Administration of low-dose FK 506 accelerates histomorphometric regeneration and functional outcomes after allograft nerve repair in a rat model

A Novel Approach to Peripheral Nerve Regeneration: Local FK-506 Delivery Using a Reservoir Flap Model

PURPOSE

Peripheral nerve injuries can lead to lasting functional impairments, impacting movement and quality of life. FK-506, a widely used immunosuppressant, has demonstrated potential in promoting nerve regeneration in addition to its immunosuppressive effects. This study investigates the use of a local reservoir flap to deliver FK-506 directly to the nerve injury site, aiming to enhance nerve regeneration while minimizing systemic immunosuppression.

MATERIALS AND METHODS

Sciatic nerve injuries were surgically induced in 24 rats, which were divided into control, 0.5 mg/kg FK-506 (Exp 1), and 2.0 mg/kg FK-506 (Exp 2) groups. A superficial inferior epigastric artery flap served as a reservoir for FK-506, allowing direct delivery to the injury site. FK-506 was administered intermittently over a 4-week period. Outcomes included the Sciatic Functional Index (SFI), muscle recovery (width and weight), nerve morphology, expression of neurogenic markers such as GDNF, immune cell counts, and body weight.

RESULTS

Exp 1 (0.5 mg/kg) demonstrated significant improvements in SFI, GDNF expression, and muscle width compared to the control and high-dose groups. These findings suggest that FK-506 administration via a reservoir flap, particularly at a lower dose, supports effective nerve regeneration. Additionally, FK-506 treatment did not result in significant changes in immune cell profiles or body weight, indicating minimal systemic effects.

CONCLUSION

Localized FK-506 administration via a reservoir flap effectively enhances peripheral nerve regeneration and minimizes systemic immunosuppression, making it a promising approach for clinical application in treating peripheral nerve injuries.

Time course of functional recovery after 1 cm sciatic nerve resection in rats with or without surgical intervention - measured by grip strength and locomotor activity

The rat sciatic nerve (SN) is the most frequently used model in experimental research on peripheral nerve injuries. Within the broad range of evaluation methods to determine the experimental outcome, recovery of behavior represents the major criterion to assess functional regeneration. The grasping test indicates when recovery begins and its improvement with time. However, lesions of the SN have yet remained unstudied with this method. Therefore, rats received a SN resection and were divided into experimental groups: 1) control with lesion only, 2) nerve bridge, and 3) autograft. During weekly sessions, the grasping test measured the grip strength, and the locomotor behavior was assessed in the open field. Finally, the nerves were prepared for electrophysiology and histomorphometry. Autograft recovered grasping after 7 weeks with the strongest improvement afterwards. Nerve tube allowed grasping by week 12. Control animals did not recover. In the open field, no differences were observed between the groups. Recordings were possible only in the autograft group, which could be explained by higher number of regenerated fibers. This study indicates that grasping data correspond with physiological and anatomical findings. We conclude that the grasping test is a valid method to evaluate functional recovery after SN resection in rats.

Local delivery of tacrolimus using electrospun poly-ϵ-caprolactone nanofibres suppresses the T-cell response to peripheral nerve allografts

Objective.Repair of nerve gap injuries can be achieved through nerve autografting, but this approach is restricted by limited tissue supply and donor site morbidity. The use of living nerve allografts would provide an abundant tissue source, improving outcomes following peripheral nerve injury. Currently this approach is not used due to the requirement for systemic immunosuppression, to prevent donor-derived cells within the transplanted nerve causing an immune response, which is associated with severe adverse effects. The aim of this study was to develop a method for delivering immunosuppression locally, then to test its effectiveness in reducing the immune response to transplanted tissue in a rat model of nerve allograft repair.Approach.A coaxial electrospinning approach was used to produce poly-ϵ-caprolactone fibre sheets loaded with the immunosuppressant tacrolimus. The material was characterised in terms of structure and tacrolimus release, then testedin vivothrough implantation in a rat sciatic nerve allograft model with immunologically mismatched host and donor tissue.Main results.Following successful drug encapsulation, the fibre sheets showed nanofibrous structure and controlled release of tacrolimus over several weeks. Materials containing tacrolimus (and blank material controls) were implanted around the nerve graft at the time of allograft or autograft repair. The fibre sheets were well tolerated by the animals and tacrolimus release resulted in a significant reduction in lymphocyte infiltration at 3 weeks post-transplantation.Significance.These findings demonstrate proof of concept for a novel nanofibrous biomaterial-based targeted drug delivery strategy for immunosuppression in peripheral nerve allografting.

