Developmental Angiogenesis

Developmental angiogenesis is the beautiful process through which the embryo’s complex pattern of blood vessels throughout the forming body, organs and tissues is established and maintained ([1] ; [2] see Front Cover image). Blood vessels are essential for the normal development of the embryo and angiogenesis, where new vessels form from existing networks through proliferation and migration of endothelial cells to form new vessels. Moreover, the cardiovascular system is one of the first functioning tissues in the human embryo – with a beating heart and rudimentary vascular system by the 4th week of development [3] ; [4]. Indeed, vascular malformations or the failure of normal vessel formation or the failure of the transition from the embryonic to the adult vessel networks can result in damage to the embryo [5]. For example, inhibition of angiogenesis through teratogens such as thalidomide can cause birth defects [5] ; [6], in addition, misregulation of signaling molecules important for normal angiogenesis can also result in malformations, such as limb and brain defects [7]. The importance of the vascular system in embryonic development is further underlined by the large number of signaling molecules that when mutated to cause a loss-of-function in mouse embryos result in embryonic lethality due to failure of vascular development [8] ; [9].