Evaluation of thermoreversible polymers containing fibroblast growth factor 9 (FGF‐9) for chondrocyte culture

Abstract We previously evaluated a thermoreversible polymer gel composed of N‐isopropylacrylamide and acrylic acid as a cell culture substrate and cell‐delivery vehicle. The copolymer promoted phenotype expression and amplification of chondrocytes. In this study, we determined whether addition of fibroblast growth factor 9 (FGF‐9), which is mitogenic for chondrocytes, would further enhance cell proliferation and phenotype expression in the polymer. We tested the hypothesis that the thermoreversible polymer containing FGF‐9 would promote increased chondrocyte proliferation and phenotype expression. Articular chondrocytes (1 × 10⁵/150 μL) were plated onto control (without gel) and gel containing 24‐well plates. The gels were prepared in media alone or in media containing heparin (100 μg/mL) and FGF‐9 (5 μg/mL). The cultures were incubated at 37°C in 5% CO₂ for 3 days. Cells remained viable in the thermoreversible polymer in the presence or absence of FGF‐9. Addition of FGF‐9 to the copolymer did not induce proliferation and the cell numbers did not increase. Reverse transcription polymerase chain reaction (RT‐PCR)‐determined expression of chondrocyte markers collagen type II and aggrecan. FGF‐9 did not enhance chondrocyte proliferation nor alter the phenotype after 3 days in culture. These findings suggest the poly(NiPA‐co‐AAc) gel alone may provide the optimal 3D environment for propagation of chondrocytes. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 367–372, 2004