The need for speed in rodent locomotion analyses

The relationship between changes in inflammation and locomotor function in sensory phenotypes of central neuropathic pain after spinal cord injury

Introduction

Central neuropathic pain (CNP) commonly develops in patients after spinal cord injury (SCI), causing debilitating symptoms and sensory abnormalities to mechanical and thermal stimuli. The biological variability of pain phenotypes in individuals has limited the number of positive outcomes. Thus, it is necessary to investigate the physiological processes contributing to sensory changes that develop over time.

Objective

To investigate the physiological processes contributing to neuropathic pain sensory changes and locomotor impairments with sensory phenotypes that develop over time.

Methods

Using the tail flick and von Frey tests, we performed hierarchical clustering to determine the subpopulation of rats that developed thermal and mechanical sensory abnormalities. To measure inflammation as a potential mediator of CNP phenotypes, we used flow cytometry and immunohistochemistry. Finally, to assess the secondary effects on locomotor recovery, up to 8 weeks after injury, we used the CatWalk test to assess multiple parameters of gait.

Results

The von Frey test showed a subpopulation of SCI rats that were hyposensitive to mechanical stimuli from 6 to 8 weeks after injury. The tail flick test showed a subpopulation of SCI rats that were hypersensitive to thermal stimuli at 1 week and 3 to 8 weeks after injury. Although there were no differences in inflammatory cells between subpopulations, we did see significant changes in locomotor recovery between rats with and without sensory abnormalities.

Conclusion

The myeloid cell population at large is not affected by mechanical or thermal phenotypes of pain in this model; however, locomotor recovery is impaired depending on the pain phenotype present. Further investigation into acute inflammatory cells may be insightful for predicting the development of pain phenotypes.

Myelinated peripheral axons are more vulnerable to mechanical trauma in a model of enlarged axonal diameters

The velocity of axonal impulse propagation is facilitated by myelination and axonal diameters. Both parameters are frequently impaired in peripheral nerve disorders, but it is not known if the diameters of myelinated axons affect the liability to injury or the efficiency of functional recovery. Mice lacking the adaxonal myelin protein chemokine-like factor-like MARVEL-transmembrane domain-containing family member-6 (CMTM6) specifically from Schwann cells (SCs) display appropriate myelination but increased diameters of peripheral axons. Here we subjected Cmtm6-cKo mice as a model of enlarged axonal diameters to a mild sciatic nerve compression injury that causes temporarily reduced axonal diameters but otherwise comparatively moderate pathology of the axon/myelin-unit. Notably, both of these pathological features were worsened in Cmtm6-cKo compared to genotype-control mice early post-injury. The increase of axonal diameters caused by CMTM6-deficiency thus does not override their injury-dependent decrease. Accordingly, we did not detect signs of improved regeneration or functional recovery after nerve compression in Cmtm6-cKo mice; depleting CMTM6 in SCs is thus not a promising strategy toward enhanced recovery after nerve injury. Conversely, the exacerbated axonal damage in Cmtm6-cKo nerves early post-injury coincided with both enhanced immune response including foamy macrophages and SCs and transiently reduced grip strength. Our observations support the concept that larger peripheral axons are particularly susceptible toward mechanical trauma.

Sensory feedback and central neuronal interactions in mouse locomotion

Locomotion is a complex process involving specific interactions between the central neural controller and the mechanical components of the system. The basic rhythmic activity generated by locomotor circuits in the spinal cord defines rhythmic limb movements and their central coordination. The operation of these circuits is modulated by sensory feedback from the limbs providing information about the state of the limbs and the body. However, the specific role and contribution of central interactions and sensory feedback in the control of locomotor gait and posture remain poorly understood. We use biomechanical data on quadrupedal locomotion in mice and recent findings on the organization of neural interactions within the spinal locomotor circuitry to create and analyse a tractable mathematical model of mouse locomotion. The model includes a simplified mechanical model of the mouse body with four limbs and a central controller composed of four rhythm generators, each operating as a state machine controlling the state of one limb. Feedback signals characterize the load and extension of each limb as well as postural stability (balance). We systematically investigate and compare several model versions and compare their behaviour to existing experimental data on mouse locomotion. Our results highlight the specific roles of sensory feedback and some central propriospinal interactions between circuits controlling fore and hind limbs for speed-dependent gait expression. Our models suggest that postural imbalance feedback may be critically involved in the control of swing-to-stance transitions in each limb and the stabilization of walking direction.

Methodology of using acoustic emissions for enhancing rodent behavioral analysis

Rodent models of behavior used in the fields of neuroscience and psychology generate a wealth of multimodal data. For instance, as a rodent moves and behaves in its environment, muscle contractions apply subtle forces to any surface the animal contacts. These forces generate acoustic waves that propagate through the waveguide as Lamb and shear horizontal (SH) waves and contain information about the rodent's physiology, behavior, and underlying psychological state. If the information in these waves were to be tapped, it would provide a novel, non-invasive way to study rodent behavior. This article lays the foundations for using guided ultrasonic waves generated by a mouse's movement on an aluminum plate for detecting behavior and drawing inferences about acoustic startle responses. The experimental setup involves piezoelectric sensors capturing the waves generated by the rodent's movement, which are then stored as discrete acoustic emission (AE) hits using an amplitude threshold-based data acquisition system. This method of data acquisition ensures that data collection occurs only when the animal moves or behaves, and each movement/behavior is represented by values of features within the generated wavepackets (AE hits). Through open field tests with C57BL/6J mice, utilizing piezoelectric sensors and the DAQ system, it was observed that every movement/behavior of the animal generated Lamb wavepackets within the frequency range of 20 kHz to 100 kHz. Furthermore, rearing behavior in the animals also led to the generation of SH wavepackets in the frequency range of 75 kHz to 230 kHz. This criterion was subsequently employed to detect rearing behavior. In the acoustic startle response test, where the animals' responses to intense sound pulse were recorded, AE hits' features proved useful in quantifying the response. These experimental findings validate the proposed technology's practicality and demonstrate its capability to enhance studies of rodent behavior.

Sensory Feedback and Central Neuronal Interactions in Mouse Locomotion

Locomotion is a complex process involving specific interactions between the central neural controller and the mechanical components of the system. The basic rhythmic activity generated by locomotor circuits in the spinal cord defines rhythmic limb movements and their central coordination. The operation of these circuits is modulated by sensory feedback from the limbs providing information about the state of the limbs and the body. However, the specific role and contribution of central interactions and sensory feedback in the control of locomotor gait and posture remain poorly understood. We use biomechanical data on quadrupedal locomotion in mice and recent findings on the organization of neural interactions within the spinal locomotor circuitry to create and analyze a tractable mathematical model of mouse locomotion. The model includes a simplified mechanical model of the mouse body with four limbs and a central controller composed of four rhythm generators, each operating as a state machine controlling the state of one limb. Feedback signals characterize the load and extension of each limb as well as postural stability (balance). We systematically investigate and compare several model versions and compare their behavior to existing experimental data on mouse locomotion. Our results highlight the specific roles of sensory feedback and some central propriospinal interactions between circuits controlling fore and hind limbs for speed-dependent gait expression. Our models suggest that postural imbalance feedback may be critically involved in the control of swing-to-stance transitions in each limb and the stabilization of walking direction.

