Biology Reference
In-Depth Information
YIGSR peptide, have been utilized to bridge a 15-mm rat sciatic nerve
gap. Histological and functional recovery analyses showed that while thio-
lation might have delayed nerve tissue regeneration, YIGSR peptides
enhanced nerve regeneration by promoting sprouting from the proximal
nerve stump and long-distance growth of regenerated axons throughout
the tube (
Itoh et al., 2005
). Moreover, a bilayered chitosan tube that com-
prised of an outer layer of a chitosan film and an inner layer of a nonwo-
ven chitosan nano-/microfiber mesh coated with the YIGSR peptide (in
which a glycin spacer has been introduced) has been successfully used to
bridge the 15-mm rat sciatic nerve gap (
Wang, Itoh, Matsuda, Aizawa,
et al., 2008
).
Chitosan has also been used in combination with collagen for nerve
repair. Collagen-blended chitosan nerve guides have been successfully tested
in vivo
in rats and enhanced both motor and sensory recoveries in compar-
ison with unblended nerve guides (
Patel et al., 2008a; Wei, Lao, & Gu,
2003
). Moreover, collagen-chitosan nerve guides promote and support axo-
nal sprouting, increase axon diameters and the area occupied by regenerated
axons, and further improve axonal maturation (
Patel et al., 2008b
).
Collagen-chitosan conduits, characterized by longitudinally orientated
microchannels, have also been shown to allow good nerve regeneration
and functional recovery across 15-mm-long rat sciatic nerve defects
(
Hu et al., 2009
). A summary of the different studies of chitosan combined
with adhesion molecules is reported in
Table 1.6
.
4.2. Chitosan conduits combined with cells for PNS repair
Directing SC migration by biomaterial substrates is receiving much atten-
tion in peripheral nerve tissue engineering (
Heath & Rutkowski, 1998
).
SCs secrete neurotrophic factors and express cell adhesion molecules that
enhance peripheral nerve regeneration (
Gravvanis et al., 2004; Heath &
Rutkowski, 1998; Ide, 1996
). They form an endoneurial sheath which acts
as a guide for axonal growth from the proximal to the distal nerve stumps.
They also play a role in clearing debris and creating an appropriate
milieu
for
nerve regrowth. Due to their role in nerve regeneration, the behavior of SCs
on a biomaterial used for nerve conduit fabrication is clearly a key issue
(
Guenard, Kleitman, Morrissey, Bunge, & Aebischer, 1992; Heath &
Rutkowski, 1998
) and it has been shown that SCs can be aligned by cultur-
ing them on biomaterial surface groves which provide micrometric dimen-
sions (
Hsu et al., 2007; Wang et al., 2009
).
