Matusovsky OS, et al. - Researchers evaluated the contractility of the cystic fibrosis (CF) intrapulmonary airway smooth muscle (ASM). For this purpose, they dissected ASM strips from human control and CF intrapulmonary airways, and carried out assessments for methacholine-induced shortening velocity, maximal force, and stress. In maximally methacholine-contracted ASM, they also evaluated isoproterenol responses. Thereafter, they incubated ASM strips for 16 hours with IL-13 and repeat measurements were obtained. With Western blotting, they evaluated myosin light chain kinase (MLCK) expression. For morphometry, immunostaining of airways was performed. In CF, the possible contributor to airway dysfunction could be the combination of an increase in ASM mass, increased MLCK expression, and inflammation-induced β-adrenergic hyporesponsiveness.