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.

3D mouse pose from single-view video and a new dataset

We present a method to infer the 3D pose of mice, including the limbs and feet, from monocular videos. Many human clinical conditions and their corresponding animal models result in abnormal motion, and accurately measuring 3D motion at scale offers insights into health. The 3D poses improve classification of health-related attributes over 2D representations. The inferred poses are accurate enough to estimate stride length even when the feet are mostly occluded. This method could be applied as part of a continuous monitoring system to non-invasively measure animal health, as demonstrated by its use in successfully classifying animals based on age and genotype. We introduce the Mouse Pose Analysis Dataset, the first large scale video dataset of lab mice in their home cage with ground truth keypoint and behavior labels. The dataset also contains high resolution mouse CT scans, which we use to build the shape models for 3D pose reconstruction.

Degeneration of muscle spindles in a murine model of Pompe disease

Pompe disease is a debilitating medical condition caused by a functional deficiency of lysosomal acid alpha-glucosidase (GAA). In addition to muscle weakness, people living with Pompe disease experience motor coordination deficits including an instable gait and posture. We reasoned that an impaired muscle spindle function might contribute to these deficiencies and therefore analyzed proprioception as well as muscle spindle structure and function in 4- and 8-month-old Gaa-/- mice. Gait analyses showed a reduced inter-limb and inter-paw coordination in Gaa-/- mice. Electrophysiological analyses of single-unit muscle spindle proprioceptive afferents revealed an impaired sensitivity of the dynamic and static component of the stretch response. Finally, a progressive degeneration of the sensory neuron and of the intrafusal fibers was detectable in Gaa-/- mice. We observed an increased abundance and size of lysosomes, a fragmentation of the inner and outer connective tissue capsule and a buildup of autophagic vacuoles in muscle spindles from 8-month-old Gaa-/- mice, indicating lysosomal defects and an impaired autophagocytosis. These results demonstrate a structural and functional degeneration of muscle spindles and an altered motor coordination in Gaa-/- mice. Similar changes could contribute to the impaired motor coordination in patients living with Pompe disease.

Effects of Repeat Test Exposure on Gait Parameters in Naïve Lewis Rats

Rodent gait analysis has emerged as a powerful, quantitative behavioral assay to characterize the pain and disability associated with movement-related disorders. In other behavioral assays, the importance of acclimation and the effect of repeated testing have been evaluated. However, for rodent gait analysis, the effects of repeated gait testing and other environmental factors have not been thoroughly characterized. In this study, fifty-two naïve male Lewis rats ages 8 to 42 weeks completed gait testing at semi-random intervals for 31 weeks. Gait videos and force plate data were collected and processed using a custom MATLAB suite to calculate velocity, stride length, step width, percentage stance time (duty factor), and peak vertical force data. Exposure was quantified as the number of gait testing sessions. Linear mixed effects models were used to evaluate the effects of velocity, exposure, age, and weight on animal gait patterns. Relative to age and weight, repeated exposure was the dominant parameter affecting gait variables with significant effects on walking velocity, stride length, fore and hind limb step width, fore limb duty factor, and peak vertical force. From exposure 1 to 7, average velocity increased by approximately 15 cm/s. Together, these data indicate arena exposure had large effects on gait parameters and should be considered in acclimation protocols, experimental design, and subsequent data analysis of rodent gait data.

Neuroprotective and Immunomodulatory Effects of Probiotics in a Rat Model of Parkinson's Disease

It is now well recognized that a bidirectional relationship between gut microbiota and the brain, referred to as the gut-brain axis, plays a prominent role in maintaining homeostasis and that a disruption in this axis can result in neuroinflammatory response and neurological disorders such as Parkinson's disease (PD). The protective action of probiotics such as Bifidobacterium animalis ssp. lactis Bb12 and Lactobacillus rhamnosus GG in various animal models of PD has been reported. Therefore, in this study, we used an inflammatory model of PD to assess the effects of a combination of these two probiotics (Microbiot^®) on motor behavior as well as on the response of microglia, including microglia morphology, to gain a better understanding of their mechanism of action. Microbiot^® (300 µL) was administered orally once daily for 15 days in a lipopolysaccharide-induced PD model using male Wistar rats. Although LPS-induced motor asymmetry in cylinder test was not affected by Microbiot^®, impairment of motor coordination in the narrow-beam test was significantly reduced by this probiotic. Moreover, Microbiot^® treatment reduced microglial activation suggesting an anti-inflammatory effect. While further mechanistic investigation of Microbiot^® in neurodegenerative diseases is warranted, our results support the potential utility of probiotics in PD.

A buprenorphine depot formulation provides effective sustained post-surgical analgesia for 72 h in mouse femoral fracture models

Adequate pain management is essential for ethical and scientific reasons in animal experiments and should completely cover the period of expected pain without the need for frequent re-application. However, current depot formulations of Buprenorphine are only available in the USA and have limited duration of action. Recently, a new microparticulate Buprenorphine formulation (BUP-Depot) for sustained release has been developed as a potential future alternative to standard formulations available in Europe. Pharmacokinetics indicate a possible effectiveness for about 72 h. Here, we investigated whether the administration of the BUP-Depot ensures continuous and sufficient analgesia in two mouse fracture models (femoral osteotomy) and could, therefore, serve as a potent alternative to the application of Tramadol via the drinking water. Both protocols were examined for analgesic effectiveness, side effects on experimental readout, and effects on fracture healing outcomes in male and female C57BL/6N mice. The BUP-Depot provided effective analgesia for 72 h, comparable to the effectiveness of Tramadol in the drinking water. Fracture healing outcome was not different between analgesic regimes. The availability of a Buprenorphine depot formulation for rodents in Europe would be a beneficial addition for extended pain relief in mice, thereby increasing animal welfare.

Dietary phosphate restriction prevents the appearance of sarcopenia signs in old mice

BACKGROUND

Sarcopenia is defined by the progressive and generalized loss of muscle mass and function associated with aging. We have previously proposed that aging-related hyperphosphataemia is linked with the appearance of sarcopenia signs. Because there are not effective treatments to prevent sarcopenia, except for resistance exercise, we propose here to analyse whether the dietary restriction of phosphate could be a useful strategy to improve muscle function and structure in an animal model of aging.

