Glial Reaction Research Articles

Norepinephrine Drives Sleep Fragmentation Activation of Asparagine Endopeptidase, Locus Ceruleus Degeneration, and Hippocampal Amyloid-β42 Accumulation.

Chronic sleep disruption (CSD), from insufficient or fragmented sleep and is an important risk factor for Alzheimer's disease (AD). Underlying mechanisms are not understood. CSD in mice results in degeneration of locus ceruleus neurons (LCn) and CA1 hippocampal neurons and increases hippocampal amyloid-β42 (Aβ42), entorhinal cortex (EC) tau phosphorylation (p-tau), and glial reactivity. LCn injury is increasingly implicated in AD pathogenesis. CSD increases NE turnover in LCn, and LCn norepinephrine (NE) metabolism activates asparagine endopeptidase (AEP), an enzyme known to cleave amyloid precursor protein (APP) and tau into neurotoxic fragments. We hypothesized that CSD would activate LCn AEP in an NE-dependent manner to induce LCn and hippocampal injury. Here, we studied LCn, hippocampal, and EC responses to CSD in mice deficient in NE [dopamine β-hydroxylase (Dbh)-/-] and control male and female mice, using a model of chronic fragmentation of sleep (CFS). Sleep was equally fragmented in Dbh -/- and control male and female mice, yet only Dbh -/- mice conferred resistance to CFS loss of LCn, LCn p-tau, and LCn AEP upregulation and activation as evidenced by an increase in AEP-cleaved APP and tau fragments. Absence of NE also prevented a CFS increase in hippocampal AEP-APP and Aβ42 but did not prevent CFS-increased AEP-tau and p-tau in the EC. Collectively, this work demonstrates AEP activation by CFS, establishes key roles for NE in both CFS degeneration of LCn neurons and CFS promotion of forebrain Aβ accumulation, and, thereby, identifies a key molecular link between CSD and specific AD neural injuries.

Coenzyme Q10 eyedrops conjugated with vitamin E TPGS alleviate neurodegeneration and mitochondrial dysfunction in the diabetic mouse retina.

Diabetic retinopathy (DR) is a leading cause of blindness and vision impairment worldwide and represents one of the most common complications among diabetic patients. Current treatment modalities for DR, including laser photocoagulation, intravitreal injection of corticosteroid, and anti-vascular endothelial growth factor (VEGF) agents, target primarily vascular lesions. However, these approaches are invasive and have several limitations, such as potential loss of visual function, retinal scars and cataract formation, and increased risk of ocular hypertension, vitreous hemorrhage, retinal detachment, and intraocular inflammation. Recent studies have suggested mitochondrial dysfunction as a pivotal factor leading to both the vascular and neural damage in DR. Given that Coenzyme Q10 (CoQ10) is a proven mitochondrial stabilizer with antioxidative properties, this study investigated the effect of CoQ10 eyedrops [in conjunction with vitamin E d-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS)] on DR-induced neurodegeneration using a type 2 diabetes mouse model (C57BLKsJ-db/db mice). Utilizing a comprehensive electroretinography protocol, supported by immunohistochemistry, our results revealed that topical application of CoQ10 eyedrops conjugated with vitamin E TPGS produced a neuroprotective effect against diabetic-induced neurodegeneration by preserving the function and histology of various retinal neural cell types. Compared to the control group, mice treated with CoQ10 exhibited thicker outer and inner nuclear layers, higher densities of photoreceptor, cone cell, and rod-bipolar cell dendritic boutons, and reduced glial reactivity and microglial cell density. Additionally, the CoQ10 treatment significantly alleviated retinal levels of MMP-9 and enhanced mitochondrial function. These findings provide further insight into the role of mitochondrial dysfunction in the development of DR and suggest CoQ10 eyedrops, conjugated with vitamin E TPGS, as a potential complementary therapy for DR-related neuropathy.

