Peripheral Nerve Regeneration and Muscle Reinnervation

Three-Year Outcomes After Posterior Nasal Neurectomy in Perennial Moderate and Severe Allergic Rhinitis Patients

BACKGROUND

Posterior nasal neurectomy (PNN) has been shown to reduce the symptom burden of patients with perennial moderate and severe allergic rhinitis (AR).

OBJECTIVES

To evaluate the long-term safety and effectiveness of PNN for the treatment of perennial moderate and severe AR.

METHODS

A prospective 3-year single-arm study was conducted in which the reflective total nasal symptom score (rTNSS) and total non-nasal symptom score (rTNNSS) were collected preoperatively and at 3 months, 6 months, 1 year, 2 years, and 3 years postoperatively.

RESULTS

A total of 213 patients with AR were recruited and received PNN, of whom 154 patients completed the 3-year follow-up. The mean rTNSS of the long-term follow-up patients improved from 7.74 (95% confidence interval [CI] 7.507-7.974) at baseline to 2.604 (95% CI 2.221-2.986), P < .001, at 6 months and showed sustained improvement to 3.156 (95% CI 2.806-3.506), P < .001, at 3 years. The mean rTNNSS ranged from 1.301 (95% CI 1.112-1.491) at baseline to 0.564 (95% CI 0.441-0.688) (P < .001) at 6 months and showed sustained improvement to 0.641 (95% CI 0.533-0.749) (P < .001) at 3 years. The rTNSS subscores (sneezing, congestion, rhinorrhea, and itching) and rTNNSS subscores (lacrimation, eye itching, postnasal drip, and cough) remained significantly improved from the baseline at all follow-up time points (all P < .001).

CONCLUSION

Posterior nasal neurectomy significantly and sustainably alleviated nasal and non-nasal symptoms of perennial moderate and severe AR and improved patient quality of life through 3 years postprocedure.

GalT Knockout Porcine Nerve Xenografts Support Axonal Regeneration in a Rodent Sciatic Nerve Model

BACKGROUND

Nerve xenografts harvested from transgenic α1,3-galactosyltransferase knockout pigs lack the epitope responsible for hyperacute rejection in pig-to-primate transplants. It is unknown whether these cold-preserved nerve grafts support axonal regeneration in another species during and after immunosuppression. The authors compared outcomes between autografts and cold-preserved xenografts in a rat sciatic model of nerve gap repair.

METHODS

Fifty male Lewis rats had a 1-cm sciatic nerve defect repaired using autograft and suture ( n = 10); 1-week or 4-week cold-preserved xenograft and suture ( n = 10 per group); or 1-week or 4-week cold-preserved xenograft and photochemical tissue bonding using a human amnion wrap ( n = 10 per group). Rats with xenografts were given tacrolimus until 4 months postoperatively. At 4 and 7 months, rats were killed and nerve sections were harvested. Monthly sciatic functional index (SFI) scores were calculated.

RESULTS

All groups showed increases in SFI scores by 4 and 7 months. The autograft suture group had the highest axon density at 4 and 7 months. The largest decrease in axon density from 4 to 7 months was in the group with 1-week cold-preserved photochemical tissue bonding using a human amnion wrap. The only significant difference between group SFI scores occurred at 5 months, when both 1-week cold-preserved groups had significantly lower scores than the 4-week cold-preserved suture group.

CONCLUSIONS

The results suggest that α1,3-galactosyltransferase knockout nerve xenografts may be viable alternatives to autografts. Further studies of long-gap repair and comparison with acellular nerve allografts are needed.

CLINICAL RELEVANCE STATEMENT

This proof-of-concept study in the rat sciatic model demonstrates that cold-preserved α1,3-galactosyltransferase knockout porcine xenografts support axonal regeneration and viability following immunosuppression withdrawal. These results further suggest a role for both cold preservation and photochemical tissue bonding in modulating the immunological response at the nerve repair site.

Physical modulation and peripheral nerve regeneration: a literature review

Peripheral nerve injury (PNI) usually causes severe motor, sensory and autonomic dysfunction. In addition to direct surgical repair, rehabilitation exercises, and traditional physical stimuli, for example, electrical stimulation, have been applied in promoting the clinical recovery of PNI for a long time but showed low efficiency. Recently, significant progress has been made in new physical modulation to promote peripheral nerve regeneration. We hereby review current progress on the mechanism of peripheral nerve regeneration after injury and summarize the new findings and evidence for the application of physical modulation, including electrical stimulation, light, ultrasound, magnetic stimulation, and mechanical stretching in experimental studies and the clinical treatment of patients with PNI.

Type I collagen extracellular matrix facilitates nerve regeneration via the construction of a favourable microenvironment

Background

The extracellular matrix (ECM) provides essential physical support and biochemical cues for diverse biological activities, including tissue remodelling and regeneration, and thus is commonly applied in the construction of artificial peripheral nerve grafts. Nevertheless, the specific functions of essential peripheral nerve ECM components have not been fully determined. Our research aimed to differentially represent the neural activities of main components of ECM on peripheral nerve regeneration.

Methods

Schwann cells from sciatic nerves and neurons from dorsal root ganglia were isolated and cultured in vitro. The cells were seeded onto noncoated dishes, Matrigel-coated dishes, and dishes coated with the four major ECM components fibronectin, laminin, collagen I, and collagen IV. The effects of these ECM components on Schwann cell proliferation were determined via methylthiazolyldiphenyl-tetrazolium bromide (MTT), Cell Counting Kit-8, and 5-ethynyl-2'-deoxyuridine (EdU) assays, whereas their effects on cell migration were determined via wound healing and live-cell imaging. Neurite growth in neurons cultured on different ECM components was observed. Furthermore, the two types of collagen were incorporated into chitosan artificial nerves and used to repair sciatic nerve defects in rats. Immunofluorescence analysis and a behavioural assessment, including gait, electrophysiology, and target muscle analysis, were conducted.

Results

ECM components, especially collagen I, stimulated the DNA synthesis and movement of Schwann cells. Direct measurement of the neurite lengths of neurons cultured on ECM components further revealed the beneficial effects of ECM components on neurite outgrowth. Injection of collagen I into chitosan and poly(lactic-co-glycolic acid) artificial nerves demonstrated that collagen I facilitated axon regeneration and functional recovery after nerve defect repair by stimulating the migration of Schwann cells and the formation of new blood vessels. In contrast, collagen IV recruited excess fibroblasts and inflammatory macrophages and thus had disadvantageous effects on nerve regeneration.

Conclusions

These findings reveal the modulatory effects of specific ECM components on cell populations of peripheral nerves, reveal the contributing roles of collagen I in microenvironment construction and axon regeneration, and highlight the use of collagen I for the healing of injured peripheral nerves.

Cellular crosstalk in the bone marrow niche

The bone marrow niche is a special microenvironment that comprises elements, including hematopoietic stem cells, osteoblasts, and endothelial cells, and helps maintain their characteristic functions. Here, we elaborate on the crosstalk between various cellular components, hematopoietic stem cells, and other cells in the bone marrow niche. We further explain the mechanism of preserving equilibrium in the bone marrow niche, which is crucial for the directional regulation of bone reconstruction and repair. Additionally, we elucidate the intercommunication among osteocytes, the regulation of osteoblast maturation and activation by lymphocytes, the deficiency of megakaryocytes that can markedly impair osteoblast formation, and the mechanism of interaction between macrophages and mesenchymal stem cells in the bone marrow niche. Finally, we discussed the new immunotherapies for bone tumors in the BM niche. In this review, we aimed to provide a candid overview of the crosstalk among bone marrow niche cells and to highlight new concepts underlying the unknown mechanisms of hematopoiesis and bone reconstruction. Thus, this review may provide a more comprehensive understanding of the role of these niche cells in improving hematopoietic function and help identify their therapeutic potential for different diseases in the future.

Conservative Management and Postoperative Return to Sport in Endurance Athletes with Flow Limitations in the Iliac Arteries: A Scoping Review

BACKGROUND

Flow limitations in the iliac arteries (FLIA) is a sport-related vascular condition increasingly recognised as an occupational risk for professional cyclists and other endurance athletes. Surgical reconstruction is the definitive treatment for athletes wishing to continue competition. However, less information has been published regarding conservative management options and return-to-sport (RTS) guidelines.

