Stimulation of chondroitin sulfate proteoglycan production by chondrocytes in monolayer.

Chondrocytes in monolayer undergo morphological and biochemical changes which culminate in the establishment of cartilage nodules in vitro. Chondroitin sulfate or heparin, added to the culture media of these cells, stimulates the production of chondroitin sulfate proteoglycan over the entire period of culture with a maximum effect during the log phase of growth. In addition, a lag of 2-3 hours is required before an increase in sulfate incorporation into polysaccharide is observed. The responsiveness of chondrocytes is influenced by several factors, such as cell density, conditioned media and enzyme treatment. Furthermore, puromycin abolishes the endogenous as well as the stimulated synthesis, demonstrating the necessity for core protein synthesis in both synthetic processes. Addition of beta-D-xylosides (which presumably act as initiators of chondroitin sulfate polysaccharide synthesis) and chondroitin sulfate, concurrently, stimulate sulfate incorporation to levels higher than either agent alone, indicating that these compounds act by different mechanisms.