Apoptosis Of The Donor Tracheal Epithelium Can Exacerbate Obliterative Bronchiolitis After Tracheal Transplantation In Mice

Part 1:A modified bone marrow transplantation model to label bone marrow-derived cellsBackground:We intended to demonstrate the migration and effect of the bone marrow-derived cells. First of all, we needed to label the bone marrow-derived cells. We chose a syngeneic, sex-mismatched bone marrow transplantation model to label the bone marrow-derived cells. However, the recipients are lethally irradiated prior to bone marrow transplantation. The lethal irradiation can not only destroy the bone marrow microenviroment of the recipients but also cause acute radiation injury. The bone marrow mesenchymal stem cells can regenerate the bone marrow microenvironment to improve the hematopoietic engraftment.Methods:First of all, we isolated the bone marrow cells of male C57BL/6 mice. Then, the cells were cultured to acquire pure bone marrow stem cells. The female C57BL/6 mice were lethally irradiated at a dose of 8 Gy and injected with 0.2 ml of medium containing different ingredients via the tail vein. For the bone marrow cell (BMC) group (n=6), the mesenchymal stem cell (MSC) group (n=6), and the bone marrow cell+mesenchymal stem cell (BMC+MSC) group (n=6), the medium contained 1×107 bone marrow cells, 1×106 mesenchymal stem cells, or 1×107 bone marrow cells and 1×106 mesenchymal stem cells, respectively. At 1,2,4 weeks after the bone marrow transplantation, the peripheral blood of the recipents was collected to performed q-PCR. Then, the chimerism of the recipients was calculated.Results:In the control group, no mice survived more than 2.5 weeks, and no SRY could be detected when the mice were alive. The chimerism of the MSC group was low during the observation period. Recipients transplanted with BMC had a much lower chimerism compared with mice transplanted with BMC+MSC at 1 and 2 weeks after transplantation. However. the chimerisms of the two groups were similar at 4 weeks.Conclusion:We established a modified bone marrow transplantation model via cotransplanting bone marrow cells and bone marrow stem cells. We can label the bone marrow-derived cells better than before with this modified model.Part 2:Apoptosis of the donor tracheal epithelium can exacerbate obliterative bronchiolitis after tracheal transplantation in mice.Background:The long-term outcome of lung transplantation is impeded by obliterative bronchiolitis (OB). However, the current treatment cannot effectively prevent the development of OB. The present studies show that the apoptosis of tracheal epithelia triggers the development of OB and the extracellular matrix is mainly produced by myofibroblasts. Here, we sought to investigate the relationship between the apoptosis of tracheal epithelia and the increase of myofibroblasts in the process of OB.Methods:Mice orthotopic tracheal transplant model was established by using C57BL/6 or BALB/c as donor and chimera as recipient. The allografts and syngrafts were separately harvested at 1,2,3 and 4 weeks after tracheal transplantation. The percentage of tracheal lumen occlusion was assayed via histology and morphometry. Immunofluorescence staining was used to detect the apoptotic epithelial cells and recipient-derived myofibroblasts. The expression of SDF-1? and TGF-? and the infiltrations of CD4+ and CD8+ T cells in the grafts were detected by immunohistochemical staining.Results:We found that there were more apoptotic epithelia in the allograft group than in the syngraft group, and that the level of tracheal lumen occlusion was higher at different time points. Moreover, the increase in the apoptosis of the tracheal epithelium occurred earlier than that of occlusion of the tracheal lumen. There were more myofibroblasts derived from the recipients' bone marrow and more CD4+ and CD8+ T cells in the allografts. The expression of SDF-1? and TGF-? was higher in the epithelium from allografts than in those of syngrafts.Conclusions:Our study indicated that the apoptotic tracheal epithelia in the OB model might increase the amount of myofibroblasts derived from the recipient's bone marrow. Therapeutic methods aim at preventing apoptosis of the tracheal epithelium may improve the outcome of lung transplantation.