Host Brain Research Articles

Human Stem Cell-Derived GABAergic Interneurons Establish Efferent Synapses onto Host Neurons in Rat Epileptic Hippocampus and Inhibit Spontaneous Recurrent Seizures.

Epilepsy is a complex disorder affecting the central nervous system and is characterised by spontaneously recurring seizures (SRSs). Epileptic patients undergo symptomatic pharmacological treatments, however, in 30% of cases, they are ineffective, mostly in patients with temporal lobe epilepsy. Therefore, there is a need for developing novel treatment strategies. Transplantation of cells releasing γ-aminobutyric acid (GABA) could be used to counteract the imbalance between excitation and inhibition within epileptic neuronal networks. We generated GABAergic interneuron precursors from human embryonic stem cells (hESCs) and grafted them in the hippocampi of rats developing chronic SRSs after kainic acid-induced status epilepticus. Using whole-cell patch-clamp recordings, we characterised the maturation of the grafted cells into functional GABAergic interneurons in the host brain, and we confirmed the presence of functional inhibitory synaptic connections from grafted cells onto the host neurons. Moreover, optogenetic stimulation of grafted hESC-derived interneurons reduced the rate of epileptiform discharges in vitro. We also observed decreased SRS frequency and total time spent in SRSs in these animals in vivo as compared to non-grafted controls. These data represent a proof-of-concept that hESC-derived GABAergic neurons can exert a therapeutic effect on epileptic animals presumably through establishing inhibitory synapses with host neurons.

Exploring the Impact of the Microbiome on Neuroactive Steroid Levels in Germ-Free Animals.

Steroid hormones are essential biomolecules for human physiology as they modulate the endocrine system, nervous function and behaviour. Recent studies have shown that the gut microbiota is directly involved in the production and metabolism of steroid hormones in the periphery. However, the influence of the gut microbiota on levels of steroids acting and present in the brain (i.e., neuroactive steroids) is not fully understood. Therefore, using liquid chromatography–tandem mass spectrometry, we assessed the levels of several neuroactive steroids in various brain areas and the plasma of germ-free (GF) male mice and conventionally colonized controls. The data obtained indicate an increase in allopregnanolone levels associated with a decrease in those of 5α-androstane-3α, 17β-diol (3α-diol) in the plasma of GF mice. Moreover, an increase of dihydroprogesterone and isoallopregnanolone in the hippocampus, cerebellum, and cerebral cortex was also reported. Changes in dihydrotestosterone and 3α-diol levels were also observed in the hippocampus of GF mice. In addition, an increase in dehydroepiandrosterone was associated with a decrease in testosterone levels in the hypothalamus of GF mice. Our findings suggest that the absence of microbes affects the neuroactive steroids in the periphery and the brain, supporting the evidence of a microbiota-mediated modulation of neuroendocrine pathways involved in preserving host brain functioning.

Lactobacillus plantarum DP189 prevents cognitive dysfunction in D-galactose/AlCl3 induced mouse model of Alzheimer’s disease via modulating gut microbiota and PI3K/Akt/GSK-3β signaling pathway

ABSTRACT Probiotic intervention has beneficial effects on host brain function and behavior via regulating microbiota-gut-brain axis; however, the underlying mechanism is not yet understood. Herein, we investigated that the effects of Lactobacillus plantarum DP189 (DP189) administration in preventing cognitive dysfunction and pathology of Alzheimer’s disease (AD) in D-galactose (D-gal) and AlCl3-induced AD model mice. After L. plantarum DP189 intervention for 10 weeks, we assessed cognitive behavior, neurotransmitter expression, histological changes, microbial communities, and the mechanisms underlying the disease in AD model mice. The results showed that L. plantarum DP189 intervention prevented cognitive dysfunction by behavioral test. Increased levels of serotonin, dopamine, and gamma-aminobutyric acid positively affected the pathological processes by ameliorating neuronal damage, beta-amyloid deposition, and tau pathology. L. plantarum DP189 intervention simultaneously modulated the gut microbial communities to alleviate gut dysbiosis. Moreover, L. plantarum DP189 inhibited tau hyperphosphorylation by regulating the PI3 K/Akt/GSK-3β pathway. These findings indicated that L. plantarum DP189 intervention is a promising therapeutic strategy to prevent the onset and development of AD.

