肝移植是多种终末期肝病的唯一有效治疗手段。诱导对供者特异的免疫耐受，摆脱对免疫抑制剂的长期依赖，已成当前肝移植乃至异体器官移植领域的主要研究目标。骨髓移植建立混合嵌合体诱导免疫耐受是迄今唯一试用于临床的免疫耐受诱导机制，但在临床肝移植中应用尚需解决如下问题：1）避免GvHD反应；2）减少受体骨髓移植前预处理的毒副作用。本研究针对FC细胞在易化骨髓移植及诱导免疫耐受方面的最新研究成果，拟采用骨髓造血干细胞（HSC）+FC细胞移植建立混合嵌合体模型，进而研究嵌合体形成对移植肝免疫耐受的诱导作用，筛选诱导耐受形成所必需的毒副作用最小的预处理方案，探索移植肝脏免疫耐受形成的细胞与分子机制，从而建立起安全有效的骨髓移植-嵌合体形成-肝移植免疫耐受方案，为骨髓移植诱导肝移植免疫耐受的临床应用提供科学依据，同时也为研究其它多种器官异体移植免疫耐受奠定方法学基础。

Liver transplantation has become a well-recognized treatment option for people with end-stage liver diseases. The main challenge facing liver transplantation nowadays is to induce donor-specific tolerance and to avoid lifelong dependence on immunosuppressive drugs. One of the best-studied approaches for establishing tolerance is hematopoietic stem cell (HSC) chimerism. chimerism is associated with donor-specific transplantation tolerance in vivo and in vitro and has been shown to effectively induce donor-specific tolerance to a variety of allografts. In humans, bone marrow transplantation (BMT) induced mixed chimerism has been shown to confer acceptance of donor specific skin and kidney allografts without long-term immunosuppression. Despite the promising potential of mixed allogeneic chimerism, important considerations which must be addressed are (1) the risk of GVHD and (2) toxicity of the conditioning. In this study, based on the latest findings on the role of facilitating cells (FCs) in facilitating stem cells engraftment, we aim to establish mixed chimerism with combined use of HSC and FCs in a rat model, and the rats will accept liver transplantation simultaneously. Thus, we can systematically study the role of HSC+FCs in promoting the establishment of mixed chimerism and the iduction of donor-specfic tolerance in liver transplantation, choose a set of conditioning protocols with minimal toxicity, and investigate the cellular and molecular mechanism of transplantation tolerance. The purpose of the study is to establish a safe and effective BMT-Mixed chimerism-Liver transplantation tolerace protocol, and from a long run, to provide a scientific foundation for clinical use of BMT induced liver/other solid organs transplantation tolerance protocol.

本研究针对FC细胞在易化骨髓移植及诱导免疫耐受方面的最新研究成果，采用骨髓造血干细胞（HSC）+FC细胞移植建立混合嵌合体模型，进而研究嵌合体形成对移植肝免疫耐受的诱导作用，筛选诱导耐受形成所必需的毒副作用最小的预处理方案，探索移植肝脏免疫耐受形成的细胞与分子机制。我们的研究结果表明：在前期实验筛选的最佳FCs（1,000,000）+最佳HSC（100,000）组合下，应用FK506 0.5mg/kg/d×11d，能够进一步将γ射线照射剂量降低至200 cGy。术后一月嵌合体中供体细胞水平仍维持在5%左右。HSC与FCs联合移植建立嵌合体，能够对大鼠移植肝脏诱导免疫耐受（嵌合体能够接受ACI供体皮肤移植，但排斥F344供体皮肤移植），移植肝脏急慢性排斥反应发生率显著低于对照组（66.7% VS 16.7%）。本研究通过建立安全有效的骨髓移植-嵌合体形成-肝移植免疫耐受方案，为骨髓移植诱导肝移植免疫耐受的临床应用提供了科学依据，同时也为研究其它多种器官异体移植免疫耐受奠定了方法学基础。