| Background and ObjectiveSpinal Cord Injury(SCI)is a serious disabling disease that occurs in the central nervous system and is mostly caused by accidental injuries such as traffic injuries and war injuries.Spinal cord injury caused by the following serious segmental limb dysfunction,urinary bladder dysfunction,neuropathic pain,sphincter and autonomic dysfunction.The incidence of SCI in our country is relatively high,reaching 23.7-60.6 / 1000000.Sudden onset of SCI is common and the rate of life-long disability is high,which has a long-term and lasting negative impact on the life of patients and their families.It also brings a huge social burden.Astrocyte is a kind of supporting cell widely existing in the central nervous system.It has functions of supporting and guiding neuron migration,maintaining synaptic physiological function,forming blood-brain barrier and assisting neuronal metabolism in physiological state.After spinal cord injury,astrocytes in the resting state are activated excessively,secreting nerve inhibitors and extracellular matrix such as glial fibrillary acidic protein(GFAP)and collagen,leading to neuronal apoptosis and inflammation.Therefore,how to inhibit the over-activation of astrocytes and reduce the death of neurons after SCI is of great significance in the repair of SCI.Mesenchymal stem cells(MSCs)are pluripotent stem cells that have multidirectional differentiation potential and are one of the most frequently used cell types in cell transplantation for spinal cord injury.MSCs secrete a variety of neuroprotective trophic factors,also have a strong multi-target regulation of astrocyte activation.MSC derived exosomes(exosomes)are actively secreted by the MSCs in diameter of 40 ~ 100 nm vesicle body.It contains a variety of proteins,RNA,DNA,etc.,in cells to transduce information.MSCs exosomes can not only mimic the majority of MSCs biological functions,promote tissue repair and treatment of diseases,but also have advantages over MSCs in many aspects and therefore have broad clinical application prospects.In this study,exosomes derived from rat bone marrow-derived mesenchymal stem cells(BMSCs)were extracted and exosomes were applied to rats with experimental SCI via tail vein injection to detect hind limbs at specific time points after injury The recovery of motor function,the number of activated astrocytes and the residual neurons in the lesion,and to explore the impact of BMSCs derived exosomes on functional recovery and reactive astrocytes post spinal cord injury.Materials and MethodsBMSCs were cultured by whole bone marrow culture.The supernatant of BMSCs was collected and the exosomes were extracted and labeled by ultracentrifugation.The structures of the supernatant were observed by electron microscopy.The expression of CD63 and CD9 were detected by Western blot.Exosomes were applied to SCI rats and evaluated for hindlimb motor function(basso,beattie and bresnahan,BBB)at various time points after SCI.The rats were sacrificed at a predetermined time point,and the injured spinal cord segments were taken.Astrocyte activation and the number of residual neurons were evaluated by immunofluorescence assay.Results1.The cultured BMSCs positively expressed CD90,negatively expressed CD34.2.The extracted exosomes showed the shape of tea tray under the electron microscope,with a diameter of about 40-100 nm.The positive expression of CD63 and CD9 was detected by Western blot.3.The neurological function of the treatment group improved to a certain extent on the 14 th and 28 th day after operation,and the difference between the two groups was statistically significant(p <0.05).4.The number of reactive astrocytes on the 7th,14 th and 28 th day in the treatment group was significantly lower than that in the injury group(p <0.05).5.The number of residual neurons in the treatment group at 7d,14 d and 28 d after operation was higher than that at the corresponding time points(p <0.05).ConclusionExosomes secreted by BMSCs can reduce the number of activated astrocytes in the spinal cord injury area,reduce the death of neurons and improve the motor function of hind limbs. |
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