Biochemical changes in intervertebral disc 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 centre of the disc. Proteoglycans of the nucleus pulposus and annulus fibrosus of normal and degenerate intervertebral discs were examined. In comparison with monomers of normal tissues, 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 HS-Sepharose 2B affinity column. A greater proportion of the keratan sulphate-protein cores from degenerate disc were capable of interaction with the immobilized hyaluronate. Loss of aggregating ability was associated with diminution in size of the core. It is suggested that a large proportion of proteoglycans from normal disc have undergone a degree of degradation in the hyaluronate binding region and that proteoglycan synthesis in this tissue is slower than in degenerate tissue.