A Bioresorbable and Conductive Scaffold Integrating Silicon Membranes for Peripheral Nerve Regeneration

Biomimetic ECM nerve guidance conduit with dynamic 3D interconnected porous network and sustained IGF-1 delivery for enhanced peripheral nerve regeneration and immune modulation

Recent advancements in tissue engineering have promoted the development of nerve guidance conduits (NGCs) that significantly enhance peripheral nerve injury treatment, improving outcomes and recovery rates. However, utilising tailored biomimetic three-dimensional (3D) topological porous structures combined with multiple bio-effect neurotrophic factors to create environments similar to neural tissues, regulate local immune responses, and develop a supportive microenvironment to promote peripheral nerve regeneration and repair poses significant challenges. Herein, a biomimetic extracellular matrix (ECM) NGC featuring an interconnected 3D porous network and sustained delivery of insulin-like growth factor-1 (IGF-1) is designed using multi-functional gelatine microcapsules (GMs). Nerve conduits made by blending chitosan (CS) with GMs demonstrate suitable degradation rates, reduced swelling rates, increased suture tensile strength, improved elongation at break, and 50 % radial compression performance that meet clinical application requirements. In vitro cytological studies indicate that biomimetic ECM NGCs exhibit good biocompatibility, promote early survival, proliferation, and remyelination potential of Schwann cells (SCs), and support neurite outgrowth. The biomimetic ECM NGCs comprising a 3D interconnected porous network in a 10-mm sciatic nerve defect rat model sustain IGF-1 delivery, promoting early infiltration of macrophages and polarisation towards M2-type macrophages. Furthermore, observations at 12 weeks post-implantation revealed improvements in electrophysiological performance, alleviation of gastrocnemius muscle atrophy, increased peripheral nerve regeneration, and motor function restoration. Thus, biomimetic ECM NGCs offer a therapeutic strategy for peripheral nerve regeneration with promising clinical applications and transformation prospects to regulate immune microenvironments, promoting SC proliferation and differentiation with nerve axon growth.

Application of olfactory ensheathing cells in peripheral nerve injury and its complication with pathological pain

Direct or indirect injury of peripheral nerve can lead to sensory and motor dysfunction, which can lead to pathological pain and seriously affect the quality of life and psychosomatic health of patients. While the internal repair function of the body after peripheral nerve injury is limited. Nerve regeneration is the key factor hindering the recovery of nerve function. At present, there is no effective treatment. Therefore, more and more attention have been paid to the development of foreground treatment to achieve functional recovery after peripheral nerve injury, including relief of pathological pain. Cell transplantation strategy is a therapeutic method with development potential in recent years, which can exert endogenous alternative repair by transplanting exogenous functional bioactive cells to the site of nerve injury. Olfactory ensheathing cells (OECs) are a special kind of glial cells, which have the characteristics of continuous renewal and survival. The mechanisms of promoting nerve regeneration and functional repair and relieving pathological pain by transplantation of OECs to peripheral nerve injury include secretion of a variety of neurotrophic factors, axonal regeneration and myelination, immune regulation, anti-inflammation, neuroprotection, promotion of vascular growth and improvement of inflammatory microenvironment around nerve injury. Different studies have shown that OECs combined with biomaterials have made some progress in the treatment of peripheral nerve injury and pathological pain. These biomaterials enhance the therapeutic effect of OECs. Therefore, the functional role of OECs in peripheral nerve injury and pathological pain was discussed in this paper.Although OECs are in the primary stage of exploration in the repair of peripheral nerve injury and the application of pain, but OECs transplantation may become a prospective therapeutic strategy for the treatment of peripheral nerve injury and pathological pain.

Electrical Stimulation: Enhancing Axonal Growth following Peripheral Nerve Injury

Electrical stimulation has been integrated in recent decades into rehabilitation protocols following neuromuscular injuries. Existing literature supports the utilisation of prolonged or continuous stimulation generated by implantable or transcutaneous devices for chronic pain subsidence and muscle trophism maintenance, which improve outcomes following microsurgical interventions. Newer uses include brief electrical stimulation for peripheral nerve injury. Brief electrical stimulation has shown promise in expediting regeneration of both torn and crushed nerve axons in the murine model and has been incorporated into a limited number of clinical studies. Augmentation of the natural response of an injured peripheral nerve by electrical stimulation has the potential to accelerate regeneration, presumably leading to improved function and clinical outcomes. We review the existing literature on intraoperative utilisation of electrical stimulation to enhance regeneration, such as neural mechanisms of action and their microscopic effect in animal models, as well as results from initial human studies. Level of Evidence: Level V (Therapeutic).

