Airway smooth muscle cell proliferation is increased in asthma

Increased airway smooth muscle (ASM) within the bronchial wall of asthmatic patients has been well documented and is likely to be the result of increa sed muscle proliferation. We have for the first time been able to culture A SM cells from asthmatic patients and to compare their proliferation rate wi th that of nonasthmatic patients. Asthmatic ASM cell cultures (n = 12) were established from explanted lungs and endobronchial biopsies. Nonasthmatic ASM cells (n = 10) were obtained from explanted tissue from patients with n o airway disease, emphysema, carcinoma, and fibrosing alveolitis. Cell coun ts, tritiated thymidine incorporation, and cell cycle analysis were conduct ed over 7 d. Asthmatic ASM cell numbers at Days 3, 5, and 7 were significan tly higher than corresponding values for nonasthmatic cells (p < 0.05). Tri tiated thymidine incorporation was increased 3.2-fold in asthmatic cells co mpared with nonasthmatic cells within the first 24 h (p = 0.026). Flow cyto metric analysis of DNA content on Days 1 and 2 revealed that a significantl y greater percentage of asthmatic ASM cells were in the G2 + M phase (p < 0 .05). This study shows for the first time that proliferation of ASM cells i s increased in patients with asthma and provides evidence for an intrinsic abnormality in the ASM cell in this disease.