Mesenchymal stem cells (MSCs) constitute a promising therapy for spinal cord injury (SCI) because they can provide a favorable environment for the regrowth of neurons by inhibiting receptor-regulated Smads (R-Smads) expression in endogenous neural stem cells (NSCs). However, their mechanism of action and effect on the expression of inhibitory Smads (I-Smads) remain unclear. Herein, we demonstrated that extracellular vesicles (EVs) from MSCs were able to upregulate the Smad 6 expression by carrying TGF-β, and the Smad 6 knockdown in NSCs partially weakened the bone marrow MSC (BMSC)-EV-induced effect on neural differentiation. We found that the expression of Smad 6 did not reduced owing to the TGF-β type I receptor kinase inhibitor, SB 431,542, treatment in the acute phase of injury in rats with SCI, thereby indicating that the Smad 6 expression was not only mediated by TGF-β, but also by the inflammatory factors and bone morphogenetic proteins (BMPs) as well. However, in the later phase of SCI, the Smad 6 expression decreased by the addition of SB 431,542, suggesting that TGF-β plays a key role in the mediation of Smad 6 expression in this phase. In addition, immunohistochemistry staining; hematoxylin–eosin staining; and the Basso, Beattie, and Bresnahan (BBB) scores revealed that the early inhibition of TGF-β did not increase neuron regrowth. However, this inhibition increased the cavity and the caspase-3 expression at 24 h post-injury, leading to a worse functional outcome. Conversely, the later treatment with the TGF-β inhibitor promoted the regrowth of neurons around the cavity, resulting in a better neurological outcome. Together, these results indicate that Smad 6 acts as a feedback regulator to prevent the over-differentiation of NSCs to astrocytes and that BMSC-EVs can upregulate Smad 6 expression by carrying TGF-β. Graphical abstract

Spinal cord injury (SCI) often causes neuronal and axonal damage, resulting in permanent neurological impairments. Mesenchymal stem cells (MSCs) and extracellular vesicles (EVs) are promising treatments for SCI. However, the underlying mechanisms remain unclear. Herein, we demonstrated that EVs from bone marrow-derived MSCs promoted the differentiation of neural stem cells (NSCs) into the neurons and outgrowth of neurites that are extending into astrocytic scars in SCI rats. Further study found that let-7a-5p exerted a similar biological effect as MSC-EVs in regulating the differentiation of NSCs and leading to neurological improvement in SCI rats. Moreover, these MSC-EV-induced effects were attenuated by let-7a-5p inhibitors/antagomirs. When investigating the mechanism, bioinformatics predictions combined with western blot and RT-PCR analyses showed that both MSC-EVs and let-7a-5p were able to downregulate the expression of SMAD2 by inhibiting HMGA2. In conclusion, MSC-EV-secreted let-7a-5p promoted the regrowth of neurons and improved neurological recovery in SCI rats by targeting the HMGA2/SMAD2 axis.

Ewing sarcoma (ES) is a rare disease that lacks a prognostic prediction model. This study aims to develop a nomogram and risk classification system for estimating the probability of overall survival (OS) of patients with ES. The clinicopathological data of ES were collected from the Surveillance, Epidemiology and Final Results (SEER) database from 2010 to 2018. The primary cohort was randomly assigned to the training set and the validation set. Univariate and multiple Cox proportional hazard analyses based on the training set were performed to identify independent prognostic factors. A nomogram was established to generate individualized predictions of 3- and 5-year OS and evaluated by the concordance index (C-index), the receiver operating characteristic curve (ROC), the calibration curve, the integrated discrimination improvement (IDI) and the net reclassification improvement (NRI). Based on the scores calculated with the nomogram, ES patients were divided into three risk groups to predict their survival. A total of 935 patients were identified, and a nomogram consisting of 6 variables was established. The model provided better C-indices of OS (0.788). The validity of the Cox model assumptions was evaluated through the Schönfeld test and deviance residual. The ROC, calibration curve, IDI and NRI indicated that the nomogram exhibited good performance. A risk classification system was built to classify the risk group of ES patients. The nomogram compares favourably and accurately to the traditional SEER tumour staging systems, and risk stratification provides a more convenient and effective tool for clinicians to optimize treatment options.

Background Endogenous neural stem cells (NSCs) are critical for the remyelination of axons following spinal cord injury (SCI). Cell–cell communication plays a key role in the regulation of the differentiation of NSCs. Astrocytes act as immune cells that encounter early inflammation, forming a glial barrier to prevent the spread of destructive inflammation following SCI. In addition, the cytokines released from astrocytes participate in the regulation of the differentiation of NSCs. The aim of this study was to investigate the effects of cytokines released from inflammation-stimulated astrocytes on the differentiation of NSCs following SCI and to explore the influence of these cytokines on NSC–NSC communication. Results Lipopolysaccharide stimulation of astrocytes increased bone morphogenetic protein 2 (BMP2) release, which not only promoted the differentiation of NSCs into astrocytes and inhibited axon remyelination in SCI lesions but also enriched miRNA-22-3p within extracellular vesicles derived from NSCs. These miRNA-22 molecules function as a feedback loop to promote NSC differentiation into oligodendrocytes and the remyelination of axons following SCI by targeting KDM3A. Conclusions This study revealed that by releasing BMP2, astrocytes were able to regulate the differentiation of NSCs and NSC–NSC communication by enriching miRNA-22 within NSC-EVs, which in turn promoted the regeneration and remyelination of axons by targeting the KDM3A/TGF-beta axis and the recovery of neurological outcomes following SCI.

Cell‒cell communication following spinal cord injury (SCI) plays a key role in remyelination and neurological recovery. Although communication between neuron-neural stem cells (NSCs) affects remyelination, its precise mechanism remains unclear. The present study investigated the biological effects of extracellular vesicles (EVs) derived from neurons on the differentiation of NSCs and the remyelination of axons in a rat model for SCI. We found that that EVs derived from neurons promoted the differentiation of NSCs into oligodendrocytes and the remyelination of axons in SCI rats. However, neuron-derived EVs lost their biological effects after inflammatory stimulation of these neurons from which they originate. Further analysis demonstrated that the inflammatory stimulation on neurons upregulated miR-21 within EVs, which targeted SMAD 7 and upregulated the TGF-β/SMAD2 signaling pathway, resulting in an excess of astrocytic scar boundaries and in remyelination failure. Moreover, these effects could be abolished by miR-21 inhibitors/antagomirs. Considered together, these results indicate that inflammatory stimulation of neurons prevents remyelination following SCI via the upregulation of miR-21 expression within neuron-derived EVs, and this takes place through SMAD 7-mediated activation of the TGF-β/SMAD2 signaling pathway.