Enhancement of peripheral nerve regeneration

Electrophysiological and histopathological evaluation of the effectiveness of melatonin and glatiramer acetate for traumatic facial nerve injuries

AIM

This study aimed to evaluate the effect of systemic/local use of melatonin and glatiramer acetate on regeneration in traumatic nerve injury models.

MATERIALS AND METHODS

A total of 42 male Wistar albino rats were randomly divided into 6 groups: healthy control (Group 1), injured control (Group 2), local melatonin (Group 3), systemic melatonin (Group 4), local glatiramer acetate (Group 5), and systemic glatiramer acetate (Group 6). In all groups, electromyography recordings of the facial nerve were obtained after surgery and before sacrifice, and the damaged nerve region was histopathologically examined after sacrifice.

RESULTS

In the electrophysiological evaluation, the control group had the greatest decrease in amplitude and extension in latency time following surgery than the treatment groups. Furthermore, a significant decrease in the degenerative axon count, edematous areas, and fibrotic areas as well as a significant increase in axonal surface areas was observed in all the treatment groups compared with the damage control group.

CONCLUSIONS

Although both glatiramer acetate and melatonin are beneficial in regeneration in traumatic facial nerve injuries, it can be concluded that systemic use of melatonin can yield more positive results than glatiramer acetate and local use of both two drugs.

Thoracodorsal to long thoracic nerve transfer in a patient with traumatic injury: A case report

Background

Traumatic injury to the long thoracic nerve causes paralysis of the serratus muscle, clinically expressed as winged scapula and functional impairment of the shoulder girdle. Treatment varies according to the severity of the injury, with a focus on early intervention for best results; however, the therapeutic approach remains a challenge at present.

Case Description

We present the case of a 32-year-old male patient, athlete, right-handed, presented with bilateral paresis predominantly in the right arm, associated with paresthesia and changes in the coloring of the upper limbs. After being diagnosed with Thoracic Outlet Syndrome and undergoing surgery, vascular symptoms persisted with a significant loss of strength in the right shoulder. Winged scapula was observed and structural lesions were excluded on magnetic resonance imaging. Electromyographic studies confirmed the presumption of traumatic nerve involvement of the long thoracic nerve. Notwithstanding 6 months of physical therapy, there was no improvement, so a nerve transfer from the thoracodorsal nerve to the right long thoracic nerve was chosen. At 12 months, complete resolution of the winged scapula and functional recovery were observed. The patient also experienced a decrease in preoperative pain from 5/10 to 2/10 on the visual analog scale.

Conclusion

Nerve transfer from the thoracodorsal nerve to the long thoracic nerve is a safe and effective technique to treat winged scapula due to long thoracic nerve injury.

Potential of dental pulp stem cells and their products in promoting peripheral nerve regeneration and their future applications

Peripheral nerve injury (PNI) seriously affects people's quality of life. Stem cell therapy is considered a promising new option for the clinical treatment of PNI. Dental stem cells, particularly dental pulp stem cells (DPSCs), are adult pluripotent stem cells derived from the neuroectoderm. DPSCs have significant potential in the field of neural tissue engineering due to their numerous advantages, such as easy isolation, multidifferentiation potential, low immunogenicity, and low transplant rejection rate. DPSCs are extensively used in tissue engineering and regenerative medicine, including for the treatment of sciatic nerve injury, facial nerve injury, spinal cord injury, and other neurodegenerative diseases. This article reviews research related to DPSCs and their advantages in treating PNI, aiming to summarize the therapeutic potential of DPSCs for PNI and the underlying mechanisms and providing valuable guidance and a foundation for future research.

Remodeling of Neuromuscular Junctions in Target Muscle Following Nerve Regeneration in Mice After Delayed Peripheral Nerve Repair

Peripheral nerve injury (PNI) induces severe functional loss in extremities. Progressive denervation and atrophy occur in the muscles if the nerve repair is delayed for long periods of the time. To overcome these difficulties, detailed mechanisms should be determined for neuromuscular junction (NMJ) degeneration in target muscles after PNI and regeneration after nerve repair. We established two models of end-to-end neurorrhaphy and allogeneic nerve grafting in the chronic phase after common peroneal nerve injury in female mice (n = 100 in total). We evaluated motor function, histology, and gene expression in the target muscles during their regeneration processes and compared the models. We found that the functional recovery with allogeneic nerve grafting was superior to that with end-to-end neurorrhaphy, and the number of reinnervated NMJs and Schwann cells was increased at 12 weeks after allograft. In addition, NMJ- and Schwann cell-related molecules showed high expression in the target muscle in the allograft model. These results suggest that Schwann cell migrating from the allograft might play a crucial role in nerve regeneration in the chronic phase after PNI. The relationship between the NMJ and Schwann cells should be further investigated in the target muscle.

Regeneration of sensory nerve branches in extraction socket and surrounding alveolar bone in rat: immunohistochemical observation of the axon and myelin sheath changes

The purpose of this study was to investigate the process and derivation of the distribution of the sensory nerves that appear in the extraction socket and surrounding alveolar bone following tooth extraction. The right mandibular first molar of rats and periodontal ligament were extracted as a single mass, and the mandible was harvested after days 1, 3, 5, and 7 after extraction. Serial sections of 7 µm thickness were prepared for the proximal root (Section A), buccolingual root (Section B), and centrifugal root (Section C) of the first molar. H–E staining and immunohistochemical staining with anti-S100 antibody and anti-NF-L antibody were carried out. The presence of nerve fiber bundles in the blood clot was already evident on post-extraction day 3, and on post-extraction day 7. On day 3, the number of axons in Sections B and C had greatly decreased, indicating that, after extraction, the connection between peripheral nerve tissue and the trigeminal ganglion was temporarily markedly reduced in the region of the alveolar branch. Although the myelin sheaths were regenerating on day 5, the majority of the axons of the alveolar branches extending from the inferior alveolar nerve were seen to be extremely thin and scattered, despite their further regeneration. The above results suggest that the newly myelinated nerves are actually derived from the bone marrow to the extraction socket, so few nerves, rather than being derived from the alveolar branches that had innervated the extracted tooth.

Optic nerve injury models under varying forces

PURPOSE

To explore the pathological changes in optic nerve injury models under varying forces.

METHODS

The rats were classified into 4 groups: sham operation (SH), 0.1, 0.3, and 0.5 N. Modeling was performed using the lateral optic nerve pulling method. Seven days after modeling, Brn3a immunofluorescence was used to detect retinal ganglion cell (RGC) number, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to detect RGC apoptosis, and flash visual evoked potential (FVEP) was used to detect the optic nerve function on days 1, 3, and 7 after modeling. In addition, LC3 II and P62 expression levels in retinal tissues were detected by western blotting to observe the changes in autophagy levels.

