The long-term functional recovery of repair of sciatic nerve transection with biogenic conduits

PMMA-induced biofilm promotes Schwann cells migration and proliferation mediated by EGF/Tnc/FN1 to improve sciatic nerve defect

Objective

The purpose of this study is to investigate the role of PMMA-induced biofilm in nerve regeneration compared with silicone-induced biofilm involved in the mechanism.

Methods

PMMA or silicon rods were placed next to the sciatic nerve to induce a biological membrane which was assayed by PCR, Western blot, immunohistochemistry, immunofluorescence and proteomics. A 10 mm sciatic nerve gaps were repaired with the autologous nerve wrapped in an induced biological membrane. The repair effects were observed through general observation, functional evaluation of nerve regeneration, ultrasound examination, neural electrophysiology, the wet weight ratio of bilateral pretibial muscle and histological evaluation. Cell proliferation and migration of Schwann cells co-cultured with EGF-treated fibroblasts combined with siRNA were investigated.

Results

The results indicated that expression of GDNF, NGF and VEGF along with neovascularization was similar in the silicone and PMMA group and as the highest at 6 weeks after operation. Nerve injury repair mediated by toluidine blue and S100β/NF200 expression, the sensory and motor function evaluation, ultrasound, target organ muscle wet-weight ratio, percentage of collagen fiber, electromyography and histochemical staining were not different between the two groups and better than blank group. EGF-treated fibroblasts promoted proliferation and migration may be Tnc expression dependently.

Conclusion

Our study suggested that PMMA similar to silicon induced biofilm may promote autogenous nerve transplantation to repair nerve defects through EGF/Tnc/FN1 to increase Schwann cells proliferation and migration.

The efficacy of combining a vascularized biogenic conduit and a decellularized nerve graft in the treatment of peripheral nerve defects: An experimental study using the rat sciatic nerve defect model

BACKGROUND

Although decellularized nerve grafts are often used as a bridging material in nerve defect repair, the lack of perfusion support in this procedure limits the regeneration capacity. To address this, we applied vascularized biogenic conduits, which are fibrous membranes prefabricated around the silicone rod that contain rich vascularity and macrophages, to nerve defect repair procedures using decellularized nerve grafts. The purpose of this study is to investigate the capacity of combining a vascularized biogenic conduit and a decellularized nerve graft for peripheral nerve regeneration using a 10-mm nerve defect model in rats.

MATERIALS AND METHODS

Sixteen adult male rats (F344 rats, 10-12 weeks, 200-250 g) were used in this study. For the prefabrication of vascularized biogenic conduits, a silicone rod was transplanted next to the sciatic nerve. After 8 weeks, this silicone rod was enveloped in connective tissue, called a vascularized biogenic conduit. The first rat was used to investigate the histological characteristics of vascularized biogenic conduits through immunofluorescence studies. The remaining 15 rats were divided into three groups to evaluate the efficacy of the combination of a decellularized nerve graft and a vascularized biogenic conduit: a decellularized nerve graft (DNG) group, a decellularized nerve graft with a vascularized biogenic conduit (DNG-w-VBC) group, and an autologous nerve graft (ANG) group. Eight weeks after nerve graft surgery, the assessment results of both functional recovery (electrophysical studies and target muscle atrophy) and morphological recovery (total number, diameter, and myelin thickness of the regenerated axons) of the regenerated nerves were examined.

RESULTS

Immunofluorescence studies revealed that the VBC contains extracellular matrix, vascular tissue, and macrophages. The results of the DNG-w-VBC group were superior to the DNG group in electrophysiological studies (CMAP; 6.29 ± 0.80% vs. 4.02 ± 3.35%, MNCV; 50.6 ± 8.4% vs. 25.7 ± 15.6%, p < .05, respectively), regenerated axon number (11,348 ± 812 vs. 7697 ± 2197, p < .05), and mean axon diameter (2.72 ± 0.33 μm vs. 1.64 ± 0.12 μm, p < .05).

CONCLUSIONS

Our study confirms that vascularized biogenic conduits supply vascularity and macrophages to nerve defect sites. Combining vascularized biogenic conduits with decellularized nerve grafts to treat nerve defects offers superior functional and morphological recovery of regenerated axons.

