Reconstruction Of Sciatic Nerve Research Articles

Influence of the Combination of Single Fascicle Grafting and Vascular Epithelial Growth Factor on the Nerve Reconstruction in the Rat Sciatic Nerve Injury Model: Experimental Study

Background and Aim: The purpose of this study was to evaluate the regeneration effects after sciatic nerve reconstruction with single fascicle grafting + vascular endothelial growth factor (VEGF) compared with traditional epineural suture. Methods: Sixty-four Wistar rats were divided into 2 groups randomly and created 10-25 mm sciatic nerve defects. In control group, nerve was reconstructed using traditional epineural suture and the rats of the study group were treated with single fascicle grafting + VEGF. At the point of 6 and 12 weeks, testing consisted of sciatic nerve function index (SFI), gastrocnemius muscle weight, toe spread test, pin-prick test was undergone. Results: The rats of 25mm defect subgroup repaired with single fascicle grafting + VEGF demonstrated significantly higher SFI score, toe spread test score, re- innervated muscle weight at the points of 6, 12 weeks. And in the 20, 25 mm defect rats of study group, pin-prick test score were significantly higher than the control group. Conclusion: Single fascicle grafting + VEGF was better to reconstruct long nerve defect compared to epineural suture.

Nanobioglass enhanced polyurethane/collagen conduit in sciatic nerve regeneration.

The main purpose of neural tissue engineering and regenerative medicine is the development of biological substitutions to preserve, improve, and regenerate the damaged functions of tissues and organs. Three novel conduits, including polyurethane (PU), polyurethane/collagen (PU/C), and polyurethane/collagen/nano-bio glass (PU/C/NBG), were fabricated by the electrospinning technique. After confirming the suitability of conduits in the in-vitro environment, conduits were surgically sutured in a 10-mm gap in the sciatic nerve of a rat to evaluate their role in sciatic nerve reconstruction. After 4, 8, and 12 weeks of surgery, nerve regeneration was assessed by the hot plate test, sciatic functional index, electromyography, histology, and immunohistochemistry against S100, NF200, and CD31 antibodies. The results of various examinations revealed that the PU/C/NBG conduit is significantly more suitable than PU and PU/C conduits in terms of nerve regeneration. However, all three groups of conduits had the potential to be used for nerve regeneration. Overall, this study discovered that the PU/C/NBG conduit is a biocompatible neural conduit, which is a favorable candidate for peripheral nerve regeneration and axonal growth.

The Superficial Inferior Epigastric Artery Fascia Flap in Rats

Abstract Background An adipofascial flap in the rat may provide new options for adding vascularization to scarred or nonvascularized beds for a variety of research studies. Current literature lacks sufficient description for a simple reproducible flap model for a vascularized pedicled flap in rats, in particular for neovascularization of allograft nerves for the reconstruction of sciatic nerve defects. The purpose of this study was to describe a surgical technique and determine long-term survivability for the pedicled superficial inferior epigastric artery fascial (SIEF) flap in the rat to meet requirement for a tunneled adipofascial flap to add vascularization to the sciatic nerve area. Methods The technique and use of a 4 × 3-cm SIEF flap are described. Twenty Lewis rats underwent the technique to determine feasibility. The flap was wrapped around processed allograft nerve reconstructions and viability of the flap was evaluated after 12 and 16 weeks. To visualize vessels, nerve grafts were harvested at 12 weeks and stained with hematoxylin-eosin and an antibody against microvessels (CD-34). Results All flaps remained viable after survival of 12 and 16 weeks. Complications included one hematoma formation and two lymphocele formations that did not have any impact on the flap. Immunohistochemistry confirmed an increase in microvessels and Schwann cell nuclei in the SIEF group compared with nerve samples from the unoperated, contralateral side. Conclusion A pedicled adipofascial flap model in the rat to provide a vascular bed for sciatic nerve reconstruction is detailed with long-term survivability evaluation of the flap. This flap is technically simple to be harvested and is suitable for revascularization procedures of various tissues in the lower abdomen, genital area, thigh, or upper limb of the rat.

