Observations on the acid glycosaminoglycan (mucopolysaccharide) content of the matrix of aging cartilage.

Abstract

The use of Alcian-blue at a pH near neutrality and incorporating different concentrations of MgCl2 in the staining medium, provides a method for the differentiation of the glycosaminoglycans. Both chondroitin sulfate and keratosulfate are stained in cartilage, using a salt concentration of 0.4[image]; but only high molecular weight keratosulfate is detected using a concentration of 0.9[image] MgCl2. Keratosulfate was localized in the matrix of costal and articular cartilage from 10 human subjects aged 1 1/2 - 78 years. There is a negligible staining reaction for keratosulfate in infant cartilage. Keratosulfate is localized in the interterritorial matrix from the second decade onwards. There is an intense staining reaction for keratosulfate in the territorial matrix, and only a weak reaction inter-territorially in the central region of mature costal cartilage. A similar territorial predominance is seen in the deeper parts of articular cartilage next to the calcified layer from about the beginning of the fourth decade. The territorial distribution of this substance in the deepest parts of both types of cartilage may be related to the efficiency of nutrition of the cells in these areas as much as to their age. The effect of these age changes on the physical properties of the tissue as a whole are discussed in the light of the principle of "excluded volume".