Establishing a reliable gait evaluation method for rodent studies

Constraint-Induced Movement Therapy (CIMT) and Neural Precursor Cell (NPC) Transplantation Synergistically Promote Anatomical and Functional Recovery in a Hypoxic-Ischemic Mouse Model

Cerebral palsy (CP) is a common neurodevelopmental disorder characterized by pronounced motor dysfunction and resulting in physical disability. Neural precursor cells (NPCs) have shown therapeutic promise in mouse models of hypoxic-ischemic (HI) perinatal brain injury, which mirror hemiplegic CP. Constraint-induced movement therapy (CIMT) enhances the functional use of the impaired limb and has emerged as a beneficial intervention for hemiplegic CP. However, the precise mechanisms and optimal application of CIMT remain poorly understood. The potential synergy between a regenerative approach using NPCs and a rehabilitation strategy using CIMT has not been explored. We employed the Rice-Vannucci HI model on C57Bl/6 mice at postnatal day (PND) 7, effectively replicating the clinical and neuroanatomical characteristics of hemiplegic CP. NPCs were transplanted in the corpus callosum (CC) at PND21, which is the age corresponding to a 2-year-old child from a developmental perspective and until which CP is often not formally diagnosed, followed or not by Botulinum toxin injections in the unaffected forelimb muscles at PND23, 26, 29 and 32 to apply CIMT. Both interventions led to enhanced CC myelination and significant functional recovery (as shown by rearing and gait analysis testing), through the recruitment of endogenous oligodendrocytes. The combinatorial treatment indicated a synergistic effect, as shown by newly recruited oligodendrocytes and functional recovery. This work demonstrates the mechanistic effects of CIMT and NPC transplantation and advocates for their combined therapeutic potential in addressing hemiplegic CP.

Coordination function index: A novel indicator for assessing hindlimb locomotor recovery in spinal cord injury rats based on catwalk gait parameters

In preclinical studies of spinal cord injury (SCI), behavioral assessments are crucial for evaluating treatment effectiveness. Commonly used methods include Basso, Beattie, Bresnahan (BBB) score and the Louisville swim scale (LSS), relying on subjective observations. The CatWalk automated gait analysis system is also widely used in SCI studies, providing extensive gait parameters from footprints. However, these parameters are often used independently or combined simply without utilizing the vast amount of data provided by CatWalk. Therefore, it is necessary to develop a novel approach encompassing multiple CatWalk parameters for a comprehensive and objective assessment of locomotor function. In this work, we screened 208 CatWalk XT gait parameters and identified 38 suitable for assessing hindlimb motor function recovery in a rat thoracic contusion SCI model. Exploratory factor analysis was used to reveal structural relationships among these parameters. Weighted scores for Coordination effectively differentiated hindlimb motor function levels, termed as the Coordinated Function Index (CFI). CFI showed high reliability, exhibiting high correlations with BBB scores, LSS, and T2WI lesion area. Finally, we simplified CFI based on factor loadings and correlation analysis, obtaining a streamlined version with reliable assessment efficacy. In conclusion, we developed a systematic assessment indicator utilizing multiple CatWalk parameters to objectively evaluate hindlimb motor function recovery in rats after thoracic contusion SCI.

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.

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.

Neurobehavioral deficits of mice expressing a low level of G127V mutant frataxin

Friedreich's ataxia (FRDA) is a neurodegenerative disease caused by reduced expression of the mitochondrial protein frataxin (FXN). Most FRDA patients are homozygous for large expansions of GAA repeats in intron 1 of FXN, while some are compound heterozygotes with an expanded GAA tract in one allele and a missense or nonsense mutation in the other. A missense mutation, changing a glycine to valine at position 130 (G130V), is prevalent among the clinical variants. We and others have demonstrated that levels of mature FXN protein in FRDA G130V samples are reduced below those detected in samples harboring homozygous repeat expansions. Little is known regarding expression and function of endogenous FXN-G130V protein due to lack of reagents and models that can distinguish the mutant FXN protein from the wild-type FXN produced from the GAA-expanded allele. We aimed to determine the effect of the G130V (murine G127V) mutation on Fxn expression and to define its multi-system impact in vivo. We used CRISPR/Cas9 to introduce the G127V missense mutation in the Fxn coding sequence and generated homozygous mice (Fxn^G127V/G127V). We also introduced the G127V mutation into a GAA repeat expansion FRDA mouse model (Fxn^GAA230/KO; KIKO) to generate a compound heterozygous strain (Fxn^G127V/GAA230). We performed neurobehavioral tests on cohorts of WT and Fxn mutant animals at three-month intervals for one year, and collected tissue samples to analyze molecular changes during that time. The endogenous Fxn G127V protein is detected at much lower levels in all tissues analyzed from Fxn^G127V/G127V mice compared to age and sex-matched WT mice without differences in Fxn transcript levels. Fxn^G127V/G127V mice are significantly smaller than WT counterparts, but perform similarly in most neurobehavioral tasks. RNA sequencing analysis revealed reduced expression of genes in oxidative phosphorylation and protein synthesis, underscoring the metabolic consequences in our mouse model expressing extremely low levels of Fxn. Results of these studies provide insight into the unique pathogenic mechanism of the FXN G130V mechanism and the tolerable limit of Fxn/FXN expression in vivo.

Clinical Assessments of Fracture Healing and Basic Science Correlates: Is There Room for Convergence?

PURPOSE OF REVIEW

The purpose of this review is to summarize the clinical and basic science methods used to assess fracture healing and propose a framework to improve the translational possibilities.

