Exosomal miR-9-5p derived from BMSCs alleviates apoptosis, inflammation and endoplasmic reticulum stress in spinal cord injury by regulating the HDAC5/FGF2 axis.

Exosomes derived from human bone marrow mesenchymal stem cells (BMSCs) play potential protective roles in spinal cord injury (SCI). However, the underlying mechanisms remain not fully elucidated. Herein, we isolated exosomes from BMSCs, and exosome morphology and marker protein levels were identified by transmission electron microscopy (TEM) and Western blot, respectively. PC12 cells were treated with lipopolysaccharide (LPS) to construct an injury model, and then incubated with BMSCs-derived exosomes. We found that exosome incubation increased miR-9-5p expression, and inhibited apoptosis and the levels of inflammation cytokines and ER stress marker proteins. Moreover, histone deacetylase 5 (HDAC5) was identified as a target gene of miR-9-5p by dual-luciferase reporter gene assay. Exosomal miR-9-5p upregulated fibroblast growth factor 2 (FGF2) expression by inhibiting HDAC5-mediated FGF2 deacetylation. Then, it was observed that HDAC5 overexpression or FGF2 inhibition reversed the inhibitory effects of exosomal miR-9-5p on apoptosis, inflammation and ER stress in PC12 cells. Additionally, an SCI rat model was established and exosomes were injected for treatment. Exosomal miR-9-5p treatment alleviated locomotor ability, histopathological damage, neuronal apoptosis, inflammation and ER stress in SCI rats. In conclusion, our findings indicated that exosomal miR-9-5p derived from BMSCs promoted FGF2 expression by inhibiting HDAC5-mediated deacetylation, thus inhibiting LPS-induced apoptosis, inflammation, and ER stress in PC12 cells, and alleviating SCI in rat model. Our study may provide a therapeutic direction for SCI.

He X ，Zhang J ，Guo Y ，Yang X ，Huang Y ，Hao D ... -  《-》

BMSC-Derived Exosomes Carrying miR-26a-5p Ameliorate Spinal Cord Injury via Negatively Regulating EZH2 and Activating the BDNF-TrkB-CREB Signaling.

Spinal cord injury (SCI) is a destructive neurological and pathological state that causes major motor, sensory and autonomic dysfunctions. Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes show great therapeutic potential for SCI. Exosomes derived from miR-26a-modified MSCs promote axonal regeneration following SCI. Our study aims to uncover the mechanisms by which BMSC-derived exosomes carrying miR-26a-5p regulate SCI. BMSCs and BMSC-derived exosomes were isolated and characterized by Oil Red O and alizarin red staining, transmission electron microscopy, flow cytometry, nanoparticle tracking analysis and Western blotting. PC12 cells were treated with lipopolysaccharides (LPS), and SCI was established through laminectomy with contusion injury in rats. Annexin-V staining, CCK-8 and EdU incorporation were applied to determine cell apoptosis, viability, and proliferation. Hematoxylin and Eosin, Nissl and TUNEL staining was used to evaluate SCI injury and apoptosis in the spinal cord. Luciferase and chromatin immunoprecipitation assays were applied to evaluate gene interaction. BMSC-derived exosomes facilitated LPS-treated PC12 cell proliferation and inhibited apoptosis by delivering miR-26a-5p. Moreover, BMSC-derived exosomal miR-26a-5p alleviated SCI. Furthermore, miR-26a-5p inhibited EZH2 expression by directly binding to EZH2, and EZH2 inhibited BDNF expression via promoting H3K27me3. Increased phosphorylated CREB enhanced KCC2 transcription and expression by binding to its promoter. Knockdown of miR-26a-5p abrogated BMSC-derived exosome-mediated protection in LPS-treated PC12 cells, but it was reversed by KCC2 overexpression. BMSC-derived exosomes carrying miR-26a-5p repressed EZH2 expression to promote BDNF and TrkB expression and CREB phosphorylation and subsequently increase KCC2 expression, thus protecting PC12 cells and ameliorating SCI.

