"Donor" muscle structure and function after end-to-side neurorrhaphy

End-to-end nerve coaptation is the preferred surgical technique for peripheral nerve reconstruction after injury or tumor extirpation. However, if the proximal nerve stump is not available for primary repair, then end-to-side neurorrhaphy may be a reasonable alternative. Numerous studies have demonstrated the effectiveness of this technique for muscle reinnervation. However, very little information is available regarding the potential adverse sequelae of end-to-side neurorrhaphy on the innervation and function of muscles innervated by the "donor" nerve. End-to-side neurorrhaphy is hypothesized to (1) acutely produce partial donor muscle denervation and (2) chronically produce no structural or functional deficits in muscles innervated by the donor nerve. Adult Lewis rats were allocated to one of two studies to determine the acute (2 weeks) and chronic (6 months) effects of end-to-side neurorrhaphy on donor muscle structure and function. In the acute study, animals underwent either sham exposure of the peroneal nerve (n = 13) or end-to-side neurorrhaphy between the end of the tibial nerve and the side of the peroneal nerve (n = 7). After a 2-week recovery period, isometric force (F(0) was measured, and specific force (sF(0) was calculated for the extensor digitorum longus muscle ("donor" muscle) for each animal. Immunohistochemical staining for neural cell adhesion molecule (NCAM) was performed to identify populations of denervated muscle fibers. In the chronic study, animals underwent either end-to-side neurorrhaphy between the end of the peroneal nerve and the side of the tibial nerve (n = 6) or sham exposure of the tibial nerve with performance of a peroneal nerve end-to-end nerve coaptation approximately 6), to match the period of anterior compartment muscle denervation in the end-to-side neurorrhaphy group. After a 6-month recovery period, contractile properties of the medial gastrocnemius muscle ("donor" muscle) were measured. Acutely, a fivefold increase in the percentage of denervated muscle fibers (1 +/0 0.7 percent to 5.4 +/-2.7 percent) was identified in the donor muscles of the animals with end-to-side neurorrhaphy (p < 0.001). However, no skeletal muscle force deficits were identified in these donor muscles. Chronically, the contractile properties of the medial gastrocnemius muscles were identical in the sham and end-to-side neurorrhaphy groups. These data support our two hypotheses that end-to-side neurorrhaphy causes acute donor muscle denervation, suggesting that there is physical disruption of axons at the time of nerve coaptation. However, end-to-side neurorrhaphy does not affect the long-term structure or function of muscles innervated by the donor nerve.     

Functional and morphometric evaluation of end-to-side neurorrhaphy for muscle reinnervation

This study was undertaken to quantify the effect of motor collateral sprouting in an end-to-side repair model allowing end organ contact. Besides documentation of the functional outcome of muscle reinnervation by end-to-side neurorrhaphy, this experimental work was performed to determine possible downgrading effects to the donor nerve at end organ level. In 24 female New Zealand White rabbits, the motor nerve branch to the rectus femoris muscle of the right hindlimb was dissected, cut, and sutured end-to-side to the motor branch to the vastus medialis muscle after creating an epineural window. The 24 rabbits were divided into two groups of 12 each, with the second group receiving additional crush injury of the vastus branch. After a period of 8 months, maximum tetanic tension in the reinnervated rectus femoris and the vastus medialis muscles was determined. The contralateral healthy side served as control. The reinnervated rectus femoris muscle showed an average maximum tetanic force of 24.9 N (control 26.2 N, p = 0.7827), and the donor- vastus medialis muscle 11.0 N (control 7.3 N, p = 0.0223). There were no statistically significant differences between the two experimental groups (p = 0.9914). The average number of regenerated myelinated nerve fibers in the rectus femoris motor branch was 1,185 +/- 342 (control, 806 +/- 166), and the mean diameter was 4.6 +/- 0.6 microm (control, 9.4 +/- 1.0 microm). In the motor branch to the vastus medialis muscle, the mean fiber number proximal to the coaptation site was 1227 (+/-441), and decreased distal to the coaptation site to 795 (+/-270). The average difference of axon counts in the donor nerve proximal to distal regarding the repair site was 483.7 +/- 264.2. In the contralateral motor branch to the vastus medialis muscle, 540 (+/- 175) myelinated nerve fibers were counted. In nearly all cross-section specimens of the motor branch to the vastus medialis muscle, altered nerve fibers could be identified in one fascicle distal and proximal to the repair site. The results show a relevant functional reinnervation by end-to-side neurorrhaphy without functional impairment of the donor muscle. It seems to be evident that most axons in the attached segment were derived from collateral sprouts. Nonetheless, the present study confirms that end-to-side neurorrhaphy is a reliable method of reconstruction for damaged nerves, which should be applied clinically in a more extended manner.     

