Nerve guide conduits for peripheral nerve injury repair: A review on design, materials and fabrication methods

Piezo-electronics: A paradigm for self-powered bioelectronics

Recent breakthroughs in electroactive piezo-biomaterials have driven significant progress towards the development of both, diagnostic and therapeutic purposes, enabling vital sign monitoring, such as heart rate, etc. while also supporting tissue regeneration. Bioelectronic medicine provides a promising method for controlling tissue and organ functions, with 'piezo-electronics' emphasizing the lasting role of electro-active piezo-biomaterials in self-powered devices. This article critically analyses a range of self-powered bioelectronic technologies, including wearable, implantable, regenerative, and cancer therapy applications. Piezoelectric nanogenerators (PENGs) are essential in wearable and implantable systems such as pressure and strain measurements, sensor for human-machine interface, self-powered pacemakers, deep brain stimulation, cochlear implant, tissue restoration and sustained drug delivery, controlled by electrical stimuli from PENGs etc. Regenerative bioelectronics play a key role in healing tissues, such as bone, neural, cardiac, tendon, ligament, skeletal muscle etc. using self-powered implants, which have ability to restore tissue functionality. Additionally, piezoelectric biomaterials are being utilized in cancer treatment, offering more targeted therapies with minimal side effects. Various cancerous tumors can be destroyed by reactive oxygen species (ROS), generated by piezo-biomaterials. Data science is also emerging as a crucial tool in optimizing self-powered bioelectronics, enhancing patient outcomes through data-driven strategies, and broadening the role of bioelectronic technologies in modern healthcare.

A novel flexible nerve guidance conduit promotes nerve regeneration while providing excellent mechanical properties

JOURNAL/nrgr/04.03/01300535-202507000-00029/figure1/v/2024-09-09T124005Z/r/image-tiff Autografting is the gold standard for surgical repair of nerve defects > 5 mm in length; however, autografting is associated with potential complications at the nerve donor site. As an alternative, nerve guidance conduits may be used. The ideal conduit should be flexible, resistant to kinks and lumen collapse, and provide physical cues to guide nerve regeneration. We designed a novel flexible conduit using electrospinning technology to create fibers on the innermost surface of the nerve guidance conduit and employed melt spinning to align them. Subsequently, we prepared disordered electrospun fibers outside the aligned fibers and helical melt-spun fibers on the outer wall of the electrospun fiber lumen. The presence of aligned fibers on the inner surface can promote the extension of nerve cells along the fibers. The helical melt-spun fibers on the outer surface can enhance resistance to kinking and compression and provide stability. Our novel conduit promoted nerve regeneration and functional recovery in a rat sciatic nerve defect model, suggesting that it has potential for clinical use in human nerve injuries.

ARA290, an alternative of erythropoietin, inhibits activation of NLRP3 inflammasome in schwann cells after sciatic nerve injury

The challenge of repairing peripheral nerve injury is a critical issue that needs to be addressed urgently. Previous research has shown that erythropoietin (EPO) and its prolonged peptides exhibit beneficial effects in neurological disorders. In our study, we demonstrated that both EPO and pyroglutamic acid helix B surface peptide (pHBSP, also known as ARA290) inhibit the early inflammatory response and promote functional recovery after sciatic nerve crush injury in rat models. Our experimental results demonstrate that significant inflammatory response occurred in Schwann cells after sciatic nerve injury, and that the activation of NLRP3 inflammasome in Schwann cells is inhibited after EPO and ARA290 treatment. Our study further demonstrated that EPO and ARA290 inhibit the activation of NLRP3 inflammasome in Schwann cells by inhibiting NF-κB phosphorylation and reducing reactive oxygen species (ROS) production. In summary, EPO and ARA290 promote repair and regeneration by inhibiting the activation of NLRP3 inflammasome after sciatic nerve injury.

Silk-based nerve guidance conduits with macroscopic holes modulate the vascularization of regenerating rat sciatic nerve

JOURNAL/nrgr/04.03/01300535-202506000-00029/figure1/v/2024-08-05T133530Z/r/image-tiff Peripheral nerve injuries induce a severe motor and sensory deficit. Since the availability of autologous nerve transplants for nerve repair is very limited, alternative treatment strategies are sought, including the use of tubular nerve guidance conduits (tNGCs). However, the use of tNGCs results in poor functional recovery and central necrosis of the regenerating tissue, which limits their application to short nerve lesion defects (typically shorter than 3 cm). Given the importance of vascularization in nerve regeneration, we hypothesized that enabling the growth of blood vessels from the surrounding tissue into the regenerating nerve within the tNGC would help eliminate necrotic processes and lead to improved regeneration. In this study, we reported the application of macroscopic holes into the tubular walls of silk-based tNGCs and compared the various features of these improved silk+ tNGCs with the tubes without holes (silk- tNGCs) and autologous nerve transplants in an 8-mm sciatic nerve defect in rats. Using a combination of micro-computed tomography and histological analyses, we were able to prove that the use of silk+ tNGCs induced the growth of blood vessels from the adjacent tissue to the intraluminal neovascular formation. A significantly higher number of blood vessels in the silk+ group was found compared with autologous nerve transplants and silk-, accompanied by improved axon regeneration at the distal coaptation point compared with the silk- tNGCs at 7 weeks postoperatively. In the 15-mm (critical size) sciatic nerve defect model, we again observed a distinct ingrowth of blood vessels through the tubular walls of silk+ tNGCs, but without improved functional recovery at 12 weeks postoperatively. Our data proves that macroporous tNGCs increase the vascular supply of regenerating nerves and facilitate improved axonal regeneration in a short-defect model but not in a critical-size defect model. This study suggests that further optimization of the macroscopic holes silk+ tNGC approach containing macroscopic holes might result in improved grafting technology suitable for future clinical use.

Global research trends of peripheral nerve surgery: a bibliometric and visualized analysis

Peripheral nerve surgery is an emerging research field gaining attention from neurosurgeons. However, a bibliometric analysis has yet to be conducted in this area. This study aims to visualize the hot spots and trends in publications of peripheral nerve surgery through bibliometric analysis, offering insights into potential future research directions. We analyzed all English-language publications (articles and reviews) on peripheral nerve surgery available in the Web of Science Core Collection from 1967 to 2024. The bibliometrix package, VOSviewer, and CiteSpace were used for visual network analyses of key indicators, including institutions, countries/regions, journals, authors, keywords, and references. Additionally, country maps were created by Scimago Graphica. A total of 605 papers were incorporated in the analysis. The number of publications and citations related to peripheral nerve surgery has increased annually. These publications originated from 947 institutions across 62 countries/regions, with the United States leading. The Mayo Clinic emerged as the most influential institution, while Anesthesia and Analgesia was identified as the journal with the highest number of publications in this area. We identified 2,963 authors, with Ilfeld. brian m. being the most prolific and frequently cited. Keyword cluster analysis revealed four clusters, indicating that surgery and treatment methods, injuries and complications, pain management, and nerve regeneration and repair will be key research hotspots moving forward. Peripheral nerve surgery is a rapidly growing field. Future research is expected to focus on topics related to surgery, injury, and pain management and recovery. Clinical trial number Not applicable.

Conductive Hydrogels with Topographical Geometry and Mechanical Robustness for Enhanced Peripheral Nerve Regeneration

Nerve guidance conduits (NGCs) emerge as a promising solution for nerve regeneration; however, conventional NGCs fail to fulfill the requirements for peripheral nerve regeneration, which are subjected to periodical yet vigorous stretching, bending, and compression. Here, we developed a fatigue-resistant conductive hydrogel-based NGC by integrating topographical geometry, enhanced electroactivity, and superior fatigue resistance within one unit. The hydrogel, consisting of a PVA matrix with PEDOT:PSS as a conductive filler, features a topographical alignment that promotes axonal growth and achieves a fatigue threshold over 500 J/m2, making it well-suited for sciatic nerve repairing. Phase segregation of PEDOT chains enhances its electrical conductivity (>500 S/m) and mitigates the interfacial impedance mismatch, allowing for high-efficiency bioelectrical signal transmission. In vivo studies on a rat sciatic nerve injury model corroborate the accelerated peripheral nerve regeneration through improved motor function recovery and efficient electrophysiological signal transmission. These findings establish our hydrogel-based NGCs as a promising solution for high-efficiency nerve regeneration through the synergy of topographical, mechanical, and electrical engineering.

