Meta-Analysis Reveals Transcription Factor Upregulation in Cells of Injured Mouse Sciatic Nerve

Following peripheral nerve injury, transcription factors upregulated in the distal nerve play essential roles in Schwann cell reprogramming, fibroblast activation and immune cell function to create a permissive distal nerve environment for axonal regrowth. In this report, we first analysed four microarray data sets to identify transcription factors that have at least twofold upregulation in the mouse distal nerve stump at day 3 and day 7 post-injury. Next, we compared their relative mRNA levels through the analysis of an available bulk mRNA sequencing data set at day 5 post-injury. We then investigated the expression of identified TFs in analysed single-cell RNA sequencing data sets for the distal nerve at day 3 and day 9 post-injury. These analyses identified 55 transcription factors that have at least twofold upregulation in the distal nerve following mouse sciatic nerve injury. Expression profile for the identified 55 transcription factors in cells of the distal nerve stump was further analysed on the scRNA-seq data. Transcription factor network and functional analysis were performed in Schwann cells. We also validated the expression pattern of Jun, Junb, Runx1, Runx2, and Sox2 in the mouse distal nerve stump by immunostaining. The findings from our study not only could be used to understand the function of key transcription factors in peripheral nerve regeneration but also could be used to facilitate experimental design for future studies to investigate the function of individual TFs in peripheral nerve regeneration.

The Masseteric-Facial Anastomosis With Intratemporal Translocation of the Facial Nerve: Step-by-Step Technique and Results

BACKGROUND In the absence of a viable proximal nerve stump, damaged after surgical procedures around the skull base, numerous techniques for facial reanimation have been developed over time, aiming to restore baseline symmetry and active mimicry. OBJECTIVE To report experience using the masseteric nerve as a direct transfer to the facial nerve rerouted after intratemporal translocation. This paper illustrates the main steps of the technique and the quality of results. METHODS Eleven patients were treated with a masseteric direct transfer to the facial nerve. Its extratemporal rerouting toward the zygoma allowed tension-free coaptation between donor and recipient nerves. RESULTS Of the 11 patients, 8 had a good to excellent recovery, showing different patterns of time and scores, according to age, surgical timing, and masseteric nerve function quality. The return of activity in the frontalis muscle, never obtained after reinnervation via the hypoglossal nerve, is of particular interest. The quality of the smile can be improved with re-education and practice but remains under volitional control. A true emotional response is still lacking. CONCLUSION The masseteric nerve is an excellent alternative to the hypoglossal nerve and can reinnervate the whole territory of the facial nerve rerouted after intratemporal translocation. The overall results are remarkable, but the low quality of the trigeminal nerve, eventually affected by the first surgery, may be an important limitation. Even if the patients appear more at ease in re-education than with other techniques, a fully natural facial expression remains impossible to obtain.

Facial Nerve Reconstruction with Free Vascularized Composite Nerve Flap from Intrapetrous Portion to Terminal Branches—Case Report

The case presented here is a delayed reconstruction of a facial nerve defect after radical parotidectomy without a useful nerve stump at the stylomastoid foramen. A composite free flap was used to reconnect the nerve’s intrapetrous portion to the peripheral branches and reconstruct the soft-tissue deficit.

Covering the proximal nerve stump with chondroitin sulfate proteoglycans prevents traumatic painful neuroma formation by blocking axon regeneration after neurotomy in Sprague Dawley rats

