[Altered expression of Ank protein in vertebral end plate]

To observe the expression change of ANK protein in normal and degenerative vertebral endplate chondrocytes and explore the correlation between ANK gene expression and intervertebral disc degeneration.

Cartilaginous endplates of 45 patients were divided into experiment group (28 with cervical spondylotic myelopathy including 17 males and 11 females) and control group (17 with fracture or dislocation of cervical spine including 10 males and 7 females). The MRI examinations revealed that all the endplate in control group were grade 0 and grade I-III in experiment group according to Miller's classification. Pathological examination demonstrated that intervertebral discs were grade I in control group and grade III-V in experiment group according to Thompson's classification. The morphological appearances and calcification of cartilaginous endplates were observed by HE and Von kossa staining. Immunohistochemical SABC staining, RT-PCR and Western blot were used to detect the ANK mRNA and protein expression in chondrocytes.

More calcium deposit could be observed in the experiment group than in the control group by Von kossa staining. ANKH protein was found positive in cell membrane of chondrocytes. Compared with chondrocytes of control group, the expression of ANK mRNA in experiment group markedly decreased (P < 0.05). And the level of ANK protein expression decreased too (P < 0.05).

Following the degeneration of cartilaginous endplate, the intervertebral disc degeneration worsened and the expression level of ANK decreased in vertebral endplate chondrocytes. Also calcification is positively correlated with the degree of intervertebral disc degeneration. Modulating the expression of ANK in endplate chondrocytes may be a new approach to treat the degeneration of intervertebral disc.