Recent Improvements in in vitro Angiogenesis Assays

Blood vessel formation, a highly organized sequence of cellular events, is initiated with activation of endothelial cells (ECs) followed by proliferation, sprouting, migration, tube formation, and maturation. Two fundamental processes of blood vessel formation are vasculogenesis and angiogenesis. Vasculogenesis refers to the de novo process of new vessel formation by migration and differentiation of endothelial progenitors into endothelial cells (ECs), whereas angiogenesis refers to the extension of pre-existing blood vessels through EC sprouting and subsequent stabilization by pericytes1,2. Angiogenesis plays an important role in not only embryonic development but also adult reproductive function and wound healing3. Furthermore, abnormal angiogenesis is associated with many pathological conditions such as diabetic retinopathy, rheumatoid arthritis, and tumor progression. Thus, exploring key molecular mechanisms of angiogenesis has become one of the most important biomedical research areas because drugs to control angiogenesis hold great promise in overcoming vascular malformation-associated diseases, especially cancer4.