Montelukast improves disease outcome in SOD1G93A female mice by counteracting oligodendrocyte dysfunction and aberrant glial reactivity.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron (MN) loss and consequent muscle atrophy, for which no effective therapies are available. Recent findings reveal that disease progression is fuelled by early aberrant neuroinflammation and the loss of oligodendrocytes with neuroprotective and remyelinating properties. On this basis, pharmacological interventions capable of restoring a pro-regenerative local milieu and re-establish proper oligodendrocyte functions may be beneficial. Here, we evaluated the in vivo therapeutic effects of montelukast (MTK), an antagonist of the oligodendroglial G protein-coupled receptor 17 (GPR17) and of cysteinyl-leukotriene receptor 1 (CysLT1R) receptors on microglia and astrocytes, in the SOD1G93A ALS mouse model. We chronically treated SOD1G93A mice with MTK, starting from the early symptomatic disease stage. Disease progression was assessed by behavioural and immunohistochemical approaches. Oral MTK treatment significantly extended survival probability, delayed body weight loss and ameliorated motor functionalityonly in female SOD1G93A mice. Noteworthy, MTK significantly restored oligodendrocyte maturation and induced significant changes in the reactive phenotype and morphological features of microglia/macrophages and astrocytes in the spinal cord of female SOD1G93A mice, suggesting enhanced pro-regenerative functions. Importantly, concomitant MN preservation has been detected after MTK administration. No beneficial effects were observed in male mice, highlighting a sex-based difference in the protective activity of MTK. Our results provide the first preclinical evidence indicating that repurposing of MTK, a safe and marketed anti-asthmatic drug, may be a promising sex-specific strategy for personalized ALS treatment.

Ependymal cells undergo astrocyte-like reactivity in response to neuroinflammation.

Ependymal cells form a specialized brain-cerebrospinal fluid (CSF) interface and regulate local CSF microcirculation. It is becoming increasingly recognized that ependymal cells assume a reactive state in response to aging and disease, including conditions involving hypoxia, hydrocephalus, neurodegeneration, and neuroinflammation. Yet what transcriptional signatures govern these reactive states and whether this reactivity shares any similarities with classical descriptions of glial reactivity (i.e., in astrocytes) remain largely unexplored. Using single-cell transcriptomics, we interrogated this phenomenon by directly comparing the reactive ependymal cell transcriptome to the reactive astrocyte transcriptome using a well-established model of autoimmune-mediated neuroinflammation (MOG35-55 EAE). In doing so, we unveiled core glial reactivity-associated genes that defined the reactive ependymal cell and astrocyte response to MOG35-55 EAE. Interestingly, known reactive astrocyte genes from other CNS injury/disease contexts were also up-regulated by MOG35-55 EAE ependymal cells, suggesting that this state may be conserved in response to a variety of pathologies. We were also able to recapitulate features of the reactive ependymal cell state acutely using a classic neuroinflammatory cocktail (IFNγ/LPS) both invitro and invivo. Taken together, by comparing reactive ependymal cells and astrocytes, we identified a conserved signature underlying glial reactivity that was present in several neuroinflammatory contexts. Future work will explore the mechanisms driving ependymal reactivity and assess downstream functional consequences.

Docosahexaenoic Acid (DHA), Vitamin D3, and Probiotics Supplementation Improve Memory, Glial Reactivity, and Oxidative Stress Biomarkers in an Aluminum-Induced Cognitive Impairment Rat Model.

Globally, the rise in neurodegenerative issues in tandem with shifts in lifestyle and aging population has prompted a search for effective interventions. Nutraceutical compounds have emerged as promising agents for addressing these challenges. This 60-day study on an aluminum-induced cognitive impairment rat model assessed three compounds and their combinations: probiotics (Prob, Lactobacillus plantarum [5 × 1010 CFU/day], and Lactobacillus acidophilus [5 × 1010 CFU/day]), docosahexaenoic acid (DHA, 23.8 mg/day), and vitamin D3 (VD3, 150 IU/day). Behavioral outcomes were evaluated by using the Morris water maze and novel object recognition tests. Glial activation was assessed through immunofluorescence analysis of GFAP/Iba1, and oxidative stress markers in brain tissue were determined by measuring the levels of Malondialdehyde (MDA) and Superoxide dismutase (SOD). The results demonstrated a progressive improvement in the learning and memory capacity. The aluminum group exhibited the poorest performance in the behavioral test, enhanced GFAP/Iba1 activation, and elevated levels of oxidative stress markers. Conversely, the DHA + Prob + VD3 treatment demonstrated the best performance in the Morris water maze. The combination of DHA + Prob + VD3 exhibited superior performance in the Morris water maze, accompanied by reduced levels of GFAP/Iba1 activation in DG/CA1 brain regions. Furthermore, DHA + Prob supplementation showed lower GFAP/Iba1 activation in the CA3 region and enhanced antioxidant activity. In summary, supplementing various nutraceutical combinations, including DHA, VD3, and Prob, displayed notable benefits against aluminum-induced cognitive impairment. These benefits encompassed memory enhancement, diminished MDA concentration, increased SOD activity, and reduced glial activation, as indicated by GFAP/Iba1 markers.

