Acquired forms of Aplastic anemia (AA) are characterized by T cell‐mediated immune disease resulting in bone marrow (BM) failure and marrow hypoplasia. In these cases, it is a major challenge to modulate autoreactive T cell activity and thereby decrease the pro‐inflammatory cytokine storm. Emerging evidence indicates that extracellular vesicles derived from mesenchymal stem cells (MSC‐EVs) control and modulate immunity. The therapeutic potential of MSC‐EVs has not been investigated in acquired AA. Hence, in this study, we constructed an AA mice model through irradiation and splenocyte infusion to test the benefits of hypoxic MSC‐EVs (Hx‐EVs) and normoxic MSC‐EVs (Nx‐EVs). We found that MSC‐EVs treatment significantly prolonged the survival rate and increased the platelet (PLT) counts of the AA mice. Immunohistochemical staining and colony assay confirmed amelioration of hypoplasia in the BM and increased numbers of hematopoietic stem cells (HSCs). These effects of MSC‐EVs were mediated by T cell suppression and inhibition of interferon‐gamma (IFN‐γ) and tumor necrosis factor‐alpha (TNF‐α) production in the AA mouse model. In addition, an in vitro study revealed that MSC‐EVs led to reduced IFN‐γ and TNF‐α levels and there was an association with decreased splenocyte viability. Previous studies examined the diagnostic and prognostic values of microRNAs (miRNAs) in AA and identified miR‐199a, miR‐146a, miR‐223, and miR‐126. We used quantitative real‐time PCR to evaluate the expression of these miRNAs on isolated BM mononuclear cells (BM‐MNCs) from treated and untreated AA mice. miR‐223, miR‐146a, and miR‐199a expressions increased in the MSC‐EVs treated AA mice. Treatment with MSC‐EVs increased expression of miR‐223 and miR‐146a. Our findings showed that treatment with MSC‐EVs significantly ameliorated immune destruction of HSCs in the AA mouse model and confirmed the importance of miRNAs in the clinical status of this model.

中文翻译：

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间充质干细胞衍生的细胞外囊泡有条件地改善免疫介导的再生障碍性贫血小鼠模型的骨髓衰竭症状

获得性再生障碍性贫血 (AA) 的特征是 T 细胞介导的免疫疾病，导致骨髓 (BM) 衰竭和骨髓发育不良。在这些情况下，调节自身反应性 T 细胞活性从而减少促炎细胞因子风暴是一项重大挑战。新出现的证据表明，源自间充质干细胞 (MSC-EV) 的细胞外囊泡控制和调节免疫。尚未在获得性 AA 中研究 MSC-EVs 的治疗潜力。因此，在本研究中，我们通过辐照和脾细胞输注构建了 AA 小鼠模型，以测试缺氧 MSC-EVs (Hx-EVs) 和常氧 MSC-EVs (Nx-EVs) 的益处。我们发现MSC-EVs治疗显着延长了AA小鼠的存活率并增加了血小板（PLT）计数。免疫组织化学染色和集落测定证实了 BM 发育不全的改善和造血干细胞 (HSC) 的数量增加。MSC-EVs 的这些作用是通过 T 细胞抑制和抑制 AA 小鼠模型中干扰素-γ（IFN-γ）和肿瘤坏死因子-α（TNF-α）的产生来介导的。此外，一项体外研究表明，MSC-EVs 导致 IFN-γ 和 TNF-α 水平降低，并且与脾细胞活力降低有关。先前的研究检查了 AA 中 microRNA (miRNA) 的诊断和预后价值，并确定了 miR-199a、miR-146a、miR-223 和 miR-126。我们使用定量实时 PCR 来评估这些 miRNA 在来自治疗和未治疗 AA 小鼠的分离的 BM 单核细胞 (BM-MNCs) 上的表达。miR-223、miR-146a、和 miR-199a 表达在 MSC-EVs 治疗的 AA 小鼠中增加。MSC-EVs 治疗增加了 miR-223 和 miR-146a 的表达。我们的研究结果表明，MSC-EVs 治疗显着改善了 AA 小鼠模型中 HSCs 的免疫破坏，并证实了 miRNAs 在该模型的临床状态中的重要性。