Comparable functional motor outcomes after repair of peripheral nerve injury with an elastase-processed allograft in a rat sciatic nerve model.

A bridging nerve autograft is the gold standard for the repair of segmental nerve injury that cannot be repaired directly. However, limited availability and donor site morbidity remain major disadvantages of autografts. Here, a nerve allograft decellularized with elastase was compared with an autograft regarding functional motor outcome in a rat sciatic segmental nerve defect model. Furthermore, the effect of storage on this allograft was studied. Sixty-six Lewis rats (250-300 g) underwent a 10-mm sciatic nerve reconstruction using either a cold- (n = 22) or frozen-stored (n = 22) decellularized nerve allograft or an autograft (n = 22). Sprague-Dawley rats (300-350 g) served as full major histocompatibility complex-mismatched donors. Functional motor outcome was evaluated after 12 and 16 weeks. Ankle angle, compound muscle action potential (CMAP), isometric tetanic force, wet muscle weight, and histomorphometry were tested bilaterally. For CMAP and isometric tetanic force, no significant differences were observed between groups. In contrast, for ankle angle, histomorphometry and muscle weight, the cold-stored allograft performed comparable to the autograft, while the frozen-stored allograft performed significantly inferior to the autograft. At week 16, ankle angle was 88.0 ± 3.1% in the cold-stored group, 77.4 ± 3.6% in the frozen-stored group, and 74.1 ± 3.1% in the autograft group (P < .001); At week 16, the muscle weight showed a recovery up to 71.1 ± 4.8% in the autograft group, 67.0 ± 6.6% in the cold-stored group, and 64.7 ± 3.7% in the frozen-stored group (P < .05). A nerve allograft decellularized with elastase, if stored under the right conditions, results in comparable functional motor outcomes as the gold standard, the autograft.

Allogenic Adipose Derived Stem Cells Transplantation Improved Sciatic Nerve Regeneration in Rats: Autologous Nerve Graft Model.

We examined the effect of transplantation of allogenic adipose-derived stem cells (ADSCs) with properties of mesenchymal stem cells (MSCs) on posttraumatic sciatic nerve regeneration in rats. We suggested an approach to rat sciatic nerve reconstruction using the nerve from the other leg as a graft. The comparison was that of a critical 10 mm nerve defect repaired by means of autologous nerve grafting versus an identical lesion on the contralateral side. In this experimental model, the same animal acts simultaneously as a test model, and control. Regeneration of the left nerve was enhanced by the use of ADSCs, whereas the right nerve healed under natural conditions. Thus the effects of individual differences were excluded and a result closer to clinical practice obtained. We observed significant destructive changes in the sciatic nerve tissue after surgery which resulted in the formation of combined contractures in knee and ankle joints of both limbs and neurotrophic ulcers only on the right limb. The stimulation of regeneration by ADSCs increased the survival of spinal L5 ganglia neurons by 26.4%, improved sciatic nerve vascularization by 35.68% and increased the number of myelin fibers in the distal nerve by 41.87%. Moreover, we have demonstrated that S100, PMP2, and PMP22 gene expression levels are suppressed in response to trauma as compared to intact animals. We have shown that ADSC-based therapy contributes to significant improvement in the regeneration.

