TSP-1与CD47结合的分子基础和TSP-1/CD47信号对异种移植影响的机制研究

CD47 plays an important role in transplant rejection. CD47 acts as a marker of “self” that prevents phagocytosis of autologous cells by binding to signaling regulatory protein (SIRPα), a critical inhibitory receptor on macrophages. This is particulary significant in xenotransplantation. However, CD47 signaling upon binding to thrombospondin-1 (TSP-1) induces CD47-dependent apoptosis and accelerates graft rejection. Thus, ensuring the binding of SIRPα and CD47 while restraining the interaction between TSP-1 and CD47 may significantly improve graft survival. To this end, it is important to identify the binding site of CD47/TSP-1 interaction. In this project, we will express human mutant CD47 in porcine lymphoma cells to achieve its binding to SIRPα and block the negative signals in survival from TSP-1 simultaneously. We will employ heterogeneous cell co-culture, also use NOD/SCID mice to assess the potential of mutant CD47 expression which inhibits macrophage-mediated rejection of porcine cells in vivo. In addition, we will investigate the regulation of mutant CD47 on cell signal pathways. These studies are expected to provide important information help to develop novel means of establishing transgenic animal model for transplant. It can also provide novel targets for developing clinical drugs which resist to transplant rejection.

CD47在移植排斥反应中发挥重要作用。移植过程中，移植供体细胞表面CD47与受者巨噬细胞表面SIRPα结合，保护移植物不被受体巨噬细胞吞噬而存活，这在异种移植中表现显著；但TSP-1与供体细胞表面CD47作用会导致移植物损伤。因此，保留CD47与SIRPα结合同时抑制CD47与TSP-1相互作用将有效提升移植物存活质量。目前CD47与TSP-1相互作用位点尚未明确，这是移植免疫领域亟待解决的问题。本项目拟在猪B淋巴瘤细胞表面表达人突变型CD47，力求使其既能与SIRPα结合，保留抑制吞噬能力，又能阻断TSP-1传导的负向调节生存信号。采用异源细胞共培养和NOD/SCID小鼠移植模型，探讨突变型CD47对吞噬的调控机制。通过检测突变型CD47下游信号变化，研究其对细胞的调控机制。为提高异种移植物存活质量奠定理论基础，并为建立可供移植的转基因动物模型以及开发临床抗移植排斥药物提供新靶点。