Turnover epineural sheath tube in primary repair of peripheral nerves

Assessment of Human Epineural Conduit of Different Size Diameters on Efficacy of Nerve Regeneration and Functional Outcomes

Background Different types of nerve conduits are used to bridge peripheral nerve gaps when a tension-free repair is unattainable. To best support nerve regeneration, naturally occurring conduits have been tested. Since allografts offer an unlimited source of epineurium, we have developed human epineural conduit (hEC) as a novel technology to bridge nerve gaps. Considering acellular properties, and lack of immunogenic response, epineurium-derived conduits represent an attractive material, when compared with nerve allografts that require systemic immunosuppression. In this study, we introduce the hEC as a novel naturally occurring material applied for repair of nerve gaps after trauma.

Methods We tested the application of hEC created from human sciatic nerve in the restoration of 20 mm sciatic nerve defects in the nude rat model. Four experimental groups were studied: group 1: no repair control (n = 6), group 2: autograft control (n = 6), group 3: matched diameter hEC (n = 6), and group 4: large diameter hEC (n = 6). Functional tests of toe-spread and pin prick were performed at 1, 3, 6, 9, 12 weeks after repair. At 12 weeks, nerve samples were collected for immunostaining of Laminin B, S-100, glial fibrillary acidic protein (GFAP), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), von Willebrand factor, and histomorphometric analysis of myelin thickness, axonal density, fiber diameter, and percentage of the myelinated nerve fibers. Muscle samples were gathered for gastrocnemius muscle index (GMI) and muscle fiber area ratio measurements.

Results Best functional recovery, as well as GMI, was revealed for the autograft group, and was comparable to the matched hEC group. Significant differences were revealed between matched and large hEC groups in expression of S100 (p = 0.0423), NGF (p = 0.269), VEGF (p = 0.0003) as well as in percentage of myelinated fibers (p < 0.001) and axonal density (p = 0.0003).

Conclusion We established the feasibility of hEC creation. The innovative method introduces an alternative technique to autograft repair of nerve defects.

The effect of a gap concept on peripheral nerve recovery in modified epineurial neurorrhaphy: An experimental study in rats

BACKGROUND

Several factors such as surgical approach that only consider topographic anatomy; inadequate fascicular alignment, extraepineurial sprouting in the repair zone; contact of axons with the suture area are the disadvantages of epineurial neurorrhaphy. Accordingly, axonal mismatch, neuroma, and unfavorable nerve recovery become inevitable. Neurotropism is the theory clarifying appropriate matching of the nerve fibers independently without needing surgical approach. The studies comparing the primary nerve repair with the nerve defects bridged in different ways demonstrated better outcomes of nerve recovery in the groups with a nerve gap. In this study, we aimed to demonstrate the effects of the gap concept in primary nerve repair bridged by own epineurium. We hypothesized that this technique will provide better results in terms of peripheral nerve recovery and will significantly eliminate the occurrence of a neuroma, which is quite possible in epineurial neurorrhaphy.

MATERIALS AND METHODS

A total of 35 Wistar female rats weighing 200 ~ 250 g were randomly divided into five groups each with seven rats. Sham controls constituted Group 1, while the rats with epineural neurorrhaphy were included in Group 2. The remaining three groups were the study groups. In Group 3, after the sciatic nerve transection, epineurium of the distal segment was sleeved and preserved. A 2-mm axonal segment was removed from the epineurium free distal ending and no any procedure was applied to the proximal ending of the transected sciatic nerve. Epineuriums of the both sides were approximated and repaired. In Group 4, a 2-mm axonal segment was removed from the proximal ending of the sciatic nerve after preservation of epineurium and no any procedure was applied to the distal part of sciatic nerve. Epineuriums of the both sides were approximated and repaired. In addition, in Group 5, after epineuriums were sleeved in the both distal and proximal stumps, a 1-mm nerve segment was removed from both endings and epineuriums were repaired in the middle bridging a 2-mm axonal gap again. After a 3 months follow-up period Sciatic Functional Index (SFI) was measured by walking track analysis; the area under the evoked compound muscle action potential (CMAP) and latency periods were calculated via electromyographic (EMG) analysis; and histopathological evaluation were performed to compare the parameters of edema, fibrosis, inflammation, vascularization, axonal degeneration, axonal density, myelination, disorganization, and neuroma occurrence. Vascular structures and nerve fibers were counted at ×200 magnification: +1, +2, and +3 indicated the presence of 0-15, 16-30, and >30 structures, respectively. For uncountable parameters (edema, disorganization, myelination, fibrosis, and inflammation): +1 indicated mild, +2 indicated moderate, and +3 indicated severe.