RECENT FINDINGS

Mainstays of fracture healing assessment include clinical examination, various imaging modalities, and assessment of function. Pre-clinical studies have yielded insight into biomechanical progression as well as the genetic, molecular, and cellular processes of fracture healing. Efforts are emerging to identify early markers to predict impaired healing and possibly early intervention to alter these processes. Despite of the differences in clinical and preclinical research, opportunities exist to unify and improve the translational efforts between these arenas to develop and optimize our ability to assess and predict fracture healing, thereby improving the clinical care of these patients.

Temporal alteration of microglia to microinfarcts in rat brain induced by the vascular occlusion with fluorescent microspheres

Microglia, the resident immune cells in the central nervous system, can monitor the microenvironment and actively respond to ischemic stroke and other brain injuries. In this procedure, microglia and neurons can cross-talk via transmembrane chemokine, Fractalkine (CX3CL1), to impact one another. We used a rat model of multifocal microinfarcts induced by the injection of fluorescent microspheres into the right common carotid artery and examined the morphological alteration of blood vessels, microglia, astrocytes, and neurons at 6 h, 1, 7, and 14 days after modeling, along with neurobehavioral tests and the staining of CX3CL1 in this study. Our results demonstrated that in the infarcted regions, astrocytes and microglia activated in response to neuronal degeneration and upregulation of cleaved caspase-3, which occurred concurrently with vascular alteration and higher expression of CX3CL1. We provided sequential histological data to shed light on the morphological changes after modeling, which would help in the identification of new targets and the choice of the ideal time window for therapeutic intervention in ischemic stroke.

Melatonin promotes peripheral nerve repair through Parkin-mediated mitophagy

Schwann cells (SCs) are the major glial cells in peripheral nervous system. They unsheathe and myelinate axons and play an essential role in peripheral nerve regeneration. Several studies report that Parkin-mediated mitophagy is associated with various diseases. Melatonin promotes proliferation of central glial cells. Little is known about the effect of melatonin and Parkin-mediated mitophagy on peripheral nerve repair. In this study, using a rat model of a peripheral nerve injury (PNI) and in vitro model established by RSC96 cells treated with tert-butyl hydroperoxide (TBHP), we found that Parkin-mediated mitophagy can effectively reduce the production of mitochondrial reactive oxygen species (ROS), maintain the balance of mitochondrial membrane potential, maintain autophagic flux, and inhibit mitochondrial apoptosis. At the same time, we found that the increase of Parkin under stress is a manifestation of the RSC96 cells' resistance to oxidative stress to maintain RSC96 cells' balance. In our experiment, melatonin is similar to a Parkin agonist, up-regulating the expression of Parkin, enhancing all the positive results of Parkin in a stress state, such as inhibiting active oxygen production, maintaining autophagic flux, and inhibiting mitochondrial apoptosis. In addition, we design in vivo experiments to verify in In vitro experiments. In in vivo, melatonin promotes the expression of Parkin, maintains autophagic flux, inhibits apoptosis, promotes myelin regeneration, reduces the regeneration of collagen fibers around damaged tissues, and promotes peripheral nerve repair. When adenovirus was used to down-regulate the expression of Parkin, we found that all the positive effects of melatonin were attenuated. Collectively, these findings indicate that melatonin upregulates Parkin-mediated mitophagy and promotes peripheral nerve repair. The results provide a basis for development of effective drugs for PNI treatment.

Local vibration therapy promotes the recovery of nerve function in rats with sciatic nerve injury

OBJECTIVE

It has been reported that local vibration therapy can benefit recovery after peripheral nerve injury, but the optimized parameters and effective mechanism were unclear. In the present study, we investigated the effect of local vibration therapy of different amplitudes on the recovery of nerve function in rats with sciatic nerve injury (SNI).

METHODS

Adult male Sprague-Dawley rats were subjected to SNI and then randomly divided into 5 groups: sham group, SNI group, SNI + A-1 mm group, SNI + A-2 mm group, and SNI + A-4 mm group (A refers to the amplitude; n = 10 per group). Starting on the 7th day after model initiation, local vibration therapy was given for 21 consecutive days with a frequency of 10 Hz and an amplitude of 1, 2 or 4 mm for 5 min. The sciatic function index (SFI) was assessed before surgery and on the 7th, 14th, 21st and 28th days after surgery. Tissues were harvested on the 28th day after surgery for morphological, immunofluorescence and Western blot analysis.

RESULTS

Compared with the SNI group, on the 28th day after surgery, the SFIs of the treatment groups were increased; the difference in the SNI + A-2 mm group was the most obvious (95% confidence interval [CI]: [5.86, 27.09], P < 0.001), and the cross-sectional areas of myocytes in all of the treatment groups were improved. The G-ratios in the SNI + A-1 mm group and SNI + A-2 mm group were reduced significantly (95% CI: [-0.12, -0.02], P = 0.007; 95% CI: [-0.15, -0.06], P < 0.001). In addition, the expressions of S100 and nerve growth factor proteins in the treatment groups were increased; the phosphorylation expressions of ERK1/2 protein in the SNI + A-2 mm group and SNI + A-4 mm group were upregulated (95% CI: [0.03, 0.96], P = 0.038; 95% CI: [0.01, 0.94], P = 0.047, respectively), and the phosphorylation expression of Akt in the SNI + A-1 mm group was upregulated (95% CI: [0.11, 2.07], P = 0.031).

CONCLUSION

Local vibration therapy, especially with medium amplitude, was able to promote the recovery of nerve function in rats with SNI; this result was linked to the proliferation of Schwann cells and the activation of the ERK1/2 and Akt signaling pathways.

