The response to injury in the peripheral nervous system

The Role of Current Techniques and Concepts in Peripheral Nerve Repair

Patients with peripheral nerve injuries, especially severe injury, often face poor nerve regeneration and incomplete functional recovery, even after surgical nerve repair. This review summarizes treatment options of peripheral nerve injuries with current techniques and concepts and reviews developments in research and clinical application of these therapies.

Differentiation of Human Endometrial Stem Cells into Schwann Cells in Fibrin Hydrogel as 3D Culture

Human endometrial stem cells (hEnSCs) are a new source of adult multipotent stem cells with the ability of differentiation into many cell lineages. Many stem cell sources are desirable for differentiation into Schwann cells. Schwann-like cells derived from hEnSCs may be one of the ideal alternative cell sources for Schwann cell generation. In this study, for differentiation of hEnSCs into Schwann cells, hEnSCs were induced with RA/FSK/PDGF-AA/HRG as an induction medium for 14 days. The cells were cultured in a tissue culture plate (TCP) and fibrin gel matrix. The viability of cultured cells in the fibrin gel and TCP was analyzed with 3-[4,5-dimethyl-2-thia-zolyl]-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay for 7 days. The attachment of cells was analyzed with SEM and DAPI staining. The expression of S100 and P75 as Schwann cell markers was evaluated by immunocytochemistry and quantitative real-time PCR (RT-PCR). The evaluation of the MTT assay and gene expression showed that the survival rate and differentiation of hEnSCs into Schwann cells in the fibrin gel were better than those in the TCP group. These results suggest that human EnSCs can be differentiated into Schwann cells in the fibrin gel better than in the TCP, and the fibrin gel might provide a suitable three-dimensional (3D) scaffold for clinical applications for cell therapy of the nervous system.

SncRNA715 Inhibits Schwann Cell Myelin Basic Protein Synthesis

Myelin basic proteins (MBP) are major constituents of the myelin sheath in the central nervous system (CNS) and the peripheral nervous system (PNS). In the CNS Mbp translation occurs locally at the axon-glial contact site in a neuronal activity-dependent manner. Recently we identified the small non-coding RNA 715 (sncRNA715) as a key inhibitor of Mbp translation during transport in oligodendrocytes. Mbp mRNA localization in Schwann cells has been observed, but has not been investigated in much detail. Here we could confirm translational repression of Mbp mRNA in Schwann cells. We show that sncRNA715 is expressed and its levels correlate inversely with MBP in cultured Schwann cells and in the sciatic nerve in vivo. Furthermore we could reduce MBP protein levels in cultured Schwann cells by increasing the levels of the inhibitory sncRNA715. Our findings suggest similarities in sncRNA715-mediated translational repression of Mbp mRNA in oligodendrocytes and Schwann cells.

Effect of an Epineurial-Like Biohybrid Nerve Conduit on Nerve Regeneration

A novel approach of making a biomimetic nerve conduit was established by seeding adipose-derived adult stem cells (ADSCs) on the external wall of porous poly(d,l-lactic acid) (PLA) nerve conduits. The PLA conduits were fabricated using gas foaming salt and solvent-nonsolvent phase conversion. We examined the effect of two different porous structures (GS and GL) on ADSC growth and proliferation. The GS conduits had better structural stability, permeability, and porosity, as well as better cell viability at 4, 7, and 10 days. The epineurial-like tissue was grown from ADSC-seeded conduits cultured for 7 days in vitro and then implanted into 10-mm rat sciatic nerve defects for evaluation. The regeneration capacity and functional recovery were evaluated by histological staining, electrophysiology, walking track, and functional gait analysis after 6 weeks of implantation. Experimental data indicated that the autograft and ADSC-seeded GS conduits had better functional recovery than the blank conduits and ADSC-seeded GL conduits. The area of regenerated nerve and number of myelinated axons quantified based on the histology also indicated that the autograft and AGS groups performed better than the other two groups. We suggested that ADSCs may interact with endogenous Schwann cells and release neurotrophic factors to promote peripheral nerve regeneration. The design of the conduit may be critical for producing a biohybrid nerve conduit and to provide an epineurial-like support.

Up-regulation of P2X7 receptors mediating proliferation of Schwann cells after sciatic nerve injury

Peripheral nerve injury (PNI) is a common disease, which results in a partial or total loss of motor, sensory and autonomic functions, leading to a decrease in quality of life. Schwann cells play a vital role in maintaining the peripheral nervous system and in injury and repair. Using immunohistochemistry, Western blot, calcium assay and bromodeoxyuridine (BrdU) proliferation assay, the present study clearly demonstrated that P2X7 receptors (R) were expressed in myelinating and non-myelinating Schwann cells in longitudinal sections of sciatic nerves. After sciatic nerve injury (SNI), P2X7R expression in Schwann cells of injured sciatic nerves was significantly up-regulated during the early days of SNI. Double immunofluorescence of proliferating cell nuclear antigen (PCNA) and P2X7R implied that P2X7R may be involved in proliferation of Schwann cells. Further experiments on primary cultures of Schwann cells showed that P2X7R are functionally expressed in Schwann cells of rat sciatic nerves; ATP via P2X7R can promote Schwann cell proliferation, possibly via the MAPK/ERK intracellular signalling pathway. Other possible roles of P2X7R on Schwann cells are discussed.

