Human Vascular endothelial growth factor (VEGF), also known as VEGF-A and vascular permeability factor (VPF), belongs to the platelet-derived growth factor family of cysteine-knot growth factors. It is a potent activator in vasculogenesis and angiogenesis both physiologically and pathologically. VEGF-A has 8 differently spliced isoforms, of which VEGF165 is the most abundant one. VEGF165 is a disulfide-linked homodimer consisting of two glycosylated 165 amino acid polypeptide chains. VEGF stimulates the cellular response through binding to tyrosine kinase receptors VEGFR1 and VEGFR2 on the cell surface. It is widely accepted that VEGFR2 mediate almost all of the known cellular responses to VEGF while the function of VEGFR1 is less defined and is thought to modulate the VEGFR2 signaling.