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

Genetic and Pharmacological Modulation of P75 Neurotrophin Receptor Attenuate Brain Damage After Ischemic Stroke in Mice

The precursor nerve growth factor (ProNGF) and its receptor p75 neurotrophin receptor (p75NTR) are upregulated in several brain diseases, including ischemic stroke. The activation of p75NTR is associated with neuronal apoptosis and inflammation. Thus, we hypothesized that p75NTR modulation attenuates brain damage and improves functional outcomes after ischemic stroke. Two sets of experiments were performed. (1) Adult wild-type (WT) C57BL/6 J mice were subjected to intraluminal suture-middle cerebral artery occlusion (MCAO) to induce cerebral ischemia. Pharmacological inhibitor of p75NTR, LM11A-31 (50 mg/kg), or normal saline was administered intraperitoneally (IP) 1 h post-MCAO, and animals survived for 24 h. (2) Adult p75NTR heterozygous knockout (p75NTR+/-) and WT were subjected to photothrombotic (pMCAO) to induce ischemic stroke, and the animals survived for 72 h. The sensory-motor function of animals was measured using Catwalk XT. The brain samples were collected to assess infarction volume, edema, hemorrhagic transformation, neuroinflammation, and signaling pathway at 24 and 72 h after the stroke. The findings described that pharmacological inhibition and genetic knocking down of p75NTR reduce infarction size, edema, and hemorrhagic transformation following ischemic stroke. Additionally, p75NTR modulation significantly decreased several anti-apoptosis markers and improved sensory motor function compared to the WT mice following ischemic stroke. Our observations exhibit that the involvement of p75NTR in ischemic stroke and modulation of p75NTR could improve the outcome of ischemic stroke by increasing cell survival and enhancing motor performance. LM11A-31 has the potential to be a promising therapeutic agent for ischemic stroke. However, more evidence is needed to illuminate the efficacy of LM11A-31 in ischemic stroke.

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.

A Novel Improved Thromboembolism-Based Rat Stroke Model That Meets the Latest Standards in Preclinical Studies

The animal thromboembolic model of ischemia perfectly mimics human ischemic stroke which remains the leading cause of disability and mortality in humans. The development of new treatment strategies was therefore imperative. The purpose of this study is to improve the thromboembolic stroke model in rats in order to design experiments that use motor tests, and are in accordance with the 3R principles to prevent complications and maintain the same size of the infarct repeatedly. Tail vein dye application, a protective skull mask and a stress minimization protocol were used as additional modifications to the animal stroke model. These modifications significantly minimized the pain and stress severity of the procedures in this model. In our experimental group of Long-Evans rats, a photo-induced stroke was caused by the application of a photosensitive dye (Rose Bengal) activated with white-light irradiation, thus eliminating the need to perform a craniotomy. The animals' neurological status was evaluated using a runway elevated test. Histological examination of the brain tissue was performed at 12, 24 and 48 h, and seven days post-stroke. Tissue examination revealed necrotic foci in the cortex and the subcortical regions of the ipsilateral hemisphere in all experimental groups. Changes in the area, width and depth of the necrotic focus were observed over time. All the experimental groups showed motor disturbances after stroke survival. In the proposed model, photochemically-induced stroke caused long-term motor deficits, showed high reproducibility and low mortality rates. Consequently, the animals could participate in motor tests which are particularly suitable for assessing the efficacy of neuro-regenerative therapies, while remaining in line with the latest trends in animal experimental design.

Transcranial-Direct-Current-Stimulation Accelerates Motor Recovery After Cortical Infarction in Mice: The Interplay of Structural Cellular Responses and Functional Recovery

BACKGROUND

Transcranial direct current stimulation (tDCS) promotes recovery after stroke in humans. The underlying mechanisms, however, remain to be elucidated. Animal models suggest tDCS effects on neuroinflammation, stem cell proliferation, neurogenesis, and neural plasticity.

OBJECTIVE

In a longitudinal study, we employed tDCS in the subacute and chronic phase after experimental focal cerebral ischemia in mice to explore the relationship between functional recovery and cellular processes.

METHODS

Mice received photothrombosis in the right motor cortex, verified by Magnetic Resonance Imaging. A composite neuroscore quantified subsequent functional deficits. Mice received tDCS daily: either 5 sessions from day 5 to 9, or 10 sessions with days 12 to 16 in addition. TDCS with anodal or cathodal polarity was compared to sham stimulation. Further imaging to assess proliferation and neuroinflammation was performed by immunohistochemistry at different time points and Positron Emission Tomography at the end of the observation time of 3 weeks.

RESULTS

Cathodal tDCS at 198 kC/m² (220 A/m²) between days 5 and 9 accelerated functional recovery, increased neurogenesis, decreased microglial activation, and mitigated CD16/32-expression associated with M1-phenotype. Anodal tDCS exerted similar effects on neurogenesis and microglial polarization but not on recovery of function or microglial activation. TDCS on days 12 to 16 after stroke did not induce any further effects, suggesting that the therapeutic time window was closed by then.

CONCLUSION

Overall, data suggest that non-invasive neuromodulation by tDCS impacts neurogenesis and microglial activation as critical cellular processes influencing functional recovery during the early phase of regeneration from focal cerebral ischemia.

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.

Protective role of mRNA demethylase FTO on axon guidance molecules of nigro-striatal projection system in manganese-induced parkinsonism

One of the major environmental factors that induce PD is Manganese (Mn). Cellular and molecular mechanism of parkinsonism caused by Mn has not been explored clearly. The results of in vivo and in vitro experiments showed that Mn exposure caused abnormal projection of dopaminergic neurons and decreased mRNA expression and protein levels of FTO. This is due to Mn-induced the upregulation of Foxo3a. Using the cell model of overexpression of FTO, we found that FTO could antagonize Mn-induced the down-regulation of axon guidance molecule ephrin-B2 through RNA-seq, MeRIP-qPCR, and RT-qPCR experiments. Through RIP-seq and actinomycin D experiments, it was found that FTO can up-regulate the mRNA m⁶A level of ephrin-B2, which can be recognized by YTHDF2 and degraded. Finally, it is proved that Mn induces dopaminergic neurons projection injury and motor dysfunction through Foxo3a/FTO/m⁶A/ephrin-B2/YTHDF2 signal pathway.