Molecular and Cellular Angiogenesis

Blood vessels deliver oxygen and nutrients — essential for survival of cells in multicellular organisms. Since the diffusion for oxygen is limited, cells in the mammalian body are located within a short range of blood vessels. The growth of new blood vessels via vasculogenesis or angiogenesis is tightly regulated by an intricate balance between activators and inhibitors. In a normal adult, angiogenesis cyclically occurs during reproduction and as part of a self-limiting reparative program after wounding or during inflammation. The remainder of the adult vasculature is quiescent, with only 0.01% of endothelial cells undergoing cell division. During pathological conditions, angiogenesis occurs in an uncontrolled manner. Leonardo Da Vinci was among the first to demonstrate angiogenesis in an inflamed human lung. We now know that abnormal vascular growth or function also contributes to numerous nonneoplastic disorders of significant morbidity, and the list is expanding every day (Table 1). For example, an excess of vessels in diabetic retinopathy can lead to blindness or promote cancer.