Use of the CatWalk gait analysis system to assess functional recovery in rodent models of peripheral nerve injury - a systematic review

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

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

Chronic, Battery-Free, Fully Implantable Multimodal Spinal Cord Stimulator for Pain Modulation in Small Animal Models

Spinal cord stimulation (SCS) for chronic pain management is an invasive therapy involving surgical implantation of electrodes into spinal epidural space. While the clinical value and mechanistic action of the therapy is debated considerably in recent years, preclinical chronic studies employing rodent models can provide invaluable insights regarding the balance between efficacy and complications as well as mechanistic understanding of SCS therapy. However, current rodent compatible devices require tethered power delivery or bulky batteries, severely limiting the ability to probe long-term efficacy of SCS therapy. This work introduces a tether-free, small-footprint, fully implantable, battery-free SCS device compatible with rodent models, capable of delivering electrical stimulation to the spinal cord at a wide range of frequency, amplitude, and period via wireless communication adjustable on-demand without direct interaction with the animal. The presented device features capabilities of clinical SCS devices, with materials and processes amendable to scalable fabrication at a cost suitable for one-time use enabling high N studies. In this proof of concept, the implantable device serves to assess therapeutic efficacy of various clinically relevant SCS paradigms in alleviating neuropathic pain. This technology offers chronic stability and the potential to serve as the foundation for future research into the development of SCS therapeutic systems.

Impairment of theta oscillations in the hippocampal CA1 region may mediate age-dependent movement alternations in the 5xFAD mouse model of Alzheimer's disease

Clinical evidences indicate that multifaceted gait abnormalities may manifest in Alzheimer's disease (AD) patients, which are associated with cognitive decline. Although the correlation between hippocampal theta power and locomotion has been known for a long time, the mechanisms by how hippocampal impairment participates in the altered gait seen in AD is not fully understood. To explore the manifestations of gait disorders in AD, we characterized gait performance in 3-, 6-, and 9-month-old male 5xFAD and control mice in the semi-automated, highly sensitive, Catwalk XT system. The 5xFAD mice displayed a decrease in kinetic parameters (average speed and cadence), and spatial parameters (paw area), while the temporal parameters (stance and swing time) were significantly increased. The parameters of interlimb coordination also displayed deficits. The majority of impairment variables related to the slow speed in 5xFAD mice at 9-month-old. We further explored the theta oscillations in the brain by in vivo tetrode recording of the hippocampal CA1. The results showed that the theta oscillations reduced in the hippocampal CA1 of 5xFAD mice, which related to the gait impairments. In conclusion, gait impairments started at 6 months of age, manifested at 9 months of age in 5xFAD mice. A reduction in theta oscillation power of the hippocampal CA1 may be responsible for the gait impairments.

Multivariate description of gait changes in a mouse model of peripheral nerve injury and trauma

OBJECTIVE

Animal models of nerve injury are important for studying nerve injury and repair, particularly for interventions that cannot be studied in humans. However, the vast majority of gait analysis in animals has been limited to univariate analysis even though gait data is highly multi-dimensional. As a result, little is known about how various spatiotemporal components of the gait relate to each other in the context of peripheral nerve injury and trauma. We hypothesize that a multivariate characterization of gait will reveal relationships among spatiotemporal components of gait with biological relevance to peripheral nerve injury and trauma. We further hypothesize that legitimate relationships among said components will allow for more accurate classification among distinct gait phenotypes than if attempted with univariate analysis alone.

METHODS

DigiGait data was collected of mice across groups representing increasing degrees of damage to the neuromusculoskeletal sequence of gait; that is (a) healthy controls, (b) nerve damage only via total nerve transection + reconnection of the femoral and sciatic nerves, and (c) nerve, muscle, and bone damage via total hind-limb transplantation. Multivariate relationships among the 30+ spatiotemporal measures were evaluated using exploratory factor analysis and forward feature selection to identify the features and latent factors that best described gait phenotypes. The identified features were then used to train classifier models and compared to a model trained with features identified using only univariate analysis.

RESULTS

10-15 features relevant to describing gait in the context of increasing degrees of traumatic peripheral nerve injury were identified. Factor analysis uncovered relationships among the identified features and enabled the extrapolation of a set of latent factors that further described the distinct gait phenotypes. The latent factors tied to biological differences among the groups (e.g. alterations to the anatomical configuration of the limb due to transplantation or aberrant fine motor function due to peripheral nerve injury). Models trained using the identified features generated values that could be used to distinguish among pathophysiological states with high statistical significance (p < .001) and accuracy (>80%) as compared to univariate analysis alone.

CONCLUSION

This is the first performance evaluation of a multivariate approach to gait analysis and the first demonstration of superior performance as compared to univariate gait analysis in animals. It is also the first study to use multivariate statistics to characterize and distinguish among different gradations of gait deficit in animals. This study contributes a comprehensive, multivariate characterization pipeline for application in the study of any pathologies in which gait is a quantitative translational outcome metric.

TAM receptors mediate the Fpr2-driven pain resolution and fibrinolysis after nerve injury

