Sulfation of chondroitin sulfate in human articular cartilage - The effectof age, topographical position, and zone of cartilage on tissue composition

The chondroitin ABC lyase digestion products of normal human femoral condyl e articular cartilage and of purified aggrecan were analyzed for their mono - and nonsulfated disaccharide composition, Changes in the total tissue che mistry were most pronounced during the period from birth to 20 years of age , when the -[GlcA beta,3GalNAc6]- disaccharide content increased from appro ximately 50% to 85% of the total disaccharide content and there was a conco mitant decrease in the content of the 4-sulfated disaccharide, In general, the disaccharide content of the deeper layers of immature cartilage were ri cher in the 4-sulfated residue than the upper regions of the tissue. As the tissue aged and decreased in thickness, the disaccharide composition becam e more evenly 6-sulfated. The newly synthesized chondroitin sulfate chains had a similar composition to the endogenous chains and also underwent the s ame age and zonal changes, The monoclonal antisera 3B3(+) and 2B6(+) were u sed to immunolocalize the unsaturated 6- and 4-sulfated residues generated at the reducing termini of the chondroitin sulfate chains by digestion with chondroitin ABC lyase, and these analyses indicated that the sulfation pat tern at this position did not necessarily reflect the internal disaccharide composition of the chains. In summary, the sulfation pattern of chondroiti n sulfate disaccharides from human normal articular cartilage varies with t he age of the specimen, the position (topography) on the joint surface, and the zone of cartilage analyzed, Furthermore, these changes in composition are a consequence of both extracellular, post-translational processing of t he core protein of aggrecan and changes in the sulfotransferase activity of the chondrocyte.