Immunohistochemical assesment of matrix metalloproteinase expression in cervical degenerative disc disease

Degenerative disc disease, even though underlying mechanisms are not fully understood, is associated with the vascular, biochemical and anatomical changes of the intervertebral disc. The integrity and the structure of the extracellular matrix provides the functional properties of the intervertebral disc. During the degeneration process, production of normal matrix decreases as the degradation of the matrix increases. Matrix degrading enzymes such as matrix metalloproteinases (MMPs) are assumed to play a pivotal role in intervertebral disc degradation. In this study, 20 herniated cervical discs obtained from 20 patients and 34 cervical discs obtained from 17 fresh cadavers as a control group were used to show the expression of MMP-1, 3, 9 and TIMP-1 by using immunohistochemistry. The number of immunopositive cells were assessed by morphometric analyses. Thompson grade 3,4,5 patients were included as the degenerative disc group. Specimens were also scored for the degeneration according to the formation of clefts and tears, cellular proliferation, granular matrix changes and mucous degeneration. The patient group discs were statistically more degenerative than the control group. Also a significant close relation was found between Thompson grade and the histologic degeneration scores. In the patient group, MMP-1, 9 and TIMP-1 levels were significantly higher than the control group. There was no difference in MMP-3 levels between the groups. For the first time Thompson grading system was applied in the cervical region and a significant correlation between the histological degeneration and Thompson grading was shown. According to this result we think that Thompson Scoring system can be used for the cervical region as well. Our data suggests that major MMPs play an important role in degradation of the intervertebral disc (IVD). This is evidenced by the statistically high levels of MMPs in the degeneration group than the control group.These kinds of studies highlight specific matrix metalloproteinases that might be most efficient to target in developing therapeutics for minimizing the degradation of the extracellular matrix of the intervertebral disc.