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.

Local FK506 drug delivery enhances nerve regeneration through fresh, unprocessed peripheral nerve allografts

OBJECTIVE

Nerve allografts offer many advantages in the reconstruction of peripheral nerve gaps: they retain their native microstructure, contain pro-regenerative Schwann cells, are widely available, and avoid donor site morbidity. Unfortunately, clinical use of nerve allografts is limited by the need for systemic immunosuppression and its adverse effects. To eliminate the toxicity of the systemic immunosuppressant FK506, we developed a local FK506 drug delivery system (DDS) to provide drug release over 28 days. The study objective was to investigate if the local FK506 DDS enhances nerve regeneration in a rodent model of nerve gap defect reconstruction with immunologically-disparate nerve allografts.

METHODS

In male Lewis rats, a common peroneal nerve gap defect was reconstructed with either a 20 mm nerve isograft from a donor Lewis rat or a 20 mm fresh, unprocessed nerve allograft from an immunologically incompatible donor ACI rat. After 4 weeks of survival, nerve regeneration was evaluated using retrograde neuronal labelling, quantitative histomorphometry, and serum cytokine profile.

RESULTS

Treatment with both systemic FK506 and the local FK506 DDS significantly improved motor and sensory neuronal regeneration, as well as histomorphometric indices including myelinated axon number. Rats with nerve allografts treated with either systemic or local FK506 had significantly reduced serum concentrations of the pro-inflammatory cytokine IL-12 compared to untreated vehicle control rats with nerve allografts. Serum FK506 levels were undetectable in rats with local FK506 DDS.

INTERPRETATION

The local FK506 DDS improved motor and sensory nerve regeneration through fresh nerve allografts to a level equal to that of either systemic FK506 or nerve isografting. This treatment may be clinically translatable in peripheral nerve reconstruction or vascularized composite allotransplantation.

All hands on deck: Hand replantation versus transplantation

Objectives:

Our hands play a remarkable role in our activities of daily living and the make-up of our identities. In the United States, an estimated 41,000 individuals live with upper limb loss. Our expanding experience in limb transplantation—including operative techniques, rehabilitation, and expected outcomes—has often been based on our past experience with replantation. Here, we undertake a systematic review of replantation with transplantation in an attempt to better understand the determinants of outcome for each and to provide a summary of the data to this point.

Methods:

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we conducted PubMed searches from 1964 to 2013 for articles in English. In total, 53 primary and secondary source articles were found to involve surgical repair (either replantation or transplantation) for complete amputations at the wrist and forearm levels. All were read and analyzed.

Results:

Hand replantations and transplantations were compared with respect to pre-operative considerations, surgical techniques, post-operative considerations and outcomes, including motor, sensation, cosmesis, patient satisfaction/quality of life, adverse events/side effects, financial costs, and overall function. While comparison of data is limited by heterogeneity, these data support our belief that good outcomes depend on patient expectations and commitment.

Conclusion:

When possible, hand replantation remains the primary option after acute amputation. However, when replantation fails or is not possible, hand transplantation appears to provide at least equal outcomes. Patient commitment, realistic expectations, and physician competence must coincide to achieve the best possible outcomes for both hand replantation and transplantation.

