GDNF to the rescue: GDNF delivery effects on motor neurons and nerves, and muscle re-innervation after peripheral nerve injuries

Unique content of breastmilk: neurotrophic growth factors in breastmilk at 2 years and beyond

The aim of our study was to show the presence of neurotrophic factors in breast milk that have a significant impact on neurocognitive development of children aged two years and beyond. Mothers expressed at least 5 mL of breast milk into sterile containers when their children 18, 24, and ≥ 25 months of age, and then specimens were transferred to Eppendorf tubes and stored at -20 °C. One day before the analysis, specimens were kept at +4 °C and then thawed at room temperature to prepare them for analysis. Brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and S100B neurotrophic growth factor levels were analyzed using the sandwich enzyme-linked immunosorbent assay (ELISA) principles. Sixty-two mothers with children aged 18 months were included in the study. The mean age of the mothers was 33.4 (± 0.71) years. Due to the detection limits of the commercial kits, BDNF and S100B analyses could not be conducted. Therefore, only GDNF was analyzed. The presence of GDNF was found in the breast milk samples taken at 18, 24, and ≥ 25 months, and the median (min max) values were 315,505 ng/mL (193,067 750,718), 316,721 ng/mL (161,278 l-752,252), and 564,577 ng/mL (238,528-781,104) respectively. There were no significant differences between GDNF levels of breast milk samples collected from the same mother at the three different time points (18, 24, and ≥ 25 months) (p = 0.278).    Conclusion: Our study was the first to show the presence of neurotrophic factors in the breast milk of mothers with healthy children over one year of age. Our results provide evidence-based data on the importance of breastfeeding until children are at least two years of age. What is Known: • Presence of Brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and S100B neurotrophic growth factor have been shown in the breast milk of mothers whose infants are the first year of life. What is New: • Glial Cell Line-Derived Neurotrophic factors continue to present in breast milk of mothers with children aged 18, 24, and ≥ 25 months, without any significant difference in level between months.

Exploring the Mechanisms of Neuronal Protection by Glial Cell Line-Derived Neurotrophic Factor in Autism Spectrum Disorder

BACKGROUND

A complicated neurological disease known as autism spectrum disorder (ASD) is typified by issues with social interaction, communication, and repetitive behavior. The neural protective mechanisms in ASD are thought to be influenced by genetic variables, including the expression of neurotrophic genes such as glial cell line-derived neurotrophic factor (GDNF).

OBJECTIVE

The aim was to examine the relationship between neuronal protection and cognitive functioning by crosslinking GDNF gene expression and serum levels in individuals with relation to Mini-Mental State Examination (MMSE) scores in ASD patients.

MATERIALS AND METHODS

After getting study approval and informed consent of patients, this case-control study experimental study was conducted for six months between July 2023 and December 2023. The blood samples (5 ml each) were drawn from the study population (n = 140), including 100 ASD patients with a disease course of 30 months based on patients' reports data and 40 healthy controls from four major clinical and hospital settings in Lahore, Karachi, and Bahawalpur from Pakistan. The analytical procedures included nucleic acid extraction, primer design and optimization, and GDNF-targeted real-time quantitative polymerase chain reaction expression analysis. To measure cognitive and behavioral deficits, enzyme-linked immunosorbent assay-based serum GDNF levels (pg/ml) and MMSE scores were compared, concluding the neuronal protection potential of GDNF.

RESULTS

In patients with ASD, lower serum levels of GDNF (9.371 ± 2.388 pg/ml) were linked to more severe behavioral and cognitive deficits confirmed by MMSE scores (13.6 ± 3.5) of ASD patients in comparison with the control group (27.1 ± 2.1). Healthy individuals showed higher relative gene fold expression (11.71) compared to the ASD patients (5.51).

CONCLUSION

There is a notable decrease in GDNF gene expression in people with ASD, which raises the possibility that GDNF is important for both cognitive performance and neuronal protection in these people. GDNF may be a useful biomarker for identifying ASD and comprehending its molecular causes, opening the door for focused treatment approaches.

