Age changes in Alcian blue staining of glycosaminoglycans in sheep articular cartilage

Alcian blue staining of glycosaminoglycans in sheep articular cartilage is described and discussed. Chodrocytes contain mainly low molecular weight chondroitin sulphate in the outer layers but keratan sulphate increases with depth. Protein-polysaccharide interaction increases with age but the cellular staining decreases in intensity with age. Lacunar capsules contain material of higher molecular weight, much of which is chondroitin sulphate, but no protein-polysaccharide interaction occurs. The matrix of the outer layers is deeply stained while that of the inner layer is pale and consists mainly of keratan sulphate. When stained in high salt concentrations (greater than 0-7 M) the matrix of the middle layer shows two zones; hyaluronidase treatment allows these zones to be differentiated at lower salt concentrations.