The distribution of myofibroblasts in feline IPF are similar to that of the human disease. While myofibroblasts are found in rodent models of pulmonary fibrosis, because of the lack of honeycombing, they lack the relationship with the metaplastic epithelium that is important in the progressive fibrosis of IPF. Uhal et al showed that in human IPF lung there is an increase in the apoptosis of the metaplastic epithelial cells overlying foci of myofibroblast metaplasia. This apoptosis may be mediated by local conversion of native angiotensinogen into angiotensin II, which goes on to mediate apoptosis through the angiotensin receptor subtype AT-i.- Induction of myofibroblasts subjacent to the metaplastic epithelial cells in cats with IPF may create a similar environment of epithelial cell loss. The finding of attenuated epithelial cells overlying the sites of myofibroblast metaplasia implies repair after previous cell loss, the pathogenesis of which may involve the above process. read
The ultrastructure of the type II pneumocyte in spontaneous feline IPF suggests that the type II cell may be integral in the pathogenesis of the disease. The morphology of the lamellar body-like structures is abnormal and similar to those reported by Thomas et al in a kindred of people with UIP and cellular NSIP associated with a mutation in the prosurfactant protein C gene. The authors suggest that misfolding of the pro-surfactant protein C may lead to type II cell injury and loss. Recently, the role of abnormalities in surfactant genes and interstitial lung disease in humans has been reviewed. Exfoliation of the type II cells in the lungs of feline IPF suggests that the cells are being lost as part of the aberrant alveolar epithelialization. This process has been suggested to be important in the development of pulmonary fibrosis.