Regeneration and functional recovery following peripheral nerve injury

Application of Electrical Stimulation to Enhance Axon Regeneration Following Peripheral Nerve Injury

Enhancing axon regeneration is a major focus of peripheral nerve injury research. Although peripheral axons possess a limited ability to regenerate, their functional recovery is very poor. Various activity-based therapies like exercise, optical stimulation, and electrical stimulation as well as pharmacologic treatments can enhance spontaneous axon regeneration. In this protocol, we use a custom-built cuff to electrically stimulate the whole sciatic nerve for an hour prior to transection and repair. We used a Thy-1-YFP-H mouse to visualize regenerating axon profiles. We compared the regeneration of axons from nerves that were electrically stimulated to nerves that were not stimulated (untreated). Electrically stimulated nerves had longer axon growth than the untreated nerves. We detail how variations of this method can be used to measure acute axon growth.

Target-selective vertebrate motor axon regeneration depends on interaction with glial cells at a peripheral nerve plexus

A critical step for functional recovery from peripheral nerve injury is for regenerating axons to connect with their pre-injury targets. Reestablishing pre-injury target specificity is particularly challenging for limb-innervating axons as they encounter a plexus, a network where peripheral nerves converge, axons from different nerves intermingle, and then re-sort into target-specific bundles. Here, we examine this process at a plexus located at the base of the zebrafish pectoral fin, equivalent to tetrapod forelimbs. Using live cell imaging and sparse axon labeling, we find that regenerating motor axons from 3 nerves coalesce into the plexus. There, they intermingle and sort into distinct branches, and then navigate to their original muscle domains with high fidelity that restores functionality. We demonstrate that this regeneration process includes selective retraction of mistargeted axons, suggesting active correction mechanisms. Moreover, we find that Schwann cells are enriched and associate with axons at the plexus, and that Schwann cell ablation during regeneration causes profound axonal mistargeting. Our data provide the first real-time account of regenerating vertebrate motor axons navigating a nerve plexus and reveal a previously unappreciated role for Schwann cells to promote axon sorting at a plexus during regeneration.

Effects of apocynin on sciatic nerve injury in rabbits

We investigated the effects of apocynin (APO) on experimental sciatic nerve compression injury in rabbits. We used 21 male rabbits divided randomly into three groups of seven. The control group was subjected to sciatic nerve compression with no further intervention. The APO treated group was subjected to compression injury and 20 mg/kg APO was administered daily for 21 days by intraperitoneal injection beginning the day after the injury. The sham group was treated with APO without injury. The control group exhibited shrinkage of axons, disruption of myelin sheaths and loss of nerve fibers. The damage for the control group was significantly greater than for the sham group. The severity of histopathology was decreased in the APO treated group compared to the control group, as was the oxidative stress index. Our findings suggest that APO treatment may contribute to healing of sciatic nerve damage.

A glia cell dependent mechanism at a peripheral nerve plexus critical for target-selective axon regeneration

A critical step for functional recovery from peripheral nerve injury is for regenerating axons to connect with their pre-injury targets. Reestablishing pre-injury target specificity is particularly challenging for limb-innervating axons as they encounter a plexus, a network where peripheral nerves converge, axons from different nerves intermingle, and then re-sort into target-specific bundles. Here, we examine this process at a plexus located at the base of the zebrafish pectoral fin, equivalent to tetrapod forelimbs. Using live cell imaging and sparse axon labeling, we find that regenerating motor axons from three nerves coalesce into the plexus. There, they intermingle and sort into distinct branches, and then navigate to their original muscle domains with high fidelity that restores functionality. We demonstrate that this regeneration process includes selective retraction of mistargeted axons, suggesting active correction mechanisms. Moreover, we find that Schwann cells are enriched and associate with axons at the plexus, and that Schwann cell ablation during regeneration causes profound axonal mistargeting. Our data provide the first real time account of regenerating vertebrate motor axons navigating a nerve plexus and reveal a previously unappreciated role for Schwann cells to promote axon sorting at a plexus during regeneration.

Use of aerobic treadmill exercises on nerve regeneration after sciatic nerve injury in spontaneously hypertensive rats

PURPOSE

Various postoperative protocols have been proposed to improve outcomes and accelerate nerve regeneration. Recently, the use of physical exercise in a post-surgical neurorraphy procedure has shown good results when started early. We experimentally investigated the hypothesis that post-operative exercise speeds up results and improves clinical and morphologic parameters.

METHODS

Isogenic rats were randomly divided into four groups: 1 SHAM; 2 SHAM submitted to the exercise protocol (EP); 3 Grafting of the sciatic nerve; and 4 Grafting of the sciatic nerve associated with the EP. The EP was based on aerobic activities with a treadmill, with a progressive increase in time and intensity during 6 weeks. The results were evaluated by the sciatic functional index (SFI), morphometric and morphologic analysis of nerve distal to the lesion, and the number of spinal cord motor neurons, positive to the marker Fluoro-Gold (FG), captured retrogradely through neurorraphy.