Recent research of peptide-based hydrogel in nervous regeneration

Neurological disorders exert significantly affect the quality of life for patients, necessitating effective strategies for nerve regeneration. Both traditional autologous nerve transplantation and emerging therapeutic approaches encounter scientific challenges due to the complex nature of the nervous system and the unsuitability of the surrounding environment for cell transplantation. Tissue engineering techniques offer a promising path for neurotherapy. Successful neural tissue engineering relies on modulating cell differentiation behavior and tissue repair by developing biomaterials that mimic the natural extracellular matrix (ECM) and establish a three-dimensional microenvironment. Peptide-based hydrogels have emerged as a potent option among these biomaterials due to their ability to replicate the structure and complexity of the ECM. This review aims to explore the diverse range of peptide-based hydrogels used in nerve regeneration with a specific focus on dipeptide hydrogels, tripeptide hydrogels, oligopeptide hydrogels, multidomain peptides (MDPs), and amphiphilic peptide hydrogels (PAs). Peptide-based hydrogels offer numerous advantages, including biocompatibility, structural diversity, adjustable mechanical properties, and degradation without adverse effects. Notably, hydrogels formed from self-assembled polypeptide nanofibers, derived from amino acids, show promising potential in engineering neural tissues, outperforming conventional materials like alginate, poly(ε-caprolactone), and polyaniline. Additionally, the simple design and cost-effectiveness of dipeptide-based hydrogels have enabled the creation of various functional supramolecular structures, with significant implications for nervous system regeneration. These hydrogels are expected to play a crucial role in future neural tissue engineering research. This review aims to highlight the benefits and potential applications of peptide-based hydrogels, contributing to the advancement of neural tissue engineering.

Enhancing therapeutic potential: Human adipose-derived mesenchymal stem cells modified with recombinant adeno-associated virus expressing VEGF165 gene for peripheral nerve injury

This study aimed to investigate the therapeutic potential of human adipose-derived mesenchymal stem cells (hADSCs) modified with recombinant adeno-associated virus (rAAV) carrying the vascular endothelial growth factor 165 (VEGF165) gene in peripheral nerve injury (PNI). The hADSCs were categorized into blank, control (transduced with rAAV control vector), and VEGF165 (transduced with rAAV VEGF165 vector) groups. Subsequently, Schwann cell differentiation was induced, and Schwann cell markers were assessed. The sciatic nerve injury mouse model received injections of phosphate-buffered saline (PBS group), PBS containing hADSCs (hADSCs group), rAAV control vector (control-hADSCs group), or rAAV VEGF165 vector (VEGF165-hADSCs group) into the nerve defect site. Motor function recovery, evaluated through the sciatic function index (SFI), and nerve regeneration, assessed via toluidine blue staining along with scrutiny of Schwann cell markers and neurotrophic factors, were conducted. Modified hADSCs exhibited enhanced Schwann cell differentiation and elevated expression of Schwann cell markers [S100 calcium-binding protein B (S100B), NGF receptor (NGFR), and glial fibrillary acidic protein (GFAP)]. Mice in the VEGF165-hADSCs group demonstrated improved motor function recovery compared to those in the other three groups, accompanied by increased fiber diameter, axon diameter, and myelin thickness, as well as elevated expression of Schwann cell markers (S100B, NGFR, and GFAP) and neurotrophic factors [mature brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF)] in the distal nerve segment. rAAV-VEGF165 modification enhances hADSC potential in PNI, promoting motor recovery and nerve regeneration. Elevated Schwann cell markers and neurotrophic factors underscore therapy benefits, providing insights for nerve injury strategies.

The Physiologic Basis of Molecular Therapeutics for Peripheral Nerve Injury: A Primer

Peripheral nerve injuries affect a significant number of patients who experience trauma affecting the hand and upper extremity. Improving unsatisfactory outcomes from repair of these injuries remains a clinical challenge despite advancements in microsurgical repair. Imperfections of the nerve regeneration process, including imprecise reinnervation, distal axon degradation, and muscular atrophy, complicate the repair process. However, the capacity for peripheral nerves to regenerate offers an avenue for therapeutic advancement. Regeneration is a temporally and spatially dynamic process coordinated by Schwann cells and neurons among other cell types. Neurotrophic factors are a primary means of controlling cell growth and differentiation in the repair setting. Sustained axon survival and regrowth and consequently functional outcomes of nerve repair in animal models are improved by the administration of neurotrophic factors, including glial cell-derived neurotrophic factor, nerve growth factor, sterile alpha and TIR motif containing 1, and erythropoietin. Targeted and sustained delivery of neurotrophic factors through gelatin-based nerve conduits, multiluminal conduits, and hydrogels have been shown to enhance the innate roles of these factors to promote expedient and accurate peripheral nerve regeneration in animal models. These delivery methods may help address the practical limitations to clinical use of neurotrophic factors, including systemic side effects and the need for carefully timed, precisely localized release schedules. In addition, tacrolimus has also improved peripheral nerve regrowth in animal models and has recently shown promise in addressing human disease. Ultimately, this realm of adjunct pharmacotherapies provides ample promise to improve patient outcomes and advance the field of peripheral nerve repair.