Trypanosoma brucei brucei induced hypoglycaemia resulted in severe reduction in hexokinase activity in liver, kidney, brain and heart of untreated Trypanosoma brucei brucei infected mice

Trypanosoma brucei brucei depends on mammalian host glucose for survival and establishment of infection. The interference with host glucose results in disturbance of pathways for glucose metabolism and their enzymes. Therefore, this study tried to examine the relationship between untreated Trypanosoma brucei brucei infection and the host hexokinase activity in selected organs that depend on glucose for their normal biological and biochemical functions. The mice for this study were grouped into two: control (uninfected) and infected group. Baseline values for PCV, serum glucose and protein; hexokinase activity and protein concentration in the liver, kidney, heart and brain were obtained for each group. The infected group was intraperitoneally inoculation by 1 104 parasites/mice and monitor for the presence of Trypanosoma brucei brucei from the second day post infection. The same parameters were collected again on days 4 and 11 before the death of the infected group. Protein was determined by colorimetric method using Bradford reagent. PCV was analysed using a sysmex haematology analyser while hexokinase activity was measured spectrophotometrically by a coupled reaction with glucose-6-phosphate dehydrogenase at 340 nm. The result of this study showed that untreated Trypanosoma brucei brucei infection resulted in decrease in PCV, serum glucose, hexokinase activity in the liver, kidney, heart and brain but increase in serum protein. In conclusion, untreated Trypanosoma brucei brucei infection resulted in reduction in host liver, kidney, brain and heart hexokinase activity which probably deprived them of the needed energy and may be the cause of early death in untreated trypanosomiasis.

The Microbiota-Gut-Brain Axis During Heat Stress in Chickens: A Review.

Heat stress is a global issue for the poultry industries with substantial annual economic losses and threats to bird health and welfare. When chickens are exposed to high ambient temperatures, like other species they undergo multiple physiological alterations, including behavioral changes, such as cessation of feeding, initiation of a stress signaling cascade, and intestinal immune, and inflammatory responses. The brain and gut are connected and participate in bidirectional communication via the nervous and humoral systems, this network collectively known as the gut-brain axis. Moreover, heat stress not only induces hyperthermia and oxidative stress at the gut epithelium, leading to impaired permeability and then susceptibility to infection and inflammation, but also alters the composition and abundance of the microbiome. The gut microflora, primarily via bacterially derived metabolites and hormones and neurotransmitters, also communicate via similar pathways to regulate host metabolic homeostasis, health, and behavior. Thus, it stands to reason that reshaping the composition of the gut microbiota will impact intestinal health and modulate host brain circuits via multiple reinforcing and complementary mechanisms. In this review, we describe the structure and function of the microbiota-gut-brain axis, with an emphasis on physiological changes that occur in heat-stressed poultry.

Alterations of kynurenine pathway in alcohol use disorder and abstinence: a link with gut microbiota, peripheral inflammation and psychological symptoms

The gut-brain communication is mostly driven by the immune, metabolic and neural pathways which remained poorly explored in patients with alcohol use disorder (AUD). The metabolites arising from the tryptophan-kynurenine pathway have gained considerable attention since they are at the interface between intestinal bacteria, host immune response and brain functions. This study described the circulating levels of kynurenine metabolites in AUD patients, at the onset (T1) and end (T2) of a 3-week detoxification program, and tested correlations between those metabolites and inflammatory markers, the gut microbiota and the psychological symptoms. Increased concentration of the neurotoxic metabolite quinolinic acid (QUIN) and decreased levels of the neuroprotector metabolite kynurenic acid (KYNA) which both modulate glutamatergic neurotransmission were observed in AUD patients, particularly at T2. The inflammatory marker hsCRP was associated with several metabolic ratios of the kynurenine pathway. Tryptophan, KYNA and QUIN were correlated with depression, alcohol craving and reaction time, respectively. Analysis of gut microbiota revealed that bacteria known as short-chain fatty acid producers, as well as bacterial metabolites including butyrate and medium-chain fatty acids were associated with some metabolites of the tryptophan-kynurenine pathway. Targeting the glutamatergic neurotransmission through the modulation of the kynurenine pathway, by manipulating the gut microbiota, might represent an interesting alternative for modulating alcohol-related behavior.

