Biomedical Engineering Reference
In-Depth Information
in the implant and the merging process of blood vessels with
the host system. Three processes have been distinguished dur-
ing blood vessel formation, which are vasculogenesis, angiogenesis,
and arteriogenesis.
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Vasculogenesis is the
de novo
vessel-forming
process that takes place during early embryonic development.
Endothelial cells differentiate from their precursors and proliferate
within avascular tissue to form a capillary network. Angiogenesis is
the morphogenic process of new blood capillaries emerging from
preexisting vessels. The process comprises matured vessel changes,
pericyte detachment, ECM degradation and remodeling, prolifer-
ation, and migration and assembly of endothelial cells (EC) into
tubule structures. Finally comes arteriogenesis, a process of struc-
tural enlargement and remodeling of preexisting small arterioles
into larger vessels. Under well-controlled pathological and physio-
logical conditions, angiogenesis is regulated by a number of medi-
ators, either pro-angiogenic or anti-angiogenic factors.
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,
39
This
means the mediators can be used as tuning parameters in induc-
ing, controlling, and speeding up the whole angiogenesis process.
Thus in the interest of supplying oxygen to tissue, the use of angio-
genicfactorspermitsenhanceddiffusionofoxygenacrossthenewly
formedtissue.Thisismadepossiblebythestimulationofbloodves-
sel development and maturation by different growth factors such
as vascular endothelial growth factor and basic fibroblast growth
factor.
40
,
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Besides, new microvascular networks in tissue substi-
tuteshavebeenengineeredusingvascularendothelialcellsandstem
cellsorbycreatingarteriovenousshuntloops.Withtherapidforma-
tion of vessels and the merging with the sounding readily available
respiratory system, the possibility ofnecrosis has been reduced.
32.2.3
The Utilization of Oxygen-Generating Biomaterials
There are attempts to supply a su
cient amount of oxygen for tis-
sue generation via a direct method, using chemically generated oxy-
gen that is incorporated within scaffolds. It is known that peroxide
salts such as sodium percarbonate and calcium peroxide will get
dissociated into hydrogen peroxide upon dissolving in water,
42
and
subsequently the hydrogen peroxide decomposes into water and
oxygen.Suchkindofworkhasbeeninvestigatedbyresearchersfrom
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