Biology Reference
In-Depth Information
4.3. Chitosan conduits combined with neurotrophic factors or
neuroprotective molecules for PNS repair
After an injury, one of the causes contributing to apoptosis and poor func-
tional recovery is the neurotrophic factor deprivation (
Ramer, Priestley, &
McMahon, 2000
). Nerve regeneration has been found to be enhanced by
utilizing guidance channels filled with neurotrophic factors, such as GDNF,
ciliary nerotrophic factor (CNTF), FGF-2, and NT-3 (
Grothe, Haastert, &
Jungnickel, 2006; Madduri, Feldman, Tervoort, Papaloizos, & Gander,
2010; Madduri, Papaloizos, & Gander, 2010; Oh et al., 2008; Pfister
et al., 2008; Yang et al., 2007
). Various types of nerve guides have been
developed by blending chitosan with different growth factors (
Table 1.8
).
Adding growth factors can support nerve regeneration by improving the
biological properties of a nerve guide. GDNF has been mixed to
chitosan-laminin conduits which have been used to bridge 10-mm rat sciatic
nerve gaps. GDNF-laminin-blended chitosan conduits increased functional
recovery and decreased muscle atrophy compared with unblended chitosan
conduits (
Patel et al., 2007
). Histologically, the GDNF-laminin-blended
chitosan conduits demonstrated at 6 weeks postsurgery regenerated axons
with higher axonal area and myelination in comparison with control con-
ditions. At 9-12 weeks postsurgery, however, control groups matched the
GDNF-laminin-blended chitosan group indicating that these kinds of con-
duits exert their positive effects during the initial stages of nerve regeneration
only (
Patel et al., 2009
).
In another study, CNTF-coated PLGA chitosan nerve conduit has been
utilized to repair 25-mm-long segments in the canine tibial nerve. Histolog-
ical results demonstrated that the PLGA/chitosan-CNTF conduits were
capable of guiding the damaged axons through the lesioned area, resulting
in good functional recovery close to the outcome in the nerve autograft
group (
Shen et al., 2010
).
Yet, also NGF has been immobilized onto biodegradable PDLLA/CS/
CHS nontoxic nerve conduits, resulting in good functional recovery after
bridging 10-mm defects in the rat sciatic nerve (
Xu et al., 2011
). Moreover,
chitosan conduit on which NGF was immobilized via genipin cross-linking
resulted in nerve reconstruction and muscle reinnervation in a 10-mm-long
sciatic nerve gap in rat (
Wang et al., 2012
).
Chitosan nerve conduits filled with heparin-incorporated fibrin-
fibronectin matrix for bFGF delivery have been successfully used to repair
sciatic nerve defects of 10-mm in adult rats (
Han et al., 2010
).