Nerve injury causes neuropathic pain and multilevel nerve barrier disruption. Nerve barriers consist of perineurial, endothelial and myelin barriers. So far, it is unclear whether resealing nerve barriers fosters pain resolution and recovery. To this end, we analysed the nerve barrier property portfolio, pain behaviour battery and lipidomics for precursors of specialized pro-resolving meditators (SPMs) and their receptors in chronic constriction injury of the rat sciatic nerve to identify targets for pain resolution by resealing the selected nerve barriers. Of the three nerve barriers-perineurium, capillaries and myelin-only capillary tightness specifically against larger molecules, such as fibrinogen, recuperated with pain resolution. Fibrinogen immunoreactivity was elevated in rats not only at the time of neuropathic pain but also in nerve biopsies from patients with (but not without) painful polyneuropathy, indicating that sealing of the vascular barrier might be a novel approach in pain treatment. Hydroxyeicosatetraenoic acid (15R-HETE), a precursor of aspirin-triggered lipoxin A4, was specifically upregulated at the beginning of pain resolution. Repeated local application of resolvin D1-laden nanoparticles or Fpr2 agonists sex-independently resulted in accelerated pain resolution and fibrinogen removal. Clearing macrophages (Cd206) were boosted and fibrinolytic pathways (Plat) were induced, while inflammation (Tnfα) and inflammasomes (Nlrp3) were unaffected by this treatment. Blocking TAM receptors (Tyro3, Axl and Mer) and tyrosine kinase receptors linking haemostasis and inflammation completely inhibited all the effects. In summary, nanoparticles can be used as transporters for fleeting lipids, such as SPMs, and therefore expand the array of possible therapeutic agents. Thus, the Fpr2-Cd206-TAM receptor axis may be a suitable target for strengthening the capillary barrier, removing endoneurial fibrinogen and boosting pain resolution in patients with chronic neuropathic pain.

Therapeutic Potential of Vitamin B Complex in Peripheral Nerve Injury Recovery: An Experimental Rat Model Study

Objectives: Vitamin B complexes are frequently used in clinical practice for peripheral nerve trauma. However, there is a lack of scientific data on their effectiveness. This study aims to investigate the impact of the vitamin B complex on nerve recovery in a rat model of peripheral nerve paralysis. Materials and Methods: Sixty male Wistar Albino rats were divided into six groups. Models of nerve injury, including blunt trauma, nerve incision, and autograft, were performed on all rats approximately 1 cm distal to the sciatic notch. B-complex vitamins were injected intraperitoneally at 0.2 mL/day to the treatment groups. The control groups were given 0.2 mL/day saline. After 1 month, the study was terminated, electromyography (EMG) was performed to measure the conduction velocity, and nerve tissue was taken from the repair line. The sciatic function indexes (SFIs) were calculated and analyzed. The histopathological samples were stained with hematoxylin and eosin and Toluidine blue and examined with a light microscope. Pathologically, myelination, fibrosis, edema, and mast cell densities in the nervous tissue were evaluated. Results: The vitamin B treatment groups demonstrated significant improvements in SFI compared to the control groups, indicating functional improvement in nerve damage (p < 0.05). In the nerve graft group, the vitamin B group showed a shorter latency, higher velocity, and larger peak-to-peak compared to the controls (p < 0.05). In the nerve transection group, the vitamin B group had better latency, velocity, and peak-to-peak values than the controls (p < 0.05). In the crush injury group, the vitamin B group exhibited an improved latency, velocity, and peak-to-peak compared to the controls (p < 0.05). Better myelination, less fibrosis, edema, and mast cells were also in the vitamin B group (p < 0.05). Conclusions: Vitamin B treatment significantly improves nerve healing and function in peripheral nerve injuries. It enhances nerve conduction, reduces fibrosis, and promotes myelination, indicating its therapeutic potential in nerve regeneration.

Automatic detection of foot-strike onsets in a rhythmic forelimb movement

Rhythmic movement is the fundamental motion dynamics characterized by repetitive patterns. Precisely defining onsets in rhythmic movement is essential for a comprehensive analysis of motor functions. Our study introduces an automated method for detecting rat's forelimb foot-strike onsets using deep learning tools. This method demonstrates high accuracy of onset detection by combining two techniques using joint coordinates and behavioral confidence scale. The analysis extends to neural oscillatory responses in the rat's somatosensory cortex, validating the effectiveness of our combined approach. Our technique streamlines experimentation, demanding only a camera and GPU-accelerated computer. This approach is applicable across various contexts and promotes our understanding of brain functions during rhythmic movements.

Loss of Elp1 in cerebellar granule cell progenitors models ataxia phenotype of Familial Dysautonomia

Familial Dysautonomia (FD) is an autosomal recessive disorder caused by a splice site mutation in the gene ELP1, which disproportionally affects neurons. While classically characterized by deficits in sensory and autonomic neurons, neuronal defects in the central nervous system have also been described. Although ELP1 expression remains high in the normal developing and adult cerebellum, its role in cerebellar development is unknown. To explore the role of Elp1 in the cerebellum, we knocked out Elp1 in cerebellar granule cell progenitors (GCPs) and examined the outcome on animal behavior and cellular composition. We found that GCP-specific conditional knockout of Elp1 (Elp1cKO) resulted in ataxia by 8 weeks of age. Cellular characterization showed that the animals had smaller cerebella with fewer granule cells. This defect was already apparent as early as 7 days after birth, when Elp1cKO animals also had fewer mitotic GCPs and shorter Purkinje dendrites. Through molecular characterization, we found that loss of Elp1 was associated with an increase in apoptotic cell death and cell stress pathways in GCPs. Our study demonstrates the importance of ELP1 in the developing cerebellum, and suggests that loss of Elp1 in the GC lineage may also play a role in the progressive ataxia phenotypes of FD patients.

S100A9 deletion in microglia/macrophages ameliorates brain injury through the STAT6/PPARγ pathway in ischemic stroke

BACKGROUND

Microglia and infiltrated macrophages (M/M) are integral components of the innate immune system that play a critical role in facilitating brain repair after ischemic stroke (IS) by clearing cell debris. Novel therapeutic strategies for IS therapy involve modulating M/M phenotype shifting. This study aims to elucidate the pivotal role of S100A9 in M/M and its downstream STAT6/PPARγ signaling pathway in neuroinflammation and phagocytosis after IS.

METHODS

In the clinical study, we initially detected the expression pattern of S100A9 in monocytes from patients with acute IS and investigated its association with the long-term prognosis. In the in vivo study, we generated the S100A9 conditional knockout (CKO) mice and compared the stroke outcomes with the control group. We further tested the S100A9-specific inhibitor paqunimod (PQD), for its pharmaceutical effects on stroke outcomes. Transcriptomics and in vitro studies were adopted to explore the mechanism of S100A9 in modulating the M/M phenotype, which involves the regulation of the STAT6/PPARγ signaling pathway.