Human iPSC-derived astrocytes transplanted into the mouse brain undergo morphological changes in response to amyloid-\u03b2 plaques

BackgroundIncreasing evidence for a direct contribution of astrocytes to neuroinflammatory and neurodegenerative processes causing Alzheimer’s disease comes from molecular and functional studies in rodent models. However, these models may not fully recapitulate human disease as human and rodent astrocytes differ considerably in morphology, functionality, and gene expression.ResultsTo address these challenges, we established an approach to study human astrocytes within the mouse brain by transplanting human induced pluripotent stem cell (hiPSC)-derived astrocyte progenitors into neonatal brains. Xenografted hiPSC-derived astrocyte progenitors differentiated into astrocytes that integrated functionally within the mouse host brain and matured in a cell-autonomous way retaining human-specific morphologies, unique features, and physiological properties. In Alzheimer´s chimeric brains, transplanted hiPSC-derived astrocytes responded to the presence of amyloid plaques undergoing morphological changes that seemed independent of the APOE allelic background.ConclusionsIn sum, we describe here a promising approach that consist of transplanting patient-derived and genetically modified astrocytes into the mouse brain to study human astrocyte pathophysiology in the context of Alzheimer´s disease.

Isolation and Purification of Self-Renewable Human Neural Stem Cells from iPSCs for Cell Therapy in Experimental Model of Ischemic Stroke.

Neural stem cell therapy has been galvanized by the discovery of pluripotent stem cells. The possibility to generate specialized central nervous system-specific differentiated cells using human somatic cells engineered to become induced pluripotent stem cells (iPSCs) was a game changer. This technology has broad applications in the field of regenerative medicine, in vitro disease modeling, targeted drug discovery, and precision medicine. Currently, iPSCs are one of the most promising cell sources amenable for commercialization and off-the-shelf neural stem cell therapy products. iPSCs exhibit a strong self-renewable ability that supports the development of a virtually unlimited source of neural cells for structural repair in neurological disorders. However, along with this strong proliferative capacity of iPSCs comes the tumorigenic potential of these cells after transplantation. Thus, the isolation and purification of a homogeneous population of human neural stem cells (hNSCs) are of paramount importance to ensure consistency in the composition of the cellular product and to avoid tumor formation in the host brain. This chapter describes the isolation, neuralization, and long-term perpetuation of hNSCs derived from iPSCs through the use of specific growth medium and the preparation of hNSCs for transplantation in an experimental model of stroke. Additionally, we will describe methods to analyze the ischemic stroke and size of grafts using magnetic resonance imaging and OsiriX software and neuroanatomical tracing procedures to study axonal remodeling after ischemic stroke and cell transplantation.

Temporal analysis the acetylation and cytokine levels of the Cronobacter muytjensii infection brain based on a bioluminescence mouse model

The present study aims to develop a bioluminescence Cronobacter muytjensii (C. muytjensii) infection animal model for use to evaluate the spatiotemporal acetylation and cytokine levels of brain. Frist, we cultured a luciferase expressing C. muytjensii that could be used for real-time monitoring in BALB/c mice. Then we performed a comparative acetylation analysis and cytokine levels analysis of the host's brain tissue. Further bioinformatic analysis studies have revealed that that some key acetylation proteins and inflammatory mediators involve in C. muytjensii infection. In this paper, the integration of bioluminescence imaging with Liquid Chromatography and Mass Spectrometry (LC-MS) based proteomics and quantitative analysis cytokine levels provide a systems-level understanding of infected brain response caused by C. muytjensii.

