Lack of association between outcome measures of nerve regeneration

Evaluation of combined effects of brief electrical stimulation and Schwann-like cells on sciatic nerve injury model

Severe nerve injuries can be treated with electrical stimulation and stem cell therapies, but little is known about the potential benefits of combining these two treatments. In an effort to investigate this combination, we conducted a study to evaluate the effectiveness of electrical stimulation and Schwann-like cell transplantation in female Wistar albino rats. Our study consisted of five groups of rats: a sham group, an injury group, an electrical stimulation group, a Schwann-like cell group, and a combination group. The experimental groups received electrical stimulation, Schwann-like cell transplantation, or both. The animals sciatic function index was evaluated during a 6-week recovery period, and nerve conduction velocity, wet muscle mass, and nerve tissues were also analyzed. The results of the study showed that all experimental groups had a faster functional recovery compared to the injury group, although the difference between groups was not statistically significant. Both the combination group and the Schwann-like cell transplantation group had a higher nerve conduction velocity compared to the other experimental groups. However, there was no significant difference between the combination and Schwann-like cell transplantation groups. Nonetheless, histological analysis showed a better axonal reorganization in the combination group. The study provides preliminary evidence of the potential benefits of combining electrical stimulation and Schwann-like cell transplantation in treating severe nerve injuries. However, further studies with larger sample sizes are needed to confirm these findings and optimize the treatment parameters.

Biomechanical microenvironmental stimulating effect of pulsed electromagnetic field on the regeneration of crush injured rat sciatic nerve

This study evaluated the biomechanical microenvironmental stimulating effect of pulsed electromagnetic field (PEMF) on the regeneration of crush-injured rat sciatic nerve, when combined with bone marrow mesenchymal stem cells (BMSCs) and recombinant human nerve growth factor (rhNGF-β), in the form of an adenoviral vector-mediated NGF. Sprague-Dawley rats were equally distributed into six groups; PBS, BMSC, NGF-Ad + BMSC, PEMF + PBS, PEMF + BMSC and PEMF + NGF-Ad + BMSC. The PBS group received PBS (volume: 10μL/rat), the BMSC group with BMSCs (1 × 106 cell/10 μL/rat) and NGF-Ad group with the rhNGF-β Ad infected BMSCs (1 × 106 cell/10 μL/rat) immediate after right sciatic nerve crush injury. The PEMF groups were exposed to PEMF of 1mT, 50 Hz, 1 h/day. The rats were observed for 3 weeks. PEMF alone did not showed the positive effect compared with negative control group. The groups transplanted with BMSCs showed higher axonal regeneration compared with the groups without transplantation of the cells whether BMSC was infected with NGF-Ad or not and whether the animals received PEMF. PEMF + NGF-Ad + BMSC group showed the significantly highest number of axons than the other groups. Functionally, all groups showed marked improvement at 3 weeks postoperatively although the difference was not statistically significant among the groups. PEMF showed the positive effect when combined with BMSC and NGF-ad in aspect of number of axons. Therefore, combining the microenvironment stimulation methods of PEMF and conventional methods such as transplantation of stem cells and growth factor could be considered for the regeneration methods in the nerve damage.

Peripheral nerve regeneration in rats using nerve graft in a vein conduit pre-filled with platelet-rich fibrin (PRF)

Treatment of peripheral nerve injury is not always satisfactory. To improve results, specific adjuvant methods have been used, such as platelet-rich fibrin (PRF) and vein conduits. The goal of this study was to assess whether use of PRF and vein conduits after nerve suture improves nerve regeneration as measured by a functional score and histomorphometry analysis. Ten isogenic spontaneously hypertensive rats were randomly assigned to 4 experimental procedures: 1) Sham group (n = 10); 2) Nerve graft (NG) group (n = 10); 3) Nerve graft covered with a vein conduit (NGVC) (n = 10); and 4) Nerve graft covered with a vein conduit pre-filled with PRF (NGVCP) (n = 10). Nerve repair results were evaluated on: sciatic functional index (SFI) at 0, 30, 60 and 90 days; morphometric and morphologic analysis of the distal nerve; and histological analysis of Fluoro-Gold® stained motor neurons in the anterior horn of the spinal cord. Compared to the Sham control group, the NGVC and NGVCP groups exhibited lower SFI on all measures. The NGVC group showed improvement in SFI at day 90, which was significant compared to the NG group. Fiber and axon diameters were comparable in the NGVC and NGVCP groups, which were both significantly lower than in the Sham and NG groups. Significant improvement was expected with PRF, but in fact the release of factors from this substance was not as effective as hoped.

Functional Gait Assessment Using Manual, Semi-Automated and Deep Learning Approaches Following Standardized Models of Peripheral Nerve Injury in Mice

Objective: To develop a standardized model of stretch−crush sciatic nerve injury in mice, and to compare outcomes of crush and novel stretch−crush injuries using standard manual gait and sensory assays, and compare them to both semi-automated as well as deep-learning gait analysis methods. Methods: Initial studies in C57/Bl6 mice were used to develop crush and stretch−crush injury models followed by histologic analysis. In total, 12 eight-week-old 129S6/SvEvTac mice were used in a six-week behavioural study. Behavioral assessments using the von Frey monofilament test and gait analysis recorded on a DigiGait platform and analyzed through both Visual Gait Lab (VGL) deep learning and standardized sciatic functional index (SFI) measurements were evaluated weekly. At the termination of the study, neurophysiological nerve conduction velocities were recorded, calf muscle weight ratios measured and histological analyses performed. Results: Histological evidence confirmed more severe histomorphological injury in the stretch−crush injured group compared to the crush-only injured group at one week post-injury. Von Frey monofilament paw withdrawal was significant for both groups at week one compared to baseline (p < 0.05), but not between groups with return to baseline at week five. SFI showed hindered gait at week one and two for both groups, compared to baseline (p < 0.0001), with return to baseline at week five. Hind stance width (HSW) showed similar trends as von Frey monofilament test as well as SFI measurements, yet hind paw angle (HPA) peaked at week two. Nerve conduction velocity (NCV), measured six weeks post-injury, at the termination of the study, did not show any significant difference between the two groups; yet, calf muscle weight measurements were significantly different between the two, with the stretch−crush group demonstrating a lower (poorer) weight ratio relative to uninjured contralateral legs (p < 0.05). Conclusion: Stretch−crush injury achieved a more reproducible and constant injury compared to crush-only injuries, with at least a Sunderland grade 3 injury (perineurial interruption) in histological samples one week post-injury in the former. However, serial behavioral outcomes were comparable between the two crush groups, with similar kinetics of recovery by von Frey testing, SFI and certain VGL parameters, the latter reported for the first time in rodent peripheral nerve injury. Semi-automated and deep learning-based approaches for gait analysis are promising, but require further validation for evaluation in murine hind-limb nerve injuries.

Electrophysiological, biomechanical, and finite element analysis study of sacral nerve injury caused by sacral fracture

Background: We aimed to study the mechanism of sacral nerve injury caused by sacral fractures and the relationship between nerve decompression and nerve function.