Dual-regulation biomimetic composite nerve scaffold with oriented structure and conductive function for skin peripheral nerve injury repair

Skin peripheral nerve injury repair still faces significant clinical challenges. Although nerve tissue engineering scaffolds show potential, issues such as limited functionality and low repair efficiency persist. This study developed a dual-regulation biomimetic composite nerve scaffold with oriented structure and conductive function to promote nerve injury repair. The structural layer was a chitosan (CS)/polycaprolactone (PCL) oriented nanofiber membrane, which could promote cell adhesion and induce directional growth of cells. The functional layer was a CS/sodium alginate (SA) ionic conductive hydrogel, which could enhance endogenous electric fields to promote cell proliferation and differentiation. The two layers were combined through physical crosslinking, avoiding the use of chemical adhesives and preserving the surface morphology of the nanofibrous membrane and the porous structure of the hydrogel. The biomimetic composite nerve scaffold exhibited layered degradability, excellent orientation, conductivity, and biocompatibility. Cell experiments indicated that the scaffold effectively induced directional migration, growth, and differentiation of cells and enhanced cell activity, thereby providing a favorable microenvironment for nerve regeneration. This study not only overcomes the limitation of functional singularity in traditional nerve scaffolds but also aligns with the forefront trend in tissue engineering toward multifunctional and biomimetic materials. It demonstrates great potential for treating complex conditions such as traumatic nerve defects and post-surgical nerve regeneration and has broad application prospects in the field of neural tissue engineering.

Dental pulp stem cells alleviate Schwann cell pyroptosis via mitochondrial transfer to enhance facial nerve regeneration

Dental pulp stem cells (DPSCs) have demonstrated remarkable potential in enhancing peripheral nerve regeneration, though the precise mechanisms remain largely unknown. This study investigates how DPSCs alleviate Schwann cell pyroptosis and restore mitochondrial homeostasis through intercellular mitochondrial transfer. In a crab-eating macaque model, we first observed that DPSC-loaded nerve conduits significantly promoted long-term nerve regeneration, facilitating tissue proliferation and myelin recovery. We further established a rat facial nerve injury (FNI) model and found that DPSC treatment reduced pyroptosis and mitochondrial ROS production in Schwann cells. A pivotal mitochondrial protective mechanism, resembling the effects of a ROS-targeted inhibitor, involved the transfer of mitochondria from DPSCs to pyroptosis-induced Schwann cells via tunneling nanotubes, while blocking intercellular junctions or mitochondrial function diminished the therapeutic effects. TNFα secreted by pyroptosis-induced Schwann cells activated the NF-κB pathway in DPSCs, enhancing mitochondrial transfer and adaptive stress responses, thereby promoting mitochondrial protection against pyroptosis in Schwann cells, as reflected in the improved therapeutic efficacy of TNFα-preconditioned DPSCs in the FNI model. These findings unveil a mechanism through which DPSCs foster nerve regeneration via mitochondrial transfer, presenting a promising strategy for enhancing stem cell-based therapies for nerve injuries.

Structured Light Projection Using Image Guide Fibers for In Situ Photo-biofabrication

Light-based biofabrication techniques have revolutionized the field of tissue engineering and regenerative medicine. Specifically, the projection of structured light, where the spatial distribution of light is controlled at both macro and microscale, has enabled precise fabrication of complex three dimensional structures with high resolution and speed. However, despite tremendous progress, biofabrication processes are mostly limited to benchtop devices which limit the flexibility in terms of where the fabrication can occur. Here, a Fiber-assisted Structured Light (FaSt-Light) projection apparatus for rapid in situ crosslinking of photoresins is demonstrated. This approach uses image-guide fiber bundles which can project bespoke images at multiple wavelengths, enabling flexibility and spatial control of different photoinitiation systems and crosslinking chemistries and also the location of fabrication. Coupling of different sizes of fibers and different lenses attached to the fibers to project small (several mm) or large (several cm) images for material crosslinking is demonstrated. FaSt-Light allows control over the cross-section of the crosslinked resins and enables the introduction of microfilaments which can further guide cellular infiltration, differentiation, and anisotropic matrix production. The proposed approach can lead to a new range of in situ biofabrication techniques which improve the translational potential of photofabricated tissues and grafts.

Advanced development of conductive biomaterials for enhanced peripheral nerve regeneration: a review

Peripheral nerve injury (PNI), as a major cause of disability worldwide, makes it difficult to achieve effective repair and regeneration. Including autologous nerve transplantation, traditional therapies are restricted by surgical intricacy, donor scarcity, and inconsistent recovery effects. As to nerve guidance conduits (NGCs), conductive materials have brought novel pathways for PNI repair. Such materials boost nerve regeneration via electrical stimulation and bring key mechanical stability and biophysical signaling. This review summarizes the progress in conductive materials for PNI therapy while emphasizing their functions in electrical stimulation (ES), bioelectric signal transmission, and cell behavior guidance, as well as revealing the design and function needs of nerve conduits. Additionally, our review highlights the demand for follow-up studies to accentuate material optimization and improve real-time electrical signal supervision. Accordingly, this research is insightful and contributes to developing PNI repair. This results in more efficacious therapies and enhanced outcomes.

Optimizing Peripheral Nerve Regeneration: Surgical Techniques, Biomolecular and Regenerative Strategies-A Narrative Review

Peripheral nerve injury disrupts the function of the peripheral nervous system, leading to sensory, motor, and autonomic deficits. While peripheral nerves possess an intrinsic regenerative capacity, complete sensory and motor recovery remains challenging due to the unpredictable nature of the healing process, which is influenced by the extent of the injury, age, and timely intervention. Recent advances in microsurgical techniques, imaging technologies, and a deeper understanding of nerve microanatomy have enhanced functional outcomes in nerve repair. Nerve injury initiates complex pathophysiological responses, including Wallerian degeneration, macrophage activation, Schwann cell dedifferentiation, and axonal sprouting. Complete nerve disruptions require surgical intervention to restore nerve continuity and function. Direct nerve repair is the gold standard for clean transections with minimal nerve gaps. However, in cases with larger nerve gaps or when direct repair is not feasible, alternatives such as autologous nerve grafting, vascularized nerve grafts, nerve conduits, allografts, and nerve transfers may be employed. Autologous nerve grafts provide excellent biocompatibility but are limited by donor site morbidity and availability. Vascularized grafts are used for large nerve gaps and poorly vascularized recipient beds, while nerve conduits serve as a promising solution for smaller gaps. Nerve transfers are utilized when neither direct repair nor grafting is possible, often involving re-routing intact regional nerves to restore function. Nerve conduits play a pivotal role in nerve regeneration by bridging nerve gaps, with significant advancements made in material composition and design. Emerging trends in nerve regeneration include the use of 3D bioprinting for personalized conduits, gene therapy for targeted growth factor delivery, and nanotechnology for nanofiber-based conduits and stem cell therapy. Advancements in molecular sciences have provided critical insights into the cellular and biochemical mechanisms underlying nerve repair, leading to targeted therapies that enhance axonal regeneration, remyelination, and functional recovery in peripheral nerve injuries. This review explores the current strategies for the therapeutic management of peripheral nerve injuries, highlighting their indications, benefits, and limitations, while emphasizing the need for tailored approaches based on injury severity and patient factors.

3-Dimensional printing and bioprinting in neurological sciences: applications in surgery, imaging, tissue engineering, and pharmacology and therapeutics

The rapid evolution of three-dimensional printing (3DP) has significantly impacted the medical field. In neurology for instance, 3DP has been pivotal in personalized surgical planning and education. Additionally, it has facilitated the creation of implants, microfluidic devices, and optogenetic probes, offering substantial implications for medical and research applications. Additionally, 3D printed nasal casts are showing great promise for targeted brain drug delivery. 3DP has also aided in creating 3D "phantoms" aligning with advancements in neuroimaging, and in the design of intricate objects for investigating the neurobiology of sensory perception. Furthermore, the emergence of 3D bioprinting (3DBP), a fusion of 3D printing and cell biology, has created new avenues in neural tissue engineering. Effective and ethical creation of tissue-like biomimetic constructs has enabled mechanistic, regenerative, and therapeutic evaluations. While individual reviews have explored the applications of 3DP or 3DBP, a comprehensive review encompassing the success stories across multiple facets of both technologies in neurosurgery, neuroimaging, and neuro-regeneration has been lacking. This review aims to consolidate recent achievements of both 3DP and 3DBP across various neurological science domains to encourage interdisciplinary research among neurologists, neurobiologists, and engineers, in order to promote further exploration of 3DP and 3DBP methodologies to novel areas of neurological science research and practice.

