Lipid-droplet-accumulating microglia represent a dysfunctional and proinflammatory state in the aging brain

In the paper

“In the aging brain and in neurodegeneration, microglia lose their homeostatic molecular signature and show profound functional impairments, such as increased production of pro-inflammatory cytokines, elevated generation of reactive oxygen species (ROS) and build-up of dysfunctional lysosomal deposits indicative of impaired phagocytosis2.”

What the sources say

• Partly supported

  Section 4.4 reports generally increased pro-inflammatory cytokine release from aged microglia, altered marker expression, and increased oxidative stress with aging. Section 4.5 reports lysosomal inclusions in aged microglia, but says impaired degradation is a possible interpretation and that age-related effects on phagocytosis remain poorly defined. The source therefore supports the broad pattern, but not a definitive loss of a homeostatic molecular signature or the claim that the deposits establish impaired phagocytosis. (LLM, conf=0.87)

  cites [2] Mosher, K. I. & Wyss-Coray, T. Microglial dysfunction in brain aging and Alzheimer’s disease. Biochem. Pharmacol. 88, 594–604 (2014). sourceExperimental — accuracy not yet measured

In the paper

“Another characteristic of aged microglia is the increased production of inflammatory cytokines such as TNF-α, IL-1β and IL-6 under baseline conditions and excessive cytokine release upon immune challenge2.”

What the sources say

• Partly supported

  Section 4.4 (page unavailable) says proinflammatory cytokine production and release by aged microglia are generally increased, and identifies TNF-α, IL-1β and IL-6 as markers often elevated in aged mice. But it says secretion depends on the stimulant and notes studies finding no age-related activation differences without pathological insults; it does not establish increased production of all three under baseline conditions or consistently excessive release upon immune challenge. The Conclusion (page unavailable) presents over-reactivity to additional stimuli as a possibility. (LLM, conf=0.86)

  cites [2] Mosher, K. I. & Wyss-Coray, T. Microglial dysfunction in brain aging and Alzheimer’s disease. Biochem. Pharmacol. 88, 594–604 (2014). sourceExperimental — accuracy not yet measured

In the paper

“Impaired phagocytosis is considered a hallmark of microglia aging2.”

What the sources say

• Supported

  The Conclusion explicitly lists impaired phagocytosis among six proposed “hallmarks of microglial aging.” This directly supports the citing sentence’s characterization. (LLM, conf=0.94)

  cites [2] Mosher, K. I. & Wyss-Coray, T. Microglial dysfunction in brain aging and Alzheimer’s disease. Biochem. Pharmacol. 88, 594–604 (2014). source

In the paper

“Of note, we used an optimized microglia isolation strategy that uses mechanical tissue homogenization instead of enzymatic digestion, which keeps microglia largely in a non-activated state and therefore prevents unwanted bias towards an activated pro-inflammatory signature19.”

What the sources say

• ?Could not verify

  Split into 2 atoms — 0 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 2 unverifiable. Expand the claim to see per-atom verdicts.

  cites [19] Yu, Y., Ramachandran, P. V. & Wang, M. C. Shedding new light on lipid functions with CARS and SRS microscopy. Biochim. Biophys. Acta 1841, 1120–1129 (2014). sourceExperimental — accuracy not yet measured

In the paper

“Lipid droplets were also induced in LPS-treated mouse hippocampal slice cultures and in the N9 microglia cell line15,16.”

What the sources say

• ?Could not verify

  The Results section describes lipid-laden cells in brain tissue from aging mice, and the Methods describe staining brain sections. Searches for LPS-treated hippocampal slice cultures and the N9 microglia cell line found no passage addressing either experiment in our copy. (LLM, conf=0.74)

  cites [15] Shimabukuro, M. K. et al. Lipid-laden cells differentially distributed in the aging brain are functionally active and correspond to distinct phenotypes. Sci. Rep. 6, 23795 (2016). sourceExperimental — accuracy not yet measured
• Supported

  The Results (Figure 1 and accompanying text) report increased numbers of large lipid bodies after LPS treatment in both mouse hippocampal slice cultures and N9 microglia. In the slices, the total number of lipid bodies decreased, so the reported induction specifically concerns large lipid bodies. (LLM, conf=0.90)

  cites [16] Chang, P. K., Khatchadourian, A., McKinney, R. A. & Maysinger, D. Docosahexaenoic acid (DHA): a modulator of microglia activity and dendritic spine morphology. J. Neuroinflammation 12, 34 (2015). source

In the paper

“GRN mutations are linked to the development of frontotemporal dementia (FTD)34, and GRN−/− mice are used as a model for FTD and are characterized by microglial changes, neuroinflammation, and cognitive deficits36.”