Methods: First, we observed the anatomical features of lumbosacral nerve root region in Sprague-Dawley rats. Next, the rats were divided into the sham, 10 g, 30 g, and 60 g groups for electrophysiological studies on nerve root constriction injury. Then we studied the biomechanical properties of rat nerve roots, lumbosacral trunk, and sacrum. Finally, we established a finite element analysis model of sacral nerve roots injury in rats and determined the correlation between sacral deformation and the degree of sacral nerve roots injury.

Result: Anatomical study showed L5 constitutes sciatic nerve, the length of the L5 nerve root is 3.67 ± 0.15 mm, which is suitable for electrophysiological research on nerve root compression injury. After a series of electrophysiological study of L5 nerve roots, our results showed that nerve root function was almost unaffected at a low degree of compression (10 g). Nerve root function loss began at 30 g compression, and was severe at 60 g compression. The degree of neurological loss was therefore positively correlated with the degree of compression. Combining biomechanical testing of the lumbosacral nerve roots, finite element analysis and neuroelectrophysiological research, we concluded when the sacral foramina deformation is &gt;22.94%, the sacral nerves lose function. When the compression exceeds 33.16%, early recovery of nerve function is difficult even after decompression.

Conclusion: In this study, we found that the neurological loss was positively correlated with the degree of compression. After early decompression, nerve root function recovery is possible after moderate compression; however, in severe compression group, the nerve function would not recover. Furthermore, FEA was used to simulate nerve compression during sacral fracture, as well as calculate force loading on nerve with different deformation rates. The relationship between sacral fractures and neurological loss can be analyzed in combination with neurophysiological test results.

Comparison between normal and reverse orientation of graft in functional and histomorphological outcomes after autologous nerve grafting: An experimental study in the mouse model

BACKGROUND

Autologous nerve grafting has been considered the gold standard for the treatment of irreparable nerve gaps. However, the choice of effective proximodistal orientation of autografts (normal or reversed) is controversial. Therefore, we compared functional and histological outcomes between normal and reversed orientations of autografts in a mouse sciatic nerve model.

MATERIALS AND METHODS

Thirty C57BL/6J mice weighing 20-25 g were assigned to the donor, normally oriented autograft, and reverse-oriented autograft groups (n = 10 per group). A 10-mm section of the sciatic nerve was harvested from a donor mouse. Half the harvested nerve was grafted onto an irreparable gap in a recipient mouse using either a normal or reversed orientation. The sciatic functional index (SFI) was measured biweekly for up to 12 weeks postoperatively. Morphological analysis was performed using immunofluorescence staining for neurofilament (NF) and myelin protein zero (P0) in cross-sectional and whole-mount nerve preparations in 12 weeks postoperatively. Additionally, morphological analysis of the tibialis anterior muscle was performed using hematoxylin and eosin staining. NF or P0-expressing axons were counted and cross-sectional area (CSA) and minimum Feret's diameter of myofibers were measured.

RESULTS

The SFI recovered gradually up to 12 weeks after autografting, but there were no significant differences in the SFI between the normal and reversed orientations. The number of NF-expressing axons in center of graft was significantly higher in the normal orientation than in the reversed orientation (P < .05). However, there were no significant differences in the number and mean intensity of P0-expressing axons between the orientations. The CSA of myofibers was significantly larger in the normal orientation than in the reversed orientation (P < .05).

CONCLUSIONS

Normally oriented autografts promote axonal regrowth and prevent neurogenic muscular atrophy compared with reverse-oriented autografts. However, despite these positive histomorphometric effects, the proximodistal orientation of the autograft does not affect functional outcomes.

Histomorphometry in Peripheral Nerve Regeneration: Comparison of Different Axon Counting Methods

BACKGROUND

Histomorphometry quantitatively evaluates nerve regeneration. Total myelinated fiber count (TMFC) is most accurately obtained manually across full nerve cross-sections, but most researchers opt for automated, sampled analysis. Few of the numerous techniques available have been validated. The goal of this study was to compare common histomorphometric methods (full manual [FM], sampled manual [SM], and sampled automatic [SA]) to determine their reliability and consistency.

MATERIAL AND METHODS

Twenty-four rats underwent sciatic nerve (SN) repair with 20mm isografts; SNs distal to the graft were analyzed. TMFC was manually determined in each full cross-section. Counts were also extrapolated from sampled fields, both manually and automatically with ImageJ software. Myelinated fiber diameter, axon diameter, and myelin sheath thickness were measured manually in full and sampled fields; G-ratio was calculated. Repeated-measures MANOVA, Spearman correlation, and Wilcoxon signed-rank tests were performed. A systematic review of histomorphometry in rat SN repair was performed to analyze the variability of techniques in the literature.

RESULTS

FM TMFC was 13,506 ± 4,217. Both sampled methods yielded significantly different TMFCs (SM:14.4 ± 13.4%, P< 0.001; SA:21.8 ± 44.7%, P = 0.037). All three methods strongly correlated with each other, especially FM and SM (r_s = 0.912, P< 0.001). FM fiber diameter, axon diameter, and myelin sheath thickness did not differ from SM (P = 0.493, 0.209, and 0.331, respectively). 65% of papers used sampling; 78% utilized automated or semi-automated analysis. Software, sampling, and histomorphometric parameters varied widely.

CONCLUSION

SM and SA analysis are reliable with standardized, systematic sampling. Transparency is essential to allow comparison of data; meanwhile, researchers must be cognizant of the wide variety of methodologies in the literature.

Performance of Schwann cell transplantation into extracted socket after inferior alveolar nerve injury in a novel rat model

An inferior alveolar nerve (IAN) injury is a common clinical problem that can affect a patients' quality of life. Cellular therapy has been proposed as a promising treatment for this injury. However, the current experimental models for IAN injury require surgery to create bone windows that expose the nerve, and these models do not accurately mimic human IAN injuries. Therefore, in this study, a novel experimental model for IAN injury has been established in rats. Using this model, the effects of Schwann cells and their role in the recovery from IAN injuries were investigated. Schwann cells were isolated from rat sciatic nerves and cultured. The first molar in the mandible was extracted and the IAN was immediately injured for 30 min by inserting an insect pin. Then, the Schwann cells or culture medium were transplanted into the extracted sockets of the cell and injury groups, respectively. After the surgery, the cell group displayed significantly increased sensory reflexes in response to mechanical stimulation, regenerated IAN width, and myelin basic protein-positive myelin sheaths when compared with the injury group. In conclusion, a novel animal experimental model for IAN injury has been developed that does not require the creation of a bone window to evaluate the impacts of cell transplantation and demonstrates that Schwann cell transplantation facilitates the regeneration of injured IANs.