RESULTS

The differences between the groups with axonal gap repair and epineural neurorrhaphy were not significant regarding to SFI. The areas under CMAP were as follows: 27.9 ± 5.9 (Δ = 12.1%) in Group 1; 16.5 ± 5.5 (Δ = 6.3%) in Group 2; 14.1 ± 6.2 (Δ = 4.8%) in group 3; 13.8 ± 2.3 (Δ = 9.2%) in Group 4, and 22.5 ± 18.3 (Δ = 2.2%) in Group 5. Group 5 (1 mm gap in the distal +1 mm gap in the proximal segments) had a significantly better result in terms of the area under CMAP with the value of 22.5 ± 18.3 m/Mv (p = .031). Axonal density was 0.9 ± 0.6 (Δ = 2.2%) in Group 2, 2.4 ± 0.3 (Δ = 5.1%) in Group 3, 2.8 ± 0.1 (Δ = 7.7%) in Group 4, and 2.8 ± 0.2 (Δ = 4.8%) in Group 5. Myelination was 1.1 ± 0.5 (Δ = 3.4%) in group 2, 2.2 ± 0.2 (Δ = 6.7%) in group 3, 2.4 ± 0.4 (Δ = 6.0%) in Group 4, and 2.7 ± 0.3 (Δ = 4.6%) in Group 5. Disorganization was 2.3 ± 0.4 (Δ = 4.1%) in Group 2, 1.2 ± 0.2 (Δ = 7.7%) in Group 3, 1.3 ± 0.2 (Δ = 6.5%) in Group 4, and 1 ± 0.3 (Δ = 5.9%) in Group 5. And, neuroma occurrence was found 2.2 ± 0.6 (Δ = 2.8%) in Group 2 and 0.3 ± 0.2 (Δ = 0.1%) in Group 4 while neuroma was not encountered in Group 3 and Group 5. Comparison between the epineurial neurorrhaphy group and the groups with axonal defect revealed the statistically significant results in the factors of axonal density (p = .001), myelination (p = .028), disorganization (p = .016) and neuroma (p = .001).

CONCLUSIONS

Creating axonal gap bridged by own epineurium showed favorable results comparing with epineurial neurorrhaphy. Resection of a 1 mm axonal segment from the proximal and distal stumps following the epineurial sleeve procedure and performing the epineurium- only repair can facilitate the nerve regeneration. The feasibility of the described technique has been demonstrated in a small rat model and must be further validated in larger animals before clinical testing.

Comparison of the Effects of Intratubal Injection of Adipose-Derived Mesenchymal Stem Cells in a Rat Sciatic Nerve Transection: An Experimental Study

ABSTRACT

This study was designed to evaluate the efficacy of epineural tubulization (ENT) with or without intratubal application of adipose-derived mesenchymal stem cells (ASCs) in the rat model of sciatic nerve transection. After formation of 1-cm defect in the left sciatic nerve and ENT, 32 adults female Wistar albino rats were separated into 4 groups (n = 8 for each) including ENT per se (group 1; ENT group) and ENT plus intratubal ASC injection groups killed on day 21 (group 2; ENT-ASC-21-day group), 60 days (group 3; ENT-ASC-60-day group), and 120 days (group 4; ENT-ASC-120-day group). Functional (sciatic function index, hip circumference, withdrawal reflex latency, muscle weight ratio), electrophysiological, histomorphometric, and immunohistochemical analyses were performed in each group. Sciatic function index was significantly higher (-51.98 ± 5.94, P < 0.01) and withdrawal reflex latency was shorter (-6.21 ± 2.14, P < 0.01), in the group 4 as compared with all other groups on day 21. Amplitude of contraction was significantly lower in the group 4 as compared with all other groups (0.22 ± 0.05 vs 0.34 ± 0.07, 0.50 ± 0.11, and 0.61 ± 0.16, P < 0.01 for each). Immunohistochemical analysis revealed presence of green fluorescent protein, vimentin-stained cells, and single neural progenitor cells indicating that induction of neuronal differentiation by ASCs and direct involvement of ASCs within the axonal structure alongside extension of ASCs to the muscular layer of the group 4. In conclusion, our findings revealed that use of ENT plus intratubal ASC injection in a rat sciatic nerve transection model was associated with satisfactory functional outcome and improved peripheral axonal regeneration along with stem cell neural differentiation.

