Standardization of nutrient media for isolated human articular chondrocytes in gelified agarose suspension culture

Human articular cartilage cells were cultured in 1.5% agarose in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal calf serum or in serum-free DMEM with 0.15% bovine serum albumin. S-35-aggrecan synthesis in serum-free DMEM was between 20% and 30% of the value observed in DMEM supplemented with 10% fetal calf serum. The extent to which different growth or differentiation factors were able to restore S-35 incorporation in aggrecan in serum-free DMEM was determined: human serum transferrin had no effect on aggrecan synthesis levels; bovine pancreas insulin, insulin-like growth factor (IGF)-1 and IGF-8 restored S-35-aggrecan synthesis to 35-50% of the control levels. The effects were dose-dependent, to level off at 100 ng/ml for the three factors. No cumulative or synergistic activities were observed when these factors were combined. Transforming growth factor (TGF)beta, at concentrations ranging from 10-50 ng/ml stimulated aggrecan synthesis to approximately 50% of the control values in the chondrocytes obtained from two out of four donors, while the cells of the other two maintained within the range of the control levels. In the presence of insulin (100 ng/ml) 10 ng/ml of TGF-beta stimulated aggrecan synthesis to more than 90% of the control level in the chondrocytes of all donors.