Acute radiation syndrome (ARS) is caused by acute exposure to ionizing radiation that damages multiple organ systems but especially the bone marrow (BM). We have previously shown that human macrophages educated with exosomes from human BM-derived mesenchymal stromal cells (MSCs) primed with lipopolysaccharide (LPS) prolonged survival in a xenogeneic lethal ARS model. The purpose of this study was to determine if exosomes from LPS-primed MSCs could directly educate human monocytes (LPS-EEMos) for the treatment of ARS. Human monocytes were educated by exosomes from LPS-primed MSCs and compared to monocytes educated by unprimed MSCs (EEMos) and uneducated monocytes to assess survival and clinical improvement in a xenogeneic mouse model of ARS. Changes in surface molecule expression of exosomes and monocytes after education were determined by flow cytometry, while gene expression was determined by qPCR. Irradiated human CD34+ hematopoietic stem cells (HSCs) were co-cultured with LPS-EEMos, EEMos, or uneducated monocytes to assess effects on HSC survival and proliferation. LPS priming of MSCs led to the production of exosomes with increased expression of CD9, CD29, CD44, CD146, and MCSP. LPS-EEMos showed increases in gene expression of IL-6, IL-10, IL-15, IDO, and FGF-2 as compared to EEMos generated from unprimed MSCs. Generation of LPS-EEMos induced a lower percentage of CD14+ monocyte subsets that were CD16+, CD73+, CD86+, or CD206+ but a higher percentage of PD-L1+ cells. LPS-EEMos infused 4 h after lethal irradiation significantly prolonged survival, reducing clinical scores and weight loss as compared to controls. Complete blood counts from LPS-EEMo-treated mice showed enhanced hematopoietic recovery post-nadir. IL-6 receptor blockade completely abrogated the radioprotective survival benefit of LPS-EEMos in vivo in female NSG mice, but only loss of hematopoietic recovery was noted in male NSG mice. PD-1 blockade had no effect on survival. Furthermore, LPS-EEMos also showed benefits in vivo when administered 24 h, but not 48 h, after lethal irradiation. Co-culture of unprimed EEMos or LPS-EEMos with irradiated human CD34+ HSCs led to increased CD34+ proliferation and survival, suggesting hematopoietic recovery may be seen clinically. LPS-EEMos are a potential counter-measure for hematopoietic ARS, with a reduced biomanufacturing time that facilitates hematopoiesis.

中文翻译：

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来自引发的 MSCs 的外泌体可以培养单核细胞作为造血急性放射综合征的细胞疗法

急性辐射综合征 (ARS) 是由急性暴露于电离辐射引起的，电离辐射会损害多个器官系统，尤其是骨髓 (BM)。我们之前已经表明，用脂多糖 (LPS) 引发的人 BM 间充质基质细胞 (MSC) 的外泌体培养的人巨噬细胞在异种致死 ARS 模型中延长了存活期。本研究的目的是确定来自 LPS 引发的 MSC 的外泌体是否可以直接培养人单核细胞 (LPS-EEMos) 用于治疗 ARS。人单核细胞由来自 LPS 引发的 MSCs 的外泌体教育，并与由未引发的 MSCs (EEMos) 和未教育的单核细胞教育的单核细胞进行比较，以评估 ARS 异种小鼠模型的存活率和临床改善。教育后外泌体和单核细胞表面分子表达的变化通过流式细胞仪测定，而基因表达则通过 qPCR 测定。将受辐照的人类 CD34+ 造血干细胞 (HSC) 与 LPS-EEMos、EEMos 或未受教育的单核细胞共培养，以评估对 HSC 存活和增殖的影响。MSCs 的 LPS 引发导致外泌体的产生，CD9、CD29、CD44、CD146 和 MCSP 的表达增加。与未引发的 MSCs 产生的 EEMos 相比，LPS-EEMos 显示 IL-6、IL-10、IL-15、IDO 和 FGF-2 的基因表达增加。LPS-EEMos 的产生诱导了较低百分比的 CD14+ 单核细胞亚群，即 CD16+、CD73+、CD86+ 或 CD206+，但诱导了较高百分比的 PD-L1+ 细胞。致死辐射后 4 小时输注 LPS-EEMos 可显着延长生存期，与对照组相比，减少临床评分和体重减轻。LPS-EEMo 处理小鼠的全血细胞计数显示最低点后造血恢复增强。IL-6 受体阻断完全消除了 LPS-EEMos 在雌性 NSG 小鼠体内的辐射保护生存益处，但在雄性 NSG 小鼠中仅注意到造血恢复的损失。PD-1 阻断对生存没有影响。此外，LPS-EEMos 在致死照射后 24 小时而非 48 小时给药时也显示出体内益处。未引发的 EEMos 或 LPS-EEMos 与受照射的人 CD34+ HSC 的共培养导致 CD34+ 增殖和存活增加，表明临床上可以看到造血恢复。LPS-EEMos 是造血 ARS 的潜在对抗措施，其生物制造时间缩短，有利于造血。