Department of Neurosurgery, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Hokkaido, Japan.
Regenerative Medicine and Cell Therapy Laboratories, Kaneka Corporation, Kobe 650-0047, Hyogo, Japan.
Int J Mol Sci. 2024 Feb 18;25(4):2406. doi: 10.3390/ijms25042406.
Spinal cord injury (SCI) leads to devastating sequelae, demanding effective treatments. Recent advancements have unveiled the role of neutrophil extracellular traps (NETs) produced by infiltrated neutrophils in exacerbating secondary inflammation after SCI, making it a potential target for treatment intervention. Previous research has established that intravenous administration of stem cell-derived exosomes can mitigate injuries. While stem cell-derived exosomes have demonstrated the ability to modulate microglial reactions and enhance blood-brain barrier integrity, their impact on neutrophil deactivation, especially in the context of NETs, remains poorly understood. This study aims to investigate the effects of intravenous administration of MSC-derived exosomes, with a specific focus on NET formation, and to elucidate the associated molecular mechanisms. Exosomes were isolated from the cell supernatants of amnion-derived mesenchymal stem cells using the ultracentrifugation method. Spinal cord injuries were induced in Sprague-Dawley rats (9 weeks old) using a clip injury model, and 100 μg of exosomes in 1 mL of PBS or PBS alone were intravenously administered 24 h post-injury. Motor function was assessed serially for up to 28 days following the injury. On Day 3 and Day 28, spinal cord specimens were analyzed to evaluate the extent of injury and the formation of NETs. Flow cytometry was employed to examine the formation of circulating neutrophil NETs. Exogenous miRNA was electroporated into neutrophil to evaluate the effect of inflammatory NET formation. Finally, the biodistribution of exosomes was assessed using Cu-labeled exosomes in animal positron emission tomography (PET). Rats treated with exosomes exhibited a substantial improvement in motor function recovery and a reduction in injury size. Notably, there was a significant decrease in neutrophil infiltration and NET formation within the spinal cord, as well as a reduction in neutrophils forming NETs in the circulation. In vitro investigations indicated that exosomes accumulated in the vicinity of the nuclei of activated neutrophils, and neutrophils electroporated with the miR-125a-3p mimic exhibited a significantly diminished NET formation, while miR-125a-3p inhibitor reversed the effect. PET studies revealed that, although the majority of the transplanted exosomes were sequestered in the liver and spleen, a notably high quantity of exosomes was detected in the damaged spinal cord when compared to normal rats. MSC-derived exosomes play a pivotal role in alleviating spinal cord injury, in part through the deactivation of NET formation via miR-125a-3p.
脊髓损伤 (SCI) 导致严重的后遗症,需要有效的治疗方法。最近的研究揭示了浸润中性粒细胞产生的中性粒细胞胞外诱捕网 (NETs) 在 SCI 后加重继发性炎症的作用,使其成为治疗干预的潜在靶点。先前的研究已经证实,干细胞衍生的外泌体的静脉内给药可以减轻损伤。虽然干细胞衍生的外泌体已被证明能够调节小胶质细胞反应并增强血脑屏障的完整性,但它们对中性粒细胞失活的影响,特别是在 NETs 的情况下,仍知之甚少。本研究旨在探讨静脉内给予 MSC 衍生的外泌体对 NET 形成的影响,并阐明相关的分子机制。使用超速离心法从羊膜衍生的间充质干细胞的细胞上清液中分离出外泌体。使用夹伤模型在 Sprague-Dawley 大鼠 (9 周龄) 中诱导脊髓损伤,在损伤后 24 小时静脉内给予 1 mL PBS 中的 100 μg 外泌体或 PBS 单独给药。在损伤后长达 28 天的时间内连续评估运动功能。在第 3 天和第 28 天,分析脊髓标本以评估损伤程度和 NET 形成情况。使用流式细胞术检查循环中性粒细胞 NET 的形成。将外源性 miRNA 电穿孔到中性粒细胞中,以评估炎症性 NET 形成的影响。最后,使用动物正电子发射断层扫描 (PET) 中的 Cu 标记的外泌体评估外泌体的生物分布。用外泌体治疗的大鼠表现出运动功能恢复的显著改善和损伤体积的减少。值得注意的是,脊髓内中性粒细胞浸润和 NET 形成显著减少,循环中形成 NET 的中性粒细胞减少。体外研究表明,外泌体聚集在活化中性粒细胞的核附近,电穿孔 miR-125a-3p 模拟物的中性粒细胞 NET 形成显著减少,而 miR-125a-3p 抑制剂逆转了这种作用。PET 研究表明,尽管大多数移植的外泌体被隔离在肝脏和脾脏中,但与正常大鼠相比,在受损的脊髓中检测到明显更多数量的外泌体。MSC 衍生的外泌体通过 miR-125a-3p 发挥缓解脊髓损伤的作用,部分通过抑制 NET 形成。
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