METHODS

Five-month-old (young), 24-month-old (old) and 28-month-old (geriatric) male C57BL6 mice were used. Old and geriatric mice were divided into two groups, one fed with a standard diet (0.6% phosphate) and the other fed with a low-phosphate (low-P) diet (0.2% phosphate) for 3 or 7 months, respectively. A phosphate binder, Velphoro®, was also supplemented in a group of old mice, mixed with a standard milled diet for 3 months. Muscle mass was measured by the weight of gastrocnemius and tibial muscles, and quality by nuclear magnetic resonance imaging (NMRI) and histological staining assays. Muscle strength was measured by grip test and contractile properties of the tibialis muscle by electrical stimulation of the common peroneal nerve. Gait parameters were analysed during the spontaneous locomotion of the mice with footprinting. Orientation and motor coordination were evaluated using a static rod test.

RESULTS

Old mice fed with low-P diet showed reduced serum phosphate concentration (16.46 ± 0.77 mg/dL young; 21.24 ± 0.95 mg/dL old; 17.46 ± 0.82 mg/dL low-P diet). Old mice fed with low-P diet displayed 44% more mass in gastrocnemius muscles with respect to old mice (P = 0.004). NMRI revealed a significant reduction in T2 relaxation time (P = 0.014) and increased magnetization transfer (P = 0.045) and mean diffusivity (P = 0.045) in low-P diet-treated mice compared with their coetaneous. The hypophosphataemic diet increased the fibre size and reduced the fibrotic area by 52% in gastrocnemius muscle with respect to old mice (P = 0.002). Twitch force and tetanic force were significantly increased in old mice fed with the hypophosphataemic diet (P = 0.004 and P = 0.014, respectively). Physical performance was also improved, increasing gait speed by 30% (P = 0.032) and reducing transition time in the static rod by 55% (P = 0.012). Similar results were found when diet was supplemented with Velphoro®.

CONCLUSIONS

The dietary restriction of phosphate in old mice improves muscle quantity and quality, muscle strength and physical performance. Similar results were found using the phosphate binder Velphoro®, supporting the role of phosphate in the impairment of muscle structure and function that occurs during aging.

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.

Water-Reaching Platform for Longitudinal Assessment of Cortical Activity and Fine Motor Coordination Defects in a Huntington Disease Mouse Model

Huntington disease (HD), caused by dominantly inherited expansions of a CAG repeat results in characteristic motor dysfunction. Although gross motor defects have been extensively characterized in multiple HD mouse models using tasks such as rotarod and beam walking, less is known about forelimb deficits. We develop a high-throughput alternating reward/nonreward water-reaching task and training protocol conducted daily over approximately two months to simultaneously monitor forelimb impairment and mesoscale cortical changes in GCaMP activity, comparing female zQ175 (HD) and wild-type (WT) littermate mice, starting at ∼5.5 months. Behavioral analysis of the water-reaching task reveals that HD mice, despite learning the water-reaching task as proficiently as wild-type mice, take longer to learn the alternating event sequence as evident by impulsive (noncued) reaches and initially display reduced cortical activity associated with successful reaches. At this age gross motor defects determined by tapered beam assessment were not apparent. Although wild-type mice displayed no significant changes in cortical activity and reaching trajectory throughout the testing period, HD mice exhibited an increase in cortical activity, especially in the secondary motor and retrosplenial cortices, over time, as well as longer and more variable reaching trajectories by approximately seven months. HD mice also experienced a progressive reduction in successful performance. Tapered beam and rotarod tests as well as reduced DARPP-32 expression (striatal medium spiny neuron marker) after water-reaching assessment confirmed HD pathology. The water-reaching task can be used to inform on a daily basis, HD and other movement disorder onset and manifestation, therapeutic intervention windows, and test drug efficacy.

Neurological scoring and gait kinematics to assess functional outcome in an ovine model of ischaemic stroke

Background

Assessment of functional impairment following ischaemic stroke is essential to determine outcome and efficacy of intervention in both clinical patients and pre-clinical models. Although paradigms are well described for rodents, comparable methods for large animals, such as sheep, remain limited. This study aimed to develop methods to assess function in an ovine model of ischaemic stroke using composite neurological scoring and gait kinematics from motion capture.

Methods

Merino sheep (n = 26) were anaesthetised and subjected to 2 hours middle cerebral artery occlusion. Animals underwent functional assessment at baseline (8-, 5-, and 1-day pre-stroke), and 3 days post-stroke. Neurological scoring was carried out to determine changes in neurological status. Ten infrared cameras measured the trajectories of 42 retro-reflective markers for calculation of gait kinematics. Magnetic resonance imaging (MRI) was performed at 3 days post-stroke to determine infarct volume. Intraclass Correlation Coefficients (ICC's) were used to assess the repeatability of neurological scoring and gait kinematics across baseline trials. The average of all baselines was used to compare changes in neurological scoring and kinematics at 3 days post-stroke. A principal component analysis (PCA) was performed to determine the relationship between neurological score, gait kinematics, and infarct volume post-stroke.

Results

Neurological scoring was moderately repeatable across baseline trials (ICC > 0.50) and detected marked impairment post-stroke (p < 0.05). Baseline gait measures showed moderate to good repeatability for the majority of assessed variables (ICC > 0.50). Following stroke, kinematic measures indicative of stroke deficit were detected including an increase in stance and stride duration (p < 0.05). MRI demonstrated infarction involving the cortex and/or thalamus (median 2.7 cm³, IQR 1.4 to 11.9). PCA produced two components, although association between variables was inconclusive.

Conclusion

This study developed repeatable methods to assess function in sheep using composite scoring and gait kinematics, allowing for the evaluation of deficit 3 days post-stroke. Despite utility of each method independently, there was poor association observed between gait kinematics, composite scoring, and infarct volume on PCA. This suggests that each of these measures has discreet utility for the assessment of stroke deficit, and that multimodal approaches are necessary to comprehensively characterise functional impairment.

Clicker Training Mice for Improved Compliance in the Catwalk Test

The CatWalk test relies on the run of mice across the platform to measure a constant speed with low variation. Mice usually require a stimulus to walk to the end of the catwalk. However, such stimuli are usually aversive and can impair welfare. Positive reinforcement training of laboratory animals is a thriving tool for refinement and contributes to meeting the demands instituted by Directive 2010/63/EU. We have already demonstrated the positive effects of clicker training. In this study, we trained male and female mice to complete the CatWalk protocol while assessing the effects of training on their well-being (Open Filed and Elevated Plus Maze). In the CatWalk test, we observed that clicker training improved the running speed of the mice. In addition, clicker training reduced the number of runs required by mice, which was more pronounced in males. Clicker training lowered anxiety-like behaviors in our mice, especially in females, where a significant difference was observed between trained and untrained ones. Based on our findings, we hypothesize that clicker training is an effective tool to motivate mice and increase performance on the CatWalk test without potentially impairing their welfare (e.g., by puffing them).

