Different muscle graft denaturing methods and their use for nerve repair

Muscle Grafts with Doxorubicin Pretreatment Produce "Empty Tubes" in the Basal Laminae, Promote Contentious Maturation of the Regenerated Axons, and Bridge 20-mm Sciatic Nerve Defects in Rats

BACKGROUND

 We newly developed a muscle graft that employs a doxorubicin pretreatment technique. The aims of this study were to reveal the biological and morphological features of the muscle tissue in the second week (Study I), to reveal the regeneration outcomes of functional and kinematic assessments of longer-term follow-up (16 weeks, Study II), and to make assessments of the muscle graft with doxorubicin pretreatment in the critical-sized nerve defect model (20 mm, Study III).

METHODS

 A total of 26 adult rats were used in this study. Doxorubicin treatment was accomplished by immersion in a doxorubicin solution for 10 minutes followed by a rinsing procedure. The rats were divided into three groups: the muscle graft with and without doxorubicin pretreatment (M-graft-w-Dox and M-graft-w/o-Dox) groups and the autologous nerve graft (N-graft) group. Assays of apoptosis, immunofluorescent histochemistry including CD68 (macrophage marker), scanning electron microscopy (SEM), morphometrical studies of the regenerated axons, nerve conduction studies, and kinematic studies were performed.

RESULTS

 The M-graft-w-Dox group contained significantly larger numbers of apoptotic cells and CD68-positive cells. SEM revealed the existence of the basal lamina, so called "empty tubes," in the M-graft-w-Dox group. Study II showed contentious maturation of the regenerated axons, especially in the compound muscle action potentials. Study III showed that even at 20 mm, the M-graft-w-Dox group promoted axonal regeneration and functional regeneration.

CONCLUSION

 The M-graft-w-Dox group showed superior regeneration results, and this easy and short-term procedure can expand the muscle graft clinical indication for the treatment of peripheral nerve defects.

[Regeneration of critical injuries of the peripheral nerve with growth factors]

INTRODUCTION

This project aims to study the regeneration of non-repairable lesions of peripheral nerve by muscle grafts enhanced with growth factors.

MATERIAL AND METHODS

The experiment was carried out in two phases. The first one compared direct suture of a critical defect in the sciatic nerve of ten rats, with the interposition of autologous muscle graft, denatured by heat, in another ten. The second phase compared ten rats with nerve repair using an acellular muscle graft, with injection of 2cc of IGF-1 (10mg/ml mecasermin, Injectable solution) into the acellular graft of another ten. A clinical and functional follow-up was carried out including, ambulation, footprint measurement, and "grasping test". . The animals were sacrificed at 90-100 days, and samples obtained for macro- and microscopic studies with toluidine blue, haematoxylin-eosin and Masson's trichrome staining.

RESULTS

The first experiment showed the characteristic findings of nerve tissue in muscle graft level sections. The second was an enhancement of the results: post-surgical clinical improvement, early ambulation, decrease in the rate of pressure ulcers in toes, recovery of the footprint, and increasing the percentage of nerve endings in distal sciatic regeneration (47-62%).

CONCLUSIONS

In this study the experimental and clinical possibilities of nerve defect repair by denatured muscle are demonstrated, confirming the suitability of the technique. Furthermore, it confirms our hypothesis with clinical and cellular determinations enriched by the addition of growth factors that promote nerve regeneration.

Peripheral nerve repair with epimysium conduit

Autologous tissues such as skeletal muscle have high biocampatibility and can effectively promote nerve regeneration compared to other biological and artificial materials; however, the reasonable and effective application of skeletal muscle requires further study. The purpose of this investigation was to assess the possibility of preparing a hollow nerve conduit, termed the epimysium conduit (EMC), using thin crimps of epimysium with skeletal muscle fibers and evaluate its effectiveness in repairing peripheral nerve defects. We prepared nerve conduits containing lumen with the external oblique muscle of the CAG-EFGP transgenic mice using microsurgical techniques for bridge repair of a 5-mm long sciatic nerve defect in wild-type mice. Systematic histological and functional assessments of the regenerated nerves were performed 8 and 12 weeks after surgery. EMC was found to effectively repair the sciatic nerve defect with significantly greater effectiveness than artificial conduits; however, the repair effect of EMC was lower than that of autologous nerve grafting for some parameters. In addition, our findings showed that some EMC-derived cell components migrated into the region of the regenerated nerves and contributed to reconstruction. Based on these findings, we conclude that a hollow conduit prepared with epimysium and a few skeletal muscle fibers is ideal for repairing peripheral nerve defects, and the cell components in the grafts contribute to nerve regeneration and structural remodeling, which provides an alternative option for the emergency primary repair of peripheral nerve defects in clinical practice.

