Promotion of nerve regeneration in peripheral nerve by short-course FK506 after end-to-side neurorrhaphy

Effect of Tacrolimus and Cyclosporine Immunosuppressants on Peripheral Nerve Regeneration: Systematic Review and Meta-analysis

Peripheral nerve damage is an important cause of seeking medical attention. It occurs when the continuity of structures is interrupted and the propagation of nervous impulses is blocked, affecting the functional capacity of individuals. To assess the effects of the immunosuppressants tacrolimus and cyclosporine on the regeneration of peripheral nerves, a systematic review of the literature was carried out. The articles included were published until September 2018 and proposed to evaluate the effects of the immunosuppressants tacrolimus and cyclosporine on nerve regeneration and neuroprotection, available in the MEDLINE, EMBASE, Cochrane Library, Web of Science, Oxford Pain Relief Database, and LILACS databases. The research analysed a total of 56 articles, of which 22 were included in the meta-analysis. Statistical analysis suggests the protective effect of tacrolimus in the regeneration of the number of myelinated axons (95% confidence interval [CI]: 0.93–2.39; p  < 0.01); however, such effect was not observed in relation to cyclosporine (95%CI: - 0.38–1.18; p  = 0.08) It also suggests that there is a significant relationship between the use of tacrolimus and myelin thickness (95%CI= 2.00–5.71; p  < 0. 01). The use of immunosuppressants in the regeneration of peripheral nerve damage promotes an increase in the number of myelinated axons in general, regardless of the administered dose. In addition, it ensures greater myelin thickness, muscle weight and recovery of the sciatic functional index. However, heterogeneity was high in most analyses performed.

Revitalizing the common peroneal function index for assessing functional recovery following nerve injury

BACKGROUND AND AIMS

Peripheral nerve injury is common with poor functional recovery and consequent high personal and societal costs. Sciatic nerve transection and assessment of recovery using sciatic functional index (SFI) are widely used. SFI is biologically limited as axonal misdirection of axons supplying flexors and extensors in the hindlimb, after nerve injury can lead to synkinetic innervation and function which does not correspond to the degree of axonal regeneration.

METHODS

We reevaluated the use of traditional metrics such as print length (PL), toe spread (TS), and intermediate toe spread (ITS) as well as hock angle at mid-swing as approaches for determining recovery. We used two alternative approaches in discrete cohorts of rats following common peroneal crush injury, transection with repair and critical gap, using transection with ligation as a negative control. We compared walking track analysis (print) with digital capture and kinematics.

RESULTS

PL, TS, and ITS varied as expected after injury. The traditional functional index for common peroneal injury using inked prints failed to describe recovery and we derived new indices to describe recovery (all R²  > 0.88, p < .0001) although pre-injury PFI was never attained by any of the models. Kinematic analysis identified hock angle at mid-swing as a useful predictor of recovery (p < .0001).

INTERPRETATION

Using complementary approaches.

Reconstruction of bladder function and prevention of renal deterioration by means of end-to-side neurorrhaphy in rats with neurogenic bladder

AIMS

To investigate the feasibility of restoring bladder function and prevention of renal deterioration by neurorrhaphy in rats with neurogenic bladder (NB).

METHODS

Forty-two rats were assigned to the end-to-side nerve coaptation group (ECG, n = 16), no nerve coaptation group (NCG, n = 16), and control group (CG, n = 10). In the ECG, the left ventral root (VR) and dorsal root (DR) of L6 and S1 were transected, and the distal stump of L6VR was sutured to the lateral face of L4VR. In the NCG, the left VR and DR of L6 and S1 were transected, but coaptation was not performed. In the CG, no operation was performed. Nerve regeneration, bladder function, and renal function were evaluated by FluoroGold (FG) retrograde tract tracing, cystometry, electrical stimulation, MRI, histology and biochemical assays.

RESULTS

In the ECG, FG-labeled neurons were observed in the left ventral horn of L4 spinal cord. There was a significant increase in intravesical pressure upon stimulation of the left L4VR proximal to the coaptation. Maximum cystometric capacity, post-void residual urine, bladder compliance and weight, serum creatinine, blood urea nitrogen, and fibrotic area of bladder and kidney were lower in the ECG than in the NCG, but higher than the CG. Hydronephrosis was noticed in ECG and NCG rats. Maximum detrusor voiding pressure was higher in the ECG and CG than in the NCG.