The role of V3 neurons in speed-dependent interlimb coordination during locomotion in mice

Speed-dependent interlimb coordination allows animals to maintain stable locomotion under different circumstances. The V3 neurons are known to be involved in interlimb coordination. We previously modeled the locomotor spinal circuitry controlling interlimb coordination (Danner et al., 2017). This model included the local V3 neurons that mediate mutual excitation between left and right rhythm generators (RGs). Here, our focus was on V3 neurons involved in ascending long propriospinal interactions (aLPNs). Using retrograde tracing, we revealed a subpopulation of lumbar V3 aLPNs with contralateral cervical projections. V3OFF mice, in which all V3 neurons were silenced, had a significantly reduced maximal locomotor speed, were unable to move using stable trot, gallop, or bound, and predominantly used a lateral-sequence walk. To reproduce this data and understand the functional roles of V3 aLPNs, we extended our previous model by incorporating diagonal V3 aLPNs mediating inputs from each lumbar RG to the contralateral cervical RG. The extended model reproduces our experimental results and suggests that locally projecting V3 neurons, mediating left-right interactions within lumbar and cervical cords, promote left-right synchronization necessary for gallop and bound, whereas the V3 aLPNs promote synchronization between diagonal fore and hind RGs necessary for trot. The model proposes the organization of spinal circuits available for future experimental testing.

Fatty acid-binding protein 4 (FABP4) inhibition promotes locomotor and autonomic recovery in rats following spinal cord injury

The inflammatory response associated with traumatic spinal cord injury (SCI) contributes to locomotor and sensory impairments. Pro-inflammatory (M1) macrophages/microglia (MφMG) are the major cellular players in this response as they promote chronic inflammation resulting in injury expansion and tissue damage. Fatty Acid-Binding Protein 4 (FABP4) promotes M1 MφMG differentiation; however, it is unknown if FABP4 also plays a role in the etiology of SCI. The present study investigates whether FABP4's gene expression influences functional recovery following SCI. Analysis of qPCR data shows a robust induction of FABP4 mRNA (>100 fold) in rats subjected to a T9-T10 contusion injury compared to control. Western blot experiments reveal significant upregulation of FABP4 protein at the injury epicenter, and immunofluorescence analysis identifies this upregulation occurs in CD11b+ MφMG. Furthermore, upregulation of FABP4 gene expression correlates with PPARγ downregulation, inactivation of Iκβα, and the activation of the NF-κB pathway. Analysis of locomotor recovery using the Basso-Beattie-Bresnahan's (BBB) locomotor scale and the CatWalk gait analysis system shows that injured rats treated with FABP4 inhibitor BMS309403 have significant improvements in locomotion compared to vehicle controls. Additionally, inhibitor-treated rats exhibit enhanced autonomic bladder reflex recovery. Immunofluorescence experiments also show the administration of the FABP4 inhibitor increases the number of CD163+ and Liver Arginase+ M2 MφMG within the epicenter and penumbra of the injured spinal cord 28 dpi. These findings show that FABP4 may significantly exacerbate locomotor and sensory impairments during SCI by modulating macrophage/microglial activity.

Stride-level analysis of mouse open field behavior using deep-learning-based pose estimation

Gait and posture are often perturbed in many neurological, neuromuscular, and neuropsychiatric conditions. Rodents provide a tractable model for elucidating disease mechanisms and interventions. Here, we develop a neural-network-based assay that adopts the commonly used open field apparatus for mouse gait and posture analysis. We quantitate both with high precision across 62 strains of mice. We characterize four mutants with known gait deficits and demonstrate that multiple autism spectrum disorder (ASD) models show gait and posture deficits, implying this is a general feature of ASD. Mouse gait and posture measures are highly heritable and fall into three distinct classes. We conduct a genome-wide association study to define the genetic architecture of stride-level mouse movement in the open field. We provide a method for gait and posture extraction from the open field and one of the largest laboratory mouse gait and posture data resources for the research community.

Sheppard et al. present a method for gait and posture analysis in the common open field apparatus using neural-network-based pose estimation. They apply this high-throughput method to dissect the genetic architecture of mouse movement.

The use of a detailed video-based locomotor pattern analysis system to assess the functional reinnervation of denervated hind limb muscles

BACKGROUND

Spinal cord injuries induce a critical loss of motoneurons followed by irreversible locomotor function impairment. Surgical approaches combined with neuroprotective agents effectively rescue the damaged motoneurons and improve locomotor function. Our aim was to develop a reliable method which is able to provide quantifiable and in-depth data on the locomotor recovery during skeletal muscle reinnervation.

NEW METHOD

Sprague-Dawley rats underwent lumbar 4 ventral root avulsion and reimplantation followed by riluzole treatment in order to rescue the injured motoneurons of the damaged pool. Control animals were operated, but received no riluzole treatment. The locomotor pattern of the hind limb was recorded biweekly on a special runway equipped with high resolution and high speed digital cameras producing both lateral and rear views simultaneously. All together 12 parameters of the hind limb movement pattern were evaluated by measuring specific joint angles, footprints and gait parameters in single video frames. Four months after the operation Fast Blue, a fluorescent retrograde tracer was applied to the L4 spinal nerve in order to label the reinnervating motoneurons.

RESULTS

Our results confirmed the sensitivity of our arrangement and established strong relationship between the functional improvement and the morphological reinnervation. Moreover, we developed a correction method to make the system tolerant to the differences in the weight, step duration and step length.

COMPARISON WITH EXISTING METHODS

There are no commercially available cheap, multi-parametric analysing equipment to characterise the gait in its complexity.

CONCLUSIONS

Our system offers a modular, adaptable and expandable analysis on the reinnervation of the limb musculature in rodents.

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.

Markerless analysis of hindlimb kinematics in spinal cord-injured mice through deep learning

Rodent models are commonly used to understand the underlying mechanisms of spinal cord injury (SCI). Kinematic analysis, an important technique to measure dysfunction of locomotion after SCI, is generally based on the capture of physical markers placed on bony landmarks. However, marker-based studies face significant experimental hurdles such as labor-intensive manual joint tracking, alteration of natural gait by markers, and skin error from soft tissue movement on the knee joint. Although the pose estimation strategy using deep neural networks can solve some of these issues, it remains unclear whether this method is adaptive to SCI mice with abnormal gait. In the present study, we developed a deep learning based markerless method of 2D kinematic analysis to automatically track joint positions. We found that a relatively small number (< 200) of manually labeled video frames was sufficient to train the network to extract trajectories. The mean test error was on average 3.43 pixels in intact mice and 3.95 pixels in SCI mice, which is comparable to the manual tracking error (3.15 pixels, less than 1 mm). Thereafter, we extracted 30 gait kinematic parameters and found that certain parameters such as step height and maximal hip joint amplitude distinguished intact and SCI locomotion.