RESULTS

Functional analysis (SFI) did not show a statistical difference between the group grafted with (-50.94) and without exercise (-65.79) after 90 days. The motoneurons count (Spinal cord histology) also showed no diference between these groups (834.5 × 833 respectively). Although functionally there is no difference between these groups, morphometric study showed a greater density (53.62) and larger fibers (7.762) in GRAFT group. When comparing both operated groups with both SHAM groups, all values were much lower.

CONCLUSIONS

The experimental model that this aerobic treadmill exercises protocol did not modify nerve regeneration after sciatic nerve injury and repair with nerve graft.

Neurological complications in COVID-19: a single case study of rehabilitation treatment

Background/aims:

COVID-19 is a global pandemic, which has seen over 198 million cases as of August 2021. This case study highlights the rehabilitation of a young patient with respiratory and neurologic sequalae of COVID-19 across the continuum of care, from the intensive care unit to the inpatient rehabilitation unit.

Case description:

A 45-year-old woman, with past medical history of fibromyalgia and morbid obesity, presented with complaints of shortness of breath. She tested positive for SARS-CoV-2, was transferred to the intensive care unit, and was intubated for 17 days. The day after extubation, she experienced worsened mental status; computed tomography and magnetic resonance imaging scans revealed bilateral strokes. On hospital day 21, she was transferred to the stroke step-down unit. On hospital day 24, she recovered some cognitive ability and movement of her lower extremities. On hospital day 30, she was admitted to the inpatient rehabilitation unit. Examination by occupational and physiotherapists found motor and sensory impairments of multiple peripheral nerves, including musculocutaneous, axillary and radial nerves. Interventions included passive range of motion, sitting balance, transfer training, rigid taping, upper extremity strengthening and functional training (gait, stair, activities of daily living). Her activities of daily living performance was limited by upper extremity weakness, sensory loss and pain.

Conclusions

This case highlights the medical, neurological and functional implications of COVID-19 on patients after prolonged hospitalisation. The plan of care was informed by collaboration between rehabilitation disciplines. Causes of her injuries are unclear but could include positioning, brachial plexus injuries, or post-critical illness syndrome. Further research on the evaluation and care of patients with COVID-19 that result in profound neurological impairments is warranted.

Effects of Platelet-Rich Fibrin/Collagen Membrane on Sciatic Nerve Regeneration

ABSTRACT

Alternative treatment approaches to improve the regeneration ability of damaged peripheral nerves are currently under investigation. The aim of the current study was to evaluate the effects of leucocyte/platelet-rich fibrin (L-PRF) with or without a collagen membrane as a supporter on crushed sciatic nerve healing in a rat model. Recovery of motor function and electrophysiologic measurements were evaluated at 4 weeks postoperatively. The whole number of myelinated axons, peripheral nerve axon density, average nerve fiber diameter (μm), and G-ratio were analyzed and compered among the groups. Functional, electrophysiological, and histological evaluations showed no significant difference among the groups with the exception of the L-PRF with collagen membrane groups that showed relatively positive effects on the functional and histological nerve recovery. In addition, the collagen membrane with L-PRF can be effect in nerve regeneration.

Transcriptomic differential lncRNA expression is involved in neuropathic pain in rat dorsal root ganglion after spared sciatic nerve injury

Dorsal root ganglia (DRG) neurons regenerate spontaneously after traumatic or surgical injury. Long noncoding RNAs (lncRNAs) are involved in various biological regulation processes. Conditions of lncRNAs in DRG neuron injury deserve to be further investigated. Transcriptomic analysis was performed by high-throughput Illumina HiSeq2500 sequencing to profile the differential genes in L4–L6 DRGs following rat sciatic nerve tying. A total of 1,228 genes were up-regulated and 1,415 down-regulated. By comparing to rat lncRNA database, 86 known and 26 novel lncRNA genes were found to be differential. The 86 known lncRNA genes modulated 866 target genes subject to gene ontology (GO) and KEGG enrichment analysis. The genes involved in the neurotransmitter status of neurons were downregulated and those involved in a neuronal regeneration were upregulated. Known lncRNA gene rno-Cntnap2 was downregulated. There were 13 credible GO terms for the rno-Cntnap2 gene, which had a putative function in cell component of voltage-gated potassium channel complex on the cell surface for neurites. In 26 novel lncRNA genes, 4 were related to 21 mRNA genes. A novel lncRNA gene AC111653.1 improved rno-Hypm synthesizing huntingtin during sciatic nerve regeneration. Real time qPCR results attested the down-regulation of rno-Cntnap lncRNA gene and the upregulation of AC111653.1 lncRNA gene. A total of 26 novel lncRNAs were found. Known lncRNA gene rno-Cntnap2 and novel lncRNA AC111653.1 were involved in neuropathic pain of DRGs after spared sciatic nerve injury. They contributed to peripheral nerve regeneration via the putative mechanisms.