CONCLUSIONS

End-to-side neurorrhaphy is a useful method for restoring bladder function and preventing renal injury in rats with NB.

Functional, Histopathological and Immunohistichemical Assessments of Cyclosporine A on Sciatic Nerve Regeneration Using Allografts: A Rat Sciatic Nerve Model

OBJECTIVES

To study the functional, histopathological and immunohistochemical effect of cyclosporine A on sciatic nerve regeneration using allografts in a rat sciatic nerve model.

METHODS

Thirty male white Wistar rats were divided into three experimental groups (n = 10), randomly: Normal control group (NC), allograft group (ALLO), CsA treated group (ALLO/ CsA). In NC group left sciatic nerve was exposed through a gluteal muscle incision and after homeostasis muscle was sutured. In the ALLO group the left sciatic nerve was exposed through a gluteal muscle incision and transected proximal to the tibio-peroneal bifurcation where a 10 mm segment was excised. The same procedure was performed in the ALLO/ CsA group and the animals were treated with interaperitoneal administration of cyclosporine A. The harvested nerves of the rats of ALLO group were served as allograft for ALLO/ CsA group and vice versa. The NC and ALLO groups received 300 μL sterile olive oil interaperitoneally once a day for one week and the ALLO/ CsA group received 300 μL CsA (1mg/kg/day) interaperitoneally once a day for one week.

RESULTS

Behavioral, functional, biomechanical and gastrocnemius muscle mass showed earlier regeneration of axons in ALLO/ CsA than in ALLO group (p=0.001). Histomorphometic and immunohistochemical studies also showed earlier regeneration of axons in ALLO/ CsA than in ALLO group (p=0.034).

CONCLUSION

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

The effect of tacrolimus on facial nerve injury: Histopathological findings in a rabbit model

HYPOTHESIS

Tacrolimus helps healing of facial nerve injury.

BACKGROUND

Positive effects of tacrolimus on axon regeneration and healing of injured peripheral nerves (eg. sciatic nerve) have been reported in the literature. Tacrolimus may be an additional treatment method that could improve the nerve healing after surgical treatment of cut injury of facial nerve.

METHODS

20 New Zealand rabbits were randomly separated into control and study groups of 10. In control group, no medical treatment was given after facial nerve anastomosis, and the animals were followed up for 2months. In the study group rabbits were given 1mg/kg/day tacrolimus subcutaneously for 2months after the facial nerve anastomosis. The histopathologic findings of axon regeneration like axon myelination were analyzed in both groups under electron and light microscopy. The data obtained in the groups were compared.

RESULTS

Greater axon diameters, thicker myelin sheaths, and higher total number of myelinated axons were found in the tacrolimus group, suggesting better regeneration in this group when compared to the control group. There was less vacuolar degeneration in the study group. All these findings suggest that tacrolimus positively affects healing after facial nerve anastomosis.

CONCLUSION

The results of this study indicate that tacrolimus has favorable effects on the healing process of the facial nerve after end-to-end anastomosis. Tacrolimus may be a promising agent in the future for nerve regeneration following traumatic facial paralysis surgery.

Effects of hyaluronic acid and tacrolimus on the prevention of perineural scar formation and on nerve regeneration after sciatic nerve repair in a rabbit model

PURPOSE

Scar formation after injured peripheral nerve repair is a significant clinical problem because it prevents nerve regeneration. The aim of this study was to investigate and compare the effects of hyaluronic acid (HA) and tacrolimus (FK506) on peripheral nerve regeneration in rabbits after the drugs were topically applied at the site of nerve repair.

METHODS

Thirty adult male European rabbits (Oryctolagus cuniculus), ranging in weight from 2.5 to 3 kg, were randomly assigned to three groups: the HA and FK506 groups comprised the experimental groups, while the saline group served as the control. At week 12, macroscopic and microscopic evaluations were performed and analyzed.

RESULTS

In general, the macroscopic evaluations (skin and muscle fascia closure and nerve adherence), microscopic evaluations (cellular components, scar tissue formation index, and histomorphological organization), and measurements of nerve diameter and gastrocnemius muscle wet weight demonstrated the positive effects of topical application of these pharmacological agents (HA and FK506); HA and FK506 prevented scar formation and enhanced nerve regeneration. No significant differences in the parameters described above were observed between the HA and FK506 groups (P > 0.05). However, significant differences were observed between both the HA and FK506 groups and the saline group (P < 0.05).