Toxicologic Pathology Forum: Apoptosis/Single Cell Necrosis as a Possible Procedural Effect in Primate Brain Following Ice-Cold Saline Perfusion.

Nonclinical studies of test articles (TAs) in nonhuman primates are often designed to assess both biodistribution and toxicity. For this purpose, studies commonly use intravenous perfusion of ice-cold (2°C-8°C) saline to facilitate measurements of TA-associated nucleic acids and proteins, after which tissues undergo later fixation by immersion for histological processing and microscopic evaluation. Intriguingly, minimal apoptosis/single cell necrosis (A/SCN) of randomly distributed neural cells is evident in the cerebral cortex and less often the hippocampus in animals from all groups, including vehicle-treated controls. Affected cells exhibit end-stage features such as cytoplasmic hypereosinophilia, nuclear condensation or fragmentation, and shape distortions, so their lineage(s) generally cannot be defined; classical apoptotic bodies are exceedingly rare. In addition, A/SCN is not accompanied by glial reactions, leukocyte infiltration/inflammation, or other parenchymal changes. The severity is minimal in controls but may be slightly exacerbated (to mild) by TA that accumulate in neural cells. One plausible hypothesis explaining this A/SCN exacerbation is that cold shock (perhaps complicated by concurrent tissue acidity and hypoxia) drives still-viable but TA-stressed cells to launch a self-directed death program. Taken together, these observations indicate that A/SCN in brain processed by cold saline perfusion with delayed immersion fixation represents a procedural artifact and not a TA-related lesion.

Structural, Functional, and Genetic Changes Surrounding Electrodes Implanted in the Brain.

Implantable neurotechnology enables monitoring and stimulating of the brain signals responsible for performing cognitive, motor, and sensory tasks. Electrode arrays implanted in the brain are increasingly used in the clinic to treat a variety of sources of neurological diseases and injuries. However, the implantation of a foreign body typically initiates a tissue response characterized by physical disruption of vasculature and the neuropil as well as the initiation of inflammation and the induction of reactive glial states. Likewise, electrical stimulation can induce damage to the surrounding tissue depending on the intensity and waveform parameters of the applied stimulus. These phenomena, in turn, are likely influenced by the surface chemistry and characteristics of the materials employed, but further information is needed to effectively link the biological responses observed to specific aspects of device design. In order to inform improved design of implantable neurotechnology, we are investigating the basic science principles governing device-tissue integration. We are employing multiple techniques to characterize the structural, functional, and genetic changes that occur in the cells surrounding implanted electrodes. First, we have developed a new "device-in-slice" technique to capture chronically implanted electrodes within thick slices of live rat brain tissue for interrogation with single-cell electrophysiology and two-photon imaging techniques. Our data revealed several new observations of tissue remodeling surrounding devices: (a) there was significant disruption of dendritic arbors in neurons near implants, where losses were driven asymmetrically on the implant-facing side. (b) There was a significant loss of dendritic spine densities in neurons near implants, with a shift toward more immature (nonfunctional) morphologies. (c) There was a reduction in excitatory neurotransmission surrounding implants, as evidenced by a reduction in the frequency of excitatory postsynaptic currents (EPSCs). Lastly, (d) there were changes in the electrophysiological underpinnings of neuronal spiking regularity. In parallel, we initiated new studies to explore changes in gene expression surrounding devices through spatial transcriptomics, which we applied to both recording and stimulating arrays. We found that (a) device implantation is associated with the induction of hundreds of genes associated with neuroinflammation, glial reactivity, oligodendrocyte function, and cellular metabolism and (b) electrical stimulation induces gene expression associated with damage or plasticity in a manner dependent upon the intensity of the applied stimulus. We are currently developing computational analysis tools to distill biomarkers of device-tissue interactions from large transcriptomics data sets. These results improve the current understanding of the biological response to electrodes implanted in the brain while producing new biomarkers for benchmarking the effects of novel electrode designs on responses. As the next generation of neurotechnology is developed, it will be increasingly important to understand the influence of novel materials, surface chemistries, and implant architectures on device performance as well as the relationship with the induction of specific cellular signaling pathways.

Dose-Related Side Effects of Intravitreal Injections of Humanized Anti-Vascular Endothelial Growth Factor in Rats: Glial Cell Reactivity and Retinal Ganglion Cell Loss.

