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.