RESULTS

RGC number decreased 7 d after modeling, and it showed a downward trend with increasing damaging force. The number of apoptotic RGCs in ganglion cell layer in the 0.3 and 0.5 N groups was increased and was higher than that in the 0.1 N group. The difference in FVEP of rats in each group was mainly reflected in the P2 peak latency. LC3 II and P62 expression levels in retinal tissue of 0.3 and 0.5 N groups were higher than those of the SH and 0.1 groups; however, the difference between the 0.1 N and SH groups was not statistically significant.

CONCLUSION

Precisely controlling the force of the optic nerve clamping injury model is necessary because different forces acting on the optic nerve will lead to differences in the loss of optic neurons, the conduction function of the optic nerve, and autophagy level in retinal tissues.

Nanoparticles for neurotrophic factor delivery in nerve guidance conduits for peripheral nerve repair

Peripheral nerve injuries are a major source of disabilities, and treatment of long nerve gap autografts is the gold standard. However, due to poor availability and donor-site morbidity, research is directed towards the development of regenerative strategies based on the use of artificial nerve guidance conduits (NGCs). Several properties and characteristics of the NGCs can be fine-tuned, such as the architecture of the conduit, the surface topography and the addition of bioactive molecules and cells to speed up nerve regeneration. In this review, US FDA-approved NGCs are described. The recent works, in which polymeric, magnetic, silica-based and lipidic NPs are employed to introduce growth factors (GFs) to NGCs, are overviewed and discussed in depth herein.

Effects of Adipose-Derived Mesenchymal Stem Cells and Human Amniotic Membrane on Sciatic Nerve Repair in Rats

Background: Peripheral nerve injuries remain a great challenge for microsurgery despite the significant progress in recent decades. The current gold standard is autogenous nerve grafting with a success rate as low as 50% in long gaps. Current studies have focused on finding alternative methods for bridging nerve defects. Previous data have demonstrated the role of human amniotic membrane in stimulating neural regeneration. On the other hand, adipose-derived mesenchymal stem cells can differentiate into all three germ layers and could support nerve repair. The purpose of this study was to compare the role of the human amniotic membrane with and without adipose tissue stem cells in sciatic nerve injury with gap in rats. Objectives: We aimed to evaluate the effectiveness of the human amniotic membrane with and without adipose-derived mesenchymal stem cells in sciatic nerve injury with gap in rats. Methods: Twenty-four male Wistar rats in four random groups were used in our study. In the first group, the nerve gap was repaired using the inverse resected nerve segment (Control group), the second group was repaired with a human amniotic membrane (AM group), the third group was repaired with an amnion sheet with seeded adipose-derived mesenchymal stem cells (AM/ADMSCs group), and the last group was not repaired, and both stumps were sutured to muscles. Results: All the animals underwent the procedures and survived without complication. The sciatic function index and hot plate test results were significantly improved in the AM and AM/ADMSCs groups compared to the Control group (as a gold standard of care) (P>0.05). Based on histopathology findings, regenerative nerve fibers were seen in the implanted area of both AM and AM/ADMSCs groups; however, nerve fibers were surrounded by significant fibrosis (scar formation) in the AM/ADMSCs group. The axon count in the Control group was significantly higher than both experimental groups (P < 0.01). Conclusions: Our study showed the role of amniotic membrane in the promotion of nerve regeneration in sciatic nerve injury with a gap, but adding adipose-derived mesenchymal stem cells not only has no extra benefits, but also causes more tissue scar.

Dynamic Environmental Physical Cues Activate Mechanosensitive Responses in the Repair Schwann Cell Phenotype

Schwann cells plastically change in response to nerve injury to become a newly reconfigured repair phenotype. This cell is equipped to sense and interact with the evolving and unusual physical conditions characterizing the injured nerve environment and activate intracellular adaptive reprogramming as a consequence of external stimuli. Summarizing the literature contributions on this matter, this review is aimed at highlighting the importance of the environmental cues of the regenerating nerve as key factors to induce morphological and functional changes in the Schwann cell population. We identified four different microenvironments characterized by physical cues the Schwann cells sense via interposition of the extracellular matrix. We discussed how the physical cues of the microenvironment initiate changes in Schwann cell behavior, from wrapping the axon to becoming a multifunctional denervated repair cell and back to reestablishing contact with regenerated axons.

Overview of the short- and long-term quantitative outcomes following end-to-side neurorrhaphy in a rat model

The time course of events following end-to-side nerve coaptation remains unclear. Re-innervation and effects on the donor nerve were assessed following short- and long-term end-to-side neurorrhaphy were investigated in a rat model. One hundred and our Sprague-Dawley female rats were randomized to fresh and pre degenerated repair groups with or without perineurotomy. The right peroneal nerve was sutured to the tibial nerve in an end-to-side manner. Histological and electro-physiological assessment of re-innervation and of the donor nerve was performed at two-three months and at nine-twelve months, post-operatively. The results demonstrated that end-to-side neurorrhaphy could attract axonal sprouts and successfully re-innervate the target muscles. The influence on donor nerve was minimal in late stages, although it did have early negative effect. Double labeling provided evidence that one of the mechanisms of this procedure is probably by collateral sprouting.

Bioprinting: From Tissue and Organ Development to in Vitro Models

Bioprinting techniques have been flourishing in the field of biofabrication with pronounced and exponential developments in the past years. Novel biomaterial inks used for the formation of bioinks have been developed, allowing the manufacturing of in vitro models and implants tested preclinically with a certain degree of success. Furthermore, incredible advances in cell biology, namely, in pluripotent stem cells, have also contributed to the latest milestones where more relevant tissues or organ-like constructs with a certain degree of functionality can already be obtained. These incredible strides have been possible with a multitude of multidisciplinary teams around the world, working to make bioprinted tissues and organs more relevant and functional. Yet, there is still a long way to go until these biofabricated constructs will be able to reach the clinics. In this review, we summarize the main bioprinting activities linking them to tissue and organ development and physiology. Most bioprinting approaches focus on mimicking fully matured tissues. Future bioprinting strategies might pursue earlier developmental stages of tissues and organs. The continuous convergence of the experts in the fields of material sciences, cell biology, engineering, and many other disciplines will gradually allow us to overcome the barriers identified on the demanding path toward manufacturing and adoption of tissue and organ replacements.

