Spatially Resolved Microglial Expression Around Aβ Plaques in Human Alzheimer’s Disease Tissue
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ABSTRACT:
PROVIDER: PRJNA1310559 | ENA |
REPOSITORIES: ENA
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Project description:Using microglia-enriched spatial transcriptomics on human Alzheimer’s disease tissue, we identify distinct gene expression changes across microglia located in direct contact with plaques, in periplaque regions, and in areas distant from plaques. We define a group of plaque contact–only microglial (PCOM) genes whose expression increases exclusively in microglia directly contacting plaques. These genes show significant overlap with previously reported gene sets, suggesting that plaque-contacting microglia correspond to the well-characterised disease-associated microglia (DAM) and other AD-related gene-expression signatures. We further identify distinct co-expression networks associated with disease-relevant covariates, including an immune module linked to APOE genotype and a synaptic–mitochondrial module negatively associated with Braak stage. Finally, we compare the human dataset to our previously published data from 18-month-old AppNL-F mice, generated using the same experimental paradigm and demonstrate cross-species concordance in gene expression within plaque-contacting microglia.
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Project description:Anti-amyloid β-peptide (Aβ) immune therapy was developed as treatment for Alzheimer’s disease (AD) to reduce and prevent amyloid plaque pathology. This approach has proven successful in phase 3 clinical trials of Aducanumab, Lecanemab and Donanemab. These antibodies induce robust amyloid plaque clearance, slow memory decline, and have beneficial effects on daily living activities. The therapeutic effects correlate with the efficacy of plaque removal. Treatment is associated with adverse side-effects, such as oedema and haemorrhages (ARIA-E and -H), which are potentially linked to the induced immune response. To improve therapeutic safety, it is therefore imperative to understand the effects of anti-Aβ antibody treatment on immune cell function. We investigated the effects of long-term chronic Aducanumab treatment on amyloid plaque pathology and microglial response in the APP-SAA triple knock-in mouse model. Mice were treated weekly with Aducanumab from 4-8 months of age. Long-term treatment with Aducanumab results in a robust and dose-dependent removal of amyloid plaque pathology. Analysis of the CSF proteome indicates a reduction of markers for neurodegeneration including tau and α-synuclein. Consistent with a reduction of glucose uptake, the therapeutic effects were accompanied by reduced microglial activation. RNAseq confirmed a dose-dependent decrease in the disease-associated microglia (DAM) transcriptional signature of microglia, which is supported by a parallel decrease of Trem2 protein. However, genes associated with antigen-presentation were still increased after treatment. IHC confirms that Aducanumab treatment increases microglial clustering, as well as MHC-II expression around plaques and ELISA confirmed increased cytokine levels. These findings demonstrate that long-term chronic Aducanumab-mediated removal of Aβ leads to a dose dependent decrease in microglial activation and neurodegeneration, but induces a unique antibody treatment-related microglial phenotype associated with antigen presentation, which may be related to plaques still present after the 4 months treatment period.
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Project description:INTRODUCTION: Omics studies have revealed that various brain cell types undergo profound molecular changes in Alzheimer’s disease (AD) but the spatial relationships with plaques and tangles and APOE-linked differences remain unclear. METHODS: We performed laser capture microdissection of Ab plaques, the 50mm halo around them, tangles with the 50mm halo around them, and areas distant (>50mm) from plaques and tangles in the temporal cortex of AD and control donors, followed by RNA-sequencing. RESULTS: Ab plaques exhibited upregulated microglial (neuroinflammation) and downregulated neuronal (neurotransmission/energy metabolism) genes, whereas tangles had mostly downregulated neuronal genes. Ab plaques had more differentially expressed genes than tangles. We identified a gradient Ab plaque>peri-plaque>tangle>distant for these changes. AD APOEe4 homozygotes had greater changes than APOEe3 across locations, especially within Ab plaques. DISCUSSION: Transcriptomic changes in AD consist primarily of neuroinflammation and neuronal dysfunction, are spatially associated mainly with Ab plaques, and are exacerbated by the APOEe4 allele.
