Functional Magnetic Resonance Imaging of Rats with Experimental Autoimmune Encephalomyelitis Reveals Brain Cortex Remodeling

Long-access heroin self-administration induces region specific reduction of grey matter volume and microglia reactivity in the rat

In opioid use disorder (OUD) patients, a decrease in brain grey matter volume (GMV) has been reported. It is unclear whether this is the consequence of prolonged exposure to opioids or is a predisposing causal factor in OUD development. To investigate this, we conducted a structural MRI longitudinal study in NIH Heterogeneous Stock rats exposed to heroin self-administration and age-matched naïve controls housed in the same controlled environment. Structural MRI scans were acquired before (MRI1) and after (MRI2) a prolonged period of long access heroin self-administration resulting in escalation of drug intake. Heroin intake resulted in reduced GMV in various cortical and sub-cortical brain regions. In drug-naïve controls no difference was found between MRI1 and MRI2. Notably, the degree of GMV reduction in the medial prefrontal cortex (mPFC) and the insula positively correlated with the amount of heroin consumed and the escalation of heroin use. In a preliminary gene expression analysis, we identified a number of transcripts linked to immune response and neuroinflammation. This prompted us to hypothesize a link between changes in microglia homeostasis and loss of GMV. For this reason, we analyzed the number and morphology of microglial cells in the mPFC and insula. The number of neurons and their morphology was also evaluated. The primary motor cortex, where no GMV change was observed, was used as negative control. We found no differences in the number of neurons and microglia cells following heroin. However, in the same regions where reduced GMV was detected, we observed a shift towards a rounder shape and size reduction in microglia, suggestive of their homeostatic change towards a reactive state. Altogether these findings suggest that escalation of heroin intake correlates with loss of GMV in specific brain regions and that this phenomenon is linked to changes in microglial morphology.

Long-access heroin self-administration induces region specific reduction of grey matter volume and microglia reactivity in the rat

In opioid use disorder (OUD) patients, a decrease in brain grey matter volume (GMV) has been reported. It is unclear whether this is the consequence of prolonged exposure to opioids or is a predisposing causal factor in OUD development. To investigate this, we conducted a structural MRI longitudinal study in NIH Heterogeneous Stock rats exposed to heroin self-administration and age-matched naïve controls housed in the same controlled environment. Structural MRI scans were acquired before (MRI 1 ) and after (MRI 2 ) a prolonged period of long access heroin self-administration resulting in escalation of drug intake. Heroin intake resulted in reduced GMV in various cortical and sub-cortical brain regions. In drug-naïve controls no difference was found between MRI 1 and MRI 2 . Notably, the degree of GMV reduction in the medial prefrontal cortex (mPFC) and the insula positively correlated with the amount of heroin consumed and the escalation of heroin use. In a preliminary gene expression analysis, we identified a number of transcripts linked to immune response and neuroinflammation. This prompted us to hypothesize a link between changes in microglia homeostasis and loss of GMV. For this reason, we analyzed the number and morphology of microglial cells in the mPFC and insula. The number of neurons and their morphology was also evaluated. The primary motor cortex, where no GMV change was observed, was used as negative control. We found no differences in the number of neurons and microglia cells following heroin. However, in the same regions where reduced GMV was detected, we observed a shift towards a rounder shape and size reduction in microglia, suggestive of their homeostatic change towards a reactive state. Altogether these findings suggest that escalation of heroin intake correlates with loss of GMV in specific brain regions and that this phenomenon is linked to changes in microglial morphology.

Altered Neural Pathways and Related Brain Remodeling: A Rat Study Using Different Nerve Reconstructions

BACKGROUND

Function recovery is related to cortical plasticity. The brain remodeling patterns induced by alterations in peripheral nerve pathways with different nerve reconstructions are unknown.

OBJECTIVE

To explore brain remodeling patterns related to alterations in peripheral neural pathways after different nerve reconstruction surgeries.

METHODS

Twenty-four female Sprague-Dawley rats underwent complete left brachial plexus nerve transection, together with the following interventions: no nerve repair (n = 8), grafted nerve repair (n = 8), and phrenic nerve transfer (n = 8). Resting-state functional MR images of brain were acquired at the end of seventh month postsurgery. Amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and functional connectivity (FC) were compared among 3 groups. Behavioral observation and electromyography assessed nerve regeneration.

RESULTS

Compared with brachial plexus injury group, ALFF and ReHo of left entorhinal cortex decreased in nerve repair and nerve transfer groups. The nerve transfer group showed increased ALFF and ReHo than nerve repair group in left caudate putamen, right accumbens nucleus shell (AcbSh), and right somatosensory cortex. The FC between right somatosensory cortex and bilateral piriform cortices and bilateral somatosensory cortices increased in nerve repair group than brachial plexus injury and nerve transfer groups. The nerve transfer group showed increased FC between right somatosensory cortex and areas including left corpus callosum, left retrosplenial cortex, right parietal association cortex, and right dorsolateral thalamus than nerve repair group.

CONCLUSION

Entorhinal cortex is a key brain area in recovery of limb function after nerve reconstruction. Nerve transfer related brain remodeling mainly involved contralateral sensorimotor areas, facilitating directional "shifting" of motor representation.

Effect of aging on the cerebral metabolic mechanism of electroacupuncture treatment in rats with traumatic brain injury

Objective

Aging has great influence on the clinical treatment effect of cerebrovascular diseases, and evidence suggests that the effect may be associated with age-related brain plasticity. Electroacupuncture is an effective alternative treatment for traumatic brain injury (TBI). In the present study, we aimed to explore the effect of aging on the cerebral metabolic mechanism of electroacupuncture to provide new evidence for developing age-specific rehabilitation strategies.

Methods

Both aged (18 months) and young (8 weeks) rats with TBI were analyzed. Thirty-two aged rats were randomly divided into four groups: aged model, aged electroacupuncture, aged sham electroacupuncture, and aged control group. Similarly, 32 young rats were also divided into four groups: young model, young electroacupuncture, young sham electroacupuncture, and young control group. Electroacupuncture was applied to "Bai hui" (GV20) and "Qu chi" (LI11) for 8 weeks. CatWalk gait analysis was then performed at 3 days pre- and post-TBI, and at 1, 2, 4, and 8 weeks after intervention to observe motor function recovery. Positron emission computed tomography (PET/CT) was performed at 3 days pre- and post-TBI, and at 2, 4, and 8 weeks after intervention to detect cerebral metabolism.

Results

Gait analysis showed that electroacupuncture improved the forepaw mean intensity in aged rats after 8 weeks of intervention, but after 4 weeks of intervention in young rats. PET/CT revealed increased metabolism in the left (the injured ipsilateral hemisphere) sensorimotor brain areas of aged rats during the electroacupuncture intervention, and increased metabolism in the right (contralateral to injury hemisphere) sensorimotor brain areas of young rats.

Results

This study demonstrated that aged rats required a longer electroacupuncture intervention duration to improve motor function than that of young rats. The influence of aging on the cerebral metabolism of electroacupuncture treatment was mainly focused on a particular hemisphere.

Dimorphic evaluation of hippocampal changes in rat model of demyelination: A comparative functional, morphometric, and histological study

BACKGROUND

Multiple sclerosis (MS) is the most common autoimmune disease. Progressive depletion of the brain and spinal cord tissue appears at the onset of the disease. Several studies have shown the increased size of the ventricles of the brain and decreases in the area of the corpus callosum and the width of the brain. Other important symptoms of this disease are cognitive, learning, and memory disorders.

AIM

The aim of this study was to compare morphometric, histological, and functional changes in the demyelination model in both sexes.

