FBS suppresses TGF-beta1-induced chondrogenesis in synoviocyte pellet cultures while dexamethasone and dynamic stimuli are beneficial.

In vitro cartilage tissue engineering culture systems benefit from a fine balance of biochemical and mechanical components to maintain the chondrocyte phenotype. This balance, however, can be disrupted by using typical methods for cultivating chondrogenic cells in medium supplemented with fetal bovine serum (FBS) and growth factors. Our goal was to determine the effects of fluid-dynamic stimuli, fetal bovine serum and dexamethasone on the chondrogenesis of 14-day synoviocyte pellet cultures in the presence of TGF-beta1. We employed a pellet culture system that provides a highly cellular three-dimensional structure that permits differentiation and extracellular matrix synthesis. Our results indicated that FBS inhibited glycosaminoglycan (GAG) and type II collagen production. Interestingly, the effect of dynamic stimuli was modulated by the presence of FBS; mixed serum-free cultures had increased GAG production, whereas mixed cultures with 10% FBS exhibited less GAG production compared with their static counterparts, possibly due to pronounced suppressive effects of FBS via increased transport. Dexamethasone addition during the first week of culture resulted in enhanced extracellular matrix production and increased cellularity. Moreover, the presence of 10% FBS in addition to ITS(+) and TGF-beta1 did not significantly increase cell proliferation compared with serum-free medium. These results indicate the importance of a comprehensive analysis of growth conditions for each cell culture system.