IgM Immunoglobulin Influences Recovery after Cervical Spinal Cord Injury by Modulating the IgG Autoantibody Response

Spinal cord injury (SCI) results in the development of detrimental autoantibodies against the lesioned spinal cord. IgM immunoglobulin maintains homeostasis against IgG-autoantibody responses, but its effect on SCI recovery remains unknown. In the present study we investigated the role of IgM immunoglobulin in influencing recovery after SCI. To this end, we induced cervical SCI at the C6/C7 level in mice that lacked secreted IgM immunoglobulin [IgM-knock-out (KO)] and their wild-type (WT) littermate controls. Overall, the absence of secretory IgM resulted in worse outcomes as compared with WT mice with SCI. At two weeks after injury, IgM-KO mice had significantly more IgG antibodies, which fixed the complement system, in the injured spinal cord parenchyma. In addition to these findings, IgM-KO mice had more parenchymal T-lymphocytes as well as CD11b+ microglia/macrophages, which co-localized with myelin. At 10 weeks after injury, IgM-KO mice showed significant impairment in neurobehavioral recovery, such as deteriorated coordination, reduced hindlimb swing speed and print area. These neurobehavioral detriments were coupled with increased lesional tissue and myelin loss. Taken together, this study provides the first evidence for the importance of IgM immunoglobulin in modulating recovery after SCI and suggests that modulating IgM could be a novel therapeutic approach to enhance recovery after SCI.

Theta-gamma coupling during REM sleep depends on breathing rate

Temporal coupling between theta and gamma oscillations is a hallmark activity pattern of several cortical networks and becomes especially prominent during REM sleep. In a parallel approach, nasal breathing has been recently shown to generate phase-entrained network oscillations which also modulate gamma. Both slow rhythms (theta and respiration-entrained oscillations) have been suggested to aid large-scale integration but they differ in frequency, display low coherence, and modulate different gamma sub-bands. Respiration and theta are therefore believed to be largely independent. In the present work, however, we report an unexpected but robust relation between theta-gamma coupling and respiration in mice. Interestingly, this relation takes place not through the phase of individual respiration cycles, but through respiration rate: the strength of theta-gamma coupling exhibits an inverted V-shaped dependence on breathing rate, leading to maximal coupling at breathing frequencies of 4-6 Hz. Noteworthy, when subdividing sleep epochs into phasic and tonic REM patterns, we find that breathing differentially relates to theta-gamma coupling in each state, providing new evidence for their physiological distinctiveness. Altogether, our results reveal that breathing correlates with brain activity not only through phase-entrainment but also through rate-dependent relations with theta-gamma coupling. Thus, the link between respiration and other patterns of cortical network activity is more complex than previously assumed.

Common and distinct muscle synergies during level and slope locomotion in the cat

Although it is well established that the motor control system is modular, the organization of muscle synergies during locomotion and their change with ground slope are not completely understood. For example, typical reciprocal flexor-extensor muscle synergies of level walking in cats break down in downslope: one-joint hip extensors are silent throughout the stride cycle, whereas hindlimb flexors demonstrate an additional stance phase-related electromyogram (EMG) burst (Smith JL, Carlson-Kuhta P, Trank TV. J Neurophysiol 79: 1702-1716, 1998). Here, we investigated muscle synergies during level, upslope (27°), and downslope (-27°) walking in adult cats to examine common and distinct features of modular organization of locomotor EMG activity. Cluster analysis of EMG burst onset-offset times of 12 hindlimb muscles revealed five flexor and extensor burst groups that were generally shared across slopes. Stance-related bursts of flexor muscles in downslope were placed in a burst group from level and upslope walking formed by the rectus femoris. Walking upslope changed swing/stance phase durations of level walking but not the cycle duration. Five muscle synergies computed using non-negative matrix factorization accounted for at least 95% of variance in EMG patterns in each slope. Five synergies were shared between level and upslope walking, whereas only three of those were shared with downslope synergies; these synergies were active during the swing phase and phase transitions. Two stance-related synergies of downslope walking were distinct; they comprised a mixture of flexors and extensors. We suggest that the modular organization of muscle activity during level and slope walking results from interactions between motion-related sensory feedback, CPG, and supraspinal inputs.NEW & NOTEWORTHY We demonstrated that the atypical EMG activities during cat downslope walking, silent one-joint hip extensors and stance-related EMG bursts in flexors, have many features shared with activities of level and upslope walking. Majority of EMG burst groups and muscle synergies were shared among these slopes, and upslope modulated the swing/stance phase duration but not cycle duration. Thus, synergistic EMG activities in all slopes might result from a shared CPG receiving somatosensory and supraspinal inputs.

Therapeutic targeting of Lyn kinase to treat chorea-acanthocytosis

Chorea-Acanthocytosis (ChAc) is a devastating, little understood, and currently untreatable neurodegenerative disease caused by VPS13A mutations. Based on our recent demonstration that accumulation of activated Lyn tyrosine kinase is a key pathophysiological event in human ChAc cells, we took advantage of Vps13a^−/− mice, which phenocopied human ChAc. Using proteomic approach, we found accumulation of active Lyn, γ-synuclein and phospho-tau proteins in Vps13a^−/− basal ganglia secondary to impaired autophagy leading to neuroinflammation. Mice double knockout Vps13a^−/− Lyn^−/− showed normalization of red cell morphology and improvement of autophagy in basal ganglia. We then in vivo tested pharmacologic inhibitors of Lyn: dasatinib and nilotinib. Dasatinib failed to cross the mouse brain blood barrier (BBB), but the more specific Lyn kinase inhibitor nilotinib, crosses the BBB. Nilotinib ameliorates both Vps13a^−/− hematological and neurological phenotypes, improving autophagy and preventing neuroinflammation. Our data support the proposal to repurpose nilotinib as new therapeutic option for ChAc patients.

Intensive longitudinal characterization of multidimensional biobehavioral dynamics in laboratory rats

Rats have been used as animal models for human diseases for more than a century, yet a systematic understanding of basal biobehavioral phenotypes of laboratory rats is still missing. In this study, we utilize wireless tracking technology and videography, collect and analyze more than 130 billion data points to fill this gap, and characterize the evolution of behavior and physiology of group-housed male and female rats (n = 114) of the most commonly used strains (Lister Hooded, Long-Evans, Sprague-Dawley, and Wistar) throughout their development. The resulting intensive longitudinal data suggest the existence of strain and sex differences and bi-stable developmental states. Under standard laboratory 12-h light/12-h dark conditions, our study found the presence of multiple oscillations such as circatidal-like rhythms in locomotor activity. The overall findings further suggest that frequent movement along cage walls or thigmotaxic activity may be a physical feature of motion in constrained spaces, critically affecting the interpretation of basal behavior of rats in cages.

