背景:研究发现,内皮素参与了脊髓损伤后血脊髓屏障的破坏,干细胞来源外泌体可降低血脊髓屏障的通透性,修复脊髓损伤. 目的:观察人脐带间充质干细胞来源外泌体是否可以通过抑制内皮素1表达降低血脊髓屏障的通透性,进而修复脊髓损伤. 方法:用超速离心法从人脐带间充质干细胞培养上清液中提取外泌体,透射电子显微镜观察其形态,Western blot检测tsg101、CD63的表达.80只SD大鼠随机分成假手术组、模型组、外泌体组、内皮素1组(n=20),采用改良Allen's法制备大鼠脊髓损伤模型,内皮素1组用微量注射器直接向损伤部位注射10 μL(1 μg/mL)内皮素1,术后即刻及1,2 d,分别给予假手术组、模型组尾静脉注射200 μL PBS,外泌体组、内皮素1组尾静脉注射200 μL外泌体(200 μg/mL).脊髓损伤后第1,3,7,14,21天进行后肢运功功能评分;损伤后第7天通过伊文思蓝染色观察血脊髓屏障通透性,Western blot检测脊髓组织中紧密连接蛋白ZO-1、β-Catenin、Occludin和内皮素1的表达. 结果与结论:①外泌体组BBB评分在损伤后3-21 d显著高于模型组(P<0.05),苏木精-伊红染色显示外泌体组脊髓损伤较模型组明显减轻;内皮素1组BBB评分较外泌体组显著降低(P<0.05),内皮素1组脊髓损伤较外泌体组加重;②模型组内皮素1表达量较假手术组显著增加(P<0.05),外泌体组内皮素1表达量较模型组显著降低(P<0.05);③与模型组比较,外泌体组血脊髓屏障伊文思蓝渗出量显著减少(P<0.05),紧密连接蛋白β-Catenin、Occludin、ZO-1的表达增加(P<0.05);与外泌体组比较,内皮素1组伊文思蓝渗出量显著增加(P<0.05),上述紧密连接蛋白表达量显著减少(P<0.05);④结果表明,人脐带间充质细胞来源外泌体通过下调内皮素1表达来保护血脊髓屏障的通透性,起到了修复脊髓损伤的作用.
BACKGROUND:Endothelin has been found to be involved in the breakdown of the blood-spinal cord barrier after spinal cord injury,and stem cell-derived exosomes can reduce the permeability of the blood-spinal cord barrier and repair spinal cord injury. OBJECTIVE:To investigate whether exosomes produced by human umbilical cord mesenchymal stem cells can reduce the permeability of the blood-spinal cord barrier by inhibiting endothelin-1 expression,thus repairing spinal cord injury. METHODS:Exosomes were extracted from the cultured supernatant by the hyperspeed centrifugation method.The morphology of exosomes was observed by transmission electron microscope.The expression levels of tsg101 and CD63 were detected by western blot assay.Eighty SD rats were randomly divided into sham operation group,model group,exosome group,and endothelin-1 group(n=20).The modified Allen's method was used to create the rat model of spinal cord injury.In the endothelin-1 group,10 μL(1 μg/mL)endothelin-1 was injected directly into the injured area with a microsyringe.Immediately,1 day,2 days after operation,sham operation group and model group were injected with 200 μL PBS solution through the tail vein;the exosome group and endothelin-1 group were injected with 200 μL exosome(200 μg/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 cord barrier permeability was observed by Evans blue staining on day 7 after injury.The expression levels of tight junction proteins β-Catenin,ZO-1,Occludin and endothelin-1 in the spinal cord were detected by western blot assay. RESULTS AND CONCLUSION:(1)Basso-Beattie-Bresnahan score in the exosome group was significantly higher than that in the model group at 3-21 days after injury(P<0.05).Hematoxylin-eosin staining showed that spinal cord injury was greatly reduced in the exosome group compared with the model group.Basso-Beattie-Bresnahan score in the endothelin-1 group was significantly decreased compared with the exosome group(P<0.05).Spinal cord injury was more severe in the endothelin-1 group than that in the exosome group.(2)The expression of endothelin-1 in the model group was significantly increased compared with the sham operation group(P<0.05),and the expression of endothelin-1 in the exosome group was significantly decreased compared with the model group(P<0.05).(3)The blood-spinal cord barrier Evans blue exudate in the exosome group was significantly decreased compared with the model group(P<0.05).The expression levels of the tight junction proteins β-Catenin,Occludin and ZO-1 in the exosome group were increased(P<0.05);the Evans blue exudate in the endothelin-1 group was significantly increased compared with the exosome group(P<0.05).The expression level of tight junction protein was significantly decreased compared with the exosome group(P<0.05).(4)The results show that human umbilical cord mesenchymal cell-derived exosomes protect the permeability of the blood-spinal cord barrier by down-regulating the expression of endothelin-1 and play a role in the repair of spinal cord injury.