In a previous study, we documented that the Intravitreal injections (IVIs) of bevacizumab in rats caused a retinal inflammatory response. We now study whether the IVI of other humanized anti-VEGF: ranibizumab and aflibercept also cause an inflammatory reaction in the rat retina and if it depends on the dose administered. Finally, we study whether this reaction affects retinal ganglion cell (RGC) survival. Albino Sprague-Dawley rats received a single IVI of 5 µL of PBS or ranibizumab or aflibercept at the concentration used in clinical practice (10 µg/µL or 40 µg/µL) or at a lower concentration (0.38 µg/µL and 1.5 µg/µL) calculated to obtain within the rat eye the same concentration as in the human eye in clinical practice. Others received a single 5 µL IVI of a polyclonal goat anti-rat VEGF (0.015 µg/µL) or of vehicle (PBS). Animals were processed 7days or 1month later. Retinal whole mounts were immunolabeled for the detection of microglial, macroglial, RGCs, and intrinsically photosensitive RGCs (ipRGCs). Fluorescence and confocal microscopy were used to examine retinal changes, and RGCs and ipRGCs were quantified automatically or semiautomatically, respectively. All the injected substances including the PBS induced detectable side effects, namely, retinal microglial cell activation and retinal astrocyte hypertrophy. However, there was a greater microglial and macroglial response when the higher concentrations of ranibizumab and aflibercept were injected than when PBS, the antibody anti-rat VEGF and the lower concentrations of ranibizumab or aflibercept were injected. The higher concentration of ranibizumab and aflibercept resulted also in significant RGC death, but did not cause appreciable ipRGC death. The IVI of all the substances had some retinal inflammatory effects. The IVI of humanized anti-VEGF to rats at high doses cause important side effects: severe inflammation and RGC death, but not ipRGC death.

209 Transcriptomic Analysis of the Post-mortem Brain in Intracranial Atherosclerosis Implicates Interferon Signaling

INTRODUCTION: Intracranial atherosclerotic stenosis (ICAS) is a common cause of ischemic stroke. Stroke patients manifesting symptomatic ICAS often have poor prognoses, including worsened functional outcome, increased morbidity, and mortality. Despite risk factor management, ICAS exhibits a nonlinear rise in incidence with age, with an increase in unstable lipid-rich plaques. Understanding mechanisms of ICAS is crucial to improve clinical outcomes and reduce stroke incidence. Previous studies have demonstrated that intracranial arteries demonstrate different histopathologic profiles compared to extracranial arteries, likely lowering their risk of atherosclerosis. However, these studies are limited to healthy intracranial arteries. Comprehensive multiomic data examining diseased intracranial arteries are limited. METHODS: We performed bulk transcriptomic analysis in 4 tissues in a post-mortem brain dataset (N=304), with 34 patients with cerebral atherosclerosis confirmed via autopsy, 90 patients with peripheral atherosclerosis, and 180 controls. Cell type deconvolution was conducted to identify differential expression signatures in 7 neuronal and glial subtypes. To examine interferon response further in glial cells, we generated human induced pluripotent stem cell (hiPSC)-derived astrocytes treated with 3 doses of interferon and performed transcriptomic analysis. RESULTS: Cerebral atherosclerosis was significantly (pathway enrichment p<10e-9) associated with interferon signaling compared to peripheral atherosclerosis and controls. Glial cells particularly expressed patterns associated with cerebral atherosclerosis. Astrocytes, oligodendrocytes, excitatory neurons, and endothelial cells were most impacted. In hiPSC-derived astrocytes treated with interferon, we identified upregulation of interferon-inducible genes matching those found in intracranial atherosclerosis in the post-mortem brain, implicating glial reactivity to interferon-related stress. CONCLUSIONS: Our study implicates interferon signaling as critical within the development of cerebral atherosclerosis. Protection of the intracranial arteries from atherosclerosis may occur due to reduced expression of interferon-inducible genes. Targeted treatment of cerebral atherosclerosis should consider interferon-signaling modulators.

THE EFFECT OF GABA-BENZODIAZEPINE RECEPTOR COMPLEX MODULATORS (MPTD-01 AND BS 34-20) ON THE CEREBRAL CORTEX AFTER EXPERIMENTAL BRAIN INJURY

