Increased adventitial thickening is a feature of pulmonary arterial remodeling in cats with bronchiolar disorders

To compare pulmonary arterial remodeling in cats with histopathologic diagnosis of bronchiolar disorder (BD) to control cats without BD.

Lung tissue from cats with primary or secondary BD (n = 13) were compared to control cats without histopathological evidence of pulmonary and cardiac disease (n = 13). Wall-to-lumen ratio scores, wall cross-sectional area, and intimal, medial, and adventitial tunic areas were compared between groups for small (70 to 300 μm), medium (301 to 999 μm), and large (≥ 1,000 µm) pulmonary arteries. Analysis used linear or linear mixed models and γ-log or arcsine distributions. Post hoc tests were performed, when applicable, with the Tukey method. Benjamini-Hochberg corrections were applied to multiple pairwise comparisons.

Remodeling of pulmonary arteries was found in both groups, affecting more small pulmonary arteries, medium pulmonary arteries, and large pulmonary arteries, in that order. Pulmonary arterial remodeling in cats without BD consisted of medial hypertrophy and occasional intimal fibrosis. While having changes to the intima and media, cats with BD also showed increased adventitial collagen. No significant differences were noted between groups for wall-to-lumen scores and wall cross-sectional area for all 3 categories of arteries. Adventitial area was, on average, 1.3-fold larger in cats with BD compared to controls (P = .012), whereas no difference was found for intimal and medial areas between groups (P = .05).

The results show that cats with BD have a thicker adventitial tunic than control cats.

The adventitial tunic of pulmonary arteries may represent a potential target for therapy in cats with BD.