A bioisostere of Dimebon/Latrepirdine delays the onset and slows the progression of pathology in FUS transgenic mice

Aims

To assess effects of DF402, a bioisostere of Dimebon/Latrepirdine, on the disease progression in the transgenic model of amyotrophic lateral sclerosis (ALS) caused by expression of pathogenic truncated form of human FUS protein.

Methods

Mice received DF402 from the age of 42 days and the onset of clinical signs, the disease duration and animal lifespan were monitored for experimental and control animals, and multiple parameters of their gait were assessed throughout the pre‐symptomatic stage using CatWalk system followed by a bioinformatic analysis. RNA‐seq was used to compare the spinal cord transcriptomes of wild‐type, untreated, and DF402‐treated FUS transgenic mice.

Results

DF402 delays the onset and slows the progression of pathology. We developed a CatWalk analysis protocol that allows detection of gait changes in FUS transgenic mice and the effect of DF402 on their gait already at early pre‐symptomatic stage. At this stage, a limited number of genes significantly change expression in transgenic mice and for 60% of these genes, DF402 treatment causes the reversion of the expression pattern.

Conclusion

DF402 slows down the disease progression in the mouse model of ALS, which is consistent with previously reported neuroprotective properties of Dimebon and its other bioisosteres. These results suggest that these structures can be considered as lead compounds for further optimization to obtain novel medicines that might be used as components of complex ALS therapy.

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.

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.

Frizzled 1 and Wnt1 as new potential therapeutic targets in the traumatically injured spinal cord

Despite the experimental evidence pointing to a significant role of the Wnt family of proteins in physiological and pathological rodent spinal cord functioning, its potential relevance in the healthy and traumatically injured human spinal cord as well as its therapeutic potential in spinal cord injury (SCI) are still poorly understood. To get further insight into these interesting issues, we first demonstrated by quantitative Real-Time PCR and simple immunohistochemistry that detectable mRNA expression of most Wnt components, as well as protein expression of all known Wnt receptors, can be found in the healthy human spinal cord, supporting its potential involvement in human spinal cord physiology. Moreover, evaluation of Frizzled (Fz) 1 expression by double immunohistochemistry showed that its spatio-temporal and cellular expression pattern in the traumatically injured human spinal cord is equivalent to that observed in a clinically relevant model of rat SCI and suggests its potential involvement in SCI progression/outcome. Accordingly, we found that long-term lentiviral-mediated overexpression of the Fz1 ligand Wnt1 after rat SCI improves motor functional recovery, increases myelin preservation and neuronal survival, and reduces early astroglial reactivity and NG2+ cell accumulation, highlighting the therapeutic potential of Wnt1 in this neuropathological situation.

An Analysis of Variability in "CatWalk" Locomotor Measurements to Aid Experimental Design and Interpretation

Preclinical studies in models of neurologic injury and disease rely on behavioral outcomes to measure intervention efficacy. For spinal cord injury, the CatWalk system provides unbiased quantitative assessment of subtle aspects of locomotor function in rodents and so can powerfully detect significant differences between experimental and control groups. Although clearly of key importance, summary group-level data can obscure the variability within and between individual subjects and therefore make it difficult to understand the magnitude of effect in individual animals and the proportion of a group that may show benefit. Here, we calculate reference change intervals (RCIs) that define boundaries of normal variability for measures of rat locomotion on the CatWalk. Our results indicate that many commonly-used outcome measures are highly variable, such that differences of up to 70% from baseline value must be considered normal variation. Many CatWalk outcome variables are also highly correlated and dependent on run speed. Application of calculated RCIs to open access data (https://scicrunch.org/odc-sci) on hindlimb stride length in spinal cord-injured rats illustrates the complementarity between group-level (16 mm change; p = 0.0009) and individual-level (5/32 animals show change outside RCI boundaries) analysis between week 3 and week 6 after injury. We also conclude that interdependence among CatWalk variables implies that test “batteries” require careful composition to ensure that different aspects of defective gait are analyzed. Calculation of RCIs aids in experimental design by quantifying variability and enriches overall data analysis by providing details of change at an individual level that complement group-level analysis.

Factors affecting the reliability of behavioral assessments for rodent osteoarthritis models

The translational value of osteoarthritis (OA) models is often debated because numerous studies have shown that animal models frequently fail to predict the efficacy of therapies in humans. In part, this failing may be due to the paucity of preclinical studies that include behavioral assessments in their metrics. Behavioral assessments of animal OA models can provide valuable data on the pain and disability associated with disease-sequelae of significant clinical relevance. Clinical definitions of efficacy for OA therapeutics often center on their palliative effects. Thus, the widespread inclusion of behaviors indicative of pain and disability in preclinical animal studies may contribute to greater success identifying clinically relevant interventions. Unfortunately, studies that include behavioral assays still frequently encounter pitfalls in assay selection, protocol consistency, and data/methods transparency. Targeted selection of behavioral assays, with consideration of the array of clinical OA phenotypes and the limitations of individual behavioral assays, is necessary to identify clinically relevant outcomes in OA animal models appropriately. Furthermore, to facilitate accurate comparisons across research groups and studies, it is necessary to improve the transparency of methods. Finally, establishing agreed-upon and clear definitions of behavioral data will reduce the convolution of data both within and between studies. Improvement in these areas is critical to the continued benefit of preclinical animal studies as translationally relevant data in OA research. As such, this review highlights the current state of behavioral analyses in preclinical OA models.

Shared and specific signatures of locomotor ataxia in mutant mice

Several spontaneous mouse mutants with deficits in motor coordination and associated cerebellar neuropathology have been described. Intriguingly, both visible gait alterations and neuroanatomical abnormalities throughout the brain differ across mutants. We previously used the LocoMouse system to quantify specific deficits in locomotor coordination in mildly ataxic Purkinje cell degeneration mice (pcd; Machado et al., 2015). Here, we analyze the locomotor behavior of severely ataxic reeler mutants and compare and contrast it with that of pcd. Despite clearly visible gait differences, direct comparison of locomotor kinematics and linear discriminant analysis reveal a surprisingly similar pattern of impairments in multijoint, interlimb, and whole-body coordination in the two mutants. These findings capture both shared and specific signatures of gait ataxia and provide a quantitative foundation for mapping specific locomotor impairments onto distinct neuropathologies in mice.