MATERIALS AND METHODS

In this experimental study, male and female Wistar rats were studied in four experimental groups. Demyelination was induced by the injection of ethidium bromide in the ventricular region. The chronic effect of demyelination on spatial memory, movement, and coordination was investigated using the Morris Water Maze (MWM), and clinical and balance beam tests, respectively. Myelin degradation, cell death and neurogenesis were estimated using Luxol Fast Blue staining and immunohistochemistry (Caspase-3 and Nestin markers). In addition, morphometric findings were recorded for the brain and hippocampus (weight, volume, length, width).

RESULT

Demyelination increased the time and distance index and decreased the residence time in the target quarter in the water maze test (p < .001). It also increases the neuromuscular and modified neurological severity score (p < .01). Demyelination increases caspase-3 (p < .05) expression and decreases Nestin expression (p < .001), which are directly related to the extent of damage.

CONCLUSION

This study showed an interaction between hippocampal structural and functional networks in explaining spatial learning and memory in the early stages of MS.

Low Frequency Ultrasound With Injection of NMO-IgG and Complement Produces Lesions Different From Experimental Autoimmune Encephalomyelitis Mice

Neuromyelitis optica spectrum disorder (NMOSD), a relapsing autoimmune disease of the central nervous system, mainly targets the optic nerve and spinal cord. To date, all attempts at the establishment of NMOSD animal models have been based on neuromyelitis optica immunoglobulin G antibody (NMO-IgG) and mimic the disease in part. To solve this problem, we developed a rodent model by opening the blood-brain barrier (BBB) with low frequency ultrasound, followed by injection of NMO-IgG from NMOSD patients and complement to mice suffering pre-existing neuroinflammation produced by experimental autoimmune encephalomyelitis (EAE). In this study, we showed that ultrasound with NMO-IgG and complement caused marked inflammation and demyelination of both spinal cords and optic nerves compared to blank control group, as well as glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQP4) loss of spinal cords and optic nerves compared to EAE mice and EAE mice with only BBB opening. In addition, magnetic resonance imaging (MRI) revealed optic neuritis with spinal cord lesions. We further demonstrated eye segregation defects in the dorsal lateral geniculate nucleus (dLGN) of these NMOSD mice.

Synaptic Dysfunction in Multiple Sclerosis: A Red Thread from Inflammation to Network Disconnection

Multiple sclerosis (MS) has been clinically considered a chronic inflammatory disease of the white matter; however, in the last decade growing evidence supported an important role of gray matter pathology as a major contributor of MS-related disability and the involvement of synaptic structures assumed a key role in the pathophysiology of the disease. Synaptic contacts are considered central units in the information flow, involved in synaptic transmission and plasticity, critical processes for the shaping and functioning of brain networks. During the course of MS, the immune system and its diffusible mediators interact with synaptic structures leading to changes in their structure and function, influencing brain network dynamics. The purpose of this review is to provide an overview of the existing literature on synaptic involvement during experimental and human MS, in order to understand the mechanisms by which synaptic failure eventually leads to brain networks alterations and contributes to disabling MS symptoms and disease progression.

Functional Organization of Brain Network in Peripheral Neural Anastomosis Rats after Electroacupuncture: An ICA and Connectome Analysis

Acupuncture is a mild therapy in rehabilitation practice of peripheral nerve injury. Previous studies confirmed the deep participation of brain plasticity in the process of functional restoration. The therapeutic effect of acupuncture is also believed to be closely associated with brain plasticity, especially in the hypothalamus and limbic system. But the fuzzy neural mechanism somehow limits the application or improvement of this therapy. There is little information about the effect of acupuncture on topological properties of brain networks. Instead of functional segregation approach, we utilized graph theory method to analyze the large-scale and distributed properties of information processing. We first established rat model of sciatic nerve injury and performed rehabilitation therapy of electroacupuncture for 120 days. Meanwhile, we used independent component analysis to extract seven sub-networks from the whole brain. Then measurements of graph theory were calculated in each sub-network as well as the whole brain network. We found no significant difference of any measurement in whole brain network among intervention group, model group and normal group. But the assortativity, hierarchy, small-world properties of sub-network displayed significant differences among three groups. It induces changes of neural plasticity in several sub-networks instead of whole brain network. We attributed the changes to the enhancement of the short-term compensatory adaptation and the reduction of the long-term overacting regional information transmission. The present study may shed light on the vague distinction of large-scale property of brain networks after electroacupuncture, which leads to a better understanding of this ancient traditional Chinese therapy.

Validation of Chronic Restraint Stress Model in Young Adult Rats for the Study of Depression Using Longitudinal Multimodal MR Imaging

Prior research suggests that the neurobiological underpinnings of depression include aberrant brain functional connectivity, neurometabolite levels, and hippocampal volume. Chronic restraint stress (CRS) depression model in rats has been shown to elicit behavioral, gene expression, protein, functional connectivity, and hippocampal volume changes similar to those in human depression. However, no study to date has examined the association between behavioral changes and brain changes within the same animals. This study specifically addressed the correlation between the outcomes of behavioral tests and multiple 9.4 T magnetic resonance imaging (MRI) modalities in the CRS model using data collected longitudinally in the same animals. CRS involved placing young adult male Sprague Dawley rats in individual transparent tubes for 2.5 h daily over 13 d. Elevated plus maze (EPM) and forced swim tests (FSTs) confirmed the presence of anxiety-like and depression-like behaviors, respectively, postrestraint. Resting-state functional MRI (rs-fMRI) data revealed hypoconnectivity within the salience and interoceptive networks and hyperconnectivity of several brain regions to the cingulate cortex. Proton magnetic resonance spectroscopy revealed decreased sensorimotor cortical glutamate (Glu), glutamine (Gln), and combined Glu-Gln (Glx) levels. Volumetric analysis of T2-weighted images revealed decreased hippocampal volume. Importantly, these changes parallel those found in human depression, suggesting that the CRS rodent model has utility for translational studies and novel intervention development for depression.

An analytical workflow for seed-based correlation and independent component analysis in interventional resting-state fMRI studies

Resting-state functional MRI (rs-fMRI) is a task-free method of detecting spatially distinct brain regions with correlated activity, which form organised networks known as resting-state networks (RSNs). The two most widely used methods for analysing RSN connectivity are seed-based correlation analysis (SCA) and independent component analysis (ICA) but there is no established workflow of the optimal combination of analytical steps and how to execute them. Rodent rs-fMRI data from our previous longitudinal brain stimulation studies were used to investigate these two methods using FSL. Specifically, we examined: (1) RSN identification and group comparisons in ICA, (2) ICA-based denoising compared to nuisance signal regression in SCA, and (3) seed selection in SCA. In ICA, using a baseline-only template resulted in greater functional connectivity within RSNs and more sensitive detection of group differences than when an average pre/post stimulation template was used. In SCA, the use of an ICA-based denoising method in the preprocessing of rs-fMRI data and the use of seeds from individual functional connectivity maps in running group comparisons increased the sensitivity of detecting group differences by preventing the reduction in signals of interest. Accordingly, when analysing animal and human rs-fMRI data, we infer that the use of baseline-only templates in ICA and ICA-based denoising and individualised seeds in SCA will improve the reliability of results and comparability across rs-fMRI studies.

Anterior insula stimulation suppresses appetitive behavior while inducing forebrain activation in alcohol-preferring rats

The anterior insular cortex plays a key role in the representation of interoceptive effects of drug and natural rewards and their integration with attention, executive function, and emotions, making it a potential target region for intervention to control appetitive behaviors. Here, we investigated the effects of chemogenetic stimulation or inhibition of the anterior insula on alcohol and sucrose consumption. Excitatory or inhibitory designer receptors (DREADDs) were expressed in the anterior insula of alcohol-preferring rats by means of adenovirus-mediated gene transfer. Rats had access to either alcohol or sucrose solution during intermittent sessions. To characterize the brain network recruited by chemogenetic insula stimulation we measured brain-wide activation patterns using pharmacological magnetic resonance imaging (phMRI) and c-Fos immunohistochemistry. Anterior insula stimulation by the excitatory Gq-DREADDs significantly attenuated both alcohol and sucrose consumption, whereas the inhibitory Gi-DREADDs had no effects. In contrast, anterior insula stimulation failed to alter locomotor activity or deprivation-induced water drinking. phMRI and c-Fos immunohistochemistry revealed downstream activation of the posterior insula and medial prefrontal cortex, as well as of the mediodorsal thalamus and amygdala. Our results show the critical role of the anterior insula in regulating reward-directed behavior and delineate an insula-centered functional network associated with the effects of insula stimulation. From a translational perspective, our data demonstrate the therapeutic potential of circuit-based interventions and suggest that potentiation of insula excitability with neuromodulatory methods, such as repetitive transcranial magnetic stimulation (rTMS), could be useful in the treatment of alcohol use disorders.

