Growth Factor Receptor Proteins


 Growth Factor Receptor Proteins Background

Growth factors are a group of cytokines, containing members like Transforming Growth Factor β-1 (TGFβ-1), Insulin-like Growth Factor I (IGF-I), Bone Morphogenic Protein 2 (BMP-2), Bone Morphogenic Protein 7 (BMP-7), and Fibroblastic Growth Factor 2 (FGF-2). TGFβ and IGF-I have been shown to stimulate the production of proteoglycans (anabolic). Additionally, IGF-I has been shown to increase chondrocyte proliferation (mitogenic). BMP-2 and BMP-7 have been shown to enhance proteoglycan synthesis, and it has been indicated that BMP-7 maybe also increase the synthesis of hyaluronic acid and its receptor CD44. FGF-2 can help the regenerative capacity of chondrocytes, as it will stimulate proliferation and redifferentiation once the chondrocytes are moved from monolayer culture to a 3D culture in a scaffold. Moreover, studies by the Loeser laboratory have shown that growth factors IGF-I and TGFβ-1 when added exogenously to the culture medium can enhance the expression of certain integrins, increasing the adhesivity of the cells to the matrix; however, TGFβ-1 had the opposite effect on the α1β1 integrin, decreasing chondrocyte affinity to collagen VI.