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Pathologic changes in 3-methylindole-induced equine bronchiolitis
Abstract:
The pathologic features of bronchiolitis were studied in horses and ponies from 30 minutes to 27 days after an oral dose of 3-methylindole (3MI). From 30 minutes to 3 hours, lesions were limited to nonciliated bronchiolar epithelial (Clara) cells, which lost apical caps and cytoplasmic granules and had dilated smooth endoplasmic reticulum (SER). At 12 hours, necrotic Clara cells were exfoliated; degeneration and necrosis were evident, in bronchiolar ciliated cells. Rare epithelial cells with hyperplastic SER appeared on the denuded basal lamina at 24 hours. Inflammatory cells, epithelia, fibroblastlike cells, collagen, and debris occluded many bronchiolar lumens from 3 to 6 days. Reorganization resulted in a simple columnar bronchiolar epithelium with relatively normal ciliated cells and fewer fibroblastlike cells. However, mature Clara cells were rare at 27 days, and collagenous bands still divided bronchiolar lumens. Thus, 3MI toxicosis is a persistent model of equine bronchiolitis with many morphologic features of the spontaneous disease.
Insights
3-methylindole (3MI) causes persistent equine bronchiolitis, damaging Clara cells and leading to long-term airway changes. This study models spontaneous equine respiratory disease, highlighting lasting lung injury.
Area of Science:
- Veterinary Pathology
- Equine Respiratory Diseases
- Toxicology
Background:
- Equine bronchiolitis is a significant respiratory condition in horses.
- Understanding the pathogenesis of equine bronchiolitis is crucial for effective treatment and prevention.
- 3-methylindole (3MI) is a known toxin that can induce respiratory damage in horses.
Purpose of the Study:
- To investigate the sequential pathologic features of 3-methylindole-induced bronchiolitis in horses.
- To establish 3MI toxicosis as a persistent model for studying spontaneous equine bronchiolitis.
Main Methods:
- Horses and ponies were administered an oral dose of 3-methylindole (3MI).
- Bronchiolar tissues were examined at various time points, from 30 minutes to 27 days post-administration.
- Histopathologic evaluation focused on cellular and structural changes within the bronchioles.
Main Results:
- Early lesions (30 minutes to 3 hours) involved damage to nonciliated bronchiolar epithelial (Clara) cells, characterized by loss of apical caps, cytoplasmic granules, and smooth endoplasmic reticulum (SER) dilation.
- By 12 hours, necrotic Clara cells were exfoliated, and ciliated cells showed degeneration and necrosis.
- Inflammatory cells, epithelial changes, fibroblast proliferation, collagen deposition, and debris occluded bronchiolar lumens from 3 to 6 days, with persistent changes like rare mature Clara cells and collagen bands observed at 27 days.
Conclusions:
- 3-methylindole toxicosis serves as a persistent and relevant model for equine bronchiolitis.
- The study demonstrates significant, long-lasting morphologic changes in the equine bronchioles following 3MI exposure.
- These findings provide insights into the pathogenesis of spontaneous equine respiratory diseases.