Epineurial Nerve Coaptation: A Biological Nonliving Training Model Using Gradually Thawed Cryopreserved Sciatic Nerves

The authors present a novel biological nonliving epineurial nerve coaptation training model, which allows cost-efficient practicing on organic mammal nerves and offers an objective performance control on the basis of successful suturing and respecting the 3R model.Anatomic dissection of 40 rat cadavers was performed. Four residents without prior microneurosurgical experience were included. Each trainee performed 20 epineurial nerve coaptations. The number of successful sutures served as qualitative variable and operation time as a quantitative variable for efficiency control.The rate for successful sutures was 51.9% in the first half of trials and improved to 94.4% in the second half. Whereas, the trainees needed a mean time of 34 minutes for the first 10 coaptations, the last 10 coaptations were performed within 24.5 minutes.The authors' presented model is an easily accessible, low-cost microneurosurgical simulation model, allowing a realistic and instructive performance of epineurial nerve coaptation. Because cadaveric nerves are used, an approval of the local ethics committee is not needed. Furthermore, anatomic knowledge about the topography related to the harvest of the sciatic nerve of rats is provided in this study.

Application of Epineural Sheath as a Novel Approach for Fat Volume Maintenance

INTRODUCTION

Various methods have been suggested to improve fat graft survival and decrease graft loss. The exact mechanism of fat graft survival is still unclear, and new strategies are needed to further investigate it.

MATERIALS AND METHODS

The efficacy of epineural sheath in fat volume maintenance was tested in rat model. Five experimental groups were created: group 1, fat graft without any coverage; group 2, epineural sheath tube alone; group 3, epineural sheath tube filled with fat graft; group 4, fat graft mixed with minced epineural sheath without any coverage; and group 5, fat graft covered with the epineural sheath patch. All grafts were implanted into the dorsal subcutaneous region and were followed for up to 12 weeks, when samples were harvested for hematoxylin and eosin and immunostaining for vascular endothelial growth factor expression and perilipin evaluation of fat viability.

RESULTS

In groups 1 and 4, over 25% of graft loss was observed at first week, over 50% at third week, and 100% at sixth week postimplantation. The weight of fat graft within the epineural sheath tube and the weight of epineural tube (ET) alone were maintained up to 12 weeks postimplantation. The weight of fat graft within the epineural patch was maintained up to 6 weeks, but 50% of weight loss was observed between 6 and 12 weeks. Structure of the epineural sheath tubes and patches was intact, and no leakage of fat graft was observed. Based on hematoxylin and eosin staining, normal structure and integrity of the fat graft within the ET were preserved up to 12 weeks postimplantation. Characteristic adipocyte morphology was confirmed by perilipin staining, showing viable fat cells in groups 3 and 5 at 12 weeks. Increased vascular endothelial growth factor expression was observed in groups 2, 3, 4, and 5.

CONCLUSIONS

Both, the ETs and epineural patches maintained 100% and 50% of fat graft weight at 12 weeks postimplantation, respectively. These results were confirmed by histology and immunostaining showing viable adipocytes within the epineural patches (6 weeks) and tubes (12 weeks). These results are encouraging and justify further evaluation of fat volume maintenance in preclinical large animal model in preparation to clinical application.

Distal Inside-Out Epineural Sliding Technique to Repair Segmental Nerve Defects

Background: The repair of a segmental peripheral nerve injury is a clinical challenge. Several studies have been performed to determine superior methods for overcoming nerve gaps. The purpose of this study was to investigate if the inside-out slided epineurium of the distal segment of an injured nerve can serve as a conduit to bridge a short nerve defect (10 mm). Methods: Nineteen sciatic nerves in Sprague-Dawley rats were transected, and a 10-mm gap was left between the ends. A section of distal epineurium was pulled inside out to bridge the gap. Walking track analysis was performed, and the sciatic function index (SFI) was calculated. Wet muscle mass and withdrawal reflex were measured. The density of axon fibers at different levels of repaired nerves was determined, and histological analysis was performed at 16 weeks. Results: The mean SFI improved from -81.0 at 4 weeks to 36.3 at 16 weeks. The axon densities showed regeneration through the epineural tube, and 5 of the rats demonstrated a withdrawal reflex. The weight of the tibialis anterior muscle of the injured limb at 16 weeks was 59% that of the uninjured side. Conclusions: The distal epineural sheath tube provided a size-matched conduit between the nerve stumps, with no histological donor-site morbidity. Histologically, regeneration occurred through the epineural tube without neuroma formation, and functional recovery was comparable to that of previous studies of nerve repair techniques. Technique may be an addition to the armamentarium of tools used to treat segmental nerve defects.

