Chondrocyte extracellular matrix synthesis and turnover are influenced by static compression in a new alginate disk culture system

The goal of this study was to examine the effects of mechanical compression on chondrocyte biosynthesis of extracellular matrix (ECM) components durin g culture in a new alginate disk culture system. Specifically, we have exam ined chondrocyte biosynthesis rates, and the structure of aggrecan core pro tein species present in the cell-associated matrix (CM), in the further rem oved matrix (FRM) and in the surrounding culture medium. In this alginate d isk culture system, chondrocytes can be subjected to mechanical deformation s similar to those experienced in vivo. Our results show that over an 8-wee k culture period, chondrocytes synthesize a functional ECM and can respond to mechanical forces similarly to chondrocytes maintained in native cartila ge. In the alginate disk system, static compression was shown to decrease a nd dynamic compression to increase synthesis of aggrecan of bovine chondroc ytes. Western blot analysis of the core proteins of aggrecan molecules iden tified a number of different species that were present in different relativ e amounts in the CM, FRM, and medium. Over 21 days of culture, the predomin ant form of aggrecan found in the ECM was a full-length link-stabilized spe cies. In addition, our data show that the application of 40 h of static com pression caused an increase in the proportion of newly synthesized aggrecan molecules released into the medium. However, this was not accompanied by a significant change in the size and composition of aggrecan and aggrecan fr agments in the different compartments, suggesting that mechanical compressi on did not alter the catabolic pathways. Together, these data show that cho ndrocyte function is maintained in an alginate disk culture system and that this culture system is a useful model to examine chondrocyte ECM assembly and some aspects of catabolism normally found in vivo, (C) 2000 Academic Pr ess.