DIFFERENTIAL EXPRESSION OF MEMBRANE-ANCHORED PROTEOGLYCANS IN RABBIT ARTICULAR CHONDROCYTES CULTURED IN MONOLAYERS AND IN ALGINATE BEADS - EFFECT OF TRANSFORMING GROWTH-FACTOR-BETA-1

Cell-surface proteoglycans (PGs) were extracted with Triton X-100 from rabbit articular chondrocytes cultured in monolayers and in alginate beads. They were first purified on DEAE-Trisacryl columns and the prop ortion of hydrophobic PGs was determined by both Octyl-Sepharose chrom atography and partitioning in Triton X-114. These two methods revealed that the proportion of hydrophobic PGs was higher in monolayer cultur e system as compared to alginate beads (24 and 15%, respectively). Cha racterization of the PGs by Sepharose CL 6B gel filtration followed by electrophoresis indicated that the PGs isolated from monolayers were composed of three chondroitin sulfate (CS) PGs (core proteins of 180, 100 and 50 kDa) and a heparan sulfate (HS) PG (core protein of 60 kDa) . In the alginate system, CSPGs with core proteins of 180, 45 and 32 k Da were observed, but no HSPG was present. In parallel, the effect of TGF-beta on the distribution of membrane-associated PGs was studied. T he results showed that the synthesis of cell-surface PGs was stimulate d by TGF-beta in monolayers whereas it was inhibited in alginate beads , but the amount of hydrophobic PGs was not altered by the growth fact or. These data clearly indicate that TGF-beta induces a differential e xpression of the PG families present at the cell surface, Taken togeth er, the results reveal the complex regulation oi cell-surface PG distr ibution, which obviously depends on the culture method used and sugges t that rabbit articular chondrocytes may differentially respond to ext racellular ligands according to their morphological state and environm ent.