Composite nanofibers incorporating alpha lipoic acid and atorvastatin provide neuroprotection after peripheral nerve injury in rats

Despite the new treatment strategies within the last 30 years, peripheral nerve injury (PNI) is still a worldwide clinical problem. The incidence rate of PNIs is 1 in 1000 individuals per year. In this study, we designed a composite nanoplatform for dual therapy in peripheral nerve injury and investigated the in-vivo efficacy in rat sciatic nerve crush injury model. Alpha-lipoic acid (ALA) was loaded into poly lactic-co-glycolic acid (PLGA) electrospun nanofibers which would release the drug in a faster manner and atorvastatin (ATR) loaded chitosan (CH) nanoparticles were embedded into PLGA nanofibers to provide sustained release. Sciatic nerve crush was generated via Yasargil aneurism clip with a holding force of 50 g/cm². Nanofiber formulations were administered to the injured nerve immediately after trauma. Functional recovery of operated rat hind limb was evaluated using the sciatic functional index (SFI), extensor postural thrust (EPT), withdrawal reflex latency (WRL) and Basso, Beattie, and Bresnahan (BBB) test up to one month in the post-operative period at different time intervals. In addition to functional recovery assessments, ultrastructural and biochemical analyses were carried out on regenerated nerve fibers. L-929 mouse fibroblast cell line and B35 neuroblastoma cell line were used to investigate the cytotoxicity of nanofibers before in-vivo experiments. The neuroprotection potential of these novel nanocomposite fiber formulations has been demonstrated after local implantation of composite nanofiber sheets incorporating ALA and ATR, which contributed to the recovery of the motor and sensory function and nerve regeneration in a rat sciatic nerve crush injury model.

Fabrication and transplantation of chitosan-selenium biodegradable nanocomposite conduit on transected sciatic nerve: a novel study in rat model

Purpose: The improvement of techniques using conduits that connects the ends of damaged nerves and guides the growth of nerve fibers between the stumps, including adoption of natural or synthetic materials still is a challenge in peripheral nerve repair. The aim of the present novel study was to fabricate and transplant chitosan-selenium biodegradable nanocomposite conduit on transected sciatic nerve in rat model.Methods: In NORMAL group, the left sciatic nerve was exposed through a gluteal muscle incision and after careful hemostasis skin was closed. In TRANSECTED group left sciatic nerve was transected and stumps were fixed in adjacent muscle. In CHITOSAN and CSBNC groups, 10-mm sciatic nerve defects were bridged using a chitosan and chitosan-selenium biodegradable nanocomposite conduits, respectively. The regenerated fibers were studied 4, 8 and 12 weeks after surgery. Assessment of nerve regeneration was based on behavioral, functional, biomechanical, histomorphometric and immunohistochemical criteria.Results: The behavioral, functional and biomechanical studies confirmed significant recovery of regenerated axons in CSBNC group (P < 0.05). Quantitative morphometric analyses of regenerated fibers showed the number and diameter of myelinated fibers in CSBNC group were significantly higher than in the CHITOSAN group (P < 0.05).Discussion: This demonstrates the potential of using CSBNC in peripheral nerve regeneration without limitations of donor-site morbidity associated with isolation autograft. It is also cost saving and may have clinical implications for the surgical management of patients after facial nerve transection.

Efficacy of Human Cell-Seeded Muscle-Stuffed Vein Conduit in Rat Sciatic Nerve Repair

We investigated the efficacy of a muscle-stuffed vein (MSV) seeded with neural-transdifferentiated human mesenchymal stem cells as an alternative nerve conduit to repair a 15-mm sciatic nerve defect in athymic rats. Other rats received MSV conduit alone, commercial polyglycolic acid conduit (Neurotube^®), reverse autograft, or were left untreated. Motor and sensory functions as well as nerve conductivity were evaluated for 12 weeks, after which the grafts were harvested for histological analyses. All rats in the treatment groups demonstrated a progressive increase in the mean Sciatic Functional Index (motor function) and nerve conduction amplitude (electrophysiological function) and showed positive withdrawal reflex (sensory function) by the 10th week of postimplantation. Autotomy, which is associated with neuropathic pain, was severe in rats treated with conduit without cells; there was mild or no autotomy in the rats of other groups. Histologically, harvested grafts from all except the untreated groups exhibited axonal regeneration with the presence of mature myelinated axons. In conclusion, treatment with MSV conduit is comparable to that of other treatment groups in supporting functional recovery following sciatic nerve injury; and the addition of cells in the conduit alleviates neuropathic pain. Impact Statement It is shown that pretreated muscle-stuffed vein conduit is comparable to that of commercial nerve conduit and autograft in supporting functional recovery following peripheral nerve injury. The addition of neural-differentiated mesenchymal stem cells in the conduit is shown to alleviate neuropathic pain.

Brachial plexus nerve injury and repair in a rabbit model part II: Does middle trunk injury result in loss of biceps function while repair results in recovery of biceps function

INTRODUCTION

There is conflicting anatomic and innervation data regarding the rabbit brachial plexus injury model. This study aims to validate a rabbit brachial plexus injury model. We hypothesize the middle trunk (C6, C7) is the primary innervation of the biceps, and when cut and unrepaired, would demonstrate lack of recovery and when repaired would demonstrate evidence of recovery.

MATERIALS AND METHODS

Twenty two male New Zealand white rabbits (3-4 kg) underwent unilateral surgical division of the middle trunk. Five rabbits were randomly assigned to the "no-repair" group while the remaining 17 rabbits underwent direct coaptation ("repair" group). Rabbits were followed for 12 weeks, with ultrasound measurement of biceps cross-sectional area performed preoperatively, and at 4, 8, and 12 weeks postoperatively. At a euthanasia procedure, bilateral compound muscle action potential (CMAP) and isometric tetanic force (ITF) were measured. Bilateral biceps muscles were harvested and wet muscle weight was recorded. The operative side was expressed as a percentage of the non-operated side, and differences between the no repair and repair rabbits were statistically compared.

RESULTS

The repair group demonstrated significantly higher CMA (23.3 vs. 0%, p < .05), ITF (25.6 vs. 0%, p < .05), and wet muscle weight (65.8 vs. 52.0%, p < .05) as compared to the unrepaired group. At 4 weeks postoperatively, ultrasound-measured cross-sectional area of the biceps demonstrated atrophy in both groups. At 12 weeks, the repair group had a significantly larger cross-sectional area as compared to the no-repair group (89.1 vs. 59.3%, p < .05).

CONCLUSIONS

This injury model demonstrated recovery with repair and lack of function without repair. Longer survival time is recommended for future investigations.

RGD-Modified Nanofibers Enhance Outcomes in Rats after Sciatic Nerve Injury

Nerve injuries requiring surgery are a significant problem without good clinical alternatives to the autograft. Tissue engineering strategies are critically needed to provide an alternative. In this study, we utilized aligned nanofibers that were click-modified with the bioactive peptide RGD for rat sciatic nerve repair. Empty conduits or conduits filled with either non-functionalized aligned nanofibers or RGD-functionalized aligned nanofibers were used to repair a 13 mm gap in the rat sciatic nerve of animals for six weeks. The aligned nanofibers encouraged cell infiltration and nerve repair as shown by histological analysis. RGD-functionalized nanofibers reduced muscle atrophy. During the six weeks of recovery, the animals were subjected to motor and sensory tests. Sensory recovery was improved in the RGD-functionalized nanofiber group by week 4, while other groups needed six weeks to show improvement after injury. Thus, the use of functionalized nanofibers provides cues that aid in in vivo nerve repair and should be considered as a future repair strategy.