Gait performance of adolescent mice assessed by the CatWalk XT depends on age, strain and sex and correlates with speed and body weight

The automatization of behavioral tests assessing motor activity in rodent models is important for providing robust and reproducible results and evaluating new therapeutics. The CatWalk system is an observer-independent, automated and computerized technique for the assessment of gait performance in rodents. This method has previously been used in adult rodent models of CNS-based movement disorders such as Parkinson's and Huntington's diseases. As motor and gait abnormalities in neuropsychiatric disorders are observed during infancy and adolescence, it became important to validate the CatWalk XT in the gait analysis of adolescent mice and unravel factors that may cause variations in gait performance. Three adolescent wild-type inbred mouse strains, C57BL/6N, DBA/2 and FVB/N, were tested using the CatWalk XT (Version 10.6) for suitable detection settings to characterize several gait parameters at P32 and P42. The same detection settings being suitable for C57BL/6N and DBA/2 mice allowed a direct comparison between the two strains. On the other hand, due to their increased body weight and size, FVB/N mice required different detection settings. The CatWalk XT reliably measured the temporal, spatial, and interlimb coordination parameters in the investigated strains during adolescence. Additionally, significant effects of sex, development, speed and body weight within each strain confirmed the sensitivity of motor and gait functions to these factors. The CatWalk gait analysis of rodents during adolescence, taking the effect of age, strain, sex, speed and body weight into consideration, will decrease intra-laboratory discrepancies and increase the face validity of rodent models of neuropsychiatric disorders.

Three-dimensional analysis of the characteristics of joint motion and gait pattern in a rodent model following spinal nerve ligation

BACKGROUND

The spinal nerve ligation (SNL) rat is well known as the most common rodent model of neuropathic pain without motor deficit. Researchers have performed analyses using only the von Frey and thermal withdrawal tests to evaluate pain intensity in the rat experimental model. However, these test are completely different from the neurological examinations performed clinically. We think that several behavioral reactions must be observed following SNL because the patients with neuropathic pain usually have impaired coordination of the motions of the right-left limbs and right-left joint motion differences. In this study, we attempted to clarify the pain behavioral reactions in SNL rat model as in patients. We used the Kinema-Tracer system for 3D kinematics gait analysis to identify new characteristic parameters of each joint movement and gait pattern.

RESULTS

The effect of SNL on mechanical allodynia was a 47 ± 6.1% decrease in the withdrawal threshold during 1-8 weeks post-operation. Sagittal trajectories of the hip, knee and ankle markers in SNL rats showed a large sagittal fluctuation of each joint while walking. Top minus bottom height of the left hip and knee that represents instability during walking was significantly larger in the SNL than sham rats. Both-foot contact time, which is one of the gait characteristics, was significantly longer in the SNL versus sham rats: 1.9 ± 0.15 s vs. 1.03 ± 0.15 s at 4 weeks post-operation (p = 0.003). We also examined the circular phase time to evaluate coordination of the right and left hind-limbs. The ratio of the right/left circular time was 1.0 ± 0.08 in the sham rats and 0.62 ± 0.15 in the SNL rats at 4 weeks post-operation.

CONCLUSIONS

We revealed new quantitative parameters in an SNL rat model that are directly relevant to the neurological symptoms in patients with neuropathic pain, in whom the von Frey and thermal withdrawal tests are not used at all clinically. This new 3D analysis system can contribute to the analysis of pain intensity of SNL rats in detail similar to human patients' reactions following neuropathic pain.

Therapeutic effects of peripherally administrated neural crest stem cells on pain and spinal cord changes after sciatic nerve transection

BACKGROUND

Severe peripheral nerve injury significantly affects patients' quality of life and induces neuropathic pain. Neural crest stem cells (NCSCs) exhibit several attractive characteristics for cell-based therapies following peripheral nerve injury. Here, we investigate the therapeutic effect of NCSC therapy and associated changes in the spinal cord in a sciatic nerve transection (SNT) model.

METHODS

Complex sciatic nerve gap injuries in rats were repaired with cell-free and cell-laden nerve scaffolds for 12 weeks (scaffold and NCSC groups, respectively). Catwalk gait analysis was used to assess the motor function recovery. The mechanical withdrawal threshold and thermal withdrawal latency were used to assess the development of neuropathic pain. Activation of glial cells was examined by immunofluorescence analyses. Spinal levels of extracellular signal-regulated kinase (ERK), NF-κB P65, brain-derived neurotrophic factor (BDNF), growth-associated protein (GAP)-43, calcitonin gene-related peptide (CGRP), and inflammation factors were calculated by western blot analysis.

RESULTS

Catwalk gait analysis showed that animals in the NCSC group exhibited a higher stand index and Max intensity At (%) relative to those that received the cell-free scaffold (scaffold group) (p < 0.05). The mechanical and thermal allodynia in the medial-plantar surface of the ipsilateral hind paw were significantly relieved in the NCSC group. Sunitinib (SNT)-induced upregulation of glial fibrillary acidic protein (GFAP) (astrocyte) and ionized calcium-binding adaptor molecule 1 (Iba-1) (microglia) in the ipsilateral L4-5 dorsal and ventral horn relative to the contralateral side. Immunofluorescence analyses revealed decreased astrocyte and microglia activation. Activation of ERK and NF-κB signals and expression of transient receptor potential vanilloid 1 (TRPV1) expression were downregulated.

