Browsing by Author "Ma, Yi"

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    A Retrospective Study of Conversion From Tacrolimus-based to Sirolimus-based Immunosuppression in Orthotopic Liver Transplant Recipients
    (Başkent Üniversitesi, 2008-06) Yu, Si; Huang, Jiefu; Ju, Weiqiang; Zhu,Xiaofeng; Ma, Yi; Yang, Lu; He, Xiaoshun
    Objectives: Calcineurin inhibitors are used widely in liver transplant recipients. Sirolimus is a new, potent immunosuppressant considered to be nonnephrotoxic. There is limited experience with the use of sirolimus in liver transplant recipients. This study aimed to investigate the clinical experience of conversion from tacrolimus-based to sirolimus-based immunosuppression in liver transplant recipients. Patients switched to cyclosporine-based immunosuppression during the same period were enrolled as controls. Materials and Methods: This retrospective study examined liver transplant recipients who had been switched from tacrolimus-based to sirolimus-based or cyclosporine-based immunosuppressive therapy between January 2004 and January 2007 in the first affiliated hospital of Sun Yat-sen University. Patients were divided into 3 groups: those switched to sirolimus-based immunosuppression owing to acute rejection (group SIR-AR; n=11); those switched to sirolimus-based immunosuppression owing to renal insufficiency (group SIR-RI; n=18), and those switched to cyclosporine-based immunosuppression owing to acute rejection (group CsA-AR; n=15) Results: In patients switched owing to acute rejection, the rate of successful conversion was 54.5% in group SIR-AR (6/11) compared with 60% in group CsA-AR (9/15); this difference was not statistically significant (P > .05). After conversion, renal function in patients in group SIR-AR remained normal. Conversely, renal function in patients in group CsA-AR became abnormal 3 months after conversion. In patients who were switched owing to renal insufficiency in group SIR-RI, renal function improved significantly after conversion (P < .05). In the sirolimus groups, some sirolimus-associated adverse effects occurred but were limited and well controlled. Conclusions: Sirolimus can be used safely in liver transplant recipients. In the early stages after liver transplant, sirolimus combination therapy is recommended to prevent acute rejection. For patients with tacrolimus-related adverse effects, a sirolimus-based immunosuppression regimen is a rescue therapy.
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    Comparison of 2 Heterotopic Heart Transplant Techniques in Rats: Cervical and Abdominal Heart
    (Başkent Üniversitesi, 2011-04) Ma, Yi; Wang, Guodong
    Objectives: Heterotopic heart transplant in rats has been accepted as the most-commonly used animal model to investigate the mechanisms of transplant immunology. Many ingenious approaches to this model have been reported. We sought to improve this model and compare survival rates and histologic features of acute rejection in cervical and abdominal heart transplants. Materials and Methods: Rats were divided into cervical and abdominal groups. Microsurgical techniques were introduced for vascular anastomoses. In the abdominal heart transplant group, the donor’s thoracic aorta was anastomosed end-to-side to the recipient’s infrarenal abdominal aorta, and the donor’s pulmonary artery was anastomosed to the recipient’s inferior vena cava. In the cervical heart transplant group, the donor’s thoracic aorta was anastomosed to the recipient’s common carotid artery, and the donor’s pulmonary artery was anastomosed to the recipient’s external jugular vein. Survival time of the 2 models was followed and pathology was examined. Histologic features of allogeneic rejection also were compared in the cervical and abdominal heart transplant groups. Results: The mean time to recover the donor’s hearts was 7.4 ± 2.2 minutes in the cervical group and 7.2 ± 1.8 minutes in the abdominal group. In the cervical and abdominal heart transplant models, the mean recipient’s operative time was 23.2 ± 2.6 minutes and 21.6 ± 2.8 minutes. Graft survival was 98% and 100% in the cervical and abdominal heart transplant groups. There was no significant difference in graft survival between the 2 methods. Heart allografts rejected at 5.7 and 6.2 days in the cervical and abdominal transplant groups. There was no difference in the histologic features of acute allogenic rejection in cervical and abdominal heart transplant. Conclusions: Both cervical and abdominal heart transplants can achieve a high rate of success. The histologic features of acute allogeneic rejection in the models are comparable.