Epineurial Window Is More Efficient in Attracting Axons than Simple Coaptation in a Sutureless (Cyanoacrylate-Bound) Model of End-to-Side Nerve Repair in the Rat Upper Limb: Functional and Morphometric Evidences and Review of the Literature

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10–11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.     

Mechanical function of muscle reinnervated by end-to-side neurorrhaphy.

End-to-side neurorrhaphy is a surgical technique for peripheral nerve reconstruction when end-to-end neurorrhaphy is not an option. To define the effectiveness of end-to-side neurorrhaphy as a method of nerve repair, the authors tested the null hypothesis: there is no difference in the mechanical function of skeletal muscle denervated and reinnervated by end-to-side versus end-to-end neurorrhaphy. Adult Lewis rats underwent either transection and end-to-end epineurial repair of the left peroneal nerve (n = 9) or end-to-side repair of the distal stump of the peroneal nerve to the side of the tibial nerve (n = 8). After a 6-month recovery period, isometric force (Fo) was measured, and specific force (sFo) was calculated for the extensor digitorum longus muscle of each animal. Immunohistochemical staining for neural cell adhesion molecule (NCAM) was performed to identify populations of denervated muscle fibers. The mean extensor digitorum longus muscle mass in the end-to-end group (195 +/- 32 g) was significantly greater than that of the end-to-side group (146 +/- 55 g) (p < 0.05). A significantly greater percentage of denervated fibers was identified in the extensor digitorum longus muscles of animals in the end-to-side group (9.4 +/- 3.2 percent) than in those in the end-to-end group (3.8 +/- 1.0 percent) (p < 0.05). Despite a lower muscle mass and a higher percentage of denervated fibers, neither Fo nor sFo was significantly different in the two groups. These data support the null hypothesis that, under appropriate circumstances, there is no difference in the recovery of whole muscle force and specific force production in muscles reinnervated by end-to-side versus end-to-end neurorrhaphy.     

Nerve regeneration through side-to-side neurorrhaphy sites in a rat model: a new concept in peripheral nerve surgery

Despite great improvement and refinements in nerve repair techniques, there were still problems in repair of peripheral nerve injuries for which proximal stumps were not available. In these circumstances for which classic end-to-end neurorrhaphy was impossible, new treatment modalities, benefiting by an adjacent healthy nerve, have been under investigation to overcome this problem. Therefore, end-to-side nerve repair with its modifications came to view and axonal passages through this site were shown. Moreover, the results were unsatisfactory or necessitating sacrifice of another healthy nerve. Three groups, containing 10 rats each, were included in the study. First was the control group, with end-to-end repair of the peroneal nerve. Second was the end-to-side repair group, in which the distal stump of the peroneal nerve trunk was anastomosed to the lateral side of the tibial nerve. The third was the side-to-side repair group. In this technique, 1-mm diameter epineural windows, both from peroneal and tibial nerve trunks facing each other, were removed and side-to-side neurorrhaphy was performed. After 3 weeks, as the second step, the peroneal nerve was sectioned proximally. At 2, 4, 8, 12, 20, and 28 weeks, functional assessment of nerve regeneration was performed by using walking track analysis. The number of myelinated fibers and fiber diameters were measured and an electron microscopic evaluation was carried out. Statistically, both in morphometric and gait analysis, the differences in values between the groups were significant in favor of the control group, followed by the side-to-side group. The study showed that axonal passage was possible with side-to-side technique and the functional results were satisfactory and superior to the end-to-side technique. Continuous supply of neurotrophic factors from their target cells was the probable cause of superior functional return in side-to-side repair, because both joining nerves were intact and healthy during the anastomosis procedure and after 3 weeks. It was concluded that this technique could be indicated in salvage of nerves in cases for which any intermediate segments would be removed, as in tumor ablation surgery, harvesting of nerve grafts, or both.     

