Rapamycin Inhibits Epithelial Mesenchymal Transition And Attenuates Obliterative Airway Disease In Murine Tracheal Allograft

Part â… :Establishment of Murine Obliterative Bronchiolitis ModelBackground:Couples of animal models have been developed to investigate the mechanisms of obliterative bronchiolitis (OB) post lung transplantation. In this study, we compared three prevalent murine models of obliterative bronchiolitis in terms of several pathologic changes after transplantation.Methods:Recipient mice received one of the orthotopic, intra-omental and subcutaneous tracheal transplantations in both syngeneic (Balb/C to Balb/C) and allogeneic (Balb/C to C57BL/6) settings. No immunosuppressive drugs were administered. Tracheal grafts were harvested on Day14,21and28post-transplant for histological and immunohistochemical assessment.Results:Syngeneic tracheal grafts from different transplant sites maintained normal histologic structures, while the corresponding allografts exhibited 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 the two heterotopic allografts, the orthotopic had less occlusion of the tracheal lumen as well as less CD4+/CD8+mononuclear cells and myofibroblasts, but more regenerative epithelium and neovascularized blood vessels (P<0.05).Conclusions:We presume orthotopic tracheal transplantation in mice can act as a model to study early stages of OB, and heterotopic tracheal transplantation can be a model for late stages of OB. Part â…¡:Epithelial-Mensenchymal Transition in Murine Orthotopic Tracheal AllograftBackground:In graft lungs of patients with BOS, airway remodelling was observed, including epithelium of the airway shedding and fibrosis proliferation. In this study, we hypothesized that epithelial-mesenchymal transition (EMT) occurs with the development of BOS after transplantation.Methods:Recipient mice received orthotopic tracheal transplantation in both syngeneic (Balb/C to Balb/C) and allogeneic (Balb/C to C57BL/6) setting. No immunosuppressive treatment was administered. Tracheal grafts were harvested on Day14,21and28after transplantation for histological and immunohistochemical analyses.Results:Syngeneic tracheal graft maintained normal histological structures, while allografts exhibited more occlusion of the airway lumen (P<0.05). Compare with syngeneic tracheal grafts, tracheal allografts exhibited lower expression of epithelium markers E-cadherin, but higher expression of myofibroblasts markers a-SMA as well as marker of epithelial damage and EMT MMP-9(P<0.05).Conclusions:Our data demonstrates that EMT occurs with the development of Obstructive airway disease in mice tracheal allografts,which suggests that EMT is a potential target in the treatment of OB post lung transplantation. Part III:Rapamycin Inhibits Epithelial-Mesenchymal Transition and Attenuates Obliterate Airway Disease in Murine Tracheal AllograftBackground:Rapamycin (RAPA) is employed to prevent rejection of transplanted solid organ as an immunosuppressive agent. Rapamycin can improve pulmonary function of lung transplant patients with bronchiolitis obliterans syndrome (BOS), but as a result of severe adverse events, it is sometimes intolerant. In this study, we investigate the outcomes of murine tracheal allografts treated by reduced-dose Rapamycin.Methods:Recipient mice underwent orthotopic tracheal transplant after been allocated into randomized groups. Recipients were treated with either different doses of Rapamycin (experimental group) or solvent (control group) after transplantation. Tracheal allografts were harvested in the28th day post-transplant for histological, immunohistochemical, Western-Blot and Flow Cytometry analyses.Results:Compared with tracheal allografts in experimental groups, tracheal allografts in control group exhibited more occlusion of the airway lumen (P<0.05) and underwent epithelium to mesenchymal transition:lower expression of E-Cadherin, but higher expression of myofibroblasts markera-SMA, MMP-9as well as fibrocytes both in peripheral blood and tracheal allografts (P<0.05). The outcomes of mid-dose and high-dose RAPA groups made no differences (P>0.05), which were better than those in low-dose RARA groups:the cell counts of peripheral fibrocytes in all groups were not significantly different (P>0.05), but the cell counts of tissue fibrocytes in mid-dose RAPA groups were both decreased than those in low-dose group (P<0.05).Conclusions:Our study demonstrated that higer-dose Rapamycin can attenuate obstructive airway disease with inhibiting epithelium-mesenchymal transition in murine tracheal allograft, and EMT plays an import role in development of obstructive airway diseases post tracheal transplantation.