| ObjectiveSpinal Cord Injury(SCI)is a serious traumatic disease that poses a great threat to the health of patients due to its high incidence,high mortality,high disability and expensive cost of medicine.Epidemiological surveys show that the incidence of SCI in our country is higher than other countries,with incomplete statistics reaching 23.7-60.6/1 million.The pathological and physiological characteristics of SCI are that the spinal cord suffered by external forces,which causes secondary injury,resulting in ischemia,edema,hypoxia and inflammatory cascade reaction in the injured region.Recently,marrow mesenchymal stem cells(MSCs)transplantation is widely concerned in SCI treatment,which can inhibit inflammatory reaction and apoptosis after SCI,promote axonal and vascular regeneration,reduce astrocyte scar and cavitation,and promote motor function recovery.However,there are many problems in stem cell transplantation,such as teratogenic tumor,immune rejection,pulmonary embolism and so on.As an important means of intercellular interaction,exosomes can enter target cells by membrane receptor or endocytosis.Numerous studies have shown that the efficacy of intravenous MSCs is comparable to that of MSCs and plays a key role in the repair of central nervous system injuries.Stem cell-based exocrine gene therapy can improve the safety of gene therapy,so it is expected to be an alternative therapy.In this study,we extracted the exosomes of BMSCs and transplanted through the tail vein to observe the behavior and histological changes of rats before and after transplantation.The results provide experimental evidence for the treatment of nervous system injury by transplanting exosomes from BMSCs.MethodsBMSCs were purified from rat bone marrow and cultured in vitro,the exosomes were isolated and extracted by Exo Quick Precipitation kit from the cell supernatant,the exosome markers,CD9,CD63 were analyzed by using Western blot.The MSCs-Exosomes morphology was assessed by transmission electron microscopy(TEM).The rats were randomly divided into the following three groups(n=10/group): sham group,control group(SCI+PBS)and exosomes group(SCI+exosomes).1 hour after the operation,the rats were injected with 500 ?L exosomes or 500 ?L sterile phosphate solution.Neurological functions were evaluated by the Basso-Beattie-Bresnahan(BBB)score and the slope plate experiment score after modeling.The distribution of the exosomes in the damaged tissue was observed in 24 hours after surgery.Histomorphological changes of spinal cord were observed at 28 days after modeling by hematoxylin-eosin(HE)staining and luxol fast blue(LFB)staining,Survivor number of spinal cord tissue neurons was observed at 28 days after modeling by Nissl staining.Results1.A large number of vesicle-like structures were observed under transmission electron microscopy(TEM).The appearance of vesicle-like structures was round or similar.The membrane structure is obvious around the vesicles.The size distribution profile displayed a homogeneous population from 40~100nm.MSCs-Exosomes were found to express high levels of CD9,CD63 by using Western blot.2.The behavior score of rats was normal before operation.1 day after surgery,BBB score and sloping plate experiment score were normal in sham group of 19.90±0.74,75±3.33,but in control group and exosomes group were significantly lower than those in sham group(P<0.05),the scores of BBB in exosomes group were higher than those in control group(P<0.05)from 7 days after surgery,and the scores of slope plate experiment in exosomes group were higher than those in control group from 7 day after surgery(P<0.05).3.24 hours after transplantation,exosomes were observed in the injury spinal cord in the exosomes group under transmission electron microscope.HE,LFB and Nissl staining showed nerve cells with normal morphology in sham group at 28 days after modeling;in control group,spinal cord porosis,disorder of myelin sheath and necrosis of nerve cells were found.The injured spinal cord was restored better and the number of neuronal survival was better in exosomes group than that in control group.ConclusionExosomes released from marrow stem cells can alleviate the degree of tissue damage after SCI,which obviously promote the recovery of neuromotor function.and provide a new idea for the treatment of SCI by biological transplantation. |
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