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.

Pathologically, blood-spinal-cord-barrier (BSCB) disruption after spinal cord injury (SCI) leads to infiltration of numerous peripheral macrophages into injured areas and accumulation around newborn vessels. Among the leaked macrophages, M1-polarized macrophages are dominant and play a crucial role throughout the whole SCI process. The aim of our study was to investigate the effects of M1-polarized bone marrow-derived macrophages (M1-BMDMs) on vascular endothelial cells and their underlying mechanism. Microvascular endothelial cell line bEnd.3 cells were treated with conditioned medium or exosomes derived from M1-BMDMs, followed by evaluations of endothelial-to-mesenchymal transition (EndoMT) and mitochondrial function. After administration, we found conditioned medium or exosomes from M1-BMDMs significantly promoted EndoMT of vascular endothelial cells in vitro and in vivo, which aggravated BSCB disruption after SCI. In addition, significant dysfunction of mitochondria and accumulation of reactive oxygen species (ROS) were also detected. Furthermore, bioinformatics analysis demonstrated that miR-155 is upregulated in both M1-polarized macrophages and microglia. Experimentally, exosomal transfer of miR-155 participated in M1-BMDMs-induced EndoMT and mitochondrial ROS generation in bEnd.3 cells, and subsequently activated the NF-κB signaling pathway by targeting downstream suppressor of cytokine signaling 6 (SOCS6), and suppressing SOCS6-mediated p65 ubiquitination and degradation. Finally, a series of rescue assay further verified that exosomal miR155/SOCS6/p65 axis regulated the EndoMT process and mitochondrial function in vascular endothelial cells. In summary, our work revealed a potential mechanism describing the communications between macrophages and vascular endothelial cells after SCI which could benefit for future research and aid in the development of potential therapies for SCI.

Osteosarcoma (OS) is a malignant bone tumor that mainly occurs in adolescents. It is accompanied by a high rate of lung metastasis, and high mortality. Recent studies have suggested the important roles of tripartite motif-containing (TRIM) family proteins in regulating various substrates and signaling pathways in different tumors. However, the detailed functional role of TRIM family proteins in the progression of OS is still unknown and requires further investigations. In this study, we found that tripartite motif-containing 22 (TRIM22) was downregulated in OS tissues and was hence associated with better prognosis. In vitro and in vivo functional analysis demonstrated that TRIM22 inhibits proliferation and metastasis of OS cells. Nuclear factor erythroid 2-related factor 2 (NRF2), a redox regulator, was identified as a novel target for TRIM22. TRIM22 interacts with and accelerates the degradation of NRF2 by inducing its ubiquitination dependent on its E3 ligase activity but independent of Kelch-like ECH-associated protein 1 (KEAP1). Further, a series of gain- and loss-of-function experiments showed that knockdown or overexpression of NRF2 reversed the functions of knockdown or overexpression of TRIM22 in OS. Mechanistically, TRIM22 inhibited OS progression through NRF2-mediated intracellular reactive oxygen species (ROS) imbalance. ROS production was significantly promoted and mitochondrial potential was remarkably inhibited when overexpressing TRIM22, thus activating AMPK/mTOR signaling. Moreover, TRIM22 was also found to inhibit Warburg effect in OS cells. Autophagy activation was found in OS cells which were overexpressed TRIM22, thus leading to autophagic cell death. Treatment with N-Acetylcysteine (NAC), a ROS scavenger or the autophagy inhibitor 3-Methyladenine (3-MA) abolished the decreased malignant phenotypes in TRIM22 overexpressing OS cells. In conclusion, our study indicated that TRIM22 inhibits OS progression by promoting proteasomal degradation of NRF2 independent of KEAP1, thereby activating ROS/AMPK/mTOR/Autophagy signaling that leads to autophagic cell death in OS. Therefore, our findings indicated that targeting TRIM22/NRF2 could be a promising therapeutic target for treating OS.