IDENTIFICATION OF HUMAN INTERVERTEBRAL-DISK STROMELYSIN AND ITS INVOLVEMENT IN MATRIX DEGRADATION

Human intervertebral disc when maintained in organ culture released a latent casein-degrading metalloproteinase into the medium in a manner analogous to cultures of human cartilage. This enzyme was demonstrated to be immunologically identical to prostromelysin. It was also found that the amount of procollagenase secreted by both cartilage and disc cells was considerably less than that of prostromelysin. Tissue extraction confirmed that the low level of procollagenase observed was not due to retention of the enzyme within the tissue. Human intervertebral disc link proteins were found to possess the same N-terminal as those of their counterparts in human articular cartilage, where it appears that stromelysin is responsible for generating molecular heterogeneity. These results suggest that intervertebral disc cells are capable of secreting prostromelysin, which can become activated within the extracellular matrix and hence contribute to the age-related and degenerative changes in the disc.