Growth Factors to Enhance Nerve Regeneration: Approaching Clinical Translation

Following nerve injury, growth factors (GFs) are transiently upregulated in injured neurons, proliferating Schwann cells, and denervated muscle and skin. They act on these same cells and tissues to promote nerve regeneration and end-organ reinnervation. Consequently, much attention has been focused on developing GF-based therapeutics. A major barrier to clinical translation of GFs is their short half-life. To provide sustained GF treatment to the affected nerve, muscle, and skin in a safe and practical manner, engineered drug delivery systems are needed. This review highlights recent advancements in GF-based therapeutics and discusses the remaining hurdles for clinical translation.

Runx2 regulates peripheral nerve regeneration to promote Schwann cell migration and re-myelination

JOURNAL/nrgr/04.03/01300535-202407000-00038/figure1/v/2023-11-20T171125Z/r/image-tiff

Runx2 is a major regulator of osteoblast differentiation and function; however, the role of Runx2 in peripheral nerve repair is unclear. Here, we analyzed Runx2 expression following injury and found that it was specifically up-regulated in Schwann cells. Furthermore, using Schwann cell-specific Runx2 knockout mice, we studied peripheral nerve development and regeneration and found that multiple steps in the regeneration process following sciatic nerve injury were Runx2-dependent. Changes observed in Runx2 knockout mice include increased proliferation of Schwann cells, impaired Schwann cell migration and axonal regrowth, reduced re-myelination of axons, and a block in macrophage clearance in the late stage of regeneration. Taken together, our findings indicate that Runx2 is a key regulator of Schwann cell plasticity, and therefore peripheral nerve repair. Thus, our study shows that Runx2 plays a major role in Schwann cell migration, re-myelination, and peripheral nerve functional recovery following injury.

Mesenchymal stem cells' "garbage bags" at work: Treating radial nerve injury with mesenchymal stem cell-derived exosomes

Unlike central nervous system injuries, peripheral nerve injuries (PNIs) are often characterized by more or less successful axonal regeneration. However, structural and functional recovery is a senile process involving multifaceted cellular and molecular processes. The contemporary treatment options are limited, with surgical intervention as the gold-standard method; however, each treatment option has its associated limitations, especially when the injury is severe with a large gap. Recent advancements in cell-based therapy and cell-free therapy approaches using stem cell-derived soluble and insoluble components of the cell secretome are fast-emerging therapeutic approaches to treating acute and chronic PNI. The recent pilot study is a leap forward in the field, which is expected to pave the way for more enormous, systematic, and well-designed clinical trials to assess the therapeutic efficacy of mesenchymal stem cell-derived exosomes as a bio-drug either alone or as part of a combinatorial approach, in an attempt synergize the best of novel treatment approaches to address the complexity of the neural repair and regeneration.

Strategies for Treating Traumatic Neuromas with Tissue-Engineered Materials

Neuroma, a pathological response to peripheral nerve injury, refers to the abnormal growth of nerve tissue characterized by disorganized axonal proliferation. Commonly occurring after nerve injuries, surgeries, or amputations, this condition leads to the formation of painful nodular structures. Traditional treatment options include surgical excision and pharmacological management, aiming to alleviate symptoms. However, these approaches often offer temporary relief without addressing the underlying regenerative challenges, necessitating the exploration of advanced strategies such as tissue-engineered materials for more comprehensive and effective solutions. In this study, we discussed the etiology, molecular mechanisms, and histological morphology of traumatic neuromas after peripheral nerve injury. Subsequently, we summarized and analyzed current nonsurgical and surgical treatment options, along with their advantages and disadvantages. Additionally, we emphasized recent advancements in treating traumatic neuromas with tissue-engineered material strategies. By integrating biomaterials, growth factors, cell-based approaches, and electrical stimulation, tissue engineering offers a comprehensive solution surpassing mere symptomatic relief, striving for the structural and functional restoration of damaged nerves. In conclusion, the utilization of tissue-engineered materials has the potential to significantly reduce the risk of neuroma recurrence after surgical treatment.

