Molecular therapy of the intervertebral disc.

BACKGROUND CONTEXT

Currently, no biologic treatment is available for disc degeneration. However, many different molecules of potential therapeutic benefit are being investigated.

PURPOSE

Review and categorize the molecules under investigation for potential therapy in preventing or reversing disc degeneration.

STUDY DESIGN

Review article.

METHODS

Review of published articles on molecules that may be useful in biologic therapy of the intervertebral disc.

RESULTS

The list of molecules under investigation for potential benefit in biologic therapy of the intervertebral disc repair continues to grow. These molecules are so diverse that they no longer all fall into the classic terminology of "growth factor." Some of these molecules are not growth factors at all and some are not even cytokines. At least four different classes of molecules may be effective in disc repair. These include anticatabolics (eg, tissue inhibitors of metalloproteinase [TIMPs]), mitogens (eg, insulin-like growth factor-1 [IGF-1], platelet-derived growth factor [PDGF]), chondrogenic morphogens (transforming growth factor beta [TGF-beta] and bone morphogenetic proteins [BMPs]), and intracellular regulators (LIM mineralization protein-1 [LMP-1] and Sox9). Although some in vitro data are available on all of these molecules, few of these molecules have been tested in vivo with an animal model of disc degeneration.

CONCLUSIONS

As the current screening experiments are concluded, more definitive in vivo systems involving a more realistic degeneration model will be a necessary step before attempting human studies.