Axonal regeneration in early stages of sciatic nerve crush injury is enhanced by α7nAChR in rats

This study investigated the role of alpha 7 nicotinic acetylcholine receptor (α7nAChR) in axonal regeneration after crush injury to the rat sciatic nerve. The time course of α7nAChR expression following injury was assessed by immunohistochemistry and western blotting, and local inflammation, as indicated by the expression of tumor necrosis factor (TNF)-α, was detected by enzyme-linked immunosorbent assay. Axonal regeneration was evaluated by the pinch-test, morphometric analysis, and by measuring growth-associated protein 43 expressions. Local α7nAChR expression increased on day 1, peaked on day 3, and remained elevated on day 5 following nerve injuries. Prominent α7nAChR immunoreactivity was observed in Schwann cells, endothelial cells of the capillaries, and a small number of inflammatory cells. Application of the selective α7nAChR agonist PNU-282987 decreased TNF-α level and enhanced axonal regeneration, but this effect was blocked by concomitant treatment with methyllycaconitine, a α7nAChR antagonist. The results indicate that the local expression of α7nAChR is increased during the early stages of sciatic nerve injury, and application of a α7nAChR agonist promotes axonal regeneration by suppression of TNF-α-mediated inflammation. The α7nAChR can act as a neuroprotective agent and α7nAChR activation may be a useful therapeutic strategy to treat peripheral nerve injury.

A combination of Schwann-cell grafts and aerobic exercise enhances sciatic nerve regeneration

Background

Despite the regenerative potential of the peripheral nervous system, severe nerve lesions lead to loss of target-organ innervation, making complete functional recovery a challenge. Few studies have given attention to combining different approaches in order to accelerate the regenerative process.

Objective

Test the effectiveness of combining Schwann-cells transplantation into a biodegradable conduit, with treadmill training as a therapeutic strategy to improve the outcome of repair after mouse nerve injury.

Methods

Sciatic nerve transection was performed in adult C57BL/6 mice; the proximal and distal stumps of the nerve were sutured into the conduit. Four groups were analyzed: acellular grafts (DMEM group), Schwann cell grafts (3×10⁵/2 µL; SC group), treadmill training (TMT group), and treadmill training and Schwann cell grafts (TMT + SC group). Locomotor function was assessed weekly by Sciatic Function Index and Global Mobility Test. Animals were anesthetized after eight weeks and dissected for morphological analysis.

Results

Combined therapies improved nerve regeneration, and increased the number of myelinated fibers and myelin area compared to the DMEM group. Motor recovery was accelerated in the TMT + SC group, which showed significantly better values in sciatic function index and in global mobility test than in the other groups. The TMT + SC group showed increased levels of trophic-factor expression compared to DMEM, contributing to the better functional outcome observed in the former group. The number of neurons in L4 segments was significantly higher in the SC and TMT + SC groups when compared to DMEM group. Counts of dorsal root ganglion sensory neurons revealed that TMT group had a significant increased number of neurons compared to DMEM group, while the SC and TMT + SC groups had a slight but not significant increase in the total number of motor neurons.

Conclusion

These data provide evidence that this combination of therapeutic strategies can significantly improve functional and morphological recovery after sciatic injury.

Does pulsed magnetic field therapy influence nerve regeneration in the median nerve model of the rat?

The aim of this study was to evaluate the impact of pulsed magnetic field therapy on peripheral nerve regeneration after median nerve injury and primary coaptation in the rat. Both median nerves were surgically exposed and denervated in 24 female Wistar rats. A microsurgical coaptation was performed on the right side, whereas on the left side a spontaneous healing was prevented. The study group underwent a daily pulsed magnetic field therapy; the other group served as a control group. The grasping force was recorded 2 weeks after the surgical intervention for a period of 12 weeks. The right median nerve was excised and histologically examined. The histomorphometric data and the functional assessments were analyzed by t-test statistics and one-way ANOVA. One-way ANOVA indicated a statistically significant influence of group affiliation and grasping force (P = 0.0078). Grasping strength was higher on a significant level in the experimental group compared to the control group permanently from the 9th week to the end of the study. T-test statistics revealed a significantly higher weight of the flexor digitorum sublimis muscle (P = 0.0385) in the experimental group. The histological evaluation did not reveal any statistically significant differences concerning the histomorphometric parameters. Our results suggest that the pulsed magnetic field therapy has a positive influence on the functional aspects of neural regeneration. More studies are needed to precisely evaluate and optimize the intensity and duration of the application.