Silicon-induced biofilm improves peripheral nerve defect in rats mediated by VEGF/VEGFR2/ERK

Background: Injury of peripheral nerve capable of regeneration with much poorer prognosis affects people's life quality. The recovery of nerve function after transplantation for peripheral nerve injury remain a worldwide problem. Silicon-induced biofilms as vascularized biological conduits can promote nerve regeneration by encapsulating autologous or allogeneic nerve graft.Objective: We proposed to explore the effect of silicon-induced biofilms on nerves regeneration and whether the VEGF/VEGFR2/ERK pathway was involved in the present study.Methods: Biofilms around the transplanted nerves in peripheral nerve injury rats were induced by silicon. Vascularization and proteins related to VEGF/VEGFR2/ERK were measured. Pathology and morphology of nerves were investigated after encapsulating the transplanted nerves by silicon-induced biofilms.Results: Our results indicated that the biofilms induced by silicon for 6 weeks showed the most intensive vascularization and the optimal effect on nerve regeneration. Moreover, silicon-induced biofilms for 4, 6 and 8 weeks could significantly secrete VEGF with the highest content at week 6 after induction. VEGFR2, VEGF, p-VEGFR2, ERK1, ERK2, p-ERK1 and p-ERK2 were expressed in the biofilms. p-VEGFR2, p-ERK1 and p-ERK2 expression were different at each time point and significantly increased at week 6 compared with that at week 4 or week 8 which was consistent with that 6 week of was the optimum time for biofilms induction to improve the nerve repair after peripheral nerve injury.Conclusion: Our results suggested that combination of silicon-induced autologous vascularized biofilm and autologous transplantation may promote the repair of rat sciatic nerve defect quickly through VEGF/VEGFR2/ERK pathway.

Electrical stimulation enhances sciatic nerve regeneration using a silk-based conductive scaffold beyond traditional nerve guide conduits

Despite recent advancements in peripheral nerve regeneration, the creation of nerve conduits with chemical and physical cues to enhance glial cell function and support axonal growth remains challenging. This study aimed to assess the impact of electrical stimulation (ES) using a conductive nerve conduit on sciatic nerve regeneration in a rat model with transection injury. The study involved the fabrication of conductive nerve conduits using silk fibroin and Au nanoparticles (AuNPs). Collagen hydrogel loaded with green fluorescent protein (GFP)-positive adipose-derived mesenchymal stem cells (ADSCs) served as the filling for the conduit. Both conductive and non-conductive conduits were applied with and without ES in rat models. Locomotor recovery was assessed using walking track analysis. Histological evaluations were performed using H&E, luxol fast blue staining and immunohistochemistry. Moreover, TEM analysis was conducted to distinguish various ultrastructural aspects of sciatic tissue. In the ES + conductive conduit group, higher S100 (p < 0.0001) and neurofilament (p < 0.001) expression was seen after 6 weeks. Ultrastructural evaluations showed that conductive scaffolds with ES minimized Wallerian degeneration. Furthermore, the conductive conduit with ES group demonstrated significantly increased myelin sheet thickness and decreased G. ratio compared to the autograft. Immunofluorescent images confirmed the presence of GFP-positive ADSCs by the 6th week. Locomotor recovery assessments revealed improved function in the conductive conduit with ES group compared to the control group and groups without ES. These results show that a Silk/AuNPs conduit filled with ADSC-seeded collagen hydrogel can function as a nerve conduit, aiding in the restoration of substantial gaps in the sciatic nerve with ES. Histological and locomotor evaluations indicated that ES had a greater impact on functional recovery compared to using a conductive conduit alone, although the use of conductive conduits did enhance the effects of ES.

Recent advances in enhances peripheral nerve orientation: the synergy of micro or nano patterns with therapeutic tactics

Several studies suggest that topographical patterns influence nerve cell fate. Efforts have been made to improve nerve cell functionality through this approach, focusing on therapeutic strategies that enhance nerve cell function and support structures. However, inadequate nerve cell orientation can impede long-term efficiency, affecting nerve tissue repair. Therefore, enhancing neurites/axons directional growth and cell orientation is crucial for better therapeutic outcomes, reducing nerve coiling, and ensuring accurate nerve fiber connections. Conflicting results exist regarding the effects of micro- or nano-patterns on nerve cell migration, directional growth, immunogenic response, and angiogenesis, complicating their clinical use. Nevertheless, advances in lithography, electrospinning, casting, and molding techniques to intentionally control the fate and neuronal cells orientation are being explored to rapidly and sustainably improve nerve tissue efficiency. It appears that this can be accomplished by combining micro- and nano-patterns with nanomaterials, biological gradients, and electrical stimulation. Despite promising outcomes, the unclear mechanism of action, the presence of growth cones in various directions, and the restriction of outcomes to morphological and functional nerve cell markers have presented challenges in utilizing this method. This review seeks to clarify how micro- or nano-patterns affect nerve cell morphology and function, highlighting the potential benefits of cell orientation, especially in combined approaches.