Biomedical Engineering Reference
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native blood vessels since pulsatile flow was generated, which cre-
ated liquid movement inside of the scaffold. Unfortunately, most of
the compliance tests were performed with a simpler system due to
the lack of adequate equipment. However, our results indicate that
the results cannot recapitulate the conditions
in vivo
, which may
mislead evaluation of scaffold materials and development of novel
materials. Compliance is an important factor in designing scaffolds
for tissue-engineered, small-caliber vascular grafts since a compli-
ance mismatch is thought to affect prognosis. Such a mismatch may
cause neointimal hyperplasia at anastomotic sites, which, in turn,
can lead to thrombosis and occlusion even at early stages after
bypass surgery.
27
Weperformedratcarotidarterialreplacementusingelectrospun
scaffolds to evaluate their function
in vivo
. Grafts were patent for
12weeks,andnothrombusformationwasobserved.However,scaf-
foldmaterialsremained,andneitherthesmoothmusclelayer,which
is an important component of the vessel, nor regeneration of elas-
tic fibers was observed (Fig. 26.7). When biodegradable materials
Figure 26.7.
In vivo
findings of electrospun scaffolds (PCL). Rat carotid
arterial replacement was performed (a). The scaffold was removed 12
weeks after implantation. Grafts were in place for 12 weeks, and no throm-
bus formation was observed (d). Elastica van Gisson staining revealed that
collagen was growing in the scaffold wall, but there was little elastin in the
scaffold compared with native artery (b, e). Immunohistochemical staining
for factor VIII showed single-layered endothelial cells covering the inside
of the graft (c). However,
-smooth muscle actin staining revealed that the
smooth muscle layer, which is important for vascular strength, was not
regenerated (f). Scale bar
α
=
μ
μ
200
m (c and f) and 500
m (b and e). See
also ColorInsert.
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