Abstract
Peripheral nerve injury treatment is a relevant problem because of nerve lesion high incidence and because of unsatisfactory regeneration after severe injuries, thus resulting in a reduced patient’s life quality. To repair severe nerve injuries characterized by substance loss and to improve the regeneration outcome at both motor and sensory level, different strategies have been investigated. Although autograft remains the gold standard technique, a growing number of research articles concerning nerve conduit use has been reported in the last years. Nerve conduits aim to overcome autograft disadvantages, but they must satisfy some requirements to be suitable for nerve repair. A universal ideal conduit does not exist, since conduit properties have to be evaluated case by case; nevertheless, because of their high biocompatibility and biodegradability, natural-based biomaterials have great potentiality to be used to produce nerve guides. Although they share many characteristics with synthetic biomaterials, natural-based biomaterials should also be preferable because of their extraction sources; indeed, these biomaterials are obtained from different renewable sources or food waste, thus reducing environmental impact and enhancing sustainability in comparison to synthetic ones. This review reports the strengths and weaknesses of natural-based biomaterials used for manufacturing peripheral nerve conduits, analyzing the interactions between natural-based biomaterials and biological environment. Particular attention was paid to the description of the preclinical outcome of nerve regeneration in injury repaired with the different natural-based conduits.
Highlights
Peripheral nerve repair outcome after an injury is often poor, it has been estimated that only 3% of patients recover sensibility while the motor function is recovered by less than 25% of patients (Houshyar et al, 2019).Peripheral nerve repair and the consequent recovery of sensory and/or motor function is a great challenge for both researchers in biomedical sciences and bioengineering, and for clinicians
- No in vitro toxicity. - Short term: higher number of activated Schwann cells in the distal segments of nerves regenerated through DAIII tubes. - Chitosan tubes with the different degrees of acetylation (DA) allowed good structural and functional sciatic nerve regeneration. - Differences with regard to the speed of their degradation: DAI no degradation after 3 months, DAIII faster degradation. - DAIII conduit showed a lower mechanical stability in comparison with the other experimental groups. - Nerves regenerated through DAI chitosan tubes revealed a significantly higher total number of myelinated axons as compared to the gold standard. - static sciatic index (SSI) and electrophysiology showed no differences between the experimental groups. - No differences in connective tissue thickness
Conduits obtained from natural-based biomaterials share many characteristics with synthetic ones, which are suitable for their use in peripheral nerve regeneration
Summary
Peripheral nerve repair outcome after an injury is often poor, it has been estimated that only 3% of patients recover sensibility while the motor function is recovered by less than 25% of patients (Houshyar et al, 2019). It is modifiable via chemical reactions [e.g., alginate dialdehyde formed by periodate oxidation of sodium alginate) (Dranseikiene et al, 2020) and physical crosslinking using Ca ions, maintaining a negligible inflammatory response (Sun and Tan, 2013)] This biomaterial can promote nerve regeneration but has a weak mechanical resistance, insufficient to bear physiological loading conditions and the high degradation rate justifies the use of alginate blended with other polymers (Hashimoto et al, 2002; Omidian et al, 2006; Kim and Kim, 2014; Shen and Hsieh, 2014; Golafshan et al, 2017), hybridized by incorporating nanofillers (Homaeigohar et al, 2019) or both (Chen et al, 2019). Experimental studies of nerve gaps longer than 10 mm repaired with chitosan tubes showed that chitosan conduit permits nerve regeneration, even if lower than those of nerve repaired through the autologous graft
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