Age changes in the localization and distribution of glycosaminoglycans in human hyaline cartilage.

Abstract

The localization and distribution of acid glycosaminoglycans, glycoproteins and basic proteins have been studied in human costal cartilage, trachea and primary bronchi from the fetal period through old age. Alcian blue and PAS were used for the staining of acid glycosaminoglycans and glycoprotein and/or sugar-containing compounds respectively. Bromphenol blue and/or bromsulfalein were utilized for the detection of basic proteins. In a further attempt to histochemically identify the various polyanions staining was carried out with AB containing different concentrations of electrolytes. Mild acid hydrolysis, hyaluronidase and proteolytic digestions were also employed. It appeared that the distribution, localization and concentration of the different macromolecules vary according to age, to the type of hyaline cartilage and to the different areas of the same segment. The results also suggested that in developing tissues the areas of appositional growth synthesize mainly chondroitinsulphate while in the territory and interterritory this acidic polyanion is found with keratansulphate. With advancing age the latter slowly disappears from the interterritorial matrix and is nearly exclusively found in the matrix adjacent to the chondrocytes. The susceptibility of these tissues to enzyme digestion also varied according to age and to the type of hyaline cartilage. Proteolytic and hyaluronidase treatment, which were extremely effective in the prenatal period and in young subjects, had practically no effect on mature and old ribs. In the bronchi, instead, the substrates were easily extracted even at an old age. The problems related to the different chemical state of the various macromolecules, their localization and distribution and their possible effect on “senescence” of hyaline cartilage are discussed.