Plasticity of Unmyelinated Fibers in a Side-to-end Tubulization Model

BACKGROUND

Histomorphometric studies of unmyelinated fibers of the rat fibular nerves are uncommon, and side-to-end neurorrhaphy studies using the fibular nerve investigate primarily motor fibers. We investigated side-to-end tubulization (SET) technique, in which occurs collateral sprouting from the intact donor nerve fibers to the distal stump of receptor nerve, with muscle reinnervation and functional rehabilitation, to assess whether there is a successful growth of unmyelinated fibers in this model.

METHODS

Adult Wistar rats fibular nerves were sectioned to create a 5-mm gap. A 6-mm silicone tube was attached between a side of the intact tibial nerve and the sectioned fibular nerve distal stump (SET group), with the left fibular nerve as normal (sham group). Seventy days postsurgery, unmyelinated fibers from the distal segment of the fibular nerve were quantified using light and transmission electron microscopy and their diameters were measured.

RESULTS

The number of unmyelinated fibers was similar between sham (1,882 ± 270.9) and SET (2,012 ± 1,060.8), but axons density was significantly greater in the SET (18,733.3 ± 5,668.6) than sham (13,935.0 ± 1,875.8). Additionally, the axonal diameters differed significantly between groups with mean measures in sham (0.968 ± 0.10) > SET (0.648 ± 0.08).

CONCLUSIONS

Unmyelinated fiber growth occurred even with a 5-mm distance between the donor and receptor nerves, reaching similar axonal number to the normal nerve, demonstrating that the SET is a reliable technique that can promote a remarkable plasticity of unmyelinated axons.

Innervation of an engineered muscle graft for reconstruction of muscle defects

Autologous muscle flaps are commonly used to reconstruct defects that involve muscle impairment. To maintain viability and functionality of these flaps, they must be properly vascularized and innervated. Tissue-engineered muscles could potentially replace autologous muscle tissue, but still require establishment of sufficient innervation to ensure functionality. In this study, we explored the possibility of innervating engineered muscle grafts transplanted to an abdominal wall defect in mice, by transferring the native femoral nerve to the graft. Six weeks posttransplantation, nerve conduction studies and electromyography demonstrated increased innervation in engineered grafts neurotized with the femoral nerve, as compared to non-neurotized grafts. Histologic assessments revealed axonal penetration and formation of neuromuscular junctions within the grafts. The innervation process described here may advance the fabrication of a fully functional engineered muscle graft that will be of utility in clinical settings.

Synthetic bioresorbable poly-α-hydroxyesters as peripheral nerve guidance conduits; a review of material properties, design strategies and their efficacy to date

Implantable tubular devices known as nerve guidance conduits (NGCs) have drawn considerable interest as an alternative to autografting in the repair of peripheral nerve injuries.

Biomimetic Architectures for Peripheral Nerve Repair: A Review of Biofabrication Strategies

Biofabrication techniques have endeavored to improve the regeneration of the peripheral nervous system (PNS), but nothing has surpassed the performance of current clinical practices. However, these current approaches have intrinsic limitations that compromise patient care. The "gold standard" autograft provides the best outcomes but requires suitable donor material, while implantable hollow nerve guide conduits (NGCs) can only repair small nerve defects. This review places emphasis on approaches that create structural cues within a hollow NGC lumen in order to match or exceed the regenerative performance of the autograft. An overview of the PNS and nerve regeneration is provided. This is followed by an assessment of reported devices, divided into three major categories: isotropic hydrogel fillers, acting as unstructured interluminal support for regenerating nerves; fibrous interluminal fillers, presenting neurites with topographical guidance within the lumen; and patterned interluminal scaffolds, providing 3D support for nerve growth via structures that mimic native PNS tissue. Also presented is a critical framework to evaluate the impact of reported outcomes. While a universal and versatile nerve repair strategy remains elusive, outlined here is a roadmap of past, present, and emerging fabrication techniques to inform and motivate new developments in the field of peripheral nerve regeneration.

Decellularized sciatic nerve matrix as a biodegradable conduit for peripheral nerve regeneration

The use of autologous nerve grafts remains the gold standard for treating nerve defects, but current nerve repair techniques are limited by donor tissue availability and morbidity associated with tissue loss. Recently, the use of conduits in nerve injury repair, made possible by tissue engineering, has shown therapeutic potential. We manufactured a biodegradable, collagen-based nerve conduit containing decellularized sciatic nerve matrix and compared this with a silicone conduit for peripheral nerve regeneration using a rat model. The collagen-based conduit contains nerve growth factor, brain-derived neurotrophic factor, and laminin, as demonstrated by enzyme-linked immunosorbent assay. Scanning electron microscopy images showed that the collagen-based conduit had an outer wall to prevent scar tissue infiltration and a porous inner structure to allow axonal growth. Rats that were implanted with the collagen-based conduit to bridge a sciatic nerve defect experienced significantly improved motor and sensory nerve functions and greatly enhanced nerve regeneration compared with rats in the sham control group and the silicone conduit group. Our results suggest that the biodegradable collagen-based nerve conduit is more effective for peripheral nerve regeneration than the silicone conduit.

A Novel Model for Acute Peripheral Nerve Injury in the Horse and Evaluation of the Effect of Mesenchymal Stromal Cells Applied In Situ on Nerve Regeneration: A Preliminary Study

Transplantation of mesenchymal stromal cells (MSCs) to sites of experimentally created nerve injury in laboratory animals has shown promising results in restoring nerve function. This approach for nerve regeneration has not been reported in horses. In this study, we first evaluated the in vitro ability of equine bone marrow-derived MSCs (EBM-MSCs) to trans-differentiate into Schwann-like cells and subsequently tested the MSCs in vivo for their potential to regenerate a transected nerve after implantation. The EBM-MSCs from three equine donors were differentiated into SCLs for 7 days, in vitro, in the presence of specialized differentiation medium and evaluated for morphological characteristics, by using confocal microscopy, and for protein characteristics, by using selected Schwann cell markers (GFAP and S100b). The EBM-MSCs were then implanted into the fascia surrounding the ramus communicans of one fore limb of three healthy horses after a portion of this nerve was excised. The excised portion of the nerve was examined histologically at the time of transection, and stumps of the nerve were examined histologically at day 45 after transplantation. The EBM-MSCs from all donors demonstrated morphological and protein characteristics of those of Schwann cells 7 days after differentiation. Nerves implanted with EBM-MSCs after nerve transection did not show evidence of nerve regeneration at day 45. Examination of peripheral nerves collected 45 days after injury and stem cell treatment revealed no histological differences between nerves treated with MSCs and those treated with isotonic saline solution (controls). The optimal delivery of MSCs and the model suitable to study the efficacy of MSCs in nerve regeneration should be investigated.