Aberrant insular cortex connectivity in abstinent alcohol-dependent rats is reversed by dopamine D3 receptor blockade

A few studies have reported aberrant functional connectivity in alcoholic patients, but the specific neural circuits involved remain unknown. Moreover, it is unclear whether these alterations can be reversed upon treatment. Here, we used functional MRI to study resting state connectivity in rats following chronic intermittent exposure to ethanol. Further, we evaluated the effects of SB-277011-a, a selective dopamine D3 receptor antagonist, known to decrease ethanol consumption. Alcohol-dependent and control rats (N = 13/14 per group), 3 weeks into abstinence, were administered SB-277011-a or vehicle before fMRI sessions. Resting state connectivity networks were extracted by independent component analysis. A dual-regression analysis was performed using independent component maps as spatial regressors, and the effects of alcohol history and treatment on connectivity were assessed. A history of alcohol dependence caused widespread reduction of the internal coherence of components. Weaker correlation was also found between the insula cortex (IC) and cingulate cortices, key constituents of the salience network. Similarly, reduced connectivity was observed between a component comprising the anterior insular cortex, together with the caudate putamen (CPu-AntIns), and the posterior part of the IC. On the other hand, postdependent rats showed strengthened connectivity between salience and reward networks. In particular, higher connectivity was observed between insula and nucleus accumbens, between the ventral tegmental area and the cingulate cortex and between the VTA and CPu-AntIns. Interestingly, aberrant connectivity in postdependent rats was partially restored by acute administration of SB-277011-a, which, conversely, had no significant effects in naïve rats.

Alteration of metabolic connectivity in a rat model of deafferentation pain: a 18F-FDG PET/CT study

OBJECTIVE

Refractory deafferentation pain has been evidenced to be related to central nervous system neuroplasticity. In this study, the authors sought to explore the underlying glucose metabolic changes in the brain after brachial plexus avulsion, particularly metabolic connectivity.

METHODS

Rats with unilateral deafferentation following brachial plexus avulsion, a pain model of deafferentation pain, were scanned by small-animal 2-deoxy-[18F]fluoro-d-glucose (18F-FDG) PET/CT to explore the changes of metabolic connectivity among different brain regions. Thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) of the intact forepaw were also measured for evaluating pain sensitization. Brain metabolic connectivity and TWL were compared from baseline to 1 week after brachial plexus avulsion.

RESULTS

Alterations of metabolic connectivity occurred not only within the unilateral hemisphere contralateral to the injured forelimb, but also in the other hemisphere and even in the connections between bilateral hemispheres. Metabolic connectivity significantly decreased between sensorimotor-related areas within the left hemisphere (contralateral to the injured forelimb) (p < 0.05), as well as between areas across bilateral hemispheres (p < 0.05). Connectivity between areas within the right hemisphere (ipsilateral to the injured forelimb) significantly increased (p = 0.034). TWL and MWT of the left (intact) forepaw after surgery were significantly lower than those at baseline (p < 0.001).

CONCLUSIONS

This study revealed that unilateral brachial plexus avulsion facilitates pain sensitization in the opposite limb. A specific pattern of brain metabolic changes occurred in this procedure. Metabolic connectivity reorganized not only in the sensorimotor area corresponding to the affected forelimb, but also in extensive areas involving the bilateral hemispheres. These findings may broaden our understanding of central nervous system changes, as well as provide new information and a potential intervention target for nosogenesis of deafferentation pain.

Brain Metabolism in Rats with Neuropathic Pain Induced by Brachial Plexus Avulsion Injury and Treated via Electroacupuncture

PURPOSE

Brain organisation is involved in the mechanism of neuropathic pain. Acupuncture is a common clinical practise in traditional Chinese medicine for the treatment of chronic pain. This study explored electroacupuncture's effects on brain metabolism following brachial plexus avulsion injury (BPAI)-induced pain.

METHODS

A total of 32 female rats were randomised into a normal group, model group, sham electroacupuncture group, and electroacupuncture group. A pain model was included via right BPAI. The electroacupuncture intervention at cervical "Jiaji" points (C5-7) was performed for 11 weeks. The mechanical withdrawal threshold of the non-injured (left) forepaw was measured at the baseline and on days 3, 7, 14, 21, 28, 56, 84, and 112 subsequent to BPAI. Positron emission tomography (PET) was applied to explore metabolic changes on days 28, 84, and 112.

RESULTS

After electroacupuncture, the mechanical withdrawal threshold of the left forepaws was significantly elevated and the effect persisted until 4 weeks after the intervention ceased (p<0.05 or p<0.001). In the sensorimotor-related brain regions, standardised uptake values in the bilateral somatosensory and motor cortices were observed in the electroacupuncture group. Metabolism particularly increased in the right somatosensory cortex. Metabolism changes also occurred in the pain-related brain regions and emotion- and cognition-related brain regions.

CONCLUSION

The present study demonstrated the beneficial effects of electroacupuncture for relieving BPAI-induced neuropathic pain in rats. Electroacupuncture intervention might inhibit maladaptive plasticity in brain areas governing multidimensional functions, especially in sensorimotor- and cognition-related cortices.

Drug delivery to macrophages: A review of targeting drugs and drug carriers to macrophages for inflammatory diseases

Macrophages play a key role in defending against foreign pathogens, healing wounds, and regulating tissue homeostasis. Driving this versatility is their phenotypic plasticity, which enables macrophages to respond to subtle cues in tightly coordinated ways. However, when this coordination is disrupted, macrophages can aid the progression of numerous diseases, including cancer, cardiovascular disease, and autoimmune disease. The central link between these disorders is aberrant macrophage polarization, which misguides their functional programs, secretory products, and regulation of the surrounding tissue microenvironment. As a result of their important and deterministic roles in both health and disease, macrophages have gained considerable attention as targets for drug delivery. Here, we discuss the role of macrophages in the initiation and progression of various inflammatory diseases, summarize the leading drugs used to regulate macrophages, and review drug delivery systems designed to target macrophages. We emphasize strategies that are approved for clinical use or are poised for clinical investigation. Finally, we provide a prospectus of the future of macrophage-targeted drug delivery systems.

Diffusional plasticity induced by electroacupuncture intervention in rat model of peripheral nerve injury

Electroacupuncture (EA) is an adjuvant therapy for peripheral nerve injury (PNI). Both peripheral and central alterations contribute to the rehabilitation process. We employed diffusion tensor imaging (DTI) to investigate the diffusion plasticity of afferent and efferent pathways caused by EA in model of peripheral nerve injury and reparation. Twenty-four rats were divided into three groups: normal group, model group and intervention group. Rats of the model group and the intervention group underwent sciatic nerve transection and anastomosis. EA intervention was performed on the intervention group at ST-36 and GB-30 for three months. Gait assessment and DTI were conducted at days post-operative (DPO) 30, 60 and 90. We selected corticospinal tract, spinothalamic tract and internal capsule as regions of interest and analyzed diffusion metrics including fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD). FA values and RD values displayed significant differences or obvious tendency while AD values maintained a stable level. RD values displayed better indicative performance than FA in internal capsule. The intervention group presented significant correlation between RD values and Regularity Index (RI) during the intervention period. The effect of EA on peripheral nerve injury repairing rats appeared to be accelerated recovery process of sensory and motor neural pathway. We proposed that RD was a potential in vivo indicator for structural plasticity caused by EA and PNI.