Effects of safranal, a constituent of saffron, and vitamin E on nerve functions and histopathology following crush injury of sciatic nerve in rats

Safranal is one of the major components of saffron and has many biological effects such as antioxidant property. The present study investigated the effects of safranal on sciatic nerve function after induction of crush injury. We also used of vitamin E as a reference potent antioxidant agent. In anesthetized rats, right sciatic nerve was crushed using a small haemostatic forceps. Functional recovery was assessed using sciatic functional index (SFI). Acetone spray and von Frey filament tests were used for neuropathic pain assay. Histopathological changes including severities of Wallerian degeneration of sciatic nerve and gastrocnemius muscle atrophy were investigated by light microscopy. Blood levels of malodialdehyde (MDA) were also measured. The SFI values were accelerated, cold and mechanical allodynia were suppressed, the severities of Wallerian degeneration and muscular atrophy were improved, and the increased MDA level was reversed with 10 consecutive days intraperitoneal injections of 0.2 and 0.8 mg/kg of safranal and 100 mg/kg of vitamin E. It is concluded that safranal and vitamin E produced same improving effects on crushed-injured sciatic nerve functions. Inhibition of oxidative stress pathway may be involved in improving effects of safranal and vitamin E on functions and histopathology of an injured peripheral nerve.

Epidermal cells are the primary phagocytes in the fragmentation and clearance of degenerating dendrites in Drosophila

During developmental remodeling, neurites destined for pruning often degenerate on-site. Physical injury also induces degeneration of neurites distal to the injury site. Prompt clearance of degenerating neurites is important for maintaining tissue homeostasis and preventing inflammatory responses. Here we show that in both dendrite pruning and dendrite injury of Drosophila sensory neurons, epidermal cells rather than hemocytes are the primary phagocytes in clearing degenerating dendrites. Epidermal cells act via Draper-mediated recognition to facilitate dendrite degeneration and to engulf and degrade degenerating dendrites. Using multiple dendritic membrane markers to trace phagocytosis, we show that two members of the CD36 family, croquemort (crq) and debris buster (dsb), act at distinct stages of phagosome maturation for dendrite clearance. Our finding reveals the physiological importance of coordination between neurons and their surrounding epidermis, for both dendrite fragmentation and clearance.

CAP1 was associated with actin and involved in Schwann cell differentiation and motility after sciatic nerve injury

Adenylate cyclase-associated protein 1 (CAP1), a member of cyclase-associated proteins that regulating actin dynamics, was shown to regulate actin filaments, localize to dynamic actin structures and mediate such processes as establishment of cell polarity, motility, morphogenesis, receptor-mediated endocytosis and mRNA location. But little is known about the role of CAP1 during peripheral nervous system injury. Here, we found the spatiotemporal protein expression of CAP1 after sciatic nerve crush. After crush, CAP1 had an increased protein expression level, reached a peak at about day 5 and then returned to the normal level at 4 weeks, similar to Oct-6. Besides, in 5-day injured tissue, using double immunofluorescent staining we found CAP1 had a colocalization with S100 and Oct-6. In vitro, during the process of cAMP-induced Schwann cells differentiation, we observed enhanced expression of CAP1 and P0. Specially, CAP1-specific siRNA-tranfected SCs did not show significant actin structure which form cellure surface tension and protrusion shape after cAMP treatment. And we observed the interaction of CAP1 with actin and that CAP1-specific siRNA-transfected SCs had a decreased motility and migration. Together, all these data indicated that the change of CAP1 protein expression was associated with Schwann cells motility and differentiation after the crush of sciatic nerve.

Advances in experimental and clinical studies of chemotaxis

The theory of chemotaxis has been widely accepted, but its mechanisms are disputed. Chemotactic growth of peripheral nerves may be tissue, topographic and end-organ specific. Recent studies indicated that peripheral nerve regeneration lacks topographic specificity, but whether it has end-organ specificity is disputed. Chemotaxis in nerve regeneration is affected by the distance between stumps, volume, and neurotrophic support, as well as the structure of distal nerve stumps. It can be applied to achieve precise repair of nerves and complete recovery of end organ function. Small gap sleeve bridging technique, which is based on this theory shows promising effects but it is still challenging to find the perfect combination of nerve conduits, cells and neurotrophic factors to put it intoits best use. In this paper, we made a comprehensive review of mechanisms, effect factors and applications of chemotaxis.

Temporal-spatial expressions of Spy1 in rat sciatic nerve after crush

As a novel cell cycle protein, Spy1 enhances cell proliferation, promotes the G1/S transition as well as inhibits apoptosis in response to UV irradiation. Spy1 levels are tightly regulated during mammary development, and overexpression of Spy1 accelerates tumorigenesis in vivo. But little is known about the role of Spy1 in the pathological process of damage and regeneration of the peripheral nervous system. Here we established a rat sciatic nerve crush (SNC) model to examine the spatiotemporal expression of Spy1. Spy1 expression was elevated gradually after sciatic nerve crush and peaked at day 3. The alteration was due to the increased expression of Spy1 in axons and Schwann cells after SNC. Spy1 expression correlated closely with Schwann cells proliferation in sciatic nerve post injury. Furthermore, Spy1 largely localized in axons in the crushed segment, but rarely co-localized with GAP43. These findings suggested that Spy1 participated in the pathological process response to sciatic nerve injury and may be associated with Schwann cells proliferation and axons regeneration.

