Coalescent angiogenesis—evidence for a novel concept of vascular network maturation

Abstract

Angiogenesis describes the formation of new blood vessels from pre-existing vascular structures. While the most studied mode of angiogenesis is vascular sprouting, specific conditions or organs favor intussusception, i.e., the division or splitting of an existing vessel, as preferential mode of new vessel formation. In the present study, sustained (33-h) intravital microscopy of the vasculature in the chick chorioallantoic membrane (CAM) led to the hypothesis of a novel non-sprouting mode for vessel generation, which we termed “coalescent angiogenesis.” In this process, preferential flow pathways evolve from isotropic capillary meshes enclosing tissue islands. These preferential flow pathways progressively enlarge by coalescence of capillaries and elimination of internal tissue pillars, in a process that is the reverse of intussusception. Concomitantly, less perfused segments regress. In this way, an initially mesh-like capillary network is remodeled into a tree structure, while conserving vascular wall components and maintaining blood flow. Coalescent angiogenesis, thus, describes the remodeling of an initial, hemodynamically inefficient mesh structure, into a hierarchical tree structure that provides efficient convective transport, allowing for the rapid expansion of the vasculature with maintained blood supply and function during development.

VEGF Gene Expression and Angiogenesis in the Chorioallantoic Membrane: the Role of Cloprostenol

“…3, 4, and 5, the effects of cloprostenol on VEGF gene expression were fluctuating, and this result may be due to that the VEGF receptors play a key role in this response, and it is well known that their receptors have wide variations depending on the age of development (note the difference in response between 6 th and 9 th days of incubation). The maturity of blood vessels may be contributed to these variations, also the process of angiogenesis requires more quantity and quality of blood vessels in the embryo [22,23]. Our results reveal that the effects of PGF 2 α analogue on the blood vessels may be influenced in a time-dependent manner, so many interacting factors play a key role in VEGF gene expression [24].…”

Engineering Spatiotemporal Control in Vascularized Tissues

“…During the process of angiogenesis, novel capillaries are formed from existing vasculature via the process of sprouting and intussusception. Several cellular functions occur during angiogenesis categorized into a phase of activation involving initiation and progression and a phase of resolution that includes processes of termination and maturation of vessel [ 9 ]. Biochemical processes such as ischemia or inflammation causes sprouting that promotes stimulatory autocrine and paracrine cytokines release, including the very potent vascular endothelial growth factor (VEGF) [ 10 ].…”

Flow-Responsive Noncoding RNAs in the Vascular System: Basic Mechanisms for the Clinician

“…Flow sensing elements include transmembrane and cytoskeletal proteins, networks of sugars and ion channels. Hemodynamic forces of blood flow are known to have an important impact on vascular development, function and disease [3][4][5][6]. In fact, increasing evidence now indicates that fluid shear stress (FSS), induced by blood flow, is an essential factor promoting intracellular biochemical signals, and its role in physiological and pathological vascular remodeling has received increasing attention.…”