BIOCHEMICAL-CHANGES IN INTERVERTEBRAL-DISK DEGENERATION

The distribution of the principal matrix components, collagen, proteoglycans and water, across the diameter of human normal and degenerate intervertebral discs was compared. Little difference in collagen distribution was noted between normal and degenerate tissue, but water and proteoglycan content decreased with degeneration, particularly in the center of the disc. Proteoglycans of the nucleus pulposus and annulus fibrosus of normal and degenerate intervertebral discs were examined. Compared to monomers of normal tissue, degenerate disc proteoglycans were of larger average hydrodynamic size and had a higher glucosamine to galactosamine ratio. Proteoglycans were digested with chondroitinase ABC and passed over an HA[hyaluronate]-Sepharose 2B affinity column. A greater proportion of the keratan sulphate-protein cores from degenerate disc were capable of interaction with the immobolized hyaluronate. Loss of aggregating ability was associated with diminution in size of the core. Apparently, a large proportion of proteoglycans from normal disc undergo a degree of degradation in the hyaluronate binding region. Apparently, proteoglycan synthesis in this tissue in slower than in degenerate tissue.