Differential expression of matrix metalloproteinase-3 in normal and degenerated human intervertebral disc

Detailed description of MMP-3 production in the human intervertebral disc degeneration has not been reported. We have previously demonstrated the production of MMP-3 by the rabbit annulus fibrosus cells in culture. The aim of this study was to determine the differences in the levels of MMP-3 between normal and degenerated human intervertebral discs. Six normal lumbar intervertebral discs from autopsy and degenerated specimens from 15 patients undergoing disc surgery were obtained. These were cultured and incubated with or without interleukin-1β (IL-1β) for 48 hours, and the media were assayed for immunological MMP-3 protein and caseinase activity. Immunohistochemistry was conducted to detect staining cells with MMP-3 and the ratio of positive cells was analyzed. The cultured media from degenerative disc tissues showed increased levels of MMP-3 compared to those of normal discs. Similarly, the levels of caseinase activity were significantly higher in degenerated discs. IL-1β produced a potent enhancement of MMP-3 synthesis, but, in the control group, no significant increase of MMP-3 synthesis was found. Immunohistochemical studies showed that MMP-3 was localized both in normal (4 of 6 specimens, 67%) and degenerated (14 of 15 specimens, 93%) disc tissues. The rate of positive cells in degenerated discs was significantly higher than that of the control discs.