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    Hepatic Artery Thrombosis After Orthotopic Liver Transplant: A Review of the Same Institute 5 Years Later
    (Başkent Üniversitesi, 2011-06) Wu, Linwei; Hu, Anbin; Wang, Guodong; Ma, Yi; Zhu, Xiaofeng; Wang, Dongping; Ju, Weiqiang; He, Xiaoshun; Tai, Qiang; Guo, Zhiyong; Zhang, Jianwei
    Objectives: Summarize the experience of managing patients with hepatic artery thrombosis after orthotopic liver transplant in a single center. Materials and Methods: A total of 726 adult patients who received a liver transplant at the Department of Organ Transplantation, the First Affiliated Hospital of Sun Yat-Sen University, between January 2004 and December 2009, were selected. Fourteen patients had hepatic artery thrombosis after the operation, and the clinical data of these patients were analyzed retrospectively. Results: The incidence rate of hepatic artery thrombosis was 1.9% (14/726), and the mean time of onset was 10 days (range, 1 - 41 d) after surgery. Six patients had acute deterioration of liver function, 4 had bile leakage, 1 had hepatic abscess, and 3 had no symptoms. Three patients received urgent rearterialization, 2 received intra-arterial thrombolysis, 3 received combined urgent rearterialization and intra-arterial thrombolysis, and 6 patients received a retransplant. The mortality rate associated with hepatic artery thrombosis was 42.9% (6/14); 2 from biliary necrosis and secondary hepatic failure after urgent rearterialization; 1 from recurrent hepatic artery thrombosis and multiple organ failure after intra-arterial thrombolysis; 1 from renal failure and severe infection after combined urgent rearterialization and intra-arterial thrombolysis, and 2 from severe infection after retransplant. The other patients recovered and were followed for 18 to 66 months. Their liver grafts all functioned well with a patent artery. Two died from tumor recurrence at 18 and 29 months after transplant. Conclusions: Hepatic artery thrombosis is a severe complication after liver transplant, which leads to graft loss and recipient death. Rearterialization as early as possible before irreversible biliary and liver parenchyma damage can avoid retransplant.
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    Tolerogenic Semimature Dendritic Cells Induce Effector T-cell Hyporesponsiveness by the Activation of Antigen-Specific CD4+ CD25+ T-Regulatory Cells
    (Başkent Üniversitesi, 2009-09) Fu, Bi-mang; Huang, Jie-fu; Tam, Nga-lei; Wu, Lin-wei; Ma, Yi; Hu, An-bin; Yu, Si; He, Xiao-shun
    Objectives: Researchers recently discovered a group of semimature dendritic cells that induce autoimmune tolerance by activating host antigen-specific CD4+CD25+ T-regulatory cells. We hypothesized that donor semimature dendritic cells injected into recipients would induce effector T-cell hyporesponsiveness by activating CD4+CD25+ T-regulatory cells. Materials and Methods: Donor myeloid semimature dendritic cells were cultivated for 6 days and were then stimulated with tumor necrosis factor α for 24 hours. BALB/c mice were pretreated with semimature dendritic cells to generate antigen-specific CD4+CD25+ T-regulatory cells in vivo. The role of CD4+CD25+ T-regulatory cells in transplant immunity was studied via mixed lymphocyte culture in vitro. Results: Surface markers and cytokines secreted by semimature dendritic cells differed from those secreted by immature myeloid dendritic cells or mature dendritic cells. Semimature dendritic cells and immature myeloid dendritic cells did not activate allogenic lymphocyte responses in coculture studies. CD4+CD25+ T-regulatory cells of recipients challenged by donor semimature dendritic cells, which expressed a high level of interleukin-10, induced hyporesponsiveness in host effector T cells that were stimulated by donor splenocytes. In contrast, CD4+CD25+ T-regulatory cells did not induce hyporesponsiveness in effector T cells when the host T cells were stimulated by third-party antigen from DBA2 mice splenocytes. Conclusions: Our findings confirm that semimature dendritic cells are an independent subgroup of dendritic cells in both immune function and morphologic profile. It may be the cytokine secretion profile of semimature dendritic cells (rather than that of surface markers) that has a key role in inducing CD4+CD25+ T-regulatory cells to express a high level of interleukin-10. Immunization with donor semimature dendritic cells may be an effective method of inducing transplant tolerance, but further evidence-based studies of that topic are necessary