The brain-derived neurotrophic factor, nerve growth factor, neurotrophin-3, and induced nitric oxide synthase expressions after low-level laser therapy in an axonotmesis experimental model

BACKGROUND DATA

A robust body of evidence has shown that low-level laser therapy (LLLT) improves peripheral nerve regeneration. However, the biochemical background triggered in this process is not yet fully understood.

OBJECTIVE

The purpose of this study was to evaluate the mRNA expression of neurotrophic factors (brain-derived neurotrophic factor [BDNF], nerve growth factor [NGF], and neurotrophin-3, [NT-3]) and also an inflammatory marker (induced nitric oxide synthase [iNOS]) in an axonotmesis experimental model after low-level laser therapy.

METHODS

Thirty-six adult male Wistar rats (250-350 g) were subjected to right sciatic nerve crush injury, and 24 h later, the animals in the three different experimental groups (n=18) were irradiated on a daily basis with helium-neon laser (collimated HeNe laser, continuous emission, wavelength: 632.8 nm, power density: 0.5 mW/cm(2), irradiation time: 20 sec, energy density: 10 J/cm(2)) during 7, 14, and 21 consecutive days, respectively. The control group (n=18) underwent the same procedures, but with the equipment turned off. At the end of the experiments, animals were killed with an overdose of anesthesia to remove samples from the sciatic nerve lesion epicenter to determine the mRNA expression of BDNF, NGF, NT-3 and iNOS enzyme.

RESULTS

Comparisons between groups showed that HeNe laser increased the mRNA expression of both BDNF and NGF factors after 14 days of LLLT, with peak expression at the 21st day. Increase in NT-3 mRNA expression was not observed. In addition, HeNe laser produced iNOS expression reduction, which played an important role in the inflammatory process.

CONCLUSIONS

The reported data could have a relevant practical value because LLLT is a noninvasive procedure, and have revealed significant increase in neurotrophic factor expressions and inflammatory process reduction, opening the possibility of using LLLT as an important aid to nerve regeneration process.

Repercussões morfológicas e funcionais do exercício sobre a regeneração nervosa periférica

INTRODUÇÃO: A indicação de exercícios físicos como abordagem terapêutica após lesões nervosas periféricas, apesar de resultados clínicos favoráveis, ainda não é consenso na literatura pertinente. Objetivos: Este estudo buscou avaliar a interferência do exercício em roda motorizada no processo de regeneração nervosa periférica. MATERIAIS E MÉTODOS: Foram utilizados 48 ratos Wistar divididos proporcionalmente em quatro grupos de 12 ratos cada (seis controles e seis experimentais). Após treinamento, os ratos foram submetidos à axonotmese do nervo ciático direito. Todos os grupos iniciaram o regime de exercícios diários 24 horas após a lesão, porém com durações diferenciadas (G1 por 28 dias; G2 por 21 dias, G3 por 14 dias e G4 por sete dias). O exercício teve tempo e velocidade ajustados de acordo com o tempo de tratamento para cada grupo. RESULTADOS: Por meio do cálculo do Índice Funcional do Ciático, os animais submetidos ao exercício apresentaram sinais de atraso na recuperação funcional da marcha, em comparação a animais controles. Na análise histológica dos nervos lesionados, observou-se que animais exercitados apresentaram sinais de preservação dos axônios no coto proximal e de degeneração no coto distal, e os animais exercitados por somente sete dias não apresentaram a mesma característica degenerativa no coto distal. A aplicação de exercícios ativos e sem carga em animais que sofreram axonotmese interfere negativamente no processo de recuperação funcional de alguns parâmetros da marcha. CONCLUSÃO: Apesar de o exercício ativo não ter interferido na manutenção da viabilidade neuronal nos sítios proximais à lesão, sua continuidade prejudicou a viabilidade dos cotos neurais distais, provável causa do atraso na recuperação funcional da marcha.

Gene expression patterns specific to the regenerating limb of the Mexican axolotl

Salamander limb regeneration is dependent upon tissue interactions that are local to the amputation site. Communication among limb epidermis, peripheral nerves, and mesenchyme coordinate cell migration, cell proliferation, and tissue patterning to generate a blastema, which will form missing limb structures. An outstanding question is how cross-talk between these tissues gives rise to the regeneration blastema. To identify genes associated with epidermis-nerve-mesenchymal interactions during limb regeneration, we examined histological and transcriptional changes during the first week following injury in the wound epidermis and subjacent cells between three injury types; 1) a flank wound on the side of the animal that will not regenerate a limb, 2) a denervated limb that will not regenerate a limb, and 3) an innervated limb that will regenerate a limb. Early, histological and transcriptional changes were similar between the injury types, presumably because a common wound-healing program is employed across anatomical locations. However, some transcripts were enriched in limbs compared to the flank and are associated with vertebrate limb development. Many of these genes were activated before blastema outgrowth and expressed in specific tissue types including the epidermis, peripheral nerve, and mesenchyme. We also identified a relatively small group of transcripts that were more highly expressed in innervated limbs versus denervated limbs. These transcripts encode for proteins involved in myelination of peripheral nerves, epidermal cell function, and proliferation of mesenchymal cells. Overall, our study identifies limb-specific and nerve-dependent genes that are upstream of regenerative growth, and thus promising candidates for the regulation of blastema formation.