CONCLUSION

NCSC-laden nerve scaffolds mitigated SNT-induced neuropathic pain and improved motor function recovery after sciatic nerve repair. NCSCs also protected the spinal cord from SNT-induced glial activation and central sensitization.

An analysis of the CatWalk XT and a composite score to assess neurofunctional deficits after photothrombosis in mice

The purpose of this study was to evaluate CatWalk's capability for assessing the functional outcome after photothrombotic stroke affecting the motor cortex of mice. Mice were tested up to 21 days after photothrombosis or sham surgery using CatWalk, and a composite score assessing functional deficits (neuroscore). The neuroscore demonstrated deficits of the contralateral forelimb for more than two weeks after stroke. There were no asymmetric or coordinative dysfunctions of limbs detected by CatWalk. However, CatWalk data revealed impairment of locomotion speed and its depending parameters for one-week after stroke in strong correlation to the neuroscore. Data suggest that the composite neuroscore allows to more sensitively and precisely specify and quantify photothrombosis-induced hemisyndromes than CatWalk.

Combination of Defined CatWalk Gait Parameters for Predictive Locomotion Recovery in Experimental Spinal Cord Injury Rat Models

In many preclinical spinal cord injury (SCI) studies, assessment of locomotion recovery is key to understanding the effectiveness of the experimental intervention. In such rat SCI studies, the most basic locomotor recovery scoring system is a subjective observation of animals freely roaming in an open field, the Basso Beattie Bresnahan (BBB) score. In comparison, CatWalk is an automated gait analysis system, providing further parameter specifications. Although together the CatWalk parameters encompass gait, studies consistently report single parameters, which differ in significance from other behavioral assessments. Therefore, we believe no single parameter produced by the CatWalk can represent the fully-coordinated motion of gait. Typically, other locomotor assessments, such as the BBB score, combine several locomotor characteristics into a representative score. For this reason, we ranked the most distinctive CatWalk parameters between uninjured and SC injured rats. Subsequently, we combined nine of the topmost parameters into an SCI gait index score based on linear discriminant analysis (LDA). The resulting combination was applied to assess gait recovery in SCI experiments comprising of three thoracic contusions, a thoracic dorsal hemisection, and a cervical dorsal column lesion model. For thoracic lesions, our unbiased machine learning model revealed gait differences in lesion type and severity. In some instances, our LDA was found to be more sensitive in differentiating recovery than the BBB score alone. We believe the newly developed gait parameter combination presented here should be used in CatWalk gait recovery work with preclinical thoracic rat SCI models.

Modeling Complex Orthopedic Trauma in Rodents: Bone, Muscle and Nerve Injury and Healing

Orthopedic injury can occur from a variety of causes including motor vehicle collision, battlefield injuries or even falls from standing. Persistent limb pain is common after orthopedic injury or surgery and presents a unique challenge, as the initiating event may result in polytrauma to bone, muscle, and peripheral nerves. It is imperative that we understand the tissue-specific and multicellular response to this unique type of injury in order to best develop targeted treatments that improve healing and regeneration. In this Mini Review we will first discuss current rodent models of orthopedic trauma/complex orthotrauma. In the second section, we will focus on bone-specific outcomes including imaging modalities, biomechanical testing and immunostaining for markers of bone healing/turnover. In the third section, we will discuss muscle-related pathology including outcome measures of fibrosis, muscle regeneration and tensile strength measurements. In the fourth section, we will discuss nervous system-related pathology including outcome measures of pain-like responses, both reflexive and non-reflexive. In all sections we will consider parallels between preclinical outcome measures and the functional and mechanistic findings of the human condition.

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

Injuries of the peripheral nervous system are common among the population affecting around 3% of all trauma patients. This high clinical need in the field of peripheral nerve injury and regeneration has been steadily driving experimental and epidemiological research. Thereby, it is crucial to determine the exact degree of recovery of end-organ function. Regeneration after nerve injuries is assessed by a wide variety of techniques and pre-clinical model systems, where rodent models are among the most widely used. However, results from rodents are difficult to translate to human patients in general, and reproducible and comparable assessment of functional recovery is of highest importance. Computerized gait analysis allows comprehensive acquisition of locomotor function. As the animals cross the recording device voluntarily, functional recovery is assessable with a minimum degree of human interference on their behavior. This article aims to give a detailed overview on the existing literature on CatWalk gait analysis in rodent models of peripheral nerve injuries of upper and lower extremities, e.g. axonotmesis, neurotmesis or fibrosis, with special emphasis on differences between models. Researchers interested in assessment of locomotor function in such models will especially benefit from this work as it will provide them with an overview of the various experimental setups and expected outcomes. This work also addresses potential pitfalls and hurdles in order to promote well designed, comparable studies allowing for accelerated development of therapeutic strategies in peripheral repair and regeneration.

Pain behaviour assessments by gait and weight bearing in surgically induced osteoarthritis and inflammatory arthritis

OBJECTIVE

. Osteoarthritis (OA) is the most common cause of joint pain. Animal models and relevant assays for measurement of pain-related behaviours are important tools for studies of mechanisms inducing and sustaining pain in OA. The aim of this study was to evaluate two different assessments of weight bearing; stationary and during locomotion, and to explore their feasibility to detect analgesic effects in vivo. Two fundamentally different mouse models of joint arthritis were investigated; surgical transection of the anterior cruciate ligament (ACLT) resulting in destabilization of the joint with subsequent structural deterioration resembling OA, and monoarthritis induced by injection of Complete Freund´s Adjuvant (CFA) into the ankle joint capsule.

