidity of the bronchial wall in patients with asthma, which causes the progressively more limited resolution of airway obstruction upon pharmacological treatment and the gross anatomical finding of bronchial stiffness at inspection of the lungs. The possibility should also be considered that myofibroblasts and elastic--not collagen--fibers have contributed to bronchial hyperreactivity at an early stage of the disease.