Induced Pluripotent Stem Cell-Derived Exosomes Promote Peripheral Nerve Regeneration in a Rat Sciatic Nerve Crush Injury Model: A Safety and Efficacy Study

Peripheral nerve injury (PNI) remains a significant clinical challenge, often leading to long-term functional impairment. Despite advances in therapies, current repair strategies offer unsatisfactory clinical outcomes. Exosomes derived from induced pluripotent stem cells (iPSC-Exos) have emerged as a promising therapeutic approach in regenerative medicine. This study assesses the efficacy and safety of iPSC-Exos in a rat model of sciatic nerve crush injury. Briefly, iPSCs were generated from peripheral blood mononuclear cells (PBMCs) of healthy donors using Sendai virus vectors and validated for pluripotency. iPSC-Exos were characterized and injected at the injury site. Functional recovery was assessed through gait analysis, grip strength, and pain response. Histological and molecular analyses were used to examine axonal regeneration, myelination, Schwann cell (SC) activation, angiogenesis, and changes in gene expression. iPSC-Exos were efficiently internalized by SC, promoting their proliferation. No adverse effects were observed between groups on body weight, organ histology, or hematological parameters. iPSC-Exos injection significantly enhanced nerve regeneration, muscle preservation, and vascularization, with RNA sequencing revealing activation of PI3K-AKT and focal adhesion pathways. These findings support iPSC-Exos as a safe and effective non-cell-based therapy for PNIs, highlighting their potential for clinical applications in regenerative medicine.

CP/HA/HGF Conductive Composite Scaffolds with Synergistic Electrical Stimulation for Nerve Regeneration

The challenge of nerve regeneration stems from the diminished vitality of mature neurons post-injury. The construction of a suitable microenvironment at the injury site to facilitate axonal regeneration is a crucial aspect of nerve injury repair. In this work, a conductive and biocompatible composite material, CP/HA/HGF, is designed by grafting polypyrrole onto chitosan and compounding it with hyaluronic acid and functional short peptides for neural regeneration. Comprehensive material characterizations shows that CP/HA/HGF holds the potential as a scaffold material based on its good overall performance. In vitro experiments revealed that the combination of conductive composite scaffolds and electrical stimulation facilitated axonal growth and myelin formation in the dorsal root ganglion, while also promoting the migration of Schwann cells. Therefore, the conductive composite scaffold studied in this paper presents a promising strategy for enhancing neural regeneration.

Engineering the Future of Restorative Clinical Peripheral Nerve Surgery

Peripheral nerve injury is a significant clinical challenge, often leading to permanent functional deficits. Standard interventions, such as autologous nerve grafts or distal nerve transfers, require sacrificing healthy nerve tissue and typically result in limited motor or sensory recovery. Nerve regeneration is complex and influenced by several factors: 1) the regenerative capacity of proximal neurons, 2) the ability of axons and support cells to bridge the injury, 3) the capacity of Schwann cells to maintain a supportive environment, and 4) the readiness of target muscles or sensory organs for reinnervation. Emerging bioengineering solutions, including biomaterials, drug delivery systems, fusogens, electrical stimulation devices, and tissue-engineered products, aim to address these challenges. Effective translation of these therapies requires a deep understanding of the physiology and pathology of nerve injury. This article proposes a comprehensive framework for developing restorative strategies that address all four major physiological responses in nerve repair. By implementing this framework, we envision a paradigm shift that could potentially enable full functional recovery for patients, where current approaches offer minimal hope.

Photo-Responsive H2S Composite System Regulates the Nerve Regeneration Microenvironment Through Multiple Pathways

After injury, the imbalance of the regeneration microenvironment caused by inflammation, oxidative stress, insufficient neurovascularization, and inadequate energy supply affects nerve regeneration. Drug-delivery nerve conduits play a role in repairing the regenerative microenvironment. However, traditional drugs often fail to cross the blood-nerve barrier and lack multifunctionality, limiting the effectiveness of conduit therapy. Therefore, it is necessary to construct a multifunctional conduit that regulate the regeneration microenvironment timely and effectively. Herein, a photo-responsive hydrogen sulfide (H2S) composite nerve conduit, artificially controlled H2S release, is developed. A new structure of zinc-citric acid organic metal framework (Zn-CA MOFs) is utilized to improve its drug loading rate, achieving the joint regulation of the nerve regeneration microenvironment by H2S and Zn2+. In addition, RGD modification of polyester amide (P(CL-MMD-MAC)-RGD)) combined with aligned structure is used to improve the performance of the conduit. Relevant results demonstrate that H2S and Zn2+ can regulate inflammatory response and oxidative stress and promote mitochondrial function recovery and angiogenesis. Furthermore, the aligned structure can promote cell adhesion and guide cell directed migration. Overall, this study provides a method of combining gas neurotransmitters with ions to improve the nerve regeneration microenvironment, accelerate nerve regeneration, and restore motor function.

Advances in biomaterial-based tissue engineering for peripheral nerve injury repair

Peripheral nerve injury is a common clinical disease. Effective post-injury nerve repair remains a challenge in neurosurgery, and clinical outcomes are often unsatisfactory, resulting in social and economic burden. Particularly, the repair of long-distance nerve defects remains a challenge. The existing nerve transplantation strategies show limitations, including donor site morbidity and immune rejection issues. The multiple studies have revealed the potential of tissue engineering strategies based on biomaterials in the repair of peripheral nerve injuries. We review the events of regeneration after peripheral nerve injury, evaluates the efficacy of existing nerve grafting strategies, and delves into the progress in the construction and application strategies of different nerve guidance conduits. A spotlight is cast on the materials, technologies, seed cells, and microenvironment within these conduits to facilitate optimal nerve regeneration. Further discussion was conducted on the approve of nerve guidance conduits and potential future research directions. This study anticipates and proposes potential avenues for future research, aiming to refine existing strategies and uncover innovative approaches in biomaterial-based nerve repair. This study endeavors to synthesize the collective insights from the fields of neuroscience, materials science, and regenerative medicine, offering a multifaceted perspective on the role of biomaterials in advancing the frontiers of peripheral nerve injury treatment.

Folic Acid Promotes Peripheral Nerve Injury Repair via Regulating DNM3-AKT Pathway Through Mediating Methionine Cycle Metabolism

Emerging evidence suggests that folic acid (FA) supports nerve repair, but its beneficial effects in peripheral nerve injury (PNI) remains unclear. This study aims to investigate protective effects of FA against PNI and the underlying molecular mechanisms. High-performance liquid chromatography-tandem mass spectrometry was utilized for precise quantification of metabolites. A sciatic nerve crush injury model was established in rats, followed by assessments of cell proliferation, apoptosis, and motor function using CCK-8 assays, flow cytometry, and the balance beam test, respectively. Neuromorphological observations, electromyography, and ELISA were conducted to evaluate structural, electrophysiological, and biochemical parameters. In vitro, FA restored methionine cycle balance in Schwann cells and neurons disrupted by enzyme inhibition, improving cell viability, reducing apoptosis, and preserving cellular structure. In vivo, FA supplementation restored S-adenosylmethionine and homocysteine levels in a methionine metabolism disorder model and enhanced motor function, neural morphology, neuron survival, and electrophysiological recovery after PNI. Epigenetic analyses revealed that FA modulated DNA methylation and histone modifications of the DNM3 promoter, influencing gene expression. Furthermore, FA facilitated nerve repair via the DNM3-AKT pathway, regulating apoptosis, autophagy, and oxidative stress-related enzymes. These findings highlight FA's potential in promoting nerve repair through metabolic and epigenetic mechanisms.

Silk fibroin-hyaluronic acid nanofibers for peripheral nerve regeneration

Peripheral nerve injuries are common and a major source of pain that can lead to debilitating loss of function. Current treatments are limited, with autologous nerve grafts being the gold standard treatment for nerve injuries. However, autografting is not always successful and can lead to increased debilitation through donor site morbidity. Tissue engineering seeks to improve nerve injury treatment though the use of nerve conduits. Conduits made from a functional biomaterial can be implanted into a nerve injury site encouraging and controlling axonal regrowth without causing additional harm to the patient. Both silk fibroin (SF) and hyaluronic acid (HA) have been proven successful in the field of neural tissue engineering. SF has excellent mechanical properties and is biocompatible. HA is part of the extracellular matrix and had been used in nerve regeneration applications. This study developed aligned combination SF-HA nanofibers through electrospinning that could be used within a nerve conduit. Both materials were methacrylated to allow for photocrosslinking and additional control over material properties. Methcrylated SF-HA was tested alongside a material containing only methacrylated HA that has already proven to be effective in literature. When characterizing the materials, it was found that through chemical methacrylation HA was substituted at 60% while SF reported a 30% substitution. Electrospun SF-HA nanofibers were found to have a greater diameter than HA fibers; however, SF-HA was found to be more aligned with greater surface hydrophobicity. Mechanically, it was found that both materials exceeded the elastic modulus of native tissue, but SF-HA far exceeded HA in elasticity and overall fiber extension. Furthermore, human Schwann cells attached, proliferated, and released more pro-regenerative growth factors on SF-HA than HA. Dorsal root ganglia neurons also displayed longer neurite extensions on SF-HA fibers. We concluded that SF-HA nanofibers have potential as a nerve conduit material.

