Department of Orthopaedics, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, Jiangsu, China.
Department of Orthopaedics, West China Hospital Sichuan University, Chengdu, 610000, Sichuan, China.
Cell Death Dis. 2019 Apr 18;10(5):340. doi: 10.1038/s41419-019-1571-8.
Spinal cord injury (SCI) can cause severe irreversible motor dysfunction and even death. Neural stem cell (NSC) transplantation can promote functional recovery after acute SCI in experimental animals, but numerous issues, including low-transplanted cell survival rate, cell de-differentiation, and tumor formation need to be resolved before routine clinical application is feasible. Recent studies have shown that transplanted stem cells facilitate regeneration through release of paracrine factors. Small extracellular vesicles (sEVs), the smallest known membrane-bound nanovesicles, are involved in complex intercellular communication systems and are an important vehicle for paracrine delivery of therapeutic agents. However, the application of NSC-derived small extracellular vesicles (NSC-sEVs) to SCI treatment has not been reported. We demonstrate that NSC-sEVs can significantly reduce the extent of SCI, improve functional recovery, and reduce neuronal apoptosis, microglia activation, and neuroinflammation in rats. Furthermore, our study suggests that NSC-sEVs can regulate apoptosis and inflammatory processes by inducing autophagy. In brief, NSC-sEVs increased the expression of the autophagy marker proteins LC3B and beclin-1, and promoted autophagosome formation. Following NSC-sEV infusion, the SCI area was significantly reduced, and the expression levels of the proapoptotic protein Bax, the apoptosis effector cleaved caspase-3, and the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 were significantly reduced, whereas the expression level of the anti-apoptotic protein Bcl-2 was upregulated. In the presence of the autophagy inhibitor 3MA, however, these inhibitory effects of NSC-sEVs on apoptosis and neuroinflammation were significantly reversed. Our results show for the first time that NSC-sEV treatment has the potential to reduce neuronal apoptosis, inhibit neuroinflammation, and promote functional recovery in SCI model rats at an early stage by promoting autophagy.
脊髓损伤（SCI）可导致严重的不可逆运动功能障碍，甚至死亡。神经干细胞（NSC）移植可以促进实验动物急性 SCI 后的功能恢复，但在常规临床应用可行之前，还需要解决许多问题，包括移植细胞存活率低、细胞去分化和肿瘤形成。最近的研究表明，移植的干细胞通过释放旁分泌因子促进再生。小细胞外囊泡（sEVs）是已知最小的膜结合纳米囊泡，参与复杂的细胞间通讯系统，是旁分泌递药的重要载体。然而，尚未有报道将 NSC 衍生的小细胞外囊泡（NSC-sEVs）应用于 SCI 治疗。我们证明 NSC-sEVs 可显著减轻 SCI 程度，改善功能恢复，并减少大鼠神经元凋亡、小胶质细胞激活和神经炎症。此外，我们的研究表明，NSC-sEVs 可以通过诱导自噬来调节凋亡和炎症过程。简而言之，NSC-sEVs 增加了自噬标记蛋白 LC3B 和 beclin-1 的表达，并促进了自噬体的形成。在 NSC-sEV 输注后，SCI 区域明显缩小，促凋亡蛋白 Bax、凋亡效应子 cleaved caspase-3 和促炎细胞因子 TNF-α、IL-1β 和 IL-6 的表达水平显著降低，而抗凋亡蛋白 Bcl-2 的表达水平上调。然而，在自噬抑制剂 3MA 的存在下，NSC-sEVs 对凋亡和神经炎症的抑制作用明显逆转。我们的结果首次表明，NSC-sEV 治疗通过促进自噬，具有减少神经元凋亡、抑制神经炎症和促进 SCI 模型大鼠早期功能恢复的潜力。