Tacrolimus- and Nerve Growth Factor-Treated Allografts for Neural Tissue Regeneration

Treatment of injured peripheral nerves, especially long-distance nerve defects, remains a significant challenge in regenerative medicine due to complex biological conditions and a lack of biomaterials for effective nerve reconstruction. Without proper treatment, nerve injury leads to motor and sensory dysfunction. Here, we have developed an efficacious nerve allograft treated with a dual drug containing acrolimus and nerve growth factor to bridge the nerve gap and achieve rapid neural tissue recovery without immunological rejection. The recovery of the structure, activity, and function of rats treated with the dual drug-treated allograft was investigated by walking track analysis and electrophysiological measurement. The sciatic functional index was measured to be -3.0 after a 12-week treatment. The nerve conduction velocity, peak latency, and peak amplitude of the nerve action potentials demonstrate the functional recovery of the nerve. To study the synergistic effect of the dual drug on the growth of neurites, a neural cell hypoxia model was created. The dual drug exhibited a high efficiency in promoting the growth of nerve cells under the nerve injury-induced hypoxic condition. The dual drug could protect the cells against antioxidative damage from hypoxia by the expression of heat shock protein, hypoxia-inducible factor, β-tubulin, and vimentin.

Acute Limb Shortening for Major Near and Complete Upper Extremity Amputations with Associated Neurovascular Injury: A Review of the Literature

In the setting a near or complete upper extremity amputations with significant soft tissue loss and neurovascular compromise, upper extremity surgeons are faced with the challenge of limb salvage. There are a multitude of treatment options for managing skeletal and soft tissue injuries including provisional fixation, staged reconstruction, and an acute shortening osteotomy with primary rigid internal fixation. However, many complications are associated with these techniques. Complications of provisional fixation include pin tract infection and loosening, tethering of musculotendinous units, nonunion, and additional surgeries. Staged reconstruction includes a variety of techniques: distraction osteogenesis, bone transport, or vascularized and non-vascularized structural autograft or allograft, but the risks often outweigh the benefits. Risks include nonunion, postoperative vascular complications necessitating reoperation, and the inability to return to the previous level of function at an average of 24 months. Acute shortening osteotomy with internal fixation offers the advantage of a single-stage procedure that provides for decreasing the soft tissue loss, provides a rigid platform to protect the delicate neurovascular repair, and alleviates unwanted tension at the repair sites. This review discusses the literature on the surgical treatment of severe upper extremity trauma with associated neurovascular injury over the past 75 years, and aims to evaluate the indications, surgical techniques, clinical and functional outcomes, and complications associated with acute shortening osteotomy with rigid internal fixation. Although this technique is not without risks, it is well-tolerated in the acute setting with a complication profile comparable to other techniques of fixation while remaining a single procedure.

Ginkgo biloba extract (EGb 761) promotes peripheral nerve regeneration and neovascularization after acellular nerve allografts in a rat model

This study aimed to investigate whether or not ginkgo biloba extract (EGb 761) enhances peripheral nerve regeneration and vascularization after repair using acellular nerve allografts (ANA). Seventy-two Sprague-Dawley rats were randomly divided into three experimental groups: a unilateral 15-mm sciatic nerve defect was created and repaired with an autologous graft (autograft group); the same defect was repaired with an 18 mm ANA with an i.p. injection of normal saline for 10 days (saline group); and in the final group, the same defect was repaired with an 18 mm ANA with an i.p. injection of EGb 761 for 10 days (EGb 761 group). Axon outgrowth and vascularization were evaluated by immunocytochemistry 14 days post-implantation. The expression of genes associated with angiogenesis was analyzed by real-time polymerase chain reaction (PCR) seven days post-implantation. Compared with the saline group, rats in the EGb 761 group significantly increased the number of myelinated fibers and the average diameter of the nerves within the graft. There is no significant difference between the EGb 761 group and the autograft group. The expression of CD34 and NF200 was significantly higher in the EGb 761 group than in the saline group. Additionally, EGb 761 treatment increased the expression of several angiogenesis-related genes, including Vegf, SOX18, Prom 1, and IL-6. In conclusion, ANA repair with EGb 761 treatment demonstrates effects on peripheral nerve regeneration and vascularization that are equal to those of autologous graft repair, and that are superior to ANA repair alone.

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.

