| Background:Lung Transplantation is the only treatment and the last effective method for the end-stage lung diseases. Unlike heart transplantation, liver transplantation, and kidney transplantation, lung has its anatomical and physiological particularity, especially for containing a large amount of bronchial associated lymphoid tissues, where immune cells mature in many ways triggered by the immune response, rejection of the lung transplantation occurs more serious and earlier than liver and kidney transplantation [M]. Therefore, lung transplantation has become one of the hotest topics in the field of organ transplantation and thoracic surgery. So far,3,546 cases of heart and lung transplantation and 32,652 cases of lung transplantation have been completed worldwide, with the annual growth rate of about 2,000 cases[5].The pathology of chronic rejection after lung transplantation mainly presents as obliterative bronchiolitis (OB) is an important limiting factor to long-term survival in lung transplantation patients, and there are no effective medicine to treat this complication[6]. During the past years, how to prevent or reduce tissue cells and organs ischemia-reperfusion injury is an important research topic of organ transplantations. A lot of ischemia-reperfusion injury animal models after lung transplantation have been' established as well as many heterotopic or orthotopic tracheal transplantation animal models[7-8] for researching obliterative bronchiolitis have been reported. But the heterotopic tracheal transplantation model does not meet the normal physiological characteristics, The environment around the heterotopic transplanted tracheal is different from the environment in the chest:the transplanted tracheal with no air flow through, lost self-purification, increase the incidence fibrosis risk, can not observed the impact of pathogens in air on the graft, and can not observe the therapeutic effect by respiratory administration against immune rejection; the epithelial cells in orthotopic transplanted tracheal would be replaced by the host epithelial cells, showing re-epithelialization process, without normal blood supply, heterotopic transplanted tracheal is susceptible to the environmental impact of the surrounding skin or the greater omentum[8-12].The etiology of OB (Obliterative Bronchiolitis) includes transplanting and non-transplanting factors. The main factors of non-transplanting are connective tissue disease, inhalation injury and infection, etc; transplanting factors are bone marrow transplantation, heart and lung transplantation and lung transplantation[13].The pathological changes of obliterative bronchiolitis are described as follows: Bronchiole epithelial cells damage, the inflammatory cell infiltration in peripheral or submucosal bronchioles and fibrosis which caused stenosis, but no granulation tissue formation within the intracavity. When the lesion is slight, it only appears inflammatory cell infiltration in the small bronchial mucosa, submucosa, and mild peripheral wall, or necrosis of bronchiolar epithelial cells. As the lesions progress, the bronchial lumen produces collagen, which gradually causes fibrosis and scar contraction, resulting in luminal narrowing and distortion, severely blocken of the lumen completely. The clinical manifestations of obliterative bronchiolitis commonly known as BOS (bronchiolitis obliterans syndrome), of which clinical manifestations are lung function decline, that is, forced expiratory volume in 1 second and FEF decreasing. Its pathogenesis is very complicated, including immunological and non-immunological factors and other risky factors.According to the statistics from ISHLT (International Heart and Lung Transplantation Society), OB is the main cause of death of lung transplant patients in 5 years, accounting for 48% of all causes. Although surgical techniques and immunosuppressive therapy have greatly improved, OB still can not get effective treatment, which is seriously affecting the lung function and the patients'quality of life. Therefore, to establish a stable and practicable model of obliterative bronchiolitis after lung transplantation for studying the pathogenesis and prevention, diagnosis and treatment of bronchiolitis obliterans has an important value. Therefore, to establish a stable and practicable rat lung transplantation model to figure out the pathogenesis of obliterative bronchiolitis, and to find an effective treatment for obliterative bronchiolitis, is very important to prolong lung transplantation patients'survival and to improve postoperative patients' quality of life.Objectives:To improve the technology of orthotopic left lung transplantation using cuff technique, in order to establish a long-term, stable and practicable rat orthotopic left lung transplantation for observing the obliterative bronchiolitis.Methods:Using a modified cuff technique to inosculate bronchial, pulmonary artery and pulmonary vein and establish a rat orthotopic left single lung transplantation model. And record the operation success rate, total operation time, recipient operation time, donor lung cold ischemia time, warm ischemia time (inosculation time) and survival rate. Rats for lung transplantation were divided into two groups:A group and B group. A group is comprised of 12 rats, in which 6 for donors and 6 for recipient to complete 6 operations. Monitor the status and survival rate of these rats. Chest X-ray was taken in 1 month after transplantation before execution. Sacrifice them in 1 month, carry out the hematoxylin-eosin staining of the donor lung and observe lung tissue structure and cell infiltration; B group is comprised of 12 rats, in which 6 for donors and 6 for recipient to complete 6 operations. Monitor the status and survival rate of these rats. Chest X-ray was taken in 1 week after transplantation before execution. Sacrifice them in 1 week, carry out the hematoxylin-eosin staining of the donor lung and observe lung tissue structure and cell infiltration.Results:This study was completed by a single person under direct vision. The total success rate was 100%(12/12), the total operation time for the donor and recipient:131±16min, the recipient operation time:64±8 min, the cold ischemia time of transplanted lung: 87±17 min, the warm ischemia time of the graft:24±6 min.6 rats of "A " group all survived, short-term (1 week) survival rate was 100%(6/6),5 rats were survived in long term (> 1 month), long-term survival was 83%(5/6). X-ray were taken for the 5 survived rats of "A" group in 1 month, which suggested that the transplanted lungs were all shrinked. HE staining of grafted lungs in 3 rats showed that inflammatory cell infiltration in small bronchial mucosa, submucosa and peripheral wall, bronchioles fibrosis, some of the lumens were obturated, which demonstrated OB formation; 6 rats of "B" group all survived, short-term survival rate was 100%(6/6). X-ray were taken for the 6 survived rats of "B" group in 1 week, which all showed that transplanted lung had good shapes, HE staining all showed that the lung parenchyma and interstitial tissue were normal, with a small amount of lymphocytes and neutrophils infiltration, which demonstrated no OB formation.Conclusions:The modified rat lung transplantation model based on the cuff technique has many advantages, such as obtain donor lung rapidly, precise and simple to inosculate pulmonary vessels and bronchial tube and long survival time of recipients. Through our consistent exploration, we finally established a stable, practical orthotopic left lung transplantation model in rats, and observed obliterative bronchiolitis formation of the transplanted lung in rats.
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