Structure and composition of proteoglycans from human annulus fibrosus

Proteoglycans were extracted from ground human lumbar annuli fibrosi with 4M guanidinium chloride and purified by means of associative equilibrium density gradient centrifugation. The proteoglycan preparations contained chondroitin sulphate, keratan sulphate and hyaluronic acid, but no dermatan sulphate. Degradation experiments suggested that the proteoglycans contain three regions: a chondroitin sulphate-rich region, a keratan sulphate-rich region and a region that binds to hyaluronic acid, thus allowing proteoglycan aggregates to be formed. The keratan sulphate-rich region seemed to be more prominent than in bovine hyaline cartilage proteoglycans. The model for the structure of bovine hyaline cartilage proteoglycans, Hascall and Heinegård, seems to be applicable to the proteoglycans from human annulus fibrosus. The amino acid composition of annulus fibrosus proteoglycans is very similar to that of bovine hyaline cartilage proteoglycans.