GROWTH-FACTORS AND WOUND-HEALING

Growth factors are peprides that stimulate cell growth and proliferation. They have typically been named after their target cell (eg, epidermal growth factor, or EGF), their source (eg, platelet-derived growth factor, or PDGF), or biologic property (eg, transforming growth factor, or TGF). These peptides have both paracrine and autocrine functions, affecting neighboring cells and permitting self-regulation, respectively. The actions of growth factors are typically mediated by cellular receptors. Binding of growth factors and kinase receptors initiates autophosphorylation of the receptor and intracellular proteins, which then act as second messengers to initiate nuclear transcription (eg, EGF, PDGF, and insulin-like growth factor or IGF).1,2 Nuclear transcription factors activate or enhance gene transcription, and cellular proliferation then ensues.2 Growth factors have been linked to oncogenes, which are genes of viral or cellular origin whose expression transforms a cell toward the malignant phenotype. Oncogenes may encode for growth factors, their receptors, phosphorylating enzymes, or other key elements in ligand transmission.1,2. © 1991.