DESIGN

. Mice were subjected to ACLT or CFA injection into the ankle joint. Stationary weight bearing was performed up to twenty weeks after ACLT, and for two weeks after CFA. In addition, mice with CFA-induced monoarthritis were assessed for gait and weight bearing during locomotion, and the effects of an anti-NGF antibody (MEDI578) were tested. End point histopathological analysis was performed in knee joints of ACLT mice, and in mice with ankle joint injection of CFA at eight days after injection.

RESULTS

. Both the surgical ACLT and CFA-induced monoarthritis reduced stationary weight bearing on the affected paw. The reduction in weight bearing was compensated by all other legs, but differently when stationary compared to during locomotion in the CFA-injected mice. The behavioural effects of ACLT correlated to the structural changes of the joint. In the CFA-induced monoarthritis, showing a massive infiltration of inflammatory cells at 8 days, MEDI578 significantly attenuated the pain-like behaviours.

CONCLUSIONS

. The pain-like behaviour detected is mainly due to inflammation and not to the same degree to structural changes in the joint. Behavioural effects after ACLT were too small for pharmacological evaluation of pain relief. In contrast, the inflammation after CFA injection caused a long-lasting effect on pain-like behaviours such as weight bearing and gait, which could be attenuated by administration of an anti NGF antibody.

Visual Gait Lab: A user-friendly approach to gait analysis

BACKGROUND

Gait analysis forms a critical part of many lab workflows, ranging from those interested in preclinical neurological models to others who use locomotion as part of a standard battery of tests. Unfortunately, while paw detection can be semi-automated, it becomes generally a time-consuming process with error corrections. Improvement in paw tracking would aid in better gait analysis performance and experience.

NEW METHOD

Here we show the use of Visual Gait Lab (VGL), a high-level software with an intuitive, easy to use interface, that is built on DeepLabCut™. VGL is optimized to generate gait metrics and allows for quick manual error corrections. VGL comes with a single executable, streamlining setup on Windows systems. We demonstrate the use of VGL to analyze gait.

RESULTS

Training and evaluation of VGL were conducted using 200 frames (80/20 train-test split) of video from mice walking on a treadmill. The trained network was then used to visually track paw placements to compute gait metrics. These are processed and presented on the screen where the user can rapidly identify and correct errors.

COMPARISON WITH EXISTING METHODS

Gait analysis remains cumbersome, even with commercial software due to paw detection errors. DeepLabCut™ is an alternative that can improve visual tracking but is not optimized for gait analysis functionality.

CONCLUSIONS

VGL allows for gait analysis to be performed in a rapid, unbiased manner, with a set-up that can be easily implemented and executed by those without a background in computer programming.

Gait analysis and muscle weight analysis after lower extremity fractures in a small animal model

BACKGROUND

Besides adequate healing of bone and soft tissues, mobility represents a significant factor in functional outcome after lower extremity fractures. Although gait analysis is gaining clinical interest and importance in the rehabilitation of patients with fractures, it is rarely used in experimental fracture healing research. The aim of this study is to establish an accurate gait analysis method for fracture healing research in small animal models and to evaluate the influence of a lower extremity fracture on gait pattern and muscle atrophy in rats.

RESEARCH QUESTION

How does an intramedullary stabilized femur fracture influence the gait pattern and muscle atrophy during fracture healing in rats?

METHODS

An isolated femur fracture with intramedullary stabilization was induced in 26 Sprague Dawley rats. Different gait parameters (e.g. intensity, print area, stand duration, duty cycle, and swing speed) were evaluated with the CatWalk gait analysis system during the fracture healing process. Furthermore, muscle weight analysis was performed at different time points.

RESULTS

The gait analyses with the CatWalk system showed a high correlation with the osteogenesis of fracture healing in this model. Muscle atrophy increased during the early fracture healing stages and then decreased in the later stages.

SIGNIFICANCE

We are the first to show that the CatWalk system is a useful tool to perform gait analyses after lower extremity fractures in a murine model. These results could form a basis for future gait analyses research in fracture healing studies to improve knowledge about bone regeneration and rehabilitation after lower extremity fractures.

Using animal models to evaluate the functional consequences of anesthesia during early neurodevelopment

Fifteen years ago Olney and colleagues began using animal models to evaluate the effects of anesthetic and sedative agents (ASAs) on neurodevelopment. The results from ongoing studies indicate that, under certain conditions, exposure to these drugs during development induces an acute elevated apoptotic neurodegenerative response in the brain and long-term functional impairments. These animal models have played a significant role in bringing attention to the possible adverse effects of exposing the developing brain to ASAs when few concerns had been raised previously in the medical community. The apoptotic degenerative response resulting from neonatal exposure to ASAs has been replicated in many studies in both rodents and non-human primates, suggesting that a similar effect may occur in humans. In both rodents and non-human primates, significantly increased levels of apoptotic degeneration are often associated with functional impairments later in life. However, behavioral deficits following developmental ASA exposure have not been consistently reported even when significantly elevated levels of apoptotic degeneration have been documented in animal models. In the present work, we review this literature and propose a rodent model for assessing potential functional deficits following neonatal ASA exposure with special reference to experimental design and procedural issues. Our intent is to improve test sensitivity and replicability for detecting subtle behavioral effects, and thus enhance the translational significance of ASA models.

Intraneural IFG-1 in Cryopreserved Nerve Isografts Increase Neural Regeneration and Functional Recovery in the Rat Sciatic Nerve

BACKGROUND

Insulin-like growth factor 1 (IGF-1) was found to stimulate Schwann cell mitosis. Exogenous IGF-1 may improve nerve regeneration after cryopreservation.