Peripheral Facial Nerve Regeneration Using Collagen Conduit Entubulation in a Cat Model

Objectives:

Facial nerve (FN) injuries are functionally, psychologically, and financially debilitating. Facial nerve autograft repairs produce significant donor nerve morbidity and functional results that rarely exceed House-Brackmann (HB) grade III over VI. In this study we sought to enhance FN regeneration via collagen conduit entubulation.

Methods:

Five control cats underwent right (“cut-side”) FN transection and immediate microsurgical anastomosis repair. Five experimental cats underwent identical repairs plus collagen conduit entubulation of each anastomosis.

Results:

Postoperative behavioral observations revealed gradual FN functional recovery in all cats, who attained adapted HB grades of II to III over VI after 6 weeks. Electromyographic latencies and amplitudes from the bilateral orbicularis oculi and orbicularis oris muscles indicated restoration of FN continuity in all 10 cats. In comparison with FN repairs without conduits, repairs with conduits significantly enhanced recovery of amplitude in cut-side orbicularis oculi muscles (p = .037) and latency in cut-side orbicularis oris muscles (p = .048). In comparison with intact left (“uncut-side”) FN latencies and amplitudes, more statistically significant differences in cut-side FN function were observed in repairs without conduits than in repairs with conduits. Conduits therefore facilitated a more complete return of electrophysiological function. Histologic analyses confirmed FN continuity and revealed more organized FN regenerative architecture in conduit-implanted repairs.

Conclusions:

The overall results support enhanced FN regeneration with collagen conduit entubulation.

Nonexpanded Adipose Stromal Vascular Fraction Local Therapy on Peripheral Nerve Regeneration Using Allografts

AIM OF THE STUDY

Adipose tissue possesses a population of multi-potent stem cells which can be differentiated to a Schwann cell phenotype and may be of benefit for treatment of peripheral nerve injuries. Effects of local therapy of nonexpanded adipose stromal vascular fraction (SVF) on peripheral nerve regeneration was studied using allografts in a rat sciatic nerve model.

MATERIALS AND METHODS

Thirty male white Wistar rats were divided into three experimental groups (n = 10), randomly: Sham-operated group (SHAM), allograft group (ALLO), SVF-treated group (ALLO/SVF). In SHAM group left sciatic nerve was exposed through a gluteal muscle incision and after homeostasis muscle was sutured. In the ALLO group the left sciatic nerve was exposed through a gluteal muscle incision and transected proximal to the tibio-peroneal bifurcation where a 10 mm segment was excised. The same procedure was performed in the ALLO/SVF group. The harvested nerves of the rats of ALLO group were served as allograft for ALLO/SVF group and vice versa. The SHAM and ALLO groups received 100 μL phosphate buffered saline and the ALLO/SVF group received 100 μL SVF (2.25 ± 0.45 × 10(7) cells) locally where the grafting was performed.

RESULTS

Behavioral, functional, biomechanical, and gastrocnemius muscle mass showed earlier regeneration of axons in ALLO/SVF than in ALLO group (p < .05). Histomorphometic and immunohistochemical studies also showed earlier regeneration of axons in ALLO/SVF than in ALLO group (p < .05).

CONCLUSIONS

Administration of nonexpanded SVF could accelerate functional recovery after nerve allografting in sciatic nerve. It may have clinical implications for the surgical management of patients after nerve transection.

Influence of insulin-like growth factor I on nerve regeneration using allografts: a sciatic nerve model

Effects of insulin-like growth factor I (IGF I) on peripheral nerve regeneration was studied using allografts in a rat sciatic nerve model. Thirty male white Wistar rats were divided into 3 experimental groups (n = 10) randomly: normal control group (NC), allograft group (ALLO), and IGF I-treated group (ALLO/IGF). In the NC group, the left sciatic nerve was exposed through a gluteal muscle incision and, after homeostasis, the muscle was sutured. In the ALLO group, the left sciatic nerve was exposed through a gluteal muscle incision and transected proximal to the tibioperoneal bifurcation where a 10-mm segment was excised. The same procedure was performed in the ALLO/IGF group. The harvested nerves of the rats of the ALLO group were served as allograft for the ALLO/IGF group and vice versa. The NC and ALLO groups received 10 μL of sterile phosphate buffered saline intraperitoneally once a day for 1 week, and the ALLO/IGF group received 10 μL of IGF I (100 ng/kg per day) intraperitoneally once a day for 1 week. Behavioral testing, sciatic nerve functional study and the gastrocnemius muscle mass showed earlier regeneration of axons in the ALLO/IGF group than in the ALLO group (P < 0.05). Administration of IGF I could accelerate functional recovery after nerve allografting in the sciatic nerve and may have clinical implications for the surgical management of patients after facial nerve transection.

Minced nerve tissue in vein grafts used as conduits in rat tibial nerves

INTRODUCTION

Peripheral nerve injuries are encountered frequently in clinical practice. In nerve repair, an end-to-end suture is the preferable choice of treatment. However, where primary closure is not possible, the defect is to be repaired with a nerve graft.

METHODS

A total of 21 female Wistar rats weighing 230 to 290 g were used in the study. They were classified into the following 3 groups: (I) nerve graft, (II) vein graft, and (III) minced nerve graft. In group I, after exposure of the tibial nerve, a 1-cm-long nerve gap was created on the tibial nerve, and the defect was repaired epineurally by using the autogenous nerve. In group II, the 1-cm tibial nerve defect was repaired by using an autogenous vein graft. In group III, a 1-cm nerve graft was divided to 3 equal parts, with one of the nerve parts being minced with microscissors and placed in the vein graft lumen. Thereafter, a 1-cm tibial nerve defect was repaired by the vein graft filled with minced nerve tissue. The tibial function indices (TFIs) were calculated for functional assessment using the Bain-Mackinnon-Hunter formula. Light and electron microscopic evaluations were performed for morphometric assessment. In addition, the myelinated fibers were counted in all groups.

RESULTS

The TFIs of group II were found to be the lowest among all the groups after the sixth week, whereas the TFI of group I was found to be better than the other groups after the sixth week. There was no difference in TFIs between group I and group III. On the basis of the number of myelinated fibers, there was no statistically significant difference between group I and group III, whereas the difference was significant (P<0.05) between groups I/III and group II. Presence of peripheral nerves in light microscopic evaluation revealed normal characteristics of myelinated fibers in all groups. The myelinated axon profile was near normal in the nerve graft group in electron microscopic evaluation. However, there were more degenerated axons with disturbed contours and vacuolizations in the vein graft group compared to the minced nerve graft group.

