Biochemical characterization of long‐term culture of the swarm rat chondrosarcoma chondrocytes in agarose

Difficulty in maintaining phenotypic stability of the Swarm rat chondrosarcoma in long‐term monolayer cultures has prompted investigation of alternative conditions that would enable extended maintenance of these cells, permitting use of the tumor as a model system for the long‐term study of proteoglycan metabolism. Morphological analysis of the growth of the chondrosarcoma chondrocytes in agarose has shown stability of the culture over a 20 day period with respect to the ability of the cells to proliferate and synthesize an Alcian blue‐positive extracellular matrix. The present study confirms these findings through analysis of the growth characteristics of the culture and the pattern of proteoglycan‐rich matrix at a rate dependent on the initial plating density and concentration of serum in the culture medium. These factors similarly affect the proliferative capabilities of the culture as demonstrated by the growth curves obtained at different culture conditions. During 20 days in culture, the cells synthesize an aggregating chondroitin sulfate proteoglycan and collagen type II, typical of cartilage and this chondrosarcoma. In addition, small molecular weight proteoglycans were found to be present at concentrations of up to 10% of the total proteoglycan population. Degradative rates are slow, the proteoglycan half‐life is about 30 days, but can be enhanced with retinol, reducing the half‐life to 2 days.