Smooth muscle hypertrophy in distal airways of sensitized infant rhesus monkeys exposed to house dust mite allergen

Summary Background Airway smooth muscle hypertrophy is closely associated with the pathophysiology of hyper‐reactive airways in allergic asthma. Objective To determine whether repeated exposure to allergens during postnatal lung development promotes remodelling of airway smooth muscle. Methods Infant, male rhesus monkeys (30‐day‐old) were sensitized to house dust mite allergen (HDMA) and then exposed to HDMA aerosol periodically over 5 months. Smooth muscle mass and bundle size and abundance in conducting airways were measured and compared with age‐matched control (filtered air‐exposed) monkeys. Results Total smooth muscle mass and average bundle size were significantly greater in the conducting airways of monkeys exposed to HDMA. Smooth muscle bundle abundance was not affected by exposure to HDMA. Conclusion Repeated cycles of allergen exposure alter postnatal morphogenesis of smooth muscle, affecting both total mass and bundle size, in conducting airways of infant monkeys.