Abstract
BackgroundSilicone tube (ST) conduits have been accepted as a therapeutic alternative to direct nerve suturing in the treatment of nerve injuries; however, the search for optimal adjuncts to maximize the outcomes is still ongoing. Frankincense (Fr) and graphene oxide (GO) have both been cited as neuroregenerative compounds in the literature. This study assesses the efficacy of these materials using a ST conduit in a rat facial nerve motor neuron axotomy model, distal to the stylomastoid foramen.MethodsAmmonia-functionalized graphene oxide (NH2-GO) and/or Fr extract were embedded in a collagen-chitosan hydrogel and were injected inside a ST. The ST was inserted in the gap between the axotomized nerve stumps. Return of function in eye closure, blinking reflex, and vibrissae movements were assessed and compared to control groups through 30 days following axotomy. To assess the histological properties of regenerated nerves, biopsies were harvested distal to the axotomy site and were visualized through light and fluorescence microscopy using LFB and anti-MBP marker, respectively.ResultsThere was no significant difference in behavioral test results between groups. Histological analysis of the nerve sections revealed increased number of regenerating axons and mean axon diameter in NH2-GO group and decreased myelin surface area in Fr group. Using both NH2-GO and Fr resulted in increased number of regenerated axons and myelin thickness compared to the hydrogel group.ConclusionsThe findings suggest a synergistic effect of the substances above in axon regrowth, notably in myelin regeneration, where Fr supposedly decreases myelin synthesis.
Highlights
Facial nerve (CN VII) paralysis, while not being lifethreatening, can be drastically disabling to the patients and profoundly impacting the psychosocial aspects of life [1]
Examination of the LFB-stained horizontal sections of nerve tissue (Fig. 3) showed decreased remyelination of axons in the Fr group compared to hydrogel group, Fig. 3 Luxol fast blue stained nerve cross-sections in different groups
The hydrogel control group and other experimental groups, showed increased regeneration compared to silicone tube controls
Summary
Facial nerve (CN VII) paralysis, while not being lifethreatening, can be drastically disabling to the patients and profoundly impacting the psychosocial aspects of life [1]. Despite the considerable advances of recent years and new microsurgical techniques proposed in the literature, facial nerve reconstruction remains a challenge for Aghajanian et al Inflammation and Regeneration (2021) 41:13 both biological and nonbiological conduits [7]. This study was conducted to assess the efficacy of novel adjuncts in hydrogels in regeneration and regrowth of motor neuron axons in a facial nerve axotomy model. Silicone rubber was chosen as the material of choice for the conduits in our model due to its accessibility, compatibility with short nerve gaps and along with a non-crosslinked collagen-chitosan-based hydrogel, the ability to be used as a template for a rudimentary assessment of the regenerative properties of the substances of interest in this study. This study assesses the efficacy of these materials using a ST conduit in a rat facial nerve motor neuron axotomy model, distal to the stylomastoid foramen
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