Airway Smooth Muscle in Asthma — Not Just More of the Same

Airway smooth-muscle mass is increased in patients with asthma. This increase in muscle mass is quite marked in lung sections from patients who have died of asthma, but bronchial-biopsy studies indicate that even persons with mild-to-moderate asthma have increased airway smooth-muscle mass. Both hypertrophy and hyperplasia appear to contribute to this increase, and it is possible that airway smooth-muscle hyperplasia in asthma stems from the inflammatory milieu surrounding the asthmatic muscle. There are numerous smooth-muscle growth factors present in the asthmatic airway. Indeed, in culture, serum or bronchoalveolar-lavage fluid from patients with asthma causes greater proliferation of human airway smooth-muscle . . .