The role of matrix metalloproteinase 9 in intervertebral disc degeneration.

The present study investigates the histological alterations and expression of matrix metalloproteinase 9 (MMP-9) in disc specimens of 43 patients who underwent surgery for lumbar disc herniation. The immunostaining for MMP-9 was evaluated semi-quantitatively. Histologic degeneration was scored between 0 and 12 depending on the degree of chondrocyte proliferation and presence of tears and clefts, granular changes and mucous degeneration. Herniation was graded as grade 1 (protrusion), grade 2 (extrusion) or grade 3 (sequestration) on MRI. Although there was no significant statistical difference between the histologic degeneration score and age, degenerative changes were more pronounced in higher grade of herniation (p<0.0001). MMP-9 expression was related to histologic degenerative score in all age groups (p=0.0065). MMP-9 was also related to herniation grade in patients younger than 30 years of age (p=0.0037). No significant association was found between MMP-9 expression and herniation grade in patients who were 30-60 years or over 60 years of age.