title: Proteoglycan aggregate formation by articular chondrocytes. Decrease in link-protein synthesis during culture.
abstract: The synthesis of link-stabilized proteoglycan aggregates by rabbit articular chondrocytes was investigated by [35S]sulphate labelling of primary monolayer cultures maintained for up to 21 days. (1) At all culture times the cells secreted a high-molecular-weight cartilage-type proteoglycan monomer of which 75%-80% formed aggregates with hyaluronic acid. (2) At 2 days of culture all of the aggregates were in link-stabilized form, but by 21 days only 5% were link-stabilized, as shown by displacement of monomers from the aggregate by hyaluronic acid oligosaccharides. (3) The addition of purified link protein to 21-day culture medium increased the proportion of link-stable aggregate from 5% to 70%. (4) Analysis of [3H]serine-labelled proteoglycan aggregates in the medium showed a marked decrease with culture time in the ratio of 3H-labelled link protein to 3H-labelled core protein present. The results suggest that the secretion of proteoglycan monomers and link protein by articular chondrocytes changes independently during prolonged monolayer culture.
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D002846:Chromatography, Affinity; D016326:Extracellular Matrix Proteins; D006025:Glycosaminoglycans / Q000302:isolation & purification; D046911:Macromolecular Substances; D014176:Protein Biosynthesis; D011509:Proteoglycans / Q000378:metabolism*; D011817:Rabbits; D000099249:Proteoglycan Link Protein
chemical_list: D016326:Extracellular Matrix Proteins; D006025:Glycosaminoglycans; D046911:Macromolecular Substances; D011509:Proteoglycans; D000099249:Proteoglycan Link Protein