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Edward M. Conway, Désiré Collen, Peter Carmeliet, Molecular mechanisms of blood vessel growth, Cardiovascular Research, Volume 49, Issue 3, February 2001, Pages 507–521, https://doi.org/10.1016/S0008-6363(00)00281-9
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Extract
Time for primary review 12 days.
1 From avascular to vascular
From the earliest stages, the embryo develops in the absence of vascularization, receiving its nutrition by diffusion [1]. In an ordered and sequential manner, however, the embryo rapidly transforms into a highly vascular organism, survival being dependent on a functional, complex network of capillary plexuses and blood vessels. ‘Vasculogenesis’ refers to the initial events in vascular growth in which endothelial cell precursors (angioblasts) migrate to discrete locations, differentiate in situ and assemble into solid endothelial cords, later forming a plexus with endocardial tubes (Fig. 1). The subsequent growth, expansion and remodeling of these primitive vessels into a mature vascular network is referred to as ‘angiogenesis’ (Fig. 1). This process is characterized by a combination of sprouting of new vessels from the sides and ends of pre-existing ones, or by longitudinal division of existing vessels with periendothelial cells (intussusception), either of which may then split and branch into precapillary arterioles and capillaries. Depending on the ultimate fate with respect to the type of vessel (artery, vein, capillary) and vascular bed, activated endothelial cells that are migrating and proliferating to form new vessels, forming anastomotic connections with each other, become variably surrounded by layers of periendothelial cells — pericytes for small vessels and smooth muscle cells for large vessels (‘vascular myogenesis’) (Fig. 1) [2]. During this dynamic period, extracellular matrix produced by mural cells, serves to stabilize the network. Finally, further functional modifications of larger arteries occur during ‘arteriogenesis’ as a thick muscular coat is added, concomitant with acquisition of viscoelastic and vasomotor properties (Fig. 1).