Background. Traumatic brain injury (TBI) is a major medical, social, and public health problem, In the military population the TBI incidence also remains high due to blunt head trauma and blast injuries. Considering the substantial TBI burden on society, including possible postraumatic epilepsy onset and other comorbidities the search for new treatment methods, including drug design with the identification of new molecules, is highly relevant.
 Aim: The study aimed to evaluate the effect of GABA-benzodiazepine receptor complex modulators (hydrogenated 2,3-benzodiazepines MPTD-01 та BS 34-20) on rat cerebral cortex after traumatic brain injury
 Materials and methods. The experiment was carried out on male Wistar rats. To obtain traumatic brain injury we used the weight drop model. Based on the received treatment, the Rats were divided into intact, placebo (II), and MPTD-01 (III) and BS 34-20 (IV) groups. The cerebral cortex in the impact zone was harvested for examination. The light microscopy was performed on 3, 7, 14, and 21 days after injury.
 Results. The observed histological picture of the changes in the cerebral cortex, especially in the II group is similar to those, described by other research papers as mild- to severe traumatic brain injury. The reproduction of the blunt trauma model leads to a series of typical changes that replace each other and can be characterized as alteration, edema, phase of cellular reactions, and repair. Unlike the placebo group, the III and IV experimental groups (GABA-benzodiazepine receptor complex modulators administration) cerebral cortex demonstrated a smoothing of the swelling phase and its reduction, a shift in the time phase of cellular reactions to a later time. In the BS 34-20 group, minimal edema was observed on the 21st day of the experiment.
 Conclusion. Such morphological changes can be considered a neuroprotective effect, however, to fully characterize the effects of the GABA-benzodiazepine receptor complex modulators, glial reactions and neuron-glial interactions should be investigated.

Pyroptosis-mediator GSDMD promotes Parkinson’s disease pathology via microglial activation and dopaminergic neuronal death

GSDMD-mediated pyroptosis occurs in the nigrostriatal pathway in Parkinson’s disease animals, yet the role of GSDMD in neuroinflammation and death of dopaminergic neurons in Parkinson’s disease remains elusive. Here, our in vivo and in vitro studies demonstrated that GSDMD, as a pyroptosis executor, contributed to glial reaction and death of dopaminergic neurons across different Parkinson’s disease models. The ablation of the Gsdmd attenuated Parkinson’s disease damage by reducing dopaminergic neuronal death, microglial activation, and detrimental transformation. Disulfiram, an inhibitor blocking GSDMD pore formation, efficiently curtailed pyroptosis, thereby lessening the pathology of Parkinson’s disease. Additionally, a modification in GSDMD was identified in the blood of Parkinson’s disease patients in contrast to healthy subjects. Therefore, the detected alteration in GSDMD within the blood of Parkinson’s disease patients and the protective impact of disulfiram could be promising for the diagnostic and therapeutic approaches against Parkinson’s disease.

Involvement of CB1 and CB2 receptors in neuroprotective effects of cannabinoids in experimental TDP-43 related frontotemporal dementia using male mice

BackgroundThe elevation of endocannabinoid levels through inhibiting their degradation afforded neuroprotection in CaMKIIα-TDP-43 mice, a conditional transgenic model of frontotemporal dementia. However, which cannabinoid receptors are mediating these benefits is still pending to be elucidated. MethodsWe have investigated the involvement of the CB1 and the CB2 receptor using chronic treatments with selective ligands in CaMKIIα-TDP-43 mice, analysis of their cognitive deterioration with the Novel Object Recognition test, and immunostaining for neuronal and glial markers in two areas of interest in frontotemporal dementia. ResultsOur results confirmed the therapeutic value of activating either the CB1 or the CB2 receptor, with improvements in the animal performance in the Novel Object Recognition test, preservation of pyramidal neurons, in particular in the medial prefrontal cortex, and attenuation of glial reactivity, in particular in the hippocampus. In addition, the activation of both CB1 and CB2 receptors reduced the elevated levels of TDP-43 in the medial prefrontal cortex of CaMKIIα-TDP-43 mice, an effect exerted by mechanisms that are currently under investigation. ConclusionsThese data reinforce the notion that the activation of CB1 and CB2 receptors may represent a promising therapy against TDP-43-induced neuropathology in frontotemporal dementia. Future studies will have to confirm these benefits, in particular with one of the selective CB2 agonists used here, which has been thoroughly characterized for clinical development.

