[Effect of inhaled corticosteroids on airway remodeling in patients with mild asthma]

Objective: To evaluate the effect of inhaled corticosteroids on airway remodeling in patients with mild asthma. Methods: In this single-arm, open-label, single-center, prospective exploratory study, we enrolled patients with mild asthma from January 2019 to December 2020 at the First Affiliated Hospital of Guangdong Pharmaceutical University. A total of 15 patients with mild asthma were included in this study. There were 6 males and 9 females. The age was (38.6±11.5) years. Fluticasone propionate inhalation aerosol (125 μg) was administered twice daily for 12 months. Pulmonary function tests, high-resolution chest CT, asthma control test (ACT) questionnaires were performed before and after treatment. Airway mucosal biopsies and bronchoalveolar lavage fluid were obtained by bronchoscopy of the right lower lobe to evaluate the airway inflammatory condition. Airway lumen area (Ai), airway wall thickness (Aw%) measured by CT, and the thickness of airway epithelium, basement membrane and smooth muscle measured by pathology were analyzed to evaluate the effect of inhaled corticosteroid on airway remodeling. Pearson or Spearman correlation were used to analyze the correlation among the improvement in lung function, ACT score and the improvement of airway remodeling. Results: The Ai at 3, 4, 5, and 6^th generation of bronchi was increased by 7.5%, 14.4%, 4.1%, and 22.8%, respectively; The Aw% was decreased by 6.1%, 6.7%, 6.5%, and 7%, respectively (all P< 0.05). The average area of airway smooth muscle was 13.3%±8.7% at baseline, and was 11.67% at the 12th month (interquartile range 9%), but the change was not significant (Z=-0.63, P=0.539). The thickness of the basement membrane decreased from (5.19±1.75) μm to (3.83±1.15) μm at the 12th month (Z=-2.38, P=0.019). The thickness of the epithelium decreased from (78.60±13.12) μm to (59.32 ±11.97) μm at 12 month (t=4.20, P<0.001). Changes in Aw%, epithelial and basement membrane thickness at the 12th month were correlated with the improvement in ACT score (all P<0.05). Conclusions: Regular inhalation of corticosteroids for 12 months in patients with mild asthma resulted in reduced airway remodeling, as evidenced by a decrease in the thickness of airway wall, airway mucosal epithelium and basement membrane. The improvement of airway remodeling was significantly associated with the improvement of asthma ACT score. A scientific rationale for inhaled corticosteroids in mild asthma on airway remodeling was provided at the level of morphology and structure.