RESULTS

S100A9 was predominantly expressed in classical monocytes and was correlated with unfavorable outcomes in patients of IS. S100A9 CKO mitigated infarction volume and white matter injury, enhanced cerebral blood flow and functional recovery, and prompted anti-inflammation phenotype and efferocytosis after tMCAO. The STAT6/PPARγ pathway, an essential signaling cascade involved in immune response and inflammation, might be the downstream target mediated by S100A9 deletion, as evidenced by the STAT6 phosphorylation inhibitor AS1517499 abolishing the beneficial effect of S100A9 inhibition in tMCAO mice and cell lines. Moreover, S100A9 inhibition by PQD treatment protected against neuronal death in vitro and brain injuries in vivo.

CONCLUSION

This study provides evidence for the first time that S100A9 in classical monocytes could potentially be a biomarker for predicting IS prognosis and reveals a novel therapeutic strategy for IS. By demonstrating that S100A9-mediated M/M polarization and phagocytosis can be reversed by S100A9 inhibition in a STAT6/PPARγ pathway-dependent manner, this study opens up new avenues for drug development in the field.

Circ-AGTPBP1 promotes white matter injury through miR-140-3p/Pcdh17 axis role of Circ-AGTPBP1 in white matter injury

White matter injury (WMI) resulting from intracerebral hemorrhage (ICH) is closely associated with adverse prognoses in ICH patients. Although Circ-AGTPBP1 has been reported to exhibit high expression in the serum of premature infants with WMI, its effects and mechanisms in ICH-induced WMI remain unclear. This study aimed to investigate the role of circ-AGTPBP1 in white matter injury after intracerebral hemorrhage. An intracerebral hemorrhage rat model was established by injecting autologous blood into rat left ventricles and circ-AGTPBP1 was knocked down at the ICH site using recombinant adeno-associated virus, AAV2/9. Magnetic resonance imaging (MRI) and gait analysis were conducted to assess long-term neurobehavioral effects. Primary oligodendrocyte progenitor cells (OPCs) were isolated from rats and overexpressed with circ-AGTPBP1. Downstream targets of circ-AGTPBP1 in OPCs were investigated using CircInteractome, qPCR, FISH analysis, and miRDB network. Luciferase gene assay was utilized to explore the relationship between miR-140-3p and Pcdh17 in OPCs and HEK-293T cells. Finally, CCK-8 assay, EdU staining, and flow cytometry were employed to evaluate the effects of mi-RNA-140-3p inhibitor or silencing of sh-pcd17 on the viability, proliferation, and apoptosis of OPCs. Low expression of circ-AGTPBP1 alleviates white matter injury and improves neurological functions in rats after intracerebral hemorrhage. Conversely, overexpression of circ-AGTPBP1 reduces the proliferative and migrative potential of oligodendrocyte progenitor cells and promotes apoptosis. CircInteractome web tool and qPCR confirmed that circ-AGTPBP1 binds with miR-140-3p in OPCs. Additionally, miRDB network predicted Pcdh17 as a downstream target of miR-140-3p. Moreover, pcdh17 expression was increased in the brain tissue of rats with intracerebral-induced white matter injury. Furthermore, inhibiting miR-140-3p suppressed the proliferation and migration of OPCs and facilitated apoptosis through Pcdh17. Circ-AGTPBP1 promotes white matter injury through modulating the miR-140-3p/Pcdh17 axis. The study provides a new direction for developing therapeutic strategies for white matter injury.

Gait analysis in chemotherapy-induced peripheral neurotoxicity rodent models

Gait analysis could be used in animal models as an indicator of sensory ataxia due to chemotherapy-induced peripheral neurotoxicity (CIPN). Over the years, gait analysis in in vivo studies has evolved from simple observations carried out by a trained operator to computerised systems with machine learning that allow the quantification of any variable of interest and the establishment of algorithms for behavioural classification. However, there is not a consensus on gait analysis use in CIPN animal models; therefore, we carried out a systematic review. Of 987 potentially relevant studies, 14 were included, in which different methods were analysed (observation, footprint and CatWalk™). We presented the state-of-the-art of possible approaches to analyse sensory ataxia in rodent models, addressing advantages and disadvantages of different methods available. Semi-automated methods may be of interest when preventive or therapeutic strategies are evaluated, also considering their methodological simplicity and automaticity; up to now, only CatWalk™ analysis has been tested. Future studies should expect that CIPN-affected animals tend to reduce hind paw support due to pain, allodynia or loss of sensation, and an increase in swing phase could or should be observed. Few available studies documented these impairments at the last time point, and only appeared later on respect to other earlier signs of CIPN (such as altered neurophysiological findings). For that reason, gait impairment could be interpreted as late repercussions of loss of sensory.

Translational evaluation of gait behavior in rodent models of arthritic disorders with the CatWalk device - a narrative review

Arthritic disorders have become one of the main contributors to the global burden of disease. Today, they are one of the leading causes of chronic pain and disability worldwide. Current therapies are incapable of treating pain sufficiently and preventing disease progression. The lack of understanding basic mechanisms underlying the initiation, maintenance and progression of arthritic disorders and related symptoms represent the major obstacle in the search for adequate treatments. For a long time, histological evaluation of joint pathology was the predominant outcome parameter in preclinical arthritis models. Nevertheless, quantification of pain and functional limitations analogs to arthritis related symptoms in humans is essential to enable bench to bedside translation and to evaluate the effectiveness of new treatment strategies. As the experience of pain and functional deficits are often associated with altered gait behavior, in the last decades, automated gait analysis has become a well-established tool for the quantitative evaluation of the sequalae of arthritic disorders in animal models. The purpose of this review is to provide a detailed overview on the current literature on the use of the CatWalk gait analysis system in rodent models of arthritic disorders, e.g., Osteoarthritis, Monoarthritis and Rheumatoid Arthritis. Special focus is put on the assessment and monitoring of pain-related behavior during the course of the disease. The capability of evaluating the effect of distinct treatment strategies and the future potential for the application of the CatWalk in rodent models of arthritic disorders is also addressed in this review. Finally, we discuss important consideration and provide recommendations on the use of the CatWalk in preclinical models of arthritic diseases.

