血小板活化调节信号轴PAF-AH/PAF表达失衡介导异种肝移植术后急性血管性排斥反应的作用及机制研究

以猪为供体有望解决供肝短缺，但术后急性血管性免疫排斥（AVR）限制移植肝存活。前期完成11例猪-猴肝移植，分析手术前后受体PBMC差异基因，发现血小板活化因子乙酰水解酶（PAF-AH）术后表达缺失而PAF上调。PAF由巨噬细胞分泌，是最强促炎因子；PAF-AH是其降解酶，表达缺失导致PAF蓄积，放大免疫损伤。预实验发现术后受体外周血PAF明显增高，PAF-AH显著降低。以猪肝细胞刺激骨髓来源巨噬细胞，PAF-AH表达降低且PAF、IL-6等升高。结合文献及前期研究，推测PAF-AH缺失导致PAF负性调控失活并加重AVR。但机制是什么？应用PAF-AH重组蛋白能否减轻AVR、延长存活时间？与现有免疫抑制剂有无协同或拮抗？为此，本课题拟在异种肝移植动物和细胞模型中，明确PAF-AH表达缺失对AVR的影响及机制，验证PAF-AH重组蛋白减轻免疫排斥、延长移植肝存活时间效果，推动异种移植临床转化。

Liver Xenotransplantation with pig as donor is the main way to solve the shortage of donor liver, but acute vascular rejection (AVR) limits the long-term survival of liver xenograft and recipients. We have successfully completed the first pig to monkey liver xenotransplantation in China, and 11 cases have been completed so far. We analyzed the differential gene expression profiles of PBMCs before and after surgery, and found that the platelet activating factor acetylhydrolase (PAF-AH) was completely absent after surgery, but PAF was significantly up-regulated. PAF is mainly secreted by macrophages, which is the strongest pro-inflammatory factor known at present. PAF-AH is its specific degradation enzyme, so PAF-AH expression loss will lead to PAF accumulation, mediate and amplify the damage of AVR. We further found that the PAF-AH in the peripheral blood of recipients was significantly increased, but the PAF-AH was significantly decreased. We used GTKO porcine hepatocytes and vascular endothelial cells to stimulate macrophages derived from bone marrow in vitro, and found that PAF-AH expression was down-regulated, and the contents of PAF, IL-6 in the culture medium were significantly increased. Combined with the literature and previous studies, it is speculated that PAF-AH deficiency leads to the deactivation of PAF negative regulatory mechanism and aggravates the liver graft injury. But what is the mechanism? Can PAF-AH reduce AVR and prolong survival time? Are there synergistic or antagonistic effects with existing immunosuppressants? Therefore, we intend to take the animal model of xenogeneic liver transplantation, the cell model of xenogeneic immune rejection and coagulation dysfunction as the objects, to clarify the role and mechanism of PAF-AH expression loss in xenogeneic AVR, to verify the effect of PAF-AH recombinant protein on reducing the immune rejection injury and prolonging the survival time of transplanted liver and recipient, so as to achieve the clinical transformation of xenogeneic liver transplantation.