What the sources say

• ?Could not verify

  Citation 36 is attached to the claim about GRN−/− mice. The Results and Discussion passages concern Slc33a1-mutant mice and hereditary spastic paraplegia; searches for GRN, progranulin, FTD, microglial changes, neuroinflammation, and cognitive deficits found no passage addressing the GRN−/− model. The separate claim that GRN mutations are linked to FTD is attached to citation 34, not this source. (LLM, conf=0.76)

  cites [34] Liu, P. et al. S113R mutation in SLC33A1 leads to neurodegeneration and augmented BMP signaling in a mouse model. Dis. Model. Mech. 10, 53–62 (2017). sourceExperimental — accuracy not yet measured
• ?Could not verify

  Citation 36 is attached to the claim about GRN−/− mice. The Discussion describes a rat model of VPS35-associated Parkinson’s disease, not a GRN−/− mouse model of FTD. Searches for GRN, FTD, microglial changes, neuroinflammation, and cognitive deficits found no passage addressing that claim. (LLM, conf=0.78)

  cites [36] Tsika, E. et al. Parkinson’s disease-linked mutations in VPS35 induce dopaminergic neurodegeneration. Hum. Mol. Genet. 23, 4621–4638 (2014). sourceExperimental — accuracy not yet measured

In the paper

“Oil-red-O positive “lipid-laden” cells, including neurons, astrocytes, ependymal cells and Iba1+ cells have recently been reported in mice and shown to increase with age 14.”

What the sources say

• Partly supported

  The Results section on Ndufs4−/− mice reports lipid droplets in mouse brain cells bearing astrocyte and microglia markers. It does not report Oil-red-O staining or lipid-laden ependymal cells or neurons. Nor does it show a general increase with age: droplets progressively disappeared in the vestibular nucleus as the mutant mice aged, although they persisted in the olfactory bulb (page unavailable in our copy). (LLM, conf=0.88)

  cites [14] Liu, L. et al. Glial lipid droplets and ROS induced by mitochondrial defects promote neurodegeneration. Cell 160, 177–190 (2015). sourceExperimental — accuracy not yet measured

In the paper

“Surprisingly, lipid droplets have not been studied functionally in brain myeloid cells in humans or vertebrates, and less than a handful of papers report the histological presence of lipid droplets in human brains11,12.”

What the sources say

• ?Could not verify

  The passages on atherosclerotic plaques (section labeled Abstract; page unavailable) describe lipid-loaded macrophage-like cells in mouse arteries, not brain myeloid cells. Searches for brain microglia, lipid droplets, and human-brain histology found no passage addressing whether functional studies exist or how many papers report their histological presence. (LLM, conf=0.76)

  cites [11] Childs, B. G. et al. Senescent intimal foam cells are deleterious at all stages of atherosclerosis. Science 354, 472–477 (2016). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [12] Castejon, O. J., Castellano, A., Arismendi, G. J. & Medina, Z. The inflammatory reaction in human traumatic oedematous cerebral cortex. J. Submicrosc. Cytol. Pathol. 37, 43–52 (2005).

In the paper

“This is of particular interest because it has been shown that in GRN−/− mice, neuroinflammation is most pronounced in the thalamus40.”

What the sources say

• ?Could not verify

  The Results passages concern fatty-acid trafficking in starved cells and mitochondrial-fusion-deficient cells, not neuroinflammation in GRN−/− mice. Searches for GRN−/− mice, thalamus, and progranulin-related neuroinflammation found no passage addressing the claim; page numbers were unavailable. (LLM, conf=0.78)

  cites [40] Rambold, A. S., Cohen, S. & Lippincott-Schwartz, J. Fatty acid trafficking in starved cells: regulation by lipid droplet lipolysis, autophagy, and mitochondrial fusion dynamics. Dev. Cell 32, 678–692 (2015). sourceExperimental — accuracy not yet measured

In the paper

“Excitingly, knockout of GRN, which causes frontotemporal dementia in people with loss of function mutations in this gene34, resulted in severe accumulation of lipid droplets in microglia in vivo.”

What the sources say

• ?Could not verify

  The Results and Discussion passages concern SLC33A1 mutations, hereditary spastic paraplegia, and BMP signaling, not GRN. Searches for GRN, progranulin, frontotemporal dementia, and loss-of-function mutations found no passage in our copy addressing the attributed claim. (LLM, conf=0.76)

  cites [34] Liu, P. et al. S113R mutation in SLC33A1 leads to neurodegeneration and augmented BMP signaling in a mouse model. Dis. Model. Mech. 10, 53–62 (2017). sourceExperimental — accuracy not yet measured

In the paper

“Lastly, there is emerging evidence that lysosomes become dysfunctional in aged microglia2.”