The role of cannabinoid CB1 receptors in the antinociceptive and reparative actions of mesenchymal stem cells in rats with peripheral neuropathic pain

Mesenchymal stem cells (MSCs) can produce antinociceptive and reparative effects. Presumably, the MSCs-induced antinociception may be partly due to the involvement of the endocannabinoid system. The study aimed to evaluate the antinociceptive and reparative effects of adipose-derived MSCs (ADMSCs) upon pharmacological modulation of cannabinoid CB1 receptor in peripheral tissues or on ADMSCs' membranes in a rat model of peripheral neuropathy. ADMSCs were injected into the area of rat sciatic nerve injury (i) with no additional treatments, (ii) at the tissue CB1 receptor activation by endogenous agonist anandamide (AEA) or blockade with a selective AM251 antagonist; and (iii) preincubated with AEA or AM251. The evaluation of CB1 receptor activity involved analyzing nociceptive responses, gait parameters, and histology. Transplantation of ADMSCs upon activation of CB1 receptors, both on AMSCs' membranes or in the area of nerve injury, accelerated the analgesia and recovery of dynamic gait parameters, abolished static gait disturbances, and promoted the fastest nerve regeneration. Only blockade of CB1 receptors on ADMSCs shortened ADMSCs-induced analgesia and decreased the number of preserved nerve fibers. CB1 receptors on ADMSCs significantly contribute to their pain-relieving and tissue-repairing capabilities by stimulating the growth factors secretion and suppressing the release of pro-inflammatory cytokines. Peripheral CB1 receptors do not significantly influence ADMSC-induced antinociception.

A grooved conduit combined with decellularized tissues for peripheral nerve regeneration

Peripheral nerve injury (PNI) is a common and severe clinical disease worldwide, which leads to a poor prognosis because of the complicated treatments and high morbidity. Autologous nerve grafting as the gold standard still cannot meet the needs of clinical nerve transplantation because of its low availability and limited size. The development of artificial nerve conduits was led to a novel direction for PNI treatment, while most of the currently developed artificial nerve conduits was lack biochemical cues to promote nerve regeneration. In this study, we designed a novel composite neural conduit by inserting decellularized the rat sciatic nerve or kidney in a poly (lactic-co-glycolic acid) (PLGA) grooved conduit. The nerve regeneration effect of all samples was analyzed using rat sciatic nerve defect model, where decellularized tissues and grooved PLGA conduit alone were used as controls. The degree of nerve regeneration was evaluated using the motor function, gastrocnemius recovery, and morphological and histological assessments suggested that the combination of a grooved conduit with decellularized tissues significantly promoted nerve regeneration compared with decellularized tissues and PLGA conduit alone. It is worth to note that the grooved conduits containing decellularized nerves have a promotive effect similar to that of autologous nerve grafting, suggesting that it could be an artificial nerve conduit used for clinical practice in the future.

CatWalk XT gait parameters: a review of reported parameters in pre-clinical studies of multiple central nervous system and peripheral nervous system disease models

Automated gait assessment tests are used in studies of disorders characterized by gait impairment. CatWalk XT is one of the first commercially available automated systems for analyzing the gait of rodents and is currently the most used system in peer-reviewed publications. This automated gait analysis system can generate a large number of gait parameters. However, this creates a new challenge in selecting relevant parameters that describe the changes within a particular disease model. Here, for the first time, we performed a multi-disorder review on published CatWalk XT data. We identify commonly reported CatWalk XT gait parameters derived from 91 peer-reviewed experimental studies in mice, covering six disorders of the central nervous system (CNS) and peripheral nervous system (PNS). The disorders modeled in mice were traumatic brain injury (TBI), stroke, sciatic nerve injury (SNI), spinal cord injury (SCI), Parkinson's disease (PD), and ataxia. Our review consisted of parameter selection, clustering, categorization, statistical evaluation, and data visualization. It suggests that certain gait parameters serve as potential indicators of gait dysfunction across multiple disease models, while others are specific to particular models. The findings also suggest that the more site-specific the injury is, the fewer parameters are reported to characterize its gait abnormalities. This study strives to present a clearly organized picture of gait parameters used in each one of the different mouse models, potentially helping novel CatWalk XT users to apply this information to similar or related mouse models they are working on.

ATP-releasing SWELL1 channel in spinal microglia contributes to neuropathic pain

Following peripheral nerve injury, extracellular adenosine 5'-triphosphate (ATP)-mediated purinergic signaling is crucial for spinal cord microglia activation and neuropathic pain. However, the mechanisms of ATP release remain poorly understood. Here, we show that volume-regulated anion channel (VRAC) is an ATP-releasing channel and is activated by inflammatory mediator sphingosine-1-phosphate (S1P) in microglia. Mice with microglia-specific deletion of Swell1 (also known as Lrrc8a), a VRAC essential subunit, had reduced peripheral nerve injury-induced increase in extracellular ATP in spinal cord. The mutant mice also exhibited decreased spinal microgliosis, dorsal horn neuronal hyperactivity, and both evoked and spontaneous neuropathic pain-like behaviors. We further performed high-throughput screens and identified an FDA-approved drug dicumarol as a novel and potent VRAC inhibitor. Intrathecal administration of dicumarol alleviated nerve injury-induced mechanical allodynia in mice. Our findings suggest that ATP-releasing VRAC in microglia is a key spinal cord determinant of neuropathic pain and a potential therapeutic target for this debilitating disease.

