Orthotopic and heterotopic tracheal transplantation model in studying obliterative bronchiolitis.

BACKGROUND Several animal models have been established to investigate the mechanisms of obliterative bronchiolitis after lung transplantation. In this study, we compared three prevalent murine models of obliterative bronchiolitis in terms of several basic pathologic changes in a relatively short span of time after transplantation. METHODS Each of the recipient mice simultaneously received orthotopic, intra-omental and subcutaneous tracheal transplantation in both syngeneic and allogeneic settings. No immunosuppressive treatment was administered. Tracheal grafts were harvested on Day 14, 21 and 28 after transplantation for histological and immunohistochemical analyses. RESULTS Syngeneic tracheal grafts from different transplant sites retained normal histologic structures, while their corresponding allografts demonstrated more occlusion of the airway lumen as well as more infiltration of CD4(+)/CD8(+) mononuclear cells and myofibroblasts, but less regenerative epithelium and neovascularized vessels at indicated times (P<0.05). Compared with two heterotopic allografts, orthotopic allografts had less occlusion of the tracheal lumen as well as less infiltration of CD4(+)/CD8(+) mononuclear cells and myofibroblasts, but more regenerative epithelium and neovascularized vessels (P<0.05). CONCLUSIONS Orthotopic tracheal transplantation in mice can be considered as a model to study early stages of obliterative bronchiolitis, and heterotopic tracheal transplantation can be a model for late stages of obliterative bronchiolitis.