Evaluating the effect of polytetrafluoroethylene and extractum cepae-heparin-allantoin gel in peripheral nerve injuries in a rat model

BACKGROUND

Peripheral nerves can be injured by congenital, mechanical, thermal or chemical causes. Peripheral nerve injuries are increasing in frequency, particularly in countries that are becoming more industrialized. Nerve and extremity injuries result in work loss and high treatment costs, and can lead to separation of patients from their social environment. Failure of nerve repair causes muscle functional losses, sensory losses and painful neuropathies.

OBJECTIVES

To compare the effects of condensed polytetrafluoroethylene (cPTFE) and cPTFE-extractum cepae-heparin-allantoin (cPTFE-EHA) gel compound on nerve and functional recovery, and the prevention of adhesion and scar tissue formation after total peripheral nerve injury repaired by primary suture in a rat model.

RESULTS

cPTFE alone and cPTFE-EHA gel was found to provide better functional recovery and nerve regeneration compared with primary repair only. In the macroscopic evaluation, the cPTFE-EHA gel was found to have no negative effect on wound healing and, despite increasing extra-neural scar tissue and adhesions, it had no negative effect on nerve function; in addition, it facilitated functional recovery.

CONCLUSIONS

Compared with the cPTFE application alone, the application of perineural cPTFE-EHA gel during peripheral nerve surgery appeared to provide better functional recovery without causing any significant changes in epineural and extraneural scar tissue formation.

Evaluating the effect of polytetrafluoroethylene and extractum cepae-heparin-allantoin gel in peripheral nerve injuries in a rat model

Background

Peripheral nerves can be injured by congenital, mechanical, thermal or chemical causes. Peripheral nerve injuries are increasing in frequency, particularly in countries that are becoming more industrialized. Nerve and extremity injuries result in work loss and high treatment costs, and can lead to separation of patients from their social environment. Failure of nerve repair causes muscle functional losses, sensory losses and painful neuropathies.

Objectives

To compare the effects of condensed polytetrafluoroethylene (cPTFE) and cPTFE-extractum cepae-heparin-allantoin (cPTFE-EHA) gel compound on nerve and functional recovery, and the prevention of adhesion and scar tissue formation after total peripheral nerve injury repaired by primary suture in a rat model.

Results

cPTFE alone and cPTFE-EHA gel was found to provide better functional recovery and nerve regeneration compared with primary repair only. In the macroscopic evaluation, the cPTFE-EHA gel was found to have no negative effect on wound healing and, despite increasing extraneural scar tissue and adhesions, it had no negative effect on nerve function; in addition, it facilitated functional recovery.

Conclusions

Compared with the cPTFE application alone, the application of perineural cPTFE-EHA gel during peripheral nerve surgery appeared to provide better functional recovery without causing any significant changes in epineural and extraneural scar tissue formation.

A contemporary overview of peripheral nerve research from the Cleveland Clinic Microsurgery Laboratory

Despite our better understanding of the pathophysiology of peripheral nervous system and advancements in microsurgical repair techniques, peripheral nerve injuries are still considered as a reconstructive challenge for all surgeons. For achieving a better nerve regeneration and better end organ reinnervation, advanced microsurgical manipulations are parallel with molecular biological discoveries. The field of peripheral nerve research is still developing and includes more sophisticated approach at the basic science level. In our Microsurgery Research Laboratory we have been working on different nerve repair techniques, including sleeve neurorrhaphy, sleeve grafts, single and polyfascicular nerve grafting techniques and studies on nerves in diabetic rats, in addition to the roles of different growth factors and pharmacological agents on peripheral nerve regeneration. New approaches for filling nerve gaps with nerve allografts and tolerance inducing strategies with their effect on nerve regeneration are included into our research armamentarium. In this overview we will summarize our 15-year experience in peripheral nerve research.