Adhesive and Conductive Fibrous Hydrogel Bandages for Effective Peripheral Nerve Regeneration

Peripheral nerve injury is a common disease resulting in reversible and irreversible impairments of motor and sensory functions. In addition to conventional surgical interventions such as nerve grafting and neurorrhaphy, nerve guidance conduits are used to effectively support axonal growth without unexpected neuroma formation. However, there are still challenges to secure tissue-mimetic mechanical and electrophysiological properties of the conduit materials. Herein, the phenylborate-tethered hydrogel-assisted doping effect is elucidated on conductive polymers, enhancing peripheral nerve regeneration when used as a sutureless bandage on the injured nerve. The adhesive and conductive nerve bandage consists of biocompatible hyaluronic acid hydrogel microfibers produced by electrospinning, followed by in situ conductive polypyrrole polymerization on the fibrous mat. Particularly, phenylborate groups enable high adsorption of pyrrole without mechanical crack on the hydrogel network and allow tissue-like stretchability and on-nerve adhesiveness. In a rat crushed nerve injury model, the nerve bandage can effectively promote nerve regeneration through stable sutureless wrapping followed by great electrical transmission on the defect region, showing anatomical and functional recovery of the nerve tissues and preventing muscular atrophy. Such hydrogel fibrous bandages will be a promising surgical dressing to be combined with versatile biomedical devices/materials for peripheral nerve repair.

Perspectives on Schwann-like cells derived from bone marrow-mesenchymal stem cells: Advancing peripheral nerve injury therapies

Peripheral nerve injuries are clinical conditions that often result in functional deficits, compromising patient quality of life. Given the relevance of these injuries, new treatment strategies are constantly being investigated. Although mesenchymal stem cells already demonstrate therapeutic potential due to their paracrine action, the transdifferentiation of these cells into Schwann-like cells (SLCs) represents a significant advancement in nerve injury therapy. Recent studies indicate that SLCs can mimic the functions of Schwann cells, with promising results in animal models. However, challenges remain, such as the diversity of transdifferentiation protocols and the scalability of these therapies for clinical applications. A recent study by Zou et al provided a comprehensive overview of the role of bone marrow-derived mesenchymal stem cells in the treatment of peripheral nerve injuries. Therefore, we would like to discuss and explore the use of SLCs derived from bone marrow-derived mesenchymal stem cells in more detail as a promising alternative in the field of nerve regeneration.

Therapeutic potential of mesenchymal stem cells transplantation on traumatic facial nerve paralysis in two horses

Cell-based therapy has emerged as a promising strategy for treating peripheral nervous system (PNS) injuries across different species. However, there is a scarcity in the literature regarding the transplantation of mesenchymal stem cells (MSCs) for treating PNS injuries in horses. This report aims to describe the therapeutic potential of equine MSC transplantation in two horses with chronic traumatic facial nerve paralysis. Both horses presented with lip ptosis and right deviation of the nostril and upper lip, being clinically diagnosed with left facial nerve paralysis. Due to the refractoriness to conventional anti-inflammatory treatments, cell-based therapy was chosen. One horse received an autologous transplant of equine bone marrow-derived MSCs (EqBM-MSCs) four months after the traumatic event, while the other underwent three transplants of allogeneic equine adipose tissue-derived MSCs (EqAT-MSCs) at 30-day intervals, starting two months after the injury. All transplants were performed at three different sites around the facial nerve, at the level of bifurcation of the buccal branch in both horses. Physical and neurological assessments revealed significant clinical recovery within three months for the first horse and four months for the second. These findings demonstrated that equine MSCs transplants have great therapeutic potential for chronic traumatic facial nerve paralysis in horses, highlighting the relevance of MSCs- based therapy for peripheral nerve injuries.

Biocompatible EDOT-Pyrrole Conjugated Conductive Polymer Coating for Augmenting Cell Attachment, Activity, and Differentiation

Developing scaffolds supporting functional cell attachment and tissue growth is critical in basic cell research, tissue engineering, and regenerative medicine approaches. Though poly(ethylene glycol) (PEG) and its derivatives are attractive for hydrogels and scaffold fabrication, they often require bioactive modifications due to their bioinert nature. In this work, biomimetic synthesized conductive polypyrrole-poly(3,4-ethylenedioxythiophene) copolymer doped with poly(styrenesulfonate) (PPy-PEDOT:PSS) was used as a biocompatible coating for poly(ethylene glycol) diacrylate (PEGDA) hydrogel to support neuronal and muscle cells' attachment, activity, and differentiation. The synthesized copolymer was characterized by Raman spectroscopy and dynamic light scattering. Its electrochemical properties were studied using galvanostatic charge-discharge (GCD) and voltammetry. PPy-PEDOT:PSS-coated hydrogels were characterized by Raman spectroscopy and atomic force microscopy, and protein adsorption was assessed using a quartz crystal microbalance with dissipation monitoring. Attachment and differentiation of the ND7/23 neuron hybrid cell line and C2C12 myoblasts were evaluated by cell cytoskeleton staining and quantification of morphological parameters. Viability was assessed by live/dead staining using flow cytometry. Cortex neural activity was studied by calcium ion influx that could be detected through the dynamic fluorescence changes of Fluo-4. The PPy-PEDOT:PSS coating supported cell attachment and differentiation and was nontoxic to cells. Primary neurons attached and remained responsive to electrical stimulation. Altogether, the biocompatible copolymer PPy-PEDOT:PSS is a simple yet effective alternative for hydrogel coating and presents great potential as an interface for nervous and other electrically excitable tissues.

The Combination of Aligned PDA-Fe@PLCL Conduit with Aligned GelMA Hydrogel Promotes Peripheral Nerve Regeneration

Biomaterial-assisted therapeutic strategies enable precise modulation to direct endogenous cellular responses and harness regenerative capabilities for nerve repair. However, achieving effective cellular engagement during nerve remodeling remains challenging. Herein, a novel composite nerve guidance conduit (NGC), the GelMA/PLys@PDA-Fe@PLCL conduit is developed by combining aligned poly(l-lactide-co-caprolactone) (PLCL) nanofibers modified with polydopamine (PDA), ferrous iron (Fe3⁺), and polylysine (PLys) with aligned methacrylate-anhydride gelatin (GelMA) hydrogel nanofibers. PDA films exhibit strong adhesion and metal coordination properties, allowing Fe3⁺ irons to chelate with phenolic hydroxyl groups of dopamine derivatives, forming a metal-phenolic network on PLCL. PLys molecules are then grafted onto PDA-Fe3⁺ coating via Schiff base and Michael addition reactions. This multifunctional coating enhances surface roughness and zeta potential of PLCL nanofibers, imparts superhydrophilicity with anisotropic wetting behavior, and maintains wet tensile properties of substrates. In vitro studies show that the PLys@PDA-Fe coating significantly promotes aligned distribution of Schwann cells, improves cell adhesion and differentiation, and demonstrates notable antioxidant and anti-inflammatory properties. When implanted into nerve defects in rats, the multifunctional coating conduit combined with aligned GelMA hydrogel effectively accelerates axonal regeneration, remyelination, and angiogenesis, leading to enhanced motor function recovery. Overall, the GelMA/PLys@PDA-Fe@PLCL conduit presents a promising strategy for advancing peripheral nerve repair.

Liquid Metal-Based Conductive Nerve Guidance Conduit Combined With Electrical Stimulation Boosts Peripheral Nerve Repair

The combination of nerve guide conduits (NGCs) and electrical stimulation (ES) is an effective treatment for peripheral nerve injury (PNI). Flexible conductive materials with mechanical properties similar to those of biological tissues have been shown to have better long-term biointegration and functionality than rigid conductive materials. In this study, liquid metal (LM)-based conductive polycaprolactone/gelatin/polypyrrole/LM (PCL/Gel/PPy/LM, PGPL) NGC was combined with exogenous ES to repair PNI. PGPL membranes had good hydrophilicity, degradability, and mechanical properties, and its conductivity reached 0.66 ± 0.02 S/m. In vitro studies showed that the combination of PGPL membranes and ES (2 Hz, 100 mV/cm, 30 min/d) could significantly increase the expression of neuromarkers and had a better pro-neural differentiation effect. In vivo studies demonstrated that PGPL NGCs in combination with ES (2 Hz, 200 mV/mm, 30 min/d) could effectively promote morphological reconstruction and functional recovery of the sciatic nerve in rats. At 3 months post-surgery, PGPL NGCs combined with ES restored the nerve conduction velocity to 73.85% ± 5.45% of the normal value. The LM-based NGCs prepared in this study could effectively repair long sciatic nerve defects, which may further expand the application of LM in the field of nerve tissue engineering.