Pattern of Mas expression in acute and post-acute stage of nerve injury in mice

Angiotensin-(1-7) (Ang [1-7]) and its receptor Mas are involved in a number of physiological processes, including control of arterial pressure and modulation of nervous system actions. However, the involvement of the Ang-(1-7)/Mas axis in peripheral nerve injury has not been investigated. Using a model of sciatic nerve injury in mice, we demonstrated opposing changes in Mas receptor expression at days 2 and 14 post-injury. Mas receptor expression was more intense 2days after the nerve lesion, compared with the intensity of the intact nerve. At this time point, the sciatic nerve functional index was -20. At day 14 after the lesion, the intensity of the immunostaining labeling in longitudinal sections of the nerve was reduced (∼30%) and the functional index increased +36 (gait improvement). In the axotomized group treated with A779 (a Mas receptor antagonist), the functional recovery index decreased in relation to the untreated axotomized group. The Mas receptor inhibitor also altered the intensity of labeling of S-100, GAP43, and IBA-1 (morphological features compatible with delayed axon growth). This study demonstrated that Ang-(1-7)/Mas axis activity was differentially modulated in the acute and post-acute stages of nerve injury.

Polymerizing Pyrrole Coated Poly (l-lactic acid-co-ε-caprolactone) (PLCL) Conductive Nanofibrous Conduit Combined with Electric Stimulation for Long-Range Peripheral Nerve Regeneration

Electrospinning and electric stimulation (ES) are both promising methods to support neuron adhesion and guide extension of neurons for nerve regeneration. Concurrently, all studies focus on either electrospinning for conduits material or ES in vitro study to accelerate nerve regeneration; few work on the combined use of these two strategies or ES in vivo study. Therefore, this study aimed to investigate the abilities of direct current ES through electrospinning conductive polymer composites composed of polypyrrole and Poly (l-lactic acid-co-ε-caprolactone) (PPY/PLCL) in peripheral nerve regeneration. PPY/PLCL composite conduits were synthesized by polymerizing pyrrole coated electrospun PLCL scaffolds. Morphologies and chemical compositions were characterized by scanning electron microscope and attenuated total reflection fourier transform infrared (ATR-FTIR) microscope. Rat pheochromocytoma 12 (PC12) cells and dorsal root ganglia (DRG) cells cultured on PPY/PLCL scaffolds were stimulated with 100 mV/cm for 4 h per day. The median neurite length and cell viability were measured in PC-12 cells. The levels of brain-derived neurotrophic factor (BDNF), glial cell derived neurotrophic factor (GDNF) and neurotrophin-3 (NT-3) were analyzed in DRG cells. In rats, 15 mm gaps of sciatic nerves were bridged using an autograft, non-stimulated PPY/PLCL conduit and PPY/PLCL conduit stimulated with 100 mV potential, respectively. A 100 mV potential direct current ES was applied for 1 h per day at 1, 3, 5 and 7 days post-implantation. The PPY/PLCL conduits with ES showed a similar performance compared with the autograft group, and significantly better than the non-stimulated PPY/PLCL conduit group. These promising results show that the PPY/PLCL conductive conduits’ combined use with ES has great potential for peripheral nerve regeneration.

3,2/-Dihydroxyflavone-Treated Pluripotent Stem Cells Show Enhanced Proliferation, Pluripotency Marker Expression, and Neuroprotective Properties

Efficient maintenance of the undifferentiated status of embryonic stem cells (ESCs) may be important for preparation of high-quality cell sources that can be successfully used for stem cell research and therapy. Here we tried to identify a compound that can enhance the quality of pluripotent stem cells. Treatment of ESCs and induced pluripotent stem cells (iPSCs) with 3,2′-dihydroxyflavone (3,2′-DHF) led to increases in cell growth, colony formation, and cell proliferation. Treatment with 3,2′-DHF resulted in high expression of pluripotency markers (OCT4, SOX2, and NANOG) and significant activation (STAT3 and AKT) or suppression (GSK3β and ERK) of self-renewal-related kinases. 3,2′-DHF-treated high-quality pluripotent stem cells also showed enhanced differentiation potential. In particular, treatment of iPSCs with 3,2′-DHF led to elevated expression of ectodermal differentiation markers and improved differentiation into fully matured neurons. Next, we investigated the in vivo effect of 3,2′-DHF-pretreated iPSCs (3,2′-DHF iPSCs) in a peripheral nerve injury model and found that transplantation of 3,2′-DHF iPSCs resulted in more efficient axonal regeneration and functional recovery than in controls. Upon histopathological and gene expression analyses, we found that transplantation of 3,2′-DHF iPSCs stimulated expression of cytokines, such as TNF-α, in the early phase of injury and successfully reduced convalescence time of the injured peripheral nerve, showing an effective neuroprotective property. Taken together, our data suggest that 3,2′-DHF can be used for more efficient maintenance of pluripotent stem cells as well as for further applications in stem cell research and therapy.

