Neutral proteinases in human intervertebral disc. Role in degeneration and probable origin.

Neutral proteinases were partially purified from human intervertebral disc by extraction with guanidine hydrochloride followed by Sephadex G-75 column chromatography. They showed gelatinolytic and elastolytic activities at neutral pH. The apparent molecular weights of these enzymes were 70 KD and 25 KD, the former being the complexed form of the latter. The sensitivity to various synthetic inhibitors indicated these enzymes to be serine elastases. Furthermore, they were considered to be leukocyte elastases because anti-leukocyte elastase antibody inhibited the proteinase activity of these enzymes. Proteinase activity was not detected in normal discs, except for some slight activity in the end-plate. In contrast, the degenerated discs showed high activity, especially in the nucleus pulposus and end-plate. Similar high levels of proteinase activity were found in the vertebral body adjacent to normal as well as degenerated discs. These findings suggest that leukocyte elastase, which is normally present in the vertebral body, flows into and degrades the matrix of the intervertebral disc under pathologic conditions.