Alloimmune injury preceding airway obliteration in porcine heterotopic lung implants: a histologic and immunohistologic study.

BACKGROUND: Obliterative bronchiolitis (OB), the major long-term complication of lung transplantation, has thus far lacked a good large-animal model. Our goal was to develop such a model on the basis of previous rodent models with tracheal implants.
METHODS: Fragments of pulmonary tissue with structures of terminal bronchi were subcutaneously transplanted to four random-bred domestic piglets. Each animal received 10 autograft and 10 allograft implants. The histologic findings were graded from 0 to 3 for implants harvested repeatedly over 2 months.
RESULTS: In autografts, partial destruction of the respiratory epithelium and gradual luminal obliteration as well as mild damage to the cartilage and the bronchial wall underwent rapid reversal after initial ischemic injury. In the allografts, epithelial destruction and gradual obliteration were total within 14 days, the difference being statistically significant (P<0.05) in both. The histologic features of the obliterative plug were similar to those of human OB. In the allografts, cartilaginous destruction and pericartilaginous inflammation increased gradually to severe levels, significantly worse than in the autografts (P<0.05). Necrosis and inflammation of the bronchial wall were also more severe in the allografts (P<0.05).
CONCLUSIONS: At the end of follow-up, all autografts were vital, whereas the allografts were almost totally rejected and were without native structures. All bronchi in the allografts exhibited accelerated obliteration with histologic features characteristic of human OB, thus providing a model for research into OB and its prevention.