What the sources say

• Partly supported

  Section 4.5 (Phagocytosis; page unavailable) reports lysosomal inclusions in aged rodent microglia and says these may indicate impaired degradation of ingested material. That is emerging evidence consistent with the claim, but the paper does not establish that the lysosomes themselves become dysfunctional. (LLM, conf=0.82)

  cites [2] Mosher, K. I. & Wyss-Coray, T. Microglial dysfunction in brain aging and Alzheimer’s disease. Biochem. Pharmacol. 88, 594–604 (2014). sourceExperimental — accuracy not yet measured

In the paper

“Besides inflammation, metabolic changes towards increased fatty acid production have been reported to cause lipid droplet formation in immune cells9 and also in cancer cells41.”

What the sources say

• ?Not checked — no full text of the sourcecites [9] Bozza, P. T. & Viola, J. P. Lipid droplets in inflammation and cancer. Prostaglandins Leukot. Essent Fatty Acids 82, 243–250 (2010). source
• ?Could not verify

  The Results section on microglial activation reports increased microglia/macrophages in progranulin-knockout mice, and the ubiquitin-immunoreactivity section mentions a few foamy macrophages. Neither passage addresses increased fatty acid production or lipid droplet formation in immune cells. Searches for those terms found no supporting passage; the cancer-cell portion is attached to a different citation. (LLM, conf=0.75)

  cites [41] Ghoshal, N., Dearborn, J. T., Wozniak, D. F. & Cairns, N. J. Core features of frontotemporal dementia recapitulated in progranulin knockout mice. Neurobiol. Dis. 45, 395–408 (2012). sourceExperimental — accuracy not yet measured

In the paper

“For example, lipid droplets in microglia have been detected in adult mice after induction of ROS by rotenone13, in hippocampal slice culture from P6–8 mice upon treatment with LPS, and in LPS-treated cells of the microglia-like cell line N916.”

What the sources say

• Supported

  The Results report lipid bodies in LPS-treated N9 microglia and quantify an increase in large lipid bodies. The Figure 1 caption also describes lipid-body formation in LPS-treated N9 cells. These passages support the portion of the citing sentence attributed to this paper. (LLM, conf=0.94)

  cites [16] Chang, P. K., Khatchadourian, A., McKinney, R. A. & Maysinger, D. Docosahexaenoic acid (DHA): a modulator of microglia activity and dendritic spine morphology. J. Neuroinflammation 12, 34 (2015). source

In the paper

“For example, expression of ACLY, a key enzyme in the shift from the TCA cycle to lipid formation that has been shown to cause lipid droplet accumulation42, is significantly higher in LDAM than in microglia without lipid droplets.”

What the sources say

• Partly supported

  The ACLY subsection of “Blocking Fatty Acid Synthesis” says ACLY links glucose metabolism to fatty-acid synthesis and that knocking it down reduces conversion of glucose to lipid. The “Diverting Fatty Acids to Storage” subsection discusses lipid droplets, but does not say ACLY causes their accumulation. Page numbers are unavailable in our copy. (LLM, conf=0.87)

  cites [42] Currie, E., Schulze, A., Zechner, R., Walther, T. C. & Farese, R. V. Jr. Cellular fatty acid metabolism and cancer. Cell Metab. 18, 153–161 (2013). sourceExperimental — accuracy not yet measured

In the paper

“Recently, it has been shown that several subsets of microglia with unique molecular and functional phenotypes exist in the healthy, aged, and degenerating brain3–5.”

What the sources say

• Partly supported

  The Results identify distinct microglial states in an Alzheimer’s mouse model, with altered gene expression and phagocytic characteristics; they also compare these cells with wild-type controls. The paper does not establish several distinct subsets across healthy, normally aged, and degenerating brains: its disease-associated states were observed in the AD model, not the wild-type controls. No page numbers are available in our copy. (LLM, conf=0.86)

  cites [3] Keren-Shaul, H. et al. A unique microglia type associated with restricting development of Alzheimer’s disease. Cell 169, 1276–1290.e17 (2017). sourceExperimental — accuracy not yet measured
• Supported

  The Results section on disease-associated microglia distinguishes homeostatic adult microglia from the MGnD phenotype during aging and disease progression. The Results section on neuritic Aβ plaques identifies three microglial subsets with different molecular markers and plaque associations; the Discussion also describes phagocytosis-associated phenotypic changes. The copy provides no page numbers for these passages. (LLM, conf=0.89)

  cites [4] Krasemann, S. et al. The TREM2-APOE pathway drives the transcriptional phenotype of dysfunctional microglia in neurodegenerative diseases. Immunity 47, 566–581.e9 (2017). source
• Partly supported

