Microglia - astrocyte cross-talk in the amyloid plaque niche of an Alzheimer’s disease mouse model as revealed by spatial transcriptomics (CosMx)
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ABSTRACT:
ORGANISM(S): Mus musculus Homo sapiens
PROVIDER: GSE263791 | GEO | 2024/04/19
REPOSITORIES: GEO
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Project description:In this study, we characterize the transcriptomic alterations, cellular compositions, and signaling perturbations in the amyloid plaque niche in an AD mouse model using high-resolution spatial transcriptomics (CosMx and Stereo-seq). We discover a wide heterogeneity in the cellular composition of amyloid plaque niches, marked by an increase in microglial accumulation over time. We profile the alterations of glial cells as they are exposed to plaques, and conclude that the microglial response to plaques is consistent across different brain regions, while the astrocytic response is more heterogeneous. In turn, as the microglial density of plaque niches increases, astrocytes acquire a more neurotoxic phenotype and play a key role in inducing GABAergic signaling and decreasing glutamatergic signaling in neurons of the hippocampus. Taken together, we show that astrocytic signaling around plaque pathology is disrupted with increasing microglial density, which in turn induces an imbalance in synaptic signaling in neurons in the hippocampus.
2024-04-19 | GSE263789 | GEO
Project description:The e4 allele of the apolipoprotein E (APOE) gene is the strongest genetic risk factor for late-onset Alzheimer's disease and has been shown to increase amyloid pathology relative to the presence of the e2 and e3 alleles. In the brain, apoE is primarily produced by astrocytes and under pathological conditions also by microglia. The cell-type-specific role of apoE in amyloid pathology, especially after amyloid plaque deposition, has not been fully elucidated. We generated APPPS1-21/Aldh1l1-Cre/ERT2/apoE4flox/flox and APPPS1-21/apoE4flox/flox mice. At 3.8-months-of-age, during the phase of rapid plaque growth, we administered tamoxifen to reduce astrocytic APOE4 and assessed mice at 6-months-of-age. One day before tamoxifen treatment, mice were injected with methoxy-X04, a blood-brain-barrier permeant fluorescent marker that labeled the pre-existing fibrillar amyloid plaques. By using this strategy, we were able to characterize pre-existing plaques prior to the loss of astrocytic APOE4 and to also analyze newly-formed amyloid plaques after the loss of astrocytic APOE4. Interestingly, astrocytic APOE4 deletion strongly reduced pre-existing plaques. It also prevented new plaque formation and decreased glial reactivity. Importantly, the removal of astrocytic APOE4 resulted in enhanced microglial and astrocytic phagocytic ability, which may contribute to the reduction of the amyloid pathology.
2021-09-30 | GSE183050 | GEO
Project description:One of the hallmarks of Alzheimer’s disease is the presence of extracellular diffuse and fibrillar plaques predominantly consisting of the amyloid-β (Aβ) peptide. ApoE influences the deposition of amyloid pathology through affecting the clearance and aggregation of monomeric Aβ in the brain. In addition to influencing Aβ metabolism, increasing evidence suggests that apoE influences microglial function in neurodegenerative diseases. Here, we characterize the impact that apoE has on amyloid pathology and the innate immune response in APPPS1∆E9 and APPPS1-21 transgenic mice. We report that Apoe deficiency reduced fibrillar plaque deposition consistent with previous studies. However, fibrillar plaques in Apoe-deficient mice exhibited a striking reduction in plaque compaction. Hyperspectral fluorescent imaging using luminescent conjugated oligothiophenes identified distinct Aβ morphotypes in Apoe-deficient mice. We also observed a significant reduction in fibrillar plaque-associated microgliosis and activated microglial gene expression in Apoe-deficient mice, along with significant increases in dystrophic neurites around fibrillar plaques. Our results suggest that apoE is critical in stimulating the innate immune response to amyloid pathology.
