Biology Reference
In-Depth Information
Interestingly, a couple of studies showed that chitooligosaccharides
(COSs), the biodegradation products of chitosan, promote peripheral nerve
regeneration and functional recovery in the rat sciatic nerve crush injury
model and rabbit common peroneal nerve crush injury model, suggesting
their potential application in peripheral nerve repair as neuroprotective
agents (
Gong et al., 2009; Jiang et al., 2009
).
Moreover, immunophilin FK506 combined with biodegradable
chitosan guide provides neurotrophic and neuroprotective actions, promot-
ing nerve regeneration in a rat sciatic nerve defect model (
Li et al., 2010
).
Also neurosteroids, such as progesterone (PROG) and pregnenolone
(PREG), have been used for potentiating conduit nerve repair as these hor-
mones are synthesized by SCs (
Baulieu & Schumacher, 2000
) and induce
myelination binding on intracellular receptors which activate the synthesis
of myelin protein P0 and PMP22 (
Desarnaud et al., 1998; Jung-Testas,
Schumacher, Robel, & Baulieu, 1996
). Furthermore, neurite outgrowth
may be stimulated by a PROG metabolite (5-
a
-tetrahydroprogesterone)
through GABA(A) receptors (
Guennoun et al., 2001; Koenig, Gong, &
Pelissier, 2000
). Chitosan conduits have been used to deliver PROG into
a 10-mm rabbit facial nerve gap model. The released PROG promoted
nerve regeneration to a high degree so that at 45 days postsurgery myelinated
fibers were observed both in the proximal and distal nerve stumps (
Chavez-
Delgado et al., 2003
). Similar results have been reported using axotomized
dog sciatic nerve injured model (
Rosales-Cortes, Peregrina-Sandoval,
Banuelos-Pineda, Castellanos-Martinez, et al., 2003
). Chitosan tubes deliv-
ering a combination of PROG and PREG have also been tested. Fifteen
days postsurgery, the regenerating tissue contained SCs holding non-
myelinated fibers, whereas at 45 days postsurgery, the regenerating tissue
displayed myelinated fibers of different shape, size, and myelin sheath thick-
ness (
Chavez-Delgado et al., 2005
). These findings indicate that chitosan
conduits allows regeneration of nerve fibers and that long-time release of
neurosteroid from the conduits induces faster regeneration.
5. CONCLUSION
Among the many different types of biomaterials that have been pro-
posed as optimal candidates for neural repair scaffolds, chitosan has been
receiving growing interests among basic and clinical scientists. In this
review, we have overviewed the more relevant articles demonstrating that
this biomimetic material exerts a positive effect on cell cultures of both
