Spontaneous Lung Lesions in Aging Laboratory Rabbits (Oryctolagus cuniculus)

• Published in: Veterinary pathology 2017-01, Vol.54 (1), p.178-187
• Main Authors: Cooper, T. K., Griffith, J. W., Chroneos, Z. C., Izer, J. M., Willing, L. B., Peng, X.
• Format: Article
• Language: English
• Subjects: Aging - pathology; Animals; Female; Lung - pathology; Male; Pneumonia - pathology; Pneumonia - veterinary; Pulmonary Artery - pathology; Rabbits - anatomy & histology; Rabbits - physiology; Retrospective Studies
• ISSN: 0300-9858; 1544-2217
• DOI: 10.1177/0300985816658102

Spontaneous age-related lesions of laboratory rabbits are not well documented in the contemporary scientific literature. A retrospective study of diagnostic necropsies of 36 rabbits >2 years of age found a number of common lung lesions. Fibromuscular intimal hyperplasia affected medium and to a lesser extent large pulmonary arteries and was present to a variable extent in all 36 rabbits >2 years of age. The lesions were characterized by fragmentation and/or reduplication of the internal elastic lamina (IEL), proliferation of smoothelin+/alpha-smooth muscle actin (α-SMA)+/vimentin− smooth muscle cells and fewer smoothelin−/α-SMA+/vimentin+ myofibroblasts, and intimal deposition of collagen without thrombosis, embolism, or evidence of pulmonary hypertension. Pulmonary emphysema, present in 30/36 rabbits, was characterized by the loss of alveolar septa; most affected rabbits did not have clinical signs of respiratory disease. In 8/13 rabbits of the inbred EIII/JC audiogenic strain, we identified a unique syndrome of granulomatous pneumonia containing hyaline brown to gray, globular to ring-like acellular material that was Alcian blue and periodic acid-Schiff positive. The material was immunoreactive for surfactant protein-A and had the ultrastructural appearance of multilamellar vesicles, suggesting a genetic defect in surfactant metabolism. Additionally, we found small benign primary lung tumors (fibropapillomas, 5 rabbits) not previously described. Other findings included heterotopic bone (5 rabbits), subacute to chronic suppurative bronchopneumonia, pyogranulomatous pneumonia with plant material, and pulmonary artifacts from barbiturate euthanasia solution.