OBJECTIVENeuropathic pain caused by traumatic neuromas is an extremely intractable clinical problem. Disorderly scar tissue accumulation and irregular and immature axon regeneration around the injury site mainly contribute to traumatic painful neuroma formation. Therefore, successfully preventing traumatic painful neuroma formation requires the effective inhibition of irregular axon regeneration and disorderly accumulation of scar tissue. Considering that chondroitin sulfate proteoglycans (CSPGs) can act on the growth cone and effectively inhibit axon regeneration, the authors designed and manufactured a CSPG-gelatin blocker to regulate the CSPGs’ spatial distribution artificially and applied it in a rat model after sciatic nerve neurectomy to evaluate its effects in preventing traumatic painful neuroma formation.METHODSSixty female Sprague Dawley rats were randomly divided into three groups (positive group: no covering; blank group: covering with gelatin blocker; and CSPG group: covering with the CSPG-gelatin blocker). Pain-related factors were evaluated 2 and 8 weeks postoperatively (n = 30). Neuroma growth, autotomy behavior, and histological features of the neuromas were assessed 8 weeks postoperatively (n = 30).RESULTSEight weeks postoperatively, typical bulb-shaped neuromas did not form in the CSPG group, and autotomy behavior was obviously better in the CSPG group (p < 0.01) than in the other two groups. Also, in the CSPG group the regenerated axons showed a lower density and more regular and improved myelination (p < 0.01). Additionally, the distribution and density of collagenous fibers and the expression of α–smooth muscle actin were significantly lower in the CSPG group than in the positive group (p < 0.01). Regarding pain-related factors, c-fos, substance P, interleukin (IL)–17, and IL-1β levels were significantly lower in the CSPG group than those in the positive and blank groups 2 weeks postoperatively (p < 0.05), while substance P and IL-17 remained lower in the CSPG group 8 weeks postoperatively (p < 0.05).CONCLUSIONSThe authors found that CSPGs loaded in a gelatin blocker can prevent traumatic neuroma formation and effectively relieve pain symptoms after sciatic nerve neurotomy by blocking irregular axon regeneration and disorderly collagenous fiber accumulation in the proximal nerve stump. These results indicate that covering the proximal nerve stump with CSPGs may be a new and promising strategy to prevent traumatic painful neuroma formation in the clinical setting.

Neurocap Use for the Treatment of Iatrogenic Neuropathic Pain: Preliminary Operative Results in 3 Patients

Painful neuromas are a devastating condition that is notoriously difficult to treat. The large number of techniques that have been attempted suggest that no one technique is superior. Neuromas often occur in the extremities, but iatrogenically caused pain in the head and neck area has also been described. This article describes 3 consecutive patients diagnosed with traumatic neuroma who underwent transection of the causative nerve, followed by capping of the nerve stump with a Neurocap. With a follow-up of 7 to 24 months, our results show a marked reduction in the pain scores of all 3 patients. The preliminary results indicate that this technique might be a viable treatment option for patients with a suspected neuroma in the head and neck area.

Nerve capping with a nerve conduit for the treatment of painful neuroma in the rat sciatic nerve

OBJECTIVETreatment of painful neuroma remains difficult, despite the availability of numerous surgical procedures. Recently, nerve capping treatment for painful neuroma using artificial nerve conduits has been introduced in clinical and basic research. However, the appropriate length of the nerve conduit and the pain relief mechanism have not been determined. In this study the authors aimed to investigate nerve capping treatment with a bioabsorbable nerve conduit using the rat sciatic nerve amputation model. Using histological analysis, the authors focused on the nerve conduit length and pain relief mechanism.METHODSSixteen Sprague Dawley rats were evaluated for neuropathic pain using an autotomy (self-amputation) score and gross and histological changes of the nerve stump 2, 4, 8, and 12 weeks after sciatic nerve neurectomy without capping. Forty-five rats were divided into 3 experimental groups, no capping (control; n = 15), capping with a 3-mm nerve conduit (n = 15), and capping with a 6-mm nerve conduit (n = 15). All rats were evaluated using an autotomy score and nerve stump histology 12 weeks after neurectomy. The nerve conduit was approximately 0.5 mm larger than the 1.5-mm diameter of the rat sciatic nerves to prevent nerve constriction.RESULTSThe autotomy scores gradually exacerbated with time. Without capping, a typical bulbous neuroma was formed due to random axonal regeneration 2 weeks after neurectomy. Subsequently, the adhesion surrounding the neuroma expanded over time for 12 weeks, and at the 12-week time point, the highest average autotomy scores were observed in the no-capping (control) group, followed by the 3- and the 6-mm nerve conduit groups. Histologically, the distal axonal fibers became thinner and terminated within the 6-mm nerve conduit, whereas they were elongated and protruded across the 3-mm nerve conduit. Minimal perineural scar formation was present around the terminated axonal fibers in the 6-mm nerve conduit group. Expressions of anti–α smooth muscle actin and anti–sigma-1 receptor antibodies in the nerve stump significantly decreased in the 6-mm nerve conduit group.CONCLUSIONSIn the rat sciatic nerve amputation model, nerve capping treatment with a bioabsorbable nerve conduit provided relief from neuroma-induced neuropathic pain and prevented perineural scar formation and neuroinflammation around the nerve stump. The appropriate nerve conduit length was determined to be more than 4 times the diameter of the original nerve.