O-GlcNAcylation Is Required for the Survival of Cerebellar Purkinje Cells by Inhibiting ROS Generation

Purkinje cells (PCs), as a unique type of neurons output from the cerebellar cortex, are essential for the development and physiological function of the cerebellum. However, the intricate mechanisms underlying the maintenance of Purkinje cells are unclear. The O-GlcNAcylation (O-GlcNAc) of proteins is an emerging regulator of brain function that maintains normal development and neuronal circuity. In this study, we demonstrate that the O-GlcNAc transferase (OGT) in PCs maintains the survival of PCs. Furthermore, a loss of OGT in PCs induces severe ataxia, extensor rigidity and posture abnormalities in mice. Mechanistically, OGT regulates the survival of PCs by inhibiting the generation of intracellular reactive oxygen species (ROS). These data reveal a critical role of O-GlcNAc signaling in the survival and maintenance of cerebellar PCs.

Acetylcholine receptors of the neuromuscular junctions present normal distribution after peripheral nerve injury and repair through nerve guidance associated with fibrin biopolymer

Peripheral nerve injuries (PNI) lead to alterations in the Agrin-LRP4-MuSK pathway. This results in disaggregation of AChRs and change from epsilon (mature, innervated) to gamma (immature, denervated) subunit. Tubulization technique has been shown to be effective for PNI repair and it also allows the use of adjuvants, such as fibrin biopolymer (FB). This study evaluated the effect of the association of tubulization with FB after PNI on AChRs and associated proteins. Fifty-two adults male Wistar rats were used, distributed in 4 experimental groups: Sham Control (S), Denervated Control (D); Tubulization (TB) and Tubulization + Fibrin Biopolymer (TB+FB). Catwalk was performed every 15 days. Ninety days after surgery the right soleus muscles and ischiatic nerves were submitted to the following analyses: (a) morphological and morphometric analysis of AChRs by confocal microscopy; (b) morphological and morphometric analysis of the ischiatic nerve; (c) protein quantification of AChRs: alpha, gama, and epsilon, of Schwann cells, agrin, LRP4, MuSK, rapsyn, MMP3, MyoD, myogenin, MURF1 and atrogin-1. The main results were about the NMJs that in the TB+FB group presented morphological and morphometric approximation (compactness index; area of the AChRs and motor plate) to the S group. In addition, there were also an increase of S100 and AChRε protein expression and a decrease of MyoD. These positive association resulted in AChRs stabilization that potentiate the neuromuscular regeneration, which strengthens the use of TB for severe injuries repair and the beneficial effect of FB, along with tubulization technique.

ATP-releasing SWELL1 channel in spinal microglia contributes to neuropathic pain

Following peripheral nerve injury, extracellular ATP-mediated purinergic signaling is crucial for spinal cord microglia activation and neuropathic pain. However, the mechanisms of ATP release remain poorly understood. Here, we show that volume-regulated anion channel (VRAC) is an ATP-releasing channel and is activated by inflammatory mediator sphingosine-1-phosphate (S1P) in microglia. Mice with microglia-specific deletion of Swell1 (also known as Lrrc8a), a VRAC essential subunit, had reduced peripheral nerve injury-induced increase in extracellular ATP in spinal cord. The mutant mice also exhibited decreased spinal microgliosis, dorsal horn neuronal hyperactivity, and both evoked and spontaneous neuropathic pain-like behaviors. We further performed high-throughput screens and identified an FDA-approved drug dicumarol as a novel and potent VRAC inhibitor. Intrathecal administration of dicumarol alleviated nerve injury-induced mechanical allodynia in mice. Our findings suggest that ATP-releasing VRAC in microglia is a key spinal cord determinant of neuropathic pain and a potential therapeutic target for this debilitating disease.

Evaluation of peripheral nerve regeneration in Murphy Roths Large mouse strain following transection injury

Aim: Murphy Roths Large (MRL/MpJ) mice have demonstrated the ability to heal with minimal or no scar formation in several tissue types. In order to identify a novel animal model, this study sought to evaluate whether this attribute applies to peripheral nerve regeneration. Materials & methods: This was a two-phase study. 6-week-old male mice were divided into two interventional groups: nerve repair and nerve graft. The MRL/MpJ was compared with the C57BL/6J strain for evaluation of both functional and histological outcomes. Results: MRL/MpJ strain demonstrated superior axon myelination and less scar formation, however functional outcomes did not show significant difference between strains. Conclusion: Superior histological outcomes did not translate into superior peripheral nerve regeneration in MRL/MpJ strain.

The success of biomaterial-based tissue engineering strategies for peripheral nerve regeneration

Peripheral nerve injury is a clinically common injury that causes sensory dysfunction and locomotor system degeneration, which seriously affects the quality of the patients' daily life. Long gapped defects in large nerve are difficult to repair via surgery and limited donor source of autologous nerve greatly challenges the successful nerve repair by transplantation. Significantly, remarkable progress has been made in repairing the peripheral nerve injury using artificial nerve grafts and a variety of products for peripheral nerve repair have emerged been approved globally in recent years. The raw materials of these commercial products includes natural/synthetic polymers, extracellular matrix. Despite a lot of effort, the desirable functional recovery still remains great challenges in long gapped nerve defects. Thus this review discusses the recent development of tissue engineering products for peripheral nerve repair and the design of bionic grafts improving the local microenvironment for accelerating nerve regeneration against locomotor disorder, which may provide potential strategies for the repair of long gaps or thick nerve defects by multifunctional biomaterials.