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Project description:Microglia are involved in Alzheimer’s disease (AD) by adopting activated phenotypes. How ageing in the absence or presence of β-amyloid (Aβ) deposition in different brain areas affects this response and whether sex and AD risk genes are involved, remains however largely unknown. Here we analyzed the gene expression profiles of more than 10,000 individual microglia cells isolated from cortex and hippocampus of male and female AppNL-G-F at 4 different stages of Aβ deposition and in age-matched control mice. We demonstrate that microglia adopt two major activated states during normal aging and after exposure to amyloid plaques. One of the responses (activated response microglia, ARM) is enhanced in particular by amyloid plaques and is strongly enriched with AD risk genes. The ARM response is not homogeneous, as subgroups of microglia overexpressing MHC type II and tissue repair genes (Dkk2, Gpnmb, Spp1) are induced upon prolonged Aβ exposure. Microglia in female mice advance faster in the activation trajectories. Similar activated states were also found in a second AD model and in human brain. We demonstrate that abolishing the expression of Apoe, the major genetic risk factor for AD, impairs the establishment of ARMs, while the second microglia response type, enriched for interferon response genes, remains unaffected. Our data indicate that ARMs are the converging point of multiple AD risk factors.
2019-04-23 | GSE127892 | GEO
Project description:Microglia are involved in Alzheimer’s disease (AD) by adopting activated phenotypes. How ageing in the absence or presence of β-amyloid (Aβ) deposition in different brain areas affects this response and whether sex and AD risk genes are involved, remains however largely unknown. Here we analyzed the gene expression profiles of more than 10,000 individual microglia cells isolated from cortex and hippocampus of male and female AppNL-G-F at 4 different stages of Aβ deposition and in age-matched control mice. We demonstrate that microglia adopt two major activated states during normal aging and after exposure to amyloid plaques. One of the responses (activated response microglia, ARM) is enhanced in particular by amyloid plaques and is strongly enriched with AD risk genes. The ARM response is not homogeneous, as subgroups of microglia overexpressing MHC type II and tissue repair genes (Dkk2, Gpnmb, Spp1) are induced upon prolonged Aβ exposure. Microglia in female mice advance faster in the activation trajectories. Similar activated states were also found in a second AD model and in human brain. We demonstrate that abolishing the expression of Apoe, the major genetic risk factor for AD, impairs the establishment of ARMs, while the second microglia response type, enriched for interferon response genes, remains unaffected. Our data indicate that ARMs are the converging point of multiple AD risk factors.
2019-04-23 | GSE127884 | GEO
Project description:We investigated spatiotemporal molecular patterns related to AD pathophsiology using spatially resolved transcriptome of the AD mouse model. The late change of gray matters of AD was commonly related to neuroinflammation, while the early change in the white matter of AD represented neuronal projection and ensheathment of axons before the amyloid plaques accumulation. Disease-associated microglia and astrocyte signatures were spatially differently enriched. Our results provide a key spatiotemporally heterogeneous molecular change particularly related to inflammation in AD.