Raman spectral analysis of nasopharyngeal carcinoma cell line CNE2 after microwave radiation

This study aimed to study the effects of microwave radiation on the nasopharyngeal carcinoma cell line CNE2 by Raman spectroscopy. The cells were separated into a control group and radiated groups with radiation times of 2, 5, 10, and 25 min, respectively. Both principal components analysis and support vector machine were employed for statistical analysis of Raman spectra. The results show that the relative content of C-H deformation and amide I begin to change when the radiation time is over 10 min, and principal components analysis further confirms there are significant differences after 10 min of radiation. Moreover, support vector machine is simultaneously used to classify radiated samples from control samples. The classification accuracy is low until the radiation time reaches over 10 min. In conclusion, this study reveals the Raman spectral characteristics of CNE2 under different microwave radiation exposure timesand demonstrates Raman spectroscopy can be a potential method to explore cellular characterization after radiation. The final results may help in elucidating the mechanism by which microwave radiation interacts with tumor cells.

Peripheral nerve reconstruction with collagen tubes filled with denatured autologous muscle tissue in the rat model

Conventional nerve conduits lack cellular and extracellular guidance structures critical for bridging larger defects. In this study, an exogenous matrix for axonal regeneration was provided by pretreated muscle tissue. In 24 rats, 14-mm sciatic nerve segments were resected and surgically reconstructed using one of the following methods: autograft (AG); bovine type I collagen conduit; (MDM) collagen tube filled with modified denatured autologous muscle tissue. For 8 weeks, functional regeneration was evaluated by footprint and video gait analysis. Evaluation was complemented by electrophysiology, as well as qualitative and quantitative structural assessment of nerves and target muscles. Group AG was superior both structurally and functionally, showing higher axon counts, a more normal gait pattern, and less severe muscle atrophy. Fiber quality (fiber size and myelin thickness) was highest in group MDM, possibly related to the myelin-producing effect of muscular laminin. However, axon count was lowest in this group, and ultrastructural analysis of the denatured muscle tissue showed areas of incomplete denaturation that had acted as a mechanical barrier for regenerating axons. In light of these results, the often advocated use of muscular exogenous matrix for peripheral nerve reconstruction is reviewed in the literature, and its clinical application is critically discussed. In conclusion, combined muscle tubes may have a positive influence on nerve fiber maturation. However, muscle pretreatment is not without risks, and denaturation processes need to be further refined.

Estudo comparativo entre enxerto autógeno e enxerto muscular coberto com tubo de veia autógeno em nervos tibiais de ratos wistar, utilizando o fluoro-gold® como marcador neuronal

Este trabalho teve como objetivo o estudo da regeneração nervosa através da contagem de neurônios comparando duas técnicas cirúrgicas no tratamento da perda de substância nervosa nos membros inferiores em 15 ratos. Inicialmente obteve-se tubo de veia de 12mm de comprimento retirado da jugular externa esquerda. A seguir, opera-se os dois membros inferiores, expondo o nervo tibial de cada lado e ressecando um segmento de 8 mm do nervo, simulando, ao mesmo tempo, a perda de substância e a obtenção do enxerto nervoso autógeno. A reparação da perda de substância do lado esquerdo consistiu numa enxertia convencional simples para a reparação de lesão nervosa por meio de sutura microcirúrgica. A do membro inferior direito foi pela tubulização com 8 mm de enxerto de músculo quadríceps denaturado com nitrogênio líquido coberto com veia jugular. Após quatro meses, os animais foram submetidos à nova cirurgia para exposição dos nervos tibiais ao marcador neuronal Fluoro Gold®. Após 48 horas, foram perfundidos e o segmento medular entre L3 e S1 foi removido e posteriormente cortado em secções de 40 µm. Houve contagem neuronal de todos os cortes e não foram verificadas diferenças estatísticas entre as duas técnicas cirúrgicas.

Bioresorbable glass fibres facilitate peripheral nerve regeneration

This is a proof of principle report showing that fibres of Bioglass 45S5 can form a biocompatible scaffold to guide regrowing peripheral axons in vivo. We demonstrate that cultured rat Schwann cells and fibroblasts grow on Bioglass fibres in vitro using SEM and immunohistochemistry, and provide qualitative and quantitative evidence of axonal regeneration through a Silastic conduit filled with Bioglass fibres in vivo (across a 0.5 cm interstump gap in the sciatic nerves of adult rats). Axonal regrowth at 4 weeks is indistinguishable from that which occurs across an autograft. Bioglass fibres are not only biocompatible and bioresorbable, which are absolute requirements of successful devices, but are also amenable to bioengineering, and therefore have the potential for use in the most challenging clinical cases, where there are long inter-stump gaps to be bridged.

