VEGF or vascular endothelial growth factor is a signalling molecule that promotes the formation of new blood vessels.
VEGF is made by various different types of cells including macrophages, keratinocytes, tumor cells, platelets, and mesangial cells in the kidney. As well as promoting the formation of blood and lymphatic capillaries, VEGF also plays a role in the formation of bones and blood and is required for wound healing and embryonic development.
The production of VEGF can be induced in hypoxic cells or those that are deprived of oxygen. Such an oxygen-deprived cell is capable of producing a substance called hypoxia inducible factor (HIF). This is a transcription factor that induces the release of VEGF.
The VEGF produced by these oxygen-starved cells enters the bloodstream and binds to VEGF receptors present on the surface of endothelial cells, which line the blood vessels. This, in turn, triggers the tyrosine kinase pathway, which leads to formation of new blood vessels, a process referred to as angiogenesis.
HIF-1-alpha and HIF-1-beta are both continually produced but these proteins differ in that HIF-1-alpha is highly oxygen labile, meaning it is easily degenerated in aerobic environments.
Therefore, if the blood supplies cells and tissues with an adequate amount of oxygen, the HIF-1 is degraded, whereas, if a cell becomes hypoxic, the production of HIF-1-alpha continues and forms a complex with HIF-1-beta that goes on to stimulate the release of VEGF.