Drosophila motor neuron retraction during metamorphosis is mediated by inputs from TGF-β/BMP signaling and orphan nuclear receptors

Larval motor neurons remodel during Drosophila neuro-muscular junction dismantling at metamorphosis. In this study, we describe the motor neuron retraction as opposed to degeneration based on the early disappearance of β-Spectrin and the continuing presence of Tubulin. By blocking cell dynamics with a dominant-negative form of Dynamin, we show that phagocytes have a key role in this process. Importantly, we show the presence of peripheral glial cells close to the neuro-muscular junction that retracts before the motor neuron. We show also that in muscle, expression of EcR-B1 encoding the steroid hormone receptor required for postsynaptic dismantling, is under the control of the ftz-f1/Hr39 orphan nuclear receptor pathway but not the TGF-β signaling pathway. In the motor neuron, activation of EcR-B1 expression by the two parallel pathways (TGF-β signaling and nuclear receptor) triggers axon retraction. We propose that a signal from a TGF-β family ligand is produced by the dismantling muscle (postsynapse compartment) and received by the motor neuron (presynaptic compartment) resulting in motor neuron retraction. The requirement of the two pathways in the motor neuron provides a molecular explanation for the instructive role of the postsynapse degradation on motor neuron retraction. This mechanism insures the temporality of the two processes and prevents motor neuron pruning before postsynaptic degradation.

A central role for the ERK-signaling pathway in controlling Schwann cell plasticity and peripheral nerve regeneration in vivo

Following damage to peripheral nerves, a remarkable process of clearance and regeneration takes place. Axons downstream of the injury degenerate, while the nerve is remodeled to direct axonal regrowth. Schwann cells are important for this regenerative process. "Sensing" damaged axons, they dedifferentiate to a progenitor-like state, in which they aid nerve regeneration. Here, we demonstrate that activation of an inducible Raf-kinase transgene in myelinated Schwann cells is sufficient to control this plasticity by inducing severe demyelination in the absence of axonal damage, with the period of demyelination/ataxia determined by the duration of Raf activation. Remarkably, activation of Raf-kinase also induces much of the inflammatory response important for nerve repair, including breakdown of the blood-nerve barrier and the influx of inflammatory cells. This reversible in vivo model identifies a central role for ERK signaling in Schwann cells in orchestrating nerve repair and is a powerful system for studying peripheral neuropathies and cancer.

Neuregulin1 administration increases axonal elongation in dissociated primary sensory neuron cultures

Neuregulin1 is a family of growth and differentiation factors involved in various functions of both peripheral and central nervous system including the regenerative processes that underlie regeneration of damaged peripheral nerves. In the present study we tested in vitro the effect of Neuregulin1 administration on dissociated rat dorsal root ganglion (DRG). Activity of neuregulin1 was compared to the activity of nerve growth factor in the same in vitro experimental model. Results showed that neurite outgrowth is enhanced by the addition of both neuregulin1 and nerve growth factor to the culture medium. While neuregulin1 was responsible for the growth of longer neurites, DRG neurons incubated with nerve growth factor showed shorter and more branched axons. Using enzyme-linked immunosorbent assay we also showed that the release of nerve growth factor, but not of brain derived neurotrophic factor is improved in DRG neuron treated with neuregulin1. On the other hand, the assay with growth factor blocking antibody, showed that effects exerted by neuregulin1 on neurite outgrowth is only partially due to the release of nerve growth factor. Taken together the results of this study provide a better understanding on the role of neuregulin1 in sensory neurons.

Realizing the maximum potential of Schwann cells to promote recovery from spinal cord injury