Vascularized nerve grafts: an experimental study

Objective: The aim of this study is to define an experimental model in order to promote the functional recovery of the nerves using grafts with vascular support (Vascular Nerve Grafts – VNG). The aim of this study is to define, on an experimental model in normal recipient bed, whether the functional recovery with VNG is superior to that obtained non-vascularized graft (NNG).Methods: Twenty male rabbits, which underwent dissection of sciatic nerve, were later treated by reinnervation through an autograft. In 10 animals the reconstruction of sciatic nerve was realized with VNG; in 10 control animals the reconstruction of sciatic nerve was realized with NNG.Results: The VNG group showed a better axonal organization and a significantly higher number of regenerated axons in the early phases (after 30 days) than the NNG group, whereas the difference in the axonal number at day 90 was less significant; besides, the axon diameter and the myelin thickness were not significantly improved by VNG group.Discussion: Our data suggests that the use of VNG leads to a faster regeneration process and a better functional recovery, although the final results are comparable to those of the NNG. VNG improve the quality of the axonal regeneration (axonal diameter and Schwann cells), although the increase in the axonal number is not significant and does not improve the long-term functional outcome.

Motor Nerve Regeneration Using an Optimized Nerve Allograft in a Rat Model - An In vitro and In vivo Analysis: N/A - Not a clinical study

In previous animal studies commercially available processed nerve allografts have been inferior to autograft nerve for motor recovery. The goal of this study is to create an optimized nerve allograft (in vitro) and subsequently challenge it to the nerve autograft regarding motor nerve regeneration (in vivo). For the in vitro experiment 50 rat nerves were processed. Based on previous research, standard decellularization protocols were used with different modifications and the addition of an highly potent enzymatic step Elastase. Subsequently, the nerve segments were stored at either 4 or -80°C for the duration of two weeks. Both processed and fresh control nerves were analyzed with confocal microscopy using immunohistochemical stainings on the basal lamina (laminin ?-1), Schwann cells (S100 protein) and immunogenicity (major histocompatibility complex class I). Morphology of the ultrastructure and amount of cellular debris was analyzed on cross sections of the nerves stained with toluidine blue and analyzed under electronmicroscopy. The superior method of this in vitro project was used for implementation in vivo to test the motor functional outcome of the nerve allograft in a rat. In the in vivo project, 60 rats sustained an 1 cm sciatic nerve reconstruction with either autograft (I), non-frozen allograft (II), or frozen allograft (III). Twelve and 16 weeks post-operatively motor functional outcome was determined with ankle angle, electrophysiology, isometric tetanic force, muscle mass and histomorphometry. Nerve ultrastructure was preserved with all decellularization protocols. Storage at -80°C severely altered nerve ultrastructure after any decellularization method. Elastase was found to significantly reduce the immunogenicity (MHC-I) and the amount of Schwann cells (S100), while maintaining good structural properties. When tested in vivo, significant differences were found between the three groups with regard to motor function at both 12 and 16 weeks. Cold storage of the processed allograft shows better results than the frozen stored allograft and reached the level of the nerve autograft. •Elastase, when added to nerve processing, reduced immunogenicity, diminished cellular debris and removed Schwann cells better while maintaining ultrastructure.•Storage at -80°C after the decellularization process heavily damaged nerve ultrastructure compared to cold storage.•The in vivo study, the optimized processed nerve allograft showed comparable to the golden standard, the nerve autograft, at both 12 and 16 weeks postoperatively.

Long-term follow-up of peptidergic and nonpeptidergic reinnervation of the epidermis following sciatic nerve reconstruction in rats.

Peripheral nerve injuries are a commonly encountered clinical problem and often result in long-term functional deficits. The current gold standard for transected nerves is an end-to-end reconstruction, which results in the intermittent appearance of neuropathic pain. To improve our understanding of the relation between this type of reconstruction and neuropathic pain, the authors transected and immediately end-to-end reconstructed the sciatic nerve in rats. The effect of this procedure on neuropathic pain, as measured by thermal and mechanical hypersensitivity at 4 different time points (5, 10, 20, and 30 weeks), was related to the density of peptidergic and nonpeptidergic fiber innervation in the glabrous skin of rats' hind paws. Thermal hypersensitivity occurring 20 weeks after reconstruction was accompanied by a significant increase in peptidergic epidermal fibers. However, the lesion-induced reduction in the density of nonpeptidergic epidermal fibers remained decreased at all experimental time points. Moreover, temporal collateral sprouting by undamaged saphenous nerve was visualized using the recently revised Evans blue extravasation technique. Strikingly, as the sciatic nerve repopulated rats' hind paw, the saphenous nerve withdrew to its original territory. The authors conclude that the transient thermal hypersensitivity is related to increased density of epidermal peptidergic fibers, which mainly originate from regenerating fibers. Furthermore, a changed composition in the peptidergic and nonpeptidergic epidermal fibers is demonstrated following end-to-end reconstruction of the sciatic nerve.