Functional evaluation outcomes correlate with histomorphometric changes in the rat sciatic nerve crush injury model: A comparison between sciatic functional index and kinematic analysis

Elucidating whether there is a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would contribute to an accurate evaluation of the regeneration state without sacrificing animals. The gold standard for functional evaluation is the sciatic functional index (SFI) despite there being intrinsic shortcomings. Kinematic analysis is considered a reliable and sensitive approach for functional evaluation, most commonly assessed as ankle angle at various phases of a gait cycle. Studies utilizing the toe angle for functional evaluation are scarce, and changes in the toe angle following surgery remain unknown. The present study assessed correlations of ankle angle, toe angle and SFI with histomorphometric data, aiming to determine which parameters most accurately reflect changes in histomorphometric data over time. Six Lewis rats were designated as the control group. 30 animals received surgery, six of them were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the “toe-off” phase, and for evaluation of SFI. Histomorphometric analysis were also performed, to determine the number of myelinated nerve fibers, diameters of myelinated nerve fibers, axon diameters, and myelin sheath thicknesses. Furthermore, we investigated changes in ankle angle, toe angle, SFI, and histomorphometric data over time, as well as correlations between ankle angle, toe angle, and SFI with histomorphometric data. The results revealed that changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data in the rat sciatic nerve crush injury model. Toe angle reflected changes in histomorphometric data with time more precisely than ankle angle or SFI did, and ankle angle was a better prognostic parameter than SFI.

The effect of full dose composite tissue allotransplantation immunosuppression on allograft motor nerve regeneration in a rat sciatic nerve model

BACKGROUND

The purpose of this study was to identify which triple immunosuppressive protocols, currently used for vascularized composite allotransplantation in the clinic, will have the best effect on motor function recovery following nerve allograft reconstruction.

METHODS

Eighty-eight Lewis rats underwent a 1-cm sciatic nerve allograft transplantation and skin graft from 44 Brown-Norway rats. Group I received 0.9% isotonic saline (control); Group II, 2 mg/kg FK506; Group III, 1 mg/kg FK506 with 15 mg/kg mycophenolate mofetil (MMF); and Group IV, 2 mg/kg FK506 with 30 mg/kg MMF and prednisone. Each group consisted of 11 rats. After 12 weeks, motor function recovery was evaluated with isometric tetanic force, muscle mass, ankle contracture angle, electrophysiology, and nerve histomorphometry. Adequacy of immunosuppression was monitored with the transplanted skin graft. All data are expressed as a percentage of the contralateral side.

RESULTS

Isometric tetanic force showed significantly better functional recovery in all groups treated with immunosuppression compared to control. Within the immunosuppression groups no significant difference was found: 42.1 ± 6.4% (Group I), 56.1 ± 12.4% (Group II), 58.4 ± 10.7% (Group III), and 61.3 ± 11.2% (Group IV). Group IV was superior to all other groups regarding ankle contracture (P < .05) and electrophysiology (P < .001). Skin graft rejection occurred in 41 and 0% (Groups III and IV, respectively).

CONCLUSIONS

FK506 significantly enhanced motor recovery after allograft reconstruction. This effect was comparable between combination treatment (low-dose FK506 and MMF) and triple therapy (high-dose FK506 and MMF plus prednisolone). However, triple therapy was more effective in suppressing skin rejection.

The effect of in vivo created vascularized neurotube on peripheric nerve regeneration

INTRODUCTION

Creating vascularized nerve conduits for treatment of nerve gaps have been researched, however, these methods need microsurgical anastomosis thereby complicating the nerve repair process. Thus, the concept of vascularized nerve conduits has not popularized up till now. The aim of this study is to evaluate the effects of vascularized and non-vascularized biological conduits on peripheral nerve regeneration.

MATERIAL AND METHODS

Following ethical board approval, 15 Sprague-Dawley rats were used in the study. The rats were equally divided into three groups. In group I, a silicon rod was inserted next to the sciatic nerve of the rat and connective tissue generated around this rod was used as a vascularized biological conduit. In group II, a silicon rod was inserted into the dorsum of the rat and connective tissue generated around this rod was used as a non-vascularized biological conduit. In group III, autogenic nerve graft was used to repair the nerve gap. The contralateral sciatic nerve is used as a control in all rats. Macroscopic, electrophysiological and histomorphometric evaluations were performed to determine the nerve regeneration.

RESULTS

There was no statistically significant difference between groups, in terms of latency. However, the mean amplitude of group I was found to be higher than other groups. The difference between group I and II was statistically significant. Myelinated axonal counts in group I was significantly higher than groups II and III.

CONCLUSION

Our results showed that vascularized biological conduits provided better nerve regeneration when compared to autografts and non-vascularized biological conduits. Creation and application of vascularized conduits by using the technique described here is easy. Although this method is not an alternative to autogenic nerve grafts, our results are promising and encouraging for further studies.

Validity and reliability of the CatWalk system as a static and dynamic gait analysis tool for the assessment of functional nerve recovery in small animal models

INTRODUCTION

A range of behavioral testing paradigms have been developed for the research of central and peripheral nerve injuries with the help of small animal models. Following any nerve repair strategy, improved functional outcome may be the most important evidence of axon regeneration. A novel automated gait analysis system, the CatWalk^™, can measure dynamic as well as static gait patterns of small animals. Of most interest in detecting functional recovery are in particular dynamic gait parameters, coordination measures, and the intensity of the animals paw prints. This article is designed to lead to a more efficient choice of CatWalk parameters in future studies concerning the functional evaluation of nerve regeneration and simultaneously add to better interstudy comparability.

METHODS

The aims of the present paper are threefold: (1) to describe the functional method of CatWalk gait analysis, (2) to characterize different parameters acquired by CatWalk gait analysis, and to find the most frequently used parameters as well as (3) to compare their reliability and validity throughout the different studies.

RESULTS

In the reviewed articles, the most frequently used parameters were Swing Duration (30), Print Size (27), Stride Length (26), and Max Contact Area (24). Swing Duration was not only frequently used but was also the most reliable and valid parameter. Therefore, we hypothesize that Swing Duration constitutes an important parameter to be chosen for future studies, as it has the highest level of reliability and validity.

CONCLUSION

In conclusion, CatWalk can be used as a complementary approach to other behavioral testing paradigms to assess clinically relevant behavioral benefits, with the main advantage that this system demonstrates both static and dynamic gait parameters at the same time. Due to limited reliability and validity of certain parameters, we recommend that only the most frequently assessed parameters should be used in the future.

Comparison of Peripheral Nerve Regeneration with Side-to-side, End-to-side, and End-to-end Repairs: An Experimental Study

Background:

The present study was conducted to find out a tool to enable improved functional recovery with proximal nerve injury. In this experimental study, nerve regeneration was compared between side-to-side (STS), end-to-side (ETS), and end-to-end repairs.

