Proteoglycan Metabolism Is Age Related and Modulated by Isoforms of Platelet-Derived Growth Factor in Bovine Articular Cartilage Explant Cultures

The influence of recombinant human platelet-derived growth factor (PDGF) on proteoglycan metabolism was examined in bovine articular cartilage explants under serum-free conditions. All three isoforms of PDGF (AB, AA. and BB) dose-dependently increased proteoglycan biosynthesis and decreased the rate of proteoglycan catabolism in cartilage explants obtained from young (1-6 weeks), adolescent (2-6 months), and adult animals (2-3 years). The biosynthetic stimulative effect of PDGFAA was significantly lower than that of PDGF-AB only in adult tissues. The decrease in catabolic rate was more pronounced in younger animals. For culture periods of up to 12 days, the three PDGF isoforms did not have an effect on DNA synthesis. The molecular size of both the proteoglycan monomers and the glycosaminoglycan chains and the chondroitinase ABC sensitive pool decreased with age of the animal, but were not altered by PDGF-AB treatment. These data show that the three recombinant human PDGF isoforms contributed to matrix homeostasis in the articular cartilage explant system, with no apparent mitogenic effect.