Chronic evoked seizures in young pre-symptomatic APP/PS1 mice induce serotonin changes and accelerate onset of Alzheimer’s disease-related neuropathology

ObjectiveHyperexcitability is intimately linked to Alzheimer's disease (AD) pathology, but the precise timing and contributions of neuronal hyperexcitability to disease progression is unclear. Seizure induction in rodent AD models can uncover new therapeutic targets. Further, investigator-evoked seizures can directly establish how hyperexcitability and AD-associated risk factors influence neuropathological hallmarks and disease course at presymptomatic stages. MethodsCorneal kindling is a well-characterized preclinical epilepsy model that allows for precise control of seizure history to pair to subsequent behavioral assessments. 2–3-month-old APP/PS1, PSEN2-N141I, and transgenic control male and female mice were thus sham or corneal kindled for 2 weeks. Seizure-induced changes in glia, serotonin pathway proteins, and amyloid β levels in hippocampus and prefrontal cortex were quantified. ResultsAPP/PS1 females were more susceptible to corneal kindling. However, regardless of sex, APP/PS1 mice experienced extensive seizure-induced mortality versus kindled Tg- controls. PSEN2-N141I mice were not negatively affected by corneal kindling. Mortality correlated with a marked downregulation of hippocampal tryptophan hydroxylase 2 and monoamine oxidase A protein expression versus controls; these changes were not detected in PSEN2-N141I mice. Kindled APP/PS1 mice also exhibited soluble amyloid β upregulation and glial reactivity without plaque deposition. SignificanceEvoked convulsive seizures and neuronal hyperexcitability in pre-symptomatic APP/PS1 mice promoted premature mortality without pathological Aβ plaque deposition, whereas PSEN2-N141I mice were unaffected. Disruptions in serotonin pathway metabolism in APP/PS1 mice was associated with increased glial reactivity without Aβ plaque deposition, demonstrating that neuronal hyperexcitability in early AD causes pathological Aβ overexpression and worsens long-term outcomes through a serotonin-related mechanism.

Glial reactivity in a mouse model of beta-amyloid deposition assessed by PET imaging of P2X7 receptor and TSPO using [11C]SMW139 and [18F]F-DPA

BackgroundP2X7 receptor has emerged as a potentially superior PET imaging marker to TSPO, the gold standard for imaging glial reactivity. [11C]SMW139 is the most recently developed radiotracer to image P2X7 receptor. The aim of this study was to image reactive glia in the APP/PS1-21 transgenic (TG) mouse model of Aβ deposition longitudinally using [11C]SMW139 targeting P2X7 receptor and to compare tracer uptake to that of [18F]F-DPA targeting TSPO at the final imaging time point. TG and wild type (WT) mice underwent longitudinal in vivo PET imaging using [11C]SMW139 at 5, 8, 11, and 14 months, followed by [18F]F-DPA PET scan only at 14 months. In vivo imaging results were verified by ex vivo brain autoradiography, immunohistochemical staining, and analysis of [11C]SMW139 unmetabolized fraction in TG and WT mice.ResultsLongitudinal change in [11C]SMW139 standardized uptake values (SUVs) showed no statistically significant increase in the neocortex and hippocampus of TG or WT mice, which was consistent with findings from ex vivo brain autoradiography. Significantly higher [18F]F-DPA SUVs were observed in brain regions of TG compared to WT mice. Quantified P2X7-positive staining in the cortex and thalamus of TG mice showed a minor increase in receptor expression with ageing, while TSPO-positive staining in the same regions showed a more robust increase in expression in TG mice as they aged. [11C]SMW139 was rapidly metabolized in mice, with 33% of unmetabolized fraction in plasma and 29% in brain homogenates 30 min after injection.Conclusions[11C]SMW139, which has a lower affinity for the rodent P2X7 receptor than the human version of the receptor, was unable to image the low expression of P2X7 receptor in the APP/PS1-21 mouse model. Additionally, the rapid metabolism of [11C]SMW139 in mice and the presence of several brain-penetrating radiometabolites significantly impacted the analysis of in vivo PET signal of the tracer. Finally, [18F]F-DPA targeting TSPO was more suitable for imaging reactive glia and neuroinflammatory processes in the APP/PS1-21 mouse model, based on the findings presented in this study and previous studies with this mouse model.

The Effects of the S1P Receptor Agonist Fingolimod (FTY720) on Central and Peripheral Myelin in Twitcher Mice.

Krabbe's disease (KD) is caused by mutations in the lysosomal enzyme galactocerebrosidase and is associated with psychosine toxicity. The sphingosine 1-phosphate receptor (S1PR) agonist fingolimod (FTY720) attenuates psychosine-induced cell death of human astrocytes, demyelination in cerebellar slices, as well as demyelination in the central nervous system of twitcher mice. Psychosine also accumulates in the peripheral nervous system in twitcher mice; however, effects of fingolimod on this peripheral myelin have not been examined. The aim of this study was to investigate the effects of fingolimod administration on peripheral and central markers of myelination. Here, we report that fingolimod administration (1 mg/kg/day) from postnatal day 5 (PND) onwards did not alter peripheral demyelination in the sciatic nerve of twitcher mice, despite significantly reducing myelin debris, glial reactivity, and neuronal damage in the cerebellum. We also find fingolimod administration improves twitching and mobility scores in twitcher mice. Importantly, we find that fingolimod significantly increases the lifespan of twitcher mice by approximately 5 days. These findings suggest differential effects of fingolimod on peripheral and central neuropathy in twitcher mice, which may explain its modest efficacy on behavior and lifespan.

