Airway remodeling in horses with mild and moderate asthma

Abstract 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 μm2/μm [34‐57 μm2/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 μm2/μm [21‐80 μm2/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.