Functional Gait Assessment Using Manual, Semi-Automated and Deep Learning Approaches Following Standardized Models of Peripheral Nerve Injury in Mice

Objective: To develop a standardized model of stretch−crush sciatic nerve injury in mice, and to compare outcomes of crush and novel stretch−crush injuries using standard manual gait and sensory assays, and compare them to both semi-automated as well as deep-learning gait analysis methods. Methods: Initial studies in C57/Bl6 mice were used to develop crush and stretch−crush injury models followed by histologic analysis. In total, 12 eight-week-old 129S6/SvEvTac mice were used in a six-week behavioural study. Behavioral assessments using the von Frey monofilament test and gait analysis recorded on a DigiGait platform and analyzed through both Visual Gait Lab (VGL) deep learning and standardized sciatic functional index (SFI) measurements were evaluated weekly. At the termination of the study, neurophysiological nerve conduction velocities were recorded, calf muscle weight ratios measured and histological analyses performed. Results: Histological evidence confirmed more severe histomorphological injury in the stretch−crush injured group compared to the crush-only injured group at one week post-injury. Von Frey monofilament paw withdrawal was significant for both groups at week one compared to baseline (p < 0.05), but not between groups with return to baseline at week five. SFI showed hindered gait at week one and two for both groups, compared to baseline (p < 0.0001), with return to baseline at week five. Hind stance width (HSW) showed similar trends as von Frey monofilament test as well as SFI measurements, yet hind paw angle (HPA) peaked at week two. Nerve conduction velocity (NCV), measured six weeks post-injury, at the termination of the study, did not show any significant difference between the two groups; yet, calf muscle weight measurements were significantly different between the two, with the stretch−crush group demonstrating a lower (poorer) weight ratio relative to uninjured contralateral legs (p < 0.05). Conclusion: Stretch−crush injury achieved a more reproducible and constant injury compared to crush-only injuries, with at least a Sunderland grade 3 injury (perineurial interruption) in histological samples one week post-injury in the former. However, serial behavioral outcomes were comparable between the two crush groups, with similar kinetics of recovery by von Frey testing, SFI and certain VGL parameters, the latter reported for the first time in rodent peripheral nerve injury. Semi-automated and deep learning-based approaches for gait analysis are promising, but require further validation for evaluation in murine hind-limb nerve injuries.

The Grasping Test Revisited: A Systematic Review of Functional Recovery in Rat Models of Median Nerve Injury

The rat median nerve model is a well-established and frequently used model for peripheral nerve injury and repair. The grasping test is the gold-standard to evaluate functional recovery in this model. However, no comprehensive review exists to summarize the course of functional recovery in regard to the lesion type. According to PRISMA-guidelines, research was performed, including the databases PubMed and Web of Science. Groups were: (1) crush injury, (2) transection with end-to-end or with (3) end-to-side coaptation and (4) isogenic or acellular allogenic grafting. Total and respective number, as well as rat strain, type of nerve defect, length of isogenic or acellular allogenic allografts, time at first signs of motor recovery (FSR) and maximal recovery grasping strength (MRGS), were evaluated. In total, 47 articles met the inclusion criteria. Group I showed earliest signs of motor recovery. Slow recovery was observable in group III and in graft length above 25 mm. Isografts recovered faster compared to other grafts. The onset and course of recovery is heavily dependent from the type of nerve injury. The grasping test should be used complementary in addition to other volitional and non-volitional tests. Repetitive examinations should be planned carefully to optimize assessment of valid and reliable data.

ESWT Diminishes Axonal Regeneration following Repair of the Rat Median Nerve with Muscle-In-Vein Conduits but Not after Autologous Nerve Grafting

Investigations reporting positive effects of extracorporeal shockwave therapy (ESWT) on nerve regeneration are limited to the rat sciatic nerve model. The effects of ESWT on muscle-in-vein conduits (MVCs) have also not been investigated yet. This study aimed to evaluate the effects of ESWT after repair of the rat median nerve with either autografts (ANGs) or MVCs. In male Lewis rats, a 7 mm segment of the right median nerve was reconstructed either with an ANG or an MVC. For each reconstructive technique, one group of animals received one application of ESWT while the other rats served as controls. The animals were observed for 12 weeks, and nerve regeneration was assessed using computerized gait analysis, the grasping test, electrophysiological evaluations and histological quantification of axons, blood vessels and lymphatic vasculature. Here, we provide for the first time a comprehensive analysis of ESWT effects on nerve regeneration in a rat model of median nerve injury. Furthermore, this study is among the first reporting the quantification of lymphatic vessels following peripheral nerve injury and reconstruction in vivo. While we found no significant direct positive effects of ESWT on peripheral nerve regeneration, results following nerve repair with MVCs were significantly inferior to those after ANG repair.

Comparison of human amniotic membrane and collagen nerve wraps around sciatic nerve reverse autografts in a rat model

Human amniotic membrane (hAM) and collagen nerve wraps are biomaterials that have been investigated as therapies for improving outcomes of peripheral nerve regeneration; however, their efficacy has not been compared. The purpose of this study is to compare the efficacy of collagen and human amniotic membrane nerve wraps in a rodent sciatic nerve reverse autograft model. Lewis rats (n = 29) underwent sciatic nerve injury and repair in which a 10-mm gap was bridged with reverse autograft combined with either no nerve wrap (control), collagen nerve wrap or hAM nerve wrap. Behavioral analyses were performed at baseline and 4, 8 and 12 weeks. Electrophysiological studies were conducted at 8, 10 and 12 weeks. Additional outcomes assessed included gastrocnemius muscle weights, nerve adhesions, axonal regeneration and scarring at 12 weeks. Application of both collagen and hAM nerve wraps resulted in improvement of functional and histologic outcomes when compared with controls, with a greater magnitude of improvement for the experimental group treated with hAM nerve wraps. hAM-treated animals had significantly higher numbers of axons compared to control animals (p < 0.05) and significantly less perineural fibrosis than both control and collagen treated nerves (p < 0.05). The ratio of experimental to control gastrocnemius weights was significantly greater in hAM compared to control samples (p < 0.05). We conclude that hAM nerve wraps are a promising biomaterial that is effective for improving outcomes of peripheral nerve regeneration, resulting in superior nerve regeneration and functional recovery compared to collagen nerve wraps and controls.