Transplantation of Schwann cells (SCs) has been extensively investigated as a therapeutic intervention in rodent models of spinal cord injury (SCI). Here we review both strengths and weaknesses of this approach and discuss additional strategies for maximizing the potential of SCs to repair the injured spinal cord. With no additional treatments, SCs were consistently shown to provide a bridge across the lesion site, supporting the ingrowth of sensory and propriospinal axons, to myelinate axons and to decrease the size of cavities formed after injury. Supraspinal axons did not, however, grow onto the bridge, axons failed to traverse the caudal SC-host cord interface and transplanted SC survival was poor. More recent studies have shown that the potential of SC transplantation as a therapeutic approach can be strongly enhanced by combining additional strategies . For example, combining SC transplantation with elevation of cAMP levels resulted in growth of brainstem axons into the SC graft and caudal to the lesion and in significant improvements in locomotion. Axon growth (and functional improvement) have been increased by strategies to raise neurotrophin levels, either by injection or by genetic modification of the SCs before transplantation. A major problem in maximizing SC potential in injured cord has been in achieving good integration of the transplanted cells with the adjacent cord parenchyma. Several previous studies suggested an ability of SCs to migrate extensively in CNS tissue when astroctyes were absent and to myelinate CNS axons. Furthermore, in some cases involving very limited injury, SCs migrated and integrated well even in the presence of host astrocytes. Consistent with these observations, treatments with an enzyme, chondroitinase, to modify the SC-astrocyte interface surrounding the graft, have shown much promise. Very new studies have shown that SCs derived from SC precursors show a higher ability to survive, integrate well with host tissue and support brainstem axon growth into and beyond the graft, confirming the innate promise of SCs in spinal cord repair. We review one clinical trial already underway in Iran testing SC transplantation in patients with SCI. Finally, we briefly describe a protocol, adaptable to the principles of good manufacturing practice, for generating large numbers of human SCs. Overall, the available evidence suggests that SCs, especially when used in combination with other treatments, offer one of the best hopes we have today of devising an effective treatment for spinal cord repair.

Peripheral nerve response to injury

Oral and maxillofacial surgeons caring for patients who have sustained a nerve injury to a branch of the peripheral trigeminal nerve must possess a basic understanding of the response of the peripheral nerves to trauma. The series of events that subsequently take place are largely dependent on the injury type and severity. Regeneration of the peripheral nerve is possible in many instances and future manipulation of the regenerative microenvironment will lead to advances in the management of these difficult injuries.

Median nerve compression from a nondisplaced fracture of the coronoid process of the ulna: a case report

Median nerve neuropathy following an elbow injury is uncommon. When it occurs, understanding the median nerve distribution and anatomy is crucial for identifying the cause and for distinguishing cases that can be managed with observation as opposed to intervention. The consequences of misdiagnosis can result in permanent disability. Understanding the mechanisms of nerve injury will help the clinician anticipate prognosis and guide treatment. Stretch, transection, and compression of nerves may present similarly, but isolating the mechanism and the extent of injury can guide the treatment modalities and help predict the overall recovery. The case is a report of median nerve compression in a woman after a nondisplaced fracture of the coronoid process of the ulna. Despite the unique nature of the patient's symptoms, the neuropathy resolved with "watchful waiting." The location of the injury was a key component in identifying the cause of the neuropathy. It highlights the importance of identifying a cause; some cases will resolve without intervention. Clinicians should consider median nerve compression when presented with a patient experiencing neurologic symptoms following such a fracture.

Effects of low intensity pulsed ultrasound on rat Schwann cells metabolism

The effects of low intensity pulsed ultrasound to tenocytes and osteocytes are well understood and applied clinically. However, its effects on cultured Schwann cells are still not well elucidated. This study was designed to elucidate the effects of low intensity pulsed ultrasound on cultured Schwann cells and their possible molecular mechanism. Schwann cells were harvested from sciatic nerves of 3-day-old Sprague-Dawley rats. Low intensity pulsed ultrasound stimulator (frequency: 1 MHz, duration: 2 min, duty cycle: 20%, total treatment time: 3 min) was applied to three different culture conditions: regular culture medium containing 0, 5, or 10% fetal bovine serum. The viability, damage, and differentiation of Schwann cells were examined; gene expression was also analyzed. In the presence of 0.3 W/cm(2) pulsed ultrasound stimulation, increases in cell viability and decreases in cell apoptosis were observed in the serum deprivation group; in this culture condition, interleukin-1, tumor necrosis factor-alpha, and protein zero genes expression were downregulated and Desert Hedgehog transcripts gene expression was upregulated. We concluded that intervention with low intensity pulsed ultrasound could promote Schwann cell proliferation, prevent cell death, and keep adequate phenotype presentation for peripheral nerve recovery. The low intensity pulsed ultrasound stimulation to an injured nerve site could be applied as early as possible especially when the microenvironment is almost serum-free to obtain the most benefit.

Regeneration potential and survival of transplanted undifferentiated adipose tissue-derived stem cells in peripheral nerve conduits

Adipose tissue-derived stem cells (ADSCs) have shown potential for the treatment of nerve injuries. Most previous efforts have aimed at stimulating regeneration by using neural-differentiation protocols, but the potential of undifferentiated ADSCs to enhance axonal growth as well as their ability to transdifferentiate in situ have been poorly investigated. In this study, using a rat sciatic nerve model we show that ADSCs, transplanted in an artificial nerve conduit, stimulate axonal outgrowth from the proximal nerve stump and evoke greater Schwann cell (SC) proliferation/intrusion in the distal stump. To track the fate of the transplanted cells, we used green fluorescent protein (GFP)-labelling and polymerase chain reaction (PCR) for the detection of the sex determining region Y (SRY) gene in the donor male cells. Both methods indicated a lack of significant quantities of viable cells 14 days after transplantation. These results suggest that any regenerative effect of transplanted ADSCs is more likely to be mediated by an initial boost of released growth factors and/or by an indirect effect on endogenous SCs activity. Future studies need to address long-term cell survival in tissue-engineered nerve conduits to improve the neuroregenerative potential of ADSCs.