Primary nerve repair by muscle autografts prepared with local anesthetic

We evaluated the usefulness of muscle autografts obtained immediately after graft preparation with lidocaine injections for primary nerve repair. The right sciatic nerve of adult Wistar rats was sectioned, and muscle grafts obtained 15 min or 24 h after lidocaine injection were used to repair a gap 1.5 cm long. Axon and fiber diameters, as well as myelin thickness, decreased to similar extents for grafts of both time intervals. The G-ratios in the distal stumps of both groups were not different from controls, indicating that regenerated axons had a proper level of myelination. The ultrastructural appearance of the neuromuscular junctions was similar to that of normal samples. These results indicate that there are no restrictions to the use of a muscle graft for primary nerve repair, immediately after lidocaine injection, since the nerve regeneration was comparable to that observed with this type of graft used 24 h after being prepared.

Use of Skeletal Muscle Tissue in Peripheral Nerve Repair: Review of the Literature

The management of peripheral nerve injury continues to be a major clinical challenge. The most widely used technique for bridging defects in peripheral nerves is the use of autologous nerve grafts. This technique, however, necessitates a donor nerve and corresponding deficit. Many alternative techniques have thus been developed. The use of skeletal muscle tissue as graft material for nerve repair is one example. The rationale regarding the use of the skeletal muscle tissue technique is the availability of a longitudinally oriented basal lamina and extracellular matrix components that direct and enhance regenerating nerve fibers. These factors provide superiority over other bridging methods as vein grafts or (non)degradable nerve conduits. The main disadvantages of this technique are the risk that nerve fibers can grow out of the muscle tissue during nerve regeneration, and that a donor site is necessary to harvest the muscle tissue. Despite publications on nerve conduits as an alternative for peripheral nerve repair, autologous nerve grafting is still the standard care for treatment of a nerve gap in the clinical situation; however, the use of the skeletal muscle tissue technique can be added to the surgeon's arsenal of peripheral nerve repair tools, especially for bridging short nerve defects or when traditional nerve autografts cannot be employed. This technique has been investigated both experimentally and clinically and, in this article, an overview of the literature on skeletal muscle grafts for bridging peripheral nerve defects is presented.

The use of a muscle graft to repair a segmentary nerve defect

The use of a devitalized skeletal muscle graft and conventional nerve graft to repair a 5mm long segmentary sciatic nerve lesion was studied in rats by means of functional, morphometric and spinal cord motor neuron cell response evaluation. Thirty-four rats were used and divided into four groups according to the procedure: (1) sham operation; (2) conventional nerve grafting; (3) muscle grafting; (4) unrepaired lesion. The sciatic functional index (SFI) was evaluated every fortnight up to the 105th postoperative day by measuring three parameters in the rats' footprint. The animals of Groups 2 and 3 presented initial complete functional loss, followed by slow but steady recovery, with final similar SFIs. The histologic and morphometric studies showed an increased small diameter/thin myelin sheath nerve fiber density distally to the lesion site for both types of graft. An increased population of motor neurons was observed in the anterior horn of the lumbar spinal cord segment with both types of grafts, but not in the control groups. The SFI, histologic and morphometric data did not differ significantly between the two types of graft, thus indicating a similar behavior. The authors conclude that a 5mm long skeletal muscle graft works as well as a conventional nerve graft.

Peripheral nerve regeneration through a long detergent-denatured muscle autografts in rabbits

Muscle segments excised from rabbit biceps femoris muscles were treated with detergent sodium dodecyl sulphate to denature cellular constituents, and each was autografted in a 5 cm gap of the sciatic nerve in the same rabbit. Axonal regrowth through the grafts and reinnervation into the host sciatic nerves and muscles were studied morphologically, and electrophysiologically, 4 months after grafting. Regenerating axons accompanied by Schwann cells extended through basal lamina tubes of the grafts into the distal host nerves. Reinnervation of the tibialis anterior muscles by motor nerves was confirmed by recovery of the compound muscle action potentials (CMAP) and the reinnervation of the muscle spindles was demonstrated by electron microscopy. These findings indicated that the basal lamina tubes of denatured muscles were effective scaffolds through which the regenerating nerve fibers grew across as large a gap as 5 cm.

