Angiogenesis.
The growth of new blood vessels involves the dissolution of the basement membrane, outward migration, and proliferation of endothelial cells to form new capillaries. In part, angiogenesis is dependent on peptide growth factors, many of which have been isolated and are now synthesized by recombinant DNA techniques. In animals, angiogenic factors are found in damaged skeletal muscles, tumors, and many other tissues. The infusion of angiogenic factors in animals improves wound healing, such as in bone and skin grafts. Topically applied growth factors in patients with chronic nonhealing cutaneous wounds results in a dramatic acceleration of angiogenesis and epithelialization. In diseases in which there is an excess of vascularization (tumors, osteoarthritis, diabetic retinopathy), research is directed at the identification and production of antiangiogenic agents. Although still highly experimental, the clinical use of angiogenic and angiostatic agents could cause as significant a change in medical practice as antibiotics.