OBJECTIVE

To evaulate the effect of intraneural administration of IGF-1 in cryopreserved nerve isografts.

METHODS

Eighteen millimeter grafts were used for bridging an 18-mm defect in the rat sciatic nerve. A total of 57 rats were randomly divided into three groups: (1) autograft (Group 1); (2) cryopreserved isograft (Group 2); (3) cryopreserved isograft with intraneural IGF-1 administration (Group 3). 12 weeks after surgery, functional recovery (Sciatic functional index [SFI], Swing speed [SS], nerve conduction velocity [NCV], amplitude of compound motor action potentials [CMAP], and gastrocnemius muscle index [GMI]) and nerve regeneration (myelin sheath area, total fiber counts, fiber density, and fiber width) were all evaluated.

RESULTS

The intraneural injection of IGF-1 significantly improved SFI and SS at weeks 10 and 12. There were no statistical differences between Groups 1 and 3 in any of the SFI or SS evaluations. CMAP and NCV in Group 1 were significantly higher than in Groups 2 and 3, and Group 3 had significantly higher CMAP and NCV compared to Group 2. No significant differences were found in fiber width. The number of nerve fibers, percentage of myelinated fibers, fiber density, and GMI was significantly higher in Group 1 compared to Group 2, but no significant differences were found between Groups 1 and 3.

CONCLUSION

The results show that intraneural injection of IGF-1 in an 18 mm cryopreserved isograft improve axonal regeneration and functional recovery.

Paw-Print Analysis of Contrast-Enhanced Recordings (PrAnCER): A Low-Cost, Open-Access Automated Gait Analysis System for Assessing Motor Deficits

Gait analysis is used to quantify changes in motor function in many rodent models of disease. Despite the importance of assessing gait and motor function in many areas of research, the available commercial options have several limitations such as high cost and lack of accessible, open code. To address these issues, we developed PrAnCER, Paw-Print Analysis of Contrast-Enhanced Recordings, for automated quantification of gait. The contrast-enhanced recordings are produced by using a translucent floor that obscures objects not in contact with the surface, effectively isolating the rat's paw prints as it walks. Using these videos, our simple software program reliably measures a variety of spatiotemporal gait parameters. To demonstrate that PrAnCER can accurately detect changes in motor function, we employed a haloperidol model of Parkinson's disease (PD). We tested rats at two doses of haloperidol: high dose (0.30 mg/kg) and low dose (0.15 mg/kg). Haloperidol significantly increased stance duration and hind paw contact area in the low dose condition, as might be expected in a PD model. In the high dose condition, we found a similar increase in contact area but also an unexpected increase in stride length. With further research, we found that this increased stride length is consistent with the bracing-escape phenomenon commonly observed at higher doses of haloperidol. Thus, PrAnCER was able to detect both expected and unexpected changes in rodent gait patterns. Additionally, we confirmed that PrAnCER is consistent and accurate when compared with manual scoring of gait parameters.

Systematic data analysis and data mining in CatWalk gait analysis by heat mapping exemplified in rodent models for neurodegenerative diseases

BACKGROUND

Motor impairment appears as a characteristic symptom of several diseases and injuries. Therefore, tests for analyzing motor dysfunction are widely applied across preclinical models and disease stages. Among those, gait analysis tests are commonly used, but they generate a huge number of gait parameters. Thus, complications in data analysis and reporting raise, which often leads to premature parameter selection.

NEW METHODS

In order to avoid arbitrary parameter selection, we present here a systematic initial data analysis by utilizing heat-maps for data reporting. We exemplified this approach within an intervention study, as well as applied it to two longitudinal studies in rodent models related to Parkinson's disease (PD) and Huntington disease (HD).

RESULTS

The systematic initial data analysis (IDA) is feasible for exploring gait parameters, both in experimental and longitudinal studies. The resulting heat maps provided a visualization of gait parameters within a single chart, highlighting important clusters of differences.

COMPARISON WITH EXISTING METHOD

Often, premature parameter selection is practiced, lacking comprehensiveness. Researchers often use multiple separated graphs on distinct gait parameters for reporting. Additionally, negative results are often not reported.

CONCLUSIONS

Heat mapping utilized in initial data analysis is advantageous for reporting clustered gait parameter differences in one single chart and improves data mining.

Gait Assessment of Pain and Analgesics: Comparison of the DigiGait™ and CatWalk™ Gait Imaging Systems

Investigation of pain requires measurements of nociceptive sensitivity and other pain-related behaviors. Recent studies have indicated the superiority of gait analysis over traditional evaluations (e.g., skin sensitivity and sciatic function index [SFI]) in detecting subtle improvements and deteriorations in animal models. Here, pain-related gait parameters, whose criteria include (1) alteration in pain models, (2) correlation with nociceptive threshold, and (3) normalization by analgesics, were identified in representative models of neuropathic pain (spared nerve injury: coordination data) and inflammatory pain (intraplantar complete Freund’s adjuvant: both coordination and intensity data) in the DigiGait™ and CatWalk™ systems. DigiGait™ had advantages in fixed speed (controlled by treadmill) and dynamic SFI, while CatWalk™ excelled in intrinsic velocity, intensity data, and high-quality 3D images. Insights into the applicability of each system may provide guidance for selecting the appropriate gait imaging system for different animal models and optimization for future pain research.

