Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with M1-type macrophage activation. Mesenchymal stem cells (MSCs) therapies have shown promise in models of pathologies relevant to SLE, while the function and mechanism of MSC-derived exosomes (MSC-exo) were still unclear. We aimed to interrogate the effect of MSC-exo on M1-type polarization of macrophage and investigate mechanisms underlying MSC-exo. Exosomes were isolated from MSC and the effect of MSC-exo on macrophage polarization was evaluated. The key tRNA-derived fragments (tRFs) carried by exosomes were identified by small RNA sequencing and verified in clinical samples. The effect of exosomal-tRFs on macrophage polarization was examined. In this study, MSC-exo dramatically suppressed expression of M1 markers, and reduced the levels of TNF-α and IL-1β, while increased M2 markers in macrophages. A total of 243 differently expressed tRFs (DEtRFs) were identified between MSC-exo treated and untreated macrophage, among which 103 DEtRFs were up-regulated in response to MSC-exo treatment, including tsRNA-21109. The target genes of tsRNA-21109 were mainly enriched in DNA transcription-related GO function, and mainly involved in inflammatory-related pathways, including Rap1, Ras, Hippo, Wnt, MAPK, TGF-beta signaling pathway. The tsRNA-21109 was lowly expressed in clinical samples and was associated with the patient data in SLE. Compared to the normal MSC-exo, the tsRNA-21109-privative MSC-exo up-regulated M1 marker (CD80, NOS2, MCP1) and down-regulated M2 marker (CD206, ARG1, MRC2), also increased the levels of TNF-α and IL-1β in macrophages. Western blot and immunofluorescence confirmed that the proportion of CD80/ARG-1 was increased in macrophages treated with tsRNA-21109-privatived MSC-exo compared to that with control MSC-exo. In conclusion, MSC-exo inhibited the M1-type polarization of macrophages, possibly through transferring tsRNA-21109, which may develop as a novel therapeutic target for SLE.

系统性红斑狼疮 (SLE) 是一种慢性自身免疫性疾病，具有 M1 型巨噬细胞活化。间充质干细胞 (MSC) 疗法在与 SLE 相关的病理模型中显示出前景，而 MSC 衍生的外泌体 (MSC-exo) 的功能和机制仍不清楚。我们旨在探究 MSC-exo 对巨噬细胞 M1 型极化的影响，并研究 MSC-exo 的潜在机制。从 MSC 中分离外泌体并评估 MSC-exo 对巨噬细胞极化的影响。外泌体携带的关键 tRNA 衍生片段 (tRF) 通过小 RNA 测序鉴定并在临床样本中得到验证。检查了外泌体-tRFs对巨噬细胞极化的影响。在这项研究中，MSC-exo 显着抑制了 M1 标志物的表达，并降低了 TNF-α 和 IL-1β 的水平，同时增加巨噬细胞中的 M2 标记。在 MSC-exo 处理和未处理的巨噬细胞之间共鉴定出 243 个不同表达的 tRFs (DEtRFs)，其中 103 个 DEtRFs 响应于 MSC-exo 处理而上调，包括 tsRNA-21109。tsRNA-21109的靶基因主要富集DNA转录相关的GO功能，主要参与炎症相关通路，包括Rap1、Ras、Hippo、Wnt、MAPK、TGF-β信号通路。tsRNA-21109 在临床样本中低表达，并且与 SLE 中的患者数据相关。与正常的 MSC-exo 相比，tsRNA-21109-privative MSC-exo 上调 M1 标记（CD80、NOS2、MCP1）和下调 M2 标记（CD206、ARG1、MRC2），也增加了 TNF-巨噬细胞中的α和IL-1β。蛋白质印迹和免疫荧光证实，与对照 MSC-exo 相比，用 tsRNA-21109-privatived MSC-exo 处理的巨噬细胞中 CD80/ARG-1 的比例增加。总之，MSC-exo 抑制了巨噬细胞的 M1 型极化，可能是通过转移 tsRNA-21109，这可能会成为 SLE 的新治疗靶点。