Chondrogenic differentiation of human adipose-derived stem cells in polyglycolic acid mesh scaffolds under dynamic culture conditions

Chondrogenic differentiation of human adult adipose-derived stem cells was studied in vitro for the development of engineered cartilage tissue. Cells cultured under dynamic conditions in polyglycolic acid (PGA) scaffolds produced substantially higher glycosaminoglycan (GAG) and total collagen levels than cells in pellet cultures. This result reflects the importance of cell attachment and cell–scaffold interactions in stem cell differentiation and chondrogenesis. Although gene expression levels for both aggrecan and collagen type II were up-regulated significantly in PGA cultures treated with transforming growth factor β1 (TGF-β1), synthesis of GAG but not collagen type II was enhanced in tissue constructs when TGF-β1 was added to the medium. Bone morphogenetic protein-6 (BMP-6) in the presence of TGF-β1 was effective in improving GAG and total collagen production when the cells were pre-treated with fibroblast growth factor-2 (FGF-2) prior to scaffold seeding. Extending the culture duration from 2 to 5 weeks did not improve cartilage development in PGA scaffolds; loss of cells from the constructs suggested that the rate of scaffold degradation exceeded the rate of replacement by ECM during the 5-week period. Stem cells in PGA scaffolds were cultured in perfusion-type recirculation bioreactors operated with periodic medium flow reversal. The highest levels of GAG and collagen type II accumulation were achieved in the bioreactor cultures after the seeding cell density was increased from 2 × 107 to 4 × 107 cells per scaffold.