CONCLUSION

Based on our findings, topical application of HA and FK506 exhibits equally positive effects, preventing perineural scar formation and enhancing nerve regeneration after peripheral nerve repair.

Effect of graded nerve pressure injuries on motor function

OBJECT

The purpose of this study was to determine the minimum amount of nerve fibers required to maintain normal motor function after nerve injury in rats.

METHODS

The authors first confirmed that a common peroneal nerve injury caused more aggravating effects on lower limb motor function than tibial nerve injury, as assessed by the static sciatic index (SSI). Thereafter, rats were subjected to varying degrees of crush injury to the common peroneal nerve. At 48 hours after the injury, motor function was assessed using the SSI and slope-walking ability (with slope angles of 30° and 45°). The tibialis anterior muscle, a main muscle innervated by the common peroneal nerve, was removed. Muscle sections were co-labeled with neuronal class III β-tubulin polyclonal antibody to identify the presence of axons and Alexa Fluor 488-conjugated α-bungarotoxin to identify the presence of motor endplates.

RESULTS

The evaluation of neuromuscular innervation showed a correlation between SSI scores and ratios of residual axons (rs = 0.68, p < 0.01), and there was a statistically significant difference between slope-walking ability and ratios of residual axons (p < 0.01). Moreover, the ratios of residual axons in the nerve-crushed rats with normal motor function (SSI above -20) ranged from 36.5% to 88.7%, and those ratios in the success group with slope-walking angles of 30° and 45° ranged from 14.7% to 88.7% and from 39.8% to 88.7%, respectively.

CONCLUSIONS

In this study of rodents, less than half of the motor axons were sufficient to maintain normal motor function of the lower limb.

Use of FK506 and bone marrow mesenchymal stem cells for rat hind limb allografts

Dark Agouti rat donor hind limbs were orthotopically transplanted into Lewis rat recipients to verify the effects of bone marrow mesenchymal stem cells on neural regeneration and functional recovery of allotransplanted limbs in the microenvironment of immunotolerance. bone marrow mesenchymal stem cells were intramuscularly (gluteus maximus) injected with FK506 (tacrolimus) daily, and were transplanted to the injured nerves. Results indicated that the allograft group not receiving therapy showed severe rejection, with transplanted limbs detaching at 10 days after transplantation with complete necrosis. The number of myelinated axons and Schwann cells in the FK506 and FK506 + bone marrow mesenchymal stem cells groups were significantly increased. We observed a lesser degree of gastrocnemius muscle degeneration, and increased polymorphic fibers along with other pathological changes in the FK506 + bone marrow mesenchymal stem cells group. The FK506 + bone marrow mesenchymal stem cells group showed significantly better recovery than the autograft and FK506 groups. The results demonstrated that FK506 improved the immune microenvironment. FK506 combined with bone marrow mesenchymal stem cells significantly promoted sciatic nerve regeneration, and improved sensory recovery and motor function in hind limb allotransplant.

Tacrolimus reduces scar formation and promotes sciatic nerve regeneration

A sciatic nerve transection and repair model was established in Sprague-Dawley rats by transecting the tendon of obturator internus muscle in the greater sciatic foramen and suturing with nylon sutures. The models were treated with tacrolimus gavage (4 mg/kg per day) for 0, 2, 4 and 6 weeks. Specimens were harvested at 6 weeks of intragastric administration. Masson staining revealed that the collagen fiber content and scar area in the nerve anastomosis of the sciatic nerve injury rats were significantly reduced after tacrolimus administration. Hematoxylin-eosin staining showed that tacrolimus significantly increased myelinated nerve fiber density, average axon diameter and myelin sheath thickness. Intragastric administration of tacrolimus also led to a significant increase in the recovery rate of gastrocnemius muscle wet weight and the sciatic functional index after sciatic nerve injury. The above indices were most significantly improved at 6 weeks after of tacrolimus gavage. The myelinated nerve fiber density in the nerve anastomosis and the sciatic nerve functions had a significant negative correlation with the scar area, as detected by Spearman’s rank correlation analysis. These findings indicate that tacrolimus can promote peripheral nerve regeneration and accelerate the recovery of neurological function through the reduction of scar formation.

Hericium erinaceus (Bull.: Fr.) Pers., a medicinal mushroom, activates peripheral nerve regeneration

OBJECTIVE

To study the ability of aqueous extract of Hericium erinaceus mushroom in the treatment of nerve injury following peroneal nerve crush in Sprague-Dawley rats.

