Expression of the differentiated phenotype of chondrocytes in newly synthesized acetabulum

Human cartilaginous cells produce two types of proteoglycan monomers (PGI and PGII) distinguishable by their molecular size in density gradient centrifugation under dissociative conditions. In order to determine whether connective tissues on the sliding surface of the acetabulum on an endoprosthesis are able to differentiate into cartilaginous tissue, we made histological and biochemical analysis of the incorporation of 35S and the distribution of the molecular size of proteoglycans produced. Histologically, dense collagen fibers were observed both on weight-bearing and non-weight-bearing surfaces, but there was little evidence of cartilaginous metaplasia. Biochemical analysis, however, demonstrated that incorporation of 35S in newly synthesized glycosaminoglycan (GAG) was higher than that in non-cartilaginous tissues, suggesting that cartilaginous differentiation of mesenchymal tissues had occurred.