Methods:

The walk track analysis was used as an outcome of functional recovery. Nerve regeneration was studied with morphometry and histology 6 or 26 weeks postoperatively.

Results:

All 3 repair techniques showed regeneration of the nerve. From 12 weeks onward, the functional results of the 3 intervention groups were significantly better compared with the unrepaired control group. End-to-end repair was significantly better when compared with the STS and ETS groups. At 26 weeks, the functional and morphometric results and histologic findings did not differ between the STS and ETS groups. The functional results correlated with the morphometric findings in all groups.

Conclusions:

STS neurorrhaphy showed nerve regeneration, and the end results did not differ from clinically widely used ETS repair. Further studies are warranted to optimize the neurorrhaphy technique and examine possible applications of STS repair in peripheral nerve surgery.

G-CSF prevents caspase 3 activation in Schwann cells after sciatic nerve transection, but does not improve nerve regeneration

Exogenous granulocyte-colony stimulating factor (G-CSF) has emerged as a drug candidate for improving the outcome after peripheral nerve injuries. We raised the question if exogenous G-CSF can improve nerve regeneration following a clinically relevant model - nerve transection and repair - in healthy and diabetic rats. In short-term experiments, distance of axonal regeneration and extent of injury-induced Schwann cell death was quantified by staining for neurofilaments and cleaved caspase 3, respectively, seven days after repair. There was no difference in axonal outgrowth between G-CSF-treated and non-treated rats, regardless if healthy Wistar or diabetic Goto-Kakizaki (GK) rats were examined. However, G-CSF treatment caused a significant 13% decrease of cleaved caspase 3-positive Schwann cells at the lesion site in healthy rats, but only a trend in diabetic rats. In the distal nerve segments of healthy rats a similar trend was observed. In long-term experiments of healthy rats, regeneration outcome was evaluated at 90days after repair by presence of neurofilaments, wet weight of gastrocnemius muscle, and perception of touch (von Frey monofilament testing weekly). The presence of neurofilaments distal to the suture line was similar in G-CSF-treated and non-treated rats. The weight ratio of ipsi-over contralateral gastrocnemius muscles, and perception of touch at any time point, were likewise not affected by G-CSF treatment. In addition, the inflammatory response in short- and long-term experiments was studied by analyzing ED1 stainable macrophages in healthy rats, but in neither case was any attenuation seen at the injury site or distal to it. G-CSF can prevent caspase 3 activation in Schwann cells in the short-term, but does not detectably affect the inflammatory response, nor improve early or late axonal outgrowth or functional recovery.

Electrophysiological Predictors of Clinical Outcome in Traumatic Neuropathies: A Multicenter Prospective Study

Objectives. This prospective, observational, multicentre study aims to identify electrodiagnostic (EDX) markers of clinical recovery in patients with traumatic neuropathy (TN) receiving surgical (S) and nonsurgical (NS) treatments. Methods. Subjects referred to the Italian Traumatic Neuropathy Network between 2010 and 2011 (307 patients, for a total of 444 TN) were evaluated with serial clinical/EDX evaluations at 6, 12, 24, and 36 months of follow-up. Results. Primary surgery was performed in 21 subjects with open lesions and evidence of neurotmesis, while closed lesions were treated with either conservative medical approach (216 patients) or secondary surgery (70 patients), according to the clinical spontaneous recovery at 4–6 months. Clinical improvement correlated with the increase of the compound muscle action potential amplitude (OR 3.76; CI 1.61–8.76), particularly in the S group (OR 7.25; CI 1.2–43.87), and with sensory nerve action potential amplitude in the NS group (OR 4.35; CI 1.14–16.69). No correlations were found with needle electromyography qualitative evaluations, changes in maximal voluntary recruitment, age, and gender. Conclusions. Nerve conduction studies (NCS) represent the more accurate neurophysiological markers of clinical outcome in patients with TN. Significance. Serial NCS assessments predict the functional recovery in TN, increasing the accuracy of peripheral nerves surgical decision-making process.

Comparative outcome measures in peripheral regeneration studies

Traumatic peripheral nerve injuries are common and often result in partial or permanent paralysis, numbness of the affected limb, and debilitating neuropathic pain. Experimental animal models of nerve injury have utilized a diversity of outcome measures to examine functional recovery following injury. Four primary categories of outcome measures of regenerative success including retrograde labeling with counts of regenerating neurons, immunohistochemistry and histomorphometry, reinnervation of target muscles, and behavioral analysis of recovery will be reviewed. Validity of different outcome measures are discussed in context of hindlimb, forelimb, and facial nerve injury models. Severity of nerve injury will be highlighted, and comparisons between nerve crush injury and more severe transection and neuroma-in-continuity nerve injury paradigms will be evaluated. The case is made that specific outcome measures may be more sensitive to assessing functional recovery following nerve injury than others. This will be discussed in the context of the lack of association between certain outcome measures of nerve regeneration. Examples of inaccurate conclusions from specific outcome measures will also be considered. Overall, researchers must therefore take care to select appropriate outcome measures for animal nerve injury studies dependant on the specific experimental interventions and scientific questions addressed.

Noninvasive Ultrasound of the Tibial Muscle for Longitudinal Analysis of Nerve Regeneration in Rats

BACKGROUND

Today's criterion standards for measuring functional recovery after nerve trauma in experimental studies are the muscle mass ratio and the isometric tetanic force; both tests are invasive and require a sacrificial procedure. The authors propose ultrasound as a noninvasive method to determine muscle atrophy, and evaluate its validity and reliability by comparing it to muscle mass ratio, isometric tetanic force, and histology.

METHODS

Fifty rats sustained a 10-mm autograft sciatic nerve reconstruction. With a 2-week interval, five animals were tested with a total follow-up of 20 weeks. The functional recovery of the hind-limb muscles was measured with ultrasound, muscle mass ratio, and isometric tetanic force. In addition, neuromuscular junctions were analyzed histologically. The different evaluation techniques were compared and the reliability of the ultrasound was determined.

RESULTS

Four weeks after denervation, extensive muscle atrophy resulted in a decrease of muscle mass up to 30 percent. Ultrasound showed good correlations with muscle mass ratio for both tibial (r = 0.85) and gastrocnemius muscles (r = 0.89). Both intrarater reliability (r = 0.97) and interrater reliability (r = 0.88) of the ultrasound were high. The correlation with force was lower (0.62) but still statistically significant.

CONCLUSIONS

Ultrasound measurement of muscle atrophy was highly correlated with the criterion standard muscle mass ratio and was also significantly correlated with isometric tetanic force. Histologic evaluation confirmed the regeneration pattern observed with ultrasound. The authors propose that ultrasound can be used as a valid alternative to muscle mass ratio to study muscle atrophy after nerve injury in a less-invasive and more animal-friendly manner.

Local Polyethylene Glycol in Combination with Chitosan Based Hybrid Nanofiber Conduit Accelerates Transected Peripheral Nerve Regeneration

OBJECTIVE

The incapability to promptly improve behavioral function after discontinuation of peripheral nerves is a current problem in clinical practice. Effect of local polyethylene glycol in combination with chitosan-based hybrid nanofiber conduit was assessed.