The effect of weight-bearing exercise and non-weight-bearing exercise on gait in rats with sciatic nerve crush injury

[Purpose] The purpose of this study was to access the effect of weight bearing exercise (treadmill exercise) and non-weight-bearing exercise (swimming exercise) on gait in the recovery process after a sciatic nerve crush injury. [Subjects and Methods] Rats were randomly divided into a swimming group (n=3) with non-weight-bearing exercise after a sciatic nerve crush and a treadmill group (n=3) with weight bearing exercise after a sciatic nerve crush. Dartfish is a program that can analyze and interpret motion through video images. The knee lateral epicondyle, lateral malleolus, and metatarsophalangeal joint of the fifth toe were marked by black dots before recording. [Results] There were significant differences in TOK (knee angle toe off) and ICK (knee angle at initial contact) in the swimming group and in TOK, ICA (ankle angle at initial contact), and ICK in the treadmill group. In comparison between groups, there were significant differences in TOA (ankle angle in toe off) and ICA at the 7th day. [Conclusion] There was no difference between weight bearing and non-weight-bearing exercise in sciatic nerve damage, and both exercises accelerated the recovery process in this study.

Effects of pulsed electromagnetic field and swimming exercise on rats with experimental sciatic nerve injury

[Purpose] The current study aimed to reveal the therapeutic effects of a pulsed electromagnetic field and swimming exercises on rats with experimental sciatic nerve injury, which was induced with crush-type neuropathy model damage, using electrophysiological methods. [Subjects] In the current study, the sample consisted of 28 adult male Wistar albino rats. [Methods] The rats were randomized into four groups (n=7). Swimming exercise and PEMF (2 Hz and 0.3 MT) were applied one hour a day, five days a week, for four weeks. Electroneuromyographic (ENMG) measurements were taken on day 7. [Results] When the data were evaluated, it was found that the 4 weeks of PEMF and swimming exercises led to an increase in motor conduction rates and a decrease in latency values, but the changes were not significant in comparison with the control and injury groups. The compound muscle action potential (CMAP) values of the left leg were lower in weeks 2, 3, and 4 in the swimming exercise group in comparison with the control group, although for the PEMF group, the CMAP values of the left leg reached the level observed in the control group beginning in week 3. [Conclusion] PEMF and swimming exercise made positive contributions to nerve regeneration after week 1, and regeneration was enhanced.

Nerve physiology: mechanisms of injury and recovery

Peripheral nerve injuries are common conditions, with broad-ranging groups of symptoms depending on the severity and nerves involved. Although much knowledge exists on the mechanisms of injury and regeneration, reliable treatments that ensure full functional recovery are scarce. This review aims to summarize various ways these injuries are classified in light of decades of research on peripheral nerve injury and regeneration.

ADDITION OF CONDUCTIVE ELEMENTS TO POLYMERIC SCAFFOLDS FOR MUSCLE TISSUE ENGINEERING

Cardiac and skeletal muscles are two tissues that would benefit from an electrically conductive scaffold to regenerate lost or lower functioning areas. By augmenting polymeric scaffolds with conductive elements, the contractile process for both muscles could increase. In this review, the components reviewed include polyaniline (PANi), gold (Au) nanoparticles, and carbon nanotubes (CNT). PANi has been combined with several polymers and increased the conductivity of the scaffolds. It is biocompatible, but increases mechanical properties and decreases scaffold elongation. Tissue engineering using nanoparticles is an emerging area and considerable research focuses on determining possible toxicity due to nanoparticle concentration. Contradicting data exists for both Au nanoparticles and CNT. Smaller Au nanoparticles damage cardiac tissue in vivo while larger ones do not. By comparison, in vitro data shows no harmful results for skeletal muscle cells. Data for CNT is just as diverse as the amount, orientation and further purification or functionalization could all play a role in determining biocompatibility. Future research should focus on establishing the conductivity level needed for each muscle tissue to ascertain the amount of conductive element needed so the most suitable one can be utilized.

Effects of large-area irradiated laser phototherapy on peripheral nerve regeneration across a large gap in a biomaterial conduit

This paper proposes a novel biodegradable nerve conduit comprising 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) cross-linked gelatin, annexed with β-tricalcium phosphate (TCP) ceramic particles (EDC-Gelatin-TCP, EGT). In this study, the EGT-implant site in rats was irradiated using a large-area 660 nm AlGaInP diode laser (50 mW) to investigate the feasibility of laser stimulation in the regeneration of a 15-mm transected sciatic nerve. The animals were divided into three groups: a sham-irradiated group (EGT/sham); an experimental group undergoing low-level laser (LLL) therapy (EGT/laser); a control group undergoing autologous nerve grafts (autografts). Twelve weeks after implantation, walking track analysis showed a significantly higher sciatic functional index (p < 0.05) and improved toe spreading development in the EGT/laser and autograft groups than in the EGT/sham group. In electrophysiological measurement, both the mean peak amplitude and the area under the compound muscle action potential curves in the EGT/laser and autograft groups showed significantly improved functional recovery than the EGT/sham group (p < 0.05). Compared with the EGT/sham group, the EGT/laser and autograft groups displayed a reduction in muscular atrophy. Histomorphometric assessments revealed that the EGT/laser group had undergone more rapid nerve regeneration than the EGT/sham group. The laser-treated group also presented greater neural tissue area as well as larger axon diameter and thicker myelin sheath than the tube group without the laser treatment, indicating improved nerve regeneration. Thus, these assessments demonstrate that LLL therapy can accelerate the repair of a transected peripheral nerve in rats after being bridged with EGT conduit.