METHODS

Aqueous extract of Hericium erinaceus was given by daily oral administration following peroneal nerve crush injury in Sprague-Dawley rats. The expression of protein kinase B (Akt) and mitogen-activated protein kinase (MAPK) signaling pathways; and c-Jun and c-Fos genes were studied in dorsal root ganglia (DRG) whereas the activity of protein synthesis was assessed in peroneal nerves by immunohistochemical method.

RESULTS

Peripheral nerve injury leads to changes at the axonal site of injury and remotely located DRG containing cell bodies of sensory afferent neurons. Immunofluorescence studies showed that DRG neurons ipsilateral to the crush injury in rats of treated groups expressed higher immunoreactivities for Akt, MAPK, c-Jun and c-Fos as compared with negative control group (P <0.05). The intensity of nuclear ribonucleoprotein in the distal segments of crushed nerves of treated groups was significantly higher than in the negative control group (P <0.05).

CONCLUSION

H. erinaceus is capable of promoting peripheral nerve regeneration after injury. Potential signaling pathways include Akt, MAPK, c-Jun, and c-Fos, and protein synthesis have been shown to be involved in its action.

Clinical applications of end-to-side neurorrhaphy: an update

End-to-side neurorrhaphy constitutes an interesting option to regain nerve function after damage in selected cases, in which conventional techniques are not feasible. In the last twenty years, many experimental and clinical studies have been conducted in order to understand the biological mechanisms and to test the effectiveness of this technique, with contrasting results. In this updated review, we consider the state of the art about end-to-side coaptation, focusing on all the current clinical applications, such as sensory and mixed nerve repair, treatment of facial palsy, and brachial plexus injuries and painful neuromas management.

Effect of FK506 in reducing scar formation by inducing fibroblast apoptosis after sciatic nerve injury in rats

We previously demonstrated that FK506, a generally applied immunosuppressant in organ transplantation, could promote peripheral nerve regeneration through reducing scar formation. However, little is known about how FK506 reduces scar formation. Herein we investigated the influence of FK506 on fibroblast proliferation and its correlation with scar formation after sciatic nerve injury in rats, and further explored the effect of FK506 on fibroblast proliferation and apoptosis in vitro. Masson staining and immunohistochemistry revealed that scar area and fibroblast number in the nerve anastomosis of sciatic nerve-injured rats were significantly reduced after FK506 administration. The scar area had a significant positive correlation with the fibroblast number, as detected by linear correlation analysis. CCK-8 assay and flow cytometry indicated that FK506 also inhibited proliferation and induced apoptosis of fibroblasts in vitro. It was primarily phosphorylation of JNK and ERK that were activated during the apoptosis of fibroblast. Pretreatment of cells with JNK inhibitor, SP600125, or ERK inhibitor, PD98059, could inhibit FK506-induced fibroblast apoptosis, respectively. Moreover, simultaneous application of both inhibitors had additive roles in cell protection from apoptosis. These results suggest that FK506-induced fibroblast apoptosis contributes to the suppression of fibroblast proliferation and then results in the reduction of scar formation in sciatic nerve-injured rat, and that JNK and ERK are involved in FK506-induced fibroblast apoptosis.

Tacrolimus enhances the recovery of normal laryngeal muscle fibre distribution after reinnervation

OBJECTIVES

To assess the recovery of various muscle fibre types in the posterior cricoarytenoid muscle after laryngeal reinnervation in the rat, and to determine the influence of tacrolimus on this process.

METHODS

Four groups of rats underwent resection and anastomosis of the left vagus nerve, and were administered either tacrolimus at a low dose or an immunosuppressive dose, or cyclosporin A at a low dose or an immunosuppressive dose. A fifth group received surgery alone, and a sixth group received neither surgery nor drug treatment (healthy group). Muscles were removed for immunohistochemical analysis 45 days after surgery.

RESULTS

There was no difference in the proportion of types 1, 2a and 2b muscle fibres, comparing the immunosuppressive tacrolimus group and the healthy group, whereas there were fewer type 1 fibres in the group receiving surgery alone, compared with the healthy group (7 vs 12.1 per cent, respectively; p = 0.0303).

CONCLUSION

Tacrolimus enhanced the recovery of normal laryngeal muscle fibres after reinnervation in the rat, indicating a possible role in laryngeal transplantation.

