Four growth factors, transforming growth factor-pl (TGF-PI), 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-PI (10 and 100 ng/ml) stimulated both 3H-proline and 3SS-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-p1 (10 and 100 ng/ml) had visibly denser scaffolds, as evidenced by gross microscopy, at lOOx, and the strongest uptake responses to both "S-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.

To tissue engineer the knee meniscus, our laboratory follows a paradigm that includes biomaterial scaffolding, mechanical stimulation, and growth factor addition. The aim of this study was to study extracellular matrix (ECM) component uptake by meniscal fibrochondrocytes when stimulated with platelet-derived growth factor AB, transforming growth factor beta(1) (TGF-beta(1)), insulin-like growth factor type I, and basic fibroblast growth factor at various concentrations (low, medium, and high levels for each). Growth factors were applied to monolayer cultures for 3 weeks in a soluble form as part of the culture medium. Radiolabeling with [3H]proline and [(35)S]sulfate was performed to indicate collagen and glycosaminoglycan production, respectively. TGF-beta(1) is the only growth factor that increased the uptake of both components. It showed the most consistent behavior and the highest response. There is no conclusive evidence whether the high concentration of TGF-beta(1) (100 ng/mL) is better than the medium concentration (10 ng/mL). Therefore the results of this study demonstrate that TGF-beta(1) at either 10 or 100 ng/mL can be used to upregulate ECM production in monolayer cultures of meniscal fibrochondrocytes.

To fully understand the function of the knee meniscus, it is important to define the characteristics of its structure and composition, and how they vary spatially within the tissue. The meniscus is an excellent example of how structure can confer function in a mechanical device. The goal of this article is to summarize current findings related to meniscal properties. Cellular, biochemical, ultrastructural, and biomechanical characteristics are compared in the different zones, depths, and topographical regions of the knee meniscus. It is important to note the wide variety of species and testing methods that have been used to evaluate such properties. These variations render difficult direct comparisons of the properties of this anisotropic and inhomogeneous tissue. Understanding the structure‐function relationships within the meniscus will lead to better design of replacements for this tissue.