A good outcome following complete injury of the brachial plexus

Restoration of hand function is rarely achieved after a complete closed traction lesion of the supraclavicular brachial plexus. We describe the injury, treatment, rehabilitation and long-term results of two patients who regained good function of the upper limb and useful function in the hand after such an injury. Successful repairs were performed within six days of injury. Tinel’s sign proved accurate in predicting the ruptures and the distribution of pain was accurate in predicting avulsion. The severe pain that began on the day of injury resolved with the onset of muscle function.

Recovery of muscle function preceded recovery of sensation. Recovery of the function of C and Aδ fibres was the slowest of all.

Neuregulinas 1-alfa e 1-beta na regeneração de nervos periféricos

OBJETIVO: Avaliar o efeito das neuregulinas 1-alfa e 1-beta na regeneração de nervos ciáticos de camundongos C57BL/6J, adultos, machos, através da técnica de tubulização. MÉTODOS: Utilizaram-se 18 animais, divididos em 3 grupos, implantando-se prótese de polietileno em falhas de 4,0 mm no nervo ciático esquerdo: grupo 1 contendo apenas colágeno purificado (Vitrogen®); grupo 2, colágeno associado a neuregulina 1-alfa; grupo 3 com colágeno e neuregulina 1-beta. O grupo controle foi formado por 6 segmentos de nervos ciáticos direitos. Após 4 semanas, os animais foram sacrificados; extraiu-se segmento do ponto médio do nervo regenerado no interior das próteses, padronizaram-se cortes histológicos e confecção das lâminas para análise histomorfométrica. Confrontaram-se os resultados estatisticamente. RESULTADOS: Os animais tratados com neuregulinas tiveram maior número de axônios mielinizados, com diferença estatisticamente significante quando comparados ao grupo colágeno. Não houve diferença estatística entre os grupos de neuregulinas 1-alfa e 1-beta. CONCLUSÃO: a adição de neuregulinas proporcionou aumento significativo do número de fibras mielinizadas.

Neurotrophic factors improve motoneuron survival and function of muscle reinnervated by embryonic neurons

Motoneuron death can occur over several spinal levels with disease or trauma, resulting in muscle denervation. We tested whether cotransplantation of embryonic neurons with 1 or more neurotrophic factors into peripheral nerve improved axon regeneration, muscle fiber area, reinnervation, and function to a greater degree than cell transplantation alone. Sciatic nerves of adult Fischer rats were cut to denervate muscles; 1 week later, embryonic ventral spinal cord cells (days 14-15) were transplanted into the tibial nerve stump as the only source of neurons for muscle reinnervation. Factors that promote motoneuron survival (cardiotrophin 1; fibroblast growth factor 2; glial cell line-derived neurotrophic factor; insulin-like growth factor 1; leukemia inhibitory factor; and hepatocyte growth factor) were added to the transplant individually or in combinations. Inclusion of a single factor with the cells resulted in comparable myelinated axon counts, muscle fiber areas, and evoked electromyographic activity to cells alone 10 weeks after transplantation. Only cell transplantation with glial cell line-derived neurotrophic factor, hepatocyte growth factor, and insulin-like growth factor 1 significantly increased motoneuron survival, myelinated axon counts, muscle reinnervation, and evoked electromyographic activity compared with cells alone. Thus, immediate application of a specific combination of factors to dissociated embryonic neurons improves survival of motoneurons and the long-term function of reinnervated muscle.

Peripheral neural cell sensitivity to mTHPC-mediated photodynamic therapy in a 3D in vitro model

Background:

The effect of photodynamic therapy (PDT) on neural cells is important when tumours are within or adjacent to the nervous system. The purpose of this study was to investigate PDT using the photosensitiser, meta-tetrahydroxyphenyl chlorin (mTHPC), on rat neurons and satellite glia, compared with human adenocarcinoma cells (MCF-7).

Methods:

Fluorescence microscopy confirmed that mTHPC was incorporated into all three cell types. Sensitivity of cells exposed to mTHPC-PDT (0–10 μg ml^–1) was determined in a novel 3-dimensional collagen gel culture system. Cell death was quantified using propidium iodide and cell types were distinguished using immunocytochemistry. In some cases, neuron survival was confirmed by measuring subsequent neurite growth in monolayer culture.

Results:

MCF-7s and satellite glia were significantly more sensitive to PDT than neurons. Importantly, 4 μg ml^–1 mTHPC-PDT caused no significant neuron death compared with untreated controls but was sufficient to elicit substantial cell death in the other cell types. Initially, treatment reduced neurite length; neurons then extended neurites equivalent to those of untreated controls. The protocol was validated using hypericin (0–3 μg ml^–1), which caused neuron death equivalent to other cell types.