Biological conduits combining bone marrow mesenchymal stem cells and extracellular matrix to treat long-segment sciatic nerve defects.

The transplantation of polylactic glycolic acid conduits combining bone marrow mesenchymal stem cells and extracellular matrix gel for the repair of sciatic nerve injury is effective in some respects, but few data comparing the biomechanical factors related to the sciatic nerve are available. In the present study, rabbit models of 10-mm sciatic nerve defects were prepared. The rabbit models were repaired with autologous nerve, a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells, or a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel. After 24 weeks, mechanical testing was performed to determine the stress relaxation and creep parameters. Following sciatic nerve injury, the magnitudes of the stress decrease and strain increase at 7,200 seconds were largest in the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel group, followed by the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells group, and then the autologous nerve group. Hematoxylin-eosin staining demonstrated that compared with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells group and the autologous nerve group, a more complete sciatic nerve regeneration was found, including good myelination, regularly arranged nerve fibers, and a completely degraded and resorbed conduit, in the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel group. These results indicate that bridging 10-mm sciatic nerve defects with a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel construct increases the stress relaxation under a constant strain, reducing anastomotic tension. Large elongations under a constant physiological load can limit the anastomotic opening and shift, which is beneficial for the regeneration and functional reconstruction of sciatic nerve. Better regeneration was found with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel grafts than with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells grafts and the autologous nerve grafts.

Reconstruction of sciatic nerve after traumatic injury in humans - factors influencing outcome as related to neurobiological knowledge from animal research

BackgroundThe aim was to evaluate what can be learned from rat models when treating patients suffering from a sciatic nerve injury.MethodsTwo patients with traumatic sciatic nerve injury are presented with examination of motor and sensory function with a five-year follow-up. Reconstruction of the nerve injury was performed on the second and third day, respectively, after injury using sural nerve grafts taken from the injured leg. The patients were examined during follow-up by electromyography (EMG), MRI and functionalMRI (fMRI) to evaluate nerve reinnervation, cell death in dorsal root ganglia (DRG) and cortical activation; factors that were related to clinical history in the patients.ResultsOne patient regained good motor function of the lower leg and foot, confirmed by EMG showing good activation in the leg muscles and some reinnervation in the foot muscles, as well as some sensory function of the sole of the foot. The other patient regained no motor (confirmed by EMG) or sensory function in the leg or foot. Factors most influential on outcome in two cases were type of injury, nerve gap length and particularly type of reconstruction. A difference in follow-up and rehabilitation likely also influence outcome. MRI did not show any differences in DRG size of injured side compared to the uninjured side. fMRI showed normal activation in the primary somatosensory cortex as a response to cutaneous stimulation of the normal foot. However, none of the two patients showed any activation in the primary somatosensory cortex following cutaneous stimulation of the injured foot.ConclusionsIn decision making of nerve repair and reconstruction data from animal experiments can be translated to clinical practice and to predict outcome in patients, although such data should be interpreted with caution and linked to clinical experience. Rat models may be useful to identify and study factors that influence outcome after peripheral nerve repair and reconstruction; procedures that should be done correctly and with a competent team. However, some factors, such as cognitive capacity and coping, known to influence outcome following nerve repair, are difficult to study in animal models. Future research has to find and develop new paths and techniques to study changes in the central nervous system after nerve injury and develop strategies to utilize brain plasticity during the rehabilitation.