Embryonic stem cells overexpressing high molecular weight FGF2 isoform enhance recovery of pre-ganglionic spinal root lesion in combination with fibrin biopolymer mediated root repair

BackgroundSpinal ventral root avulsion results in massive motoneuron degeneration with poor prognosis and high costs. In this study, we compared different isoforms of basic fibroblast growth factor 2 (FGF2), overexpressed in stably transfected Human embryonic stem cells (hESCs), following motor root avulsion and repair with a heterologous fibrin biopolymer (HFB).MethodsIn the present work, hESCs bioengineered to overexpress 18, 23, and 31 kD isoforms of FGF2, were used in combination with reimplantation of the avulsed roots using HFB. Statistical analysis was conducted using GraphPad Prism software with one-way or two-way ANOVA, followed by Tukey’s or Dunnett’s multiple comparison tests. Significance was set at *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001.ResultsFor the first set of experiments, rats underwent avulsion of the ventral roots with local administration of HFB and engraftment of hESCs expressing the above-mentioned FGF2 isoforms. Analysis of motoneuron survival, glial reaction, and synaptic coverage, two weeks after the lesion, indicated that therapy with hESCs overexpressing 31 kD FGF2 was the most effective. Consequently, the second set of experiments was performed with that isoform, so that ventral root avulsion was followed by direct spinal cord reimplantation. Motoneuron survival, glial reaction, synaptic coverage, and gene expression were analyzed 2 weeks post-lesion; while the functional recovery was evaluated by the walking track test and von Frey test for 12 weeks. We showed that engraftment of hESCs led to significant neuroprotection, coupled with immunomodulation, attenuation of astrogliosis, and preservation of inputs to the rescued motoneurons. Behaviorally, the 31 kD FGF2 - hESC therapy enhanced both motor and sensory recovery.ConclusionTransgenic hESCs were an effective delivery platform for neurotrophic factors, rescuing axotomized motoneurons and modulating glial response after proximal spinal cord root injury, while the 31 kD isoform of FGF2 showed superior regenerative properties over other isoforms in addition to the significant functional recovery.

CDDO regulates central and peripheral sensitization to attenuate post-herpetic neuralgia by targeting TRPV1/PKC-δ/p-Akt signals.

Postherpetic neuralgia (PHN) is a notorious neuropathic pain featuring persistent profound mechanical hyperalgesia with significant negative impact on patients' life quality. CDDO can regulate inflammatory response and programmed cell death. Its derivative also protects neurons from damages by modulating microglia activities. As a consequence of central and peripheral sensitization, applying neural blocks may benefit to minimize the risk of PHN. This study aimed to explore whether CDDO could generate analgesic action in a PHN-rats' model. The behavioural test was determined by calibrated forceps testing. The number of apoptotic neurons and degree of glial cell reaction were assessed by immunofluorescence assay. Activation of PKC-δ and the phosphorylation of Akt were measured by western blots. CDDO improved PHN by decreasing TRPV1-positive nociceptive neurons, the apoptotic neurons, and reversed glial cell reaction in adult rats. It also suppressed the enhanced PKC-δ and p-Akt signalling in the sciatic nerve, dorsal root ganglia (DRG) and spinal dorsal horn. Our research is the promising report demonstrating the analgesic and neuroprotective action of CDDO in a PHN-rat's model by regulating central and peripheral sensitization targeting TRPV1, PKC-δ and p-Akt. It also is the first study to elucidate the role of oligodendrocyte in PHN.