The Role of Monocytes and Macrophages in Autoimmune Diseases: A Comprehensive Review

Monocytes (Mo) and macrophages (Mϕ) are key components of the innate immune system and are involved in regulation of the initiation, development, and resolution of many inflammatory disorders. In addition, these cells also play important immunoregulatory and tissue-repairing roles to decrease immune reactions and promote tissue regeneration. Several lines of evidence have suggested a causal link between the presence or activation of these cells and the development of autoimmune diseases. In addition, Mo or Mϕ infiltration in diseased tissues is a hallmark of several autoimmune diseases. However, the detailed contributions of these cells, whether they actually initiate disease or perpetuate disease progression, and whether their phenotype and functional alteration are merely epiphenomena are still unclear in many autoimmune diseases. Additionally, little is known about their heterogeneous populations in different autoimmune diseases. Elucidating the relevance of Mo and Mϕ in autoimmune diseases and the associated mechanisms could lead to the identification of more effective therapeutic strategies in the future.

Behavioral and Structural Effects of Single and Repeat Closed-Head Injury

BACKGROUND AND PURPOSE

The effects of multiple head impacts, even without detectable primary injury, on subsequent behavioral impairment and structural abnormality is yet well explored. Our aim was to uncover the dynamic changes and long-term effects of single and repetitive head injury without focal contusion on tissue microstructure and macrostructure.

MATERIALS AND METHODS

We introduced a repetitive closed-head injury rodent model (n = 70) without parenchymal lesions. We performed a longitudinal MR imaging study during a 50-day study period (T₂-weighted imaging, susceptibility-weighted imaging, and diffusion tensor imaging) as well as sequential behavioral assessment. Immunohistochemical staining for astrogliosis was examined in a subgroup of animals. Paired and independent t tests were used to evaluate the outcome change after injury and the cumulative effects of impact load, respectively.

RESULTS

There was no gross morphologic evidence for head injury such as skull fracture, contusion, or hemorrhage on micro-CT and MR imaging. A significant decrease of white matter fractional anisotropy from day 21 on and an increase of gray matter fractional anisotropy from day 35 on were observed. Smaller mean cortical volume in the double-injury group was shown at day 50 compared with sham and single injury (P < .05). Behavioral deficits (P < .05) in neurologic outcome, balance, and locomotor activity were also aggravated after double injury. Histologic analysis showed astrogliosis 24 hours after injury, which persisted throughout the study period.

CONCLUSIONS

There are measurable and dynamic changes in microstructure, cortical volume, behavior, and histopathology after both single and double injury, with more severe effects seen after double injury. This work bridges cross-sectional evidence from human subject and pathologic studies using animal models with a multi-time point, longitudinal research paradigm.

SUMOylation promotes survival and integration of neural stem cell grafts in ischemic stroke

Background

Neural stem cell (NSC)-based therapies hold great promise for treating diseases of the central nervous system (CNS). However, several fundamental problems still need to be overcome to fully exploit the clinical potential of NSC therapeutics. Chief among them is the limited survival of NSC grafts within hostile microenvironments.

Methods

Herein, we sought to engineer NSCs in an effort to increase graft survival within ischemic brain lesions via upregulation of global SUMOylation, a post-translational modification critically involved in mediating tolerance to ischemia/reperfusion.

Findings

NSCs overexpressing the SUMO E2-conjugase Ubc9 displayed resistance to oxygen-glucose-deprivation/restoration of oxygen/glucose (OGD/ROG) and enhanced neuronal differentiation in vitro, as well as increased survival and neuronal differentiation when transplanted in mice with transient middle cerebral artery occlusion in vivo.

Interpretation

Our work highlights a critical role for SUMOylation in NSC biology and identifies a biological pathway that can be targeted to increase the effectiveness of exogenous stem cell medicines in ischemic stroke.

Fund

Intramural Research Program of the NINDS/NIH, the Italian Multiple Sclerosis Foundation (FISM), the Bascule Charitable Trust, NIH-IRTA-OxCam and Wellcome Trust Research Training Fellowships.

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Ubc9-overexpressing NSCs demonstrate enhanced neuronal differentiation.

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Upregulating SUMOylation in NSCs increases resistance to ischemia/reperfusion in vitro.

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Ubc9-overexpressing NSC grafts robustly integrate within the brain of mice post-stroke.

Axonal damage in spinal cord is associated with gray matter atrophy in sensorimotor cortex in experimental autoimmune encephalomyelitis

BACKGROUND

Gray matter (GM) atrophy in brain is one of the best predictors of long-term disability in multiple sclerosis (MS), and recent findings have revealed that localized GM atrophy is associated with clinical disabilities. GM atrophy associated with each disability mapped to a distinct brain region, revealing a disability-specific atlas (DSA) of GM loss.

OBJECTIVE

To uncover the mechanisms underlying the development of localized GM atrophy.

METHODS

We used voxel-based morphometry (VBM) to evaluate localized GM atrophy and Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY) to evaluate specific pathologies in mice with experimental autoimmune encephalomyelitis (EAE).

RESULTS

We observed extensive GM atrophy throughout the cerebral cortex, with additional foci in the thalamus and caudoputamen, in mice with EAE compared to normal controls. Next, we generated pathology-specific atlases (PSAs), voxelwise mappings of the correlation between specific pathologies and localized GM atrophy. Interestingly, axonal damage (end-bulbs and ovoids) in the spinal cord strongly correlated with GM atrophy in the sensorimotor cortex of the brain.

CONCLUSION

The combination of VBM with CLARITY in EAE can localize GM atrophy in brain that is associated with a specific pathology in spinal cord, revealing a PSA of GM loss.

The Localization Research of Brain Plasticity Changes after Brachial Plexus Pain: Sensory Regions or Cognitive Regions?

Objective

Neuropathic pain after brachial plexus injury remains an increasingly prevalent and intractable disease due to inadequacy of satisfactory treatment strategies. A detailed mapping of cortical regions concerning the brain plasticity was the first step of therapeutic intervention. However, the specific mapping research of brachial plexus pain was limited. We aimed to provide some localization information about the brain plasticity changes after brachial plexus pain in this preliminary study.

Methods

24 Sprague-Dawley rats received complete brachial plexus avulsion with neuropathic pain on the right forelimb successfully. Through functional imaging of both resting-state and block-design studies, we compared the amplitude of low-frequency fluctuations (ALFF) of premodeling and postmodeling groups and the changes of brain activation when applying sensory stimulation.

Results

The postmodeling group showed significant decreases on the mechanical withdrawal threshold (MWT) in the bilateral hindpaws and thermal withdrawal latency (TWL) in the left hindpaw than the premodeling group (P < 0.05). The amplitude of low-frequency fluctuations (ALFF) of the postmodeling group manifested increases in regions of the left anterodorsal hippocampus, left mesencephalic region, left dorsal midline thalamus, and so on. Decreased ALFF was observed in the bilateral entorhinal cortex compared to that of the premodeling group. The results of block-design scan showed significant differences in regions including the limbic/paralimbic system and somatosensory cortex.

Conclusion

We concluded that the entorhinal-hippocampus pathway, which was part of the Papez circuit, was involved in the functional integrated areas of brachial plexus pain processing. The regions in the “pain matrix” showed expected activation when applying instant nociceptive stimulus but remained silent in the resting status. This research confirmed the involvement of cognitive function, which brought novel information to the potential new therapy for brachial plexus pain.

