Airway remodeling in horses with mild and moderate asthma

BACKGROUND: There is a remodeling of the central airways in horses with severe asthma but whether a similar process occurs in horses with the mild or moderate asthma (MMA) is unknown. OBJECTIVES: To evaluate lesions affecting the central airways of horses with MMA. ANIMALS: Twelve horses with MMA and 8 control horses. METHODS: Case‐control retrospective study of horses classified as MMA affected or controls based on history and bronchoalveolar lavage fluid cytology. Endobronchial biopsies were analyzed using histomorphometry and a semiquantitative histologic scoring system. RESULTS: Histomorphometry identified epithelial hyperplasia (47 μm(2)/μm [34‐57 μm(2)/μm]; P = .02), a thickened lamina propria (166 μm [73‐336 μm]; P = .04), and smooth muscle fibrosis (42% [33%‐78%]; P = .04) in horses with MMA when compared to controls horses (24 μm(2)/μm [21‐80 μm(2)/μm]; 76 μm [36‐176 μm]; and 33% [26%‐52%], respectively). The semiquantitative score results indicated, in horses with MMA, the presence of epithelial hyperplasia (7 of the 12 horses with MMA and only 1 of the 8 control horses had a score of 1/1), and submucosal inflammatory leucocytes in the central airway (11 of the 12 horses with MMA and only 4 of the 8 control horses had a score ≥ 1/2). CONCLUSIONS AND CLINICAL RELEVANCE: Tissue remodeling of the bronchial lamina propria, epithelium, and smooth muscle was present in horses with MMA.