C5a/C5aR补体途径在间充质干细胞治疗cGVHD中的作用机制

Mesenchymal stem cell (MSC) is charactered by its special immunoregulation and becomes a promising treatment for chronic graft-versus-host disease (cGVHD). However, the immunoregulative mechanism of MSC remains unclear. Emerging evidences demonstrated that the imbalance of Th17 and Treg cells is the main orchestra leader in many immune diseases and transplant rejection. The complement pathway of C5a/C5aR plays a central role in polarizing CD4+T cell differentiate to Th17 or Treg. Our group is one of few groups to evaluate the efficacy and safety of MSC in cGVHD. We found that the expression of C5a is upregulated, along with the proportion of Th17 cells increased and Treg cells decreased in cGVHD patients compared with non-cGVHD patients. Importantly, the expression of C5a decreased after MSC treatment, companied with less Th17 cells and more Treg cells, indicating that MSC may regulate the C5a expression and the proportion of Th17 and Treg cells. Based on our previous work, we hypothesize that "MSC may down-regulated the expression of C5a, which then regulates the balance of Th17 and Treg cells, resulting in alleviation of cGVHD". In this study, we plan to use samples from patients with cGVHD together with in vitro and in vivo models to investigate the expression of C5a/C5aR in cGVHD; the possibility of MSC to inhibit C5a/C5aR and regulate the balance of Th17/Treg in cGVHD. The outcome of this study will not only provide new insight into mechanisms of pathogenesis of cGVHD, but may also lead to better therapeutic opportunities of MSC for the treatment of cGVHD.

间充质干细胞(MSC)独特的免疫特性使其成为防治慢性移植物抗宿主病(cGVHD)的新曙光，但其免疫调节机制尚不明确。研究报道Th17、调节性T细胞(Treg)比例失衡是许多免疫疾病和移植排斥病理新机制；且C5a/C5aR是Th17、Treg细胞分化的核心途径。申请人所在团队在国际上较早观察MSC治疗cGVHD的效果，发现cGVHD患者C5a表达上调、Th17/Treg失衡；而MSC治疗后C5a表达下降、Th17/Treg失衡缓解，cGVHD好转。由此提出MSC通过阻断C5a/C5aR途径，调控Th17/Treg比例，从而抑制cGVHD的新假说。在前期工作基础上，本项目拟结合临床样本和体内外模型深入研究C5a/C5aR的表达与cGVHD的相关性；明确MSC在cGVHD中的调控作用是否是经C5a-C5aR通路介导Th17/Treg平衡。这将有助于揭示MSC免疫调节机制，开拓临床应用MSC新策略

间充质干细胞(MSC)独特的免疫特性使其成为防治慢性移植物抗宿主病(cGVHD)的新曙光，但其免疫调节机制尚不明确。本项目创新性提出MSC通过阻断C5a/C5aR补体途径，抑制Th17细胞分化而促进Treg，发挥免疫耐受作用从而抑制cGVHD的新观点。我们的研究结果从临床患者、细胞水平、动物模型不同层次证实C5a、C5aR信号通路活化后可促进CD4+T细胞向Th17细胞分化并抑制Treg细胞，引起Th17/Treg细胞比例失衡，导致cGVHD；而MSC可有效干预这一过程的科学假说。在临床患者上发现cGVHD病人外周血中存在Th17/Treg比例失衡，并且C5a、C5aR蛋白表达明显升高；而MSC治疗后，Th17/Treg比例恢复平衡且C5a、C5aR表达降低。在体外细胞实验中发现C5a、C5aR介导CD4+T细胞分化增殖，促进其向Th17分化；而与MSC共培养之后，Th17分化减少而Treg增多，Th17/Treg比例恢复平衡。在cGVHD小鼠模型中，发现C5a/C5aR途径明显活化，Th17/Treg细胞比例失衡，并利用C5aR基因敲除鼠证实C5a/C5aR参与调控Th17/Treg失衡过程。从而揭示了C5a/C5aR通路异常激活介导Th17/Treg比例失衡，诱导cGVHD的机制，以及MSC可有效下调C5a/C5aR信号通路，抑制Th17而上调Treg细胞，延缓和减轻cGVHD病理改变的机制。该项目的研究成果至今已经发表SCI论文2篇，返修2篇；已经北大核心期刊杂志3篇；申请国家发明专利3项，其中1项已经授权。本研究从C5a/C5aR的固有免疫和Th17/Treg的适应性免疫角度揭示了cGVHD疾病的病理机制，并发现MSC可有效干预这一途径发挥重要而潜在的治疗作用。

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