STUDY DESIGN

A 10-mm sciatic nerve defect was bridged using a chitosan-based hybrid nanofiber conduit (Chitosan) filled with phosphate-buffered saline. In authograft group (AUTO), a segment of sciatic nerve was transected and reimplanted reversely. In polyethylene glycol-treated group (CHIT/PEG), the conduit was filled with polyethylene glycol solution. The regenerated fibers were studied within 12 weeks after surgery.

RESULTS

The behavioral and functional tests confirmed faster recovery of the regenerated axons in PEG-treated group compared to Chitosan group (p < .05). The mean ratios of gastrocnemius muscles weight were measured. There was statistically significant difference between the muscle weight ratios of CHIT/PEG and Chitosan groups (p < .05). Morphometric indices of regenerated fibers showed number and diameter of the myelinated fibers were significantly higher in CHIT/PEG than in Chitosan. In immuohistochemistry, the location of reactions to S-100 in CHIT/PEG was clearly more positive than Chitosan group.

CONCLUSION

polyethylene glycol solution when loaded in a chitosan-based hybrid nanofiber conduit resulted in acceleration of functional recovery and quantitative morphometric indices of sciatic nerve.

The topographic specificity of muscle reinnervation predicts function

Functional testing has assumed a progressively dominant role in validating the success of experimental nerve repair. Results obtained in one model, however, cannot predict the results in others because they reflect the coordinated interaction of several muscles across multiple joints. As a result, many combinations of topographically correct and incorrect muscle reinnervation could produce the same result. We have developed a binary model in which elbow flexors and extensors are reinnervated, and elbow flexion and extension are the functions tested. The musculocutaneous and radial nerves of Lister-Hooded rats were subjected to axonotmetic injuries that produced increasing degrees of axonal misdirection at the site of injury ranging from simple crush to transection and rotational offset of proximal and distal stumps. Elbow function was tested with a device that requires coordinated elbow extension to reach sugar pellets and flexion to return them to the mouth. After 12 weeks of regeneration, motoneurons projecting to the distal musculocutaneous nerve were retrogradely labelled with WGA-Ruby and scored regarding their location within musculocutaneous or radial motoneuron pools. The severity of axonal misdirection resulting from the initial surgery was mirrored by progressive degrees of inappropriate reinnervation of the musculocutaneous nerve by radial nerve axons. The specificity of reinnervation predicted elbow function (r = 0.72), whereas the number of motoneurons regenerating did not. This model is thus well suited to study the interaction of regeneration specificity and function across a single joint, and to produce data that can be generalized more broadly than those obtained from more complex models.

Functional evaluation of peripheral nerve regeneration and target reinnervation in animal models: a critical overview

Peripheral nerve injuries usually lead to severe loss of motor, sensory and autonomic functions in the patients. Due to the complex requirements for adequate axonal regeneration, functional recovery is often poorly achieved. Experimental models are useful to investigate the mechanisms related to axonal regeneration and tissue reinnervation, and to test new therapeutic strategies to improve functional recovery. Therefore, objective and reliable evaluation methods should be applied for the assessment of regeneration and function restitution after nerve injury in animal models. This review gives an overview of the most useful methods to assess nerve regeneration, target reinnervation and recovery of complex sensory and motor functions, their values and limitations. The selection of methods has to be adequate to the main objective of the research study, either enhancement of axonal regeneration, improving regeneration and reinnervation of target organs by different types of nerve fibres, or increasing recovery of complex sensory and motor functions. It is generally recommended to use more than one functional method for each purpose, and also to perform morphological studies of the injured nerve and the reinnervated targets.

Gait analysis after neurorrhaphy in the brachial plexus

The gait is a form of human and animal locomotion on land by using limbs. The study assessed functional recovery after end to side and side to side neurorrhaphy the ventral branches of the C5 and C6 spinal nerves to the C7 spinal nerve on the rabbit brachial plexus. Gait statistical analysis showed significant differences between the control group versus the end-to-side and side to side neurorrhaphy groups, in opposite to the comparison between the two experimentals groups. Gait analysis results corresponded with the histomorphometric results. The results indicate the potential use of gait analysis for the assessment of the recovery of nerve function.

Gait cycle analysis: parameters sensitive for functional evaluation of peripheral nerve recovery in rat hind limbs

BACKGROUND

Video-assisted gait kinetics analysis has been a sensitive method to assess rat sciatic nerve function after injury and repair. However, in conduit repair of sciatic nerve defects, previously reported kinematic measurements failed to be a sensitive indicator because of the inferior recovery and inevitable joint contracture.

OBJECTIVE

This study aimed to explore the role of physiotherapy in mitigating joint contracture and to seek motion analysis indices that can sensitively reflect motor function.

METHODS

Data were collected from 26 rats that underwent sciatic nerve transection and conduit repair. Regular postoperative physiotherapy was applied. Parameters regarding step length, phase duration, and ankle angle were acquired and analyzed from video recording of gait kinetics preoperatively and at regular postoperative intervals.

RESULTS

Stride length ratio (step length of uninjured foot/step length of injured foot), percent swing of the normal paw (percentage of the total stride duration when the uninjured paw is in the air), propulsion angle (toe-off angle subtracted by midstance angle), and clearance angle (ankle angle change from toe off to midswing) decreased postoperatively comparing with baseline values. The gradual recovery of these measurements had a strong correlation with the post-nerve repair time course.

CONCLUSIONS

Ankle joint contracture persisted despite rigorous physiotherapy. Parameters acquired from a 2-dimensional motion analysis system, that is, stride length ratio, percent swing of the normal paw, propulsion angle, and clearance angle, could sensitively reflect nerve function impairment and recovery in the rat sciatic nerve conduit repair model despite the existence of joint contractures.

Effects of physical exercise on the functional recovery of rat hindlimbs with impairments of the sciatic nerve as assessed by 2D video analysis

[Purpose] The purpose of this study was to investigate the effects of treadmill training on functional recovery by analyzing the ankle joint as well as the knee and hip joints with 2D video analysis during gait by rats with sciatic nerve injury. [Subjects and Methods] Twenty-four male Sprague-Dawley rats were used in this study. The sham group (SG) received only a sham operation without any sciatic injury; the training group (TG) performed treadmill training for 4 weeks after sciatic injury; and the control group (CG) wasn’t provided with any therapeutic intervention after sciatic injury. [Results] The ankle, knee, and hip ROM of TG and CG during the initial, mid stance, and toe-off phases of gait at post-test were significantly different from SG. [Conclusion] Physical exercise, like treadmill training, is beneficial for the improvement of the ankle, knee and hip joints of rats with crushed sciatic nerve injury.