OBJECTIVE

Our aim was to review the existing literature on conservative treatment of FLIA, identify knowledge gaps and propose an RTS framework for athletes returning to competition.

METHODS

A comprehensive literature review was performed using the Ovid-MEDLINE, PubMed, Embase and PEDro databases for publications relevant to conservative management of FLIA. A scoping review was conducted following PRISMA-ScR guidelines. Original, peer-reviewed publications in English describing conservative or postoperative management for athletes with FLIA were included. Additional grey literature and clinical expertise were consulted to inform RTS guidelines.

RESULTS

Overall, 62 studies were included in this review. In total, 11 categories of conservative modalities were extracted and presented qualitatively in terms of the information source (discussion or results statements) and perspective of the authors (positive, negative or mixed). We have proposed RTS guidelines covering pre-operative preparation and postoperative rehabilitation based on the available literature, clinical experience, and drawing from other areas of sports medicine research.

CONCLUSION

There is insufficient literature evaluating the effectiveness of conservative management options for FLIA to establish best practices. Considering the importance of RTS for competitive athletes, we proposed practical guidelines to help with clinician and patient decision making. Future consensus should be sought for RTS best practices.

Glycyrrhizic acid promote remyelination after peripheral nerve injury by reducing NF-κB activation

BACKGROUND

Peripheral nerve injury (PNI) causes motor and sensory defects, has strong impact on life quality and still has no effective therapy. Glycyrrhizic acid (GA) is one of the most widely used in traditional Chinese prescriptions and as a flavoring additive in the food industry; the aims of the study were to investigate the effects of GA during sciatic nerve regeneration in a mouse model of sciatic nerve crush injury.

METHODS

We established peripheral nerve crush model and investigated the effects of GA. We further studied the potential mechanism of action of GA by Western blotting, fluorescence immunohistochemistry, and PCR analysis.

RESULTS

GA improves the sensory and motor functions of crushed nerve by preventing Schwann cell loss, axonal loss and promoting remyelination of sciatic nerve. Affected by GA, the inflammatory response in the distal part of the sciatic nerve was reduced. Finally, the neuroprotective properties of GA may be regulated by the nuclear factor (NF)-κB pathway.

CONCLUSIONS

Our data suggest that GA can effectively alleviate PNI, and the mechanism involves mediating inflammatory response by suppressing NF-κB pathway activation. Thus, GA may represent a potential therapeutic intervention for nerve crush injury.

Combining external physical stimuli and nanostructured materials for upregulating pro-regenerative cellular pathways in peripheral nerve repair

Peripheral nerve repair remains a major clinical challenge, particularly in the pursuit of therapeutic approaches that ensure adequate recovery of patient's activity of daily living. Autografts are the gold standard in clinical practice for restoring lost sensorimotor functions nowadays. However, autografts have notable drawbacks, including dimensional mismatches and the need to sacrifice one function to restore another. Engineered nerve guidance conduits have therefore emerged as promising alternatives. While these conduits show surgical potential, their clinical use is currently limited to the repair of minor injuries, as their ability to reinnervate limiting gap lesions is still unsatisfactory. Therefore, improving patient functional recovery requires a deeper understanding of the cellular mechanisms involved in peripheral nerve regeneration and the development of therapeutic strategies that can precisely modulate these processes. Interest has grown in the use of external energy sources, such as light, ultrasound, electrical, and magnetic fields, to activate cellular pathways related to proliferation, differentiation, and migration. Recent research has explored combining these energy sources with tailored nanostructured materials as nanotransducers to enhance selectivity towards the target cells. This review aims to present the recent findings on this innovative strategy, discussing its potential to support nerve regeneration and its viability as an alternative to autologous transplantation.

Transplantation of embryonic spinal motor neurons into peripheral nerves enables functional reconstruction of a denervated diaphragm

Respiratory muscle paralysis due to trauma or neurodegenerative diseases can have devastating consequences. Only a few studies have investigated the reconstruction of motor function in denervated diaphragms caused by such conditions. Here, we studied the efficacy of transplanting E14 embryonic spinal motor neurons (SMNs) into peripheral nerve grafts for functionally reconstructing a denervated diaphragm in a rat model. The diaphragms of 8-week-old male Fischer 344 rats were first denervated by transecting the phrenic nerves. Subsequently, peripheral nerve grafts taken from the lower limb were used for neurotization of the denervated diaphragms. One week later, fetal E14 SMNs were transplanted into the peripheral nerve grafts. After 3 months, we observed functional contraction of the diaphragm following neuromuscular electrical stimulation (NMES) of the peripheral nerve graft. Additionally, we confirmed that SMN transplantation into the peripheral nerve graft had an inhibitory effect on diaphragm muscle atrophy. The SMNs transplanted into the peripheral nerve grafts formed a structure similar to the spinal cord, and the neuromuscular junction of the denervated diaphragm was reinnervated. These findings suggest the establishment of an ectopic motor neuron pool in the peripheral nerve graft. Free peripheral intra-nerve SMN transplantation in combination with NMES, which can be applied for diaphragmatic pacing, offers novel insights into the development of neuroregenerative therapies for treating life-threatening and intractable respiratory muscle paralysis caused by severe nerve damage and degenerative diseases.

Accelerated innervation of biofabricated skeletal muscle implants containing a neurotrophic factor delivery system

Introduction

Volumetric muscle loss (VML) is one of the most severe and debilitating conditions in orthopedic and regenerative medicine. Current treatment modalities often fail to restore the normal structure and function of the damaged skeletal muscle. Bioengineered tissue constructs using the patient's own cells have emerged as a promising alternative treatment option, showing positive outcomes in fostering new muscle tissue formation. However, achieving timely and proper innervation of the implanted muscle constructs remains a significant challenge. In this study, we present a clinically relevant strategy aimed at enhancing and sustaining the natural regenerative response of peripheral nerves to accelerate the innervation of biofabricated skeletal muscle implants.

Methods

We previously developed a controlled-release neurotrophic factor delivery system using poly (lactic-co-glycolic acid) (PLGA) microspheres encapsulating ciliary neurotrophic factor (CNTF) and glial cell line-derived neurotrophic factor (GDNF). Here, we incorporate this neurotrophic factor delivery system into bioprinted muscle constructs to facilitate innervation in vivo.

Results

Our results demonstrate that the neurotrophic factors released from the microspheres provide a chemical cue, significantly enhancing the neurite sprouting and functional innervation of the muscle cells in the biofabricated muscle construct within 12 weeks post-implantation.

Discussion

Our approach provides a clinically applicable treatment option for VML through accelerated innervation of biomanufactured muscle implants and subsequent improvements in functionality.

Cimifugin Alleviates Chronic Constriction Injury of the Sciatic Nerve by Suppressing Inflammatory Response and Schwann Cell Apoptosis

Inflammation and Schwann cell apoptosis play critical roles in neuropathic pain after sciatic nerve injury. This study aimed to explore the function and mechanism of cimifugin in lipopolysaccharide (LPS)-stimulated rat Schwann cells and sciatic nerves of rats treated with chronic constriction injury (CCI). Thermal, mechanical and cold hyperalgesia of rats in response to cimifugin or mecobalamin (the positive drug control) treatment were evaluated through behavioral tests. H&E staining of sciatic nerves was performed for pathological observation. ELISA was conducted to assess concentrations of inflammatory cytokines in rat serum and sciatic nerves. The intensity of S100β in sciatic nerves was determined using immunohistochemistry. Flow cytometry analysis was conducted for detection of Schwann cell apoptosis. RT-qPCR was performed to measure mRNA levels of inflammatory factors in Schwann cells. Immunofluorescence staining was performed to detect cellular p65/NF-κB activity. Western blotting was performed to quantify protein levels of apoptotic markers and factors associated with the NF-κB and MAPK pathways in rat nerves and Schwann cells. As shown by experimental data, cimifugin mitigated thermal, mechanical and cold hyperalgesia of CCI rats. Cimifugin repressed inflammatory cell infiltration, reduced proinflammatory cytokine levels while increasing anti-inflammatory factor (IL-10) level in serum or sciatic nerves of CCI rats. Cimifugin enhanced S100β expression and downregulated apoptotic markers in vivo. The anti-inflammatory and anti-apoptotic properties of cimifugin were verified in the LPS-stimulated Schwann cells. Moreover, cimifugin suppressed nuclear translocation of p65 NF-κB in vitro and repressed the phosphorylation of IκB, p65 NF-κB, p38 MAPK, ERK1/2, as well as JNK in CCI rats. In conclusion, cimifugin alleviates neuropathic pain after sciatica by suppressing inflammatory response and Schwann cell apoptosis via inactivation of NF-κB and MAPK pathways.

