Histopathologic and Morphometric Evaluation of the Nasal and Pulmonary Airways of Cats with Experimentally Induced Asthma

Abstract

Background: Allergic rhinitis frequently occurs as a comorbid condition in asthmatic people, suggesting that the upper and lower airways may be immunologically linked. Our research group has developed an experimental aeroallergen model of asthma in cats. We hypothesized that aeroallergen sensitization and challenge would induce morphologic changes in the nasal airways of cats that mimic those observed in the bronchial airways. Methods: Five mixed breed cats were sensitized to Bermuda grass allergen and then serially challenged with aerosolized Bermuda grass allergen to induce an asthmatic phenotype. Four control cats were similarly treated with saline vehicle. Nasal tissues and lungs were processed for histopathological and morphometric analyses. Results: Eosinophilic inflammation, epithelial hypertrophy and mucous cell metaplasia were observed along the pulmonary axial airway mucosa of allergen-sensitized (asthmatic) cats. Mild eosinophilic inflammation was observed in the nasal airways of asthmatic cats. This alteration was confined primarily to the anterior nasal cavity, resulting in an increase in tissue eosinophils at this site compared to controls (p < 0.05). A marked increase in tissue mast cells was observed throughout all regions of the nasal airways of asthmatic cats compared to control cats (p < 0.05). There was no difference in intraepithelial mucosubstances between the nasal airways of controls and asthmatic cats. There was no correlation between upper and lower airway eosinophils or mast cells. Conclusion: Cats with experimentally induced asthma exhibit morphologic changes in the nasal airways that are distinct from the alterations observed in the lungs. These results are similar to those observed in people with comorbid asthma and allergic rhinitis.

Immunohistochemical Analysis of Leucocyte Subsets in the Sinonasal Mucosa of Cats with Upper Respiratory Tract Aspergillosis

“…In healthy dogs, NALT has not been identified and epithelial MHC class II expression is rare (Peeters et al, 2005b), while both of these characteristics are common in horses (Banks et al, 1999;Liebler-Tenorio and Pabst, 2006;Quintana et al, 2011) in the absence of respiratory disease. NALT has been previously reported in cats in the absence of upper respiratory tract disease (Venema et al, 2013). In the present study NALT was not identified and MHCII expression was also common in cats in the absence of URT disease.…”

“…In the present study NALT was not identified and MHCII expression was also common in cats in the absence of URT disease. The absence of detectable NALT in the present study is likely due to anatomical differences in sampling, since NALT was previously detected in the caudal nasal cavity and nasopharyngeal meatus, which were not sampled in the current study (Venema et al, 2013).…”

Clinical features and radiographic findings in cats with eosinophilic, neutrophilic, and mixed airway inflammation (2011‐2018)

“…One previous study 3 found upper respiratory tract signs in 25% of cats diagnosed with asthma or bronchitis whereas another 13 reported nasal discharge more often in cats with chronic bronchitis than in those with asthma. An association of asthma with upper respiratory viruses has been noted in children, 37,38 and nasal airways in cats with experimentally induced asthma were noted to have eosinophilic infiltration in the absence of clinical signs 39 . Whether this finding was related to the method of hypersensitization via aerosolized allergen in the experimental study or represented a distinct response of the upper respiratory epithelium in those cats is unclear.…”

The computed tomographic “tree‐in‐bud” pattern: Characterization and comparison with radiographic and clinical findings in 36 cats

“…Cats could have had two unrelated diseases leading to rhinitis and lower airway disease. Another possibility is the “united airways theory” which in humans and an experimental model of feline allergic asthma suggests an immunologic link to explain the comorbid conditions of rhinitis and allergic asthma . A third possibility is postnasal drip leading to chronic aspiration and chronic bronchitis with potential bronchial plugging.…”