The glycosaminoglycans of human articular cartilage: concentration and distribution in different layers in the adult individual.

The articular cartilage from morphologically normal femoral heads from 7 humans, aged 50-85 years, was sectioned parallel to the surface firstly at 40 micron thickness and then serially at 200 micron thickness to the cartilage-bone junction. Pooled sections from separate layers were used for analysis of the glycosaminoglycans by Cetylpyridinum chloride and ECTEOLA-cellulose microcolumns. The total concentration of glycosaminoglycans per dry weight tissue showed an increase with distance from the articular surface. The increase was shown to be due, principally, to keratan sulphate, while the levels of hyaluronic acid and chondroitin sulphate showed a proportional decrease with depth. The 40 micron thick superficial layer contained a considerably lower concentration of both keratan sulphate and chondroitin sulphate than the rest of the cartilage. These superficial layer glycosaminoglycans, and particularly chondroitin sulphate, showed a more polydisperse distribution according to molecular weight/charge density than the corresponding glycosaminoglycans of the more deeply situated layers. In view of findings on bovine articular cartilage of different age-classes reported previously, these features of the superficial layer appear to represent the normal biochemical structure.