Skeletal muscle as a molecular and cellular biomarker of disease progression in amyotrophic lateral sclerosis: a narrative review

Amyotrophic lateral sclerosis is a fatal multisystemic neurodegenerative disease with motor neurons being a primary target. Although progressive weakness is a hallmark feature of amyotrophic lateral sclerosis, there is considerable heterogeneity, including clinical presentation, progression, and the underlying triggers for disease initiation. Based on longitudinal studies with families harboring amyotrophic lateral sclerosis-associated gene mutations, it has become apparent that overt disease is preceded by a prodromal phase, possibly in years, where compensatory mechanisms delay symptom onset. Since 85-90% of amyotrophic lateral sclerosis is sporadic, there is a strong need for identifying biomarkers that can detect this prodromal phase as motor neurons have limited capacity for regeneration. Current Food and Drug Administration-approved therapies work by slowing the degenerative process and are most effective early in the disease. Skeletal muscle, including the neuromuscular junction, manifests abnormalities at the earliest stages of the disease, before motor neuron loss, making it a promising source for identifying biomarkers of the prodromal phase. The accessibility of muscle through biopsy provides a lens into the distal motor system at earlier stages and in real time. The advent of "omics" technology has led to the identification of numerous dysregulated molecules in amyotrophic lateral sclerosis muscle, ranging from coding and non-coding RNAs to proteins and metabolites. This technology has opened the door for identifying biomarkers of disease activity and providing insight into disease mechanisms. A major challenge is correlating the myriad of dysregulated molecules with clinical or histological progression and understanding their relevance to presymptomatic phases of disease. There are two major goals of this review. The first is to summarize some of the biomarkers identified in human amyotrophic lateral sclerosis muscle that have a clinicopathological correlation with disease activity, evidence of a similar dysregulation in the SOD1G93A mouse during presymptomatic stages, and evidence of progressive change during disease progression. The second goal is to review the molecular pathways these biomarkers reflect and their potential role in mitigating or promoting disease progression, and as such, their potential as therapeutic targets in amyotrophic lateral sclerosis.

GDNF facilitates the differentiation of ADSCs to Schwann cells and enhances nerve regeneration through GDNF/MTA1/Hes1 axis

Adipose tissue-derived stem cells (ADSCs) are a kind of stem cells with multi-directional differentiation potential, which mainly restore tissue repair function and promote cell regeneration. It can be directionally differentiated into Schwann-like cells to promote the repair of peripheral nerve injury. Glial cell line-derived neurotrophic factor (GDNF) plays an important role in the repair of nerve injury, but the underlying mechanism remains unclear, which seriously limits its further application.The study aimed to identify the molecular mechanism by which overexpression of glial cell line-derived neurotrophic factor (GDNF) facilitates the differentiation of ADSCs into Schwann cells, enhancing nerve regeneration after injury. In vitro, ADSCs overexpressing GDNF for 48 h exhibited changes in their morphology, with 80% of the cells having two or more prominences. Compared with that of ADSCs, GDNF-ADSCs exhibited increased expression of the Schwann cell marker S100, nerve damage repair-related factors.ADSC cells in normal culture and ADSC cells were overexpressing GDNF(GDNF-ADSCs) were analysed using TMT-Based Proteomic Analysis and revealed a significantly higher expression of MTA1 in GDNF-ADSCs than in control ADSCs. Hes1 expression was significantly higher in GDNF-ADSCs than in ADSCs and decreased by MTA1 silencing, along with a simultaneous decrease in the expression of S100 and nerve damage repair factors. These findings indicate that GDNF promotes the differentiation of ADSCs into Schwann cells and induces factors that accelerate peripheral nerve damage repair.

Platelet-rich plasma-derived exosomes boost mesenchymal stem cells to promote peripheral nerve regeneration

Peripheral nerve injury (PNI) remains a severe clinical problem with debilitating consequences. Mesenchymal stem cell (MSC)-based therapy is promising, but the problems of poor engraftment and insufficient neurotrophic effects need to be overcome. Herein, we isolated platelet-rich plasma-derived exosomes (PRP-Exos), which contain abundant bioactive molecules, and investigated their potential to increase the regenerative capacity of MSCs. We observed that PRP-Exos significantly increased MSC proliferation, viability, and mobility, decreased MSC apoptosis under stress, maintained MSC stemness, and attenuated MSC senescence. In vivo, PRP-Exo-treated MSCs (pExo-MSCs) exhibited an increased retention rate and heightened therapeutic efficacy, as indicated by increased axonal regeneration, remyelination, and recovery of neurological function in a PNI model. In vitro, pExo-MSCs coculture promoted Schwann cell proliferation and dorsal root ganglion axon growth. Moreover, the increased neurotrophic behaviour of pExo-MSCs was mediated by trophic factors, particularly glia-derived neurotrophic factor (GDNF), and PRP-Exos activated the PI3K/Akt signalling pathway in MSCs, leading to the observed phenotypes. These findings demonstrate that PRP-Exos may be novel agents for increasing the ability of MSCs to promote neural repair and regeneration in patients with PNI.