Ferroptosis in oligodendrocyte progenitor cells mediates white matter injury after hemorrhagic stroke

Oligodendrocyte progenitor cells (OPCs) differentiate to myelin-producing mature oligodendrocytes and enwrap growing or demyelinated axons during development and post central nervous diseases. Failure of remyelination owing to cell death or undifferentiation of OPCs contributes to severe neurologic deficits and motor dysfunction. However, how to prevent the cell death of OPCs is still poorly understood, especially in hemorrhagic diseases. In the current study, we injected autologous blood into the mouse lateral ventricular to study the hemorrhage-induced OPC cell death in vivo. The integrity of the myelin sheath of the corpus callosum was disrupted post intraventricular hemorrhage (IVH) assessed by using magnetic resonance imaging, immunostaining, and transmission electron microscopy. Consistent with the severe demethylation, we observed massive cell death of oligodendrocyte lineages in the periventricular area. In addition, we found that ferroptosis is the major cell death form in Hemin-induced OPC death by using RNA-seq analysis, and the mechanism was glutathione peroxidase 4 activity reduction-resulted lipid peroxide accumulation. Furthermore, inhibition of ferroptosis rescued OPC cell death in vitro, and in vivo attenuated IVH-induced white matter injury and promoted recovery of neurological function. These data demonstrate that ferroptosis is an essential form of OPC cell death in hemorrhagic stroke, and rescuing ferroptotic OPCs could serve as a therapeutic target for stroke and related diseases.

Exploring the Correlation Between the Regulation of Macrophages by Regulatory T Cells and Peripheral Neuropathic Pain

Objective

Intractable pain after peripheral nerve injury has become a major concern in the field of pain. Current evidence shows that routine medications or surgical treatment is associated with inconsistent results and different curative effects. Stable and effective treatment methods in clinical practice are also lacking. To date, there is no consensus on the pathophysiological mechanisms of pain. The present study investigates the potential regulatory role of regulatory T cells in the differentiation of macrophages on dorsal root ganglion (DRG) and explores the mechanism of nociceptive signals in the signal transfer station. The findings are expected to guide the prevention of various types of peripheral neuropathic pain.

Methods

Thirty-six male Sprague Dawley (SD) rats and 18 male Nude rats, of equal weight (250–300g), were used in this study. The rats were divided into 3 groups: SD rat sciatic nerve transection group (SNT group, n = 18), SD rat nerve transection experimental group (SNT/RAPA group, n = 18) and Nude rat nerve transection experimental group (SNT/NUDE group, n = 18). The behavior related to neuropathic pain of animals were comprehensively evaluated in all groups. Furthermore, we analyzed the degree of neuroma development, histology, gene, and protein expression, and compared their correlation with the ultrastructural changes of M1/M2 type differentiation of macrophages in DRG.

Results

Sciatic nerve transection (SNT), induced the aggregation of several types of macrophages in lumbar DRG of SD rats leading to a higher ratio of M1/M2. Following the inhibition of the M1 type polarization of macrophages, axon outgrowth increased significantly. A significantly lower average autotomy score was reported in the SNT/NUDE group (*p &lt; 0.05) and the SNT/RAPA group (@p &lt; 0.05) as compared to that of the SNT group. The SNT/NUDE group showed no noticeable neuroma formation 30 days after the nerve transection. However, bulbous neuromas were observed in the nerve stumps of both the SNT control and SNT/RAPA groups. Immunofluorescence staining revealed a significant decrease in the proportion of M1/M2 macrophages in lumbar DRG of the SNT/NUDE group (**p &lt; 0.001) and the SNT/RAPA group (@p &lt; 0.05) compared to the SNT group. The expression of pain-related proteins was also decreased (@p &lt; 0.05, *p &lt; 0.05,**p &lt; 0.001). Also, the expression of alpha-smooth muscle actin (α-SMA), neurofilament 200 (NF-200), and nerve growth factor low-affinity receptor p75 were significantly down-regulated in the nerve tissue (@p &lt; 0.05, @@p &lt; 0.001, **p &lt; 0.001).

Conclusion

M1/M2 type differentiation of macrophages on DRG plays a significant role in the formation of traumatic painful neuroma after neurotomy. In combination with our previous study, the results of this study suggest that regulatory T cells reduce the ratio of M1/M2 macrophages and alleviate the pain of neuroma by regulating the polarization direction of macrophages on neuroma. These findings provide key insights into developing new strategies to manage painful neuroma.

Exercise Intervention Promotes the Growth of Synapses and Regulates Neuroplasticity in Rats With Ischemic Stroke Through Exosomes

Background: Stroke is the leading cause of death and disability. Exercise produces neuroprotection by improving neuroplasticity. Exercise can induce exosome production. According to several studies, exosomes are involved in repairing brain function, but the relationship and mechanism of exercise, exosomes, and neuroprotection have not been elucidated. This study intends to explore the relationship and potential mechanism by observing the changes in the exosome level, infarct volume, neurological function and behavioral scores, synapses, and corticospinal tract (CST).

Methods: Rats were randomly divided into four groups: a sham operation (SHAM) group, middle cerebral artery occlusion (MCAO) with sedentary intervention (SED-MCAO) group, MCAO with exercise intervention (EX-MCAO) group, and MCAO with exercise intervention and exosome injection (EX-MCAO-EXO) group. The exercise intervention was started 1 day after MCAO and lasted for 4 weeks. All rats were assessed using the modified neurological severity score (mNSS). The levels of exosomes in serum and brain, gait analysis, and magnetic resonance scan were performed 1 and 4 weeks after the intervention. After 4 weeks of intervention, the number of synapses, synaptophysin (Syn), and postsynaptic density protein 95(PSD-95) expression was detected.

