Serum-free medium supplemented with high-concentration FGF2 for cell expansion culture of human ear chondrocytes promotes redifferentiation capacity.

For tissue engineering of autologous cartilage, cell expansion is needed to obtain the cell numbers required. Standard expansion media contain bovine serum. This has several disadvantages, that is, the risk of transmitting diseases and serum-batch variations. The aim of this study was to find a serum-free medium with at least the same potential to expand cell numbers as serum-containing media. Ear chondrocytes of three young children were expanded in either serum-containing medium (SCM; DMEM with 10% fetal calf serum) or serum-free medium (SFM; DMEM with ITS+) supplemented with 5 or 100 ng/mL fibroblast growth factor-2 (FGF2). To promote cell adherence onto the culture flask, the serum-free conditions were cultured with 10% serum for 1 day after each trypsinization. After the fourth passage, the chondrocytes were encapsuled in alginate beads and redifferentiated in a SFM (DMEM with ITS+, hydrocortisone, and L-ascorbic acid) supplemented with 10 ng/mL IGF-I and 10 ng/mL TGFbeta-2. Results showed that expansion in SFM with 100 ng/mL FGF2 was comparable to expansion in SCM. Redifferentiation with SFM with IGF-I and TGFbeta-2 showed high collagen type II expression and high GAG/DNA production regardless of which expansion medium had been used. However, chondrocytes expanded in SFM with 100 ng/mL FGF2 resulted in less positive cells for collagen type I and 11-fibrau (a fibroblast membrane marker). The present study shows that it is possible to use serum-free medium for tissue engineering of cartilage. Expansion of immature ear chondrocytes in SFM supplemented with high-concentration FGF2 resulted in high cell numbers, which in addition had better redifferentiation capacity than cells expanded in medium with 10% serum.