CONCLUSIONS

We can conclude that using minced nerve tissue in vein grafts as a conduit increases the regeneration of nerves (almost like the nerve graft group) and it may not be caused by donor-site morbidity. It can be used in the repair of nerve defects instead of autogenous nerve grafts after further experimental evidence and clinical trials.

Comparison of results between chitosan hollow tube and autologous nerve graft in reconstruction of peripheral nerve defect: An experimental study

OBJECT

This study evaluated a chitosan tube for regeneration of the injured peripheral nerve in a rodent transected sciatic nerve model in comparison to autologous nerve graft repair.

METHODS

Chitosan hollow tube was used to bridge a 10-mm gap between the proximal and distal ends in 11 rats. In the control group, an end-to-end coaptation of 10-mm long autologous nerve graft was performed in 10 rats for nerve reconstruction.

RESULTS

SFI showed an insignificant advantage to the autologous group both at 30 days (P = 0.177) and at 90 days post procedure (P = 0.486). Somato-sensory evoked potentials (SSEP) and compound muscle action potentials (CMAP) tests showed similar results between chitosan tube (group 1) and autologous (group 2) groups with no statistically significant differences. Both groups presented the same pattern of recovery with 45% in group 1 and 44% in group 2 (P = 0.96) showing SSEP activity at 30 days. At 90 days most rats showed SSEP activity (91% vs.80% respectively, P = 0.46). The CMAP also demonstrated no statistically significant differences in latency (1.39 ms in group 1 vs. 1.63 ms in group 2; P = 0.48) and amplitude (6.28 mv vs. 6.43 mv respectively; P = 0.8). Ultrasonography demonstrated tissue growth inside the chitosan tube. Gastrocnemius muscle weight showed no statistically significant difference. Histomorphometry of the distal sciatic nerve, 90 days post reconstructive procedure, showed similar number of myelinated fibers and size parameters in both groups (P ≥ 0.05).

CONCLUSIONS

Chitosan hollow tube used for peripheral nerve reconstruction of rat sciatic nerve showed similar results in comparison to autologous nerve grafting. © 2015 Wiley Periodicals, Inc. Microsurgery 36:664-671, 2016.

Biocompatibility and characterization of a peptide amphiphile hydrogel for applications in peripheral nerve regeneration

Peripheral nerve injury is a debilitating condition for which new bioengineering solutions are needed. Autografting, the gold standard in treatment, involves sacrifice of a healthy nerve and results in loss of sensation or function at the donor site. One alternative solution to autografting is to use a nerve guide conduit designed to physically guide the nerve as it regenerates across the injury gap. Such conduits are effective for short gap injuries, but fail to surpass autografting in long gap injuries. One strategy to enhance regeneration inside conduits in long gap injuries is to fill the guide conduits with a hydrogel to mimic the native extracellular matrix found in peripheral nerves. In this work, a peptide amphiphile (PA)-based hydrogel was optimized for peripheral nerve repair. Hydrogels consisting of the PA C₁₆GSH were compared with a commercially available collagen gel. Schwann cells, a cell type important in the peripheral nerve regenerative cascade, were able to spread, proliferate, and migrate better on C₁₆GSH gels in vitro when compared with cells seeded on collagen gels. Moreover, C₁₆GSH gels were implanted subcutaneously in a murine model and were found to be biocompatible, degrade over time, and support angiogenesis without causing inflammation or a foreign body immune response. Taken together, these results help optimize and instruct the development of a new synthetic hydrogel as a luminal filler for conduit-mediated peripheral nerve repair.

The influence of vascularization of transplanted processed allograft nerve on return of motor function in rats

Processed nerve allografts have become an alternative to repair segmental nerve defects, with results comparable with autografts regarding sensory recovery; however, they have failed to reproduce comparable motor recovery. The purpose of this study was to determine how revascularizaton of processed nerve allograft would affect motor recovery. Eighty-eight rats were divided in four groups of 22 animals each. A unilateral 10-mm sciatic nerve defect was repaired with allograft (group I), allograft wrapped with silicone conduit (group II), allograft augmented with vascular endothelial growth factor (group III), or autograft (group IV). Eight animals from each group were sacrificed at 3 days, and the remaining animals at 16 weeks. Revascularization was evaluated by measuring the graft capillary density at 3 days and 16 weeks. Measurements of ankle contracture, compound muscle action potential, tibialis anterior muscle weight and force, and nerve histomorphometry were performed at 16 weeks. All results were normalized to the contralateral side. The results of capillary density at 3 days were 0.99% ± 1.3% for group I, 0.33% ± 0.6% for group II, 0.05% ± 0.1% for group III, and 75.6% ± 45.7% for group IV. At 16 weeks, the results were 69.9% ± 22.4% for group I, 37.0% ± 16.6% for group II, 84.6% ± 46.6% for group III, and 108.3% ± 46.8% for group IV. The results of muscle force were 47.5% ± 14.4% for group I, 21.7% ± 13.5% for group II, 47.1% ± 7.9% for group III, and 54.4% ± 10.6% for group IV. The use of vascular endothelial growth factor in the fashion used in this study improved neither the nerve allograft short-term revascularization nor the functional motor recovery after 16 weeks. Blocking allograft vascularization from surrounding tissues was detrimental for motor recovery. The processed nerve allografts used in this study showed similar functional motor recovery compared with that of the autograft.

Chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor promotes sciatic nerve repair

A chemically extracted acellular allogeneic nerve graft can reduce postoperative immune rejection, similar to an autologous nerve graft, and can guide neural regeneration. However, it remains poorly understood whether a chemically extracted acellular allogeneic nerve graft combined with neurotrophic factors provides a good local environment for neural regeneration. This study investigated the repair of injured rat sciatic nerve using a chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor. An autologous nerve anastomosis group and a chemical acellular allogeneic nerve bridging group were prepared as controls. At 8 weeks after repair, sciatic functional index, evoked potential amplitude of the soleus muscle, triceps wet weight recovery rate, total number of myelinated nerve fibers and myelin sheath thickness were measured. For these indices, values in the three groups showed the autologous nerve anastomosis group > chemically extracted acellular nerve graft + ciliary neurotrophic factor group > chemical acellular allogeneic nerve bridging group. These results suggest that chemically extracted acellular nerve grafts combined with ciliary neurotrophic factor can repair sciatic nerve defects, and that this repair is inferior to autologous nerve anastomosis, but superior to chemically extracted acellular allogeneic nerve bridging alone.