Improving peripheral nerve regeneration: from molecular mechanisms to potential therapeutic targets

Peripheral nerve injury is common especially among young individuals. Although injured neurons have the ability to regenerate, the rate is slow and functional outcomes are often poor. Several potential therapeutic agents have shown considerable promise for improving the survival and regenerative capacity of injured neurons. These agents are reviewed within the context of their molecular mechanisms. The PI3K/Akt and Ras/ERK signaling cascades play a key role in neuronal survival. A number of agents that target these pathways, including erythropoietin, tacrolimus, acetyl-l-carnitine, n-acetylcysteine and geldanamycin have been shown to be effective. Trk receptor signaling events that up-regulate cAMP play an important role in enhancing the rate of axonal outgrowth. Agents that target this pathway including rolipram, testosterone, fasudil, ibuprofen and chondroitinase ABC hold considerable promise for human application. A tantalizing prospect is to combine different molecular targeting strategies in complementary pathways to optimize their therapeutic effects. Although further study is needed prior to human trials, these modalities could open a new horizon in the clinical arena that has so far been elusive.

Human periodontal ligament stem cells repair mental nerve injury

Human periodontal ligament stem cells are easily accessible and can differentiate into Schwann cells. We hypothesized that human periodontal ligament stem cells can be used as an alternative source for the autologous Schwann cells in promoting the regeneration of injured peripheral nerve. To validate this hypothesis, human periodontal ligament stem cells (1 × 10⁶) were injected into the crush-injured left mental nerve in rats. Simultaneously, autologous Schwann cells (1 × 10⁶) and PBS were also injected as controls. Real-time reverse transcriptase polymerase chain reaction showed that at 5 days after injection, mRNA expression of low affinity nerve growth factor receptor was significantaly increased in the left trigeminal ganglion of rats with mental nerve injury. Sensory tests, histomorphometric evaluation and retrograde labeling demonstrated that at 2 and 4 weeks after injection, sensory function was significantly improved, the numbers of retrograde labeled sensory neurons and myelinated axons were significantly increased, and human periodontal ligament stem cells and autologous Schwann cells exhibited similar therapeutic effects. These findings suggest that transplantation of human periodontal ligament stem cells show a potential value in repair of mental nerve injury.

Improvement of peripheral nerve defects using a silicone conduit filled with hepatocyte growth factor

OBJECTIVE

To assess local effects of hepatocyte growth factor (HGF) on peripheral nerve repair in a rat sciatic nerve transection model.

STUDY DESIGN

Sixty male, healthy, white Wistar rats were randomized into 4 experimental groups: In the sham-operated group, sciatic nerve was exposed and manipulated. In the transected control group, the left sciatic nerve was transected. In the silicone graft group (SIL), a 10-mm defect was made and bridged using a silicone tube. The graft was filled with phosphate-buffered saline in the SIL group and with HGF in the SIL/HGF group.

RESULTS

Behavioral testing, sciatic nerve functional study, gastrocnemius muscle mass measurement, and morphometric indices found earlier regeneration of axons in the SIL/HGF than in the SIL group (P < .05). Immunohistochemical study clearly found more positive location of reactions to S-100 in the SIL/HGF group than in the SIL group.

CONCLUSIONS

HGF may have clinical implications for the surgical management of patients after facial nerve transection.

Peripheral nerve regeneration following transection injury to rat sciatic nerve by local application of adrenocorticotropic hormone

The objective of this study was to assess local effect of adrenocorticotropic hormone (ACTH) on the functional recovery of the sciatic nerve in a transection model. Sixty male healthy white Wistar rats were randomized into four experimental groups of 15 animals each: In the sham-operated group (SHAM), the sciatic nerve was exposed and manipulated. In the transected group (TC), the left sciatic nerve was transected and the cut nerve ends were fixed in the adjacent muscle. In the silicone graft group (SIL) a 10-mm defect was made and bridged using a silicone tube. The graft was filled with phosphated-buffer saline alone. In the treatment group a silicone tube (SIL/ACTH) was filled with 10 μL ACTH (0.1 mg/mL). Each group was subdivided into three subgroups of five animals each and regenerated nerve fibres were studied at 4, 8 and 12 weeks post operation. Behavioral testing, functional, gastrocnemius muscle mass and morphometric indices showed earlier regeneration of axons in SIL/ACTH than in SIL group (p < 0.05). Immunohistochemistry clearly showed more positive location of reactions to S-100 in SIL/ACTH than in SIL group. ACTH improved functional recovery and morphometric indices of sciatic nerve. This finding supports role of ACTH after peripheral nerve repair and may have clinical implications for the surgical management of patients after nerve transection.