2018-02-15 | GSE109906 | GEO
Project description:Two microglial TAM receptor tyrosine kinases - Axl and Mer - have been linked to Alzheimer’s disease, but their roles in disease have not been tested experimentally. We find that in Alzheimer’s disease and its mouse models, induced expression of Axl and Mer in amyloid plaque-associated microglia is coupled to induced plaque decoration by the TAM ligand Gas6 and its co-ligand phosphatidylserine. In the APP/PS1 mouse model of Alzheimer’s disease, sIngle cell RNAseq analysis comparing wild type microglia with those with Axl and Mer deficiency reveals a similar disease state transitional program of microglia but a dampened differential expression of numerous AD siganture genes in microglia lacking TAM receptors. In line with the transcriptomic data, using two-photon microscopy, we show that genetic ablation of Axl and Mer results in microglia that are unable to normally detect, respond to, organize, or phagocytose amyloid beta plaques. These major deficits notwithstanding, and contrary to expectation, TAM-deficient APP/PS1 mice develop fewer dense-core plaques than APP/PS1 mice with normal microglia. Our findings reveal that the TAM system is an essential mediator of microglial recognition and engulfment of amyloid plaques, and that TAM-driven microglial phagocytosis does not constrain, but rather promotes, plaque development.
2021-02-25 | GSE160523 | GEO
Project description:Microglial dysfunction is a key pathological feature of Alzheimer´s disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their consequences for microglial function. Here, we performed an in-depth proteomic characterization of microglia in two AD mouse models, the overexpression APPPS1 and the knock-in AppNL-G-F (APP-KI) model. Proteome changes were followed from pre-deposition to early, middle and advanced stages of amyloid plaque pathology, revealing a large panel of Microglial Amyloid Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations triggered by Adeposition. We demonstrate that the occurrence of MARPs coincided with the deposition of fibrillar A, recruitment of microglia to amyloid plaques and phagocytic dysfunction. While the proteomic and functional microglial changes were already markedly seen in 3 months old APPPS1 mice, they were delayed in the APP-KI model that generates substantially less fibrillar A. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.
2020-06-09 | PXD016075 | Pride
Project description:Background: The p38 alpha mitogen-activated protein kinase (p38a) pathway is linked to both innate and adaptive immune responses, and as such, is currently under active investigation as a target for drug development in the context of Alzheimer’s disease (AD) and other conditions with neuroinflammatory dysfunction. While preclinical data has shown that p38a inhibition can protect against AD-associated neuropathology, the underlying mechanisms are only partially elucidated. Inhibitors of p38a may provide benefit via modulation of microglial-associated neuroinflammatory responses that contribute to the development of AD pathology. The present study tests this hypothesis by knocking out microglial p38a and assessing early-stage pathological changes. Materials and methods: Conditional knockout of microglial p38a was accomplished in 5-month-old C57BL/6J wild-type and amyloidogenic AD model (APPswe/PS1dE9) mice using a tamoxifen-inducible Cre/loxP system. Beginning at 7.5 months of age, animals underwent behavioral assessment on the open field and radial arm water maze tests, followed by collection of cortical and hippocampal tissues at 11 months. Additional endpoint measures included microglial RNA-seq analysis, quantification of pro-inflammatory cytokines, assessment of amyloid burden and plaque deposition, and characterization of microglia-plaque dynamics using a combination of ELISA, immunohistochemical, and immunofluorescent techniques. Results: Loss of microglial p38a did not alter behavioral outcomes, pro-inflammatory cytokine levels, or overall amyloid plaque burden. However, this manipulation did significantly increase hippocampal levels of soluble Abeta42 and reduce colocalization of Iba1 and 6E10 in a subset microglia in close proximity to plaques, indicating that p38a suppression may alter microglial phagocytosis. Conclusion: The data presented here suggest that rather than reducing inflammation per se, the net effect of microglial p38a inhibition in the context of AD-type amyloid pathology could be an alteration of phagocytosis and/or plaque deposition. Additionally, these results support future investigations of microglial p38a signaling at different stages of disease, as well as its relationship to phagocytic processes in this particular cell-type.