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Project description:Aberrant increase of arachidonic acid (ARA) has long been implicated in the pathology of Alzheimer's disease (AD), while the underlying causal mechanism remains unclear. In this study, we revealed a link between ARA mobilization and microglial dysfunction in Aβ pathology. Lipidomic analysis of primary microglia from AppNL-GF mice showed a marked increase in free ARA and lysophospholipids (LPLs) along with a decrease in ARA-containing phospholipids, suggesting increased ARA release from phospholipids (PLs). To manipulate ARA-containing PLs in microglia, we genetically deleted Lysophosphatidylcholine Acyltransferase 3 (Lpcat3), the main enzyme catalyzing the incorporation of ARA into PLs. Loss of microglial Lpcat3 reduced the levels of ARA-containing phospholipids, free ARA and LPLs, leading to a compensatory increase in monounsaturated fatty acid (MUFA)-containing PLs in the AppNL-GF mice. Notably, the reduction of ARA in microglia significantly ameliorated oxidative stress and inflammatory responses while enhancing the phagocytosis of Aβ plaques and promoting the compaction of Aβ deposits. Mechanistically, sc-RNA seq suggested that LPCAT3 deficiency facilitates phagocytosis by facilitating de novo lipid synthesis while protecting microglia from oxidative damage. Collectively, our study reveals a novel mechanistic link between ARA mobilization and microglial dysfunction in AD. Lowering brain ARA levels through pharmacological or dietary interventions may be a potential therapeutic strategy to slow down AD progression.
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Project description:Amyloid-beta (Aβ) is a key factor in the onset and progression of Alzheimer's disease (AD). Selenium (Se) compounds show promise in AD treatment. Here, we reveal that selenoprotein K (SELENOK), a selenoprotein involved in immune regulation and potentially related to AD pathology, plays a critical role in microglial immune response, migration, and phagocytosis. In vivo and in vitro studies corroborate that SELENOK deficiency inhibits microglial Aβ phagocytosis, exacerbating cognitive deficits in 5xFAD mice, which are reversed by SELENOK overexpression. Mechanistically, SELENOK is involved in CD36 palmitoylation through DHHC6, regulating CD36 localization to microglial plasma membranes and thus impacting Aβ phagocytosis. CD36 palmitoylation is reduced in the brains of AD patients and mice. Se supplementation promotes SELENOK expression and CD36 palmitoylation, enhancing microglial Aβ phagocytosis and mitigating AD progression. We have identified the regulatory mechanisms from Se-dependent selenoproteins to Aβ pathology, providing novel insights into potential therapeutic strategies involving Se and selenoproteins.
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Project description:The innate immune system can develop a form of memory called priming, where prior exposure to a stimulus enhances subsequent responses. While well-characterized in peripheral immunity, its function in brain-resident cells such as astrocytes under non-disease conditions remains unclear. Here we show that human astrocytes derived from the induced pluripotent stem cells of healthy female donors, but not microglia, acquire a primed state following transient immune stimulations. Upon subsequent exposure to amyloid-β (Aβ), these astrocytes secrete elevated levels of cytokines and promote microglial Aβ uptake. In contrast, astrocytes carrying the Alzheimer’s disease (AD) risk allele APOE4 exhibit reduced priming and fail to support microglial phagocytosis. These findings are validated in astrocyte-microglial co-cultures, cerebral organoids, and male mice, where astrocyte priming enhances Aβ clearance in an APOE4-sensitive manner. Our findings identify astrocytic immune memory as a modulator of microglial function and Aβ pathology, providing insights into how early protective responses in AD may be disrupted by genetic risk factors.
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Project description:The innate immune system can develop a form of memory called priming, where prior exposure to a stimulus enhances subsequent responses. While well-characterized in peripheral immunity, its function in brain-resident cells such as astrocytes under non-disease conditions remains unclear. Here we show that human astrocytes derived from the induced pluripotent stem cells of healthy female donors, but not microglia, acquire a primed state following transient immune stimulations. Upon subsequent exposure to amyloid-β (Aβ), these astrocytes secrete elevated levels of cytokines and promote microglial Aβ uptake. In contrast, astrocytes carrying the Alzheimer’s disease (AD) risk allele APOE4 exhibit reduced priming and fail to support microglial phagocytosis. These findings are validated in astrocyte-microglial co-cultures, cerebral organoids, and male mice, where astrocyte priming enhances Aβ clearance in an APOE4-sensitive manner. Our findings identify astrocytic immune memory as a modulator of microglial function and Aβ pathology, providing insights into how early protective responses in AD may be disrupted by genetic risk factors.
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