Using the Post-Descendens Hypoglossal Nerve in Hypoglossal-Facial Anastomosis: An Anatomic and Histologic Feasibility Study

BACKGROUND Hypoglossal-facial anastomosis (HFA) is a popular facial reanimation technique. Mobilizing the intratemporal segment of the facial nerve and using the post-descendens hypoglossal nerve (ie, the segment distal to the take-off of descendens hypoglossi) have been proposed to improve results. However, no anatomic study has verified the feasibility of this technique. OBJECTIVE To assess the anatomic feasibility of HFA and the structural compatibility between the 2 nerves when the intratemporal facial and post-descendens hypoglossal nerves are used. METHODS The facial and hypoglossal nerves were exposed bilaterally in 10 sides of 5 cadaveric heads. The feasibility of a side-to-end (ie, partial end-to-end) HFA with partial sectioning of the post-descendens hypoglossal nerve and the mobilized intratemporal facial nerve was assessed. The axonal count and cross-sectional area of the facial and hypoglossal nerves at the point of anastomosis were assessed. RESULTS The HFA was feasible in all specimens with a mean (standard deviation) 9.3 (5.5) mm of extra length on the facial nerve. The axonal counts and cross-sectional areas of the hypoglossal and facial nerves matched well. Considering the reduction in the facial nerve cross-sectional area after paralysis, the post-descendens hypoglossal nerve can provide adequate axonal count and area to accommodate the facial nerve stump. CONCLUSION Using the post-descendens hypoglossal nerve for side-to-end anastomosis with the mobilized intratemporal facial nerve is anatomically feasible and provides adequate axonal count for facial reanimation. When compared with use of the pre-descendens hypoglossal nerve, this technique preserves C1 fibers and has a potential to reduce glottic complications.

LONG-TERM OUTCOMES OF RAT SCIATIC NERVE INJURY AND ITS GRAFTING WITH SILICON WIRES-BASED CONDUIT: DISTAL NERVE STUMP HISTOLOGY AND ELECTROMYOGRAPHY RESULTS

Relevance. The investigations on trauma epidemiology have shown that both combat- and noncombat-related extremity injuries are often accompanied by nerve injuries. These injuries disproportionately affect young healthy civilians and military officers and has a devastating impact on a patients’ quality of life. Severe nerve injuries, such as nerve trunk injury in continuity (Sunderland 5), that cannot be treated by neurorraphy without tension, require use of nerve gap bridging strategies with different materials and techniques. Objective. This study was aimed to evaluate any positive or negative impact of implanted silicon wires on the quality of nerve fibers at distal nerve stump. Materials and Methods. An experiment was performed on 40 male Whistar rats 2-4 month that were divided to the next groups: I, (n=10) sham-operated, only surgical access to sciatic nerve was performed. II (n=10) with 10 mm sciatic nerve gap that was bridged with autoneurografting. III (n=10) with 10 mm nerve gap that was bridged with allogenic decell aorta filled with 4% carboxymethylcellulose hydrogel. IV (n=10) with 10 mm nerve gap that was bridged with allogenic decell aorta filled with 4% carboxymethylcellulose hydrogel and aligned p-type silicon microvires. Decellularization of allogenic aortas was performed by freeze-thaw cycles. Silicon whiskers were fabricated by Vapor-Liquid-Solid (VLS) method in a cold wall Catalytic Chemical Vapor Deposition (Cat-CVD) chamber, pre-cleaned with hydrofluoric acid and sterilized via 180*C dry heat. 12 weeks after surgery under general anesthesia all rats underwent invasive needle electroneurpmyography with proximal nerve stump stimulation and registration from gastrocnemius muscle. Myograms were recorded and compared by the shape of M-reflex and its amplitude. After myography rats were euthanized under thiopentone overdosage and distal stumps of injured sciatic nerves were harvested for light microscopy. Sciatic nerve transverse slices were stained with nitric silver by modified Bielschowsky method Nerve fiber diameter, axon diameter, myelin sheath thickness and axon-to-nerve fiber diameter ratio (g-ratio) were measured. Results. Performed analysis showed that rats from ІІ and IV groups demonstrated the best quality of nerve fibers in distal nerve stump. That was evidenced by bigger nerve fibers diameter in rats from autologous nerve grafting group and aorta with gel and wires grafting group in comparison with aorta with gel grafting group. Rats from IV demonstrated higher voltage and lower latency of M-reflexes during electromyography. Conclusions. It can be concluded about the possible pro-regenerative impact of implanted silicon wires that was evidenced by better nerve fibers quality at distal nerve stump.