Expression of SOX9 and COL2A1 gene in human cervical intervertebral disc nucleus pulpusus and its significance

Objective: To observe the expression of SRYCsex determining region Y)-box 9 (SOX9) and collagen type E alpha 1 (COL2A1) in human cervical intervertebral disc nucleus pulposus (NP) tissues of various degeneration degrees, so as to discuss the role of their expression during cervical intervertebral disc degeneration(CIDD). Methods: Totally 36 human cervical intervertebral disc specimens and their pre-operation MRI findings were obtained from surgical patients or patients with cervical trauma, and they were classified into five grades according to the Miyazaki grading system. The expression of SOX9 and COL2A1 was examined by fluorescence quantitative RT-PCR, Western blotting analysis and immunohistochemistry staining. The relationship between SOX9, COL2A1 expression and the degrees of CIDD was analyzed, and the relationship between SOX9 and COL2A1 was also discussed. Results: Both SOX9 and COL2A1 were expressed in NP tissues, with SOX9 seen in the nucleus and COL2A1 in the extracellular matrix. The expression of SOX9 and COL2A1 mRNA and protein gradually decreased as Miyazaki I progressed to Miyazaki V. We also found a linear relationship between COL2A1 (Y) and SOX9 (X) expression: Y=0. 923X-0. 059 (P<0. 001). Conclusion: The expression of SOX9 and COL2A1 mRNA decrease with the increase of CIDD severity, with SOX9 and COL2A1 mRNA having a similar decreasing tendency. SOX9 positively regulate COL2A1 expression, indicating that changes of SOX9 and COL2A1 gene might be one of the molecular mechanisms of CIDD.