脂肪间充质干细胞来源外泌体调节肝星状细胞自噬的机制

Mechanism of adipose tissue-derived mesenchymal stem cell-derived exosomes regulating autophagy of hepatic stellate cells

背景:脂肪间充质干细胞可释放大量外泌体参与各种病理生理过程,关于脂肪间充质干细胞源性外泌体对肝星状细胞自噬的影响以及具体机制还有待于深入研究。目的:探讨脂肪间充质干细胞源性外泌体通过miR-15a-5p对肝星状细胞自噬的靶向调控作用及分子机制。方法:收集8周龄雄性C57BL/6小鼠腹股沟区脂肪组织,使用胶原酶消化法分离提取脂肪间充质干细胞,使用超速离心法提取脂肪间充质干细胞源性外泌体;取小鼠肝脏组织,使用胶原酶灌注消化法和密度梯度离心法分离提取肝星状细胞。实验分2组:对照组肝星状细胞常规培养48 h,外泌体组将肝星状细胞与脂肪间充质干细胞源性外泌体共培养48 h。通过Western blot、RT-qPCR和免疫荧光染色观察外泌体对肝星状细胞增殖活化、自噬及纤维化标志物表达的影响。RT-qPCR及Western blot检测外泌体对肝星状细胞中miR-15a-5p以及下游信号通路Bcl-2、Beclin-1和Rubicon mRNA和蛋白表达的影响。结果与结论:①与对照组相比,外泌体组肝星状细胞中自噬标志物LC3-Ⅱ表达下降,自噬小体数目显著减少,脂滴重新生成,细胞体积减小同时增殖能力减弱,肝星状细胞活化明显受到抑制;②与对照组相比,外泌体组肝星状细胞中α-平滑肌动蛋白和Ⅰ型胶原蛋白表达显著下降(P<0.01),miR-15a-5p表达显著增高(P<0.01),同时其下游靶基因Bcl-2表达显著下降(P<0.01),而自噬基因Beclin-1和Rubicon表达显著增高(P<0.01)。结果提示:脂肪间充质干细胞源性外泌体通过miR-15a-5p靶向抑制肝星状细胞中Bcl-2表达,促进其下游自噬基因Beclin-1、Rubicon表达,从而抑制肝星状细胞自噬。

BACKGROUND:Adipose tissue-derived mesenchymal stem cells release a large amount of exosomes to participate in various pathophysiological processes,but the impact and precise mechanism of exosomes derived from adipose tissue-derived mesenchymal stem cells on autophagy of hepatic stellate cells have not been fully elucidated.OBJECTIVE:To explore the targeted regulatory effect and molecular mechanism of adipose tissue-derived mesenchymal stem cell-derived exosomes on autophagy of hepatic stellate cells through miR-15a-5p.METHODS:Adipose tissue was collected from inguinal region of 8-week male C57BL/6 mice.Adipose tissue-derived mesenchymal stem cells were extracted by collagenase digestion.Adipose tissue-derived mesenchymal stem cell-derived exosomes were extracted by ultracentrifugation.Mouse liver tissue was obtained,and hepatic stellate cells were isolated and extracted using collagenase perfusion digestion and density gradient centrifugation.The experiment was divided into two groups.In control group,hepatic stellate cells were cultured alone for 48 hours.In the exosome group,hepatic stellate cells were co-cultured with adipose tissue-derived mesenchymal stem cell-derived exosomes for 48 hours.The effects of exosomes on hepatic stellate cell proliferation,activation,autophagy,and expression of fibrosis markers were detected by western blot assay,RT-qPCR,and immunofluorescence staining.RT-qPCR and western blot assay were used to detect the effect of exosomes on the mRNA and protein expression of miR-15a-5p and the downstream signaling pathway Bcl-2,Beclin-1,and Rubicon in hepatic stellate cells.RESULTS AND CONCLUSION:(1)Compared with the control group,the ratio of autophagy markers LC3-II expression decreased,the number of autophagosome was also significantly decreased,and the intracellular lipid droplets were regenerated,simultaneously,cell volume diminished with the weakening of proliferation in hepatic stellate cells of the exosome group,indicated that the hepatic stellate cell activation was significantly inhibited.(2)Compared with the control group,the expressions ofα-smooth actin and type I collagen were significantly decreased(P<0.01),and the expression of miR-15a-5p was significantly increased in hepatic stellate cells of the exosome group(P<0.01).At the same time,the expression of its downstream target gene Bcl-2 was significantly decreased(P<0.01),while the expressions of autophagy genes Beclin-1 and Rubicon were significantly increased in hepatic stellate cells of the exosome group(P<0.01).The results indicate that adipose tissue-derived mesenchymal stem cell-derived exosomes inhibits the expression of Bcl-2 in hepatic stellate cells by targeting miR-15a-5p and increases the expression of downstream autophagy genes Beclin-1 and Rubicon,thereby inhibiting the autophagy of hepatic stellate cells.