Application of topical pharmacological agents at the site of peripheral nerve injury and methods used for evaluating the success of the regenerative process

Traumatic injuries of the peripheral nerves are very common. Surgical repair of the damaged nerve is often complicated by scar tissue formation around the damaged nerve itself. The main objective of this study is to present the recent data from animal experimental studies where pharmacological topical agents are used at the site of peripheral nerve repair. Some of the most commonly topical agents used are tacrolimus (FK506), hyaluronic acid and its derivatives, and melatonin, whereas methylprednisolone and vitamin B12 have been used less. These studies have shown that the abovementioned substances have neuroprotective and neuroregenerative properties though different mechanisms. The successes of the regenerative process of the nerve repair in experimental research, using topical agents, can be evaluated using variety of methods such as morphological, electrophysiologic, and functional evaluation. However, most authors agree that despite good microsurgical repair and topical application of these substances, full regeneration and functional recovery of the nerve injured are almost never achieved.

Non-invasive isometric force measurement of plantar flexors in rats

INTRODUCTION

Isometric muscle force measurement is a sensitive marker for motor function recovery in rat nerve repair models. Current methods of eliciting maximal isometric force with nerve stimulation cannot provide longitudinal data.

METHODS

We developed a novel method for measuring isometric muscle force with a device designed to allow minimally invasive nerve stimulation and measurement of plantar flexion force. This indirectly elicited muscle force was compared with muscle force elicited by direct muscle stimulation in 3 surgical models.

RESULTS

The force measured after sciatic nerve transection and repair followed a parabolic trend. There was a postinjury decrease in force that continued until postoperative day 42, after which the force increased with time, indicating muscle reinnervation.

CONCLUSIONS

This approach can track longitudinal changes in force in the most common animal model for studies of clinically relevant problems in the peripheral nerve field.

Biocompatible heterogeneous porous gel matrix NeuroGel(TM) promotes regeneration of rat sciatic nerve within tubular silicone prosthesis (experimental study)

BACKGROUND

The purpose of this study was to investigate the ability of NeuroGel™ to promote and enhance the regeneration of rat sciatic nerve within a 10-mm gap using silicone tubular prosthesis, and to evaluate and compare the regeneration outcomes versus autologous grafting.

METHODS

The 10-mm gap of rat sciatic nerve was bridged through silicone tubular prosthesis filled with dehydrated NeuroGel™, and NeuroGel™ saturated with rat NGF-B (NG30-NGG60, NGgfB30-NGgfB60). To assess the regeneration of the peripheral nerve we utilized three general and most commonly applied methods: electrophysiologic, hystomorphometric, and functional methods.

RESULTS

The average M-wave amplitude (AMW index), or the intermediary index of the number of regenerated axons, in animal groups NGG60 and NGgfB60 60 days post-op was: 2.44 ± 0.57 mV and 1.87 ± 0.48 mV. These indices were statistically lower compared to the indices obtained after autologous grafting. The average impulse conduction velocity along motor fibers (VMF index), or the intermediary index of myelination rate, was: 13.3 mm/ms and 13.3 mm/ms, respectively, statistically equal to indices obtained after autologous grafting. The average density (D) of regenerated fibers (direct numerical indicator in contrast to intermediary AMW index) in animal groups NGG60 and NGgfB60 was: 4,920 ± 178.88 and 5,340 ± 150.33 per mm(2), respectively. These indices were statistically higher versus indices obtained after autologous grafting. Myelination rates of regenerated fibers in animal groups NGG60 and NGgfB60 were 73 and 86 %, respectively. They were also statistically higher. The average sciatic functional index (SFI) in NGG60 and NGgfB60 was: -25.57 ± 3.05 and -24.124 ± 4.8, respectively, which is statistically equal to indices obtained after autologous grafting.

CONCLUSIONS

Neurogel™ strongly promotes the regeneration of rat sciatic nerve within silicone tubular prosthesis. After bridging a 10-mm gap through silicone prosthesis with Neurogel™ or Neurogel™ +NGF-B-modified intraluminal space, the myelination rate of regenerated axons of rat sciatic nerve appeared to be higher, and the axon count and functional recovery is similar to results seen with the autografting technique.

The correlation of neurophysiological findings with clinical and functional status in patients following traumatic nerve injury

In this study, we aimed to determine whether there is a correlation between the electrodiagnostic findings and the functional status, muscle strength and sensibility in patients with traumatic nerve injury to the wrists. We assessed 50 patients at a mean of 11.6 months (SD 5.85) (range 6-25) after nerve injury. Sensibility was assessed by monofilament testing. Motor function was evaluated by assessing the manual muscle grade of the abductor pollicis brevis and abductor digiti minimi muscles. Function was evaluated by the Sollerman Hand Function Test. The amplitudes of the compound muscle action potential and the sensory nerve action potential were determined by electroneuromyography. While the compound muscle action potential and sensory nerve action potential amplitudes had significant correlation with muscle grade and Semmes Weinstein Monofilament tests, there was no correlation with the functional scores.

Functional evaluation in the rat sciatic nerve defect model: a comparison of the sciatic functional index, ankle angles, and isometric tetanic force

BACKGROUND

The sciatic functional index has long been the standard method of assessing motor recovery in the rat sciatic nerve model. The relative subjective nature of the assessment has led to development of newer methods, including video gait analysis and quantitative measurement of isometric tetanic muscle force.

METHODS

Forty male Lewis rats, each with a 10-mm segmental defect in the sciatic nerve, were divided randomly into two groups: rats in group I underwent repair with reversed autograft, and those in group II received a collagen conduit. Video gait analyses were performed at 0, 4, 8, and 12 weeks, and sciatic functional index and ankle angles in four different walking phases were recorded. Isometric tetanic force of the tibialis anterior muscle was also measured at 12 weeks and correlated with sciatic functional index and video gait analysis data.

RESULTS

The sciatic functional index results did not correlate with isometric tetanic force. Significantly, the sciatic functional index could not be measured in 26 percent of the rats at 8 weeks and 59 percent of the rats at 12 weeks secondary to toe contractures. Among various ankle angle measurements, only the ankle angle in toe-off phase correlated well with isometric tetanic force.

CONCLUSIONS

Toe contractures occurred more frequently in rats with better nerve recovery, and interfered with evaluation of the motor recovery using the sciatic functional index method. Ankle angle in toe-off phase measured from video gait analysis is a useful parameter that reflects functional recovery of the muscle force.

Return of motor function after repair of a 3-cm gap in a rabbit peroneal nerve: a comparison of autograft, collagen conduit, and conduit filled with collagen-GAG matrix

BACKGROUND

The purpose of this study was to evaluate the motor nerve recovery in a rabbit model after repair of a 3-cm gap in the peroneal nerve with a conduit filled with a collagen-GAG (glycosaminoglycan) matrix and compare the results with those after reconstruction with an autograft or an empty collagen conduit.

METHODS

Forty-two male New Zealand rabbits were divided into three experimental groups. In each group, a unilateral 3-cm peroneal nerve defect was repaired with a nerve autograft, an empty collagen conduit, or a conduit filled with a collagen-GAG matrix. At six months, nerve regeneration was evaluated on the basis of the compound muscle action potentials, maximum isometric tetanic force, and wet muscle weight of the tibialis anterior muscle as well as nerve histomorphometry.

