间质干细胞治疗慢性移植物抗宿主病的免疫作用机制

Chronic graft-versus-host disease (cGVHD) continues to be a common cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Conventional immunosuppressive therapies are often ineffective, and new therapeutic strategies are needed. Mesenchymal stem cells (MSC), possessing an ability of immuno-regulation, have been proven to be an effective treatment for cGVHD. However, the mechanism of action is still unknown. Our group had reported that the clinical improvement of MSC treatment was accompanied by a decrease in the plasma levels of B cell-activating factor (BAFF),and the increase of CD27+ memory B cells and CD5+ regulatory B cells (Leukemia, Mol Ther), suggesting that B cells may play an important role in the MSC treatment for cGVHD. Based on the previous results, we will systematically compare the dynamic variation and action pattern of lymphocyte subsets of cGVHD patients before and after the infusion of MSC, try to discover the critical B cell subsets in improving cGVHD. Using mice cGVHD model, we will figure out the where and how the MSC regulate the differentiation and activation of B cells, and elucidate the role of BAFF or BCR signaling, and other molecules in affecting B cell peripheral differentiation, reestablishing B cell homeostasis by MSC. The results may not only help to reveal the cellular and molecular mechanisms of MSC therapy, but also shed new light on new strategies for treatment of cGVHD.

慢性移植物抗宿主病（cGVHD）是造血干细胞移植后主要并发症和死亡原因，传统免疫抑制疗效欠佳，迫切需要新的治疗策略。间质干细胞（MSC）具有免疫调节功能，已被证实是治疗cGVHD的有效手段，但其作用机制远未阐明。申请人前期研究显示MSC改善cGVHD症状与BAFF水平下降、CD27+记忆性B细胞和CD5+调节性B细胞的增加密切相关（Leukemia，Mol Ther等），提示B细胞可能在MSC治疗cGVHD中扮演了重要角色。据此，本研究拟比较MSC治疗前后淋巴细胞亚群的变化规律与作用模式，鉴定影响MSC疗效的关键B细胞亚群及其功能；利用小鼠cGVHD模型发现MSC调控B细胞分化、功能的作用位点与调控靶点，阐明BAFF、BCR等途径在MSC调节B细胞外周分化、参与B细胞稳态重建中的作用机制。研究结果有助于揭示MSC治疗cGVHD的细胞与分子机制，也为探讨cGVHD的治疗新策略提供理论依据。

慢性移植物抗宿主病（cGVHD）是造血干细胞移植后主要并发症和死亡原因，传统免疫抑制治疗效果欠佳，迫切需要新的治疗策略。间质干细胞（MSC）具有多维度、多靶点免疫调控作用，已被证实是治疗cGVHD的有效手段，但其作用机制远未阐明。项目负责人首次报道MSC治疗有效与CD27+记忆性B细胞和CD5+调节性B细胞的改变密切相关，为了系统解析不同B细胞亚群在MSC治疗cGVHD中扮演的角色，本项目利用“光谱流式+单细胞测序”技术，筛选并发现CD20-CD27+CD86+B细胞可指示cGVHD的发病进程，CD21low/-CD23-B细胞则是一群具有自身反应性特征的致病亚群；MSC通过诱导致病亚群凋亡，增加CD23+CD43+调节性B细胞的数量与功能发挥治疗cGVHD的作用；发现脾脏等次级淋巴器官是MSC调控B细胞分化的重要场所，建立了MSC精准递送策略，显著增加MSC靶向病损组织能力并提高治疗效果。阐明POSTN、STC2、THBS1等为MSC免疫调控新分子，揭示通过MSC激活胆碱能抗炎通路、调控TCR-Ca2+信号等发挥快速抑炎作用。聚焦是cGVHD的典型病理特征——组织纤维化，发现间质细胞中Nestin可通过调控TGFβ信号通路激活在组织器官纤维化进程中扮演重要角色，抑制Nestin表达可显著缓解纤维化的症状。针对不同组织来源MSC的功能异质性，发现次级淋巴器官来源的MSC具有更强的免疫调节功能，建立了经不同发育路径获得MSC功能亚群的新方法，为优化MSC治疗cGVHD提供了新策略。项目执行期间，在J Hepatol，Eur Respir J，Signal Transduct Target Ther等发表SCI论文25篇，其中IF>30有5篇，IF>10有14篇；获得授权专利3项，荣获广东省自然科学奖一等奖等奖励6项，牵头制定《人间充质干细胞》团体标准。

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