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Cited by 198Neuroinflammation and Neurodegeneration MechanismsAlzheimer's disease research and treatmentsInflammasome and immune disorders

The DOI matches its Crossref record; 52 of the 53 references it cites were found in a registry or an index.

Plaque-associated human microglia accumulate lipid droplets in a chimeric model of Alzheimer’s disease

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Claes, Christel, Danhash, Emma Pascal, Hasselmann, Jonathan, Chadarevian, Jean Paul, Shabestari, Sepideh Kiani, England, Whitney E., Lim, Tau En, Hidalgo, Jorge Luis Silva, Spitale, Robert C., Davtyan, Hayk, Blurton-Jones, Mathew·2021·Molecular Neurodegeneration
DOI 10.1186/s13024-021-00473-0PMC PMC8305935
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Abstract

Background: Disease-associated microglia (DAMs), that surround beta-amyloid plaques, represent a transcriptionally-distinct microglial profile in Alzheimer’s disease (AD). Activation of DAMs is dependent on triggering receptor expressed on myeloid cells 2 (TREM2) in mouse models and the AD TREM2-R47H risk variant reduces microglial activation and plaque association in human carriers. Interestingly, TREM2 has also been identified as a microglial lipid-sensor, and recent data indicates lipid droplet accumulation in aged microglia, that is in turn associated with a dysfunctional proinflammatory phenotype. However, whether lipid droplets (LDs) are present in human microglia in AD and how the R47H mutation affects this remains unknown. Methods: To determine the impact of the TREM2 R47H mutation on human microglial function in vivo, we transplanted wild-type and isogenic TREM2-R47H iPSC-derived microglial progenitors into our recently developed chimeric Alzheimer mouse model. At 7 months of age scRNA-seq and histological analyses were performed. Results: Here we report that the transcriptome of human wild-type TREM2 and isogenic TREM2-R47H DAM xenografted microglia (xMGs), isolated from chimeric AD mice, closely resembles that of human atherosclerotic foam cells. In addition, much like foam cells, plaque-bound xMGs are highly enriched in lipid droplets. Somewhat surprisingly and in contrast to a recent in vitro study, TREM2-R47H mutant xMGs exhibit an overall reduction in the accumulation of lipid droplets in vivo. Notably, TREM2-R47H xMGs also show overall reduced reactivity to plaques, including diminished plaque-proximity, reduced CD9 expression, and lower secretion of plaque-associated APOE. Conclusions: Altogether, these results indicate lipid droplet accumulation occurs in human DAM xMGs in AD, but is reduced in TREM2-R47H DAM xMGs, as it occurs secondary to TREM2-mediated changes in plaque proximity and reactivity.

