An abnormality in alveolar repair would also preclude the necessity of continued superimposed inflammation to drive alveolar remodeling; the lack of an essential role for inflammation in the pathogenesis has been proposed by Selman et al. The ultrastructural findings in feline IPF suggest that the propagation of the disease may be the result of an underlying defect in type II pneumocyte biology. Whether this is due to inherent genetic defect(s) in the affected feline type II cells is currently under investigation. so
In summary, this study has shown that the domestic cat acquires a chronic respiratory disease that is pathologically very similar to IPF of humans. As with human IPF, the affected cats are older (mean age, 8.7 years) and poorly responsive to corticosteroid therapy. Both the gross pulmonary lesions and the histopathology share most of the features of the human disease. These features include multifocal distribution within the lung with subpleural orientation, honeycomb formation with abundant metaplasia of the lining epithelium, alveolar septal myofibroblast metaplasia with smooth-muscle formation, and fibrosis with fibroblast/myofibroblast foci formation. The ultrastructure of the type II pneumocyte in feline IPF suggests that abnormalities in type II cell biology are important in the abnormal alveolar repair of the disease, and that this drives the progressive fibrosis of feline IPF. These features are important in identifying animal models of IPF that faithfully recapitulate the pathogenesis and progression of the human disease. Based on the findings of this study, we conclude the following: (1) spontaneous chronic respiratory disease with pathology findings consistent with IPF/UIP occurs in the domestic cat; (2) as with the human disease, the type II pneumocyte and myofibroblasts are important cellular constituents in feline IPF; (3) the changes in type II pneumocyte ultrastructure in feline IPF are similar to a familial form of human IPF associated with a mutation in the surfactant protein C gene; (4) spontaneous feline IPF may be primarily a defect in type II pneumocyte biology; and (5) understanding the cause and pathogenesis of IPF in the cat holds promise for advancing our understanding of the disease in people.