| Objective: Traumatic brain injury(TBI)is a major cause of death and disability in humans.Despite the current improvement in medical conditions,there is no effective medications that can be used to reduce the mortality rate of TBI and to significantly improve the recovery of patients’ function due to the near failure of clinical trial II / III of TBI.In recent years,therapies for the treatment of traumatic brain injury,including bone marrow mesenchymal stem cells(MSCs),have highlighted the hope.Exogenous MSCs can selectively target damaged tissues(homing)and interact with brain parenchymal cells,thereby reducing the expression of axon inhibitory molecules,promoting neurite outgrowth and neurological repair.Recent studies have found that the therapeutic effect of MSC is through the production and release of large numbers of exosomes.Exosomes are intracellularly released small molecular membrane material with a diameter of 30nm-100 nm.All cells can secrete exosomes.Exosomes are present in body fluids(blood,urine,milk).It can be released by living cells to the outside.The initial function of exosomes is thought to be the elimination of nonfunctional proteins in cells,but the current view is that exosomes are vesicles that are cell-specifically secreted and are involved in intercellular communication.Recent studies have found that exosomes can also transmit RNA and other substances.They play a key role in angiogenesis,immune regulation and tissue growth.Studies have shown that exosomes released by MSC can promote angiogenesis and repair of nerve regeneration after brain injury.However,the role of apoptotic neurons in MSC after TBI and its mechanism of action have not yet been studied.Methods: 1.The exosomes derived from MSCs were studied by electron microscopy,nanosight and protein electrophoresis.2.C57 / BL6 mice were randomly divided into sham group,control group(TBI + PBS)Intervention group(TBI + EXO).Every group was randomly divided into 6 mice,PBS and EXO were injected into the mice via tail vein;3,The mNSS score and Beam walking latency score of each group on the 3rd day after the model was established to further evaluate the functional prognosis of mice 4,The mice were sacrificed 3 days after modeling to take brain,immersed in 4% paraformaldehyde after 24 hours gradient concentration(5%,10%)sucrose dehydration,taking the brain tissue surrounding the bilateral trauma was embedded and frozen sections.The expression of TUNEL in the tissue cells was detected by immunofluorescence staining.5.Western Blot was used to detect the relative changes of apoptotic proteins in the tissue;6,Interfering bone marrow mesenchymal stem cells by transfection,knocking up the intracellular microRNA-146 a content and collecting the secreted exosomes to further intervention TBI mice,mice were randomly grouped into sham group,TBI+PBS group,TBI+EXO(knocking up)group,PBS and EXO were injected into the mice via tail vein.The mice were sacrificed 3 days after modeling to take brain.Western Blot was used to detect the relative changes of apoptotic proteins in the tissue.Results: The mouse functional score(mNSS score and Beam walking latency score)both showed that MSC-derived exosome-treated mice had a better prognosis than the control group.By immunofluorescence,we found that the positive rate of TUNEL in the intervention group was lower than the control group(P <0.05).Furthermore,we knocked up miRNA-146 a in MSC and compared the change of Annexin V positive rate in brain tissue.We found that compared with sham group,the expression of Annexin V in TBI + PBS group and TBI + EXO-miRNA group were higher(P <0.05).However,the positive rate of Annexin V in TBI + EXO-miRNA group was lower than that in TBI + PBS group,and the differences of them were statistically significant(p <0.05).Conclusion: Bone marrow mesenchymal stem cell-derived exosomes after TBI can carry miRNA to targete migration to damaged tissue,and inhibit the occurrence of apoptosis through miRNA146 a. |
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