Peripheral Nerve Regeneration Following Crush Injury to Rat Peroneal Nerve by Aqueous Extract of Medicinal Mushroom Hericium erinaceus (Bull.: Fr) Pers. (Aphyllophoromycetideae)

Nerve crush injury is a well-established axonotmetic model in experimental regeneration studies to investigate the impact of various pharmacological treatments. Hericium erinaceus is a temperate mushroom but is now being cultivated in tropical Malaysia. In this study, we investigated the activity of aqueous extract of H. erinaceus fresh fruiting bodies in promoting functional recovery following an axonotmetic peroneal nerve injury in adult female Sprague-Dawley rats by daily oral administration. The aim was to investigate the possible use of this mushroom in the treatment of injured nerve. Functional recovery was assessed in behavioral experiment by walking track analysis. Peroneal functional index (PFI) was determined before surgery and after surgery as rats showed signs of recovery. Histological examinations were performed on peroneal nerve by immunofluorescence staining and neuromuscular junction by combined silver-cholinesterase stain. Analysis of PFI indicated that return of hind limb function occurred earlier in rats of aqueous extract or mecobalamin (positive control) group compared to negative control group. Regeneration of axons and reinnervation of motor endplates in extensor digitorum longus muscle in rats of aqueous extract or mecobalamin group developed better than in negative control group. These data suggest that daily oral administration of aqueous extract of H. erinaceus fresh fruiting bodies could promote the regeneration of injured rat peroneal nerve in the early stage of recovery.

Large-area irradiated low-level laser effect in a biodegradable nerve guide conduit on neural regeneration of peripheral nerve injury in rats

This study used a biodegradable composite containing genipin-cross-linked gelatin annexed with β-tricalcium phosphate ceramic particles (genipin-gelatin-tricalcium phosphate, GGT), developed in a previous study, as a nerve guide conduit. The aim of this study was to analyse the influence of a large-area irradiated aluminium-gallium-indium phosphide (AlGaInP) diode laser (660 nm) on the neural regeneration of the transected sciatic nerve after bridging the GGT nerve guide conduit in rats. The animals were divided into two groups: group 1 comprised sham-irradiated controls and group 2 rats underwent low-level laser (LLL) therapy. A compact multi-cluster laser system with 20 AlGaInP laser diodes (output power, 50mW) was applied transcutaneously to the injured peripheral nerve immediately after closing the wound, which was repeated daily for 5 min for 21 consecutive days. Eight weeks after implantation, walking track analysis showed a significantly higher sciatic function index (SFI) score (P<0.05) and better toe spreading development in the laser-treated group than in the sham-irradiated control group. For electrophysiological measurement, both the mean peak amplitude and nerve conduction velocity of compound muscle action potentials (CMAPs) were higher in the laser-treated group than in the sham-irradiated group. The two groups were found to be significantly different during the experimental period (P<0.005). Histomorphometric assessments revealed that the qualitative observation and quantitative analysis of the regenerated nerve tissue in the laser-treated group were superior to those of the sham-irradiated group. Thus, the motor functional, electrophysiologic and histomorphometric assessments demonstrate that LLL therapy can accelerate neural repair of the corresponding transected peripheral nerve after bridging the GGT nerve guide conduit in rats.

Sciatic nerve regeneration in rats by a promising electrospun collagen/poly(ε-caprolactone) nerve conduit with tailored degradation rate

Background

To cope with the limitations faced by autograft acquisitions particularly for multiple nerve injuries, artificial nerve conduit has been introduced by researchers as a substitute for autologous nerve graft for the easy specification and availability for mass production. In order to best mimic the structures and components of autologous nerve, great efforts have been made to improve the designation of nerve conduits either from materials or fabrication techniques. Electrospinning is an easy and versatile technique that has recently been used to fabricate fibrous tissue-engineered scaffolds which have great similarity to the extracellular matrix on fiber structure.

Results

In this study we fabricated a collagen/poly(ε-caprolactone) (collagen/PCL) fibrous scaffold by electrospinning and explored its application as nerve guide substrate or conduit in vitro and in vivo. Material characterizations showed this electrospun composite material which was made of submicron fibers possessed good hydrophilicity and flexibility. In vitro study indicated electrospun collagen/PCL fibrous meshes promoted Schwann cell adhesion, elongation and proliferation. In vivo test showed electrospun collagen/PCL porous nerve conduits successfully supported nerve regeneration through an 8 mm sciatic nerve gap in adult rats, achieving similar electrophysiological and muscle reinnervation results as autografts. Although regenerated nerve fibers were still in a pre-mature stage 4 months postoperatively, the implanted collagen/PCL nerve conduits facilitated more axons regenerating through the conduit lumen and gradually degraded which well matched the nerve regeneration rate.