2023-06-01 | GSE222257 | GEO
Project description:The complement system is part of the innate immune system that works to clear pathogens and cellular debris. In the central nervous system (CNS) complement activation can promote synaptic pruning clearance of neuronal blebs recruitment of phagocytes and protection from pathogens. However in a neuropathologic environment complement activation may contribute to inflammatory pathways neuronal dysfunction and in the Alzheimer’s disease (AD) brain cognitive decline. If complement activation proceeds to the cleavage of C5 and thus generation of C5a engagement of C5a with the receptor C5aR1 can instigate a feed-forward loop of inflammation injury and neuronal death thus making this molecule a potential target for modulation in AD therapeutics. The Arctic (Arc) AD mouse model known to rapidly accumulate fibrillar amyloid plaques was crossed to a model that lacks the receptor for C5a (ArcC5aR1KO) or to a transgenic mouse that generates C5a under the GFAP promoter (ArcC5a+). ArcticC5a+ mice showed accelerated loss of spatial memory compared to Arc mice. While eliminating C5aR1 did not alter amyloid plaque accumulation in this AD model C5aR1KO delayed or prevented the expression of important AD-associated genes in the hippocampus indicating a separation between those genes induced by amyloid plaques and those influenced by C5a-C5aR1 signaling. C5ar1 deletion also reduced/delayed the expression of select pan-reactive and A1 reactive astrocyte genes. ArcC5aR1KO showed delayed expression of genes enriched for biological processes that are significant in the AD context such as regulation of inflammatory signaling microglial cell activation astrocyte migration and lysosome pathway. Interestingly overexpression of C5a also delayed the increase of some AD- complement and astrocyte-associated genes perhaps mediated by C5aR2 and emphasizing the importance of selectively suppressing C5aR1. Immunohistochemical investigation further confirmed that modulation of C5a-C5aR1 either delayed or reduced some reactive microglial markers in the Arc hippocampus including CD11b and CD11c. These results suggest that C5a-C5aR1 signaling in the context of AD largely exerts its effects by suppressing those microglial activation pathways that accelerate disease enhancing pathways. Given the highly focused modulation of a common driver of neurotoxicity pharmacological inhibition of this C5aR1 signaling pathway is a promising therapeutic strategy to treat AD.
2022-03-05 | GSE197591 | GEO
Project description:Alzheimer's disease (AD) is characterized by a sequential progression of amyloid plaques (A), neurofibrillary tangles (T) and neurodegeneration (N), constituting ATN pathology. While microglia are considered key contributors to AD pathogenesis, their contribution in the combined presence of ATN pathologies remains incompletely understood. As sensors of the brain microenvironment, microglial phenotypes and contributions are importantly defined by the pathologies in the brain, indicating the need for their analysis in preclinical models that recapitulate combined ATN pathologies, besides their role in A and T models only. Here, we report a new tau-seed model in which amyloid pathology facilitates bilateral tau propagation associated with brain atrophy, thereby recapitulating robust ATN pathology. Single-cell RNA sequencing revealed that ATN pathology exacerbated microglial activation towards disease-associated microglia (DAM) states, with a significant upregulation of Apoe as compared to amyloid-only models (A). Importantly, Colony-Stimulating Factor 1 Receptor inhibition preferentially eliminated non-plaque-associated versus plaque associated microglia. The preferential depletion of non-plaque-associated microglia significantly attenuated tau pathology and neuronal atrophy, indicating their detrimental role during ATN progression. Together, our data reveal the intricacies of microglial activation and their contributions to pathology in a model that recapitulates the combined ATN pathologies of Alzheimer's disease. Our data may provide a basis for microglia-targeting therapies selectively targeting detrimental microglial populations, while conserving protective populations.
