Biomedical Engineering Reference
In-Depth Information
be maintained until the cellular components had satisfactorily reinforced
the construct.
12.4.4 Allogenic and xenogenic vascular scaffolds
Tissue composition and organisation are integral to an organ's optimal
functioning. Hence, employing scaffolds with an analogous structure to
naturally occurring vessels may produce TEBVs whose functionality
closely resembles that of healthy arteries. 'Functional' scaffolds, such as
decellularised allogenic and xenogenic conduits, possess a macro- and
micro-architecture which more closely resembles that of naturally occur-
ring arteries. These scaffolds retain most of their biological and mechani-
cal characteristics, thereby improving the integration and function of
TEBVs. Initially, on implantation, 'functional' scaffolds are more robust
than conduits manufactured from other naturally occurring components
such as collagen and fi brin hydrogels. Conduits with an appropriate
calibre, including human umbilical arteries and veins and bovine and
porcine carotid arteries, have been employed as scaffolds in vascular
tissue engineering applications (Dahl et al. , 2003; Daniel et al. , 2005; Gui
et al. , 2009; Holdsworth et al. , 1997; McFetridge et al. , 2004b). Allogenic
scaffold supplies are inadequate due to the limited availability of donated
human tissue and pertinent ethical issues (Anderson, 1999; Delaney and
Hershenov, 2009). The ECM constituents of xenogenic blood vessels are
conserved among species and the conduits are relatively easy to obtain
and have a consistent quality (Bernard et al. , 1983; Constantinou and
Jimenez, 1991; Stegemann et al. , 2007). Despite their structural similarities
with human host vessels, xenogenic grafts elicit an immune response
which is more vigorous than that initiated by allogenic conduits (Allaire et
al. , 1997).
The transplantation of animal tissue into humans raises ethical and cul-
tural implications that must be discussed with the patient before these
conduits are employed (George, 2006). Implanting freshly harvested,
untreated allogenic and xenogenic grafts would require the use of immu-
nosuppressants to inhibit antigenicity and subsequent graft rejection.
Untreated scaffolds increase the risk of transferring diseases, such as bovine
spongiform encephalopathy (BSE) with the use of bovine-derived biologi-
cal tissue (Burg et al. , 2000; Sogal and Tofe, 1999). In addition, owing to
the natural process of degradation, these unprocessed vessels would rapidly
lose their integrity with potentially disastrous consequences once they are
implanted. Explanted scaffolds therefore require pre-treatment which will
not destabilise their composition but preserve most of their structural integ-
rity and inherent functionality once implanted (Gilbert et al. , 2006; Schmidt
and Baier, 2000).
￿ ￿ ￿ ￿ ￿
Search WWH ::




Custom Search