Small extracellular vesicles from hypoxia-preconditioned bone marrow mesenchymal stem cells attenuate spinal cord injury via miR-146a-5p-mediated regulation of macrophage polarization

Spinal cord injury is a disabling condition with limited treatment options.Multiple studies have provided evidence suggesting that small extracellular vesicles(SEVs)secreted by bone marrow mesenchymal stem cells(MSCs)help mediate the beneficial effects conferred by MSC transplantation following spinal cord injury.Strikingly,hypoxia-preconditioned bone marrow mesenchymal stem cell-derived SEVs(HSEVs)exhibit increased therapeutic potency.We thus explored the role of HSEVs in macrophage immune regulation after spinal cord injury in rats and their significance in spinal cord repair.SEVs or HSEVs were isolated from bone marrow MSC supernatants by density gradient ultracentrifugation.HSEV administration to rats via tail vein injection after spinal cord injury reduced the lesion area and attenuated spinal cord inflammation.HSEVs regulate macrophage polarization towards the M2 phenotype in vivo and in vitro.Micro RNA sequencing and bioinformatics analyses of SEVs and HSEVs revealed that mi R-146a-5p is a potent mediator of macrophage polarization that targets interleukin-1 receptor-associated kinase 1.Reducing mi R-146a-5p expression in HSEVs partially attenuated macrophage polarization.Our data suggest that HSEVs attenuate spinal cord inflammation and injury in rats by transporting mi R-146a-5p,which alters macrophage polarization.This study provides new insights into the application of HSEVs as a therapeutic tool for spinal cord injury.

Mesenchymal stem cell-derived extracellular vesicles therapy in traumatic central nervous system diseases:a systematic review and meta-analysis

Although there are challenges in treating traumatic central nervous system diseases,mesenchymal stem cell-de rived extracellular vesicles(MSC-EVs) have recently proven to be a promising non-cellular the rapy.We comprehensively evaluated the efficacy of mesenchymal stem cell-de rived extracellular vesicles in traumatic central nervous system diseases in this meta-analysis based on preclinical studies.Our meta-analysis was registered at PROSPERO(CRD42022327904,May 24,2022).To fully retrieve the most relevant articles,the following databases were thoro ughly searched:PubMed,Web of Science,The Cochrane Library,and Ovid-Embase(up to April 1,2022).The included studies were preclinical studies of mesenchymal stem cell-derived extracellular vesicles for traumatic central nervous system diseases.The Systematic Review Centre for Laboratory Animal Experimentation(SYRCLE)’s risk of bias tool was used to examine the risk of publication bias in animal studies.After screening 2347studies,60 studies were included in this study.A meta-analysis was conducted for spinal co rd injury(n=52) and traumatic brain injury(n=8).The results indicated that mesenchymal stem cell-derived extracellular vesicles treatment prominently promoted motor function recovery in spinal co rd injury animals,including rat Basso,Beattie and Bresnahan locomotor rating scale scores(standardized mean difference [SMD]:2.36,95% confidence interval [CI]:1.96-2.76,P <0.01,I2=71%) and mouse Basso Mouse Scale scores(SMD=2.31,95% CI:1.57-3.04,P=0.01,I2=60%) compared with controls.Further,mesenchymal stem cell-de rived extracellular vesicles treatment significantly promoted neurological recovery in traumatic brain injury animals,including the modified N eurological Severity Score(SMD=-4.48,95% CI:-6.12 to-2.84,P <0.01,I2=79%) and Foot Fault Test(SMD=-3.26,95% CI:-4.09 to-2.42,P=0.28,I2=21%) compared with controls.Subgroup analyses showed that characteristics may be related to the therapeutic effect of mesenchymal stem cell-de rived extra cellular vesicles.For Basso,Beattie and Bresnahan locomotor rating scale scores,the efficacy of allogeneic mesenchymal stem cell-derived extracellular vesicles was higher than that of xenogeneic mesenchymal stem cell-derived extracellular vesicles(allogeneic:SMD=2.54,95% CI:2.05-3.02,P=0.0116,I2=65.5%;xenogeneic:SMD:1.78,95%CI:1.1-2.45,P=0.0116,I2=74.6%).Mesenchymal stem cellde rived extracellular vesicles separated by ultrafiltration centrifugation combined with density gradient ultra centrifugation(SMD=3.58,95% CI:2.62-4.53,P <0.0001,I2=31%) may be more effective than other EV isolation methods.For mouse Basso Mouse Scale scores,placenta-derived mesenchymal stem cell-de rived extracellular vesicles worked better than bone mesenchymal stem cell-derived extracellular vesicles(placenta:SMD=5.25,95% CI:2.45-8.06,P=0.0421,I2=0%;bone marrow:SMD=1.82,95% CI:1.23-2.41,P=0.0421,I2=0%).For modified Neurological Severity Score,bone marrow-derived MSC-EVs worked better than adipose-derived MSC-EVs(bone marrow:SMD=-4.86,95% CI:-6.66 to-3.06,P=0.0306,I2=81%;adipose:SMD=-2.37,95% CI:-3.73 to-1.01,P=0.0306,I2=0%).Intravenous administration(SMD=-5.47,95% CI:-6.98 to-3.97,P=0.0002,I2=53.3%) and dose of administration equal to 100 μg(SMD=-5.47,95% CI:-6.98 to-3.97,P <0.0001,I2=53.3%)showed better res ults than other administration routes and doses.The heterogeneity of studies was small,and sensitivity analysis also indicated stable results.Last,the methodological quality of all trials was mostly satisfactory.In conclusion,in the treatment of traumatic central nervous system diseases,mesenchymal stem cell-derived extracellular vesicles may play a crucial role in promoting motor function recovery.