A Novel Multi-Dimensional Analysis of Rodent Gait Reveals the Compensation Strategies Used during Spontaneous Recovery from Spinal Cord and Traumatic Brain Injury

As rodent locomotion becomes a more popular behavioral assay, proper rodent gait analysis becomes more and more important. Gait measures, such as stride length, cycle time, and duty factor, are not independent of one another, making statistical comparisons between groups a tricky endeavor. Instead of identifying the mathematical relationships between a group of locomotor measures, we simply tracked the steps of rodents in x,y,t space. By plotting with respect to the reference limb, we are able to quantify locomotor changes in space, time, and coordination simultaneously. With our technique, we show that the overall locomotion of 77 rats 1 week after a C4/5 right overhemisection injury was significantly different than pre-injury. This difference was maintained in untreated animals for the entire 7 weeks of the study, but how this difference arose changed. Initially, the right forelimb exhibited very abnormal stepping, but eventually reduced its difference from pre-injury levels. Conversely, the left forelimb was initially mildly different from pre-injury, but further deviated from normal stepping as the weeks went on. Our new gait analysis technique helps to show the trade-off between the restoration of function and the spontaneous development of compensatory techniques. When we applied this new analysis technique to 13 mice after a severe controlled cortical impact, we found that their locomotion was no different from 12 sham mice for the entire 4 weeks of the study. We believe that this gait analysis method succinctly addresses the confound of interdependency of gait measures and does so across multiple injury models.

Silhouette-Length-Scaled Gait Parameters for Motor Functional Analysis in Mice and Rats

Gait analysis of transgenic mice and rats modeling human diseases often suffers from the condition that those models exhibit genotype-driven differences in body size, weight, and length. Thus, we hypothesized that scaling by the silhouette length improves the reliability of gait analysis allowing normalization for individual body size differences. Here, we computed video-derived silhouette length and area parameters from a standard markerless gait analysis system using image-processing techniques. By using length- and area-derived data along with body weight and age, we systematically scaled individual gait parameters. We compared these different scaling approaches and report here that normalization for silhouette length improves the validity and reliability of gait analysis in general. The application of this silhouette length scaling to transgenic Huntington disease mice and Parkinson´s disease rats identifies the remaining differences reflecting more reliable, body length-independent motor functional differences. Overall, this emphasizes the need for silhouette-length-based intra-assay scaling as an improved standard approach in rodent gait analysis.

Description and validation of the LocoWhisk system: Quantifying rodent exploratory, sensory and motor behaviours

BACKGROUND

Previous studies have demonstrated that analysing whisker movements and locomotion allows us to quantify the behavioural consequences of sensory, motor and cognitive deficits in rodents. Independent whisker and feet trackers exist but there is no fully-automated, open-source software and hardware solution, that measures both whisker movements and gait.

NEW METHOD

We present the LocoWhisk arena and new accompanying software (ARTv2) that allows the automatic detection and measurement of both whisker and gait information from high-speed video footage.

RESULTS

We demonstrate the new whisker and foot detector algorithms on high-speed video footage of freely moving small mammals, and show that whisker movement and gait measurements collected in the LocoWhisk arena are similar to previously reported values in the literature.

COMPARISON WITH EXISTING METHOD(S)

We demonstrate that the whisker and foot detector algorithms, are comparable in accuracy, and in some cases significantly better, than readily available software and manual trackers.

CONCLUSION

The LocoWhisk system enables the collection of quantitative data from whisker movements and locomotion in freely behaving rodents. The software automatically records both whisker and gait information and provides added statistical tools to analyse the data. We hope the LocoWhisk system and software will serve as a solid foundation from which to support future research in whisker and gait analysis.

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.

Characterization of neuromas in peripheral nerves and their effects on heterotopic bone formation

The formation of neuromas involves expansion of the cellular components of peripheral nerves. The onset of these disorganized tumors involves activation of sensory nerves and neuroinflammation. Particularly problematic in neuroma is arborization of axons leading to extreme, neuropathic pain. The most common sites for neuroma are the ends of transected nerves following injury; however, this rodent model does not reliably result in neuroma formation. In this study, we established a rodent model of neuroma in which the sciatic nerve was loosely ligated with two chromic gut sutures. This model formed neuromas reliably (∼95%), presumably through activation of the neural inflammatory cascade. Resulting neuromas had a disorganized structure and a significant number of replicating cells. Quantification of changes in perineurial and Schwann cells showed a significant increase in these populations. Immunohistochemical analysis showed the presence of β-tubulin 3 in the rapidly expanding nerve and a decrease in neurofilament heavy chain compared to the normal nerve, suggesting the axons forming a disorganized structure. Measurement of the permeability of the blood-nerve barrier shows that it opened almost immediately and remained open as long as 10 days. Studies using an antagonist of the β3-adrenergic receptor (L-748,337) or cromolyn showed a significant reduction in tumor size and cell expansion as determined by flow cytometry, with an improvement in the animal's gait detected using a Catwalk system. Previous studies in our laboratory have shown that heterotopic ossification is also a result of the activation of neuroinflammation. Since heterotopic ossification and neuroma often occur together in amputees, they were induced in the same limbs of the study animals. More heterotopic bone was formed in animals with neuromas as compared to those without. These data collectively suggest that perturbation of early neuroinflammation with compounds such as L-748,337 and cromolyn may reduce formation of neuromas.

Endogenous Interleukin-10 Deficiency Exacerbates Vascular Pathology in Traumatic Cervical Spinal Cord Injury

Although the majority of traumatic spinal cord injuries (SCIs) take place at the cervical level, pre-clinical studies have been disproportionally focused on thoracic insults. With differences in anatomy, physiology, and immune response between spinal cord levels, there is evidence that injury pathophysiology may vary, requiring tailored treatment paradigms. Further, as only a few therapies have been successfully translated to the clinic, cervical models are increasingly recognized as essential for the characterization of trauma and therapy. Using a novel and clinically relevant cervical contusion-compression mouse model of bilateral incomplete injury, this study aimed to assess the role of interleukin10 (IL-10), a potent cytokine with broad anti-inflammatory effects, in SCI vascular pathology. While the effects of IL-10 loss have been previously evaluated, the vascular changes are poorly characterized. Here, using in vivo high-resolution ultrasound imaging, we demonstrate that IL-10 deficiency is associated with increased acute vascular damage. Importantly, the loss of endogenous IL-10 led to significant differences in the acute systemic response to SCI, specifically the circulating levels of IL-12 (p70), LIX (CXCL5), IL-1β, tumor necrosis factor (TNF)-α, and IL-6 relative to genotype sham controls. These effects also fostered modest impairments in long-term functional recovery, assessed by the Basso Mouse Scale, as well as histological outcomes.

