Comparison of nerve, vessel, and cartilage grafts in promoting peripheral nerve regeneration

Neuroprotective effects ofGarcinia kolaand curcumin on diabetic transected sciatic nerve

The growing interest in peripheral nerve regeneration and developing post-traumatic repair methods under diabetes was the impetus for this study, which aims to investigate the effect of curcumin andGarcinia kola(GK) on the transected and diabetic sciatic nerves. Thirty-five male Wistar albino rats were used. The animals were divided into five groups; each consisted of seven rats. The sciatic nerve was transected in all groups of rats except the control (Cont) group, which underwent no treatment. In the transected animals, a 10 mm nerve stump was removed from the 2 cm distal to the sciatic notch. The external jugular vein was used as a conduit to repair the gap between the two ends of the sciatic nerve. Diabetes was induced in the transected + diabetes mellitus (T + DM), the transected + diabetes mellitus + GK (T + DM + GK), and the transected + diabetes mellitus + Curcumin (T + DM + Cur) groups except for the sham group. A dose of 300 mg kg-1d-1of curcumin dissolved in olive oil was administered to the T + DM + Cur group (via oral gavage every day for 28 d) and 200 mg kg-1d-1of GK to the T + DM + GK group (via oral gavage every day for 7 d). All animals were sacrificed after three months. Stereological analysis and functional and microscopic evaluations were done to evaluate the sciatic nerve regeneration and function. In the T + DM + GK and the sham groups, the number of axons increased. A slight improvement in the axonal area in the T + DM + Cur and the sham groups was also observed, and an increase in the myelin sheath thickness was found in the T + DM + GK and the sham group. When the SFI test results were evaluated, it was seen that GK had a stronger effect than curcumin in terms of functional regeneration. Additionally, no significant difference was observed between T + DM and Cont groups when the electrophysiological results were examined. The study showed GK's efficiency in treating diabetic peripheral nerve regeneration.

Nerve guidance conduit development for primary treatment of peripheral nerve transection injuries: A commercial perspective

Commercial nerve guidance conduits (NGCs) for repair of peripheral nerve discontinuities are of little use in gaps larger than 30 mm, and for smaller gaps they often fail to compete with the autografts that they are designed to replace. While recent research to develop new technologies for use in NGCs has produced many advanced designs with seemingly positive functional outcomes in animal models, these advances have not been translated into viable clinical products. While there have been many detailed reviews of the technologies available for creating NGCs, none of these have focussed on the requirements of the commercialisation process which are vital to ensure the translation of a technology from bench to clinic. Consideration of the factors essential for commercial viability, including regulatory clearance, reimbursement processes, manufacturability and scale up, and quality management early in the design process is vital in giving new technologies the best chance at achieving real-world impact. Here we have attempted to summarise the major components to consider during the development of emerging NGC technologies as a guide for those looking to develop new technology in this domain. We also examine a selection of the latest academic developments from the viewpoint of clinical translation, and discuss areas where we believe further work would be most likely to bring new NGC technologies to the clinic. STATEMENT OF SIGNIFICANCE: NGCs for peripheral nerve repairs represent an adaptable foundation with potential to incorporate modifications to improve nerve regeneration outcomes. In this review we outline the regulatory processes that functionally distinct NGCs may need to address and explore new modifications and the complications that may need to be addressed during the translation process from bench to clinic.

An update-tissue engineered nerve grafts for the repair of peripheral nerve injuries

Peripheral nerve injuries (PNI) are caused by a range of etiologies and result in a broad spectrum of disability. While nerve autografts are the current gold standard for the reconstruction of extensive nerve damage, the limited supply of autologous nerve and complications associated with harvesting nerve from a second surgical site has driven groups from multiple disciplines, including biomedical engineering, neurosurgery, plastic surgery, and orthopedic surgery, to develop a suitable or superior alternative to autografting. Over the last couple of decades, various types of scaffolds, such as acellular nerve grafts (ANGs), nerve guidance conduits, and non-nervous tissues, have been filled with Schwann cells, stem cells, and/or neurotrophic factors to develop tissue engineered nerve grafts (TENGs). Although these have shown promising effects on peripheral nerve regeneration in experimental models, the autograft has remained the gold standard for large nerve gaps. This review provides a discussion of recent advances in the development of TENGs and their efficacy in experimental models. Specifically, TENGs have been enhanced via incorporation of genetically engineered cells, methods to improve stem cell survival and differentiation, optimized delivery of neurotrophic factors via drug delivery systems (DDS), co-administration of platelet-rich plasma (PRP), and pretreatment with chondroitinase ABC (Ch-ABC). Other notable advancements include conduits that have been bioengineered to mimic native nerve structure via cell-derived extracellular matrix (ECM) deposition, and the development of transplantable living nervous tissue constructs from rat and human dorsal root ganglia (DRG) neurons. Grafts composed of non-nervous tissues, such as vein, artery, and muscle, will be briefly discussed.