Utilization of the Rat Tibial Nerve Transection Model to Evaluate Cellular and Molecular Mechanisms Underpinning Denervation-Mediated Muscle Injury

Peripheral nerve injury denervates muscle, resulting in muscle paralysis and atrophy. This is reversible if timely muscle reinnervation occurs. With delayed reinnervation, the muscle's reparative ability declines, and muscle-resident fibro-adipogenic progenitor cells (FAPs) proliferate and differentiate, inducing fibro-fatty muscle degradation and thereby physical disability. The mechanisms by which the peripheral nerve regulates FAPs expansion and differentiation are incompletely understood. Using the rat tibial neve transection model, we demonstrated an increased FAPs content and a changing FAPs phenotype, with an increased capacity for adipocyte and fibroblast differentiation, in gastrocnemius muscle post-denervation. The FAPs response was inhibited by immediate tibial nerve repair with muscle reinnervation via neuromuscular junctions (NMJs) and sensory organs (e.g., muscle spindles) or the sensory protection of muscle (where a pure sensory nerve is sutured to the distal tibial nerve stump) with reinnervation by muscle spindles alone. We found that both procedures reduced denervation-mediated increases in glial-cell-line-derived neurotrophic factor (GDNF) in muscle and that GDNF promoted FAPs adipogenic and fibrogenic differentiation in vitro. These results suggest that the peripheral nerve controls FAPs recruitment and differentiation via the modulation of muscle GDNF expression through NMJs and muscle spindles. GDNF can serve as a therapeutic target in the management of denervation-induced muscle injury.

Exogenous GDNF promotes peripheral facial nerve regeneration in rats through the PI3K/AKT/mTOR signaling pathway

Facial nerve regeneration still lacks a well-defined and practical clinical intervention. The survival of central facial motoneuron is a critical component in the successful peripheral facial nerve regeneration. Endogenous GDNF is vital for facial nerve regeneration according to earlier investigations. Nevertheless, the low endogenous GDNF level makes it challenging to achieve therapeutic benefits. Thus, we crushed the main trunk of facial nerve in SD rats to provide a model of peripheral facial paralysis, and we administered exogenous GDNF and Rapa treatments. We observed changes in the animal behavior scores, the morphology of facial nerve and buccinator muscle, the electrophysiological of facial nerve, and the expression of GDNF, GAP-43, and PI3K/AKT/mTOR signaling pathway-related molecules in the facial motoneurons. We discovered that GDNF could boost axon regeneration, hasten the recovery of facial paralysis symptoms and nerve conduction function, and increase the expression of GDNF, GAP-43, and PI3K/AKT/mTOR signaling pathway-related molecules in the central facial motoneurons. Therefore, exogenous GDNF injection into the buccinator muscle can enhance facial nerve regeneration following crushing injury and protect facial neurons via the PI3K/AKT/mTOR signaling pathway. This will offer a fresh perspective and theoretical foundation for the management of clinical facial nerve regeneration.

MSCs overexpressing GDNF restores brain structure and neurological function in rats with intracerebral hemorrhage

Mesenchymal stem cells (MSCs) have been applied in transplantation to treat intracerebral hemorrhage (ICH) but with limited efficacy. Accumulated evidence has shown that glial cell-derived neurotrophic factor (GDNF) plays a crucial part in neuronal protection and functional recovery of the brain after ICH; however, GDNF has difficulty crossing the blood-brain barrier, which limits its application. In this study, we investigated the influences of MSCs overexpressing GDNF (MSCs/GDNF) on the brain structure as well as gait of rats after ICH and explored the possible mechanisms. We found that cell transplantation could reverse the neurological dysfunction and brain damage caused by ICH to a certain extent, and MSCs/GDNF transplantation was superior to MSCs transplantation. Moreover, Transplantation of MSCs overexpressing GDNF effectively reduced the volume of bleeding foci and increased the level of glucose uptake in rats with ICH, which could be related to improving mitochondrial quality. Furthermore, GDNF produced by transplanted MSCs/GDNF further inhibited neuroinflammation, improved mitochondrial quality and function, promoted angiogenesis and the survival of neurons and oligodendrocytes, and enhanced synaptic plasticity in ICH rats when compared with simple MSC transplantation. Overall, our data indicate that GDNF overexpression heightens the curative effect of MSC implantation in treating rats following ICH.