Evaluation of sensory recovery after reconstruction of digital nerves of the hand using muscle-in-vein conduits in comparison to nerve suture or nerve autografting

BACKGROUND

Muscle-in-vein conduits are a good alternative solution to nerve autografts for bridging peripheral nerve defects since enough graft material is available and no loss of sensation at the harvesting area is expected. The purpose of this study was to compare regeneration results after digital nerve reconstruction with muscle-in-vein conduits, nerve autografts, or direct suture.

PATIENTS AND METHODS

46 patients with 53 digital nerve injuries of the hand subjected to direct suture (n = 22) or reconstruction of 1-6 cm long defects with either nerve autografts (n = 14) or muscle-in-vein conduits (n = 17) between 2008 and 2012, were examined using the two-point discrimination and Semmes-Weinstein Monofilaments.

RESULTS

The follow-up examinations took place 12 to 58 months after surgery. A median reduction of sensibility of 2 Semmes-Weinstein monofilaments compared with intact digits was observed after direct suture (DS) and of 2.5 and 2 Semmes-Weinstein monofilaments after reconstruction with autologous nerve grafts (ANG) and muscle-in-vein conduits (MVC), respectively. No statistically significant differences between all three groups could be found with a significance level set by a P < 0.006 (PDS-ANG = 0.24, PDS-MVC = 0.03, PANG-MVC = 0.52). After harvesting a nerve graft, reduction of sensibility at the donor site occurred in 10 of 14 cases but only in one case after harvesting a muscle-in-vein conduit.

CONCLUSIONS

Muscle-in-vein conduits may be a good alternative solution to autografts for the reconstruction of digital nerves, since no significant differences could be demonstrated between the two methods.

Perspectives of employing mesenchymal stem cells from the Wharton's jelly of the umbilical cord for peripheral nerve repair

Mesenchymal stem cells (MSCs) from Wharton's jelly present high plasticity and low immunogenicity, turning them into a desirable form of cell therapy for the injured nervous system. Their isolation, expansion, and characterization have been performed from cryopreserved umbilical cord tissue. Great concern has been dedicated to the collection, preservation, and transport protocols of the umbilical cord after the parturition to the laboratory in order to obtain samples with higher number of viable MSCs without microbiological contamination. Different biomaterials like chitosan-silicate hybrid, collagen, PLGA90:10, poly(DL-lactide-ɛ-caprolactone), and poly(vinyl alcohol) loaded with electrical conductive materials, associated to MSCs have also been tested in the rat sciatic nerve in axonotmesis and neurotmesis lesions. The in vitro studies of the scaffolds included citocompatibility evaluation of the biomaterials used and cell characterization by imunocytochemistry, karyotype analysis, differentiation capacity into neuroglial-like cells, and flow cytometry. The regeneration process follow-up has been performed by functional analysis and the repaired nerves processed for stereological studies permitted the morphologic regeneration evaluation. The MSCs from Wharton's jelly delivered through tested biomaterials should be regarded a potentially valuable tool to improve clinical outcome especially after trauma to sensory nerves. In addition, these cells represent a noncontroversial source of primitive mesenchymal progenitor cells, which can be harvested after birth, cryogenically stored, thawed, and expanded for therapeutic uses. The importance of a longitudinal study concerning tissue engineering of the peripheral nerve, which includes a multidisciplinary team able to develop biomaterials associated to cell therapies, to perform preclinical trials concerning animal welfare and the appropriate animal model is here enhanced.

Neural tissue engineering options for peripheral nerve regeneration

Tissue engineered nerve grafts (TENGs) have emerged as a potential alternative to autologous nerve grafts, the gold standard for peripheral nerve repair. Typically, TENGs are composed of a biomaterial-based template that incorporates biochemical cues. A number of TENGs have been used experimentally to bridge long peripheral nerve gaps in various animal models, where the desired outcome is nerve tissue regeneration and functional recovery. So far, the translation of TENGs to the clinic for use in humans has met with a certain degree of success. In order to optimize the TENG design and further approach the matching of TENGs with autologous nerve grafts, many new cues, beyond the traditional ones, will have to be integrated into TENGs. Furthermore, there is a strong requirement for monitoring the real-time dynamic information related to the construction of TENGs. The aim of this opinion paper is to specifically and critically describe the latest advances in the field of neural tissue engineering for peripheral nerve regeneration. Here we delineate new attempts in the design of template (or scaffold) materials, especially in the context of biocompatibility, the choice and handling of support cells, and growth factor release systems. We further discuss the significance of RNAi for peripheral nerve regeneration, anticipate the potential application of RNAi reagents for TENGs, and speculate on the possible contributions of additional elements, including angiogenesis, electrical stimulation, molecular inflammatory mediators, bioactive peptides, antioxidant reagents, and cultured biological constructs, to TENGs. Finally, we consider that a diverse array of physicochemical and biological cues must be orchestrated within a TENG to create a self-consistent coordinated system with a close proximity to the regenerative microenvironment of the peripheral nervous system.

Follow-up evaluation with ultrasonography of peripheral nerve injuries after an earthquake

Published data on earthquake-associated peripheral nerve injury is very limited. Ultrasonography has been proven to be efficient in the clinic to diagnose peripheral nerve injury. The aim of this study was to assess the role of ultrasound in the evaluation of persistent peripheral nerve injuries 1 year after the Wenchuan earthquake. Thirty-four patients with persistent clinical symptoms and neurologic signs of impaired nerve function were evaluated with sonography prior to surgical repair. Among 34 patients, ultrasonography showed that 48 peripheral nerves were entrapped, and 11 peripheral nerves were disrupted. There was one case of misdiagnosis on ultrasonography. The concordance rate of ultrasonographic findings with those of surgical findings was 98%. A total of 48 involved nerves underwent neurolysis and the symptoms resolved. Only five nerves had scar tissue entrapment. Preoperative and postoperative clinical and ultrasonographic results were concordant, which verified that ultrasonography is useful for preoperative diagnosis and postoperative evaluation of injured peripheral nerves.

Molecular self-assembly guides the fabrication of peptide nanofiber scaffolds for nerve repair

The particular features render ionic self-complementary peptide-formed and peptide amphiphile-formed nanofiber scaffolds to be compelling biomaterial substrates for nerve repair.

