Critical functions of intra-axonally synthesized proteins are thought to depend on regulated recruitment of mRNA from storage depots in axons. Here we show that axotomy of mammalian neurons induces ...translation of stored axonal mRNAs via regulation of the stress granule protein G3BP1, to support regeneration of peripheral nerves. G3BP1 aggregates within peripheral nerve axons in stress granule-like structures that decrease during regeneration, with a commensurate increase in phosphorylated G3BP1. Colocalization of G3BP1 with axonal mRNAs is also correlated with the growth state of the neuron. Disrupting G3BP functions by overexpressing a dominant-negative protein activates intra-axonal mRNA translation, increases axon growth in cultured neurons, disassembles axonal stress granule-like structures, and accelerates rat nerve regeneration in vivo.
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Graphene, as a promising biomaterial, has received great attention in biomedical fields due to its intriguing properties, especially the conductivity and biocompatibility. Given ...limited studies on the effects of graphene-based scaffolds on peripheral nerve regeneration in vitro and in vivo under electrical stimulation (ES), the present study was intended to systematically investigate how conductive graphene-based nanofibrous scaffolds regulate Schwann cell (SC) behavior including migration, proliferation and myelination, and PC12 cell differentiation in vitro via ES, and whether these conductive scaffolds could guide SC migration and promote nerve regeneration in vivo. Briefly, the reduced graphene oxide (RGO) was coated onto ApF/PLCL nanofibrous scaffolds via in situ redox reaction of the graphene oxide (GO). In vitro, RGO-coated ApF/PLCL (AP/RGO) scaffolds significantly enhanced SC migration, proliferation, and myelination including myelin-specific gene expression and neurotrophic factor secretion. The conditioned media of SCs cultured on AP/RGO scaffolds under ES could induce the differentiation of PC12 cells in a separate culture. In addition, PC12 cells cultured on the conductive AP/RGO scaffolds also showed elevated differentiation upon ES. In vivo implantation of the conductive AP/RGO nerve guidance conduits into rat sciatic nerve defects exhibited a similar healing capacity to autograft, which is the current gold standard in peripheral nerve regeneration. In view of the performance of AP/RGO scaffolds in modulating cell functions in vitro and promoting nerve regeneration in vivo, it is expected that the graphene-based conductive nanofibrous scaffolds would exhibit their potential in peripheral nerve repair and regeneration.
Despite the demonstrated capability of bridging the distal and proximal peripheral nerves, it remains a significant challenge with current artificial nerve conduits to achieve the desired physiological functions, e.g., the transmission of electrical stimuli. Herein, we explored the possibility of combining the conductive properties of graphene with electrospun nanofiber to create the electroactive biomimetic scaffolds for nerve tissue regeneration. In vitro and in vivo studies were carried out: (1) In vitro, the conductive nanofibrous scaffolds significantly promoted SC migration, proliferation and myelination including myelin specific gene expression and neurotrophicfactor secretion, and induced PC12 cell differentiation with electrical stimulation. (2) In vivo, the conductive nerve guidance conduit exhibited similar effects with the gold standard autograft. In view of the performance of this conductive scaffold in modulating the cell functions in vitro and promoting nerve regeneration in vivo, it is expected that the graphene-modified nanofibrous scaffolds will exhibit their potential in peripheral nerve repair and regeneration.
The polarity of nerve grafts does not interfere with axon growth. Our goal was to investigate whether axons can regenerate in a retrograde fashion within sensory pathways and then extend into motor ...pathways, leading to muscle reinnervation.
Fifty-four rats were randomized into four groups. In Group 1, the ulnar nerve was connected end-to-end to the superficial radial nerve after neurectomy of the radial nerve in the axilla. In Group 2, the ulnar nerve was connected end-to-end to the radial nerve distal to the humerus; the radial nerve then was divided in the axilla. In Group 3, the radial nerve was divided in the axilla, but no nerve reconstruction was performed. In Group 4, the radial nerve was crushed in the axilla. Over 6 months, we behaviorally assessed the recovery of toe spread in the right operated-upon forepaw by lifting the rat by its tail and lowering it onto a flat surface. Six months after surgery, rats underwent reoperation, nerve transfers were tested electrophysiologically, and the posterior interosseous nerve (PIN) was removed for histological evaluation.
Rats in the crush group recovered toe spread between 5 and 8 days after surgery. Rats with nerve transfers demonstrated electrophysiological and histological findings of nerve regeneration but no behavioral recovery.