Effects of the matrix-bounded nanovesicles of high-hydrostatic pressure decellularized tissues on neural regeneration

Decellularized tissues have been used as implantable materials for tissue regeneration because of their high biofunctionality. We have reported that high hydrostatic pressured (HHP) decellularized tissue developed in our laboratory exhibits good in vivo performance, but the details of the mechanism are still not known. Based on previous reports of bioactive factors called matrix bound nanovesicles (MBVs) within decellularized tissues, this study aims to investigate whether MBVs are also present in decellularized tissues prepared by HHP decellularization, which is different from the previously reported methods. In this study, we tried to extract bioactive factors from HHP decellularized brain and placenta, and evaluated their effects on nerves in vitro and in vivo, where its effects have been previously reported. The results confirmed that those factors can be extracted even if the decellularization method and tissue of origin differ, and that they have effects on a series of processes toward nerve regeneration, such as neurite outgrowth and nerve fiber repair.

A neural algorithm for computing bipartite matchings

Finding optimal bipartite matchings-e.g., matching medical students to hospitals for residency, items to buyers in an auction, or papers to reviewers for peer review-is a fundamental combinatorial optimization problem. We found a distributed algorithm for computing matchings by studying the development of the neuromuscular circuit. The neuromuscular circuit can be viewed as a bipartite graph formed between motor neurons and muscle fibers. In newborn animals, neurons and fibers are densely connected, but after development, each fiber is typically matched (i.e., connected) to exactly one neuron. We cast this synaptic pruning process as a distributed matching (or assignment) algorithm, where motor neurons "compete" with each other to "win" muscle fibers. We show that this algorithm is simple to implement, theoretically sound, and effective in practice when evaluated on real-world bipartite matching problems. Thus, insights from the development of neural circuits can inform the design of algorithms for fundamental computational problems.

Comparison of Neural Recovery Effects of Botulinum Toxin Based on Administration Timing in Sciatic Nerve-Injured Rats

This study aimed to assess the effects of the timing of administering botulinum neurotoxin A (BoNT/A) on nerve regeneration in rats. Sixty 6-week-old rats with a sciatic nerve injury were randomly divided into four groups: the immediately treated (IT) group (BoNT/A injection administered immediately post-injury), the delay-treated (DT) group (BoNT/A injection administered one week post-injury), the control group (saline administered one week post-injury), and the sham group (only skin and muscle incisions made). Nerve regeneration was assessed 3, 6, and 9 weeks post-injury using various techniques. The levels of glial fibrillary acid protein (GFAP), astroglial calcium-binding protein S100β (S100β), growth-associated protein 43 (GAP43), neurofilament 200 (NF200), and brain-derived neurotrophic factor (BDNF) in the IT and DT groups were higher. ELISA revealed the highest levels of these proteins in the IT group, followed by the DT and control groups. Toluidine blue staining revealed that the average area and myelin thickness were higher in the IT group. Electrophysiological studies revealed that the CMAP in the IT group was significantly higher than that in the control group, with the DT group exhibiting significant differences starting from week 8. The findings of the sciatic functional index analysis mirrored these results. Thus, administering BoNT/A injections immediately after a nerve injury is most effective for neural recovery. However, injections administered one week post-injury also significantly enhanced recovery. BoNT/A should be administered promptly after nerve damage; however, its administration during the non-acute phase is also beneficial.

Reduced osseointegration in disuse and denervation rat models results from impaired cellular responses to multiscale microstructured titanium surfaces

Immobilization-induced skeletal unloading results in muscle atrophy and rapid bone loss, thereby increasing the risk of falling and the need for implant therapy in patients with extended bed rest or neuromuscular injuries. Skeletal unloading causes bone loss by altering bone growth and resorption, suggesting that implant performance might be affected. To test this, we focused on early events in implant osseointegration. We used the rat sciatic neurectomy-induced disuse model under two different settings. In Study 1, 16 Sprague Dawley rats (SD) were separated into control, sham operated+cast immobilization, and sciatic neurectomy+casting groups; titanium implants with multiscale microtextured topography and hydrophilic chemistry (modSLA) were inserted in the distal femoral metaphysis. Neurectomy surgeries and casting were performed at the same surgical setting as implant placement; rats were euthanized 4 weeks post-implantation. In Study 2, we established the unloaded condition before implantation. A total of 12 SD rats were divided into control and sciatic+femoral neurectomy groups. A total of 24 days after sciatic and femoral neurectomy surgery, rats received implants. Study 2 rats were euthanized at 4 weeks post-implantation. MicroCT and histomorphometry showed that trabecular bone and osseointegration were reduced when disuse was established before implantation. Osteoblasts isolated from Study 1 sciatic neurectomy tibial bones exhibited impaired differentiation on modSLA culture disks, revealing a possible mechanism responsible for the decreased osseointegration observed in the Study 2 rats. This study addressed the importance of considering the mechanical unloading and muscle function history before implant insertion and suggests that implant performance was reduced due to poor cellular ability to regenerate.

Optimal Technique for Cutting Peripheral Nerves in Nerve Transfer Surgery: A Survey of Peripheral Nerve Surgeons

Background

Nerve transfer procedures are performed in patients with proximal nerve injuries to optimize their potential for functional recovery. The study aimed to determine the preferred surgical technique and tool used by peripheral nerve surgeons to transect nerves in nerve transfers.

Methods

All current members of the American Society of Peripheral Nerve were invited to complete a cross-sectional 10-question survey. Data on practice demographics, nerve-cutting instruments/techniques used, and their belief on whether this impacted patient outcomes were collected.

Results

A total of 49 American Society of Peripheral Nerve members participated in the study, the majority of whom were over 10 years into practice (n = 30/49; 61%). The most common response was a scalpel blade (n = 26/49; 53%), with the remaining 47% using iris scissors, micro-serrated scissors, a razor blade, specialized nerve microscissors, or a specialized nerve-cutting device. The number of years in practice (P = 0.0271) and the percentage of practice that involves treating patients with peripheral nerve injuries (P = 0.0054) is significantly associated with the belief that crushing the donor nerves during transection may result in worse outcomes following nerve transfer. Only the latter is significantly associated with this belief in recipient nerves (P = 0.0214).

Conclusions

Our findings demonstrate that peripheral nerve surgeons believe that the technique used to transect nerves before coaptation influences outcomes after nerve transfer. Further ex vivo studies are necessary to investigate how different cutting techniques influence nerve morphology and scarring at the coaptation site to optimize outcomes after peripheral nerve surgery.

Vastus Lateralis Transfer for Reconstruction of Hip Abduction following Superior Gluteal Nerve Injury

A 71-year-old man who had hip abductor insufficiency due to a chronic injury to the right superior gluteal nerve injury after lipoma resection presented to our outpatient clinic 1.5 years postoperatively with persistent pain, atrophy of the gluteus medius muscle, and Trendelenburg sign with a corresponding limp. A magnetic resonance imaging scan and neurophysiological diagnostics confirmed a chronic lesion of the superior gluteal nerve with completed reinnervation and absent pathological spontaneous activity, excluding neurosurgical options to restore hip abduction. Following interdisciplinary evaluation of the patient's case, we performed a vastus lateralis transfer in May 2023 to stabilize the right hip joint. The entire vastus lateralis muscle was carefully freed from the surrounding tissue, and its attachment to the quadriceps tendon was separated. The proximal section of the lateral vastus was then fixed to the ilium and greater trochanter, while the muscle's distal portion was sutured to a more proximal part of the quadriceps muscle. The postoperative course was without any complications, and the patient left the hospital with an abduction splint 10 days after surgery. When he presented to our outpatient clinic 10 weeks after surgery, he reported a significantly improved gait and reduction of pain. Trendelenburg sign was now absent, but right knee function was not impaired and the patient was able to ambulate without the regular need for an orthosis. A transfer of the vastus lateralis muscle is therefore a valuable option to restore hip abductor function in cases of chronic nerve lesions which exclude neurosurgical options.