Advanced Immunomodulatory Biomaterials for Therapeutic Applications

The multifaceted biological defense system modulating complex immune responses against pathogens and foreign materials plays a critical role in tissue homeostasis and disease progression. Recently developed biomaterials that can specifically regulate immune responses, nanoparticles, graphene, and functional hydrogels have contributed to the advancement of tissue engineering as well as disease treatment. The interaction between innate and adaptive immunity, collectively determining immune responses, can be regulated by mechanobiological recognition and adaptation of immune cells to the extracellular microenvironment. Therefore, applying immunomodulation to tissue regeneration and cancer therapy involves manipulating the properties of biomaterials by tailoring their composition in the context of the immune system. This review provides a comprehensive overview of how the physicochemical attributes of biomaterials determine immune responses, focusing on the physical properties that influence innate and adaptive immunity. This review also underscores the critical aspect of biomaterial-based immune engineering for the development of novel therapeutics and emphasizes the importance of understanding the biomaterials-mediated immunological mechanisms and their role in modulating the immune system.

From innovation to clinic: Emerging strategies harnessing electrically conductive polymers to enhance electrically stimulated peripheral nerve repair

Peripheral nerve repair (PNR) is a major healthcare challenge due to the limited regenerative capacity of the nervous system, often leading to severe functional impairments. While nerve autografts are the gold standard, their implications are constrained by issues such as donor site morbidity and limited availability, necessitating innovative alternatives like nerve guidance conduits (NGCs). However, the inherently slow nerve growth rate (∼1 mm/day) and prolonged neuroinflammation, delay recovery even with the use of passive (no-conductive) NGCs, resulting in muscle atrophy and loss of locomotor function. Electrical stimulation (ES) has the ability to enhance nerve regeneration rate by modulating the innate bioelectrical microenvironment of nerve tissue while simultaneously fostering a reparative environment through immunoregulation. In this context, electrically conductive polymer (ECP)-based biomaterials offer unique advantages for nerve repair combining their flexibility, akin to traditional plastics, and mixed ionic-electronic conductivity, similar to ionically conductive nerve tissue, as well as their biocompatibility and ease of fabrication. This review focuses on the progress, challenges, and emerging techniques for integrating ECP based NGCs with ES for functional nerve regeneration. It critically evaluates the various approaches using ECP based scaffolds, identifying gaps that have hindered clinical translation. Key challenges discussed include designing effective 3D NGCs with high electroactivity, optimizing ES modules, and better understanding of immunoregulation during nerve repair. The review also explores innovative strategies in material development and wireless, self-powered ES methods. Furthermore, it emphasizes the need for non-invasive ES delivery methods combined with hybrid ECP based neural scaffolds, highlighting future directions for advancing preclinical and clinical translation. Together, ECP based NGCs combined with ES represent a promising avenue for advancing PNR and improving patient outcomes.

Peripheral nerve regeneration using a bioresorbable silk fibroin-based artificial nerve conduit fabricated via a novel freeze-thaw process

While silk fibroin (SF) obtained from silkworm cocoons is expected to become a next-generation natural polymer, a fabrication method for SF-based artificial nerve conduits (SFCs) has not yet been established. Here, we report a bioresorbable SFC, fabricated using a novel freeze-thaw process, which ensures biosafety by avoiding any harmful chemical additives. The SFC demonstrated favorable biocompatibility (high hydrophilicity and porosity with a water content of > 90%), structural stability (stiffness, toughness, and elasticity), and biodegradability, making it an ideal candidate for nerve regeneration. We evaluated the nerve-regenerative effects of the SFC in a rat sciatic-nerve-defect model, including its motor and sensory function recovery as well as histological regeneration. We found that SFC transplantation significantly promoted functional recovery and nerve regeneration compared to silicone tubes and was almost equally effective as autologous nerve transplantation. Histological analyses indicated that vascularization and M2 macrophage recruitment were pronounced inside the SFC. These results suggest that the unique properties of the SFC further enhanced the peripheral nerve regeneration mechanism. As no SFC has been applied in clinical practice, the SFC reported herein may be a promising candidate for repairing extensive peripheral nerve defects.

Programmable DNA‐Peptide Conjugated Hydrogel via Click Chemistry for Sequential Modulation of Peripheral Nerve Regeneration

During peripheral nerve regeneration, current deoxyribonucleic acid (DNA)‐based therapeutic platforms face the challenge of precisely regulating Schwann cells (SCs) fate to sustain their repair phenotype due to their inability to stably and precisely integrate multiple bioactive components. Herein, the strain‐promoted azide–alkyne cycloaddition reaction is utilized to integrate the neurotrophic factor mimetic peptide RGI and the laminin‐derived peptide IKVAV into DNA monomers. Through DNA sequence self‐assembly, a programmable DNA‐peptide conjugated hydrogel is constructed for loading bone marrow mesenchymal stem cell‐derived exosomes. This programmable hydrogel can rapidly, stably, and precisely integrate various bioactive components into the hydrogel network, thereby enabling sequential modulation of peripheral nerve repair. In vitro, studies show that this hydrogel, through sequential modulation mechanisms, can activate the neuregulin‐1 (Nrg1)/ErbB pathway to induce the reprogramming of SCs and promote the recruitment and proliferation of repair SCs. The induced repair SCs promote neuronal axon outgrowth and enhance tube formation in endothelial cells. In vivo, this programmable hydrogel can gelate in situ through intraneural injection in a rat sciatic nerve crush injury model, promoting nerve regeneration and functional recovery. In summary, this work provides an effective and practical strategy for peripheral nerve regeneration.

Stem Cell-Laden Engineered Patch: Advances and Applications in Tissue Regeneration

Stem cell-based therapies are emerging as significant approaches in tissue engineering and regenerative medicine, applicable to both fundamental scientific research and clinical practice. Despite remarkable results in clinical studies, challenges such as poor standardization of graft tissues, limited sources, and reduced functionality have hindered the effectiveness of these therapies. In this review, we summarize the engineering approaches involved in fabricating stem cell assisted patches and the substantial strategies for designing stem cell-laden engineered patches (SCP) to complement the existing stem cell-based therapies. We then outline the potential applications of SCP in advancing tissue regeneration and regenerative medicine. By combining living stem cells with engineered patches, SCP can enhance the functions of both components, particularly for tissue engineering applications. Finally, we addressed current challenges, such as ethical considerations, high costs, and regulatory hurdles and proposed future research directions to overcome these barriers.

Nerve repair with polylactic acid and inosine treatment enhance regeneration and improve functional recovery after sciatic nerve transection

Background

Following transection, nerve repair using the polylactic acid (PLA) conduit is an effective option. In addition, inosine treatment has shown potential to promote nerve regeneration. Therefore, this study aimed to investigate the regenerative potential of inosine after nerve transection and polylactic acid conduit repair.

Methods

C57/Black6 mice were subjected to sciatic nerve transection, repair with PLA conduit, and intraperitoneal injection of saline or inosine 1 h after injury and daily for 1 week. To assess motor and sensory recovery, functional tests were performed before and weekly up to 8 weeks after injury. Following, to evaluate the promotion of regeneration and myelination, electroneuromyography, morphometric analysis and immunohistochemistry were then performed.

Results

Our results showed that the inosine group had a greater number of myelinated nerve fibers (1,293 ± 85.49 vs. 817 ± 89.2), an increase in neurofilament high chain (NFH) and myelin basic protein (MBP) immunolabeling and a greater number of fibers within the ideal g-ratio (453.8 ± 45.24 vs. 336.6 ± 37.01). In addition, the inosine group presented a greater adenosine A2 receptor (A2AR) immunolabeling area. This resulted in greater compound muscle action potential amplitude and nerve conduction velocity, leading to preservation of muscle and neuromuscular junction integrity, and consequently, the recovery of motor and sensory function.

Conclusion

Our findings suggest that inosine may enhance regeneration and improve both motor and sensory function recovery after nerve transection when repaired with a poly-lactic acid conduit. This advances the understanding of biomaterials and molecular treatments.

