PINK1/Parkin介导的线粒体自噬在力学失衡诱导终板软骨退变中的作用

The role of PINK1/Parkin-mediated mitophagy in mechanical imbalance-induced endplate cartilage degeneration

目的 检测脊柱失稳诱导终板软骨退变模型大鼠中线粒体自噬水平的变化,探讨PINK1/Parkin介导的线粒体自噬在终板软骨以及椎间盘退变中的作用。方法 通过手术切除大鼠L2~L5棘上、棘间韧带,咬除L2~L5两侧关节突,构建大鼠脊柱失稳模型。18只SD大鼠分为正常组、退变组及羰基氰化物3-氯苯腙(CCCP)组,每组6只。正常组大鼠无特殊处理,退变组大鼠构建大鼠脊柱失稳模型,CCCP组大鼠在构建大鼠脊柱失稳模型后于椎间盘注射5μL CCCP (10μmol/L)。利用HE染色观察终板软骨及椎间盘形态变化,番红-固绿染色观察终板软骨细胞外基质变化。RT-PCR检测各组大鼠终板软骨组织中Ⅱ型胶原(COL-2A)、蛋白聚糖(ACAN)、PINK1、Parkin mRNA表达水平;Western blot检测COL-2A、ACAN、PINK1、Parkin及线粒体膜蛋白Tomm20、Timm23蛋白表达水平变化。结果 与正常组比较,退变组大鼠椎间盘髓核破坏明显,终板软骨细胞外基质分泌减少;CCCP组大鼠椎间盘结构较完整,终板软骨细胞外基质分泌较退变组明显增多。与正常组比较,退变组大鼠终板软骨组织COL-2A、ACAN表达均明显下调(P<0.05),线粒体自噬相关基因PINK1和Parkin表达显著降低(P<0.05),线粒体膜蛋白Tomm20及Timm23表达增高(P<0.05);CCCP组大鼠终板软骨组织COL-2A、ACAN、PINKI及Parkin表达较退变组均明显上调(P<0.05),Tomm20及Timm23蛋白水平较退变组明显下调(P<0.05)。结论 大鼠脊柱失稳导致终板软骨PINK1/Parkin信号通路介导的线粒体自噬水平降低,从而诱导终板软骨及椎间盘退变,激活线粒体自噬能够明显减轻终板软骨及椎间盘退变。

Objective To detect the changes of mitophagy level in rats with endplate cartilage degeneration induced by spinal instability,and explore the role of PINK1/Parkin-mediated mitophagy in endplate cartilage and intervertebral disc degeneration.Methods The rat spinal instability model was established by surgically removing the superspinal and interspinal ligaments of L2 to L5,and cleaning the bilateral articular processes of the L2 to L5.Eighteen SD rats were divided into the normal group,the degenerative group,and the carbonyl cyanide 3-chlorophenylhydrazone(CCCP)group,with 6 rats in each group.The rats in the normal group had no special treatment,the rats in the degenerative group constructed a rat spinal instability model,and the rats in the CCCP group were injected with 5μL of CCCP(10μmol/L)in the intervertebral disc after the construction of spinal instability model.The changes of histomorphology in the endplate cartilage and intervertebral disc were abserved by HE staining,and the change of extracellular matrix of endplate cartilage was observed by safranin O-fast green staining.RT-PCR detected the mRNA expression of typeⅡcollagen(COL-2A),aggrecan(ACAN),PINK1 and Parkin in each group.The changes of the protein expression levels of COL-2A,ACAN,PINK1,Parkin and mitochondrial membrane proteins of Tomm20 and Timm23 were detected by Western blot.Results Compared with the normal group,the intervertebral disc nucleus pulposus of rats in the degenerative group was significantly destroyed and the secretion of extracellular matrix of endplate chondrocytes decreased;while the structure of intervertebral discs for rats in the CCCP group was more intact,and the secretion of extracellular matrix of endplate chondrocytes was significantly increased compared with that in the degenerative group.Compared with the normal group,the expression of COL-2A and ACAN in endplate cartilage tissues of rats in the degenerative group were significantly down-regulated(P<0.05),the expression of mitochon-drial autophagy-related genes of PINK1 and Parkin were significantly decreased(P<0.05),and the expression of mitochondrial membrane proteins of Tomm20 and Timm23 were increased(P<0.05).Compared with the degenerative group,the expression of COL-2A,ACAN,PINKI and Parkin in the endplate cartilage tissue of rats in the CCCP group were significantly up-regulated(P<0.05),and the protein levels of Tomm20 and Timm23 were significantly down-regulated(P<0.05).Conclusion Rat spinal instability leads to a decrease level of mitophagy mediated by PINK1/Parkin signaling pathway in endplate cartilage,thereby inducing endplate cartilage and intervertebral disc degeneration,and the activation of mitophagy can significantly reduce endplate cartilage and intervertebral disc degeneration.