Biodegradable Nerve Guide with Glial Cell Line-Derived Neurotrophic Factor Improves Recovery After Facial Nerve Injury in Rats

Background: Bioengineered nerve guides with glial cell line-derived neurotrophic factor (GDNF) support recovery after facial nerve injury by acting as regenerative scaffolds. Objective: To compare functional, electrophysiological, and histological outcomes after repair of rat facial nerve transection in control, empty nerve guide, and nerve guide with GDNF conditions. Methods: Rats underwent transection and primary repair of the buccal branch of the facial nerve and were divided into (1) transection and repair only, (2) transection and repair augmented with empty guide, (3) transection and repair augmented with GDNF-guide groups. Weekly measurements of the whisking movements were recorded. At 12 weeks, compound muscle action potentials (CMAPs) at the whisker pad were assessed, and samples were collected for histomorphometric analysis. Results: Rats in GDNF-guide group displayed the earliest peak in normalized whisking amplitude. CMAPs were significantly higher after GDNF-guide placement. Mean fiber surface area of the target muscle, axonal count of the injured branch, and the number of Schwann cells were highest with GDNF guides. Conclusion: The biodegradable nerve guide containing double-walled GDNF microspheres enhanced recovery after facial nerve transection and primary repair.

Mesenchymal stem cells derived from bone marrow and adipose tissue for repairing acute sciatic nerve injury in a rabbit model

Peripheral nerve injury is one of the common disabling clinical conditions and around 50% of the cases end up in permanent impairment. Due to the lack of effective treatment options regenerative medicine employing stem cells is being evaluated. The presented study evaluated and compared regeneration potential of mesenchymal stem cells (MSCs) derived from bone marrow (BM) and adipose tissue (AD) in acute rabbit sciatic nerve injury (axonotmesis) model. A total of n = 54 grey giant rabbits were made subject of the study and divided equally into 3 groups: Control, BM-MSCs in Collagen I and AD-MSCs in Collagen I as per the treatment given. Iliac crest BM and omental AD was harvested from the same donor for isolation and culture of MSCs. The repair of sciatic nerve injury was evaluated on days 60 and 90. The clinical and histopathological scores and SEM morphology was better in cell treated groups as compared to the control. Morphology and histological studies revealed injured nerve in different levels of regenerative process. Gene expression was more than double for N-Cadherin in cell treated groups as compared to the control, especially at day 60. Between cell treated groups, BM-MSCs group showed better response as compared to the AD-MSCs, although statistically non-significant (p > 0.05). Incomplete nerve regeneration observed under various diagnostic parameters was in compliance to the incomplete clinical recovery at day 90. It was concluded that MSCs may improve sciatic nerve healing but fall short of complete regeneration at day 90, although BM-MSCs may have an edge over AD-MSCs.

Cellular Localization and Distribution of TGF-β1, GDNF and PDGF-BB in the Adult Primate Central Nervous System

The available data on the localization of transforming growth factor beta1 (TGF-β1), glial cell line-derived neurotrophic factor (GDNF), and platelet-derived growth factor-BB (PDGF-BB) in the adult primate and human central nervous system (CNS) are limited and lack comprehensive and systematic information. This study aimed to investigate the cellular localization and distribution of TGF-β1, GDNF, and PDGF-BB in the CNS of adult rhesus macaque (Macaca mulatta). Seven adult rhesus macaques were included in the study. The protein levels of TGF-β1, PDGF-BB, and GDNF in the cerebral cortex, cerebellum, hippocampus, and spinal cord were analyzed by western blotting. The expression and location of TGF-β1, PDGF-BB, and GDNF in the brain and spinal cord was examined by immunohistochemistry and immunofluorescence staining, respectively. The mRNA expression of TGF-β1, PDGF-BB, and GDNF was detected by in situ hybridization. The molecular weight of TGF-β1, PDGF-BB, and GDNF in the homogenate of spinal cord was 25 KDa, 30 KDa, and 34 KDa, respectively. Immunolabeling revealed GDNF was ubiquitously distributed in the cerebral cortex, hippocampal formation, basal nuclei, thalamus, hypothalamus, brainstem, cerebellum, and spinal cord. TGF-β1 was least distributed and found only in the medulla oblongata and spinal cord, and PDGF-BB expression was also limited and present only in the brainstem and spinal cord. Besides, TGF-β1, PDGF-BB, and GDNF were localized in the astrocytes and microglia of spinal cord and hippocampus, and their expression was mainly found in the cytoplasm and primary dendrites. The mRNA of TGF-β1, PDGF-BB, and GDNF was localized to neuronal subpopulations in the spinal cord and cerebellum. These findings suggest that TGF-β1, GDNF and PDGF-BB may be associated with neuronal survival, neural regeneration and functional recovery in the CNS of adult rhesus macaques, providing the potential insights into the development or refinement of therapies based on these factors.

