Enhanced cartilage tissue engineering by sequential exposure of chrondrocytes to FGF-2 during 2D expansion and BMP-2 during 3D cultivation

Bovine calf articular chondrocytes, either primary or expanded in monolayer s (2D) with or without 5 ng/ml fibroblast growth factor-2 (FGF-2), were cul tured on three-dimensional (3D) biodegradable polyglycolic acid (PGA) scaff olds with or without 10 ng/ml bone morphogenetic protein-2 (BMP-2). Chondro cytes expanded without FGF-2 exhibited high intensity immunostaining for sm ooth muscle a-actin (SMA) and collagen type I and induced shrinkage of the PGA scaffold, thus resembling contractile fibroblasts. Chondrocytes expande d in the presence of FGF-2 and cultured 6 weeks on PGA scaffolds yielded en gineered cartilage with 3.7-fold higher cell number, 4.2-fold higher wet we ight, and 2.8-fold higher wet weight glycosaminoglycan (GAG) fraction than chondrocytes expanded without FGF-2. Chondrocytes expanded with FGF-2 and c ultured on PGA scaffolds in the presence of BMP-2 for 6 weeks yielded engin eered cartilage with similar cellularity and size, 1.5-fold higher wet weig ht GAG fraction, and more homogenous GAG distribution than the correspondin g engineered cartilage cultured without BMP-2. The presence of BMP-2 during 3D culture had no apparent effect on primary chondrocytes or those expande d without FGF-2. In summary, the presence of FGF-2 during 2D expansion redu ced chondrocyte expression of fibroblastic molecules and induced responsive ness to BMP-2 during 3D cultivation on PGA scaffolds. J. Cell. Biochem. 83: 121-128, 2001. (C) 2001 Wiley-Liss, Inc.