Conditional knockout of UBC13 produces disturbances in gait and spontaneous locomotion and exploration in mice

Here we have characterized the functional impairments resulting from conditional knockout of the ubiquitin-conjugating E2 enzyme (UBC13) in rodent cerebellar granule neurons, which greatly increases the parallel fiber presynaptic boutons and functional parallel fiber/Purkinje cell synapses. We report that conditional UBC13 knockout mice exhibit reliable deficits on several gait-related variables when their velocity of ambulation is tightly controlled by a moving treadmill and by restricting space for movement. Selected gait parameters and movement patterns related to spontaneous exploration in an open field may also be affected in conditional UBC13 knockout mice. Analysis of open-field data as a function of test session half using force-plate actometer instrumentation suggest that conditional UBC13 knockout mice have alterations in emotionality, possibly affecting gait and movement variables. These findings suggest that conditional UBC13 knockout mice represent a valuable platform for assessing the effects of disturbances in cerebellar granule cell circuitry on gait and other aspects of locomotion. Also, the possibility that psychological factors such as altered emotionality may impact gait and movement patterns in these mice suggest that these mice may provide a useful model for evaluating analogous behavioral impairments in autism spectrum disorders and other neurodevelopmental syndromes associated with deregulation of ubiquitin signaling.

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.

Modeling hind-limb kinematics using a bio-inspired algorithm with a local search

BACKGROUND

Laboratory rats play a critical role in research because they provide a biological model that can be used for evaluating the affectation of diseases and injuries, and for the evaluation of the effectiveness of new drugs and treatments. The analysis of locomotion in laboratory rats facilitates the understanding of motor defects in many diseases, as well as the damage and recovery after peripheral and central nervous system injuries. However, locomotion analysis of rats remains a great challenge due to the necessity of labor intensive manual annotations of video data required to obtain quantitative measurements of the kinematics of the rodent extremities. In this work, we present a method that is based on the use of a bio-inspired algorithm that fits a kinematic model of the hind limbs of rats to binary images corresponding to the segmented marker of images corresponding to the rat's gait. The bio-inspired algorithm combines a genetic algorithm for a group of the optimization variables with a local search for a second group of the optimization variables.

RESULTS

Our results indicate the feasibility of employing the proposed approach for the automatic annotation and analysis of the locomotion patterns of the posterior extremities of laboratory rats.

CONCLUSIONS

The adjustment of the hind limb kinematic model to markers of the video frames corresponding to rat's gait sequences could then be used to analyze the motion patterns during the steps, which, in turn, can be useful for performing quantitative evaluations of the effect of lesions and treatments on rats models.

Effect of Ginkgo biloba extract-761 on motor functions in permanent middle cerebral artery occlusion rats

BACKGROUND

Ginkgo biloba extract (EGb-761) has been in use to treat variety of ailments including memory loss and emotional disorders usually experienced after ischemic stroke. However, data regarding its protective role in stroke associated motor dysfunction is scarce.

PURPOSE

The present work was designed to investigate the long-term effects of EGb-761 on the motor dysfunctions associated with permanent middle cerebral artery occlusion (pMCAO) in rats.

STUDY DESIGN/METHODS

Focal ischemic stroke was induced in male Sprague-Dawley rats by pMCAO. These rats were orally administered with EGb-761 (25, 50, 100 mg/kg) and positive control butylphthalide (50 mg/kg) for up to 28 consecutive days. The motor function was evaluated by assessing neurological scores, rotarod performance and gait analysis after 7, 14, 21 and 28 days. After 28 days, the histological examination of in frontal cortex and hippocampus was also carried out.

RESULTS

EGb-761 treatment significantly improved motor function with better outcome in coordination and gait impairment rats. EGb-761 (25, 50, 100 mg/kg) treatment for 28 days significantly decreased the neurological scores. After 28 days of treatment EGb-761 (50 and 100 mg/kg) significantly increased the latency in rotarod test, walk speed, and the body rotation, whereas, decreased the stride time and the left posterior swing length in gait were observed. EGb-761 (50, 100 mg/kg). EGb-761 (50, 100 mg/kg) significantly improved the pathological changes related to pMCAO.

CONCLUSIONS

EGb 761 could improve motor function especially gait impairments among pMCAO rat model related to the decreased neuronal damage. Therefore, it might be the potential to be explored further as an effective therapeutic drug to treat post stroke motor dysfunctions.

Gait Analyses in Mice: Effects of Age and Glutathione Deficiency

Minor changes (~0.1 m/s) in human gait speed are predictive of various measures of decline and can be used to identify at-risk individuals prior to further decline. These associations are possible due to an abundance of human clinical research. However, age-related gait changes are not well defined in rodents, even though rodents are used as the primary pre-clinical model for many disease states as well as aging research. Our study investigated the usefulness of a novel automated system, the CatWalk™ XT, to measure age-related differences in gait. Furthermore, age-related functional declines have been associated with decreases in the reduced to oxidized glutathione ratio leading to a pro-oxidizing cellular shift. Therefore the secondary aim of this study was to determine whether chronic glutathione deficiency led to exacerbated age-associated impairments. Groups of male and female wild-type (gclm^+/+) and knock-out (gclm^-/-) mice aged 4, 10 and 17 months were tested on the CatWalk and gait measurements recorded. Similar age-related declines in all measures of gait were observed in both males and females, and chronic glutathione depletion was associated with some delays in age-related declines, which were further exacerbated. In conclusion, the CatWalk is a useful tool to assess gait changes with age, and further studies will be required to identify the potential compensating mechanisms underlying the effects observed with the chronic glutathione depletion.

Impaired Motor Coordination and Learning in Mice Lacking Anoctamin 2 Calcium-Gated Chloride Channels

Neurons communicate through excitatory and inhibitory synapses. Both lines of communication are adjustable and allow the fine tuning of signal exchange required for learning processes in neural networks. Several distinct modes of plasticity modulate glutamatergic and GABAergic synapses in Purkinje cells of the cerebellar cortex to promote motor control and learning. In the present paper, we present evidence for a role of short-term ionic plasticity in the cerebellar circuit activity. This type of plasticity results from altered chloride driving forces at the synapses that molecular layer interneurons form on Purkinje cell dendrites. Previous studies have provided evidence for transiently diminished chloride gradients at these GABAergic synapses following climbing fiber activity. Electrical stimulation of climbing fibers in acute slices caused a decline of inhibitory postsynaptic currents recorded from Purkinje cells. Dendritic calcium-gated chloride channels of the type anoctamin 2 (ANO2) were proposed to mediate this short-term modulation of inhibition, but the significance of this process for motor control has not been established yet. Here, we report results of behavioral studies obtained from Ano2^−/− mice, a mouse line that was previously shown to lack this particular mode of ionic plasticity. The animals display motor coordination deficits that constitute a condition of mild ataxia. Moreover, motor learning is severely impaired in Ano2^−/− mice, suggesting cerebellar dysfunction. This reduced motor performance of Ano2^−/− mice highlights the significance of inhibitory control for cerebellar function and introduces calcium-dependent short-term ionic plasticity as an efficient control mechanism for neural inhibition.