JNK phosphorylation promotes degeneration of cervical endplate chondrocytes through down-regulation of the expression of ANK in humans.

BACKGROUND: C-Jun N-terminal kinase (JNK) signaling pathway and ankylosis gene (ANK) play a critical role in endplate chondrocytes degeneration. The purpose of this study was to investigate whether the expression levels of ANK was associated with the activation of JNK. METHODS: Cartilage endplates of 49 patients were divided into the control group (n = 19) and the experimental group (n = 30). The patients in the control group were graded 0 and those in the experimental group were graded I-III according to Miller's classification. Endplate chondrocytes were isolated by enzyme digestion and cultured in vitro. The inverted phase contrast microscope, teluidine blue staining, HE staining, real time RT-PCR, and MTT were used to observe morphological appearances, biological characteristics, and growth curve of endplate chondrocytes from the cartilage endplate of the two groups. Real time RT-PCR and Western blotting were used to analyze the mRNA and protein expression levels of associated factors in the degeneration process in the cultured endplate chondrocytes with or without subjected SP600125. RESULTS: The expression levels of type II collagen, aggrecan, and ANK in endplate chondrocytes of experimental group were lower than that of control group and phosphorylation level of JNK in the experimental group which was higher than that in the control group. Application of JNK phosphorylation inhibitor to degeneration chondrocytes resulted in a marked decrease in the phosphorylation level of JNK and a significant increase in the expression levels of type II collagen, aggrecan, and ANK. CONCLUSION: The degeneration of the human cervical endplate chondrocytes might be promoted by JNK phosphorylation by down-regulating the expression of ANK.

[Significance and expression of Sirt1 gene in human cervical endplate chondrocyte in vitro degeneration].

OBJECTIVE: To observe the expression changes of Sirt1 gene and examine the role and significance of degenerative process in human cervical endplate chondrocytes through a degeneration model of human cervical vertebral endplate chondrocyte. METHODS: Cartilage endplates of 30 patients were divided into control group (n = 16) with cervical vertebral fracture or dislocation and cervical spondylosis group (n = 14) with cervical spondylotic myelopathy. Endplate chondrocytes were isolated by enzyme digestion and cultured in vitro for 10 days. The differences of endplate chondrocytes from normal and degenerative cartilage endplates were observed by inverted phase-contrast microscope, hematoxylin and eosin staining and toluidine blue staining. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to detect the mRNA expressions of Sirt1, collagen II and aggrecan. RESULTS: Compared with the normal group, the cellular morphology of degenerative group showed spindle-shaped changes. The mRNA expression of Sirt1 (P = 0.034) significantly decreased. Aggrecan (P = 0.0063) and collagen II (P = 0.0072) decreased also markedly. CONCLUSION: Sirt1 gene expression is significantly down-regulated in degenerative human cervical endplate chondrocytes. Regulating the expression of Sirt1 gene may block or delay the occurrence of human cervical endplate cartilage degeneration.

[Establishment and significance of an in vitro model of degeneration of human cervical endplate chondrocytes].

OBJECTIVE: To establish an in vitro model of degeneration of human cervical endplate chondrocytes and observe the morphology and phenotypes of endplate chondrocytes in normal and degenerative cervical vertebral endplates. METHODS: Cartilage endplates of 49 patients were divided into control group (n = 19) with cervical vertebral fracture or dislocation and experiment group (n = 30) with cervical spondylotic myelopathy. Endplate chondrocytes were isolated by enzyme digestion and cultured in vitro. The morphological appearances, growth curve and biological characteristics of endplate chondrocytes from normal and degenerative cartilage endplate were observed by inverted phase contrast microscope, HE staining, MTT, toluidine blue staining and reverse transcription-polymerase chain reaction (RT-PCR) respectively. RT-PCR was used to detect the mRNA expression of aggrecan, type II collagen and type I collagen. RESULTS: The endplate chondrocytes expressed aggrecan, type II collagen and type I collagen. The phenotypes and biological characteristics were similar to those of articular chondrocytes. The morphological appearance of primary endplate chondrocytes in the control group were mostly polygons, nucleus with round or ellipse, sometimes nuclei, vacuoles in intra cytoplasm, expressing a high proliferating rate. The cells of the experiment group were fusiform and their proliferating rates decreased. Compared with the control group, the mRNA expression of aggrecan (0.695 ± 0.052 vs 0.950 ± 0.032, t = 7.263, P = 0.002) and type II collagen (0.726 ± 0.035, 0.907 ± 0.078, t = 3.681, P = 0.021) markedly decreased. And the mRNA expression of type I collagen (0.795 ± 0.028 vs 0.552 ± 0.070, t = -5.560, P = 0.005) increased in the experiment group. CONCLUSION: A degenerative cell model of human cervical endplate chondrocytes has been established successfully in vitro. It may offer the cytological rationales for exploring the mechanism of intervertebral disc degeneration. And the previous restrictions of studying only the model of animal cells shall be resolved.