Clara cell secretory protein is reduced in equine recurrent airway obstruction.
Authors: Katavolos P, Ackerley C A, Viel L, Clark M E, Wen X, Bienzle D
Journal: Veterinary pathology
Summary
Recurrent airway obstruction (RAO) in horses is characterised by chronic neutrophilic airway inflammation, mucus overproduction, and progressive airway remodelling following repeated exposure to environmental dust and mould, ultimately impairing athletic performance. Katavolos and colleagues investigated whether deficiency of clara cell secretory protein (CCSP)—an endogenous anti-inflammatory molecule produced by airway epithelial cells—underpins this disease, using lung biopsies from three healthy and three RAO-affected horses collected before and after RAO induction, combined with immunocytochemistry and gene expression analysis. The researchers found substantially reduced CCSP concentrations in bronchoalveolar lavage fluid from RAO horses (24–62 ng/ml) compared with healthy controls (129–132 ng/ml), alongside decreased CCSP gene expression in chronically affected animals and visible depletion of CCSP-containing granules within clara cells, particularly during active disease. These findings suggest that impaired CCSP production contributes to the perpetuation of airway inflammation in RAO rather than merely reflecting it, opening potential therapeutic avenues focused on restoring airway epithelial cell function. For practitioners, this mechanistic insight may eventually support emerging treatments aimed at enhancing clara cell secretory capacity or supplementing CCSP directly, though further research is needed to establish causality and clinical efficacy.
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Practical Takeaways
- •CCSP depletion appears to be a key mechanism in RAO pathology; monitoring or supplementing this protective protein could become a diagnostic or therapeutic target
- •Environmental management to reduce mold, dust, and bacterial exposure is critical since CCSP impairment indicates reduced lung protective capacity in susceptible horses
- •Horses with RAO have compromised anti-inflammatory defenses at the cellular level, suggesting they may benefit from more aggressive environmental control and early intervention during flare-ups
Key Findings
- •CCSP protein concentration in lung lavage fluid was 50% lower in RAO-affected horses (median 62 ng/ml before challenge, 24 ng/ml after) compared to healthy horses (median 132-129 ng/ml)
- •CCSP gene expression in lung tissue was significantly reduced in chronically affected RAO horses versus healthy animals
- •Immunogold ultrastructural analysis showed reduced CCSP labeling in Clara cell granules in chronic RAO cases and absent labeling during active disease
- •Reduced CCSP production and subcellular changes in Clara cells are associated features of environmentally induced chronic lung inflammation in horses