Research progress on the reduced neural repair ability of aging Schwann cells

Peripheral nerve injury (PNI) is associated with delayed repair of the injured nerves in elderly patients, resulting in loss of nerve function, chronic pain, muscle atrophy, and permanent disability. Therefore, the mechanism underlying the delayed repair of peripheral nerves in aging patients should be investigated. Schwann cells (SCs) play a crucial role in repairing PNI and regulating various nerve-repair genes after injury. SCs also promote peripheral nerve repair through various modalities, including mediating nerve demyelination, secreting neurotrophic factors, establishing Büngner bands, clearing axon and myelin debris, and promoting axon remyelination. However, aged SCs undergo structural and functional changes, leading to demyelination and dedifferentiation disorders, decreased secretion of neurotrophic factors, impaired clearance of axonal and myelin debris, and reduced capacity for axon remyelination. As a result, aged SCs may result in delayed repair of nerves after injury. This review article aimed to examine the mechanism underlying the diminished neural repair ability of aging SCs.

Experimental study on the repair of peripheral nerve injuries via simultaneously coapting the proximal and distal ends of peripheral nerves to the side of nearby intact nerves

Introduction

Peripheral nerve defect is a difficult disease to treat in clinical practice. End-to-side anastomosis is a useful method to treat it. At present, the end-to-side anastomosis method does not involve the proximal nerve, which results in a waste of proximal donor nerves, and even the formation of traumatic neuromas at the proximal end. The patients suffer from traumatic neuralgia and the curative effect is unsatisfactory.

Methods

In this study, an improved end-to-side anastomosis technique was proposed in this study: both the proximal and distal ends of the damaged common peroneal nerve were sutured to an adjacent normal tibial nerve. Moreover, the possible role and mechanism of the proposed technique were explained at the physiological and anatomical levels. In this study, a 10 mm common peroneal nerve defect was made in SD rats, and the rats were randomly divided into three groups. In Group I, the distal end of the common peroneal nerve was attached end-to-side to the fenestrated tibial nerve adventitia, and the proximal end was ligated and fixed in the nearby muscle. In Group II, the tibial nerve adventitia was fenestrated and the epineurial end-to-end anastomosis surgery was performed to suture the proximal and distal ends of the common peroneal nerve. Rats in Group III were taken as control and received sham operation. Twelve weeks after the operation, the recovery of the repaired nerve and distal effector functions were examined by the sciatic functional index, electrophysiology, osmic acid staining, the muscle wet weight ratio, and the muscle fiber cross-sectional area.

Results

It was found that these results in Group II were similar to those in Group III, but better than those in Group I. Through retrograde tracing of neurons and Electrophysiological examination in Group II, the study also found that the proximal common peroneal nerve also could establish a connection with tibialis anterior, even gastrocnemius.

Discussion

Therefore, it is inferred that fostering both the proximal and distal ends of defective peripheral nerves on normal peripheral nerves using the end-to-side anastomosis technique is a more effective approach to repairing injured nerves.

