Biochemical and functional modulation of the cartilage collagen network by IGF1, TGF beta 2 and FGF2

Objective: Examine effects of insulin-like growth factor 1 (IGF1), transforming growth factor β2 (TGFβ2) and fibroblast growth factor 2 (FGF2) on proteoglycan and collagen network and biomechanical properties of the newly formed cartilage matrix. Methods: Bovine articular chondrocytes were cultured in alginate beads for 3 weeks with or without FGF2, TGFβ2 or IGF1 in the presence of 10% FCS. Proteoglycan content, collagen content, hydroxylysylpyridinoline cross-links and overall matrix metalloproteinase (MMP) activity in the culture medium were measured. Alginate disks cultured for 5 weeks were used to evaluate the effect of growth factors on mechanical properties of the construct by determining the equilibrium aggregate modulus and secant modulus. Results: IGF1 increased collagen and proteoglycan deposition. FGF2 mainly decreased collagen deposition and TGFβ2 proteoglycan deposition. A decrease in cross-links was observed in matrix produced by chondrocytes cultured in the presence of TGFβ2. IGF1 and FGF2 had no influence on the number of cross-links per collagen molecule. Overall MMP activity was significantly higher in culture medium of cells cultured with FGF2. TGFβ2 and IGF1 had no effect on MMP activity. After 35 days of culture, the matrix produced under influence of IGF1 had a lower permeability and a trend to increase stiffness. FGF2 showed a trend to lower both properties. TGFβ2 had no effect on these parameters. Conclusion: IGF1, TGFβ2 and FGF2 had differential effects on collagen network formation. Of the three growth factors tested, IGF1 seems to be best in promoting the formation of a functional collagen network since it increased proteoglycan and collagen deposition and improved the mechanical properties. © 2006 OsteoArthritis Research Society International. Chemicals / CAS: alginic acid, 28961-37-7, 29894-36-8, 9005-32-7, 9005-38-3; pyridinoline, 63800-01-1; somatomedin C, 67763-96-6; Aggrecans; Collagen Type II; Collagen, 9007-34-5; DNA, 9007-49-2; Fibroblast Growth Factor 2, 103107-01-3; Insulin-Like Growth Factor I, 67763-96-6; Matrix Metalloproteinases, EC 3.4.24.-; Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase, EC 1.14.11.4; Protein-Lysine 6-Oxidase, EC 1.4.3.13; Proteoglycans; Transforming Growth Factor beta2