Mesenchymal Stem Cell Engagement Modulates Neuroma Microenviroment in Rats and Humans and Prevents Postamputation Pain

Postamputation pain is currently managed unsatisfactorily with neuron-targeted pharmacological and interventional therapies. Non-neuronal pain mechanisms have emerged as crucial factors in the development and persistence of postamputation pain. Consequently, these mechanisms offer exciting prospects as innovative therapeutic targets. We examined the hypothesis that engaging mesenchymal stem cells (MSCs) would foster local neuroimmune interactions, leading to a potential reduction in postamputation pain. We utilized an ex vivo neuroma model from a phantom limb pain patient to uncover that the oligodeoxynucleotide IMT504 engaged human primary MSCs to promote an anti-inflammatory microenvironment. Reverse translation experiments recapitulated these effects. Thus, in an in vivo rat model, IMT504 exhibited strong efficacy in preventing autotomy (self-mutilation) behaviors. This effect was linked to a substantial accumulation of MSCs in the neuroma and associated dorsal root ganglia and the establishment of an anti-inflammatory phenotype in these compartments. Centrally, this intervention reduced glial reactivity in the dorsal horn spinal cord, demonstrating diminished nociceptive activity. Accordingly, the exogenous systemic administration of MSCs phenocopied the behavioral effects of IMT504. Our findings underscore the mechanistic relevance of MSCs and the translational therapeutic potential of IMT504 to engage non-neuronal cells for the prevention of postamputation pain. PerspectiveThe present study suggests that IMT504-dependent recruitment of endogenous MSCs within severely injured nerves may prevent post-amputation pain by modifying the inflammatory scenario at relevant sites in the pain pathway. Reinforcing data in rat and human tissues supports the potential therapeutic value of IMT504 in patients suffering postamputation pain.

Histological Characterisation of a Sheep Model of Mild Traumatic Brain Injury: A Pilot Study.

Large animal models of mild traumatic brain injury (mTBI) are needed to elucidate the pathophysiology of mechanical insult to a gyrencephalic brain. Sheep (ovis aries) are an attractive model for mTBI because of their neuroanatomical similarity to humans; however, few histological studies of sheep mTBI models have been conducted. We previously developed a sheep mTBI model to pilot methods for investigating the mechanical properties of brain tissue after injury. Here, we sought to histologically characterize the cortex under the impact site in this model. Three animals received a closed skull mTBI with unconstrained head motion, delivered with an impact stunner, and 3 sham animals were anesthetized but did not receive an impact. Magnetic resonance imaging (MRI) of the brain was performed before and after the impact and revealed variable degrees of damage to the skull and brain. Fluorescent immunohistochemistry revealed regions of hemorrhage in the cortex underlying the impact site in 2 of 3 mTBI sheep, the amount of which correlated with the degree of damage observed on the post-impact MRI scans. Labeling for microtubule-associated protein 2 and neuronal nuclear protein revealed changes in cellular anatomy, but, unexpectedly, glial fibrillary acidic protein and ionized calcium-binding adaptor molecule 1 labeling were relatively unchanged compared to sham animals. Our findings provide preliminary evidence of vascular and neuronal damage with limited glial reactivity and highlight the need for further in-depth histological assessment of large animal mTBI models.

Reactive gliosis in traumatic brain injury: a comprehensive review.

Traumatic brain injury (TBI) is one of the most common pathological conditions impacting the central nervous system (CNS). A neurological deficit associated with TBI results from a complex of pathogenetic mechanisms including glutamate excitotoxicity, inflammation, demyelination, programmed cell death, or the development of edema. The critical components contributing to CNS response, damage control, and regeneration after TBI are glial cells-in reaction to tissue damage, their activation, hypertrophy, and proliferation occur, followed by the formation of a glial scar. The glial scar creates a barrier in damaged tissue and helps protect the CNS in the acute phase post-injury. However, this process prevents complete tissue recovery in the late/chronic phase by producing permanent scarring, which significantly impacts brain function. Various glial cell types participate in the scar formation, but this process is mostly attributed to reactive astrocytes and microglia, which play important roles in several brain pathologies. Novel technologies including whole-genome transcriptomic and epigenomic analyses, and unbiased proteomics, show that both astrocytes and microglia represent groups of heterogenic cell subpopulations with different genomic and functional characteristics, that are responsible for their role in neurodegeneration, neuroprotection and regeneration. Depending on the representation of distinct glia subpopulations, the tissue damage as well as the regenerative processes or delayed neurodegeneration after TBI may thus differ in nearby or remote areas or in different brain structures. This review summarizes TBI as a complex process, where the resultant effect is severity-, region- and time-dependent and determined by the model of the CNS injury and the distance of the explored area from the lesion site. Here, we also discuss findings concerning intercellular signaling, long-term impacts of TBI and the possibilities of novel therapeutical approaches. We believe that a comprehensive study with an emphasis on glial cells, involved in tissue post-injury processes, may be helpful for further research of TBI and be the decisive factor when choosing a TBI model.