Non-Coding RNA in Schwann Cell and Peripheral Nerve Injury: A Review

Peripheral nerve injury (PNI) can result in severe disabilities, profoundly impacting patients' quality of life and potentially endangering their lives. Therefore, understanding the potential molecular mechanisms that facilitate the regeneration of damaged nerves is crucial. Evidence indicates that Schwann cells (SCs) play a pivotal role in repairing peripheral nerve injuries. Previous studies have shown that RNA, particularly non-coding RNA (ncRNA), plays a crucial role in nerve regeneration, including the proliferation and dedifferentiation of SCs. In this review, the individual roles of ncRNA in SCs and PNI are analyzed. This review not only enhances the understanding of ncRNA's role in nerve injury repair but also provides a significant theoretical foundation and inspiration for the development of new therapeutic strategies.

The telocytes relationship with satellite cells: Extracellular vesicles mediate the myotendinous junction remodeling

The peripheral nerve injury (PNI) affects the morphology of the whole locomotor apparatus, which can reach the myotendinous junction (MTJ) interface. In the injury condition, the skeletal muscle satellite cells (SC) are triggered, activated, and proliferated to repair their structure, and in the MTJ, the telocytes (TC) are associated to support the interface with the need for remodeling; in that way, these cells can be associated with SC. The study aimed to describe the SC and TC relationship after PNI at the MTJ. Sixteen adult Wistar rats were divided into Control Group (C, n = 8) and PNI Group (PNI, n = 8), PNI was performed by the constriction of the sciatic nerve. The samples were processed for transmission electron microscopy and immunostaining analysis. In the C group was evidenced the arrangement of sarcoplasmic evaginations and invaginations, the support collagen layer with a TC inside it, and an SC through vesicles internally and externally to then. In the PNI group were observed the disarrangement of invaginations and evaginations and sarcomeres degradation at MTJ, as the disposition of telopodes adjacent and in contact to the SC with extracellular vesicles and exosomes in a characterized paracrine activity. These findings can determine a link between the TCs and the SCs at the MTJ remodeling. RESEARCH HIGHLIGHTS: Peripheral nerve injury promotes the myotendinous junction (MTJ) remodeling. The telocytes (TC) and the satellite cells (SC) are present at the myotendinous interface. TC mediated the SC activity at MTJ.

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.

Advances in Exosome-Based Therapies for the Repair of Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are the term used to describe injuries that occur to the nerve fibers of the peripheral nervous system (PNS). Such injuries may be caused by trauma, infection, or aberrant immunological response. Although the peripheral nervous system has a limited capacity for self-repair, in cases of severe damage, this process is either interrupted entirely or is only partially completed. The evaluation of variables that promote the repair of peripheral nerves has consistently been a focal point. Exosomes are a subtype of extracellular vesicles that originate from cellular sources and possess abundant proteins, lipids, and nucleic acids, play a critical role in facilitating intercellular communication. Due to their modifiable composition, they possess exceptional capabilities as carriers for therapeutic compounds, including but not limited to mRNAs or microRNAs. Exosome-based therapies have gained significant attention in the treatment of several nervous system diseases due to their advantageous properties, such as low toxicity, high stability, and limited immune system activation. The objective of this review article is to provide an overview of exosome-based treatments that have been developed in recent years for a range of PNIs, including nerve trauma, diabetic neuropathy, amyotrophic lateral sclerosis (ALS), glaucoma, and Guillain-Barre syndrome (GBS). It was concluded that exosomes could provide favorable results in the improvement of peripheral PNIs by facilitating the transfer of regenerative factors. The development of bioengineered exosome therapy for PNIs should be given more attention to enhance the efficacy of exosome treatment for PNIs.

Nerve Autograft: Preservation of a Lost Art

Nerve autografts involve the transplantation of a segment of the patient's own nerve to bridge a nerve gap. Autografts provide biological compatibility, support for axonal regeneration, and the ability to provide an anatomic scaffold for regrowth that other modalities may not match. Disadvantages of the autograft include donor site morbidity and the extra operative time needed to harvest the graft. Nevertheless, nerve autografts such as the sural nerve remain the gold standard in reconstructing nerve gaps, but a multitude of factors need to be favorable in order to garner reliable, consistent outcomes.

Physiology of Nerve Regeneration: Key Factors Affecting Clinical Outcomes

Functional recovery after peripheral nerve injuries is disappointing despite surgical advances in nerve repair. This review summarizes the relatively short window of opportunity for successful nerve regeneration due to the decline in the expression of growth-associated genes and in turn, the decline in regenerative capacity of the injured neurons and the support provided by the denervated Schwann cells, and the atrophy of denervated muscles. Brief, low-frequency electrical stimulation and post-injury exercise regimes ameliorate these deficits in animal models and patients, but the misdirection of regenerating nerve fibers compromises functional recovery and remains an important area of future research.

Biohacking Nerve Repair: Novel Biomaterials, Local Drug Delivery, Electrical Stimulation, and Allografts to Aid Surgical Repair

The regenerative capacity of the peripheral nervous system is limited, and peripheral nerve injuries often result in incomplete healing and poor outcomes even after repair. Transection injuries that induce a nerve gap necessitate microsurgical intervention; however, even the current gold standard of repair, autologous nerve graft, frequently results in poor functional recovery. Several interventions have been developed to augment the surgical repair of peripheral nerves, and the application of functional biomaterials, local delivery of bioactive substances, electrical stimulation, and allografts are among the most promising approaches to enhance innate healing across a nerve gap. Biocompatible polymers with optimized degradation rates, topographic features, and other functions provided by their composition have been incorporated into novel nerve conduits (NCs). Many of these allow for the delivery of drugs, neurotrophic factors, and whole cells locally to nerve repair sites, mitigating adverse effects that limit their systemic use. The electrical stimulation of repaired nerves in the perioperative period has shown benefits to healing and recovery in human trials, and novel biomaterials to enhance these effects show promise in preclinical models. The use of acellular nerve allografts (ANAs) circumvents the morbidity of donor nerve harvest necessitated by the use of autografts, and improvements in tissue-processing techniques may allow for more readily available and cost-effective options. Each of these interventions aid in neural regeneration after repair when applied independently, and their differing forms, benefits, and methods of application present ample opportunity for synergistic effects when applied in combination.

Novel Technologies to Address the Lower Motor Neuron Injury and Augment Reconstruction in Spinal Cord Injury

Lower motor neuron (LMN) damage results in denervation of the associated muscle targets and is a significant yet under-appreciated component of spinal cord injury (SCI). Denervated muscle undergoes a progressive degeneration and fibro-fatty infiltration that eventually renders the muscle non-viable unless reinnervated within a limited time window. The distal nerve deprived of axons also undergoes degeneration and fibrosis making it less receptive to axons. In this review, we describe the LMN injury associated with SCI and its clinical consequences. The process of degeneration of the muscle and nerve is broken down into the primary components of the neuromuscular circuit and reviewed, including the nerve and Schwann cells, the neuromuscular junction, and the muscle. Finally, we discuss three promising strategies to reverse denervation atrophy. These include providing surrogate axons from local sources; introducing stem cell-derived spinal motor neurons into the nerve to provide the missing axons; and finally, instituting a training program of high-energy electrical stimulation to directly rehabilitate these muscles. Successful interventions for denervation atrophy would significantly expand reconstructive options for cervical SCI and could be transformative for the predominantly LMN injuries of the conus medullaris and cauda equina.

Biological characteristics of tissue engineered-nerve grafts enhancing peripheral nerve regeneration

BACKGROUND

A favorable regenerative microenvironment is essential for peripheral nerve regeneration. Neural tissue-specific extracellular matrix (ECM) is a natural material that helps direct cell behavior and promote axon regeneration. Both bone marrow-derived mesenchymal stem cells (BMSCs) and adipose-derived mesenchymal stem cells (ADSCs) transplantation are effective in repairing peripheral nerve injury (PNI). However, there is no study that characterizes the in vivo microenvironmental characteristics of these two MSCs for the early repair of PNI when combined with neural tissue-derived ECM materials, i.e., acellular nerve allograft (ANA).