Conclusion:

Neurons in culture can survive mTHPC-PDT under conditions sufficient to kill tumour cells and other nervous system cells.

Schwann cell influence on motor neuron regeneration accuracy

Extensive peripheral nerve injuries can result in the effective paralysis of the entire limb or distal portions of the limb. The major determinant of functional recovery after lesions in the peripheral nervous system is the accurate regeneration of axons to their original target end-organs. We used the mouse femoral nerve as a model to study motor neuron regeneration accuracy in terms of regenerating motor neurons projecting to their original terminal pathway to quadriceps muscle vs. the inappropriate pathway to skin. Using a variety of surgical manipulations and the selective removal of Schwann cells in the distal nerve via molecular targeting, we have examined the respective roles of end-organ influence (muscle) vs. Schwann cells in this model system. We found evidence of a hierarchy of trophic support that regulates motor neuron regeneration accuracy with muscle contact being the most potent, followed by the number or density of Schwann cells in the distal nerve branches. Manipulating the relative levels of these sources of influence resulted in predictable projection patterns of motor neurons into the terminal pathway either to skin or to muscle.

Altered cutaneous nerve regeneration in a simian immunodeficiency virus / macaque intracutaneous axotomy model

To characterize the regenerative pattern of cutaneous nerves in simian immunodeficiency virus (SIV)-infected and uninfected macaques, excisional axotomies were performed in nonglabrous skin at 14-day intervals. Samples were examined after immunostaining for the pan-axonal marker PGP 9.5 and the Schwann cell marker p75 nerve growth factor receptor. Collateral sprouting of axons from adjacent uninjured superficial dermal nerve bundles was the initial response to axotomy. Both horizontal collateral sprouts and dense vertical regeneration of axons from the deeper dermis led to complete, rapid reinnervation of the epidermis at the axotomy site. In contrast to the slower, incomplete reinnervation previously noted in humans after this technique, in both SIV-infected and uninfected macaques epidermal reinnervation was rapid and completed by 56 days postaxotomy. p75 was densely expressed on the Schwann cells of uninjured nerve bundles along the excision line and on epidermal Schwann cell processes. In both SIV-infected and uninfected macaques, Schwann cell process density was highest at the earliest timepoints postaxotomy and then declined at a similar rate. However, SIV-infection delayed epidermal nerve fiber regeneration and remodeling of new sprouts at every timepoint postaxotomy, and SIV-infected animals consistently had lower mean epidermal Schwann cell densities, suggesting that Schwann cell guidance and support of epidermal nerve fiber regeneration may account for altered nerve regeneration. The relatively rapid regeneration time and the completeness of epidermal reinnervation in this macaque model provides a useful platform for assessing the efficacy of neurotrophic or regenerative drugs for sensory neuropathies including those caused by HIV, diabetes mellitus, medications, and toxins.

Techniques of peripheral nerve repair

Nerve injuries extend from simple nerve compression lesions to complete nerve injuries and severe lacerations of the nerve trunks. A specific problem is brachial plexus injuries where nerve roots can be ruptured, or even avulsed from the spinal cord, by traction. An early and correct diagnosis of a nerve injury is important. A thorough knowledge of the anatomy of the peripheral nerve trunk as well as of basic neurobiological alterations in neurons and Schwann cells induced by the injury are crucial for the surgeon in making adequate decisions on how to repair and reconstruct nerves. The technique of peripheral nerve repair includes four important steps (preparation of nerve end, approximation, coaptation and maintenance). Nerves are usually repaired primarily with sutures applied in the different tissue components, but various tubes are available. Nerve grafts and nerve transfers are alternatives when the injury induces a nerve defect. Timing of nerve repair is essential. An early repair is preferable since it is advantageous for neurobiological reasons. Postoperative rehabilitation, utilising the patients' own coping strategies, with evaluation of outcome are additional important steps in treatment of peripheral nerve injuries. in the rehabilitation phase adequate handling of pain, allodynia and cold intolerance are emphasised.

Chapter 5: Methods and protocols in peripheral nerve regeneration experimental research: part II-morphological techniques

This paper critically overviews the main procedures used for carrying out morphological analysis of peripheral nerve fibers in light, confocal, and electron microscopy. In particular, this paper emphasizes the importance of osmium tetroxide post-fixation as a useful procedure to be adopted independently from the embedding medium. In order to facilitate the use of any described techniques, all protocols are presented in full details. The pros and cons for each method are critically addressed and practical indications on the different imaging approaches are reported. Moreover, the basic rules of morpho-quantitative stereological analysis of nerve fibers are described addressing the important concepts of design-based sampling and the disector. Finally, a comparison of stereological analysis on myelinated nerve fibers between paraffin- and resin-embedded rat radial nerves is reported showing that different embedding procedures might influence the distribution of size parameters.