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Fig. 1 Disease associated microglia resemble atherosclerotic foam cells and signature gene expression reveals partial TREM2 dependence (A) UMAP plot displaying clustering of TREM2WT/WTxMGs isolated from 7-month-old 5X-hCSF1 mice (n=3 mice; 22,107 cells; WT xMGs per mouse (5987, 7876, 8244) and R47H xMGs per mouse (3939, 5571); B UMAP plot displaying clustering of TREM2R47H/R47HxMGs isolated from 7-month-old 5X-hCSF1 mice (n=2 mice; 9,510 cells); C A dot plot reveals top marker genes that are significantly up- or downregulated for each of the seven clusters (FDR-adjusted p-value < 0.01); (D) Barplot displaying the average percentage of cells making up the 7 unique xMG clusters; E Volcano plot displaying genes significantly up- and downregulated when comparing all TREM2R47H/R47H cells vs. all TREM2WT/WT cells; F-G UMAP plots displaying the module scores for 7 key DAM signature genes and 29 Foam cell signature genes identified in (Fernandezet al., [41]) (Additional File 1) in TREM2WT/WT (F) and TREM2R47H/R47H(G); H A dot plot reveals foam cell genes are particularly enriched in the DAM cell cluster (FDR-adjusted p-value < 0.01). Size of the circles indicate the percentage of cells expressing that gene and color indicates average expression levels; I Violin plots demonstrate foam cell signature genes are particularly enriched in the DAM cell cluster vs. other clusters, and are significantly (adjusted p-value < 0.01; LFC≥0.01) albeit subtly downregulated in R47H cells when comparing all TREM2R47H/R47H (blue) vs. all TREM2WT/WT cells (green) via pseudobulk analysis (Additional File 1)
Fig. 1 Disease associated microglia resemble atherosclerotic foam cells and signature gene expression reveals partial TREM2 dependence (A) UMAP plot displaying clustering of TREM2WT/WTxMGs isolated from 7-month-old 5X-hCSF1 mice (n=3 mice; 22,107 cells; WT xMGs per mouse (5987, 7876, 8244) and R47H xMGs per mouse (3939, 5571); B UMAP plot displaying clustering of TREM2R47H/R47HxMGs isolated from 7-month-old 5X-hCSF1 mice (n=2 mice; 9,510 cells); C A dot plot reveals top marker genes that are significantly up- or downregulated for each of the seven clusters (FDR-adjusted p-value < 0.01); (D) Barplot displaying the average percentage of cells making up the 7 unique xMG clusters; E Volcano plot displaying genes significantly up- and downregulated when comparing all TREM2R47H/R47H cells vs. all TREM2WT/WT cells; F-G UMAP plots displaying the module scores for 7 key DAM signature genes and 29 Foam cell signature genes identified in (Fernandezet al., [41]) (Additional File 1) in TREM2WT/WT (F) and TREM2R47H/R47H(G); H A dot plot reveals foam cell genes are particularly enriched in the DAM cell cluster (FDR-adjusted p-value < 0.01). Size of the circles indicate the percentage of cells expressing that gene and color indicates average expression levels; I Violin plots demonstrate foam cell signature genes are particularly enriched in the DAM cell cluster vs. other clusters, and are significantly (adjusted p-value < 0.01; LFC≥0.01) albeit subtly downregulated in R47H cells when comparing all TREM2R47H/R47H (blue) vs. all TREM2WT/WT cells (green) via pseudobulk analysis (Additional File 1)CC BY · PubMed Central
Fig. 2 Plaque-associated human microglia accumulate Lipid Droplets, and Lipid Droplet area is reduced in TREM2-R47H transplanted mice. A Lipid droplets (red, PLIN2) accumulate in human microglia (green, GFP) adjacent to plaques in chimeric mice (blue, Amylo-Glo), but not in microglia distant from plaques;B with a nearly identical relationship observed in human microglia (green, IBA1) in AD postmortem brains; C Quantification of PLIN2 in GFP TREM2-R47H vs. GFP TREM2 xMGs (green, GFP; red, PLIN2) surrounding amyloid plaques (blue, Amylo-glo) in 7-month old 5X-hCSF1 reveal (D) a significant reduction in total PLIN2 area in R47H xMG transplanted mice (E) with no significant differences in total plaque area, F a significant reduction of the percentage of PLIN2 area normalized to plaque area was also detected in R47H xMG transplanted mice; G with no significant difference in the number of PLIN2+GFP xMGs in vicinity to plaques; Scale Bars at 10 mm in A, 5 mm in B, and 20 mm in C, n=3-4; 5-6 images per mouse; * P< 0.05; ** P < 0.01
Fig. 2 Plaque-associated human microglia accumulate Lipid Droplets, and Lipid Droplet area is reduced in TREM2-R47H transplanted mice. A Lipid droplets (red, PLIN2) accumulate in human microglia (green, GFP) adjacent to plaques in chimeric mice (blue, Amylo-Glo), but not in microglia distant from plaques;B with a nearly identical relationship observed in human microglia (green, IBA1) in AD postmortem brains; C Quantification of PLIN2 in GFP TREM2-R47H vs. GFP TREM2 xMGs (green, GFP; red, PLIN2) surrounding amyloid plaques (blue, Amylo-glo) in 7-month old 5X-hCSF1 reveal (D) a significant reduction in total PLIN2 area in R47H xMG transplanted mice (E) with no significant differences in total plaque area, F a significant reduction of the percentage of PLIN2 area normalized to plaque area was also detected in R47H xMG transplanted mice; G with no significant difference in the number of PLIN2+GFP xMGs in vicinity to plaques; Scale Bars at 10 mm in A, 5 mm in B, and 20 mm in C, n=3-4; 5-6 images per mouse; * P< 0.05; ** P < 0.01CC BY · PubMed Central
Fig. 3 xMGs expressing TREM2 upregulate activation markers around plaques, but less so in TREM2-R47H xMGs. A Quantification of xMG proximity to amyloid plaques (blue, Amylo-glo) in 7-month old 5X-hCSF1 revealed a reduction of plaque-associated GFP TREM2-R47H xMGs vs. GFP TREM2 xMGs (green, GFP; red, CD9), C within 10 mm per plaque; D A significant reduction in total levels of CD9, E without a significant difference in total plaque load, and F a significant reduction of the percentage of CD9 area normalized to plaque area was observed in TREM2-R47H vs. TREM2 xMGs. B, G PLIN2 (red) accumulating GFP xMGs (green) express the DAM-specific marker CD9 (purple) near plaques (blue, Amylo-Glo); H GFP TREM2-R47H vs. TREM2 xMGs (green, GFP; Red, APOE; white, LAMP1) reveal a significant reduction in total APOE area (I), with no significant difference in total plaque load (J), and a significant reduction in APOE area normalized to plaque area (K). An increased trend of the percentage of LAMP1 normalized to plaque area (L) was observed in TREM2-R47H xMGs without reaching significance (P=0.5635). Scale Bars at 10 mm in A and 20 mm in H; * P < 0.05; ** P < 0.01; **** P < 0.0001; n=3-4 mice per genotype; 5-6 images per mouse; Confocal images B(scales at 5 mm); n=3-4 mice per genotype; 3-4 images per mouse
Fig. 3 xMGs expressing TREM2 upregulate activation markers around plaques, but less so in TREM2-R47H xMGs. A Quantification of xMG proximity to amyloid plaques (blue, Amylo-glo) in 7-month old 5X-hCSF1 revealed a reduction of plaque-associated GFP TREM2-R47H xMGs vs. GFP TREM2 xMGs (green, GFP; red, CD9), C within 10 mm per plaque; D A significant reduction in total levels of CD9, E without a significant difference in total plaque load, and F a significant reduction of the percentage of CD9 area normalized to plaque area was observed in TREM2-R47H vs. TREM2 xMGs. B, G PLIN2 (red) accumulating GFP xMGs (green) express the DAM-specific marker CD9 (purple) near plaques (blue, Amylo-Glo); H GFP TREM2-R47H vs. TREM2 xMGs (green, GFP; Red, APOE; white, LAMP1) reveal a significant reduction in total APOE area (I), with no significant difference in total plaque load (J), and a significant reduction in APOE area normalized to plaque area (K). An increased trend of the percentage of LAMP1 normalized to plaque area (L) was observed in TREM2-R47H xMGs without reaching significance (P=0.5635). Scale Bars at 10 mm in A and 20 mm in H; * P < 0.05; ** P < 0.01; **** P < 0.0001; n=3-4 mice per genotype; 5-6 images per mouse; Confocal images B(scales at 5 mm); n=3-4 mice per genotype; 3-4 images per mouseCC BY · PubMed Central