Chen M ，Lin Y ，Guo W ，Chen L ... -  《-》

Mesenchymal stem cell-derived exosomes containing miR-145-5p reduce inflammation in spinal cord injury by regulating the TLR4/NF-κB signaling pathway.

Jiang Z ，Zhang J 《-》

Overexpression of miR-338-5p in exosomes derived from mesenchymal stromal cells provides neuroprotective effects by the Cnr1/Rap1/Akt pathway after spinal cord injury in rats.

Growing evidence has shown that microRNAs (miRNAs) play crucial roles in the physiopathology of spinal cord injury (SCI). Recent studies have confirmed that miR-338-5p regulates myelination, suggesting a potential role in the treatment of SCI. However, the molecular mechanism of miR-338-5p on SCI is still unknown. Recently, exosomes have emerged as an ideal vector to deliver therapeutic molecules such as miRNAs. Here, we explored the effects of miR-338-5p-overexpressing exosomes derived from bone marrow-derived mesenchymal stromal cells (BMSCs) on SCI. In vivo, a model of contusion SCI in rats was established, and we observed that overexpression of miR-338-5p in exosomes profoundly increased the expression levels of neurofilament protein-M and growth-associated protein-43 and decreased those of myelin-associated glycoprotein and glial fibrillary acidic protein, which provided neuroprotective effects after acute SCI. In an in vitro study, we found that overexpression of miR-338-5p in exosomes repressed cell apoptosis following H2O2-induced oxidative stress injury in PC12 cells. Additionally, we confirmed that cannabinoid receptor 1 (Cnr1) was the target gene of miR-338-5p by dual-luciferase reporter assays and that Rap1 was the downstream gene by the KEGG pathway analysis. We found that miR-338-5p increased cAMP accumulation as a consequence of downregulated expression of the target gene Cnr1, and then, Rap1 was activated by cAMP. Eventually, the activation of the PI3K/Akt pathway attenuated cell apoptosis and promoted neuronal survival by cAMP-mediated Rap1 activation. In brief, these findings showed that exosomes overexpressing miR-338-5p were a promising treatment strategy for SCI.

Zhang A ，Bai Z ，Yi W ，Hu Z ，Hao J ... -  《-》

BMSC-derived exosomal miR-219-5p alleviates ferroptosis in neuronal cells caused by spinal cord injury via the UBE2Z/NRF2 pathway.

The aim of this study was to investigate the molecular mechanism of exosomal miR-219-5p derived from bone marrow mesenchymal stem cells (BMSCs) in the treatment of spinal cord injury (SCI). Basso Beattie Bresnahan (BBB) score and tissue staining were used to assess SCI and neuronal survival in rats. The contents of Fe2+, malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) were detected by a kit. The expression levels of ubiquitin-conjugating enzyme E2 Z (UBE2Z), nuclear factor erythroid 2-related Factor 2 (NRF2) and ferroptosis-related proteins were detected by Western blotting. In addition, the ability of BMSC-derived exosomes to inhibit ferroptosis in neuronal cells in rats with SCI was validated by in vivo injection of ferroptosis inhibitors/inducers. In this study, we found that miR-219-5p-rich BMSC-derived exosomes inhibited ferroptosis in SCI rats and that the alleviating effect of BMSC-Exos on SCI was achieved by inhibiting the ferroptosis signaling pathway and that NRF2 played a key role in this process. Our study confirmed that BMSC exosome-specific delivery of miR-219-5p can target UBE2Z to regulate its stability and that overexpression of UBE2Z reverses miR-219-5p regulation of NRF2. In addition, in vivo experiments showed that BMSC exosomes alleviated ferroptosis in neuronal SCI progression, and inhibiting the expression of miR-219-5p in BMSCs reduced the alleviating effect of exosomes on ferroptosis in neuronal cells and SCI. miR-219-5p in BMSC-derived exosomes can repair the injured spinal cord. In addition, miR-219-5p alleviates ferroptosis in neuronal cells induced by SCI through the UBE2Z/NRF2 pathway.

Dong J ，Gong Z ，Bi H ，Yang J ，Wang B ，Du K ，Zhang C ，Chen L ... -  《-》