Use new PLGL-RGD-NGF nerve conduits for promoting peripheral nerve regeneration

ABSTRACT: BACKGROUND: Nerve conduits provide a promising strategy for peripheral nerve injury repair. However, the efficiency of nerve conduits to enhance nerve regeneration and functional recovery is often inferior to that of autografts. Nerve conduits require additional factors such as cell adhesion molecules and neurotrophic factors to provide a more conducive microenvironment for nerve regeneration. METHODS: In the present study, poly{(lactic acid)-co-[(glycolic acid)-alt-(L-lysine)]} (PLGL) was modified by grafting Gly-Arg-Gly-Asp-Gly (RGD peptide) and nerve growth factor (NGF) for fabricating new PLGL-RGD-NGF nerve conduits to promote nerve regeneration and functional recovery. PLGL-RGD-NGF nerve conduits were tested in the rat sciatic nerve transection model. Rat sciatic nerves were cut off to form a 10 mm defect and repaired with the nerve conduits. All of the 32 Wistar rats were randomly divided into 4 groups: group PLGL-RGD-NGF, group PLGL-RGD, group PLGL and group autograft. At 3 months after surgery, the regenerated rat sciatic nerve was evaluated by footprint analysis, electrophysiology, and histologic assessment. Experimental data were processed using the statistical software SPSS 10.0. RESULTS: The sciatic function index value of groups PLGL-RGD-NGF and autograft was significantly higher than those of groups PLGL-RGD and PLGL. The nerve conduction velocities of groups PLGL-RGD-NGF and autograft were significantly faster than those of groups PLGL-RGD and PLGL. The regenerated nerves of groups PLGL-RGD-NGF and autograft were more mature than those of groups PLGL-RGD and PLGL. There was no significant difference between groups PLGL-RGD-NGF and autograft. CONCLUSIONS: PLGL-RGD-NGF nerve conduits are more effective in regenerating nerves than both PLGL-RGD nerve conduits and PLGL nerve conduits. The effect is as good as that of an autograft. This work established the platform for further development of the use of PLGL-RGD-NGF nerve conduits for clinical nerve repair.     

Experimental study of results of nerve suture under tension vs. nerve grafting.

Evoked electromyograms and myelinated fiber caliber histograms were used to compare the results of end-to-end nerve suture and nerve grafting, performed with an operating microscope. The best results were achieved after direct suture without tension. Direct suture under a tension of 25 grams produced results sometimes comparable the that of the zero tension group, but mostly quite inferior to those and even to the grafted group. The regeneration of axons in the nerve graft group was delayed more than in the sutured groups, but by the tenth month the number of regenerating fibers had increased with stable and comparatively good results. After a nerve suture under a tension of 25 grams, there is impairment of the blood flow at the suture site, and the results are not as good. In such situations I believe nerve grafting should be performed. This amount of tension also seems to be the limit which will allow accurate coaptation of a nerve by microsurgical techniques.     