Effects of Localized X-Ray Irradiation on Peripheral Nerve Regeneration in Transected Sciatic Nerve in Rats

Low-dose radiation has been used in clinical and experimental models for the prevention of scarring and for fracture healing. There is evidence that low-dose radiation improves the hormesis of various cell types but little is known about its effects on peripheral nerve tissue. In this study, we investigated the beneficial effects of low-dose radiation on the regeneration of transectional peripheral nerve injury in an experimental rat model. Seventy-two male Sprague-Dawley rats received transection injury to the left sciatic nerves, and the nerves were subsequently sutured by epineurium end-to-end anastomosis to restore continuity. Animals were randomly assigned to one of two treatment groups (n = 36/group): 1 Gy X-ray irradiation or control (sham irradiation). Gait analysis, electrophysiological examination and morphological investigations were performed. In addition, Western blot and qRT-PCR were performed to determine the level of vascular endothelial growth factor (VEGF) and growth-associated protein-43 (GAP-43). Content of VEGF and GAP-43 in the regenerated sciatic nerve of the irradiated group was higher than the control group. At 4 to 12 weeks after surgery, the irradiated animals exhibited a significantly improved functional recovery relative to controls. At 12 weeks after surgery, amplitude and conduction velocity of the irradiated group were higher than the control group (P < 0.05). The number of nerve fibers, diameter of axons and morphological structure of the myelin sheath in the irradiated group were superior to those of the control group. These results suggest that low-dose radiation contributed to regeneration and functional recovery after transverse peripheral nerve injury by inducing increased production of VEGF and GAP-43, which promote the axonal regeneration and myelination.

Dual-factor loaded functional silk fibroin scaffolds for peripheral nerve regeneration with the aid of neovascularization

Dual-factor loaded functional silk fibroin scaffolds enhanced peripheral nerve regeneration with the aid of neovascularization.

Chitooligosaccharide Inhibits Scar Formation and Enhances Functional Recovery in a Mouse Model of Sciatic Nerve Injury

Chitooligosaccharide (COS) has been shown to induce fibroblast apoptosis, indicating that it could be used as a material to inhibit scar formation. In the present study, we used a mouse model of sciatic nerve injury (SNI) to determine the role of COS in scar inhibition and functional recovery. The animals were divided into three groups: SNI, SNI + vehicle, and SNI + COS group. We performed a series of functional and histological examinations at ctrl, 0 min, 14 days, and 42 days, including behavioral recovery, percentage of regenerating axons, degree of scar formation, vascular changes, type I and type III collagen ratio, and percentage of demyelinated axons. The SNI + COS group exhibited better recovery of sensory and motor function and less scar formation. Two-photon microscopy showed that the percentage of regenerating axons was highest in the SNI + COS group at 14 and 42 days. Our results suggested that COS can inhibit scar formation and enhance functional recovery by inducing fibroblast death, altering the proportion of different vascular diameters, changing the ratio of type I/type III collagen, and reducing the percentage of demyelinated axons. COS might be a useful drug in the treatment of SNI to reduce scar formation, but additional research is required to clarify the relevant molecular pathways.

Orientated Guidance of Peripheral Nerve Regeneration Using Conduits with a Microtube Array Sheet (MTAS)

Material surface topography has been shown to affect the biological behavior of cells in vitro; however, the in vivo effect on peripheral nerve regeneration has not been explored. Here, we studied the potential of a microtube array sheet (MTAS) with a unique longitudinal surface topography to promote peripheral nerve regeneration efficiency, both in vivo and in vitro. Schwann cells, spinal cord motor neurons, and dorsal root ganglion neurons were seeded on the MTAS to study the effect of the construct on the biological properties and behaviors of neural cells. The MTAS guided the oriented migration of Schwann cells without affecting other critical biological properties, such as proliferation and neurotrophin expression. In addition, the MTAS guided the directed extension of neurites from both types of neurons. Next, we tested the capability of the MTAS to facilitate peripheral nerve regeneration by bridging a 10 mm sciatic nerve defect in rats with a nerve conduit equipped with an MTAS lining. The MTAS significantly promoted peripheral nerve regeneration, as suggested by the greater fiber caliber in the midconduit and the greater abundance of fibers in nerve segment distal to the conduit. Moreover, scanning electron microscopy (SEM) analysis suggested the orientated guidance of nerve regeneration by the MTAS, as indicated by the smaller eccentricity of the nerve fibers and the concordant arrangement of the collagen fiber in both the fibers and the matrix in the MTAS group. Our results collectively suggest that the conduits with the MTAS developed in this study have significant potential for facilitating peripheral nerve regeneration by modifying critical biological behaviors and guiding orientated nerve growth.

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.