Effect of surface pore structure of nerve guide conduit on peripheral nerve regeneration

Polycaprolactone (PCL)/Pluronic F127 nerve guide conduits (NGCs) with different surface pore structures (nano-porous inner surface vs. micro-porous inner surface) but similar physical and chemical properties were fabricated by rolling the opposite side of asymmetrically porous PCL/F127 membranes. The effect of the pore structure on peripheral nerve regeneration through the NGCs was investigated using a sciatic nerve defect model of rats. The nerve fibers and tissues were shown to have regenerated along the longitudinal direction through the NGC with a nano-porous inner surface (Nanopore NGC), while they grew toward the porous wall of the NGC with a micro-porous inner surface (Micropore NGC) and, thus, their growth was restricted when compared with the Nanopore NGC, as investigated by immunohistochemical evaluations (by fluorescence microscopy with anti-neurofilament staining and Hoechst staining for growth pattern of nerve fibers), histological evaluations (by light microscopy with Meyer's modified trichrome staining and Toluidine blue staining and transmission electron microscopy for the regeneration of axon and myelin sheath), and FluoroGold retrograde tracing (for reconnection between proximal and distal stumps). The effect of nerve growth factor (NGF) immobilized on the pore surfaces of the NGCs on nerve regeneration was not so significant when compared with NGCs not containing immobilized NGF. The NGC system with different surface pore structures but the same chemical/physical properties seems to be a good tool that is used for elucidating the surface pore effect of NGCs on nerve regeneration.

Recovery from rat sciatic nerve injury in vivo through the use of differentiated MDSCs in vitro

In this study, muscle-derived stem cells (MDSCs) whose differentiation into neuron-like cells was induced by ciliary neurotrophic factor (CNTF) and Salvia (Salvia miltiorrhiza) in vitro were used to repair rat sciatic nerve injuries in vivo, in order to investigate their multifunctional characteristics as pluripotent stem cells. The sciatic nerve in the right side of the lower limb was exposed under the anesthetized condition of 10% chloral hydrate (0.3 ml/100 g) injection into the abdominal cavity. The tissue which was 0.5 cm above the sciatic nerve bifurcation was broken using a hemostat. After induction, MDSCs were transferred in sodium hyaluronate gel and were placed into the damaged area. An untreated control group was also included in this study. The surgical area was sutured after washing with gentamycin sulfate solution. Sciatic nerve function index (SFI) was calculated, electrophysiological tests were performed and the recovery rate of gastrocnemius muscle wet weight was also calculated. Four weeks post-surgery, the SFI and the recovery rate of gastrocnemius muscle wet weight in the MDSC group were significantly higher than those in the control group (P<0.05). MDSCs whose differentiation is induced by CNTF and Salvia play an active role in the repair of peripheral nerve injury.

Use of bioabsorbable nerve conduits as an adjunct to brachial plexus neurorrhaphy

PURPOSE

The use of bioabsorbable conduits in digital nerve repair has demonstrated increased efficacy compared to direct repair (for gaps ≤ 4mm) and nerve grafting (for gaps ≥ 8 mm) for sensory recovery in a level 1 human trial. Although nonhuman primate studies on mixed motor-sensory nerves have documented comparable efficacy of the bioabsorbable nerve conduits when compared to nerve repair or grafting, there is minimal human clinical data on motor recovery following bioabsorbable nerve conduit repair. This study investigates the outcomes of bioabsorbable nerve conduits in pure motor nerve reconstruction for adult traumatic brachial plexus injuries.

METHODS

Over a 3-year period, 21 adult patients had 1 or more nerve-to-nerve transfers for traumatic brachial plexus palsy performed using the operative microscope. Ten nerve transfers were performed by advancing the nerve ends into a semi-permeable type I collagen conduit stabilized with 8-0 nylon sutures (conduit-assisted neurorrhaphy). Twenty-eight concurrent nerve transfers were performed using standard end-to-end neurorrhaphy and 8-0 or 9-0 nylon sutures. Clinical evaluation using the Medical Research Council grading system (MRC) was performed at 1 and 2 years postoperatively. Postoperative electromyographic studies were performed in 28 of 38 transfers at final follow-up.

RESULTS

Thirty transfers (17 patients) were available for 2-year follow-up evaluation. All 10 transfers performed with nerve conduits demonstrated clinical recovery and electromyographic reinnervation at 2 years. Eighteen of 20 transfers performed without conduits demonstrated clinical recovery.

CONCLUSIONS

Although no statistical difference in functional recovery was seen in nerve transfers performed with collagen nerve conduits or by traditional neurorrhaphy, this pilot series demonstrated clinical and electromyographic recovery in 10 of 10 motor nerve repairs performed using conduits. These findings warrant continued investigation into the efficacy of conduit-assisted repair for motor nerves, especially in regards to operative time, precision of repair, and speed of nerve recovery.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Interventions in the disturbances in the motor and sensory environment

Treatment of peripheral nervous system (PNS) pathology presents intervention challenges to every therapist. Many of the current and future interventions will be directed at restoring the normal anatomy, function, and biomechanical properties of the PNS, restoring normal neural physiology and ultimately patient function and quality of life. Present interventions use mechanical (movement) or electrical procedures to affect various properties of the peripheral nerve. The purpose of this article was to apply basic science to clinical practice. The pathology and accompanying structural and biomechanical changes in the PNS will be presented in three specific areas commonly encountered in the clinic: nerve injury and laceration; compression neuropathies; and neuropathic pain and neural tension dysfunction. The intent is to address possible interventions exploring the clinical reasoning process that combines basic science and evidence-based best practice. The current lack of literature to support any one intervention requires a strong foundation and understanding of the PNSs' structure and function to refine current and develop new intervention strategies. Current evidence will be presented and linked with future considerations for intervention and research. During this interlude of development and refinement, best practice will rely on sound clinical reasoning skills that incorporate basic science to achieve a successful outcome when treating these challenging patients.

Immunological demyelination enhances nerve regeneration after acute transection injury in the adult rat sciatic nerve

INTRODUCTION

Our recent experiments demonstrate that demyelination enhances peripheral nerve regeneration after contusion injury in the adult rat sciatic nerve. The role of demyelination in peripheral nerve regeneration in a sciatic nerve transection model has yet to be elucidated. We hypothesize that (1) axon regeneration within a region of injury increases after experimental, immunologic demyelination, and (2) regenerated axons are partially derived from the proximal motor axons.