低温保存许旺细胞对周围神经再生的作用

目的：比较原代培养许旺细胞（Schwann cells,SCs)和冷冻保存的SCs移植对损伤后坐骨神经再生的作用。方法：原代培养和液氮保存的SCs分别移植到桥接缺损坐骨神经的硅胶管内。在移植后不同时间（第6和8周末）,硅胶管远端神经干内注射HRP,逆行追踪背根神经节和脊髓前角的标记神经元数量;测量再生神经纤维的复合动作电位传导速度;电镜观察再生神经纤维的髓鞘形成。结果：原代培养和冷冻保存SCs在移植后不同时间其背根神经节和脊髓前角神经元HRP标记细胞数量、再生神经纤维的复合动作电位传导速度基本一致,再生神经纤维髓鞘的形成未见明显差别。结论：冷冻保存的SCs仍具有促进损伤后周围神经再生的能力。     

A conditioning lesion promotes in vivo nerve regeneration in the contralateral sciatic nerve of rats

A conditioning lesion in the sciatic nerve increases in vivo axonal regeneration in the nerve after a second transection. We studied whether this increased regeneration also occurs in the contralateral nerve. The left sciatic nerve was transected and sutured in Wistar rats; the nerve was exposed but not transected in controls. After 5 days, the right sciatic nerves of all rats were transected and sutured. Neuronal regeneration was measured at 0, 1, 3, 5, and 7 days with the pinch test and histological staining. IL-1beta and TGF-beta1 expression was also measured. The initial delay in the experimental group was significantly shorter, but the regeneration rates were the same. The expression of IL-1beta and TGF-beta1 in the right dorsal root ganglia was significantly higher in the experimental group. Nerve injury enhances cytokine expression in the contralateral dorsal root ganglion and promotes contralateral nerve regeneration in vivo by shortening the initial delay.     

Fate of 3H-thymidine labelled myogenic cells in regeneration of muscle isografts

Summary Intact and denervated extensor digitorum longus (EDL) muscles of 20-day-old inbred Lewis-Wistar rats were labelled with ³H-thymidine. Ninety minutes after the injection of the isotope 4.0% of the nuclei were labelled in the intact (i.e. innervated) and 9.6% in the muscles, denervated 3 days before administration of the isotope. The labelled EDL muscles were grafted into the bed of the previously removed EDL muscles of inbred animals and these isografts were studied 30 days later.In the EDL muscles, regenerated from innervated isografts only occasionally labelled endothelial cells were found whereas in the muscles regenerated from denervated isografts also parenchymal muscle nuclei were regularly labelled. The incidence of labelled nuclei in the regenerated EDL muscles was, however, about 20 times lower than in the donor EDL muscles. The present experiments provide a direct proof of utilization of donor satellite cell nuclei for regeneration in grafted muscle tissue. With respect to the low incidence of labelled nuclei in regenerated EDL muscles, other sources of cells apparently also contribute to the regeneration process.     

Neural Stem Cells Enhance Nerve Regeneration after Sciatic Nerve Injury in Rats

With the development of tissue engineering and the shortage of autologous nerve grafts in nerve reconstruction, cell transplantation in a conduit is an alternative strategy to improve nerve regeneration. The present study evaluated the effects and mechanism of brain-derived neural stem cells (NSCs) on sciatic nerve injury in rats. At the transection of the sciatic nerve, a 10-mm gap between the nerve stumps was bridged with a silicon conduit filled with 5?×?10⁵ NSCs. In control experiments, the conduit was filled with nerve growth factor (NGF) or normal saline (NS). The functional and morphological properties of regenerated nerves were investigated, and expression of hepatocyte growth factor (HGF) and NGF was measured. One week later, there was no connection through the conduit. Four or eight weeks later, fibrous connections were evident between the proximal and distal segments. Motor function was revealed by measurement of the sciatic functional index (SFI) and sciatic nerve conduction velocity (NCV). Functional recovery in the NSC and NGF groups was significantly more advanced than that in the NS group. NSCs showed significant improvement in axon myelination of the regenerated nerves. Expression of NGF and HGF in the injured sciatic nerve was significantly lower in the NS group than in the NSCs and NGF groups. These results and other advantages of NSCs, such as ease of harvest and relative abundance, suggest that NSCs could be used clinically to enhance peripheral nerve repair.     

The harvest and clinical application of the superficial peroneal sensory nerve for grafting motor and sensory nerve defects.