Cerebral 18F-FDG metabolism alteration in a neuropathic pain model following brachial plexus avulsion: A PET/CT study in rats

The present study aimed to investigate cerebral metabolic changes in a neuropathic pain model following deafferentation. A total of 24 Sprague-Dawley rats were included for modeling of right brachial plexus avulsion (BPA) through the posterior approach. As nerve injury would cause central sensitization and facilitate pain sensitivity in other parts of the body, thermal withdrawal latency (TWL) of the intact forepaw was assessed to investigate the level of pain perception following BPA-induced neuropathic pain. [Fluorine-18]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography (PET) was applied to the brain before and after brachial plexus avulsion to explore metabolic changes in neuropathic pain following deafferentation. The TWL of the left (intact) forepaw was significantly lower after BPA than that of baseline (p < 0.001). Using TWL as a covariate, standardized uptake values (SUVs) of ¹⁸F-FDG significantly increased in the ipsilateral dorsolateral thalamus and contralateral anterodorsal hippocampus after BPA. Conversely, SUVs in multiple brain regions decreased, including the contralateral somatosensory cortex, ipsilateral cingulate cortex, and ipsilateral temporal association cortex. The Pearson correlation analysis showed that the SUVs of the contralateral anterodorsal hippocampus and ipsilateral dorsolateral thalamus were negatively related to the TWL of the intact forepaw, whereas the SUVs in the contralateral somatosensory cortex and ipsilateral cingulate cortex were positively related to it (p < 0.05). These findings indicate that upregulation of metabolism in the anterodorsal hippocampus and dorsolateral thalamus and downregulation metabolism in the contralateral somatosensory cortex and ipsilateral cingulate cortex could be a unique pattern of metabolic changes for neuropathic pain following brachial plexus avulsion.

Segmented Echo Planar Imaging Improves Detection of Subcortical Functional Connectivity Networks in the Rat Brain

Susceptibility artifacts in the vicinity of aural and nasal cavities result in significant signal drop-out and image distortion in echo planar imaging of the rat brain. These effects may limit the study of resting state functional connectivity in deep brain regions. Here, we explore the use of segmented EPI for resting state fMRI studies in the rat, and assess the relative merits of this method compared to single shot EPI. Sequences were evaluated in terms of signal-to-noise ratio, geometric distortions, data driven detection of resting state networks and group level correlations of time series. Multishot imaging provided improved SNR, temporal SNR and reduced geometric distortion in deep areas, while maintaining acceptable overall image quality in cortical regions. Resting state networks identified by independent component analysis were consistent across methods, but multishot EPI provided a more robust and accurate delineation of connectivity patterns involving deep regions typically affected by susceptibility artifacts. Importantly, segmented EPI showed reduced between-subject variability and stronger statistical significance of pairwise correlations at group level over the whole brain and in particular in subcortical regions. Multishot EPI may represent a valid alternative to snapshot methods in functional connectivity studies, particularly for the investigation of subcortical regions and deep gray matter nuclei.

Brain grey matter volume reduction and anxiety-like behavior in lipopolysaccharide-induced chronic pulmonary inflammation rats: A structural MRI study with histological validation

While there have been multiple fMRI studies into the brain functional changes after acutely stimulated peripheral infection, knowledge for the effect of chronic peripheral infection on whole brain morphology is still quite limited. The present study was designed to investigate the brain structural and emotional changes after peripheral local infection initiated chronic systemic inflammation and the relationship between circulating inflammatory markers and brain grey matter. Specifically, in-vivo T2-weighted MRI was performed on rats with lipopolysaccharide (LPS)-induced chronic pulmonary inflammation (CPI) and those without. Grey matter volume was quantified using diffeomorphic anatomical registration through exponentiated lie (DARTEL) enhanced voxel-based morphometry followed by between-group comparison. Open field experiment was conducted to test the potential anxiety-like behaviors after CPI, along with the ELISA estimated inflammatory markers were correlated to grey matter volume. Guided by image findings, we undertook a focused histological investigation with immunefluorescence and Nissl staining. A widespread decrease of grey matter volume in CPI-model rats was revealed. 8 of the 12 measured inflammatory markers presented differential neuroanatomical correlation patterns with three of the pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) and CRP being the most notable. Lower grey matter volumes in some of the inflammatory markers related regions (amygdala, CA2 and cingulate cortex) were associated with more-severe anxiety-like behaviors. Furthermore, grey matter volumes in amygdala and CA3 were correlated negatively with the expressions of glial proteins (S100β and Nogo-A), while the grey matter volume in hypo-thalamus was changing positively with neural cell area. Overall, the neuroanatomical association patterns and the histopathology underpinning the MRI observations we demonstrated here would probably serve as one explanation for the cerebral and emotional deficits presented in the patients with CPI, which would furthermore yield new insights into the adverse effects the many other systemic inflammation and inflammatory autoimmune diseases would pose on brain morphology.

Optic nerve involvement in experimental autoimmune encephalomyelitis to homologous spinal cord homogenate immunization in the dark agouti rat

Dark-Agouti rats were immunized with spinal cord homogenate to develop Experimental Autoimmune Encephalomyelitis, a model of multiple sclerosis. We assessed motor signs and recorded VEPs for five or eight weeks with epidural or epidermal electrodes, respectively, with final histopathology of optic nerves (ONs). Injected rats exhibited motor deficits a week after immunization. VEP delays arose from the 2nd to the 5th week, when a recovery occurred in epidermal-recorded rats. ON damage appeared in epidural-, but not in epidermal-recorded rats, probably due to a remyelination process. VEP could be exploited as neurophysiological marker to test novel treatments against neurodegeneration involving ONs.

Magnetosomes Extracted from Magnetospirillum gryphiswaldense as Theranostic Agents in an Experimental Model of Glioblastoma

Magnetic fluid hyperthermia (MFH) with chemically synthesized nanoparticles is currently used in clinical trials as it destroys tumor cells with an extremely localized deposition of thermal energy. In this paper, we investigated an MFH protocol based on magnetic nanoparticles naturally produced by magnetotactic bacteria: magnetosomes. The efficacy of such protocol is tested in a xenograft model of glioblastoma. Mice receive a single intratumoral injection of magnetosomes, and they are exposed three times in a week to an alternating magnetic field with concurrent temperature measurements. MRI is used to visualize the nanoparticles and to monitor tumor size before and after the treatment. Statistically significant inhibition of the tumor growth is detected in subjects exposed to the alternating magnetic field compared to control groups. Moreover, thanks to magnetosomes high transversal relaxivity, their effective delivery to the tumor tissue is monitored by MRI. It is apparent that the efficacy of this protocol is limited by inhomogeneous delivery of magnetosomes to tumor tissue. These results suggest that naturally synthesized magnetosomes could be effectively considered as theranostic agent candidates for hyperthermia based on iron oxide nanoparticles.

Stepwise occlusion of the carotid arteries of the rat: MRI assessment of the effect of donepezil and hypoperfusion-induced brain atrophy and white matter microstructural changes

Bilateral common carotid artery occlusion (BCCAo) in the rat is a widely used animal model of vascular dementia and a valuable tool for preclinical pharmacological drug testing, although the varying degrees of acute focal ischemic lesions it induces could interfere with its translational value. Recently, a modification to the BCCAo model, the stepwise occlusion of the two carotid arteries, has been introduced. To acquire objective translatable measures, we used longitudinal multimodal magnetic resonance imaging (MRI) to assess the effects of semi-chronic (8 days) donepezil treatment in this model, with half of the Wistar rats receiving the treatment one week after the stepwise BCCAo. With an ultrahigh field MRI, we measured high-resolution anatomy, diffusion tensor imaging, cerebral blood flow measurements and functional MRI in response to whisker stimulation, to evaluate both the structural and functional effects of the donepezil treatment and stepwise BCCAo up to 5 weeks post-occlusion. While no large ischemic lesions were detected, atrophy in the striatum and in the neocortex, along with widespread white matter microstructural changes, were found. Donepezil ameliorated the transient drop in the somatosensory BOLD response in distant cortical areas, as detected 2 weeks after the occlusion but the drug had no effect on the long term structural changes. Our results demonstrate a measurable functional MRI effect of the donepezil treatment and the importance of diffusion MRI and voxel based morphometry (VBM) analysis in the translational evaluation of the rat BCCAo model.