Rat Sciatic Nerve Reconstruction Across a 30 mm Defect Bridged by an Oriented Porous PHBV Tube With Schwann Cell as Artificial Nerve Graft

An oriented poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nerve conduit has been used to evaluate its efficiency based on the promotion of peripheral nerve regeneration in rats. The oriented porous micropatterned artificial nerve conduit was designed onto the micropatterned silicon wafers, and then their surfaces were modified with oxygen plasma to increase cell adhesion. The designed conduits were investigated by cell culture analyses with Schwann cells (SCs). The conduits were implanted into a 30 mm gap in sciatic nerves of rats. Four months after surgery, the regenerated nerves were monitored and evaluated by macroscopic assessments and histology and behavioral analyses. Results of cellular analyses showed suitable properties of designed conduit for nerve regeneration. The results demonstrated that in the polymeric graft with SCs, the rat sciatic nerve trunk had been reconstructed with restoration of nerve continuity and formatted nerve fibers with myelination. Histological results demonstrated the presence of Schwann and glial cells in regenerated nerves. Functional recovery such as walking, swimming, and recovery of nociceptive function was illustrated for all the grafts especially conduits with SCs. This study proves the feasibility of the artificial nerve graft filled with SCs for peripheral nerve regeneration by bridging a longer defect in an animal model.

Schwann cell-seeded scaffold with longitudinally oriented micro-channels for reconstruction of sciatic nerve in rats

To provide a more permissive environment for axonal regeneration, Schwann cells (SCs) were introduced into a collagen-chitosan scaffold with longitudinally oriented micro-channels (L-CCH). The SC-seeded scaffold was then used for reconstruction of a 15-mm-long sciatic nerve defect in rats. The axonal regeneration and functional recovery were examined by a combination of walking track analysis, electrophysiological assessment, Fluoro-Gold retrograde tracing, as well as morphometric analyses to both regenerated axons and target muscles. The findings showed that SCs adhered and migrated into the L-CCH scaffold and displayed a longitudinal arrangement in vitro. Axonal regeneration as well as functional recovery was in the similar range between SCs-seeded scaffold and autograft groups, which were superior to those in L-CCH scaffold alone group. These indicate that the SCs-seeded L-CCH scaffold, which resembles the microstructure as well as the permissive environment of native peripheral nerves, holds great promise in nerve regeneration therapies.

Good reinnervation of motoneurons but poor recovery of gait after delayed as well as immediate sciatic nerve transplant in rats

Surgeons agree that interrupted peripheral nerves should be reconstructed ‘soon’ to enable neural regeneration. Delayed nerve repair will result in impaired outcome, but experimental data on such detriment due to delay are scarce. In a quantitative study we transected the right sciatic nerve of 80 adult female Lewis rats (LEW/SsNHsd), transflected the proximal nerve stump into a muscle pouch and let the animals wait 0 (immediate repair), 3, 6, 9 and 12 months after axotomy, until reconstruction was performed with a 5‐mm long allograft from congenic age‐matched donors. All hosts were studied with two different methods. First, the functional outcome of sciatic nerve reconstruction was evaluated 4–12 weeks after transplant by walking track analysis, calculating de Medinaceli's Sciatic Functional Index (SFI). Second, 12 weeks after transplantation the fibular communal nerve and the soleus branch of the tibial nerve close to its muscle entry were cut and the proximal stumps labelled with the retrograde neuronal tracers DiI or Fast‐Blue. Fourteen days later the rats were perfused with formaldehyde, and the numbers of fluorescently labelled motoneurons were counted in 50 μm serial vibratome sections of the spinal cord. All measurements were done on coded material and codes broken only at the end of the study. Our results are clear‐cut and deeply disappointing. The SFI was around 0 (normal value) in all rats before transection of the sciatic nerve; expectedly dropped to −85 to −125 after denervation, but stayed at −108 to −130 up to 12 weeks after transplantation. No improvement of gait at all occurred after sciatic nerve transplant performed immediately or 3, 6, 9 or 12 months after denervation.This failure of functional recovery is not due to lack of regeneration, as the numbers of labelled motoneurons prove. In normal rats we have labelled 549 ± 83 motoneurons by DiI and Fast‐Blue. After immediate nerve repair we counted 533 ± 95 labelled motoneurons; after repair delayed for 12 months we still counted 474 ± 108 motoneurons that had regenerated. In all rats the labelled motoneurons were randomly interspersed with a complete lack of myotopic distribution. This misdirection of reinnervation sadly prevents recovery of motor function.

