**3.3 Fibroblast growth factor (FGF)**

There are two FGF members used in cartilage regeneration. One of them is called as basic FGF (bFGF) or FGF-2, and the other one is called as FGF-18. FGF-2 increases anabolic material levels and decreases aggrecanase levels in cartilage. In vivo study has indicated that bFGF can promote cartilage repair [60]. However, some study indicated that the concentration of FGF-2 in synovial fluid samples of OA patients is approximately twice that of normal healthy knee joints [61]. Further studies found that FGF-2 promoted the repair of partial thickness defects of articular cartilage in immature rabbits but not in mature rabbits [62].

A rat model study has shown that FGF-18 stimulates chondrogenesis and cartilage repair in a concentration-dependent manner [63]. More studies have demonstrated that FGF-18 may present a therapeutic agent for osteoarthritis [64, 65]. A recombinant form of human FGF-18 has been used for cartilage injury treatment [66].