Protective potential of dimethyl fumarate in a mouse model of thalamocortical demyelination

Alterations in cortical cellular organization, network functionality, as well as cognitive and locomotor deficits were recently suggested to be pathological hallmarks in multiple sclerosis and corresponding animal models as they might occur following demyelination. To investigate functional changes following demyelination in a well-defined, topographically organized neuronal network, in vitro and in vivo, we focused on the primary auditory cortex (A1) of mice in the cuprizone model of general de- and remyelination. Following myelin loss in this model system, the spatiotemporal propagation of incoming stimuli in A1 was altered and the hierarchical activation of supra- and infragranular cortical layers was lost suggesting a profound effect exerted on neuronal network level. In addition, the response latency in field potential recordings and voltage-sensitive dye imaging was increased following demyelination. These alterations were accompanied by a loss of auditory discrimination abilities in freely behaving animals, a reduction of the nuclear factor-erythroid 2-related factor-2 (Nrf-2) protein in the nucleus in histological staining and persisted during remyelination. To find new strategies to restore demyelination-induced network alteration in addition to the ongoing remyelination, we tested the cytoprotective potential of dimethyl fumarate (DMF). Therapeutic treatment with DMF during remyelination significantly modified spatiotemporal stimulus propagation in the cortex, reduced the cognitive impairment, and prevented the demyelination-induced decrease in nuclear Nrf-2. These results indicate the involvement of anti-oxidative mechanisms in regulating spatiotemporal cortical response pattern following changes in myelination and point to DMF as therapeutic compound for intervention.

Resting-state fMRI study of brain activation using low-intensity repetitive transcranial magnetic stimulation in rats

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation technique used to treat many neuropsychiatric conditions. However, the mechanisms underlying its mode of action are still unclear. This is the first rodent study using resting-state functional MRI (rs-fMRI) to examine low-intensity (LI) rTMS effects, in an effort to provide a direct means of comparison between rodent and human studies. Using anaesthetised Sprague-Dawley rats, rs-fMRI data were acquired before and after control or LI-rTMS at 1 Hz, 10 Hz, continuous theta burst stimulation (cTBS) or biomimetic high-frequency stimulation (BHFS). Independent component analysis revealed LI-rTMS-induced changes in the resting-state networks (RSN): (i) in the somatosensory cortex, the synchrony of resting activity decreased ipsilaterally following 10 Hz and bilaterally following 1 Hz stimulation and BHFS, and increased ipsilaterally following cTBS; (ii) the motor cortex showed bilateral changes following 1 Hz and 10 Hz stimulation, a contralateral decrease in synchrony following BHFS, and an ipsilateral increase following cTBS; and (iii) hippocampal synchrony decreased ipsilaterally following 10 Hz, and bilaterally following 1 Hz stimulation and BHFS. The present findings demonstrate that LI-rTMS modulates functional links within the rat RSN with frequency-specific outcomes, and the observed changes are similar to those described in humans following rTMS.

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.

Combined rTMS/fMRI Studies: An Overlooked Resource in Animal Models

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation technique, which has brain network-level effects in healthy individuals and is also used to treat many neurological and psychiatric conditions in which brain connectivity is believed to be abnormal. Despite the fact that rTMS is being used in a clinical setting and animal studies are increasingly identifying potential cellular and molecular mechanisms, little is known about how these mechanisms relate to clinical changes. This knowledge gap is amplified by non-overlapping approaches used in preclinical and clinical rTMS studies: preclinical studies are mostly invasive, using cellular and molecular approaches, while clinical studies are non-invasive, including functional magnetic resonance imaging (fMRI), TMS electroencephalography (EEG), positron emission tomography (PET), and behavioral measures. A non-invasive method is therefore needed in rodents to link our understanding of cellular and molecular changes to functional connectivity changes that are clinically relevant. fMRI is the technique of choice for examining both short and long term functional connectivity changes in large-scale networks and is becoming increasingly popular in animal research because of its high translatability, but, to date, there have been no reports of animal rTMS studies using this technique. This review summarizes the main studies combining different rTMS protocols with fMRI in humans, in both healthy and patient populations, providing a foundation for the design of equivalent studies in animals. We discuss the challenges of combining these two methods in animals and highlight considerations important for acquiring clinically-relevant information from combined rTMS/fMRI studies in animals. We believe that combining rTMS and fMRI in animal models will generate new knowledge in the following ways: functional connectivity changes can be explored in greater detail through complementary invasive procedures, clarifying mechanism and improving the therapeutic application of rTMS, as well as improving interpretation of fMRI data. And, in a more general context, a robust comparative approach will refine the use of animal models of specific neuropsychiatric conditions.

A Longitudinal Mapping Study on Cortical Plasticity of Peripheral Nerve Injury Treated by Direct Anastomosis and Electroacupuncture in Rats

OBJECTIVE

We used functional magnetic resonance imaging to provide a longitudinal description of cortical plasticity caused by electroacupuncture (EA) of sciatic nerve transection and direct anastomosis in rats.

METHODS

Sixteen rats in a sciatic nerve transection and direct anastomosis model were randomly divided into intervention and control groups. EA intervention in the position of ST-36, GB-30 was conducted continuously for 4 months in the intervention group. Functional magnetic resonance imaging and gait assessment were performed every month after intervention.

RESULTS

The somatosensory area was more activated in the first 2 months and then deactivated in the rest 2 months when EA was applied. The pain-related areas had the same activation pattern as the somatosensory area. The limbic/paralimbic areas fluctuated more during the EA intervention, which was not constantly activated or deactivated as previous studies reported. We attributed such changes in somatosensory and pain-related areas to the gradual reduction of sensory afferentation. The alterations in limbic/paralimbic system might be associated with the confrontation between the upregulating effect of paresthesia or pain and the downregulating effect of EA intervention through the autonomic nerve system. The gait analysis showed significantly higher maximum contact mean intensity in the intervention group.

CONCLUSIONS

The alterations in the brain brought about by the long-term therapeutic effect of EA could be described as a synchronized activation pattern in the somatosensory and pain-related areas and a fluctuating pattern in the limbic/paralimbic system.

Macrophage-Derived Extracellular Succinate Licenses Neural Stem Cells to Suppress Chronic Neuroinflammation

Neural stem cell (NSC) transplantation can influence immune responses and suppress inflammation in the CNS. Metabolites, such as succinate, modulate the phenotype and function of immune cells, but whether and how NSCs are also activated by such immunometabolites to control immunoreactivity and inflammatory responses is unclear. Here, we show that transplanted somatic and directly induced NSCs ameliorate chronic CNS inflammation by reducing succinate levels in the cerebrospinal fluid, thereby decreasing mononuclear phagocyte (MP) infiltration and secondary CNS damage. Inflammatory MPs release succinate, which activates succinate receptor 1 (SUCNR1)/GPR91 on NSCs, leading them to secrete prostaglandin E2 and scavenge extracellular succinate with consequential anti-inflammatory effects. Thus, our work reveals an unexpected role for the succinate-SUCNR1 axis in somatic and directly induced NSCs, which controls the response of stem cells to inflammatory metabolic signals released by type 1 MPs in the chronically inflamed brain.