2021-06-03 | GSE176032 | GEO
Project description:PLCγ2-P522R (phospholipase C gamma 2, proline 522 to arginine) is a protective variant that reduces the risk for late onset Alzheimer’s disease (LOAD). Recently, it was shown to decrease β-amyloid pathology in 5XFAD mouse model of AD. In this study, our goal was to investigate the protective functions of PLCγ2-P522R variant in less aggressive mouse model of AD as well as to assess underlying mechanisms at the molecular and cellular level using mouse and human microglia models. The effects of the protective PLCγ2-P522R variant on microglia activation, AD-related β-amyloid and neuronal pathologies, as well as behavioral changes were investigated in PLCγ2-P522R knock-in mice crossbred with an APP/PS1 mouse model of AD. Transcriptomic, proteomic, and functional studies were carried out in cultured and acutely isolated adult PLCγ2-P522R mouse microglia to study molecular mechanisms. Finally, microglia-like cell models generated from blood and skin biopsy samples of the PLCγ2-P522R variant carriers were employed to translate the key findings in human cells. Our results demonstrate that the PLCγ2-P522R variant reduces brain β-amyloid plaque burden of APP/PS1 mice. Simultaneously, PLCγ2-P522R variant increased non-proinflammatory microglia activation and microglia clustering around β-amyloid plaques, leading to reduced β-amyloid plaque-associated neuronal dystrophy. In cultured mouse primary microglia, PLCγ2-P522R variant decreased accumulation of large lipid droplets, reduced cell stress, and increased acute response to strong inflammatory stimuli. Transcriptomic and proteomic analyses in acutely isolated adult mouse microglia as well as in human monocyte-derived microglial cells showed that PLCγ2-P522R upregulates mitochondrial fatty acid oxidation and downregulates inflammatory/interferon signaling pathways. Accordingly, PLCγ2-P522R increased mitochondrial respiration in iPSC -derived microglial cells. Together, these findings suggest that PLCγ2-P522R variant exerts protection against AD-associated β-amyloid and neuronal pathologies via enhancing microglial barrier formation around β-amyloid plaques, but suppressing pro-inflammatory activation. Observed changes in fatty acid metabolism and mitochondrial flexibility as well as the downregulation of genes involved in inflammatory signaling pathways suggest that these protective effects of the PLCγ2-P522R variant are mediated through an anti-ageing mechanism.
2024-09-16 | GSE277167 | GEO
Project description:Neuroinflammation is thought to contribute to the pathogenesis of Alzheimer’s disease (AD), yet numerous studies have demonstrated a beneficial role for neuroinflammation in amyloid plaque clearance. We have previously shown that sustained expression of IL-1β in the hippocampus of APP/PS1 mice decreases amyloid plaque burden independent of recruited CCR2+ myeloid cells, suggesting resident microglia as the main phagocytic effectors of IL-1β-induced plaque clearance. To date, however, the mechanisms of IL-1β-induced plaque clearance remain poorly understood. To determine whether IL-1β-induced plaque clearance is due to enhanced microglial phagocytosis of Aβ, APP/PS1 mice induced to express mature human IL-1β in the hippocampus via adenoviral transduction were treated with the Aβ fluorescent probe methoxy-X04 (MX04) and microglial internalization of Aβ was analyzed by flow cytometry and immunohistochemistry. We found that resident microglia (CD45loCD11b+) constituted >70% of the MX04+ cells in both control and IL-1β-treated conditions, and that <10% of MX04+ cells were recruited myeloid cells (CD45hiCD11b+). However, we found that IL-1β treatment did not augment the percentage of MX04+ microglia nor the quantity of Aβ internalized by individual microglia. Instead, we found that IL-1β treatment resulted in a significant increase in the total number of MX04+ microglia in the hippocampus due to IL-1β-induced proliferation. Consistent with these results, transcriptomic analyses revealed very similar gene expression profiles between MX04+ and MX04- microglia, indicating IL-1β does not drive enhanced expression of phagocytosis-related genes. By contrast, IL-1β treatment was associated with large-scale changes in the expression of genes related to proliferation, immune function and inflammation. Together, these studies demonstrate that IL-1β induces microglial proliferation and the expression of genes involved in inflammatory immune functions that may be related to Aβ clearance.
2019-05-01 | GSE113539 | GEO