An in vivo study of tricalcium phosphate and glutaraldehyde crosslinking gelatin conduits in peripheral nerve repair

In order to modulate the mechanical properties of gelatin, we previously developed a biodegradable composite composed by tricalcium phosphate and glutaraldehyde crosslinking gelatin (GTG) feasible for surgical manipulation. In this study, we evaluated the in vivo applications of GTG conduit for peripheral nerve repair. The effect of sciatic nerve reconstruction was compared between resorbable permeable GTG conduits and durable impermeable silicone tubes. Traditional methods of assessing nerve recovery following peripheral nerve repair including histomorphometric and electrophysiologic features were conducted in our study. In addition, autotomy score and sciatic function index (SFI) in walking tract analysis were used as additional parameters for assessing the return of nerve function. Twenty-four weeks after sciatic nerve repair, the GTG conduits were harvested. Microscopically, regeneration of nerves was observed in the cross-section at the mid portion of all implanted GTG conduits. The cross-sectional area of regenerated nerve of the GTG group was significant larger than that of the silicone group. In the compound muscle action potentials (CMAP), the mean recovery index of CMAP amplitude was 0.24 +/- 0.02 for the silicone group, 0.41 +/- 0.07 for the GTG group. The mean SFI increased with time in the GTG group during the evaluation period until 24 weeks. Walking tract analysis showed a higher SFI score in the GTG group at both 12 and 24 weeks. The difference reached a significant level at 24 weeks. Thus, the histomorphometric, electrophysiologic, and functional assessments demonstrate that GTG can be a candidate for peripheral nerve repair.

Sciatic nerve reconstruction: limb preservation after sarcoma resection.

Limb salvage for extremity sarcoma has become the standard of care when possible. This review attempts to determine the outcome of sciatic nerve reconstruction after surgical tumor resection. The authors' objective was to determine the clinical value of extremity salvage with such a defect. Five patients (two male, three female) were selected from a department database at The University of Texas M.D. Anderson Cancer Center between 1995 and 1999 who met the following criteria: lower limb tumor resection involving a gap in the sciatic nerve with subsequent nerve autograft reconstruction. An additional patient who underwent primary sciatic nerve neurorrhaphy was also included. The average tumor size was 203 cm2. The most common tumor histology was spindle cell sarcoma. The average autograft length was 13 +/- 3.2 cm with one to four cables employed. Currently, 3 patients are still alive. Four of the 5 patients who received sciatic autonerve grafts reported partial distal sensory recovery subjectively. The patient who underwent primary neurorrhaphy has both motor and sensory innervation 42 months after surgery. Although not ideal for all patients, sciatic nerve reconstruction is a viable option for those willing to undergo limb preservation. Notable limitations to daily activity do not appear to be present, and patients are able to ambulate with or without assistive devices. With aggressive rehabilitation, some patients are able to function quite well with this bioprosthesis. Patients should consider, however, that their extremity is on loan. Substantial wound complications or infections may ultimately lead to amputation.

Functional assessment of sciatic nerve reconstruction: Biodegradable poly (DLLA‐ε‐CL) nerve guides versus autologous nerve grafts

Functional assessment of sciatic nerve reconstruction: Biodegradable poly (DLLA‐ε‐CL) nerve guides versus autologous nerve grafts