Potential donor nerves for autografting are finite and usually limited to cutaneous nerves of the extremities. The superficial peroneal nerve is the major lateral branch of the common peroneal nerve that innervates the peroneus longus and brevis muscles and provides sensation to the lateral aspect of the lower leg and the dorsal foot. It has generally been overlooked as a potential donor of nerve autografts. Cadaver dissections were performed on 10 fresh lower extremity specimens to investigate the anatomic characteristics of the superficial peroneal nerve and to refine a harvesting technique for the nerve. Thirty-one patients underwent nerve grafting of 39 upper and lower extremity nerves using the superficial peroneal donor. There were nine median nerves, four ulnar nerves, two radial nerves, two brachial plexus lesions, 16 digital nerves, and six lower extremity nerves grafted. The superficial peroneal nerve provided a consistently long donor, comparable in length to the sural nerve. The anatomic pattern is consistent, the patient positioning is simple, the surgical harvesting technique is straightforward, and the donor defect is acceptable. The superficial peroneal nerve provides a safe and valuable donor nerve, particularly in cases where multiple or very long nerve grafts are required.     

Local substitution of GDF-15 improves axonal and sensory recovery after peripheral nerve injury

The growth/differentiation factor-15, GDF-15, has been found to be secreted by Schwann cells in the lesioned peripheral nervous system. To investigate whether GDF-15 plays a role in peripheral nerve regeneration, we substituted exogenous GDF-15 into 10-mm sciatic nerve gaps in adult rats and compared functional and morphological regeneration to a vehicle control group. Over a period of 11?weeks, multiple functional assessments, including evaluation of pinch reflexes, the Static Sciatic Index and of electrophysiological parameters, were performed. Regenerated nerves were then morphometrically analyzed for the number and quality of regenerated myelinated axons. Substitution of GDF-15 significantly accelerated sensory recovery while the effects on motor recovery were less strong. Although the number of regenerated myelinated axons was significantly reduced after GDF-15 treatment, the regenerated axons displayed advanced maturation corroborating the results of the functional assessments. Our results suggest that GDF-15 is involved in the complex orchestration of peripheral nerve regeneration after lesion.     

Deletion of p75NTR impairs regeneration of peripheral nerves in mice

AimsAfter peripheral nerve injury, p75NTR was upregulated in Schwann cells of the Wallerian degenerative nerves and in motor neurons but down-regulated in the injured sensory neurons. As p75NTR in neurons mediates signals of both neurotrophins and inhibitory factors, it is regarded as a therapeutic target for the treatment of neurodegeneration. However, its physiological function in the nerve regeneration is not fully understood. In the present study, we aimed to examine the role of p75NTR in the regeneration of peripheral nerves.Main methodsIn p75NTR knockout mice (exon III deletion), the sciatic nerves and facial nerves on one side were crushed and regenerating neurons in the facial nuclei and in the dorsal root ganglia were labelled by Fast Blue. The regenerating fibres in the sciatic nerve were also labelled by an anterograde tracer and by immunohistochemistry.Key findingsThe results showed that the axonal growth of injured axons in the sciatic nerve of p75NTR mutant mice was significantly retarded. The number of regenerated neurons in the dorsal root ganglia and in the facial nuclei in p75NTR mutant mice was significantly reduced. Immunohistochemical staining of regenerating axons also showed the reduction in nerve regeneration in p75NTR mutant mice.SignificanceOur data suggest that p75NTR plays an important role in the regeneration of injured peripheral nerves.     

Optic nerve regeneration after intravitreal peripheral nerve implants: trajectories of axons regrowing through the optic chiasm into the optic tracts