Exogenous Neural Precursor Cell Transplantation Results in Structural and Functional Recovery in a Hypoxic-Ischemic Hemiplegic Mouse Model

Cerebral palsy (CP) is a common pediatric neurodevelopmental disorder, frequently resulting in motor and developmental deficits and often accompanied by cognitive impairments. A regular pathobiological hallmark of CP is oligodendrocyte maturation impairment resulting in white matter (WM) injury and reduced axonal myelination. Regeneration therapies based on cell replacement are currently limited, but neural precursor cells (NPCs), as cellular support for myelination, represent a promising regeneration strategy to treat CP, although the transplantation parameters (e.g., timing, dosage, mechanism) remain to be determined. We optimized a hemiplegic mouse model of neonatal hypoxia-ischemia that mirrors the pathobiological hallmarks of CP and transplanted NPCs into the corpus callosum (CC), a major white matter structure impacted in CP patients. The NPCs survived, engrafted, and differentiated morphologically in male and female mice. Histology and MRI showed repair of lesioned structures. Furthermore, electrophysiology revealed functional myelination of the CC (e.g., restoration of conduction velocity), while cylinder and CatWalk tests demonstrated motor recovery of the affected forelimb. Endogenous oligodendrocytes, recruited in the CC following transplantation of exogenous NPCs, are the principal actors in this recovery process. The lack of differentiation of the transplanted NPCs is consistent with enhanced recovery due to an indirect mechanism, such as a trophic and/or “bio-bridge” support mediated by endogenous oligodendrocytes. Our work establishes that transplantation of NPCs represents a viable therapeutic strategy for CP treatment, and that the enhanced recovery is mediated by endogenous oligodendrocytes. This will further our understanding and contribute to the improvement of cellular therapeutic strategies.

Quantitative Multimodal Evaluation of Passaging Human Neural Crest Stem Cells for Peripheral Nerve Regeneration

Peripheral nerve injury is a major burden to societies worldwide, however, current therapy options (e.g. autologous nerve grafts) are unable to produce satisfactory outcomes. Many studies have shown that stem cell transplantation holds great potential for peripheral nerve repair, and human neural crest stem cells (hNCSCs), which give rise to a variety of tissues in the peripheral nervous system, are particularly promising. NCSCs are one of the best candidates for clinical translation, however, to ensure the viability and quality of NCSCs for research and clinical use, the effect of in vitro cell passaging on therapeutic effects needs be evaluated given that passaging is required to expand NCSCs to meet the demands of transplantation in preclinical research and clinical trials. To date, no study has investigated the quality of NCSCs past the 5th passage in vivo. In this study, we employed a multimodal evaluation system to investigate changes in outcomes between transplantation with 5th (p5) and 6th passage (p6) NCSCs in a 15 mm rat sciatic nerve injury and repair model. Using CatWalk gait analysis, gastrocnemius muscle index, electrophysiology, immunohistochemistry, and histomorphometric analysis, we showed that p6 NCSCs demonstrated decreased cell survival, Schwann-cell differentiation, axonal growth, and functional outcomes compared to p5 NCSCs (all p < 0.05). In conclusion, p6 NCSCs showed significantly reduced therapeutic efficacy compared to p5 NCSCs for peripheral nerve regeneration.

A companion to the preclinical common data elements for physiologic data in rodent epilepsy models. A report of the TASK3 Physiology Working Group of the ILAE/AES Joint Translational Task Force

The International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force created the TASK3 working groups to create common data elements (CDEs) for various aspects of preclinical epilepsy research studies, which could help improve standardization of experimental designs. This article concerns the parameters that can be measured to assess the physiologic condition of the animals that are used to study rodent models of epilepsy. Here we discuss CDEs for physiologic parameters measured in adult rats and mice such as general health status, temperature, cardiac and respiratory function, and blood constituents. We provide detailed CDE tables and case report forms (CRFs), and with this companion manuscript we discuss the monitoring of different aspects of physiology of the animals. The CDEs, CRFs, and companion paper are available to all researchers, and their use will benefit the harmonization and comparability of translational preclinical epilepsy research. The ultimate hope is to facilitate the development of biomarkers and new treatments for epilepsy.

Optimal electrical stimulation boosts stem cell therapy in nerve regeneration

Peripheral nerve injuries often lead to incomplete recovery and contribute to significant disability to approximately 360,000 people in the USA each year. Stem cell therapy holds significant promise for peripheral nerve regeneration, but maintenance of stem cell viability and differentiation potential in vivo are still major obstacles for translation. Using a made-in-house 96-well vertical electrical stimulation (ES) platform, we investigated the effects of different stimulating pulse frequency, duration and field direction on human neural crest stem cell (NCSC) differentiation. We observed dendritic morphology with enhanced neuronal differentiation for NCSCs cultured on cathodes subject to 20 Hz, 100μs pulse at a potential gradient of 200 mV/mm. We further evaluated the effect of a novel cell-based therapy featuring optimized pulsatile ES of NCSCs for in vivo transplantation following peripheral nerve regeneration. 15 mm critical-sized sciatic nerve injuries were generated with subsequent surgical repair in sixty athymic nude rats. Injured animals were randomly assigned into five groups (N = 12 per group): blank control, ES, NCSC, NCSC + ES, and autologous nerve graft. The optimized ES was applied immediately after surgical repair for 1 h in ES and NCSC + ES groups. Recovery was assessed by behavioral (CatWalk gait analysis), wet muscle-mass, histomorphometric, and immunohistochemical analyses at either 6 or 12 weeks after surgery (N = 6 per group). Gastrocnemius muscle wet mass measurements in ES + NCSC group were comparable to autologous nerve transplantation and significantly higher than other groups (p < 0.05). Quantitative histomorphometric analysis and catwalk gait analysis showed similar improvements by ES on NCSCs (p < 0.05). A higher number of viable NCSCs was shown via immunochemical analysis, with higher Schwann cell (SC) differentiation in the NCSC + ES group compared to the NCSC group (p < 0.05). Overall, ES on NCSC transplantation significantly enhanced nerve regeneration after injury and repair, and was comparable to autograft treatment. Thus, ES can be a potent alternative to biochemical and physical cues for modulating stem cell survival and differentiation. This novel cell-based intervention presents an effective and safe approach for improved outcomes after peripheral nerve repair.

