Glycoconjugate J (1986) 3:287-298 Effect of In Vitro Differentiation on Proteoglycan Structure in Cultured Human Monocytes SVEIN O KOLSET 1'2. and LENA KJELLI~N 1 1Department of Medical and Physiological Chemistry, Swedish University of Agricultural Sciences, The Biomedical Center, S-75123 Uppsala, Sweden 2Department of Tumor Biology, Norwegian Cancer Society, University of Tromso, N-9001 Tromso,Norway ReceivedApril 2, 1986. Key words: monocyte in vitro differentiation, chondroitin sulfate proteoglycan, fibronectin-chondroitin sulfate interaction Parellel to in vitro differentiation of human monocytes into macrophage-like cells, the cells change their synthesis of glycosaminoglycans from chondroitin 4-sulfate to highly sulfated chondroitin sulfate, containing 4,6-disulfated N-acetylgalactosamine units IKolset etal. (1983) Biochem J210:661-671. After exposure of monocyte cultures to [35S]sulfatefor 24 h either from the onset of cultivation, prior to differentiation, or from day 4, after differentiation, 35S-macromolecules from medium and cell-layer were isolated and characterized. The cell-layer of day 5 cultures contained both pro- teoglycans and free polysaccharide chains, while the 35S-macromolecules present in the cell-layer of day I cultures and in medium of both monocytes and macrophage-like cells were almost exclusively of proteoglycan nature. Proteoglycans produced by macrophage-like cells were of larger size than the monocyte proteoglycans, most like- ly due to an increased polysaccharide chain length. These proteoglycans, in contrast to the monocyte-derived species, also showed affinity for fibronectin at physiological ionic strength. Chondroitin sulfate proteoglycans present in cartilage have been extensively studied (see ref. 1 for review). The large proteoglycans form, together with hyalu ronic acid and link proteins, aggregates which are important for the mechanical properties of car- tilage. Chondroitin sulfate proteoglycans with structural features different from the large, aggregating species have also been identified in cartilage; among them a small proteoglycan (Mr -76 000) [2]. Similar proteoglycans carrying chondroitin sulfate or dermatan sulfate have been isolated from aorta, bone, cornea, sclera and tendon [31. Recently, the complete amino acid sequence of a small chondroitin sulfate pro- teoglycan has been deduced from the nucleotide sequence of the core protein cDNA [4]. The core protein contains a large region composed of alternating serine and glycine residues, relating this proteoglycan to the mast cell heparin proteoglycan Isl. Many dif- ferent cell types synthesize large chondroitin sulfate or dermatan sulfate proteoglycans *Author for correspondence 287