We have studied axon regeneration through the optic chiasm of adult rats 30 days after prechiasmatic intracranial optic nerve crush and serial intravitreal sciatic nerve grafting on day 0 and 14 post-lesion. The experiments comprised three groups of treated rats and three groups of controls. All treated animals received intravitreal grafts either into the left eye after both left sided (unilateral) and bilateral optic nerve transection, or into both eyes after bilateral optic nerve transection. Control eyes were all sham grafted on day 0 and 14 post-lesion, and the optic nerves either unlesioned, or crushed unilaterally or bilaterally. No regeneration through the chiasm was seen in any of the lesioned control optic nerves. In all experimental groups, large numbers of axons regenerated across the optic nerve lesions ipsilateral to the grafted eyes, traversed the short distal segment of the optic nerve and invaded the chiasm without deflection. Regeneration was correlated with the absence of the mesodermal components in the scar. In all cases, axon regrowth through the chiasm appeared to establish a major crossed and a minor uncrossed projection into both optic tracts, with some aberrant growth into the contralateral optic nerve. Axons preferentially regenerated within the degenerating trajectories from their own eye, through fragmented myelin and axonal debris, and reactive astrocytes, oligodendrocytes, microglia and macrophages. In bilaterally lesioned animals, no regeneration was detected in the optic nerve of the unimplanted eye. Although astrocytes became reactive and their processes proliferated, the architecture of their intrafascicular processes was little perturbed after optic nerve transection within either the distal optic nerve segment or the chiasm. The re-establishment of a comparatively normal pattern of passage through the chiasm by regenerating axons in the adult might therefore be organised by this relatively immutable scaffold of astrocyte processes. Binocular interactions between regenerating axons from both nerves (after bilateral optic nerve transection and intravitreal grafting), and between regenerating axons and the intact transchiasmatic projections from the unlesioned eye (after unilateral optic nerve lesions and after ipsilateral grafting) may not be important in establishing the divergent trajectories, since regenerating axons behave similarly in the presence and absence of an intact projection from the other eye.     

Enhancement of nerve regeneration and orientation across a gap with a nerve graft within a vein conduit graft: a functional, stereological, and electrophysiological study

In this study, the right sciatic nerves of 40 rats were used to determine whether a nerve graft within a vein graft might accelerate and facilitate axonal regeneration, compared with a nerve graft alone. The animals were separated into four groups, as follows: group 1, sham control; group 2 (control), segmental nerve resection and no repair; group 3, segmental nerve resection and nerve grafting; group 4, segmental nerve resection and reconstruction with a nerve graft within a vein conduit graft. For all groups, sciatic functional indices were calculated before the operation and on postoperative days 7 and 90. On postoperative day 90, the sciatic nerves were reexposed and nerve conduction velocities were recorded. The sciatic nerves were harvested from all groups for counting of the myelinated axons with a stereological method. No statistically significant differences with respect to return of gait function, axon count, or nerve conduction were noted between groups 3 and 4 (p > 0.05). However, functional recovery in group 4 on postoperative day 90 was significant, compared with group 2 (p < 0.05); the recovery difference between groups 2 and 3 was not significant (p > 0.05). This study was not able to demonstrate any functional benefits with the use of a nerve graft within a vein graft, compared with standard nerve grafting.     

A nanofibrous PHBV tube with Schwann cell as artificial nerve graft contributing to Rat sciatic nerve regeneration across a 30-mm defect bridge

Abstract

A nanofibrous PHBV nerve conduit has been used to evaluate its efficiency based on the promotion of nerve regeneration in rats. The designed conduits were investigated by physical, mechanical and microscopic analyses. The conduits were implanted into a 30-mm gap in the sciatic nerves of the rats. Four months after surgery, the regenerated nerves were evaluated by macroscopic assessments and histology. This polymeric conduit had sufficiently high mechanical properties to serve as a nerve guide. The results demonstrated that in the nanofibrous graft with cells, the sciatic nerve trunk had been reconstructed with restoration of nerve continuity and formatted nerve fibers with myelination. For the grafts especially the nanofibrous conduits with cells, muscle cells of gastrocnemius on the operated side were uniform in their size and structures. This study proves the feasibility of artificial conduit with Schwann cells for nerve regeneration by bridging a longer defect in a rat model.     