Method for morphometric analysis of axons in experimental peripheral nerve reconstruction

A new method for morphometric analysis of axons in experimental peripheral nerve reconstruction is presented. Twelve adult female rabbits were used. In nine animals the saphenous nerve was transected and stitched epineurially. Three animals functioned as control. After 3, 6, and 12 months, the nerves were harvested, fixed in Kryofix and embedded in Histowax. Transverse sections of 6 microm were cut, immunohistochemically stained for NF 90, and counterstained by Sirius Red. Quantification of nerve fibers in cross sections was performed by using a confocal laser scanning microscope (CLSM), and the images were stored digitally. Data analyzing was performed by the Optimas program (5.2). Calculations were done with Microsoft Excel. The total number of axons, the mean axon diameter and the percentage axon area/fascicle area were evaluated statistically. This method for morphologic analysis provides automatically complete registration of axons and so different methods of experimental nerve reconstruction can be compared in a fast and reliable way.

Grafting of detergent-denatured skeletal muscles provides effective conduits for extension of regenerating axons in the rat sciatic nerve

The basal laminae of muscle fibers, when treated by denaturing methods including freeze thawing, have been used as conduits for regenerating nerves. In this study, we developed a new method for denaturing skeletal muscle fibers through treatment with a biological detergent, sodium dodecyl sulfate. Laminin and type IV collagen proteins of muscle fiber basal laminae were preserved after the detergent treatment. A segment of detergent-denatured muscle was grafted to a 1-cm defect of the rat sciatic nerve. One week after grafting, regenerating axons immunostained for neurofilaments were seen extending within laminin-positive muscle fiber basal lamina tubes. Four weeks after grafting, numerous myelinated axons at a much higher level than the control unoperated sciatic nerve, were found in the middle of the graft. They were smaller in diameter than those in the control nerve. Distal host nerves were well reinnervated 4 weeks after grafting. These findings suggest that the basal laminae of detergent-denatured muscle fibers provide effective conduits for regenerating axons.

A 25-year perspective of peripheral nerve surgery: evolving neuroscientific concepts and clinical significance

In spite of an enormous amount of new experimental laboratory data based on evolving neuroscientific concepts during the last 25 years peripheral nerve injuries still belong to the most challenging and difficult surgical reconstructive problems. Our understanding of biological mechanisms regulating posttraumatic nerve regeneration has increased substantially with respect to the role of neurotrophic and neurite-outgrowth promoting substances, but new molecular biological knowledge has so far gained very limited clinical applications. Techniques for clinical approximation of severed nerve ends have reached an optimal technical refinement and new concepts are needed to further increase the results from nerve repair. For bridging gaps in nerve continuity little has changed during the last 25 years. However, evolving principles for immunosuppression may open new perspectives regarding the use of nerve allografts, and various types of tissue engineering combined by bioartificial conduits may also be important. Posttraumatic functional reorganizations occurring in brain cortex are key phenomena explaining much of the inferior functional outcome following nerve repair, and increased knowledge regarding factors involved in brain plasticity may help to further improve the results. Implantation of microchips in the nervous system may provide a new interface between biology and technology and developing gene technology may introduce new possibilities in the manipulation of nerve degeneration and regeneration.

The effect of denervated muscle and Schwann cells on axon collateral sprouting

The effects of denervated muscle and Schwann cells on collateral sprouting from peripheral nerve were studied in the peroneal and tibial nerves of 48 Sprague-Dawley rats. Three groups were prepared. In group MSW (muscle-Schwann cell-window), the peroneal nerves were transected 3 mm below the sciatic bifurcation. The proximal stumps were sealed in a blocked tube to prevent regeneration and the distal stumps were implanted into denervated muscle cells that were wrapped around the ipsilateral tibial nerve, which had a window of perineurium resected. Schwann cells from the ipsilateral sural nerve were implanted into the muscle. Group MS (muscle-Schwann cell) was similar to group MSW, except that the tibial nerve perineurium was kept intact. In group MW (muscle-window), the muscle was prepared without Schwann cells and the tibial nerve perineurium was windowed. S-100 immunostain was used to identify the Schwann cells surviving 1 week after transplantation. After 16 weeks of regeneration, horseradish peroxidase tracer was used to label motor neurons and sensory neurons reinnervating the peroneal nerve. Myelinated axons of the reinnervated peroneal nerves were quantified with the Bioquant OS/2 computer system (R&M Biometrics, Nashville, TN). A mean of 169 motor neurons in group MSW, 64 in group MW, and 26 in group MS reinnervated the peroneal nerve. In the dorsal root ganglion, the mean number of labeled sensory neurons was 1,283 in group MSW, 947 in group MS, and 615 in group MW. The mean number of myelinated axons in the reinnervated peroneal nerve was 1,659 in group MSW, 359 in group MS, and 348 in group MW. Reinnervated anterolateral compartment muscles in group MSW were significantly heavier than those in group MS or MW. This study demonstrates that the transplantation of denervated muscle and Schwann cells promotes motor and sensory nerve collateral sprouting through a perineurial window.

