Human Umbilical Cord Mesenchymal Stem Cell Derived Exosomes Reduce The Permeability Of Blood Spinal Cord Barrier After Spinal Cord Injury By Regulating The Expression Of ET-1

Objective:To investigate whether exosomes produced by human umbilical cord mesenchymal stem cells can reduce the permeability of the blood-spinal barrier by inhibiting ET-1expression,thus repairing spinal cord injury.Methods:Exosomes were extracted by hyperspeed centrifugation method.The morphology of exosomes was observed by projective electron microscope.The expressions of tsg101 and CD63 were detected by Western blot.Eighty SD rats were randomly divided into sham operation group,model group,exosome group,and ET-1 group(n=20).The improved Allen’s method was used to create the model of spinal cord injury.In ET-1group,10 u L(1ug/ml)ET-1 was injected directly into the injured area with a microsyringe,immediately after operation,1 day,2 day,Sham operation group and model group were injected with 200 ul PBS solution through the tail vein,and exosome group and ET-1 group were injected with 200 ul exosome(200ug/ml)solution through the tail vein,respectively.Hind limb motor function scores were performed on days 1,3,7,14 and 21 after spinal cord injury.The blood-spinal barrier permeability was observed by Evans blue staining on the 7th day after SCI,and the expression of tight junction proteins β-Catenin,ZO-1,Occludin and ET-1 in spinal cord were detected by Western blot.Results:(1)BBB score in exosome group was significantly higher than that in model group at 3-21 days after injury(p<0.05).Hematoxylin-eosin staining in exosome group showed that spinal cord injury was greatly reduced compared with model group(p<0.05).BBB score in ET-1 group was significantly decreased compared with that in exosome group(p<0.05).Hematoxylin-eosin staining showed that spinal cord injury was more severe than that in exosome group(p<0.05).(2)The expression of ET-1 in the model group was considerably increased compared with that in the sham group(p<0.05),and the expression of ET-1 in the exosome group was remarkably decreased compared with that in the model group(p<0.05).(3)The blood-spinal barrier Evans blue exudate in exosome group was significantly decreased compared with model group(p<0.05),the tight junction proteins β-Catenin,Occludin and ZO-1 in exosome group were increased(p<0.05),and the Evans blue exudate in ET-1 group was significantly increased compared with exosome group(p<0.05).The expression level of tight junction protein was significantly decreased compared with exosome group(p<0.05).Conclusion:Human umbilical cord mesenchymal cell derived exosomes protect the permeability of the blood-spinal barrier by down-regulating the expression of ET-1,and play a role in the repair of spinal cord injury.