Conclusions

All the results demonstrated this collagen/PCL nerve conduit with tailored degradation rate fabricated by electrospinning could be an efficient alternative to autograft for peripheral nerve regeneration research. Due to its advantage of high surface area for cell attachment, it is believed that this electrospun nerve conduit could find more application in cell therapy for nerve regeneration in future, to further improve functional regeneration outcome especially for longer nerve defect restoration.

Avaliação do exercício físico como fator de analgesia em um modelo experimental de ciatalgia

OBJETIVO: Avaliar a eficácia do exercício físico (natação e salto) atuando na redução do quadro álgico de ratos submetidos a um modelo experimental de ciatalgia. MÉTODOS: 24 ratos Wistar foram divididos em quatro grupos: grupo Placebo (GP), grupo Natação (GN), grupo Natação 10% (GN10) e grupo Salto (GS). Todos os grupos foram submetidos ao modelo de ciatalgia e avaliados em relação à dor pós-exercício pelo teste de incapacidade funcional e pelo filamento de Von Frey. RESULTADOS: Na comparação intragrupos houve diferenças significativas, para todos os grupos, nos momentos pós-lesão comparados com o pré-lesão, por ambos os instrumentos de avaliação. Com o filamento de Von Frey observou-se diferença significativa nos grupos GN10 e GS nos momentos finais de avaliação. Na comparação intergrupos não houve diferenças significativas com nenhum instrumento de avaliação. CONCLUSÃO: O tratamento com exercício físico não foi eficaz para reduzir o quadro álgico de ratos submetidos à ciatalgia.

Thermographic evaluation of hind paw skin temperature and functional recovery of locomotion after sciatic nerve crush in rats

INTRODUCTION

Peripheral nerves are often damaged by direct mechanical injury, diseases, and tumors. The peripheral nerve injuries that result from these conditions can lead to a partial or complete loss of motor, sensory, and autonomic functions, which in turn are related to changes in skin temperature, in the involved segments of the body. The aim of this study was to evaluate the changes in hind paw skin temperature after sciatic nerve crush in rats in an attempt to determine whether changes in skin temperature correlate with the functional recovery of locomotion.

METHODS

Wistar rats were divided into three groups: control (n = 7), sham (n = 25), and crush (n = 25). All groups were subjected to thermographic, functional, and histological assessments.

RESULTS

ΔT in the crush group was different from the control and sham groups at the 1st, 3rd and 7rd postoperative days (p<0.05). The functional recovery from the crush group returned to normal values between the 3rd and 4th week post-injury, and morphological analysis of the nerve revealed incomplete regeneration at the 4th week after injury.

DISCUSSION

This study is the first demonstration that sciatic nerve crush in rats induces an increase in hind paw skin temperature and that skin temperature changes do not correlate closely with functional recovery.

Characterization of electrospun poly(L-lactide) and gold nanoparticle composite scaffolds for skeletal muscle tissue engineering

Traumatic injuries can interrupt muscle contraction by damaging the skeletal muscle and/or the peripheral nerves. The healing process results in scar tissue formation that impedes muscle function. Electrospinning and metal nanoparticles (Nps) can create a scaffold that will trigger muscle cell elongation, orientation, fusion, and striation. Poly(L-lactic acid) (PLLA) and gold (Au) Nps were electrospun to create three composite scaffolds, 7% Au-PLLA, 13% Au-PLLA and 21% Au-PLLA, and compared to PLLA alone. The scaffolds had a conductivity of 0.008 ± 0.003 S/cm for PLLA, 0.053 ± 0.015 S/cm for 7% Au-PLLA, 0.076 ± 0.004 S/cm for 13% Au-PLLA and 0.094 ± 0.037 S/cm for 21% Au-PLLA. Next, a cell study was conducted with rat primary muscle cells and all three Au-PLLA scaffolds. The first cell study showed low cell proliferation on all three of the Au-PLLA scaffolds; however, the second cell study showed that this was not due to Au Nps toxicity. Instead, low cell proliferation may be a marker for myotube differentiation and fusion. Values for the elastic modulus and yield stress for the Au-PLLA scaffolds on days 0, 7, 14, 21 and 28 were much higher than those for skeletal muscle tissue. Therefore, lower amounts of Au Nps may be utilized to create a biodegradable, biocompatible and conductive scaffold for skeletal muscle repair.

