The Putative Convergent and Divergent Natures of Angiogenesis and Arteriogenesis

The postnatal function of blood vessels is determined by the physiology of individual tissues and organs as well as the size and mass of an individual species, and a corollary to this premise is the suggestion that not all blood vessels are created equal. Postnatally, new blood vessel growth occurs either by angiogenesis or arteriogenesis, and thus, it is anticipated that the mechanisms responsible for these processes will exhibit convergent and divergent features.1 Because angiogenesis involves the coordinated migration, proliferation, and differentiation of endothelial cells (ECs) and pericytes from existing vascular beds and arteriogenesis, the growth of muscular arteries, requires similar events regulated by ECs and smooth muscle cells (SMCs) from preexisting arteries, it is anticipated that these cells will have evolved divergent mechanisms responsible for their postnatal development and growth.2,3 Indeed, a recent study by Hershey et al4 examined the relationship between angiogenesis and arteriogenesis in the development of functional collateral blood vessels in the rabbit ischemic hind limb model and observed that although capillary sprouting via angiogenesis occurred as an early response to tissue ischemia, improved collateral blood flow occurred only as a late response when arteriogenesis could be demonstrated using angiographic methods. These data suggest that a temporal relationship may exist between angiogenesis and arteriogenesis in which the angiogenic component precedes the arteriogenic component in the formation of a collateral vasculature visualized by angiographic methods.The angiogenesis factor, VEGF, is well described as a rapidly induced hypoxia-response gene.5 If angiogenesis and arteriogenesis were not temporally related, it is likely that the mechanisms responsible for the angiogenic and arteriogenic responses may both be due to the function …