Complexity of proteoglycan organization in articular cartilage: recent observations

Antibodies to aggregating high buoyant density cartilage proteoglycans (PG) and to link proteins have been used to study the distribution of these molecules in adult bovine and human articular cartilages. The work on bovine cartilages has been described in detail elsewhere. In human articular cartilage there was a striking deficiency of PG in the interterritorial region of the deep zone and of link protein in territorial sites in this and the mid zone. Thus aggregated PG stabilized in their interaction with link protein, are probably mainly present in the interterritorial matrix of the mid zones of human cartilage and in the deep zone of bovine cartilage. This apparent deficiency of PG in the interterritorial matrix of the deep zone in adult human cartilage may produce greater weaknesses in this older cartilage.