BRONCHIAL ELASTIC FIBERS IN NORMAL SUBJECTS AND ASTHMATIC-PATIENTS

Elastic fibers required to maintain bronchial patency during ventilati on may be damaged in asthma as a result of repair following inflammati on or stretching during exacerbations. Fifteen normal subjects and 40 asthmatics of variable severity were studied. Bronchial biopsies were obtained from a subsegmental bronchus using a flexible bronchoscope. T he elastic fibers were examined using orceine-eosine staining and/or i mmunohistochemistry with two monoclonal antibodies against elastin or transmission electron microscopy (six asthmatics and four control subj ects). Orceine-eosine staining revealed that most normal subjects had normal fibers throughout the submucosa whereas of the 21 asthmatics an alyzed only three had a normal superficial elastin network. In five pa tients, elastin had virtually disappeared. In the remaining patients, fibers appeared fragmented. The deeper layer of elastic fibers was abn ormal in 17 asthmatics, fibers being patchy, tangled, and thickened. T he fragmentation of the superficial network of elastic fibers shown in asthmatics was confirmed by immunohistochemistry. Electron microscopy studies suggested that the elastinolytic process and fragmentation of elastic fibers occurred in asthmatics. Elastinolysis occurs in the ai rways of asthmatics possibly as a result of repair elicited by chronic inflammation. Mechanical stretch induced by breathing and edema may l ead to the fragmentation of fibers in asthmatic airways.