THE PROTEOGLYCANS OF THE CARTILAGINOUS END-PLATE OF THE HUMAN INTERVERTEBRAL DISC CHANGE AFTER MATURITY

Lumbar spines collected postmortem were assigned to one of two groups: group 1-three spines with healthy discs, or group 2-three spines with severely degenerated discs. The proteoglycans (PGs) of the cartilagin ous endplate (CEP) were extracted with 4 M guanidinium chloride contai ning protease inhibitors and were purified by caesium chloride density gradient ultracentrifugation. On Sepharose CL-2B chromatography, the most dense 20% of the gradient (the Al fraction) showed two subfractio ns, one eluting near the void volume and one partitioned by the gel. B oth fractions resembled those of the nucleus pulposus and the anulus f ibrosus in the number of components seen on agarose-polyacrylamide gel electrophoresis. Both fractions changed with ageing/degeneration; the ratio of keratan sulphate to chondroitin sulphate, which was about 1 in group 1, increased to about 3 in group 2; the hydrodynamic volumes fell; the electrophoretically distinguishable component of lowest mobi lity disappeared while new, highly mobile components appeared; and the water content decreased slightly. Clearly, the PGs of the CEP of dege nerated intervertebral discs differed from those of healthy discs; thi s supports the view that the CEP participates in the process of ageing /degeneration in the disc.