Intervertebral disk degeneration and herniation: the role of metalloproteinases and cytokines.

This article reviews the role of metabolic factors, including metalloproteinases and cytokines, in the occurrence of degenerative disk disease and disk herniation. Given that mechanical factors alone cannot cause disk degeneration, studies must explore metabolic, genetic, nutritional, and age-related factors. Zinc metalloproteinases exert particularly important effects, not only directly, but also indirectly through promotion of neovascularization. The production of these enzymes is dependent on a number of cytokines and on the cell changes they induce. This complex effect acts both on disk matrix degeneration and on the pain generated by contact between the protruding disk and the nerve roots. However, it can have a favorable effect by promoting resorption of the herniated disk. Available data on the role for mechanical factors on the disk chondrocyte metabolism and on metalloproteinase production show that mechanical and metabolic factors interact closely to produce disk disorders.