RÉSUMÉ
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 5 μL of CCCP(10 μmol/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 type Ⅱ collagen(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.