Postnatal prebiotic supplementation in rats affects adult anxious behaviour, hippocampus, electrophysiology, metabolomics, and gut microbiota

SummaryWe have shown previously that prebiotic (Bimuno galacto-oligosacharides, B-GOS®) administration to neonatal rats increased hippocampal NMDAR proteins. The present study has investigated the effects of postnatal B-GOS® supplementation on hippocampus-dependent behavior in young, adolescent, and adult rats and applied electrophysiological, metabolomic and metagenomic analyses to explore potential underlying mechanisms. The administration of B-GOS® to suckling, but not post-weaned, rats reduced anxious behavior until adulthood. Neonatal prebiotic intake also reduced the fast decay component of hippocampal NMDAR currents, altered age-specific trajectories of the brain, intestinal, and liver metabolomes, and reduced abundance of fecal Enterococcus and Dorea bacteria. Our data are the first to show that prebiotic administration to rats during a specific postnatal period has long-term effects on behavior and hippocampal physiology. The study also suggests that early-life prebiotic intake may affect host brain function through the reduction of stress-related gut bacteria rather than increasing the proliferation of beneficial microbes.

The Origins of the Protein Spread in Parkinson's Disease.

The Origins of the Protein Spread in Parkinson's Disease.

Beyond the neuro-immune interplay in depression: Could gut microbes be the missing link?

Accumulating evidence have positioned inflammatory signaling pathways as crucial routes by which microbes inhabiting the gastrointestinal tract (the gut microbiota) communicate with the host brain to influence behavior, with impacts on mental illnesses. In this short review, an overview of inflammatory and gut microbiota status in human depression and in rodent models of the illness are provided. Next, potential inflammatory pathways mediating the communications between the gut and the brain under stressful conditions are described. Finally, dietary interventions targeting the gut microbiota-immune-brain axis in the context of depression are briefly discussed.

Microbiota from young mice counteracts selective age-associated behavioral deficits.

The gut microbiota is increasingly recognized as an important regulator of host immunity and brain health. The aging process yields dramatic alterations in the microbiota, which is linked to poorer health and frailty in elderly populations. However, there is limited evidence for a mechanistic role of the gut microbiota in brain health and neuroimmunity during aging processes. Therefore, we conducted fecal microbiota transplantation from either young (3-4 months) or old (19-20 months) donor mice into aged recipient mice (19-20 months). Transplant of a microbiota from young donors reversed aging-associated differences in peripheral and brain immunity, as well as the hippocampal metabolome and transcriptome of aging recipient mice. Finally, the young donor-derived microbiota attenuated selective age-associated impairments in cognitive behavior when transplanted into an aged host. Our results reveal that the microbiome may be a suitable therapeutic target to promote healthy aging.

Quantitative Peptidomics of Mouse Brain After Infection With Cyst-Forming Toxoplasma gondii.

Toxoplasma gondii is an obligate intracellular parasite capable of establishing persistent infection within the host brain and inducing severe neuropathology. Peptides are important native molecules responsible for a wide range of biological functions within the central nervous system. However, peptidome profiling in host brain during T. gondii infection has never been investigated. Using a label-free peptidomics approach (LC–MS/MS), we identified a total of 2,735 endogenous peptides from acutely infected, chronically infected and control brain samples following T. gondii infection. Quantitative analysis revealed 478 and 344 significantly differentially expressed peptides (DEPs) in the acute and chronic infection stages, respectively. Functional analysis of DEPs by Gene Ontology suggested these DEPs mainly originated from cell part and took part in cellular process. We also identified three novel neuropeptides derived from the precursor protein cholecystokinin. These results demonstrated the usefulness of quantitative peptidomics in determining bioactive peptides and elucidating their functions in the regulation of behavior modification during T. gondii infection.