Efeito do laser de baixa intensidade (660 nm) na regeneração do nervo isquiático lesado em ratos

Os nervos periféricos são estruturas que, ao sofrerem lesões, podem originar incapacidades motoras e sensitivas importantes. O laser de baixa intensidade é um dos diversos recursos terapêuticos para promover a regeneração nervosa precoce, mas ainda não há consenso sobre sua utilização. O objetivo deste estudo foi investigar, por meio de avaliação funcional, o efeito da terapia a laser de baixa intensidade (660 nm) na regeneração do nervo isquiático após esmagamento. Foram utilizados 18 ratos (Wistar) submetidos à lesão do nervo isquiático divididos em dois grupos, controle e grupo laser, submetido ao tratamento a laser (AsGaAl, 660 nm, 10J/cm2, 30 mW e 0,06 cm²) por 21 dias no local da lesão. Para a avaliação funcional, foi aplicado o índice funcional do ciático (IFC) no pré-operatório e nos 7º, 14º e 21º dias de pós-operatório. Quando comparados o IFC dos grupos no 14o dia de pós-operatório, foi encontrada melhora significante no grupo laser em relação ao controle. Na amostra analisada e nos parâmetros utilizados, pôde-se constatar que a aplicação do laser foi eficaz na recuperação funcional precoce do nervo ciático esmagado.

Topographical distribution of motor fascicles in the sciatic-tibial nerve of the rat

Knowledge of the intraneural topography of peripheral nerves may help to improve nerve repair after injuries and the selectivity of neural interfaces. We studied the fascicular pattern of motor fibers of the rat sciatic-tibial nerve. We carried out an anatomical dissection of the muscular tributaries of the tibial nerve in the leg. Immunohistochemistry against choline acetyltransferase was used to identify motor axons. Retrograde tracing allowed localization of the muscular fascicles at proximal levels of the sciatic trunk. The distribution of motor fibers in transverse section of the tibial nerve is not homogeneous; two clusters were identified, each one containing fibers of functionally related muscles. Retrograde tracing allowed for the identification of motor fascicles, each one well localized along the sciatic nerve. In the rat there is a somatotopic organization of the sciatic nerve, with muscular fascicles maintaining the same relative position along the entire nerve.

Comparative effects of wavelengths of low-power laser in regeneration of sciatic nerve in rats following crushing lesion

Peripheral nerves are structures that, when damaged, can result in significant motor and sensory disabilities. Several studies have used therapeutic resources with the aim of promoting early nerve regeneration, such as the use of low-power laser. However, this laser therapy does not represent a consensus regarding the methodology, thus yielding controversial conclusions. The objective of our study was to investigate, by functional evaluation, the comparative effects of low-power laser (660 nm and 830 nm) on sciatic nerve regeneration following crushing injuries. Twenty-seven Wistar rats subjected to sciatic nerve injury were divided into three groups: group sham, consisting of rats undergoing simulated irradiation; a group consisting of rats subjected to gallium-aluminum-arsenide (GaAlAs) laser at 660 nm (10 J/cm(2), 30 mW and 0.06 cm(2) beam), and another one consisting of rats subjected to GaAlAs laser at 830 nm (10 J/cm(2), 30 mW and 0.116 cm(2)). Laser was applied to the lesion for 21 days. A sciatic functional index (SFI) was used for functional evaluation prior to surgery and on days 7, 14, and 21 after surgery. Differences in SFI were found between group 660 nm and the other ones at the 14th day. One can observe that laser application at 660 nm with the parameters and methods utilised was effective in promoting early functional recovery, as indicated by the SFI, over the period evaluated.

Laser de baixa intensidade (830 nm) na recuperação funcional do nervo isquiático de ratos

OBJETIVO: Avaliar o efeito do laser de baixa intensidade na melhora funcional da marcha de ratos após esmagamento do nervo ciático. MÉTODOS: Foram utilizados 18 ratos divididos alea-to-riamente em dois grupos: controle (sham) e irradiado com densidade de energia de 40J/cm², em 21 dias consecutivos, utilizando o laser 830nm (AsGaAl). Os animais foram submetidos ao esmagamento do nervo ciático direito com o dispositivo portátil de peso morto e avaliados pelo "Índice Funcional do Ciático" (IFC). As pegadas foram coletadas no pré-operatório, 7º, 14º e 21º dias pós-operatório. RESULTADOS: Os resultados do IFC foram significantes quando comparados os grupos no 7º e 14º dia pós-operatório (p<0,05). No 21º dia pós-operatório não houve diferença entre os grupos. Na avaliação intra-grupos houve diferença entre todas as semanas avaliadas (p<0,01). Os animais irradiados apresentaram melhora no padrão da marcha, demonstrada pelos valores do IFC nos períodos iniciais, mas ao final das 3 semanas, houve uma recuperação similar. CONCLUSÃO: A laserterapia de baixa intensidade mostrou ser eficaz no estímulo da aceleração da regeneração nervosa do ciático de ratos após esmagamento.