Mesoporous Prussian blue nanoparticle neuroconduit for the biological therapy targeting oxidative stress reduction, inflammation inhibition, and nerve regeneration

The applications of nanomaterials in regenerative medicine encompass a broad spectrum. The functional nanomaterials, such as Prussian blue and its derivative nanoparticles, exhibit potent anti-inflammatory and antioxidant properties. By combining it with the corresponding scaffold carrier, the fusion of nanomaterials and biotherapy can be achieved, thereby providing a potential avenue for clinical treatment. The present study demonstrates the fabrication of a Mesoporous Prussian blue nanoparticles (MPBN) functionalized Inverse Opal Film (IOF) neuroconduit for peripheral nerve repair through reverse replication and freeze-drying techniques. The binding of MPBN to the neuroconduit can effectively decreasing reactive oxygen species and inflammatory factors in the vicinity of the residual nerve, thereby providing protective effects on the damaged nerve. Furthermore, comprehensive behavioral, electrophysiological, and pathological analyses unequivocally substantiate the efficacy of MPBN in increasing nerve structure regeneration and ameliorating denervation-induced myopathy. Moreover, MPBN enhances the antioxidant capacity of Schwann cells by activating the AMPK/SIRT1/PGC-1 pathway. The findings suggest that MPBN, a biocompatible nanoparticle, can safeguard damaged nerves by optimizing the microenvironment surrounding nerve cells and augmenting the antioxidant capacity of nerve cells, thereby facilitating nerve regeneration and repair. This also establishes a theoretical foundation for exploring the integration and clinical translation between nanomaterials and biotherapy.

Piezoelectric bilayer fibrous conduit with gellan/curcumin encapsulated alginate infilling for promotion of sciatic nerve regeneration in the rat models

The peripheral nerve regeneration has a limited innate capacity for self-repair and thus it urgently necessitates designing a smart nerve guidance conduit. Considering the electrophysiological features of nerve tissues, a piezoelectric bilayer fibrous conduit filled with drug-encapsulated gellan was developed in this study and its ability to promote neural growth was assessed in vivo. To fabricate such conduit, bilayer fibrous mats were prepared from poly ε-caprolactone/BaTiO3 and poly-L-lactic acid -chitosan-gelatin-polyaniline/graphene via an electrospinning process. After rolling the fibrous mat, the inside of the hollow conduit was filled with gellan containing Curcumin-loaded alginate (Alg) particles. All intermediate and final products were characterized using various analytical techniques. Encapsulation of Curcumin into the Alg particles and loaded in the gellan could effectively enhance sustained release of drug during the healing process, following Higuchi model. Four weeks post-surgery, such an engineered conduit revealed much better nerve regeneration results than the control group and showed desirable outcomes in terms of sciatic function indices and formation of the perineurium as well as axon number. Such developed conduit has a high potency to repair the injured nerve tissue due to their capacity to sustain the release of drugs over a long period and transfer self-stimulated electrical signals between cells. The in vivo assay revealed the feasibility of exploiting such conduit in nerve tissue engineering.

Treatment for peripheral nerve injury: a protocol for a systematic review and Bayesian network meta-analysis

INTRODUCTION

Available therapies for peripheral nerve injury (PNI) include surgical and non-surgical treatments. Surgical treatment includes neurorrhaphy, grafting (allografts and autografts) and tissue-engineered grafting (artificial nerve guide conduits), while non-surgical treatment methods include electrical stimulation, magnetic stimulation, laser phototherapy and administration of nerve growth factors. However, the treatments currently available to best manage the different PNI manifestations remain undetermined. This systematic review and network meta-analysis (NMA) aims to address this and determine the best treatment or combination of treatments for PNI.

METHODS AND ANALYSIS

A comprehensive search of MEDLINE (via PubMed), Embase, Cochrane Library, Web of Science, Chinese Biomedical Database, China National Knowledge Infrastructure, VIP Database, Wanfang Database, WHO International Clinical Trials Registry Platform, ClinicalTrials.gov and the Chinese Clinical Trial Register will be completed using the following keywords: peripheral nerve injury, therapies and related entry terms. Studies will be included based on specific eligibility criteria, and the reference lists of the included studies will be manually searched. Relevant data will be extracted from the included studies using a specially designed data extraction sheet. The risk of bias in the included studies will be assessed, and the overall strength of the evidence will be summarised. A random-effects model was used for all pairwise meta-analyses (95% CI). Bayesian NMA is used to explore the relative benefits of various treatments. The review will be reported using the Preferred Reporting Items for Systematic Reviews incorporating NMA statement.

ETHICS AND DISSEMINATION

As the protocol for this systematic review and Bayesian NMA is based on studies with published results and does not involve patient interventions, no ethical review is required. The results will be published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42023475135.

Synergic effects of core-shell nanospheres and magnetic field for sciatic nerve regeneration in decellularized artery conduits with Schwann cells

Numerous conduits have been developed to improve peripheral nerve regeneration. However, challenges remain, including remote control of conduit function, and programmed cell behaviors like orientation. We synthesized Fe3O4-MnO2@Zirconium-based Metal-organic frameworks@Retinoic acid (FMZMR) core-shell and assessed their impact on Schwann cell function and behavior within conduits made from decellularized human umbilical arteries (DHUCA) under magnetic field (MF). FMZMR core-shell, featuring a spherical porous structure and catalytic properties, effectively scavenges radicals and facilitates controlled drug release under MF. The histology of the DHUCA indicates effective decellularization with adequate tensile strength and Young's modulus for sciatic nerve regeneration. In-vitro results demonstrate that FMZMR core-shell is biocompatible and promotes Schwann cell proliferation through remotely controlled drug release. Furthermore, its synergy with MF enhances cell orientation and increases neurite length by ~ 1.93-fold. Functional and histological evaluations indicate that the FMZMR core-shell combined with MF promotes nerve regeneration, decreases muscle atrophy, and enhances new neuron growth and myelin formation, without negatively affecting vital tissues. This study suggests that the synergistic effect of FMZMR core-shell with MF can alleviate some of the treatment challenges.

The limelight of adipose-derived stem cells in the landscape of neural tissue engineering for peripheral nerve injury

BACKGROUND AND AIMS

Challenges in treating peripheral nerve injury include prolonged repair time and insufficient functional recovery. Stem cell therapy coupled with neural tissue engineering has been shown to induce nerve regeneration following peripheral nerve injury. Among these stem cells, adipose-derived stem cells (ADSCs) are preferred due to their accessibility, expansion, multidirectional differentiation, and production of essential nutrient factors for nerve growth. In recent years, ADSC-laden nerve guide conduit has been utilized to enhance the therapeutic effects of tissue-engineered nerve grafts. This review explores existing research that recognizes the roles played by ADSCs in inducing peripheral nerve regeneration following injury and summarizes the different methods of application of ADSC-laden nerve conduit in neural tissue engineering.

Decellularized Biohybrid Nerve Promotes Motor Axon Projections

Developing nerve grafts with intact mesostructures, superior conductivity, minimal immunogenicity, and improved tissue integration is essential for the treatment and restoration of neurological dysfunctions. A key factor is promoting directed axon growth into the grafts. To achieve this, biohybrid nerves are developed using decellularized rat sciatic nerve modified by in situ polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). Nine biohybrid nerves are compared with varying polymerization conditions and cycles, selecting the best candidate through material characterization. These results show that a 1:1 ratio of FeCl3 oxidant to ethylenedioxythiophene (EDOT) monomer, cycled twice, provides superior conductivity (>0.2 mS cm-1), mechanical alignment, intact mesostructures, and high compatibility with cells and blood. To test the biohybrid nerve's effectiveness in promoting motor axon growth, human Spinal Cord Spheroids (hSCSs) derived from HUES 3 Hb9:GFP cells are used, with motor axons labeled with green fluorescent protein (GFP). Seeding hSCS onto one end of the conduit allows motor axon outgrowth into the biohybrid nerve. The construct effectively promotes directed motor axon growth, which improves significantly after seeding the grafts with Schwann cells. This study presents a promising approach for reconstructing axonal tracts in humans.

Schwann cell autotransplantation for the treatment of peripheral nerve injury

Peripheral nerve injury occurs in a relatively large proportion of trauma patients, in whom it generally results in severe functional impairment and permanent disability. At present, however, there are no effective treatments available. Studies have shown that Schwann cells play an indispensable role in removing myelin debris and guiding axonal regeneration, and transplantation using autologous Schwann cells has shown good efficacy for patients with peripheral nerve injury. In recent years, Schwann cell autologous transplantation therapy has become an area of intensive research and is anticipated to provide a new strategy for the clinical treatment of peripheral nerve injury. In this article, we review the rationale for selecting Schwann cell autotransplantation therapy and the latest progress in key aspects of cell transplantation and clinical efficacy, and also summarize the future directions of research on this therapy. All of the above provide a strong basis for the further improvement and clinical promotion of this therapy.