A diet high in sugar and fat influences neurotransmitter metabolism and then affects brain function by altering the gut microbiota

Gut microbiota (GM) metabolites can modulate the physiology of the host brain through the gut–brain axis. We wished to discover connections between the GM, neurotransmitters, and brain function using direct and indirect methods. A diet with increased amounts of sugar and fat (high-sugar and high-fat (HSHF) diet) was employed to disturb the host GM. Then, we monitored the effect on pathology, neurotransmitter metabolism, transcription, and brain circularRNAs (circRNAs) profiles in mice. Administration of a HSHF diet-induced dysbacteriosis, damaged the intestinal tract, changed the neurotransmitter metabolism in the intestine and brain, and then caused changes in brain function and circRNA profiles. The GM byproduct trimethylamine-n-oxide could degrade some circRNAs. The basal level of the GM decided the conversion rate of choline to trimethylamine-n-oxide. A change in the abundance of a single bacterial strain could influence neurotransmitter secretion. These findings suggest that a new link between metabolism, brain circRNAs, and GM. Our data could enlarge the “microbiome–transcriptome” linkage library and provide more information on the gut–brain axis. Hence, our findings could provide more information on the interplay between the gut and brain to aid the identification of potential therapeutic markers and mechanistic solutions to complex problems encountered in studies of pathology, toxicology, diet, and nutrition development.

Human stem cells harboring a suicide gene improve the\xa0safety and standardisation of neural transplants in Parkinsonian rats

Despite advancements in human pluripotent stem cells (hPSCs) differentiation protocols to generate appropriate neuronal progenitors suitable for transplantation in Parkinson’s disease, resultant grafts contain low proportions of dopamine neurons. Added to this is the tumorigenic risk associated with the potential presence of incompletely patterned, proliferative cells within grafts. Here, we utilised a hPSC line carrying a FailSafeTM suicide gene (thymidine kinase linked to cyclinD1) to selectively ablate proliferative cells in order to improve safety and purity of neural transplantation in a Parkinsonian model. The engineered FailSafeTM hPSCs demonstrated robust ventral midbrain specification in vitro, capable of forming neural grafts upon transplantation. Activation of the suicide gene within weeks after transplantation, by ganciclovir administration, resulted in significantly smaller grafts without affecting the total yield of dopamine neurons, their capacity to innervate the host brain or reverse motor deficits at six months in a rat Parkinsonian model. Within ganciclovir-treated grafts, other neuronal, glial and non-neural populations (including proliferative cells), were significantly reduced—cell types that may pose adverse or unknown influences on graft and host function. These findings demonstrate the capacity of a suicide gene-based system to improve both the standardisation and safety of hPSC-derived grafts in a rat model of Parkinsonism.

Recent Advances in the Development of Stem-Cell-Derived Dopaminergic Neuronal Transplant Therapies for Parkinson's Disease.

The last decade has seen exciting advances in the development of potential stem cell-based therapies for Parkinson's disease (PD), which have used different types of stem cells as starting material. These cells have been developed primarily to replace dopamine-producing neurons in the substantia nigra that are progressively lost in the disease process. The aim is to largely restore lost motor functions, whilst not ever being curative. We discuss cell-based strategies that will have to fulfill important criteria to become effective and competitive therapies for PD. These criteria include reproducibly producing sufficient numbers of cells with an authentic substantia nigra dopamine neuron A9 phenotype, which can integrate into the host brain after transplantation and form synapses (considered crucial for long-term functional benefits). Furthermore, it is essential that transplanted cells exhibit no, or only very low levels of, proliferation without tumor formation at the site of grafting. Cumulative research has shown that stem cell-based approaches continue to have great potential in PD, but key questions remain to be answered. Here, we review the most recent progress in research on stem cell-based dopamine neuron replacement therapy for PD and briefly discuss what the immediate future might hold. © 2021 International Parkinson and Movement Disorder Society.

3D Whole-Brain Imaging Approaches to Study Brain Tumors.