METHODS

In order to investigate biological characteristics, molecular mechanisms of early stage, and effectiveness of ADSCs- or BMSCs-injected into ANA for repairing PNI in vivo, a rat 10 mm long sciatic nerve defect model was used. We isolated primary BMSCs and ADSCs from bone marrow and adipose tissue, respectively. First, to investigate the in vivo response characteristics and underlying molecular mechanisms of ANA combined with BMSCs or ADSCs, eighty-four rats were randomly divided into three groups: ANA group, ANA+BMSC group, and ANA+ADSC group. We performed flow cytometry, RT-PCR, and immunofluorescence staining up to 4 weeks postoperatively. To further elucidate the underlying molecular mechanisms, changes in long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) were systematically investigated using whole transcriptome sequencing. We then constructed protein-protein interaction networks to find 10 top ranked hub genes among differentially expressed mRNAs. Second, in order to explore the effectiveness of BMSCs and ADSCs on neural tissue-derived ECM materials for repairing PNI, sixty-eight rats were randomized into four groups: ANA group, ANA+BMSC group, ANA+ADSC group, and AUTO group. In the ANA+BMSC and ANA+ADSC groups, ADSCs/BMSCs were equally injected along the long axis of the 10-mm ANA. Then, we performed histological and functional assessments up to 12 weeks postoperatively.

RESULTS

The results of flow cytometry and RT-PCR showed that ANA combined with BMSCs exhibited more significant immunomodulatory effects, as evidenced by the up-regulation of interleukin (IL)-10, down-regulation of IL-1β and tumor necrosis factor-alpha (TNF-α) expression, promotion of M1-type macrophage polarization to M2-type, and a significant increase in the number of regulatory T cells (Tregs). ANA combined with ADSCs exhibited more pronounced features of pro-myelination and angiogenesis, as evidenced by the up-regulation of myelin-associated protein gene (MBP and MPZ) and angiogenesis-related factors (TGF-β, VEGF). Moreover, differentially expressed genes from whole transcriptome sequencing results further indicated that ANA loaded with BMSCs exhibited notable immunomodulatory effects and ANA loaded with ADSCs was more associated with angiogenesis, axonal growth, and myelin formation. Notably, ANA infused with BMSCs or ADSCs enhanced peripheral nerve regeneration and motor function recovery with no statistically significant differences.

CONCLUSIONS

This study revealed that both ANA combined with BMSCs and ADSCs enhance peripheral nerve regeneration and motor function recovery, but their biological characteristics (mainly including immunomodulatory effects, pro-vascular regenerative effects, and pro-myelin regenerative effects) and underlying molecular mechanisms in the process of repairing PNI in vivo are different, providing new insights into MSC therapy for peripheral nerve injury and its clinical translation.

Augmentation of functional recovery via ROCK/PI3K/AKT pathway by Fasudil Hydrochloride in a rat sciatic nerve transection model

Backgrounds

The functional recovery after peripheral nerve injury remains unsatisfactory. This study aims to perform a comprehensive evaluation of the efficacy of Fasudil Hydrochloride at treating the sciatic nerve transection injury in rats and the mechanism involved.

Materials and methods

In animal experiments, 75 Sprague Dawley rats that underwent transection and repair of the right sciatic nerve were divided into a control, Fasudil, and Fas + LY group, receiving daily intraperitoneal injection of saline, Fasudil Hydrochloride (10 mg/kg), and Fasudil Hydrochloride plus LY294002 (5 mg/kg), respectively. At day 3 after surgery, the expression of ROCK2, p-PI3K, and p-AKT in L4-5 DRG and the lumbosacral enlargement was determined using Western blotting. At day 7 and 14, axon density in the distal stump was evaluated with immunostaining using the anti-Neurofilament-200 antibody. At day 30, retrograde tracing by injecting Fluoro-gold in the distal stump was performed. Three months after surgery, remyelination was analyzed with immostaining using the anti-MPZ antibody and the transmission electron microscope; Moreover, Motion-Evoked Potential, and recovery of sensorimotor functions was evaluated with a neuromonitor, Footprint, Hot Plate and Von Frey Filaments, respectively. Moveover, the Gastrocnemius muscles were weighed, and then underwent H＆E staining, and staining of the neuromuscular junction using α-Bungarotoxin to evaluate the extent of atrophy and degeneration of the endplates in the Gastrocnemius. In vitro, spinal motor neurons (SMNs) and dorsal root ganglia (DRG) were cultured to examine the impact of Fasudil Hydrochloride and LY294002 on the axon outgrowth.

Results

Three days after injury, the expression of ROCK2 increased significantly (P＜0.01), and Fasudil application significantly increased the expression of p-PI3K and p-AKT in L4-6 DRG and the lumbosacral enlargement (P < 0.05). At day 7 and 14 after surgery, a higher axon density could be observed in the Fasudil group(P < 0.05). At day 30 after surgery, a larger number of motor and sensory neurons absorbing Fluoro-gold could be observed in the Fasudil group (P < 0.01) Three months after surgery, a greater thickness of myelin sheath could be observed in the Fasudil group (P < 0.05). The electrophysiological test showed that a larger amplitude of motion-evoked potential could be triggered in the Fasudil group (P < 0.01). Behavioral tests showed that a higher sciatic function index and a lower threshold for reacting to heat and mechanical stimuli could be measured in the Fasudil group. (P < 0.01). The wet weight ratio of the Gastrocnemius muscles and the area of the cross section of its myofibrils were greater in the Fasudil group (P < 0.01), which also demonstrated a higer ratio of axon-endplate connection and a larger size of endplates (P < 0.05). And there were no significant differences for the abovementioned parameters between the control and Fas + LY groups (P＞0.05). In vitro studies showed that Fasudil could significantly promote axon growth in DRG and SMNs, and increase the expression of p-PI3K and p-AKT, which could be abolished by LY294002 (P < 0.05).

Conclusions

Fasudil can augment axon regeneration and remyelination, and functional recovery after sciatic nerve injury by activating the PI3K/AKT pathway.

The translational potential of this article

The translation potential of this article is that we report for the first time that Fasudil Hydrochloride has a remarkable efficacy at improving axon regeneration and remyelination following a transection injury of the right sciatic nerve in rats through the ROCK/PI3K/AKT pathway, which has a translational potential to be used clinically to treat peripheral nerve injury.

Opioid Prescriptions at Discharge After Minimally Invasive Repair of Pectus Excavatum Are Reduced With Cryoablation

BACKGROUND

The minimally invasive repair of pectus excavatum (MIRPE) is associated with significant postoperative pain and opioid use. The objective of this study was to determine the effect of intercostal nerve cryoablation (Cryo) on inpatient and post-hospital opioid prescription practices following MIPRE.

METHODS

A retrospective review at a single pediatric center was conducted of patients ≤21 years old who underwent MIRPE. Oral morphine equivalents (OME) of inpatient and discharge opioids were compared between Cryo and no-Cryo cohorts.

RESULTS

579 patients were identified (82.8% male, mean age 15.4 ± 2.0 years). Cryo was performed in 73.5% of patients. The total inpatient OME use was less in the Cryo group (0.89 ± 0.68 vs. 1.6 ± 0.5 OME/kg/day; p < 0.001). Patients who underwent Cryo were prescribed significantly less OME at discharge compared to the no-Cryo group (3.9 ± 1.7 vs. 10.0 ± 4.1 OME mg/kg, p < 0.001). There was no statistically significant difference in the proportion of patients who required an opioid prescription refill (Cryo 12.4% vs. no-Cryo 11.5%, p = 0.884) or were readmitted (Cryo 5.3% vs. no-Cryo 4.6%, p = 0.833).

CONCLUSION

Patients who underwent cryoablation during MIRPE were prescribed significantly less opioid at the time of discharge without increasing the need for opioid refills or hospital readmissions.

LEVEL OF EVIDENCE

Treatment study; Level III evidence.

Adrenergic microenvironment driven by cancer-associated Schwann cells contributes to chemoresistance in patients with lung cancer

Doublecortin (DCX)-positive neural progenitor-like cells are purported components of the cancer microenvironment. The number of DCX-positive cells in tissues reportedly correlates with cancer progression; however, little is known about the mechanism by which these cells affect cancer progression. Here we demonstrated that DCX-positive cells, which are found in all major histological subtypes of lung cancer, are cancer-associated Schwann cells (CAS) and contribute to the chemoresistance of lung cancer cells by establishing an adrenergic microenvironment. Mechanistically, the activation of the Hippo transducer YAP/TAZ was involved in the acquisition of new traits of CAS and DCX positivity. We further revealed that CAS express catecholamine-synthesizing enzymes and synthesize adrenaline, which potentiates the chemoresistance of lung cancer cells through the activation of YAP/TAZ. Our findings shed light on CAS, which drive the formation of an adrenergic microenvironment by the reciprocal regulation of YAP/TAZ in lung cancer tissues.