Effect of early mobilization on healing of nerve repair: histologic observations in a canine model

The effect of early mobilization on the healing of nerve repair was studied in a canine model. Median and ulnar nerves in the left wrist of 16 adult mongrel dogs were transected and immediately repaired. No motion of the repaired forelimb was allowed in the immobilized group (n = 10), while controlled passive motion between 30 and 90 degrees of wrist flexion was begun on the first postoperative day for 10 minutes twice daily in the mobilized group (n = 6). The pattern of revascularization and collagen formation at neurorrhaphy was examined by transillumination of India ink-injected specimen and by conventional histologic sections. Revascularization of nerve repair was found to occur by ingrowth of capillaries from proximal and distal nerve ends, which typically crossed the neurorrhaphy by 3 weeks in the immobilized group. Following early mobilization, there was a persistent "hypovascular zone" at the nerve repair site for up to 6 weeks. In addition, more scar tissue was generated by early motion according to gross observation and quantitative collagen analysis. Early mobilization, therefore, seems to impede nerve regeneration by delaying revascularization and enhancing scar formation.     

Variable spatial magnetic field influences peripheral nerves regeneration in rats

Generator of spatial magnetic field is one of most recent achievements among the magnetostimulators. This apparatus allows to obtain the rotating magnetic field. This new method may be more effective than other widely used techniques of magnetostimulation and magnetotherapy. We investigated the influence of alternating, spatial magnetic field on the regeneration of the crushed rat sciatic nerves. Functional and morphological evaluations were used. After crush injury of the right sciatic nerve, Wistar C rats (n?=?80) were randomly divided into four groups (control and three experimental). The experimental groups (A, B, C) were exposed (20?min/day, 5?d/week, 4 weeks) to alternating spatial magnetic field of three different intensities. Sciatic Functional Index (SFI) and tensometric assessments were performed every week after nerve crush. Forty-eight hours before the sacrificing of animals, DiI (1,1’-di-octadecyl-3,3,3’,3’-tetramethyloindocarbocyanine perchlorate) was applied 5?mm distally to the crush site. Collected nerves and dorsal root ganglia (DRG) were subjected to histological and immunohistochemical staining. The survival rate of DRG neurons was estimated. Regrowth and myelination of the nerves was examined. The results of SFI and tensometric assessment showed improvement in all experimental groups as compared to control, with best outcome observed in group C, exposed to the strongest magnetic field. In addition, DRG survival rate and nerve regeneration intensity were significantly higher in the C group. Above results indicate that strong spatial alternating magnetic field exerts positive effect on peripheral nerve regeneration and its application could be taken under consideration in the therapy of injured peripheral nerves.     

The Neurotrophic Effects and Mechanism of Action for FK1706 in Neurorrhaphy Rat Models and SH-SY5Y Cells

FK1706 is a novel non-immunosuppressive immunophilin ligand with neurotrophic activity and exerts its neurotrophic effect through NGF. The present study aimed to elaborate on the neurotrophic activity and the mechanism of action of FK1706 in end-to-side neurorrhaphy rats and SH-SY5Y cells. In the regenerating nerves of neurorrhaphy rats, FK1706 increased the thickness of myelin sheath and the level of nerve regeneration-related proteins. The mechanism of action of FK1706 on neurite regrowth was elucidated in vitro by incubating SH-SY5Y cells in different conditions (Control, NGF, FK1706, NGF?+?FK1706, NGF?+?FK1706?+?geldanamycin). Under the conditions where NGF was used, the phosphorylation level of major proteins (Raf-1 and ERK) in the Ras/Raf/MAPK/ERK signaling pathway related to SH-SY5Y cell proliferation was significantly enhanced following the application of FK1706. The number of viable cells, cell viability and neurite length of SH-SY5Y cells was maximal when NGF and FK1706 were used simultaneously. The binding level of HSP90 and Raf-1 in FK1706 group was the highest. These results indicated that FK1706 could significantly promote nerve regeneration after neurorrhaphy. The putative mechanism of action stated that FK1706 could promote the binding of HSP90 and Raf-1, make Raf-1 continue to be activated, thereby affecting key proteins in the Ras/Raf/MAPK/ERK signaling pathway related to the neurotrophic effects of NGF to promote the proliferation and neurite regrowth of nerve cells.