Evidence-Based Approach to Nerve Gap Repair in the Upper Extremity: A Review of the Literature and Current Algorithm for Surgical Management

The upper extremity is the most common site for nerve injuries. In most cases, direct repair can be performed, but when a critical gap occurs, special techniques must be used to enhance nerve regeneration and allow recovery of sensory and motor functions. These techniques include the use of autografts, processed nerve allografts, and conduits. However, surprisingly few studies have compared outcomes from the different methods of nerve gap repair in a rigorous fashion. There is a lack of evidence-based guidelines for the management of digital and motor and mixed nerve injuries with a nerve gap. The purpose of this study is to perform a comprehensive literature review and propose a rational algorithm for management of nerve injuries with a critical gap.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

INTERPRETATION

Using complementary approaches.

Progress in the Research and Development of Nerve Conduits

The reconstruction after peripheral nerve damage, especially for long-segment nerve defects, remains a clinical challenge. Autologous nerve graft transplantation is an efficient method for the repair of peripheral nerve defects, but the involved complications and shortcomings have greatly limited the clinical efficacy of treatments offered to patients with nerve defects. Thus, there is an urgent need to develop new therapeutic strategies and explore alternatives to autologous nerve transplantation in clinical practice, based on the knowledge of the peripheral nerve regeneration mechanism and biological histocompatibility principles. With significant advances in the research and application of nerve conduits, they have been used to repair peripheral nerve injury for several decades. In this paper, the study background of nerve conduits, their applications in clinic, status of conduit material research and construction of tissue-engineered artificial nerves were reviewed.

Comparison of results obtained with standard and inside out vein graft techniques and their implication on neurotrophin expression in repair of nerve defect: an experimental study

Standard vein graft (SVG) and inside out vein graft (IOVG) techniques to promote peripheral nerve regeneration have been widely studied since last two decades. In this experimental study, we attempted to compare these two techniques and analyze the differences in the expression of the neurotrophins during peripheral nerve regeneration. Thirty-six male Wistar rats were used in this sciatic nerve transection model and were divided into two experimental groups (SVG and IOVG) and one sham operated control group. An overall defect of 10 mm was made in the sciatic nerve of the animals in the experimental groups. Each group consisted of two time intervals of 6 and 12 weeks (n = 6). After each experimental interval, sciatic functional index (SFI) along with area and diameter of the axons and fibers of each group were calculated. Muscle mass measurements were also evaluated to see any functional recovery in the groups. Expression of neurotrophins in the graft and distal stump were analyzed with the help of RT-PCR. SFI obtained from walking track analysis showed poor motor recovery in the experimental groups during both time intervals. No significant differences in the histological, morphometric (P > 0.05), and muscle mass measurements (P > 0.05) between the two experimental groups were observed. Analysis of RT-PCR data exhibited an increase in the expression of NT-3 with time in both the grafts (6 weeks 0.428 ± 0.392, 12 weeks 1.089 ± 0.455, P < 0.05) and distal stump (6 weeks 0.411 ± 0.306, 12 weeks 0.807 ± 0.303, P < 0.05) of the SVG group. The study concludes that there is no substantial difference in the nerve regeneration ability between both the techniques. Also, the difference in the level of NT-3 between SVG and IOVG suggests a distinct regulation of NT-3 in peripheral nerve regeneration.

C3 toxin and poly-DL-lactide-ε-caprolactone conduits in the critically damaged peripheral nervous system: a combined therapeutic approach

INTRODUCTION

Peripheral nerve regeneration over longer distances through conduits is limited. In the presented study, critical size nerve gap bridging with a poly-DL-lactide-ε-caprolactone (PLC) conduit was combined with application of C3 toxin to facilitate axonal sprouting.

MATERIALS AND METHODS

The PLC filled with fibrin (n = 10) and fibrin gel loaded with 1-μg C3-C2I and 2-μg C2II (n = 10) were compared to autologous nerve grafts (n = 10) in a 15-mm sciatic nerve gap lesion model of the rat. Functional and electrophysiological analyses were performed before histological evaluation.

RESULTS

Evaluation of motor function and nerve conduction velocity at 16 weeks revealed no differences between the groups. All histological parameters and muscle weight were significantly elevated in nerve graft group. No differences were observed in both PLC groups.

CONCLUSIONS

The PLCs are permissive for nerve regeneration over a 15-mm defect in rats. Intraluminal application of C3 toxin did not lead to significant enhancement of nerve sprouting.

The development of a normalization method for comparing nerve regeneration effectiveness among different graft types

The inability to compare directly different nerve grafts has been a significant factor hindering the advance of nerve graft development. Due to the abundance of variables that exist in nerve graft construction and multiple assessment types, there has been limited success in comparing nerve graft effectiveness among experiments. Using mathematical techniques on nerve conduction velocity (NCV) autograft data, a normalization function was empirically derived that normalizes differences in gap lengths. Further analysis allowed for the development of the relative regeneration ratio (RRR). The RRR function allows researchers to directly compare nerve graft results based on the NCV data from their respective studies as long as the data was collected at the same post-operation time. This function also allows for comparisons between grafts tested at different gap lengths. Initial testing of this RRR function provided confidence that the function is accurate for a continuum of gap lengths and different nerve graft types.