Heparin-Poloxamer Thermosensitive Hydrogel Loaded with bFGF and NGF Enhances Peripheral Nerve Regeneration in Diabetic Rats

Peripheral nerve injury (PNI) is a major burden to society with limited therapeutic options, and novel biomaterials have great potential for shifting the current paradigm of treatment. With a rising prevalence of chronic illnesses such as diabetes mellitus (DM), treatment of PNI is further complicated, and only few studies have proposed therapies suitable for peripheral nerve regeneration in DM. To provide a supportive environment to restore structure and/or function of nerves in DM, we developed a novel thermo-sensitive heparin-poloxamer (HP) hydrogel co-delivered with basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) in diabetic rats with sciatic nerve crush injury. The delivery vehicle not only had a good affinity for large amounts of growth factors (GFs), but also controlled their release in a steady fashion, preventing degradation in vitro. In vivo, compared with HP hydrogel alone or direct GFs administration, GFs-HP hydrogel treatment is more effective at facilitating Schwann cell (SC) proliferation, leading to an increased expression of nerve associated structural proteins, enhanced axonal regeneration and remyelination, and improved recovery of motor function (all p < 0.05). Our mechanistic investigation also revealed that these neuroprotective and neuroregenerative effects of the GFs-HP hydrogel may be associated with activations of phosphatidylinositol 3 kinase and protein kinase B (PI3K/Akt), janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3), and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathways. Our work provides a promising therapy option for peripheral nerve regeneration in patients with DM.

Biomimetic neural scaffolds: a crucial step towards optimal peripheral nerve regeneration

Peripheral nerve injury is a common disease that affects more than 20 million people in the United States alone and remains a major burden to society. The current gold standard treatment for critical-sized nerve defects is autologous nerve graft transplantation; however, this method is limited in many ways and does not always lead to satisfactory outcomes. The limitations of autografts have prompted investigations into artificial neural scaffolds as replacements, and some neural scaffold devices have progressed to widespread clinical use; scaffold technology overall has yet to be shown to be consistently on a par with or superior to autografts. Recent advances in biomimetic scaffold technologies have opened up many new and exciting opportunities, and novel improvements in material, fabrication technique, scaffold architecture, and lumen surface modifications that better reflect biological anatomy and physiology have independently been shown to benefit overall nerve regeneration. Furthermore, biomimetic features of neural scaffolds have also been shown to work synergistically with other nerve regeneration therapy strategies such as growth factor supplementation, stem cell transplantation, and cell surface glycoengineering. This review summarizes the current state of neural scaffolds, highlights major advances in biomimetic technologies, and discusses future opportunities in the field of peripheral nerve regeneration.

Cortical remodeling after electroacupuncture therapy in peripheral nerve repairing model

Electroacupuncture (EA) is an alternative therapy for peripheral nerve injury (PNI). The treatment relies on post-therapeutic effect rather than real-time effect. We utilized fMRI to clarify the resting-state alteration caused by sustained effect of EA on peripheral nerve repairing model. Twenty-four rats were divided equally into three groups: normal group, model group and intervention group. Rats of the model and intervention group underwent sciatic nerve transection and direct anastomosis. EA intervention at ST-36 and GB-30 was conducted continuously for 4 months on the intervention group. Behavioral assessments and fMRI were performed 1 month and 4 months after surgery. Intervention group showed significant improvement on the gait parameters max contact mean intensity (MCMI) and thermal withdrawal latency (TWL) than model group. EA-related sustained effects of amplitude of low frequency fluctuations (ALFF) could be described as a remolding pattern of somatosensory area and sensorimotor integration regions which presented higher ALFF in the contralateral hemisphere and lower in the ipsilateral hemisphere than model group. Interhemispheric functional connectivity (FC) analysis showed a significantly lower FC after EA therapy between the largest significantly different clusters in bilateral somatosensory cortices than the model group 4 months after surgery(p < 0.05). And the model group presented significantly higher FC than the normal group at both two time-points (p < 0.01). The sustained effect of EA on peripheral nerve repairing rats appeared to induce both regional and extensive neuroplasticity in bilateral hemispheres. We proposed that such EA-related effect was a reverse of maladaptive plasticity caused by PNI.

Automated Gait Analysis in Mice with Chronic Constriction Injury

The von Frey test is a classical method that has been widely used to examine the sensory function of neuropathic pain animals. However, it has some disadvantages such as subjective data and the requirement of a skilled, experienced experimenter. To date, a variety of modifications have improved the von Frey method, but it still has a few limitations. Recent reports have suggested that gait analysis produces more accurate and objective data from the neuropathic animals. This protocol demonstrates how to perform the automated gait analysis to determine the degree of neuropathic pain in mice. After several days of acclimation, the mice were allowed to walk freely on the glass floor to illuminate footprints. Then, quantification of the footprints and gait were performed through video clips with automatic analysis of various walking parameters, such as area of paw print, swing time, angle of paw, etc. The main purpose of this study is to describe the methodology of automated gait analysis and briefly compare it with data from the classical sensory test using von Frey filament.