Angiogenesis literally means creation of new blood vessels. The word “angio” means blood vessels while “genesis” means creation.
Angiogenesis is an important process that occurs both during health and disease. Blood is important in the body as it carries oxygen and nutrients to all the parts of the body via blood vessels like arteries and brings back the toxins and wastes from these peripheral organs for purification via veins.
When a new tissue is formed, it is vital that it has blood supply for its growth and sustenance. For this formation of blood vessels or angiogenesis is important.
Angiogenesis in normal physiology
Formation of new tissues involves formation of new blood vessels. Some of the normal situations where angiogenesis is important and necessary include those for repair of wounds and the formation of the placenta during pregnancy.
The normal body has controls over the process of angiogenesis. These are complex and intricate pathways. There are several “on” and “off” switches that regulate the process. The “on” switches are some chemicals that stimulate blood vessel formation while “off” switches are chemicals that inhibit blood vessel-formation.
The on switches are termed angiogenic growth factors and when formation of new blood vessels are needed, greater amounts of these factors are created than angiogenesis inhibitors or off switches.
When inhibitors are present in greater amounts than stimulators, angiogenesis is prevented.
Angiogenesis in cancers and disease
The body strives to maintain a balance of angiogenesis regulators. When this control is lost, either too much or too little angiogenesis may be the result.
Angiogenesis becomes cause for worry when it occurs within tumors and cancers, feeding and sustaining them.
Newer agents that treat cancer are targeting the angiogenesis factors so that prevention of new blood vessels supplying the tumor could starve off the cancer cells and eventually kill them.
Angiogenesis and metastasis
Angiogenesis is an essential component of the metastatic pathway. The new blood vessels that are formed allow the cancer cells to leave the original site of the cancer and spread to distant organs via blood. Thus the higher the density of new blood vessels within some tumors, the higher is the risk of metastasis of that tumor.
Tumor angiogenesis stimulators include chemicals that belong to fibroblast growth factor and vascular endothelial growth factor families.
Tumors may also activate the off switches like angiogenic inhibitors such as angiostatin and endostatin that alter angiogenesis at the primary site of the tumor as well as the site of metastasis.