Electrical stimulation with polypyrrole-coated polycaprolactone/silk fibroin scaffold promotes sacral nerve regeneration by modulating macrophage polarisation

Peripheral nerve injury poses a great threat to neurosurgery and limits the regenerative potential of sacral nerves in the neurogenic bladder. It remains unknown whether electrical stimulation can facilitate sacral nerve regeneration in addition to modulate bladder function. The objective of this study was to utilise electrical stimulation in sacra nerve crush injury with newly constructed electroconductive scaffold and explore the role of macrophages in electrical stimulation with crushed nerves. As a result, we generated a polypyrrole-coated polycaprolactone/silk fibroin scaffold through which we applied electrical stimulation. The electrical stimulation boosted nerve regeneration and polarised the macrophages towards the M2 phenotype. An in vitro test using bone marrow derived macrophages revealed that the pro-regenerative polarisation of M2 were significantly enhanced by electrical stimulation. Bioinformatics analysis showed that the expression of signal transducer and activator of transcriptions (STATs) was differentially regulated in a way that promoted M2-related genes expression. Our work indicated the feasibility of electricals stimulation used for sacral nerve regeneration and provided a firm demonstration of a pivotal role which macrophages played in electrical stimulation.

Photosealed Neurorrhaphy Using Autologous Tissue

Photochemical sealing of a nerve wrap over the repair site isolates and optimizes the regenerating nerve microenvironment. To facilitate clinical adoption of the technology, we investigated photosealed autologous tissue in a rodent sciatic nerve transection and repair model. Rats underwent transection of the sciatic nerve with repair performed in three groups: standard microsurgical neurorrhaphy (SN) and photochemical sealing with a crosslinked human amnion (xHAM) or autologous vein. Functional recovery was assessed at four-week intervals using footprint analysis. Gastrocnemius muscle mass preservation, histology, and nerve histomorphometry were evaluated at 120 days. Nerves treated with a PTB-sealed autologous vein improved functional recovery at 120 days although the comparison between groups was not significantly different (SN: -58.4 +/- 10.9; XHAM: -57.9 +/- 8.7; Vein: -52.4 +/- 17.1). Good muscle mass preservation was observed in all groups, with no statistical differences between groups (SN: 69 +/- 7%; XHAM: 70 +/- 7%; Vein: 70 +/- 7%). Histomorphometry showed good axonal regeneration in all repair techniques. These results demonstrate that peripheral nerve repair using photosealed autologous veins produced regeneration at least equivalent to current gold-standard microsurgery. The use of autologous veins removes costs and foreign body concerns and would be readily available during surgery. This study illustrates a new repair method that could restore normal endoneurial homeostasis with minimal trauma following severe nerve injury.

Inflammation in the Peripheral Nervous System after Injury

Nerve injury is a common condition that occurs as a result of trauma, iatrogenic injury, or long-lasting stimulation. Unlike the central nervous system (CNS), the peripheral nervous system (PNS) has a strong capacity for self-repair and regeneration. Peripheral nerve injury results in the degeneration of distal axons and myelin sheaths. Macrophages and Schwann cells (SCs) can phagocytose damaged cells. Wallerian degeneration (WD) makes the whole axon structure degenerate, creating a favorable regenerative environment for new axons. After nerve injury, macrophages, neutrophils and other cells are mobilized and recruited to the injury site to phagocytose necrotic cells and myelin debris. Pro-inflammatory and anti-inflammatory factors involved in the inflammatory response provide a favorable microenvironment for peripheral nerve regeneration and regulate the effects of inflammation on the body through relevant signaling pathways. Previously, inflammation was thought to be detrimental to the body, but further research has shown that appropriate inflammation promotes nerve regeneration, axon regeneration, and myelin formation. On the contrary, excessive inflammation can cause nerve tissue damage and pathological changes, and even lead to neurological diseases. Therefore, after nerve injury, various cells in the body interact with cytokines and chemokines to promote peripheral nerve repair and regeneration by inhibiting the negative effects of inflammation and harnessing the positive effects of inflammation in specific ways and at specific times. Understanding the interaction between neuroinflammation and nerve regeneration provides several therapeutic ideas to improve the inflammatory microenvironment and promote nerve regeneration.

Schwann Cells as Orchestrators of Nerve Repair: Implications for Tissue Regeneration and Pathologies

Peripheral nerves exist in a stable state in adulthood providing a rapid bidirectional signaling system to control tissue structure and function. However, following injury, peripheral nerves can regenerate much more effectively than those of the central nervous system (CNS). This multicellular process is coordinated by peripheral glia, in particular Schwann cells, which have multiple roles in stimulating and nurturing the regrowth of damaged axons back to their targets. Aside from the repair of damaged nerves themselves, nerve regenerative processes have been linked to the repair of other tissues and de novo innervation appears important in establishing an environment conducive for the development and spread of tumors. In contrast, defects in these processes are linked to neuropathies, aging, and pain. In this review, we focus on the role of peripheral glia, especially Schwann cells, in multiple aspects of nerve regeneration and discuss how these findings may be relevant for pathologies associated with these processes.

Muscle preservation in proximal nerve injuries: a current update

Optimal recovery of muscle function after proximal nerve injuries remains a complex and challenging problem. After a nerve injury, alterations in the affected muscles lead to atrophy, and later degeneration and replacement by fat-fibrous tissues. At present, several different strategies for the preservation of skeletal muscle have been reported, including various sets of physical exercises, muscle massage, physical methods (e.g. electrical stimulation, magnetic field and laser stimulation, low-intensity pulsed ultrasound), medicines (e.g. nutrients, natural and chemical agents, anti-inflammatory and antioxidants, hormones, enzymes and enzyme inhibitors), regenerative medicine (e.g. growth factors, stem cells and microbiota) and surgical procedures (e.g. supercharge end-to-side neurotization). The present review will focus on methods that aimed to minimize the damage to muscles after denervation based on our present knowledge.

Advances of Schwann cells in peripheral nerve regeneration: From mechanism to cell therapy

Peripheral nerve injuries (PNIs) frequently occur due to various factors, including mechanical trauma such as accidents or tool-related incidents, as well as complications arising from diseases like tumor resection. These injuries frequently result in persistent numbness, impaired motor and sensory functions, neuropathic pain, or even paralysis, which can impose a significant financial burden on patients due to outcomes that often fall short of expectations. The most frequently employed clinical treatment for PNIs involves either direct sutures of the severed ends or bridging the proximal and distal stumps using autologous nerve grafts. However, autologous nerve transplantation may result in sensory and motor functional loss at the donor site, as well as neuroma formation and scarring. Transplantation of Schwann cells/Schwann cell-like cells has emerged as a promising cellular therapy to reconstruct the microenvironment and facilitate peripheral nerve regeneration. In this review, we summarize the role of Schwann cells and recent advances in Schwann cell therapy in peripheral nerve regeneration. We summarize current techniques used in cell therapy, including cell injection, 3D-printed scaffolds for cell delivery, cell encapsulation techniques, as well as the cell types employed in experiments, experimental models, and research findings. At the end of the paper, we summarize the challenges and advantages of various cells (including ESCs, iPSCs, and BMSCs) in clinical cell therapy. Our goal is to provide the theoretical and experimental basis for future treatments targeting peripheral nerves, highlighting the potential of cell therapy and tissue engineering as invaluable resources for promoting nerve regeneration.

Delayed repair of the facial nerve and its negative impacts on nerve and muscle regeneration

Background

In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as a coaptation medium and the use of photobiomodulation (PBM), performing functional and histomorphometric analysis of the BBFN and perioral muscles.

