Vascularization of organs and tissues is carried out by two related, but distinct processes: vasculogenesis and angiogenesis. Vasculogenesis is a process where primitive blood vessels develop from angioblast precursor cells that differentiate and assemble into cord-like vascular structures which further connect into a primary network. Angiogenesis is a process of formation of new blood vessels from pre-existing vessels by sprouting, splitting, and remodelling of vascular network. It is a complex process including a chain of events like endothelial cell activation, growth, migration and capillary morphogenesis.
The process of angiogenesis requires the involvement of pro- and anti-angiogenic factors. Beside numerous biogenic factors, several modulators such as inhibitors, small molecules and monoclonal antibodies have been characterised that interfere with angiogenesis. Small molecules such as adenosine, 1-butyryl glycerol, prostaglandins E1 and E2 are a few examples also reported for their angiogenic activity. Monoclonal antibodies such as bevacizumab and celecoxib and small molecules such as thalidomide are already used extensively in cancer therapy for their anti-angiogenic property.