RESULTS

The autograft group had significantly better motor recovery than the conduit groups. The empty collagen conduits and conduits filled with the collagen-GAG matrix led to results that were similar to each other.

CONCLUSIONS

On the basis of this rabbit model, autologous nerve grafting remains the gold standard in the reconstruction of 3-cm segmental motor nerve defects.

CLINICAL RELEVANCE

Segmental motor nerve defects should be reconstructed with autograft nerves. The use of a collagen conduit filled with a collagen-GAG matrix for motor nerve reconstruction should be limited until additional animal studies are performed.

The effects of cold preservation and subimmunosuppressive doses of FK506 on axonal regeneration in murine peripheral nerve isografts

BACKGROUND

FK506 is a frequently used immunosuppressant with neuroregenerative effects. The neuroregenerative and immunosuppressive mechanisms of FK506, however, are distinct, suggesting that FK506 may stimulate nerve regeneration at lower doses than are needed to induce immunosuppression. The effects of cold preservation, a technique known to improve axonal regeneration through nerve allografts, are not well studied in nerve isografts and are also reported here.

OBJECTIVES

To determine the effects of subimmunosuppressive doses of FK506 and cold preservation on nerve regeneration in isografts.

METHODS

The neuroregenerative properties of immunosuppressive and subimmunosuppressive doses of FK506 were compared in a murine model receiving either fresh or cold preserved nerve isografts. Sixty female BALB/cJ mice were randomized into six groups. Animals in groups I, III and V received fresh nerve isografts. Animals in groups II, IV and VI received cold-preserved nerve isografts. Mice in groups I and II received no medical therapy, while those in groups III and IV received subimmunosuppressive doses of FK506, and those in groups V and VI received immunosuppressive doses as confirmed by mixed lymphocyte reactivity assays. Nerve regeneration was evaluated with histomorphometry and functional recovery was evaluated with walking track analysis.

RESULTS

Pretreatment with cold preservation did not significantly affect neural regeneration. The potent neuroregenerative effect of immunosuppressive doses of FK506 was confirmed, and the ability of subimmunosuppressive doses of FK506 to stimulate axonal regeneration in murine nerve isografts is reported.

CONCLUSIONS

Less toxic subimmunosuppressive doses of FK506 retaining some neuroregenerative properties may have a clinical role in treating extensive nerve injuries.

Variation in nerve autograft length increases fibre misdirection and decreases pruning effectiveness. An experimental study in the rat median nerve

OBJECTIVES

In the clinical set, autologus nerve grafts are the current option for reconstruction of nerve tissue losses. The length of the nerve graft has been suggested to affect outcomes. Experiments were performed in the rat in order to test this assumption and to detect a possible mechanism to explain differences in recovery.

METHODS

The rat median nerve was repaired by ulnar nerve grafts of different lengths. Rats were evaluated for 12 months by behavioural assessment and histological studies, including ATPase myofibrillary histochemistry and retrograde neuronal labelling.

RESULTS

It was demonstrated that graft length interferes in behavioural functional recovery that here correlates to muscle weight recovery. Short nerve grafts recovered faster and better. Reinnervation was not specific either at the trunk level or in the muscle itself. The normal mosaic pattern of Type I muscle fibres was never restored and their number remained largely augmented. An increment in the number of motor fibres was observed after the nerve grafting in a predominantly sensory branch in all groups. This increment was more pronounced in the long graft group. In the postoperative period, about a 20% reduction in the number of misdirected motor fibres occurred in the short nerve graft group only.

CONCLUSION

Variation in the length of nerve grafts interferes in behavioural recovery and increases motor fibres misdirection. Early recovery onset was related to a better outcome, which occurs in the short graft group.

Poor electroneurography but excellent hand function 31 years after nerve repair in childhood

Children, in contrast to adults, show an excellent clinical recovery after a peripheral nerve injury, which may be explained by better peripheral nerve regeneration and a superior plasticity in the young brain. Our aim was to study the long-term electrophysiological outcome after nerve repair in children and young adults and to compare it with the clinical outcome. Forty-four patients, injured at an age younger than 21 years, were assessed by electrophysiology (amplitude, conduction velocity and distal motor latency) at a median of 31 years after a complete median or ulnar nerve injury at the level of the forearm. Electrophysiological evaluation showed pathology in all parameters and in all patients, irrespective of age at injury. No significant differences were observed in the electrophysiological results between those injured in childhood, that is, before the age of 12 years, and those injured in adolescence, that is, between 12 and 20 years of age. In contrast, the clinical nerve function was significantly better for those injured in childhood (87% of complete recovery, P=0.002) compared with those injured in adolescence. We conclude that the mechanism behind the superior clinical outcome in children is not located at the periphery, but is explained by cerebral plasticity.

Dexamethasone topically accelerates peripheral nerve repair and target organ reinnervation: a transected sciatic nerve model in rat

The objective was to assess the effect of topically administered dexamethasone on peripheral nerve regeneration and functional recovery. Sixty male healthy white Wistar rats were divided into four experimental groups (n = 15), randomly: in transected group (TC), left sciatic nerve was transected and stumps were fixed in the adjacent muscle. In treatment group defect was bridged using a silicone tube (SIL/Dexa) filled with 10 μL dexamethasone (0.1 mg/kg). In silicone group (SIL), the tube was filled with phosphate-buffered saline alone. In sham-operated group (SHAM), sciatic nerve was exposed and manipulated. Each group was subdivided into three subgroups of five animals each and regenerated nerve fibres were studied 4, 8 and 12 weeks after surgery. Functional study, gastrocnemius muscle mass and morphometric indices confirmed faster recovery of regenerated axons in SIL/Dexa than SIL group (p < 0.05). In immunohistochemistry, location of reactions to S-100 in SIL/Dexa was clearly more positive than that in SIL group. When loaded in a silicone tube, dexamethasone improved functional recovery and morphometric indices of sciatic nerve. Topical application of this readily available agent offers the benefit of cost savings as well as avoiding the complications associated with systemic administration.

Effect of skilled and unskilled training on nerve regeneration and functional recovery

The most disabling aspect of human peripheral nerve injuries, the majority of which affect the upper limbs, is the loss of skilled hand movements. Activity-induced morphological and electrophysiological remodeling of the neuromuscular junction has been shown to influence nerve repair and functional recovery. In the current study, we determined the effects of two different treatments on the functional and morphological recovery after median and ulnar nerve injury. Adult Wistar male rats weighing 280 to 330 g at the time of surgery (N = 8-10 animals/group) were submitted to nerve crush and 1 week later began a 3-week course of motor rehabilitation involving either "skilled" (reaching for small food pellets) or "unskilled" (walking on a motorized treadmill) training. During this period, functional recovery was monitored weekly using staircase and cylinder tests. Histological and morphometric nerve analyses were used to assess nerve regeneration at the end of treatment. The functional evaluation demonstrated benefits of both tasks, but found no difference between them (P > 0.05). The unskilled training, however, induced a greater degree of nerve regeneration as evidenced by histological measurement (P < 0.05). These data provide evidence that both of the forelimb training tasks used in this study can accelerate functional recovery following brachial plexus injury.