Fibroblast Growth Factors (FGFs) are a family of growth factors which play an important role in tissue repair and regeneration. They possess high affinity for heparan sulfate proteoglycans (HPSGs) and can interact with heparin-like glycosaminoglycans (HLGAGs) of the extracellular matrix (ECM).
Fibroblast Growth Factors contain a central core of 140 amino acids with high homology, which forms a structure topologically identical to interleukin-1β (IL-1β). The first of these proteins were historically named as "FGFs" for their biological activities of fibroblast stimulating, nevertheless, the "FGFs" is meant to imply that these proteins share similar structures today. In vertebrates, the FGF family contains 22 members with their molecule mass ranging from 17 to 34 KDa, and the amino acid identity between the members is 13-71%.
Members of FGF family can be phylogenetically classified into seven subfamilies; FGF 1/2, FGF 4/5/6, FGF 3/7/10/22, FGF 8/17/18, FGF 9/16/20, FGF 11/12/13/14, and FGF 19/21/23. Whereas, based on the action mechanisms, the FGF family can be divided into three categories, including paracrine, endocrine, and intracrine FGFs. Paracrine FGFs is comprised by members of subfamilies FGF1/2, FGF 4/5/6, FGF 3/7/10/22, FGF 8/17/18, FGF 9/16/20; three members of FGF 19/21/23 subfamily constitute endocrine FGFs; and intracrine FGFs contains the four members of subfamily FGF 11/12/13/14. Except FGF11, FGF12, FGF13, and FGF14, members of FGFs family are secreted ligands, which transmit their signals by binding to FGF receptors (FGFRs). The signals are further transmitted through the RAS/MAP kinase pathway, PI3 kinase/AKT pathway, and PLCγ pathway.