Neural cell transplantation effects on sciatic nerve regeneration after a standardized crush injury in the rat

The goal of the present study was to assess whether in vitro-differentiated N1E-115 cells supported by a collagen membrane would enhance rat sciatic nerve regeneration after a crush injury. To set up an appropriate experimental model for investigating the effects of neural cell transplantation, we have recently described the sequence of functional and morphologic changes occurring after a standardized sciatic nerve crush injury with a nonserrated clamp. Functional recovery was evaluated using the sciatic functional index, the static sciatic index, the extensor postural thrust, the withdrawal reflex latency, and ankle kinematics. In addition, histomorphometric analysis was carried out on regenerated nerve fibers by means of the 2D-disector method. Based on the results of the EPT and of some of the ankle locomotor kinematic parameters analyzed, the hypothesis that N1E-115 cells may enhance nerve regeneration is partially supported although histomorphometry disclosed no significant difference in nerve fiber regeneration between the different experimental groups. Therefore, results suggest that enrichment of equine type III collagen membrane with the N1E-115 cellular system in the rat sciatic nerve crush model may support recovery, at least in terms of motor function. The discrepancy between functional and morphological results also suggests that the combined use of functional and morphological analysis should be recommended for an overall assessment of recovery in nerve regeneration studies.

Influence of laser (660 nm) on functional recovery of the sciatic nerve in rats following crushing lesion

With the aim of accelerating the regenerative processes, the objective was to study the influence of gallium-aluminum-arsenide (GaAlAs) laser (660 nm) on functional and histomorphological recovery of the sciatic nerve in rats. The sciatic nerves of 12 Wistar rats were crushed divided into two groups: control and laser therapy. For the latter, GaAlAs laser was utilized (660 nm, 4 J/cm(2), 26.3 mW and 0.63 cm(2) beam), at three equidistant points on the lesion, for 20 days. Comparison of the sciatic functional index (SFI) showed that there was a significant difference only between the pre-lesion value of the laser therapy group and that after the 21st day in the control group. It was concluded that the parameters and methods utilized demonstrated positive results regarding the SFI over the time period evaluated.

Effect of laser therapy (660 nm) on recovery of the sciatic nerve in rats after injury through neurotmesis followed by epineural anastomosis

The aim of this study was to analyze the influence of aluminum gallium arsenide (AlGaAs) laser (660 nm) on the myelin sheath and functional recovery of the sciatic nerve in rats. The sciatic nerves of 12 Wistar rats were subjected to injury through neurotmesis and epineural anastomosis, and the animals were divided into two groups: group 1 was the control and group 2, underwent low-level laser therapy (LLLT). After the injury, AlGaAs laser at 660 nm, 4 J/cm(2), 26.3 mW and beam area of 0.63 cm(2) was administered to three equidistant points on the injury for 20 consecutive days. In the control group the mean area of the myelin impairment was 0.51 (+/- 0.11) on day 21 after the operation, whereas this value was 1.31 (+/- 0.22) in the LLLT group. Student's t-test revealed a P value = 0.0229 for the mean area values of the myelin sheath between the LLLT and control groups. Comparison of the sciatic functional index (SFI) showed that there was no significant difference between the pre-lesion value in the laser therapy group and the control group. The use of AlGaAs laser (660 nm) provided significant changes to the morphometrically assessed area of the myelin sheath, but it did not culminate in positive results for functional recovery in the sciatic nerve of the rats after injury through neurotmesis.

Long-term functional and morphological assessment of a standardized rat sciatic nerve crush injury with a non-serrated clamp

We have recently described the sequence of functional and morphologic changes occurring after a standardized sciatic nerve crush injury. An 8-week post-injury time was used because this end point is the far most used. Unexpectedly, both functional and morphological data revealed that animals had still not recovered to normal pre-injury levels. Therefore, the present study was designed in order to prolong the observation up to 12 weeks. Functional recovery was evaluated using sciatic functional index (SFI), static sciatic index (SSI), extensor postural thrust (EPT), withdrawal reflex latency (WRL) and ankle kinematics. In addition, quantitative morphology was carried out on regenerated nerve fibers. A full functional recovery was predicted by SFI/SSI, EPT and WRL but not all ankle kinematics parameters. Moreover, only two morphological parameters (myelin thickness/axon diameter ratio and fiber/axon diameter ratio) returned to normal values. Data presented in this paper provide a baseline for selecting the adequate end-point and methods of recovery assessment for a rat sciatic nerve crush study and suggest that the combined use of functional and morphological analysis should be recommended in this experimental model.

Interaction of cells and nanofiber scaffolds in tissue engineering

Nanofibers and nanomaterials are potentially recent additions to materials in relation to tissue engineering (TE). TE is the regeneration of biological tissues through the use of cells, with the aid of supporting structures and biomolecules. Mimicking architecture of extracellular matrix is one of the challenges for TE. Biodegradable biopolymer nanofibers with controlled surface and internal molecular structures can be electrospun into mats with specific fiber arrangement and structural integrity for drug delivery and TE applications. The polymeric materials are widely accepted because of their ease of processability and amenability to provide a large variety of cost-effective materials, which help to enhance the comfort and quality of life in modern biomedical and industrial society. Today, nanotechnology and nanoscience approaches to scaffold design and functionalization are beginning to expand the market for drug delivery and TE is forming the basis for highly profitable niche within the industry. This review describes recent advances for fabrication of nanofiber scaffolds and interaction of cells in TE.