A new focal model resembling features of cortical pathology of the progressive forms of multiple sclerosis: Influence of innate immunity

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of unknown aetiology that causes neurological disabilities in young adults. MS displays different clinical patterns, including recurrent episodes with remission periods ("relapsing-remitting MS" (RRMS)), which can progress over several years to a secondary progressive form (SPMS). However, 10% of patients display persistent progression at the onset of disease ("primary progressive MS" (PPMS)). Currently, no specific therapeutic agents are available for the progressive forms, mainly because the underlying pathogenic mechanisms are not clear and because no animal models have been specifically developed for these forms. The development of MS animal models is required to clarify the pathological mechanisms and to test novel therapeutic agents. In the present work, we overexpressed interleukin 1 beta (IL-1β) in the cortex to develop an animal model reflecting the main pathological hallmarks of MS. The treated animals presented with neuroinflammation, demyelination, glial activation, and neurodegeneration along with cognitive symptoms and MRI images consistent with MS pathology. We also demonstrated the presence of meningeal inflammation close to cortical lesions, with characteristics similar to those described in MS patients. Systemic pro-inflammatory stimulation caused a flare-up of the cortical lesions and behavioural symptoms, including impairment of working memory and the appearance of anxiety-like symptoms. Our work demonstrated induced cortical lesions, reflecting the main histopathological hallmarks and cognitive impairments characterizing the cortical pathology described in MS patients with progressive forms of the disease.

MRI in the Study of Animal Models of Neurodegenerative Diseases

Magnetic Resonance Imaging (MRI) is an important tool to study various animal models of degenerative diseases. This chapter describes routine protocols of T ₁-, T ₂-, and T ₂*-weighted and diffusion-weighted MRI for rodent brain and spinal cord. These protocols can be used to measure atrophy, axonal and myelin injury and changes in white matter connectivity.

Polymer-coated superparamagnetic iron oxide nanoparticles as T2 contrast agent for MRI and their uptake in liver

Aim:

To study the efficiency of multifunctional polymer-based superparamagnetic iron oxide nanoparticles (bioferrofluids) as a T₂ magnetic resonance contrast agent and their uptake and toxicity in liver.

Materials & methods:

Mice were intravenously injected with bioferrofluids and Endorem^®. The magnetic resonance efficiency, uptake and in vivo toxicity were investigated by means of magnetic resonance imaging (MRI) and histological techniques.

Results:

Bioferrofluids are a good T₂ contrast agent with a higher r₂/r₁ ratio than Endorem. Bioferrofluids have a shorter blood circulation time and persist in liver for longer time period compared with Endorem. Both bioferrofluids and Endorem do not generate any noticeable histological lesions in liver over a period of 60 days post-injection.

Conclusion:

Our bioferrofluids are powerful diagnostic tool without any observed toxicity over a period of 60 days post-injection.

Several superparamagnetic iron oxide nanoparticles (SPIONs) preparations have been approved by US FDA for clinical use as MRI contrast agents. In recent years, we have been developing a synthetic multifunctional platform for SPIONs based on the use of polymers. In this report, we explored the diagnostic potential of these nanoparticles (herein called bioferrofluids) as an MRI contrast agent and their uptake in liver, without neglecting their toxicological effects. Results show that our bioferrofluids are a good T₂ contrast agent without any observed toxicity in liver.

Disrupted functional connectivity between the periaqueductal gray and other brain regions in a rat model of recurrent headache

Functional connectivity (FC) has been used to investigate the pathophysiology of migraine. We aimed to identify atypical FC between the periaqueductal gray (PAG) and other brain areas in rats induced by repeated meningeal nociception. The rat model was established by infusing an inflammatory soup (IS) through supradural catheters in conscious rats. Quiescent and face-grooming behaviors were observed to assess nociceptive behavior. FC analysis seeded on the PAG was performed on rats 21 days after IS infusion. The rats exhibited nociceptive behavior correlates of human behaviors associated with migraine after IS infusion. The PAG showed increased FC with the prefrontal cortex, cingulate gyrus, and motor cortex but decreased FC with the basal ganglia, dorsal lateral thalamus, internal capsule and prelimbic cortex in the rat model. The atypical FC of the PAG with brain regions in the rat model that are involved in nociception, somatosensory processing, emotional processing, and pain modulation are consistent with the clinical data from migraineurs, indicate that resting-state FC changes in migraine patients may be a consequence of headache attacks, and further validate this rat model of chronic migraine.

MRI reveals therapeutical efficacy of stem cells: An experimental study on the SOD1(G93A) animal model

PURPOSE

The first part of the experiment identifies and validates MRI biomarkers distinctive of the disease progression in the transgenic superoxide dismutase gene (SOD1(G93A)) animal model. The second part assesses the efficacy of a mesenchymal stem cell-based therapy through the MRI biomarkers previously defined.

METHODS

The first part identifies MRI differences between SOD1(G93A) and healthy mice. The second part of the experiment follows the disease evolution of stem cell-treated and non-stem-cell treated SOD1(G93A) mice. The analysis focused on voxel-based morphometry and T2 mapping on the brain tissues, and T2-weighted imaging and diffusion tensor imaging (DTI) on the hind limbs.

RESULTS

Comparing diseased mice to healthy control revealed gray matter alterations in the brainstem area, accompanied by increased T2 relaxation time. Differences in muscle volume, muscle signal intensity, fractional anisotropy, axial diffusivity, and radial diffusivity were measured in the hind limbs. In the comparison between stem cell-treated mice and nontreated ones, differences in muscle volume, muscle signal intensity, and DTI-derived maps were found.

CONCLUSION

MRI-derived biomarkers can be used to identify differences between stem cell-treated and nontreated SOD1(G93A) mice. Magn Reson Med 79:459-469, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Central sensitization-related changes of effective and functional connectivity in the rat inflammatory trigeminal pain model

Central sensitization is a key mechanism in the pathology of several neuropathic pain disorders. We aimed to investigate the underlying brain connectivity changes in a rat model of chronic pain. Non-noxious whisker stimulation was used to evoke blood-oxygen-level-dependent (BOLD) responses in a block-design functional Magnetic Resonance Imaging (fMRI) experiment on 9.4T. Measurements were repeated two days and one week after injecting complete Freund's adjuvant into the rats' whisker pad. We found that acute pain reduced activation in the barrel cortex, most probably due to a plateau effect. After one week, increased activation of the anterior cingulate cortex was found. Analyses of effective connectivity driven by stimulus-related activation revealed that chronic pain-related central sensitization manifested as a widespread alteration in the activity of the somatosensory network. Changes were mainly mediated by the anterior cingulate cortex and the striatum and affected the somatosensory and motor cortices and the superior colliculus. Functional connectivity analysis of nested BOLD oscillations justified that the anterior cingular-somatosensory interplay is a key element of network changes. Additionally, a decreased cingulo-motor functional connectivity implies that alterations also involve the output tract of the network. Our results extend the knowledge about the role of the cingulate cortex in the chronification of pain and indicate that integration of multiple connectivity analysis could be fruitful in studying the central sensitization in the pain matrix.

In vivo imaging techniques: a new era for histochemical analysis

In vivo imaging techniques can be integrated with classical histochemistry to create an actual histochemistry of water. In particular, Magnetic Resonance Imaging (MRI), an imaging technique primarily used as diagnostic tool in clinical/preclinical research, has excellent anatomical resolution, unlimited penetration depth and intrinsic soft tissue contrast. Thanks to the technological development, MRI is not only capable to provide morphological information but also and more interestingly functional, biophysical and molecular. In this paper we describe the main features of several advanced imaging techniques, such as MRI microscopy, Magnetic Resonance Spectroscopy, functional MRI, Diffusion Tensor Imaging and MRI with contrast agent as a useful support to classical histochemistry.

Characterization of gray matter atrophy following 6-hydroxydopamine lesion of the nigrostriatal system

BACKGROUND

The unilaterally-lesioned 6-hydroxydopamine (6-OHDA) rat is one of the most commonly used experimental models of Parkinson's disease (PD). Here we investigated whether magnetic resonance imaging (MRI) that is widely used in human PD research, has the potential to non-invasively detect macroscopic structural brain changes in the 6-OHDA rat in ways translatable to humans.