Simple SummaryBrain tumors integrate into the brain and consist of tumor cells with different molecular alterations. During brain tumor pathogenesis, a variety of cell types surround the tumors to either inhibit or promote tumor growth. These cells are collectively referred to as the tumor microenvironment. Three-dimensional and/or longitudinal visualization approaches are needed to understand the growth of these tumors in time and space. In this review, we present three imaging modalities that are suitable or that can be adapted to study the volumetric distribution of malignant or tumor-associated cells in the brain. In addition, we highlight the potential clinical utility of some of the microscopy approaches for brain tumors using exemplars from solid tumors.Although our understanding of the two-dimensional state of brain tumors has greatly expanded, relatively little is known about their spatial structures. The interactions between tumor cells and the tumor microenvironment (TME) occur in a three-dimensional (3D) space. This volumetric distribution is important for elucidating tumor biology and predicting and monitoring response to therapy. While static 2D imaging modalities have been critical to our understanding of these tumors, studies using 3D imaging modalities are needed to understand how malignant cells co-opt the host brain. Here we summarize the preclinical utility of in vivo imaging using two-photon microscopy in brain tumors and present ex vivo approaches (light-sheet fluorescence microscopy and serial two-photon tomography) and highlight their current and potential utility in neuro-oncology using data from solid tumors or pathological brain as examples.

Abstract P815: Decoding the Cross-Talk Between Grafted Neural Stem Cells and Host Brain to Predict the Molecular Mechanisms of Stem Cell-Induced Functional Recovery After Stroke

Stroke is a leading cause of long-term disability and death in the united states. The development of new therapies for stroke are sorely needed. There is great hope that stem cell therapy will create a paradigm shift in the treatment of stroke patients. A barrier to ensuring clinical success of stem cell therapy is the paucity of understanding of the mechanisms by which stem cells exert their beneficial effects. Using a novel mRNA purification method, we identified 50 genes encoding extracellular space proteins, expressed by human neural stem cells (hNSCs) whose expression positively correlated with functional recovery. In this study, we focus on one of the paracrine factors from grafted hNSCs that correlated best with functional recovery, to investigate its therapeutic potential in promoting recovery after stroke. Male nude rats underwent stroke using the distal middle cerebral artery occlusion (dMCAo) model. One week following stroke, osmotic pumps were prepared and loaded with recombinant MTN-2. The osmotic pumps were inserted into the peri-infarct area and infused recombinant MTN-2 for 5 days. Post-stroke, animals were assessed for functional recovery for 5 weeks using both the Montoya staircase test and the whisker-paw reflex test to assess for forelimb function, dexterity, side bias, and placing deficits. After 5 weeks, brain tissue was isolated to assess glial cell morphology. Brain sections were stained with GFAP and IBA1 to visualize astrocytes and microglia, respectively. Confocal images were processed and analyzed using the Bitplane Imaris image analysis software. Output measurements of number of cells/mm2, cell volume, cell branching, and process length and thickness were obtained to characterize the changes in astrocytic and microglial response to injury and paracrine factor treatment. By identifying paracrine factors that are responsible for the regeneration of brain tissue following implantation of hNSCs in stroke brain, this work will increase the likelihood of successful clinical translation of stem cell therapy for stroke. Moreover, elucidating these molecular pathways important for brain recovery may ultimately identify novel therapeutic targets and offer hope to millions of Americans who live with the devastating effects of stroke.

Streptococcus suis serotype 2 enolase interaction with host brain microvascular endothelial cells and RPSA-induced apoptosis lead to loss of BBB integrity

Host proteins interacting with pathogens are receiving more attention as potential therapeutic targets in molecular medicine. Streptococcus suis serotype 2 (SS2) is an important cause of meningitis in both humans and pigs worldwide. SS2 Enolase (Eno) has previously been identified as a virulence factor with a role in altering blood brain barrier (BBB) integrity, but the host cell membrane receptor of Eno and The mechanism(s) involved are unclear. This study identified that SS2 Eno binds to 40S ribosomal protein SA (RPSA) on the surface of porcine brain microvascular endothelial cells leading to activation of intracellular p38/ERK-eIF4E signalling, which promotes intracellular expression of HSPD1 (heat-shock protein family D member 1), and initiation of host-cell apoptosis, and increased BBB permeability facilitating bacterial invasion. This study reveals novel functions for the host-interactional molecules RPSA and HSPD1 in BBB integrity, and provides insight for new therapeutic strategies in meningitis.