Methods

Twenty-eight rats were divided into eight groups using the BBFN bilaterally (the left nerve was used for PBM), namely: G1 - control group, right BBFN (without injury); G2 - control group, left BBFN (without injury + PBM); G3 - Denervated right BBFN (neurotmesis); G4 - Denervated left BBFN (neurotmesis + PBM); G5 - Immediate repair of right BBFN (neurotmesis + HFB); G6 - Immediate repair of left BBFN (neurotmesis + HFB + PBM); G7 - Delayed repair of right BBFN (neurotmesis + HFB); G8 - Delayed repair of left BBFN (neurotmesis + HFB + PBM). Delayed repair occurred after two weeks of denervation. All animals were sacrificed after six weeks postoperatively.

Results

In the parameters of the BBFN, we observed inferior results in the groups with delayed repair, in relation to the groups with immediate repair, with a significant difference (p < 0.05) in the diameter of the nerve fiber, the axon, and the thickness of the myelin sheath of the group with immediate repair with PBM compared to the other experimental groups. In measuring the muscle fiber area, groups G7 (826.4 ± 69.90) and G8 (836.7 ± 96.44) were similar to G5 (882.8 ± 70.51). In the functional analysis, the G7 (4.10 ± 0.07) and G8 (4.12 ± 0.08) groups presented normal parameters.

Conclusion

We demonstrated that delayed repair of BBFN is possible with HFB, but with worse results compared to immediate repair, and that PBM has a positive influence on nerve regeneration results in immediate repair.

Visualization analysis of research frontiers and trends in the treatment of sciatic nerve injury

Objective

To visualize and analyze the literature related to sciatic nerve injury treatment from January 2019 to December 2023, and summarize the current status, hotspots, and development trends of research in this field.

Methods

Using CiteSpace and VOSviewer software, we searched the Web of Science database for literature related to the treatment of sciatic nerve injury. Then we analyzed and plotted visualization maps to show the number of publications, countries, institutions, authors, keywords, references, and journals.

Results

A total of 2,653 articles were included in the English database. The annual number of publications exceeded 230, and the citation frequency increased yearly. The United States and China were identified as high-influence nations in this field. Nantong University was the leading institution in terms of close cooperation among institutions. The authors Wang Yu had the highest number of publications and were highly influential in this field. Keyword analysis and reference Burst revealed a research focus on nerve regeneration and neuropathic pain, which involve regenerative medicine and neural tissue engineering. Chronic pain resulting from sciatic nerve injury often manifests alongside anxiety, depression, cognitive-behavioral disorders, and other issues. Interventions such as stem cells, electrical stimulation, electroacupuncture, total joint replacement, pharmacological interventions, gene therapy, nerve conduits, chitosan scaffolds, and exercise promote nerve repair and alleviate pain. Schwann cells have been the focus of much attention in nerve repair and regeneration. Improving the outcome of sciatic nerve injury is a current research challenge and focus in this field. Based on keyword Burst, nerve conduits and grafts may become a potential research hotspot in the treatment of sciatic nerve injury.

Conclusion

This visual analysis summarizes research trends and developments of sciatic nerve injury treatment and predicts potential research frontiers and hot directions.

A comparison of two versus five epineural sutures to achieve successful polyethylene glycol (PEG) nerve fusion in a rat sciatic nerve repair model

Background

We compared rates of successful polyethylene glycol (PEG) nerve fusion between two epineural suture repairs (2SR) and five epineural suture repairs (5SR) in a rat sciatic nerve transection neurorrhaphy model. We hypothesise that the two and five epineural neural suture repair groups will achieve a similar rate of PEG fusion.

Methods

Twenty-five Lewis rats underwent bilateral sciatic nerve transection. Primary neurorrhaphy (PN) consisting of 2SR in one hind limb and 5SR in the contralateral hind limb was performed utilizing PEG fusion. Successful PEG fusion was confirmed by a distal muscle twitch after nerve stimulation proximal to the nerve fusion site. Sciatic nerve conduction velocity (SNCV) across the repair site and the force generated by tibialis anterior muscle (TAM) contraction were also compared between the 2SR and 5SR groups.

Results

Success rates were 100% for the 2SR and the 5SR groups. No statistically significant differences in SNCV (P = 0.444) or isometric tetanic TAM contractile force (P = 0.820) were observed between 2SR and 5SR in the setting of PEG fusion.

Conclusion

These findings demonstrate no significant difference in successful PEG fusion between the 2SR and 5SR groups. In addition, the findings demonstrate no statistically significant differences in SNCV or isometric tetanic TAM contractile force following sciatic nerve transection when performing a 2SR or 5SR PN in the setting of PEG fusion. Successful PEG fusion can be achieved acutely with either a two or five-epineural suture repair in a rat model.

Building, Breaking, and Repairing Neuromuscular Synapses

A coordinated and complex interplay of signals between motor neurons, skeletal muscle cells, and Schwann cells controls the formation and maintenance of neuromuscular synapses. Deficits in the signaling pathway for building synapses, caused by mutations in critical genes or autoantibodies against key proteins, are responsible for several neuromuscular diseases, which cause muscle weakness and fatigue. Here, we describe the role that four key genes, Agrin, Lrp4, MuSK, and Dok7, play in this signaling pathway, how an understanding of their mechanisms of action has led to an understanding of several neuromuscular diseases, and how this knowledge has contributed to emerging therapies for treating neuromuscular diseases.

[Progress of electrical stimulation to promote peripheral nerve regeneration]

This study reviews the latest progress on the research of electrical stimulation（ES） in peripheral nerve regeneration, summarizes the parameters in preclinical experiments and discusses the effect on nerve regeneration. A detailed description is given in the study of conditioning electrical stimulation and nerve conduit scaffolding technology combined with ES, which have been hotly researched in recent years.

Heterologous fibrin biopolymer as an emerging approach to peripheral nerve repair: a scoping review

Nerve injuries present a substantial challenge within the medical domain due to their prevalent occurrence and significant impact. In nerve injuries, a range of physiopathological and metabolic responses come into play to stabilize and repair the resulting damage. A critical concern arises from the disruption of connections at neuromuscular junctions, leading to profound degeneration and substantial loss of muscle function, thereby hampering motor tasks. While end-to-end neurorrhaphy serves as the established technique for treating peripheral nerve injuries, achieving comprehensive morphofunctional recovery remains a formidable challenge. In pursuit of enhancing the repair process, alternative and supportive methods are being explored. A promising candidate is the utilization of heterologous fibrin biopolymer, a sealant devoid of human blood components. Notably, this biopolymer has showcased its prowess in establishing a stable and protective microenvironment at the site of use in multiple scenarios of regenerative medicine. Hence, this scoping review is directed towards assessing the effects of associating heterologous fibrin biopolymer with neurorrhaphy to treat nerve injuries, drawing upon findings from prior studies disseminated through PubMed/MEDLINE, Scopus, and Web of Science databases. Further discourse delves into the intricacies of the biology of neuromuscular junctions, nerve injury pathophysiology, and the broader utilization of fibrin sealants in conjunction with sutures for nerve reconstruction procedures. The association of the heterologous fibrin biopolymer with neurorrhaphy emerges as a potential avenue for surmounting the limitations associated with traditional sealants while also mitigating degeneration in nerves, muscles, and NMJs post-injury, thereby fostering a more conducive environment for subsequent regeneration. Indeed, queries arise regarding the long-term regenerative potential of this approach and its applicability in reconstructive surgeries for human nerve injuries.

Perspectives on the Novel Multifunctional Nerve Guidance Conduits: From Specific Regenerative Procedures to Motor Function Rebuilding

Peripheral nerve injury potentially destroys the quality of life by inducing functional movement disorders and sensory capacity loss, which results in severe disability and substantial psychological, social, and financial burdens. Autologous nerve grafting has been commonly used as treatment in the clinic; however, its rare donor availability limits its application. A series of artificial nerve guidance conduits (NGCs) with advanced architectures are also proposed to promote injured peripheral nerve regeneration, which is a complicated process from axon sprouting to targeted muscle reinnervation. Therefore, exploring the interactions between sophisticated NGC complexes and versatile cells during each process including axon sprouting, Schwann cell dedifferentiation, nerve myelination, and muscle reinnervation is necessary. This review highlights the contribution of functional NGCs and the influence of microscale biomaterial architecture on biological processes of nerve repair. Progressive NGCs with chemical molecule induction, heterogenous topographical morphology, electroactive, anisotropic assembly microstructure, and self-powered electroactive and magnetic-sensitive NGCs are also collected, and they are expected to be pioneering features in future multifunctional and effective NGCs.