METHODS

We measured the gray matter (GM) composition in the unilateral 6-OHDA rat in comparison to sham animals using whole-brain voxel-based morphometry (VBM) - an unbiased MR image analysis technique. The number of nigral dopamine (DA) neurons and the density of their cortical projections were examined post-mortem using immunohistochemistry.

RESULTS

VBM revealed widespread bilateral changes in gray matter volume (GMV) on a topographic scale in the brains of 6-OHDA rats, compared to sham-operated rats. The greatest changes were in the lesioned hemisphere, which displayed reductions of GMV in motor, cingulate and somatosensory cortex. Histopathological results revealed dopaminergic cell loss in the substantia nigra (SN) and a denervation in the striatum, as well as in the frontal, somatosensory and cingulate cortices.

CONCLUSION

Unilateral nigrostriatal 6-OHDA lesioning leads to widespread GMV changes, which extend beyond the nigrostriatal system and resemble advanced Parkinsonism. This study highlights the potential of structural MRI, and VBM in particular, for the system-level phenotyping of rodent models of Parkinsonism and provides a methodological framework for future studies in novel rodent models as they become available to the research community.

Altered excitatory-inhibitory balance within somatosensory cortex is associated with enhanced plasticity and pain sensitivity in a mouse model of multiple sclerosis

BACKGROUND

Chronic neuropathic pain is a common symptom of multiple sclerosis (MS). MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) has been used as an animal model to investigate the mechanisms of pain in MS. Previous studies have implicated sensitization of spinal nociceptive networks in the pathogenesis of pain in EAE. However, the involvement of supraspinal sites of nociceptive integration, such as the primary somatosensory cortex (S1), has not been defined. We therefore examined functional, structural, and immunological alterations in S1 during the early stages of EAE, when pain behaviors first appear. We also assessed the effects of the antidepressant phenelzine (PLZ) on S1 alterations and nociceptive (mechanical) sensitivity in early EAE. PLZ has been shown to restore central nervous system (CNS) tissue concentrations of GABA and the monoamines (5-HT, NA) in EAE. We hypothesized that PLZ treatment would also normalize nociceptive sensitivity in EAE by restoring the balance of excitation and inhibition (E-I) in the CNS.

METHODS

We used in vivo flavoprotein autofluorescence imaging (FAI) to assess neural ensemble responses in S1 to vibrotactile stimulation of the limbs in early EAE. We also used immunohistochemistry (IHC), and Golgi-Cox staining, to examine synaptic changes and neuroinflammation in S1. Mechanical sensitivity was assessed at the clinical onset of EAE with Von Frey hairs.

RESULTS

Mice with early EAE exhibited significantly intensified and expanded FAI responses in S1 compared to controls. IHC revealed increased vesicular glutamate transporter (VGLUT1) expression and disrupted parvalbumin+ (PV+) interneuron connectivity in S1 of EAE mice. Furthermore, peri-neuronal nets (PNNs) were significantly reduced in S1. Morphological analysis of excitatory neurons in S1 revealed increased dendritic spine densities. Iba-1+ cortical microglia were significantly elevated early in the disease. Chronic PLZ treatment was found to normalize mechanical thresholds in EAE. PLZ also normalized S1 FAI responses, neuronal morphologies, and cortical microglia numbers and attenuated VGLUT1 reactivity-but did not significantly attenuate the loss of PNNs.

CONCLUSIONS

These findings implicate a pro-excitatory shift in the E-I balance of the somatosensory CNS, arising early in the pathogenesis EAE and leading to large-scale functional and structural plasticity in S1. They also suggest a novel antinociceptive effect of PLZ treatment.

A novel quantitative high-throughput screen identifies drugs that both activate SUMO conjugation via the inhibition of microRNAs 182 and 183 and facilitate neuroprotection in a model of oxygen and glucose deprivation

The conjugation/de-conjugation of Small Ubiquitin-like Modifier (SUMO) has been shown to be associated with a diverse set of physiologic/pathologic conditions. The clinical significance and ostensible therapeutic utility offered via the selective control of the global SUMOylation process has become readily apparent in ischemic pathophysiology. Herein, we describe the development of a novel quantitative high-throughput screening (qHTS) system designed to identify small molecules capable of increasing SUMOylation via the regulation/inhibition of members of the microRNA (miRNA)-182 family. This assay employs a SHSY5Y human neuroblastoma cell line stably transfected with a dual firefly-Renilla luciferase reporter system for identification of specific inhibitors of either miR-182 or miR-183. In this study, we have identified small molecules capable of inducing increased global conjugation of SUMO in both SHSY5Y cells and rat E18-derived primary cortical neurons. The protective effects of a number of the identified compounds were confirmed via an in vitro ischemic model (oxygen/glucose deprivation). Of note, this assay can be easily repurposed to allow high-throughput analyses of the potential drugability of other relevant miRNA(s) in ischemic pathobiology.

Synaptopathy connects inflammation and neurodegeneration in multiple sclerosis

Multiple sclerosis (MS) has long been regarded as a chronic inflammatory disease of the white matter that leads to demyelination and eventually to neurodegeneration. In the past decade, several aspects of MS pathogenesis have been challenged, and degenerative changes of the grey matter, which are independent of demyelination, have become a topic of interest. CNS inflammation in MS and experimental autoimmune encephalomyelitis (EAE; a disease model used to study MS in rodents) causes a marked imbalance between GABAergic and glutamatergic transmission, and a loss of synapses, all of which leads to a diffuse 'synaptopathy'. Altered synaptic transmission can occur early in MS and EAE, independently of demyelination and axonal loss, and subsequently causes excitotoxic damage. Inflammation-driven synaptic abnormalities are emerging as a prominent pathogenic mechanism in MS-importantly, they are potentially reversible and, therefore, represent attractive therapeutic targets. In this Review, we focus on the connection between inflammation and synaptopathy in MS and EAE, which sheds light not only on the pathophysiology of MS but also on that of primary neurodegenerative disorders in which inflammatory processes contribute to disease progression.

Prophylactic Effect of BIO-1211 Small-Molecule Antagonist of VLA-4 in the EAE Mouse Model of Multiple Sclerosis

BACKGROUND AND PURPOSE

Some functional limitations and economic burden of therapeutic antibodies indicated that introducing of alternative therapeutic compounds with same or different mechanism of action could be worthwhile. In this regard small-molecule antagonists can have a wide range of impacts, so in this research, we examine the prophylactic effects of BIO-1211 [Very Late Antigen-4 (VLA4) blocker], in experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis in comparison with commercial available medicine, Natalizumab (NTZ)].

METHODS

EAE was induced by subcutaneous immunization of myelin oligodendrocyte glycoprotein (MOG35-55) in 8-week-old C57BL/6 mice. During EAE induction, mice were separated to distinct groups and provided either BIO-1211 (5 and 10 mg/kg) or NTZ (5 mg/kg) and co-administration of these two compounds. After 21 days, neuro-inflammatory responses were analyzed using qRT-PCR, western blot, and ELISA methods. Pervade of immune cells to brain was examined by Evans blue staining and immunohistochemistry (IHC) analysis of specific markers of microglia/monocytes (CD11b) and leukocytes (CD45).

RESULTS

Targeted disruption of VLA4/VCAM1 interactions, by BIO-1211 agonist in mice, results in reduced cytokines expression, leukocyte trafficking, and inhibition of inflammatory responses in EAE (p < 0.01) in a dose-independent manner (data not shown). Mice treated with both BIO-1211 and NTZ exhibited a considerable depletion in the EAE clinical score, which correlated with decreased expression of TNF-α, IL-17, IFN-γ and pervade of CD11b(+) and CD45(+) cells into the cerebral cortex.

CONCLUSION

Our results indicated that BIO12-11 compound would be an useful tool to further understand the biological roles of VLA4/VCAM1 interactions, and could also be considered as EAE-suppressing agent.