Growth factors and fibrochondrocytes in scaffolds

Four growth factors, transforming growth factor-β1 (TGF-β1), platelet-derived growth factor-AB (PDGF-AB), insulin-like growth factor I (IGF-I), and basic fibroblastic growth factor (bFGF), were tested at different concentrations for their effects on extracellular matrix (ECM) production in three-dimensional cultures of meniscal fibrochondrocytes. Cells from New Zealand white rabbits were seeded on poly-glycolic acid (PGA) scaffolds and were stimulated with growth factors for three weeks. 3H-proline and 35S-sulfate labels were used to measure uptake of collagen and glycosaminoglycan (GAG) components, respectively. Biochemical assays were performed to measure the total collagen, GAG, and DNA present in the scaffolds at the end of the study. TGF-β1 (10 and 100 ng/ml) stimulated both 3H-proline and 35S-sulfate uptake, showing a dose-dependent response for both and a temporal response for 35S-sulfate uptake. IGF-I (5 ng/ml) and bFGF (25 and 100 ng/ml) showed increases in 3H-proline uptake by the third week of growth factor addition. PDGF-AB did not show notable increases in uptake. Because TGF-β1 (10 and 100 ng/ml) had visibly denser scaffolds, as evidenced by gross microscopy, at 100×, and the strongest uptake responses to both 35S-sulfate and 3H-proline, it appears to be the most effective growth factor for use in scaffold-based approaches to tissue engineer the knee meniscus.