α-Asarone attenuates chronic sciatica by inhibiting peripheral sensitization and promoting neural repair

This study explored the therapeutic effect of α-asarone on chronic sciatica. Thirty-two Sprague-Dawley (SD) rats were divided into four groups: the sham group, chronic constriction injury (CCI) group, pregabalin group, and α-asarone group. Hot hyperalgesia was induced after the CCI operation, and α-asarone was found to relieve chronic neuralgia. Furthermore, α-asarone reduced IL1β, IL6, TNF-α, CRP, and LPS levels and increased IL10 levels in serum. α-Asarone decreased the protein levels of TRPA1, TRPM8, and TRPV1-4 and the mRNA levels of TRPA1, TRPM8, TRPV1-4, IL1β, and TNF-α in dorsal root ganglion neurons. In the sciatic nerve, α-asarone treatment reduced the number of inflammatory cells and promoted the proliferation of Schwann cells, favouring recovery of the nerve structure. In cellular experiments, LPS induced Schwann cell apoptosis via TLR4/p38MAPK signalling; α-asarone attenuated LPS-induced Schwann cell apoptosis by decreasing TLR4, p-p38MAPK, cleaved-caspase3, and cleaved-caspase7 levels and increasing Bcl-2 and Bcl-xl expression. Overall, these findings suggest that α-asarone relieves chronic sciatica by decreasing the levels of inflammatory factors, inhibiting peripheral sensitization, and favouring the repair of damaged nerves.

Adaptive Triboelectric Nanogenerators for Long-Term Self-Treatment: A Review

Triboelectric nanogenerators (TENGs) were initially invented as an innovative energy-harvesting technology for scavenging mechanical energy from our bodies or the ambient environment. Through adaptive customization design, TENGs have also become a promising player in the self-powered wearable medical market for improving physical fitness and sustaining a healthy lifestyle. In addition to simultaneously harvesting our body's mechanical energy and actively detecting our physiological parameters and metabolic status, TENGs can also provide personalized medical treatment solutions in a self-powered modality. This review aims to cover the recent advances in TENG-based electronics in clinical applications, beginning from the basic working principles of TENGs and their general operation modes, continuing to the harvesting of bioenergy from the human body, and arriving at their adaptive design toward applications in chronic disease diagnosis and long-term clinical treatment. Considering the highly personalized usage scenarios, special attention is paid to customized modules that are based on TENGs and support complex medical treatments, where sustainability, biodegradability, compliance, and bio-friendliness may be critical for the operation of clinical systems. While this review provides a comprehensive understanding of TENG-based clinical devices that aims to reach a high level of technological readiness, the challenges and shortcomings of TENG-based clinical devices are also highlighted, with the expectation of providing a useful reference for the further development of such customized healthcare systems and the transfer of their technical capabilities into real-life patient care.

Negative neuromuscular and functional repercussion of forced swimming after axonotmesis

Peripheral nerve injuries are cause of sensory disturbances and in functional abilities, and are associated personal and social costs. Strategies that maximize nerve regeneration and functional recovery are necessary, the exercise is an option. This study evaluated the effects of forced swimming exercise on neuromuscular histomorphometry and on functional recovery in a median nerve crush model. Sixteen Wistar rats underwent median nerve crush and were divided into control group (CG) and swimming group (SG). The forced swimming protocol started one week after the injury and was performed for 1 hr a day, 5 days per week, for 2 weeks. The rats swam with an overload of 5% and 10% of body weight in the first and second week, respectively. The functional recovery was assessed in three moments using the grasping test. On day 21, fragments of the median nerve and of the forearm flexors muscles were removed for histomorphometric analysis. The SG had functional recovery impaired (P<0.001) and presented lower myelinated fibers number, fiber and axon minimal diameter, myelin thickness and g-ratio in the proximal e distal segments of the median nerve (P<0.005) and area muscle fiber (P<0.005) than CG. Also, the SG presented a number of capillaries in the proximal segments of the median nerve greater than CG (P<0.005). The exercise protocol used in this study impaired the regeneration of the median nerve and negatively influenced the functional recovery.

Changes of Functional, Morphological, and Inflammatory Reactions in Spontaneous Peripheral Nerve Reinnervation after Thermal Injury

In recent decades, the use of energy-based devices has substantially increased the incidence of iatrogenic thermal injury to nerves (cauterization, etc.). While recovery of the nerve after thermal injury is important, the changes in neural structure, function, and peripheral inflammatory reactions postinjury remain unclear. This study is aimed at demonstrating the changes mentioned above during the acute, subacute, and chronic stages of nerve reinnervation after thermal injury. Spontaneous reinnervation was evaluated, including the neural structures, nerve conduction abilities, and muscle regeneration. These effects vary depending on the severity of thermal injury (slight, moderate, and severe). Peripheral inflammatory reactions, as impediments to reinnervation, were found in significant numbers 3 days after thermal injury, exhibiting high expression of IL-1β and TNF-α, but low expression of IL-10. Our findings reveal the pathogenesis of peripheral nerve reinnervation after thermal injury, which will assist in selecting appropriate treatments in further research.