Platelet-rich plasma (PRP) in nerve repair

Platelet-rich plasma (PRP) has the capability of assisting in the recovery of damaged tissues by releasing a variety of biologically active factors to initiate a hemostatic cascade reaction and promote the synthesis of new connective tissue and revascularization. It is now widely used for tissue engineering repair. In addition, PRP has demonstrated nerve repair and pain relief, and has been studied and applied to the facial nerve, median nerve, sciatic nerve, and central nerve. These suggest that PRP injection therapy has a positive effect on nerve repair. This indicates that PRP has high clinical value and potential application in nerve repair. It is worthwhile for scientists and medical workers to further explore and study PRP to expand its application in nerve repair, and to provide a more reliable scientific basis for the opening of a new approach to nerve repair.

Insights into Advances and Applications of Biomaterials for Nerve Tissue Injuries and Neurodegenerative Disorders

The incidence of nerve tissue injuries, such as peripheral nerve injury, spinal cord injury, traumatic brain injury, and various neurodegenerative diseases (NDs), is continuously increasing because of stress, physical and chemical trauma, and the aging population worldwide. Restoration of the damaged nervous system is challenging because of its structural and functional complexity and limited regenerative ability. Additionally, there is no cure available for NDs except for medications that provide symptomatic relief. Stem cells offer an alternative approach for promoting damage repair, but their efficacy is limited by a compromised survival rate and neurogenesis process. To address these challenges, neural tissue engineering has emerged as a promising strategy in which stem cells are seeded or encapsulated within a suitable biomaterial construct, increasing cell survival and neurogenesis. Numerous biomaterials are utilized to create different types of constructs for this purpose. Researchers are trying to develop ideal scaffolds that combine biomaterials, cells, and molecules that exactly mimic the biological and mechanical properties of the tissue to achieve functional recovery associated with neurological dysfunction. This review focuses on exploring the development and applications of different biomaterials for their potential use in the diagnosis, therapy, nerve tissue regeneration, and treatment of neurological disorders.

Rapid Forming, Robust Adhesive Fungal-Sourced Chitosan Hydrogels Loaded with Deferoxamine for Sutureless Short-Gap Peripheral Nerve Repair

Clinically, conventional sutures for repair of short-distance nerve injuries (< 5 mm) may contribute to uncontrolled inflammation and scar formation, thus negatively impacting nerve regeneration. To repair transected peripheral nerves with short distances, a rapid-forming, robust adhesive chitosan hydrogel is prepared by synthesizing maleic and dopamine bi-functionalized fungal-sourced chitosan (DM) and subsequently photopolymerizing DM precursor solution. The hydrogel rapidly polymerized under UV light irradiation (≈2 s) and possessed a strong adhesive strength (273.33 ± 55.07 kPa), facilitating a fast bonding of nerve stump. Especially, its tailored degradation profile over 28 days supported both early gap bridging and subsequent nerve regeneration. Furthermore, deferoxamine (DFO), a pro-angiogenic drug, is loaded into the hydrogel to reach sustainable release, accelerating axonal growth synergistically. A 3 mm long sciatic nerve defects model in rats is used to investigate the efficacy of DM@DFO hydrogel for repairing peripheral nerve defects. After 60 days, the DM@DFO hydrogel significantly outperformed conventional sutures and fibrin glue, improving motor and sensory recovery by reducing inflammation, inhibiting scar formation, and accelerating vascular regeneration within 14 days post-repair. This work highlights the DM@DFO hydrogel as a promising tissue adhesive for effective short-distance peripheral nerve repair.

In Vitro Models for Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) resulting in lesions is highly prevalent clinically, but current therapeutic approaches fail to provide satisfactory outcomes in many patients. While peripheral nerves have intrinsic regenerative capacity, the regenerative capabilities of peripheral nerves are often insufficient to restore full functionality. This highlights an unmet need for developing more effective strategies to repair damaged peripheral nerves and improve regenerative success. Consequently, researchers are actively exploring a variety of therapeutic strategies, encompassing the local delivery of trophic factors or bioactive molecules, the design of advanced biomaterials that interact with regenerating axons, and augmentation with nerve guidance conduits or complex prostheses. However, clinical translation of these technologies remains limited, emphasizing the need for continued research on peripheral nerve regeneration modalities that can enhance functional restoration. Experimental models that accurately recapitulate key aspects of peripheral nerve injury and repair biology can accelerate therapeutic development by enabling systematic testing of new techniques. Advancing regenerative therapies for PNI requires bridging the gap between basic science discoveries and clinical application. This review discusses different in vitro models of peripheral nerve injury and repair, including their advantages, limitations, and potential applications.

Design and In Vivo Testing of an Anatomic 3D-Printed Peripheral Nerve Conduit in a Rat Sciatic Nerve Model

Background: Three-dimensional (3D) printer technology has seen a surge in use in medicine, particularly in orthopedics. A recent area of research is its use in peripheral nerve repair, which often requires a graft or conduit to bridge segmental defects. Currently, nerve gaps are bridged using autografts, allografts, or synthetic conduits. Purpose: We sought to improve upon the current design of simple hollow, cylindrical conduits that often result in poor nerve regeneration. Previous attempts were made at reducing axonal dispersion with the use of multichanneled conduits. To our knowledge, none has attempted to mimic and test the anatomical topography of the nerve. Methods: Using serial histology sections, 3D reconstruction software, and computer-aided design, a scaffold was created based on the fascicular topography of a rat sciatic nerve. A 3D printer produced both cylindrical conduits and topography-based scaffolds. These were implanted in 12 Lewis rats: 6 rats with the topographical scaffold and 6 rats with the cylindrical conduit. Each rodent's uninjured contralateral limb was used as a control for comparison of functional and histologic outcomes. Walking track analysis was performed, and the Sciatic Functional Index (SFI) was calculated with the Image J software. After 6 weeks, rats were sacrificed and analyses performed on the regenerated nerve tissue. Primary outcomes measured included nerve (fiber) density, nerve fiber width, total number of nerve fibers, G-ratio (ratio of axon width to total fiber width), and percent debris. Secondary outcomes measured included electrophysiology studies of electromyography (EMG) latency and EMG amplitude and isometric force output by the gastrocnemius and tibialis anterior. Results: There were no differences observed between the cylindrical conduit and topographical scaffold in terms of histological outcomes, muscle force, EMG, or SFI. Conclusion: This study of regeneration of the sciatic nerve in a rat model suggests the feasibility of 3D-printed topographical scaffolds. More research is required to quantify the functional outcomes of this technology for peripheral nerve regeneration.

Nerve guide conduits promote nerve regeneration under a combination of electrical stimulation and RSCs combined with stem cell differentiation

Nerve guide conduits (NGCs) offer a promising alternative to traditional tools for regenerating peripheral nerves. The efficacy of nerve regeneration and functional recovery is heavily dependent on the electrical, chemical, and physical properties of NGCs. A bionic melt electrowriting (MEW) NGC loaded with placental derived mesenchymal stem cells (PDMSCs) has been developed. Our study introduces a novel approach by utilizing Schwann cells induced from placental mesenchymal stem cells (PDMSCs), showcasing their potential in enhancing nerve regeneration when integrated with conductive nerve guidance conduits. Schwann cells (SCs) are crucial for nerve regeneration, and while various stem cells, including bone marrow stromal cells (BMSCs), have been investigated as sources of SCs for NGC loading, they are often limited by ethical concerns and restricted availability. PDMSCs, however, offer the advantages of widespread sourcing and unique ability to differentiate into SCs, making them an attractive alternative for NGC applications. This NGC utilizes an electrostatic direct writing technique employing polycaprolactone (PCL) for the sheath and a crimped fiber scaffold made of polypyrrole (PPY) incorporated with PDMSCs for its internal structure. The bionic PC-NGC loaded with PDMSCs exhibits favorable characteristics including permeability, mechanical stability, and electrical conductivity. The PPY component effectively transmits physiological nerve signals, thereby promoting nerve regeneration, while the PDMSCs differentiate into Schwann cells, creating a conducive environment for nerve regeneration. This research innovatively combines PDMSCs, known for their wide availability and SC differentiation potential, with a bionic NGC to enhance the treatment of peripheral nerve injuries (PNIs). In vitro evaluations have confirmed the excellent biocompatibility of the materials used. Animal experiments using a rat model with sciatic nerve injury demonstrated that the PC-NGC significently facilitated peripheral nerve regeneration. This was evidenced by improvements in axonal myelination, increased muscle mass, enhanced sciatic nerve function index, and positive electrophysiological findings. These outcomes are comparable to those achieved through autologous transplantation. Characterized by its layered oriented fibers, the bionic PC-NGC integrates multi-scale and multifunctional biomaterials with PDMSCs to effectively address peripheral nerve injuries (PNIs). The use of this printed NGC stimulates neuronal cell growth, thereby accelerating nerve regeneration. This innovative approach in tissue engineering presents a promising clinical treatment strategy for PNIs.