Effects of topically administered FK506 on sciatic nerve regeneration and reinnervation after vein graft repair of short nerve gaps

Object

Despite the development of various nerve coaptation materials and techniques, achievement of desired functional peripheral nerve regeneration is still inadequate, and repair of peripheral nerve injuries is still one of the most challenging tasks and concerns in neurosurgery. The effect of an FK506-loaded vein graft as an in situ delivery system for FK506 in bridging the defects was studied using a rat sciatic nerve regeneration model.

Methods

A 10-mm sciatic nerve defect was bridged using an inside-out vein graft (IOVG) filled with 10 μl of a carrier-drug dilution (10 ng/ml FK506) in the IOVG/FK506 group. In the IOVG control group, the vein was filled with the same volume of carrier dilution alone. The regenerated fibers were studied 4, 8, and 12 weeks after surgery.

Results

Functional study confirmed faster recovery of the regenerated axons in the IOVG/FK506 group than in the IOVG group (p < 0.05). There was a statistically significant difference between the mean gastrocnemius muscle weight ratios of the IOVG/FK506 and IOVG control groups (p < 0.05). Morphometric indices of regenerated fibers showed that the number and diameter of the myelinated fibers were significantly higher in the IOVG/FK506 group than in the IOVG control group. Immunohistochemical analysis showed more positive immunoreactivity to S100 protein in the IOVG/FK506 group than in the IOVG control group.

Conclusions

When loaded in a vein graft, FK506 resulted in improvement of functional recovery and quantitative 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.

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

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

Neuroproteomics approaches to decipher neuronal regeneration and degeneration

Given the complexity of brain and nerve tissues, systematic approaches are essential to understand normal physiological conditions and functional alterations in neurological diseases. Mass spectrometry-based proteomics is increasingly used in neurosciences to determine both basic and clinical differential protein expression, protein-protein interactions, and post-translational modifications. Proteomics approaches are especially useful to understand the mechanisms of nerve regeneration and degeneration because changes in axons following injury or in disease states often occur without the contribution of transcriptional events in the cell body. Indeed, the current understanding of axonal function in health and disease emphasizes the role of proteolysis, local axonal protein synthesis, and a broad range of post-translational modifications. Deciphering how axons regenerate and degenerate has thus become a postgenomics problem, which depends in part on proteomics approaches. This review focuses on recent proteomics approaches designed to uncover the mechanisms and molecules involved in neuronal regeneration and degeneration. It emerges that the principal degenerative mechanisms converge to oxidative stress, dysfunctions of axonal transport, mitochondria, chaperones, and the ubiquitin-proteasome systems. The mechanisms regulating nerve regeneration also impinge on axonal transport, cytoskeleton, and chaperones in addition to changes in signaling pathways. We also discuss the major challenges to proteomics work in the nervous system given the complex organization of the brain and nerve tissue at the anatomical, cellular, and subcellular levels.

The efficacy of end-to-end and end-to-side nerve repair (neurorrhaphy) in the rat brachial plexus

Proximal nerve injury often requires nerve transfer to restore function. Here we evaluated the efficacy of end-to-end and end-to-side neurorrhaphy of rat musculocutaneous nerve, the recipient, to ulnar nerve, the donor. The donor was transected for end-to-end, while an epineurial window was exposed for end-to-side neurorrhaphy. Retrograde tracing showed that 70% donor motor and sensory neurons grew into the recipient 3 months following end-to-end neurorrhaphy compared to 40-50% at 6 months following end-to-side neurorrhaphy. In end-to-end neurorrhaphy, regenerating axons appeared as thick fibers which regained diameters comparable to those of controls in 3-4 months. However, end-to-side neurorrhaphy induced slow sprouting fibers of mostly thin collaterals that barely approached control diameters by 6 months. The motor end plates regained their control density at 4 months following end-to-end but remained low 6 months following end-to-side neurorrhaphy. The short-latency compound muscle action potential, typical of that of control, was readily restored following end-to-end neurorrhaphy. End-to-side neurorrhaphy had low amplitude and wide-ranging latency at 4 months and failed to regain control sizes by 6 months. Grooming test recovered successfully at 3 and 6 months following end-to-end and end-to-side neurorrhaphy, respectively, suggesting that powerful muscle was not required. In short, both neurorrhaphies resulted in functional recovery but end-to-end neurorrhaphy was quicker and better, albeit at the expense of donor function. End-to-side neurorrhaphy supplemented with factors to overcome the slow collateral sprouting and weak motor recovery may warrant further exploration.