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Metadata

Authors
Claes, C., Danhash, E. P., Hasselmann, J., Chadarevian, J. P., Shabestari, S. K., England, W. E., Lim, T. E., Hidalgo, J. L. S., Spitale, R. C., Davtyan, H., & Blurton-Jones, M.
Affiliations
University of California, Irvine (US)
Corresponding author
  • Claes, Christel
  • Blurton-Jones, Mathew
ORCID
Venue
Molecular Neurodegeneration
Publisher
Springer Science and Business Media LLC
Published
2021-07-23
Volume
16
Issue
1
Pages
50-50
ISSN
1750-1326 (ISSN-L)
DOI
10.1186/s13024-021-00473-0
PMC
PMC8305935
OpenAlex
W3184188306
Cited by
197
References
53
Citations by year
2026: 38 · 2025: 44 · 2024: 44 · 2023: 31 · 2022: 38 · 2021: 1
FWCI
11.41
Type
journal article
Language
en
Open access
Licence
Locations
  • Molecular Neurodegeneration (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • eScholarship (California Digital Library) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
  • BrightFocus Foundation (A2020451F)
  • National Institutes of Health (AG048099, AG056303, AG061895)
Topics
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Alzheimer's disease research and treatments
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Inflammasome and immune disorders
Keywords
Alzheimer's disease, disease-associated microglia, lipid droplets, TREM2, amyloid plaques, chimeric mouse model, CD9, apoE secretion, microglial activation, foam cells
MeSH terms
Alzheimer Disease, Animals, Brain, Chimera, Disease Models, Animal, Humans, Membrane Glycoproteins, Receptors, Immunologic, Microglia, Mice, Heterografts, Lipid Droplets

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