Molecular biology of degenerative disc disease.

The intervertebral disc is a complex anatomic and biochemical structure. It is composed primarily of fibrocytes and chondrocytes that are anatomically segregated in an elaborate avascular macromolecular matrix of collagen and proteoglycans. Degenerative processes associated with aging and trauma result in morphological and molecular changes to the disc. Morphological changes are observed as dehydration, fissuring, and tearing of the nucleus, annulus and endplates. On the molecular level, degenerative changes include decreased diffusion, decreased cell viability, decreased proteoglycan synthesis, and alteration in collagen distribution. The role of inflammatory mediators in these processes, and the potential use of growth factors to delay or reverse the degenerative cascade, is poorly understood. However, these areas are under active investigation, the results of which may soon contribute significantly to our understanding of degenerative disc disease.