[Studies on normal and pathological human cartilage proteoglycans with metrizamide density gradient...

In order to study human articular cartilage proteoglycans (PG) in aging and pathological states, PG extracts of normal cartilage, osteoarthritic cartilage, chondrosarcoma and osteochondroma were subjected to the density gradient ultracentrifugation in 23% metrizamide-6M urea system. Normal cartilages have chondroitin sulfate rich PG and keratan sulfate rich PG. The latter has a higher buoyant density and increases markedly with aging, but is missing in all of the pathological cartilages tested which have juvenile profiles corresponding to the normal cartilage of a child under 10 years of age. No differences in the chain lengths of glycosaminoglycans were observed in any of the cartilages tested, but marked differences were observed in the aggregation PG and hyaluronate in the pathological cartilages. The molecular sizes of hyaluronate are probably small in normal adults but large in the pathological state. Determinations of hexose and uronate distribution in the density gradient characterize easily the differences in aging and pathological cartilages. This system provided more information than the CsCl-guanidine HCl system.