SPECIFICITY AND SYNERGISM OF POLYPEPTIDE GROWTH-FACTORS IN STIMULATING THE SYNTHESIS OF PROTEOGLYCANS AND A NOVEL HIGH-MOLECULAR-WEIGHT ANIONIC GLYCOPROTEIN BY ARTICULAR CHONDROCYTE CULTURES

Objective, To determine the specificity of and possible synergism amon g polypeptide growth factors (PGF) on the net synthesis of proteoglyca n and a novel high molecular weight anionic glycoprotein (HMW AG), of roughly 540 kDa, by articular chondrocyte cultures. Methods. Confluent articular chondrocyte cultures were labeled with either [S-35]SO4 or [H-3]glucosamine and [S-35]SO4 and stimulated by adding the individual PGF or combinations of the PGF. Alcian blue dye precipitation was use d for direct rapid quantification of newly synthesized proteoglycans f rom the media of the S-35 labeled cultures. To assess the effects of t he PGF on the synthesis of the HMW AGI a toluidine blue dye batch prec ipitation method was used for isolation of anionic glycoconjugates fro m the media of the H-3 and S-35 labeled articular chondrocyte cultures , followed by chondroitinase ABC digestion and gradient sodium dodecyl sulfate polyacrylamide gel electrophoresis. Results, Optimal concentr ations of transforming growth factor-beta 1 (TGF-beta), insulin-like g rowth factor-1 (IGF), and platelet derived growth factor (PDGF) stimul ated net proteoglycan synthesis per cell by 178, 106, and 101%, respec tively. In combinations, TGF-beta + PDGF, TGF-beta + IGF and PDGF + IG F gave stimulations of proteoglycan synthesis of 418, 384, and 217%, r espectively, HMW AG net synthesis was induced by all 3 PGF but the deg ree of induction was much greater with TGF-beta. Conclusion, Net prote oglycan synthesis by articular chondrocyte cultures is synergistically stimulated by the addition of optimal concentrations of combinations of TGF-beta + PDGF and TGF-beta + IGF, but not PDGF + IGE Net HMW AG s ynthesis is preferentially stimulated by TGF-beta.