Ulnar nerve axons regrew into the superficial radial nerve and then into the PIN to reinnervate the extensor digitorum communis. We were unable to demonstrate behavioral recovery because rats cannot readapt to cross-nerve transfer.
•Schwann cells showed high proliferation on tantalum surface.•Tantalum coated - poly (L-lactic acid) nerve conduit promoted peripheral nerve regeneration.•Absence of scar tissue formation or ...inflammation reaction around tantalum coated - poly (L-lactic acid) nerve conduit.
Recently, Tantalum (Ta) has been re-explored and used with bone implants to promote bone regeneration. It has previously been extensively used as a nerve suture material; however, its use was abandoned because of the formation of scar tissue. In this study, we constructed a nerve conduit made of poly (L-lactic acid) PLA (outer layer) and tantalum Ta (inner layer) to evaluate its efficiency in the promotion of peripheral nerve regeneration.
First, we conducted an in vitro study to evaluate the viability and proliferation of Schwann cells and rat pheocromocytoma (PC-12) cells on Ta-PLA sheets using Enhanced Cell Viability Assay Kit (EZ-CYTOX). An in vivo study was then performed using Sprague Dawley rats that were randomly divided into the following three groups: sham, PLA, and Ta-PLA nerve conduits. The nerve conduit was placed over a 10-mm gap of the rat sciatic nerve to promote nerve regeneration. The rats were observed over 12 wk with weekly sciatic functional index functional assessment. At the end of 12 wk, the nerve regeneration outcome was assessed through dorsal root ganglions (DRG) retrograde neurons labeling, histomorphometric analysis, and histological analysis.
The in vitro study showed significant viability and proliferation of Schwann cells in the Ta-PLA group than in the other groups. In the in vivo study, the gross findings revealed well-regenerated neural tissue in both the experimental groups with no scarring. The histological analysis showed that about 50 % of the conduits were filled with axons with a higher tendency for peripheral growth in the PLA group than for central growth within the Ta-PLA group conduits. The retrograde labeled neurons were significantly higher in Ta-PLA group than in the PLA group. Ta-PLA showed non-significant difference in the total fibers compared to the sham group.
Tantalum proved favorable for the growth of Schwann cells.In vivo, Ta-PLA nerve conduit induced peripheral nerve regeneration without scar tissue formation.
Methods in nerve tissue engineering for peripheral nerve regeneration have recently focused on the application of rapid three-dimensional (3D) printing with resorbable and degradable biomaterial ink. ...The technique aims to design and fabricate nerve guidance conduits (NGCs) to repair large-gap nerve injuries. In this study, Digital light processing (DLP)-based printing of multichannel NGCs for peripheral nerve regeneration by using gelatin methacrylate (GelMA) hydrogels was presented. Multichannel NGCs with different inner diameters were successfully fabricated using desired patterns, and optimal printing parameters were investigated. In vitro co-culturing of PC12 cells demonstrated that NGCs supported the survival, proliferation, and migration of neural cells along the longitudinal channel. The results also showed that neural crest stem cells could be induced to differentiate into neurons on fabricated conduits. This method will provide a rapid and accurate manner to fabricate complex NGCs, which can be potentially used to repair peripheral nerves.
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•NGCs with multiple channels were fabricated by DLP-based 3D printing with GelMA.•NGCs could support the survival, proliferation, and migration of neural cells.•Neural crest stem cells could differentiate into neurons on the conduits.
Abstract Several nerve guidance conduits (NGCs) and nerve protectant wraps are approved by the US Food and Drug Administration (FDA) for clinical use in peripheral nerve repair. These devices cover a ...wide range of natural and synthetic materials, which may or may not be resorbable. This review consolidates the data pertaining to all FDA approved materials into a single reference, which emphasizes material composition alongside pre-clinical and clinical safety and efficacy (where possible). This article also summarizes the key advantages and limitations for each material as noted in the literature (with respect to the indication considered). In this context, this review provides a comprehensive reference for clinicians which may facilitate optimal material/device selection for peripheral nerve repair. For materials scientists, this review highlights predicate devices and evaluation methodologies, offering an insight into current deficiencies associated with state-of-the-art materials and may help direct new technology developments and evaluation methodologies thereof.
The ability to repair or promote regeneration within the adult human brain has been envisioned for decades. Until recently, such efforts mainly involved delivery of growth factors and cell ...transplants designed to rescue or replace a specific population of neurons, and the results have largely been disappointing. New approaches using stem-cell-derived cell products and direct cell reprogramming have opened up the possibility of reconstructing neural circuits and achieving better repair. In this Review we briefly summarize the history of neural repair and then discuss these new therapeutic approaches, especially with respect to chronic neurodegenerative disorders.