Profiling circulating microRNA expression in a mouse model of nerve allotransplantation

Background

The lack of noninvasive biomarkers of rejection remains a challenge in the accurate monitoring of deeply buried nerve allografts and precludes optimization of therapeutic intervention. This study aimed to establish the expression profile of circulating microRNAs (miRNAs) during nerve allotransplantation with or without immunosuppression.

Results

Balb/c mice were randomized into 3 experimental groups, that is, (1) untreated isograft (Balb/c → Balb/c), (2) untreated allograft (C57BL/6 → Balb/c), and (3) allograft (C57BL/6 → Balb/c) with FK506 immunosuppression. A 1-cm Balb/c or C57BL/6 donor sciatic nerve graft was transplanted into sciatic nerve gaps created in recipient mice. At 1, 3, 7, 10, and 14 d after nerve transplantation, nerve grafts, whole blood, and sera were obtained for miRNA expression analysis with an miRNA array and subsequent validation with quantitative real-time PCR (qRT-PCR). Three circulating miRNAs (miR-320, miR-762, and miR-423-5p) were identified in the whole blood and serum of the mice receiving an allograft with FK506 immunosuppression, within 2 weeks after nerve allotransplantation. However, these 3 circulating miRNAs were not expressed in the nerve grafts. The expression of all these 3 upregulated circulating miRNAs significantly decreased at 2, 4, and 6 d after discontinuation of FK506 immunosuppression. In the nerve graft, miR-125-3b and miR-672 were significantly upregulated in the mice that received an allograft with FK506 only at 7 d after nerve allotransplantation.

Conclusions

We identified the circulating miR-320, miR-762, and miR-423-5p as potential biomarkers for monitoring the immunosuppression status of the nerve allograft. However, further research is required to investigate the mechanism behind the dysregulation of these markers and to evaluate their prognostic value in nerve allotransplantation.

Ketoprofen combined with artery graft entubulization improves functional recovery of transected peripheral nerves

The objective was to assess the local effect of ketoprofen on sciatic nerve regeneration and functional recovery. Eighty healthy male white Wistar rats were randomized into four experimental groups of 20 animals each: In the transected group (TC), the left sciatic nerve was transected and nerve cut ends were fixed in the adjacent muscle. In the treatment group the defect was bridged using an artery graft (AG/Keto) filled with 10 microliter ketoprofen (0.1 mg/kg). In the artery graft group (AG), the graft was filled with phosphated-buffer saline alone. In the sham-operated group (SHAM), the sciatic nerve was exposed and manipulated. Each group was subdivided into four subgroups of five animals each and regenerated nerve fibres were studied at 4, 8, 12 and 16 weeks post operation. Behavioural testing, sciatic nerve functional study, gastrocnemius muscle mass and morphometric indices showed earlier regeneration of axons in AG/Keto than in AG group (p < 0.05). Immunohistochemical study clearly showed more positive location of reactions to S-100 in AG/Keto than in AG group. When loaded in an artery graft, ketoprofen improved functional recovery and morphometric indices of the sciatic nerve. Local usage of this easily accessible therapeutic medicine is cost saving and avoids the problems associated with systemic administration.

The current state of hand transplantation

Hand transplantation is the most common form of modern composite tissue allotransplantation. Successful application of this technology requires a multidisciplinary approach incorporating not only skilled hand surgeons, transplant surgeons, and transplant immunologists, but also hand therapists, psychiatrists, medical specialists, anesthesiologists, and others. Functional outcomes can be life changing for properly selected candidates. Hand transplantation is becoming more common, with more centers offering this relatively new reconstructive modality. Its success depends on proper patient selection, a technically successful operation, postoperative rehabilitation, and an immunotherapy protocol that prevents rejection but has minimal or acceptable morbidity.