From Text to Insight: A Natural Language Processing-Based Analysis of Topics and Trends in Neurosurgery

BACKGROUND AND OBJECTIVES

Neurosurgical research is a rapidly evolving field, with new research topics emerging continually. To provide a clearer understanding of the evolving research landscape, our study aimed to identify and analyze the prevalent research topics and trends in Neurosurgery.

METHODS

We used BERTopic, an advanced natural language processing-based topic modeling approach, to analyze papers published in the journal Neurosurgery . Using this method, topics were identified based on unique sets of keywords that encapsulated the core themes of each article. Linear regression models were then trained on the topic probabilities to identify trends over time, allowing us to identify "hot" (growing in prominence) and "cold" (decreasing in prominence) topics. We also performed a focused analysis of the trends in the current decade.

RESULTS

Our analysis led to the categorization of 12 438 documents into 49 distinct topics. The topics covered a wide range of themes, with the most commonly identified topics being "Spinal Neurosurgery" and "Treatment of Cerebral Ischemia." The hottest topics of the current decade were "Peripheral Nerve Surgery," "Unruptured Aneurysms," and "Endovascular Treatments" while the cold topics were "Chiari Malformations," "Thromboembolism Prophylaxis," and "Infections."

CONCLUSION

Our study underscores the dynamic nature of neurosurgical research and the evolving focus of the field. The insights derived from the analysis can guide future research directions, inform policy decisions, and identify emerging areas of interest. The use of natural language processing in synthesizing and analyzing large volumes of academic literature demonstrates the potential of advanced analytical techniques in understanding the research landscape, paving the way for similar analyses across other medical disciplines.

Human umbilical cord mesenchymal stem cell-derived exosomes loaded into a composite conduit promote functional recovery after peripheral nerve injury in rats

Complete transverse injury of peripheral nerves is challenging to treat. Exosomes secreted by human umbilical cord mesenchymal stem cells are considered to play an important role in intercellular communication and regulate tissue regeneration. In previous studies, a collagen/hyaluronic acid sponge was shown to provide a suitable regeneration environment for Schwann cell proliferation and to promote axonal regeneration. This three-dimensional (3D) composite conduit contains a collagen/hyaluronic acid inner sponge enclosed in an electrospun hollow poly (lactic-co-glycolic acid) tube. However, whether there is a synergy between the 3D composite conduit and exosomes in the repair of peripheral nerve injury remains unknown. In this study, we tested a comprehensive strategy for repairing long-gap (10 mm) peripheral nerve injury that combined the 3D composite conduit with human umbilical cord mesenchymal stem cell-derived exosomes. Repair effectiveness was evaluated by sciatic functional index, sciatic nerve compound muscle action potential recording, recovery of muscle mass, measuring the cross-sectional area of the muscle fiber, Masson trichrome staining, and transmission electron microscopy of the regenerated nerve in rats. The results showed that transplantation of the 3D composite conduit loaded with human umbilical cord mesenchymal stem cell-derived exosomes promoted peripheral nerve regeneration and restoration of motor function, similar to autograft transplantation. More CD31-positive endothelial cells were observed in the regenerated nerve after transplantation of the loaded conduit than after transplantation of the conduit without exosomes, which may have contributed to the observed increase in axon regeneration and distal nerve reconnection. Therefore, the use of a 3D composite conduit loaded with human umbilical cord mesenchymal stem cell-derived exosomes represents a promising cell-free therapeutic option for the treatment of peripheral nerve injury.

Interactions between Schwann cell and extracellular matrix in peripheral nerve regeneration

Peripheral nerve injuries, caused by various reasons, often lead to severe sensory, motor, and autonomic dysfunction or permanent disability, posing a challenging problem in regenerative medicine. Autologous nerve transplantation has been the gold standard in traditional treatments but faces numerous limitations and risk factors, such as donor area denervation, increased surgical complications, and diameter or nerve bundle mismatches. The extracellular matrix (ECM) is a complex molecular network synthesized and released into the extracellular space by cells residing in tissues or organs. Its main components include collagen, proteoglycans/glycosaminoglycans, elastin, laminin, fibronectin, etc., providing structural and biochemical support to surrounding cells, crucial for cell survival and growth. Schwann cells, as the primary glial cells in the peripheral nervous system, play various important roles. Schwann cell transplantation is considered the gold standard in cell therapy for peripheral nerve injuries, making ECM derived from Schwann cells one of the most suitable biomaterials for peripheral nerve repair. To better understand the mechanisms of Schwann cells and the ECM in peripheral nerve regeneration and their optimal application, this review provides an overview of their roles in peripheral nerve regeneration.

Long-Term Sensory Function 3 years after Minimally Invasive Repair of Pectus Excavatum with Cryoablation

INTRODUCTION

Minimally invasive repair of pectus excavatum (MIRPE) with intercostal nerve cryoablation (Cryo) decreases length of hospitalization and opioid use, but long-term recovery of sensation has been poorly described. The purpose of this study was to quantify long-term hypoesthesia and neuropathic pain after MIRPE with Cryo.

METHODS

A prospective cohort study was conducted single-institution of patients ≤21 years who presented for bar removal. Consented patients underwent chest wall sensory testing and completed neuropathic pain screening. Chest wall hypoesthesia to cold, soft touch, and pinprick were measured as the percent of the treated anterior chest wall surface area (TACWSA); neuropathic pain was evaluated by questionnaire.

RESULTS

The study enrolled 47 patients; 87% male; median age 18.4 years. The median bar dwell time was 2.9 years. A median of 2 bars were placed; 80.9% were secured with pericostal sutures. At enrollment, 46.8% of patients had identifiable chest wall hypoesthesia. The mean percentage of TACWSA with hypoesthesia was 4.7 ± 9.3% (cold), 3.9 ± 7.7% (soft touch), and 5.9 ± 11.8% (pinprick). Hypoesthesia to cold was found in 0 dermatomes in 62%, 1 dermatome in 11%, 2 dermatomes in 17% and ≥3 dermatomes in 11%. T5 was the most common dermatome with hypoesthesia. Neuropathic symptoms were identified by 13% of patients; none required treatment.

CONCLUSION

In long-term follow up after MIRPE with Cryo, 46.8% of patients experienced some chest wall hypoesthesia; the average TACWSA with hypoesthesia was 4-6%. Hypoesthesia was mostly limited to 1-2 dermatomes, most commonly T5. Chronic symptomatic neuropathic pain was rare.

LEVEL OF EVIDENCE

Level IV.

Peripheral nerve stimulation for psoas muscle pain

The psoas muscle is the largest muscle in the lower lumbar spine and is innervated by the ipsilateral lumbar spinal nerve roots (L2-L4). Here, we present a 44-year-old female with left hip pain in the posterolateral aspect of the left hip radiating to the ipsilateral hamstring, and psoas atrophy (based on imaging). She is now reported to have over 50% improvement in pain scores after underdoing temporary peripheral nerve stimulation of the psoas muscle as well as significant improvement in muscle atrophy based on an electromyography (EMG) study. This case study is the first to report documented improvement in muscle atrophy based on EMG after peripheral nerve stimulation of the targeted area.

Effects of Physical Cues on Stem Cell-Derived Extracellular Vesicles toward Neuropathy Applications

The peripheral nervous system undergoes sufficient stress when affected by diabetic conditions, chemotherapeutic drugs, and personal injury. Consequently, peripheral neuropathy arises as the most common complication, leading to debilitating symptoms that significantly alter the quality and way of life. The resulting chronic pain requires a treatment approach that does not simply mask the accompanying symptoms but provides the necessary external environment and neurotrophic factors that will effectively facilitate nerve regeneration. Under normal conditions, the peripheral nervous system self-regenerates very slowly. The rate of progression is further hindered by the development of fibrosis and scar tissue formation, which does not allow sufficient neurite outgrowth to the target site. By incorporating scaffolding supplemented with secretome derived from human mesenchymal stem cells, it is hypothesized that neurotrophic factors and cellular signaling can facilitate the optimal microenvironment for nerve reinnervation. However, conventional methods of secretory vesicle production are low yield, thus requiring improved methods to enhance paracrine secretions. This report highlights the state-of-the-art methods of neuropathy treatment as well as methods to optimize the clinical application of stem cells and derived secretory vesicles for nerve regeneration.