Immunolocation analysis of glycosaminoglycans in the human growth plate

Monoclonal antibodies were used in this study to immunolocate glycosaminoglycans throughout the human growth plate. Chondroitin-4-sulfate, chondroitin-6-sulfate, and keratan sulfate were observed in the extracellular matrix of all zones of the growth plate and persisted into the cartilage trabeculae of newly formed metaphyseal bone. Also present in the extracellular matrix was an oversulfated chondroitin/dermatan sulfate glycosaminoglycan which appeared to be specific to the proliferative and hypertrophic zones of the growth plate. As with the other extracellular matrix molecules, this epitope persisted into the cartilage trabeculae of the metaphyseal bone. Zonal differences between the extracellular and pericellular or lacunae matrix were also observed. The hypertrophic chondrocytes appeared to synthesize chondroitin sulfate chains containing a non-reducing terminal 6-sulfated disaccharide, which were located in areas immediately adjacent to the cells. This epitope was not found to any significant extent in the other zones. The pericellular region around hypertrophic chondrocytes also contained a keratan sulfate epitope which was also observed in the resting zone but not in the proliferative zone. These cell-associated glycosaminoglycans were not found in the cartilage trabeculae of metaphyseal bone, indicating their removal as the terminal hypertrophic chondrocytes and their lacunae are removed by invading blood vessels. These changes in matrix glycosaminoglycan content, both in the different zones and within zones, indicate constant subtle alterations in chondrocyte metabolic products as they proceed through their life cycle of proliferation, maturation, and hypertrophy.