脂肪间充质干细胞对脓毒症小鼠的剂量特异性疗效。

BACKGROUND: Mesenchymal stem cells (MSCs) therapy for sepsis has been extensively studied in the past decade; however, the treatment regimen and mechanism of action of MSCs remain elusive. Here, we attempted to understand the efficacy and mechanism of action of MSCs on rescuing mice with sepsis. METHODS: A mouse model of sepsis was produced by cecal ligation and puncture (CLP). Allogeneic adipose-derived MSCs (ADSCs) were administered by intravenous infusion at 6 h after CLP, and dose-related effects of ADSCs on these mice were determined by survival rate, histopathological changes, biochemical and coagulation parameters, bacterial load, and plasma levels of endotoxin and inflammatory cytokines. The tissue distribution of intravenously infused ADSCs in septic mice was investigated by pre-labeling ADSCs with the lipophilic membrane dye PKH26. RNA sequencing analysis was performed to assess the transcriptional changes in peripheral blood mononuclear cells (PBMCs) and the liver. RESULTS: A significant therapeutic effect of ADSCs at a dose of 2 × 10 cells/kg in septic mice was evidenced by a remarkable reduction in mortality (35.89% vs. 8.89% survival rate), blood bacterial burden, systemic inflammation, and multiple organ damage. In contrast, ADSCs at a lower dose (1 × 10 cells/kg) failed to achieve any beneficial outcomes, while ADSCs at a higher dose (4 × 10 cells/kg) caused more early death within 24 h after CLP, retaining a steady survival rate of 21.42% thereafter. PKH26-labeled ADSCs were predominantly localized in the lungs of septic mice after intravenous infusion, with only a smaller proportion of PKH26-positive signals appearing in the liver and spleen. RNA sequencing analysis identified that insufficient phagocytic activity of PBMCs in addition to a hyperactivation of the hepatic immune response was responsible for the ineffectiveness of low-dose ADSCs therapy, and acute death caused by high-dose ADSCs infusion was associated with impaired coagulation signaling in PBMCs and exacerbated hepatic hypoxic injury. CONCLUSIONS: Our findings demonstrate a dose-specific effect of ADSCs on the treatment of sepsis due to dose-related interactions between exogenous stem cells and the host's microenvironment. Therefore, a precise dosing regimen is a prerequisite for ADSCs therapy for sepsis.

背景：间充质干细胞（MSCs）治疗脓毒症在过去十年中得到了广泛研究；然而，MSCs 的治疗方案和作用机制仍不清楚。在这里，我们试图了解 MSCs 对脓毒症小鼠的疗效和作用机制。

方法：通过盲肠结扎和穿孔（CLP）制备小鼠脓毒症模型。CLP 后 6 小时，通过静脉输注同种异体脂肪来源的间充质干细胞（ADSCs），通过存活率、组织病理学变化、生化和凝血参数、细菌负荷以及内毒素和炎症细胞因子的血浆水平来确定 ADSC 对这些小鼠的剂量相关作用。通过用亲脂性膜染料 PKH26 预先标记 ADSC 来研究静脉内输注的 ADSC 在脓毒症小鼠中的组织分布。进行 RNA 测序分析以评估外周血单核细胞（PBMC）和肝脏中的转录变化。

结果：在脓毒症小鼠中，ADSC 剂量为 2×10 个细胞/kg 时具有显著的治疗效果，死亡率显著降低（35.89%比 8.89%的存活率），血液细菌负荷、全身炎症和多器官损伤减少。相比之下，ADSC 低剂量（1×10 个细胞/kg）未能获得任何有益结果，而 ADCS 高剂量（4×10 个细胞/kg）在 CLP 后 24 小时内导致更多的早期死亡，此后保持 21.42%的稳定存活率。静脉内输注后，PKH26 标记的 ADSC 主要定位于脓毒症小鼠的肺部，只有较小比例的 PKH26 阳性信号出现在肝脏和脾脏中。RNA 测序分析表明，除了肝脏免疫反应的过度激活外，PBMC 的吞噬活性不足也是低剂量 ADSC 治疗无效的原因，而高剂量 ADSC 输注引起的急性死亡与 PBMC 中凝血信号受损和肝缺氧损伤加重有关。

结论：我们的研究结果表明，ADSC 对脓毒症的治疗具有剂量依赖性效应，这是由于外源性干细胞与宿主微环境之间的剂量相关相互作用所致。因此，精确的剂量方案是 ADSC 治疗脓毒症的前提。