Results: After 4 weeks of intervention, (1) the EX-MCAO and EX-MCAO-EXO groups showed higher serum exosome (p_EX−MCAO = 0.000, p_{EX−MCAO−EXO} = 0.000) and brain exosome (p_EX−MCAO = 0.001, p_{EX−MCAO−EXO} = 0.000) levels than the SED-MCAO group, of which the EX-MCAO group had the highest serum exosome (p = 0.000) and the EX-MCAO-EXO group had the highest brain exosome (p = 0.03) levels. (2) The number of synapses in the EX-MCAO (p = 0.032) and EX-MCAO-EXO groups (p = 0.000) was significantly higher than that in the SED-MCAO group. The EX-MCAO-EXO group exhibited a greater number of synapses than the EX-MCAO (p = 0.000) group. (3) The synaptic plasticity-associated proteins were expressed significantly higher in the EX-MCAO (p_Syn = 0.010, p_PSD−95 = 0.044) and EX-MCAO-EXO (p_Syn = 0.000, p_PSD−95 = 0.000) groups than in the SED-MCAO group, and the EX-MCAO-EXO group (p_Syn = 0.000, p_PSD−95 = 0.046) had the highest expression. (4) Compared with the SED-MCAO group, the EX-MCAO group had significantly improved infarct volume ratio (p = 0.000), rFA value (p = 0.000), and rADC (p = 0.000). Compared with the EX-MCAO group, the EX-MCAO-EXO group had a significantly improved infarct volume ratio (p = 0.000), rFA value (p = 0.000), and rADC value (p = 0.001). (5) Compared with the SED-MCAO group, the EX-MCAO group (p = 0.001) and EX-MCAO-EXO group (p = 0.000) had significantly lower mNSS scores and improved gait. (6) The brain exosome levels were negatively correlated with the mNSS score, infarct volume ratio, and rADC value and positively correlated with the rFA value, Syn, and PSD-95 expression. The serum and brain exosome levels showed a positive correlation.

Conclusions: Exercise intervention increases the serum exosome level in MCAO rats, which are recruited into the brain, leading to improved synaptic growth and CST integrity, a reduced infarct volume, and improved neurological function and gait.

Gait Analysis Using Animal Models of Peripheral Nerve and Spinal Cord Injuries

The present review discusses recent data regarding rodent models of spinal cord and peripheral nerve injuries in terms of gait analysis using the CatWalk system (CW), an automated and exceptionally reliable system for assessing gait abnormalities and motor coordination. CW is a good tool for both studying improvements in the walking of animals after suffering a peripheral nerve and spinal cord lesion and to select the best therapies and procedures after tissue destruction, given that it provides objective and quantifiable data. Most studies using CW for gait analysis that were published in recent years focus on injuries inflicted in the peripheral nerve, spinal cord, and brain. CW has been used in the assessment of rodent motor function through high-resolution videos, whereby specialized software was used to measure several aspects of the animal's gait, and the main characteristics of the automated system are presented here. CW was developed to assess footfall and gait changes, and it can calculate many parameters based on footprints and time. However, given the multitude of parameters, it is necessary to evaluate which are the most important under the employed experimental circumstances. By selecting appropriate animal models and evaluating peripheral nerve and spinal cord lesion regeneration using standardized methods, suggestions for new therapies can be provided, which represents the translation of this methodology into clinical application.

A systematic review and meta-analysis of studies comparing muscle-in-vein conduits with autologous nerve grafts for nerve reconstruction

The gold-standard method for reconstruction of segmental nerve defects, the autologous nerve graft, has several drawbacks in terms of tissue availability and donor site morbidity. Therefore, feasible alternatives to autologous nerve grafts are sought. Muscle-in-vein conduits have been proposed as an alternative to autologous nerve grafts almost three decades ago, given the abundance of both tissues throughout the body. Based on the anti-inflammatory effects of veins and the proregenerative environment established by muscle tissue, this approach has been studied in various preclinical and some clinical trials. There is still no comprehensive systematic summary to conclude efficacy and feasibility of muscle-in-vein conduits for reconstruction of segmental nerve defects. Given this lack of a conclusive summary, we performed a meta-analysis to evaluate the potential of muscle-in-vein conduits. This work’s main findings are profound discrepancies regarding the results following nerve repair by means of muscle-in-vein conduits in a preclinical or clinical setting. We identified differences in study methodology, inter-species neurobiology and the limited number of clinical studies to be the main reasons for the still inconclusive results. In conclusion, we advise for large animal studies to elucidate the feasibility of muscle-in-vein conduits for repair of segmental defects of critical size in mixed nerves.

Evaluation of Functional Recovery in Rats After Median Nerve Resection and Autograft Repair Using Computerized Gait Analysis

Computerized gait analysis is a common evaluation method in rat models of hind limb nerve injuries, but its use remains unpublished in models of segmental nerve injury of the forelimb. It was the aim of this work to investigate if computerized gait analysis is a feasible evaluation method in a rat model of segmental median nerve injury and autograft repair. Ten male Lewis rats underwent 7-mm resection of the right median nerve with immediate autograft repair. The left median nerve was resected without repair and served as an internal control. Animals were assessed for 12 weeks after surgery via CatWalk (CW) gait analysis every 2 weeks. Evaluation of motor recovery by means of the grasping test was performed weekly while electrophysiological measurements were performed at the end of the observation period. CW data were correlated with grasping strength at each post-operative time point. CW data were also correlated with electrophysiology using linear regression analysis. Principal component analysis was performed to identify clusters of outcome metrics. Recovery of motor function was observable 4 weeks after surgery, but grasping strength was significantly reduced (p < 0.01) compared to baseline values until post-operative week 6. In terms of sensory recovery, the pain-related parameter Duty Cycle showed significant (p < 0.05) recovery starting from post-operative week 8. The Print Area of the right paw was significantly (p < 0.05) increased compared to the left side starting from post-operative week 10. Various parameters of gait correlated significantly (p < 0.05) with mean and maximum grasping strength. However, only Stand Index showed a significant correlation with compound muscle action potential (CMAP) amplitude (p < 0.05). With this work, we prove that computerized gait analysis is a valid and feasible method to evaluate functional recovery after autograft repair of the rat median nerve. We were able to identify parameters such as Print Area, Duty Cycle, and Stand Index, which allow assessment of nerve regeneration. The course of these parameters following nerve resection without repair was also assessed. Additionally, external paw rotation was identified as a valid parameter to evaluate motor reinnervation. In summary, computerized gait analysis is a valuable additional tool to study nerve regeneration in rats with median nerve injury.