Severe injuries to peripheral nerves are challenging to repair. Standard-of-care treatment for nerve gaps >2 to 3 centimeters is autografting; however, autografting can result in neuroma formation, ...loss of sensory function at the donor site, and increased operative time. To address the need for a synthetic nerve conduit to treat large nerve gaps, we investigated a biodegradable poly(caprolactone) (PCL) conduit with embedded double-walled polymeric microspheres encapsulating glial cell line-derived neurotrophic factor (GDNF) capable of providing a sustained release of GDNF for >50 days in a 5-centimeter nerve defect in a rhesus macaque model. The GDNF-eluting conduit (PCL/GDNF) was compared to a median nerve autograft and a PCL conduit containing empty microspheres (PCL/Empty). Functional testing demonstrated similar functional recovery between the PCL/GDNF-treated group (75.64 ± 10.28%) and the autograft-treated group (77.49 ± 19.28%); both groups were statistically improved compared to PCL/Empty-treated group (44.95 ± 26.94%). Nerve conduction velocity 1 year after surgery was increased in the PCL/GDNF-treated macaques (31.41 ± 15.34 meters/second) compared to autograft (25.45 ± 3.96 meters/second) and PCL/Empty (12.60 ± 3.89 meters/second) treatment. Histological analyses included assessment of Schwann cell presence, myelination of axons, nerve fiber density, and
-ratio. PCL/GDNF group exhibited a statistically greater average area occupied by individual Schwann cells at the distal nerve (11.60 ± 33.01 μm
) compared to autograft (4.62 ± 3.99 μm
) and PCL/Empty (4.52 ± 5.16 μm
) treatment groups. This study demonstrates the efficacious bridging of a long peripheral nerve gap in a nonhuman primate model using an acellular, biodegradable nerve conduit.
Peripheral nerve injury remains a major cause of morbidity in trauma patients. Despite advances in microsurgical techniques and improved understanding of nerve regeneration, obtaining satisfactory ...outcomes after peripheral nerve injury remains a difficult clinical problem. There is a growing body of evidence in preclinical animal studies demonstrating the supportive role of stem cells in peripheral nerve regeneration after injury. The characteristics of both mesoderm‐derived and ectoderm‐derived stem cell types and their role in peripheral nerve regeneration are discussed, specifically focusing on the presentation of both foundational laboratory studies and translational applications. The current state of clinical translation is presented, with an emphasis on both ethical considerations of using stems cells in humans and current governmental regulatory policies. Current advancements in cell‐based therapies represent a promising future with regard to supporting nerve regeneration and achieving significant functional recovery after debilitating nerve injuries.
Hydrogels have promising application in tissue regeneration due to their excellent physicochemical and biocompatible properties, whereas anisotropic micropatterns are been proven to directionally ...induce cell alignment and accelerate cell migration. However, an effect of biofunctionalized anisotropic hydrogel micropatterns on nerve regeneration has rarely been reported. In this study, the anisotropic polyacrylamide (PAM) hydrogel micropatterns with aligned ridge/groove structures were first prepared via in situ free radical polymerization and micromolding, and then biofunctionalized using YIGSR peptide for better promoting cell growth. The morphology, swelling ratio, wettability, mechanical properties, and stability of the prepared hydrogel were characterized. The successful immobilization of YIGSR peptide on the PAM hydrogel was monitored using FTIR, immunofluorescence staining, and ELISA. The effects on adhesion, directional growth, and biological function of Schwann cells were evaluated. The results displayed that the anisotropic PAM hydrogel micropatterns with inner porous structure possessed good stability, swelling, and mechanical properties. The YIGSR peptide could be well immobilized on hydrogel micropatterns with a percentage of 62.6%. The biofunctionalized anisotropic hydrogel micropatterns could effectively regulate the orientation growth of Schwann cells, and obviously up-regulate BDNF (40%) and β-actin (50%) expression compared with single hydrogel micropatterns, without negatively affecting the normal secretion of neurotropic factors by Schwann cells. To the best of our knowledge, this is the first time to study the construction and effect of biofunctionalized anisotropic hydrogel micropatterns on nerve regeneration, which may provide an experimental and theoretical basis for the design and development of artificial implants for nerve regeneration application.
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