Vasculature Growth - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 601

Chapter 10
Vasculature Growth
Vasculogenesis , an embryological process, defines the formation of capillary plexi
from endothelial precursor cells. A primitive vascular network is built via the assem-
bly of angioblasts. Initial patterning of embryonic vascular network is independent
of hemodynamic forces. The onset of blood circulation contributes to vasculature
remodeling.
Angiogenesis corresponds to the maturation of the primary vascular network
during embryo- and fetogenesis as well as the expansion of existing vasculature,
i.e., generation of new branches from this network in utero as well as vascu-
lature extension after birth during tissue development and repair. Angiogenesis
enables delivery of oxygen and nutrients to ischemic regions. An intermittent, low-
magnitude ischemia during exercise in normal conditions as well as during ischemic
preconditioning activates angiogenesis for muscle adaptation.
Angiogenesis relies on the integration of hemodynamic and chemical sig-
nals. The vascular growth requires the coordinated proliferation and migration of
endothelial cells. It involves vessel dilation or contraction, sprouting and branching,
as well as intussusceptive involution and pruning (non-functional vessels). Intussus-
ception, another type of remodeling of pre-existing vessels, i.e., insertion of tissular
pillars into blood vessel lumens, enables vessel splitting.
Transcriptional, post-transcriptional, and post-translational mechanisms partic-
ipate in the control of endothelial cell behavior during sprouting, branching with
leading endothelial tip cells and trailing stalk cells, and tubulogenesis [ 886 ].
Specialized endothelial tip cells at the leading edge of vascular sprouts form
filopodia in response to guidance signals.
Lymphangiogenesis is the development of new lymph vessels. Arteriogenesis
deals with formation of mature arterioles and arteries with smooth myocytes,
particularly for collateral development to bypass an obstructed artery.
Neovascularization involves 3 major processes stimulated by several chemical,
physical, and mechanical (wall shear stress and intramural [circumferential and
longitudinal] tension) factors: (1) postnatal vasculogenesis, i.e., formation of new