Evaluation of sensory recovery after reconstruction of digital nerves of the hand using muscle-in-vein conduits in comparison to nerve suture or nerve autografting

BACKGROUND

Muscle-in-vein conduits are a good alternative solution to nerve autografts for bridging peripheral nerve defects since enough graft material is available and no loss of sensation at the harvesting area is expected. The purpose of this study was to compare regeneration results after digital nerve reconstruction with muscle-in-vein conduits, nerve autografts, or direct suture.

PATIENTS AND METHODS

46 patients with 53 digital nerve injuries of the hand subjected to direct suture (n = 22) or reconstruction of 1-6 cm long defects with either nerve autografts (n = 14) or muscle-in-vein conduits (n = 17) between 2008 and 2012, were examined using the two-point discrimination and Semmes-Weinstein Monofilaments.

RESULTS

The follow-up examinations took place 12 to 58 months after surgery. A median reduction of sensibility of 2 Semmes-Weinstein monofilaments compared with intact digits was observed after direct suture (DS) and of 2.5 and 2 Semmes-Weinstein monofilaments after reconstruction with autologous nerve grafts (ANG) and muscle-in-vein conduits (MVC), respectively. No statistically significant differences between all three groups could be found with a significance level set by a P < 0.006 (PDS-ANG = 0.24, PDS-MVC = 0.03, PANG-MVC = 0.52). After harvesting a nerve graft, reduction of sensibility at the donor site occurred in 10 of 14 cases but only in one case after harvesting a muscle-in-vein conduit.

CONCLUSIONS

Muscle-in-vein conduits may be a good alternative solution to autografts for the reconstruction of digital nerves, since no significant differences could be demonstrated between the two methods.

"Strategic sequences" in adipose-derived stem cell nerve regeneration

BACKGROUND

Peripheral nerve injuries (PNI) are a major source of morbidity worldwide. The development of cellular regenerative therapies has the potential to improve outcomes of nerve injuries. However, an ideal therapy has yet to be found. The purpose of this study is to examine the current literature key points of regenerative techniques using human adipose-derived stem cells (hADSCs) for nerve regeneration and derive a comprehensive approach to hADSC therapy for PNI.

METHODS

A literature review was conducted using the electronic database PubMed to search for current experimental approaches to repairing PNI using hADSCs. Key search elements focused on specific components of nerve regeneration paradigms, including (1) support cells, (2) scaffolds, and (3) nerve conduits.

RESULTS

Strategic sequences were developed by optimizing the components of different experimental regenerative therapies. These sequences focus on priming hADSCs within a specialized growth medium, a hydrogel matrix base, and a collagen nerve conduit to achieve neuromodulatory nerve regeneration. hADSCs may exert their neuroregenerative influence through paracrine effects on surrounding Schwann cells in addition to physical interactions with injured tissue.

CONCLUSIONS

hADSCs may play a key role in nerve regeneration by acting primarily as support for local neurotrophic mediation and modulation of nerve growth rather than that of a primary neuronal differentiation agent.

Expression patterns and functional evaluation of the UNC5b receptor during the early phase of peripheral nerve regeneration using the mouse median nerve model

INTRODUCTION

In this study, we evaluated the role of the Netrin-1 receptor UNC5b (Uncoordinated), a neuronal guidance molecule, during peripheral nerve regeneration using the mouse median nerve model.

MATERIALS AND METHODS

Using Western blot analysis, we examined the expression changes of UNC5b after transection and microsurgical repair of the mouse median nerve distal to the transection site. We evaluated the histomorphometrical changes and functional recovery of the grasping force after median nerve transection and repair in wild-type (WT) mice and UNC5b(+/-) heterozygous mice.

RESULTS

In Western blot analysis, we could show a high increase of UNC5b in the nerve segment distal to the injury site at day 14. Histomorphometrical analysis did not show any significant differences between WT animals and heterozygous animals. Using the functional grasping test, we could demonstrate that peripheral nerve regeneration is significantly diminished in heterozygous UNC5b(+/-) mice.

CONCLUSION

By using the mouse median nerve model in transgenic animals, we demonstrate that the Netrin-1 receptor UNC5b plays an important role during peripheral nerve regeneration.