METHODS

Sciatic nerves of adult female Sprague-Dawley rats (n = 20) were injected with a demyelinating agent immediately after transection injury. The sciatic nerves were harvested 1 month (n = 5) and 2 months (n = 5) after surgery. In the control groups, the cut nerves were reapproximated without demyelination therapy. The lesion containing length of nerve was cut into 1-mm transverse blocks and processed to preserve orientation. Specimens were evaluated using structural and immunohistochemical analyses.

RESULTS

A single epineural injection of complement proteins plus antibodies to galactocerebroside resulted in demyelination followed by Schwann cell remyelination. At 1 month, remyelination was clearly shown throughout the injured sciatic nerve segment. At 2 months, there was a statistically significant increase in peripheral nerve regeneration following demyelination therapy as evidenced by total axon count, axon density, and fiber diameter.

CONCLUSION

This study demonstrates enhanced histomorphologic nerve regeneration in the rat sciatic nerve after local delivery of experimental, immunologic demyelination following transection injury. It highlights the utility of demyelination in peripheral nerve regeneration. This therapy may be applicable for tissue-engineered constructs, cell-based systems, and nerve transfers to improve outcomes in peripheral nervous system injuries.

Return of motor function after segmental nerve loss in a rat model: comparison of autogenous nerve graft, collagen conduit, and processed allograft (AxoGen)

BACKGROUND

An effective alternative to nerve autograft is needed to minimize morbidity and solve limited-availability issues. We hypothesized that the use of processed allografts and collagen conduits would allow recovery of motor function that is equivalent to that seen after the use of autografts.

METHODS

Sixty-five Lewis rats were divided into three experimental groups. In each group, a unilateral 10-mm sciatic nerve defect was repaired with nerve autograft, allograft treated by AxoGen Laboratories, or a 2.0-mm-inner-diameter collagen conduit. The animals were studied at twelve and sixteen weeks postoperatively. Evaluation included bilateral measurement of the tibialis anterior muscle force and muscle weight, electrophysiology, assessment of ankle contracture, and peroneal nerve histomorphometry. Muscle force was measured with use of our previously described and validated method. Results were expressed as a percentage of the values on the contralateral side. Two-way analysis of variance (ANOVA) corrected by the Ryan-Einot-Gabriel-Welsch multiple range test was used for statistical investigation (α = 0.05).

RESULTS

At twelve weeks, the mean muscle force (and standard deviation), as compared with that on the contralateral (control) side, was 45.2% ± 15.0% in the autograft group, 43.4% ± 18.0% in the allograft group, and 7.0% ± 9.2% in the collagen group. After sixteen weeks, the recovered muscle force was 65.5% ± 14.1% in the autograft group, 36.3% ± 15.7% in the allograft group, and 12.1% ± 16.0% in the collagen group. Autograft was statistically superior to allograft and the collagen conduit at sixteen weeks with regard to all parameters except histomorphometric characteristics (p < 0.05). The collagen-group results were inferior. All autograft-group outcomes improved from twelve to sixteen weeks, with the increase in muscle force being significant.

CONCLUSIONS

The use of autograft resulted in better motor recovery than did the use of allograft or a collagen conduit for a short nerve gap in rats. A longer evaluation time of sixteen weeks after segmental nerve injuries in rats would be beneficial as more substantial muscle recovery was seen at that time.

Biomaterials for the development of peripheral nerve guidance conduits

Currently, surgical treatments for peripheral nerve injury are less than satisfactory. The gold standard of treatment for peripheral nerve gaps >5 mm is the autologous nerve graft; however, this treatment is associated with a variety of clinical complications, such as donor site morbidity, limited availability, nerve site mismatch, and the formation of neuromas. Despite many recent advances in the field, clinical studies implementing the use of artificial nerve guides have yielded results that are yet to surpass those of autografts. Thus, the development of a nerve guidance conduit, which could match the effectiveness of the autologous nerve graft, would be beneficial to the field of peripheral nerve surgery. Design strategies to improve surgical outcomes have included the development of biopolymers and synthetic polymers as primary scaffolds with tailored mechanical and physical properties, luminal "fillers" such as laminin and fibronectin as secondary internal scaffolds, surface micropatterning, stem cell inclusion, and controlled release of neurotrophic factors. The current article highlights approaches to peripheral nerve repair through a channel or conduit, implementing chemical and physical growth and guidance cues to direct that repair process.

Intrinsic and therapeutic factors determining the recovery of motor function after peripheral nerve transection

Insufficient recovery after peripheral nerve injury has been attributed to (i) poor pathfinding of regrowing axons, (ii) excessive collateral axonal branching at the lesion site and (iii) polyneuronal innervation of the neuromuscular junctions (NMJ). The facial nerve transection model has been used initially to measure restoration of function after varying therapies and to examine the mechanisms underlying their effects. Since it is very difficult to control the navigation of several thousand axons, efforts concentrated on collateral branching and NMJ-polyinnervation. Treatment with antibodies against trophic factors to combat branching improved the precision of reinnervation, but had no positive effects on functional recovery. This suggested that polyneuronal reinnervation--rather than collateral branching--may be the critical limiting factor. The former could be reduced by pharmacological agents known to perturb microtubule assembly and was followed by recovery of function. Because muscle polyinnervation is activity-dependent and can be manipulated, attempts to design a clinically feasible therapy were performed by electrical stimulation or by soft tissue massage. Electrical stimulation applied to the transected facial nerve or to paralysed facial muscles did not improve vibrissal motor performance and failed to diminish polyinnervation. In contrast, gentle stroking of the paralysed muscles (vibrissal, orbicularis oculi, tongue musculature) resulted in full recovery of function. This manual stimulation was also effective after hypoglossal-facial nerve suture and after interpositional nerve grafting, but not after surgical reconstruction of the median nerve. All these findings raise hopes that clinically feasible and effective therapies could be soon designed and tested.

Regeneration and repair of peripheral nerves with different biomaterials: review

Peripheral nerve injury may cause gaps between the nerve stumps. Axonal proliferation in nerve conduits is limited to 10-15 mm. Most of the supportive research has been done on rat or mouse models which are different from humans. Herein we review autografts and biomaterials which are commonly used for nerve gap repair and their respective outcomes. Nerve autografting has been the first choice for repairing peripheral nerve gaps. However, it has been demonstrated experimentally that tissue engineered tubes can also permit lead to effective nerve repair over gaps longer than 4 cm repair that was previously thought to be restorable by means of nerve graft only. All of the discoveries in the nerve armamentarium are making their way into the clinic, where they are, showing great potential for improving both the extent and rate of functional recovery compared with alternative nerve guides.