Axonal regeneration through muscle autografts submitted to local anaesthetic pretreatment

Freeze-thawed muscle grafts (FTMG) have been used as an alternative to nerve grafts for the reconstruction of peripheral nerve defects, although their use has some disadvantages. For instance, FTMG may fragment easily after freeze-thawing, a fact impairing their use for surgery. In this study we describe a method to obtain muscle autografts based on the myotoxic properties of local anaesthetics. Fifteen adult rats had their left tibialis anterior muscles injected transcutaneously with 0.3 ml of 2% lidocaine hydrochloride. Twenty-four hours later the injected muscle was removed and a lidocaine muscle graft (LMG) was obtained by trimming the muscle to a rectangular block of approximately 1.0 cm in length. The left sciatic nerve was exposed in the mid-thigh region and a segment removed so that a final 1.0 cm-long gap was produced. The LMG was coaxially autografted to the epineurium between the proximal and distal nerve stumps. In another 15 rats, the sciatic nerve gap was repaired with FTMG obtained from the tibialis anterior muscle. Surgical procedures were similar in both groups. Axonal regeneration and muscle reinnervation were studied quantitatively and ultrastructurally 60 days after the insertion of LMG and FTMG. The results showed that axonal regeneration with the LMG was qualitatively similar to that observed with the FTMG, with no significant differences between groups. We conclude that LMG was a successful muscle graft and a suitable alternative to other denaturing methods, without the disadvantages of FTMG.

Axonal regeneration through acellular muscle grafts

The management of peripheral nerve injury remains a major clinical problem. Progress in this field will almost certainly depend upon manipulating the pathophysiological processes which are triggered by traumatic injuries. One of the most important determinants of functional outcome after the reconstruction of a transected peripheral nerve is the length of the gap between proximal and distal nerve stumps. Long defects (> 2 cm) must be bridged by a suitable conduit in order to support axonal regrowth. This review examines the cellular and acellular elements which facilitate axonal regrowth and the use of acellular muscle grafts in the repair of injuries in the peripheral nervous system.

Nerve growth factor enhances nerve regeneration through fibronectin grafts

Soluble fibronectin and nerve growth factor (NGF) promote axonal regeneration when placed in silicone tubes. We investigated the ability of orientated fibronectin mats to bind and release bioactive NGF and the possibility of augmenting axonal regeneration following axotomy by using fibronectin conduits impregnated with NGF. The release of NGF was quantified using a fluorometric ELISA and bioactivity confirmed with a neuronal culture bioassay. Immunohistochemical techniques and computerized image analysis were used to assess the rate and volume of axonal and Schwann cell regeneration. The delivery of NGF to the site of injury produced an increase in the rate (P < or = 0.007) and volume (P < or = 0.004) of both axonal and Schwann cell regeneration when compared to conduits of plain fibronectin. We conclude that the local delivery of NGF by impregnated fibronectin conduits enhances axonal regeneration.

Orientated mats of fibronectin as a conduit material for use in peripheral nerve repair

This study introduces a new nerve conduit material consisting of orientated strands of the cell adhesive fibronectin. Axonal regeneration, Schwann cell behaviour and the degree of inflammation were quantified using immunohistochemical techniques and computerized image analysis. The results when fibronectin was used to bridge a 1 cm defect in rat sciatic nerve were compared to those with autologous nerve grafts and freeze-thawed muscle grafts used as controls. The nerve grafts supported the highest rate and amount of axonal regeneration in the first 10 days; however, the fibronectin supported a significantly faster rate of growth (P = 0.0008) and amount (P = 0.0001) of axons than the freeze-thawed muscle grafts. From day 15 onwards, the fibronectin and nerve grafts had comparable amounts of regenerating axons and Schwann cells. We conclude that the orientated form of fibronectin is a suitable material for successful nerve repair and has potential clinical use.