Understanding angiogenesis and its clinical applications.

Angiogenesis is the growth of new vessels from pre-existing blood vessels. Angiogenesis is critical during embryogenesis but occurs minimally in healthy adults, except in wound repair, inflammation, female reproductive organs, and pathologic conditions. Various growth factors and proteins, elements of the extracellular matrix, components of the coagulation/fibrinolytic system, and platelets interact with the endothelial cells and pericytes of blood vessels to regulate angiogenesis. Characterization of angiogenic factors has revealed that remodeling of the extracellular matrix occurs during angiogenesis, mediated by integrins that are found on the endothelial cell surface membrane. Counter-regulatory antiangiogenic proteins and molecules that show an intricate balance in the regulation of angiogenesis have also been characterized. Components of the coagulation/fibrinolysis cascade also play a critical role in angiogenesis. Elucidation of the mechanisms of angiogenesis has led to better understanding of certain disease states. Ongoing studies are evaluating the stimulation of angiogenesis to treat ischemic disorders, and the inhibition of angiogenesis to prevent abnormal proliferation in malignant and non-malignant disorders.