Effect of sodium L-lactate on bioactive properties of chitosan-hydroxyapatite/polycaprolactone conduits for peripheral nerve tissue engineering

Biomaterials and synthetic polymers have been widely used to replicate the regenerative microenvironment of the peripheral nervous system. Chitosan-based conduits have shown promise in the regeneration of nerve injuries. However, to mimic the regenerative microenvironment, the scaffold structure should possess bioactive properties. This can be achieved by the incorporation of biomolecules (e.g., proteins, peptides) or trophic factors that should preferably be aligned and/or released with controlled kinetics to activate the process of positive axon chemotaxis. In this study, sodium L-lactate has been used to enhance the bioactive properties of chitosan-hydroxyapatite/polycaprolactone electrodeposits. Next, two methods have been developed to incorporate NGF-loaded microspheres - Method 1 involves entrapment and co-deposition of NGF-loaded microspheres, while Method 2 is based on absorption of NGF-loaded microspheres. The study shows that modification of chitosan-hydroxyapatite/polycaprolactone conduits by sodium L-lactate significantly improves their bioactive, biological, and physicochemical properties. The obtained implants are cytocompatible, enhancing the neurite regeneration process by stimulating its elongation. The absorption of NGF-loaded microspheres into the conduit structure may be considered more favorable for the stimulation of axonal elongation compared to entrapment, as it allows for trophic factor dose-dependent controlled release. The developed conduits possess properties essential for the successful treatment of peripheral nerve discontinuities.

Influencing factors and repair advancements in rodent models of peripheral nerve regeneration

Peripheral nerve injuries lead to severe functional impairments, with rodent models essential for studying regeneration. This review examines key factors affecting outcomes. Age-related declines, like reduced nerve fiber density and impaired axonal transport of vesicles, hinder recovery. Hormonal differences influence regeneration, with BDNF/trkB critical for testosterone and nerve growth factor for estrogen signaling pathways. Species and strain selection impact outcomes, with C57BL/6 mice and Sprague-Dawley rats exhibiting varying regenerative capacities. Injury models - crush for early regeneration, chronic constriction for neuropathic pain, stretch for traumatic elongation and transection for severe lacerations - provide insights into clinically relevant scenarios. Repair techniques, such as nerve grafts and conduits, show that autografts are the gold standard for gaps over 3 cm, with success influenced by graft type and diameter. Time course analysis highlights crucial early degeneration and regeneration phases within the first month, with functional recovery stabilizing by three to six months. Early intervention optimizes regeneration by reducing scar tissue formation, while later interventions focus on remyelination. Understanding these factors is vital for designing robust preclinical studies and translating research into effective clinical treatments for peripheral nerve injuries.

Chiral Hydrogel Nerve Conduit Boosts Peripheral Nerve Regeneration via Regulation of Schwann Cell Reprogramming

The Schwann cell (SC) is essential in peripheral nerve regeneration by reprogramming into a stem-like "repair Schwann cell" (rSC) phenotype; however, maintaining the rSC stemness remains an unmet challenge. Chirality is a fundamental factor controlling cell fate, and its potential role in regulation of SC reprogramming has long been ignored and remains poorly understood. Herein, inspired by natural chiral components in the SC microenvironment, chiral hydrogel nerve conduits are prepared by supramolecular assembly of l/d-phenylalanine derivatives (l/d-Phe) in polymeric chitosan-gelatin conduits. Right-handed l-Phe fibers within hydrogel conduits maintain the stemness of rSC through enhanced stereoselective interaction between collagen IV and l-Phe fibers triggered by collagen IV-Integrin α1β1, MAPK, and YAP/TAZ signaling pathways and finally activate the key regulator of SC reprogramming, the c-Jun pathway. In the rat model of a sciatic nerve defect, the l-Phe hydrogel nerve conduit significantly enhances nerve regeneration, exhibiting markedly improved histological, electrophysiological, and functional outcomes. The findings reveal the chirality-dependent regulation of SC reprogramming in a pioneering way, offering potential strategies for nerve regeneration therapies.

Reconstruction of the Infraorbital Nerve Using Bilayered Artificial Nerve Conduits after Partial Maxillectomy

Background

Facial sensory nerves play vital roles in daily functions like self-protection, facial expressions, speaking, and eating. Severing the infraorbital nerve (ION) during partial maxillectomy via the Weber-Ferguson incision can lead to sensory disturbances. This study presents immediate ION reconstruction using artificial nerve conduits and its short-term outcomes.

Methods

This retrospective study included three patients (mean age: 67.0 years) undergoing immediate ION reconstruction after partial maxillectomy via the Weber-Ferguson incision. Sensory recovery was evaluated using the Semmes-Weinstein and two-point discrimination (2PD) tests. A reference group of five patients who underwent total maxillectomy without ION reconstruction was also assessed.

Results

No postoperative complications were observed during the 15.3-month follow-up. Sensory recovery varied among patients, with one achieving normal perception at 24 months, another showing diminished light touch at 13 months, and the third experiencing diminished protective sensation at 7 months postoperatively. In comparison, the reference group showed lower sensory recovery. Two patients showed improvements in 2PD test results at 24 and 13 months, whereas one showed no recovery at 7 months. No patients in the reference group showed improvement.

Conclusion

Immediate ION reconstruction using artificial nerve conduits after partial maxillectomy appears feasible, as evidenced by acceptable sensory recovery in the short term.

Flexible multimaterial fibers in modern biomedical applications

Biomedical devices are indispensable in modern healthcare, significantly enhancing patients' quality of life. Recently, there has been a drastic increase in innovations for the fabrication of biomedical devices. Amongst these fabrication methods, the thermal drawing process has emerged as a versatile and scalable process for the development of advanced biomedical devices. By thermally drawing a macroscopic preform, which is meticulously designed and integrated with functional materials, hundreds of meters of multifunctional fibers are produced. These scalable flexible multifunctional fibers are embedded with functionalities such as electrochemical sensing, drug delivery, light delivery, temperature sensing, chemical sensing, pressure sensing, etc. In this review, we summarize the fabrication method of thermally drawn multifunctional fibers and highlight recent developments in thermally drawn fibers for modern biomedical application, including neural interfacing, chemical sensing, tissue engineering, cancer treatment, soft robotics and smart wearables. Finally, we discuss the existing challenges and future directions of this rapidly growing field.

Characterization of lncRNA and mRNA profiles in the process of repairing peripheral nerve defects with cell-matrixed nerve grafts

BACKGROUND

Decellularized extracellular matrix (dECM) is an intriguing natural biomaterial that has garnered significant attention due to its remarkable biological properties. In our study, we employed a cell-matrixed nerve graft for the repair of sciatic nerve defects in rats. The efficacy of this approach was assessed, and concurrently, the underlying molecular regulatory mechanisms were explored to elucidate how such grafts facilitate nerve regeneration. Long noncoding RNAs (lncRNAs) regulate mRNA expression via multiple mechanisms, including post-transcriptional regulation, transcription factor effects, and competitive binding with miRNAs. These interactions between lncRNAs and mRNAs facilitate precise control of gene expression, allowing organisms to adapt to varying biological environments and physiological states. By investigating the expression profiles and interaction dynamics of mRNAs and lncRNAs, we can enhance our understanding of the molecular mechanisms through which cell-matrixed nerve grafts influence neural repair. Such studies are pivotal in uncovering the intricate networks of gene regulation that underpin this process.

RESULTS

Weighted gene co-expression network analysis (WGCNA) utilizes clustering algorithms, such as hierarchical clustering, to aggregate genes with similar expression profiles into modules. These modules, which potentially correspond to distinct biological functions or processes, can subsequently be analyzed for their association with external sample traits. By correlating gene modules with specific conditions, such as disease states or responses to treatments, WGCNA enables a deeper understanding of the genetic architecture underlying various phenotypic traits and their functional implications. We identified seven mRNA modules and five lncRNA modules that exhibited associations with treatment or time-related events by WGCNA. We found the blue (mRNAs) module which displayed a remarkable enrichment in "axonal guidance" and "metabolic pathways", exhibited strong co-expression with multiple lncRNA modules, including blue (related to "GnRH secretion" and "pyrimidine metabolism"), green (related to "arginine and proline metabolism"), black (related to "nitrogen metabolism"), grey60 (related to "PPAR signaling pathway"), and greenyellow (related to "steroid hormone biosynthesis"). All of the top 50 mRNAs and lncRNAs exhibiting the strongest correlation were derived from the blue module. Validation of key molecules were performed using immunohistochemistry and qRT-PCR.

CONCLUSION

Revealing the principles and molecular regulatory mechanisms of the interaction between materials and biological entities, such as cells and tissues, is a direction for the development of biomimetic tissue engineering technologies and clinically effective products.