  The Results describe distinct microglial populations in the healthy developing mouse brain, and the Discussion compares one of them with disease-associated microglia. But the paper does not establish several distinct subsets in aged brains; its Discussion instead reports little transcriptomic variation among classical adult microglia. The claim extends the paper’s findings beyond the populations it studied. (LLM, conf=0.85)

  cites [5] Li, Q. et al. Developmental heterogeneity of microglia and brain myeloid cells revealed by deep single-cell RNA sequencing. Neuron 101, 207–223.e10 (2019). sourceExperimental — accuracy not yet measured

In the paper

“Lipid droplets can form due to various environmental and cellular conditions, including elevated concentrations of extracellular lipids, inflammatory events, increased ROS levels and intracellular metabolic changes38,39.”

What the sources say

• Partly supported

  The copy’s Abstract reports lipid-droplet formation during allergic pulmonary inflammation and after inflammatory MIF stimulation of eosinophils. It does not address elevated extracellular lipids, increased ROS, or intracellular metabolic changes as causes; searches for those terms returned no supporting passage. No page number is available in the indexed copy. (LLM, conf=0.86)

  cites [38] Vieira-de-Abreu, A. et al. Cross-talk between macrophage migration inhibitory factor and eotaxin in allergic eosinophil activation forms leukotriene C(4)-synthesizing lipid bodies. Am. J. Respir. Cell Mol. Biol. 44, 509–516 (2011). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [39] Hu, X., Xu, B. & Ge, W. The role of lipid bodies in the microglial aging process and related diseases. Neurochem. Res. 42, 3140–3148 (2017). source

In the paper

“This is in line with findings which have shown that lipid droplet containing immune cells in the periphery are detrimental, including foamy macrophages in atherosclerosis10 or lipid droplet-rich eosinophils in experimental models of allergy37.”

What the sources say

• ?Not checked — no full text of the sourcecites [10] den Brok, M. H., Raaijmakers, T. K., Collado-Camps, E. & Adema, G. J. Lipid droplets as immune modulators in myeloid cells. Trends Immunol. 39, 380–392 (2018). source
• ?Could not verify

  The citation is attached to the example of lipid droplet-rich eosinophils in experimental allergy models. Our copy’s Discussion addresses inflammation and immune responses in progranulin-deficient mice, but searches for eosinophils, lipid droplets, and allergy found no passage addressing that example. Page numbers were not available in the indexed copy. (LLM, conf=0.76)

  cites [37] Yin, F. et al. Behavioral deficits and progressive neuropathology in progranulin-deficient mice: a mouse model of frontotemporal dementia. FASEB J. 24, 4639–4647 (2010). sourceExperimental — accuracy not yet measured

In the paper

“Likewise, LDAM showed only low overlap with the transcriptome of recently identified “lipid-associated macrophages” from mouse and human adipose tissue, a cell population that controls metabolic homeostasis in a TREM2 dependent manner and is transcriptionally similar to DAM48.”

What the sources say

• ?Could not verify

  The Results discuss ATGL expression in macrophages and foam cells, while the Introduction and Discussion focus on lipid storage and phagocytosis (page numbers unavailable). Searches for TREM2-dependent metabolic homeostasis and transcriptional similarity to DAM found no passage addressing either claim. (LLM, conf=0.75)

  cites [48] Chandak, P. G. et al. Efficient phagocytosis requires triacylglycerol hydrolysis by adipose triglyceride lipase. J. Biol. Chem. 285, 20192–20201 (2010). sourceExperimental — accuracy not yet measured

In the paper

“Almost 2,000 genes were differentially expressed between LD-hi and LD-lo microglia (Fig. 7h) and linked to metabolic processes and cellular response to stress (Fig. 7i), pathways that are also enriched in LDAM (Fig, 2e, Extended Data Fig. 2b).”

In the paper

“Pathway Analysis of differentially expressed genes revealed Phagosome maturation and Production of NO and ROS, two key functions of microglia that become dysregulated with age, as the most significant pathways associated with LD-hi microglia (Fig. 2e).”

In the paper

“Lipidomics analysis revealed that lipid droplets from the whole hippocampus and from aged microglia show a nearly identical lipid distribution and are mainly composed of glycerolipids (hippocampus: 41.3%; microglia: 44.4%), while cholesteryl esters were almost absent (hippocampus: 1.1%; microglia: 0.7%) (Fig. 1k).”

In the paper

“We used flow cytometry to measure ROS levels and found significantly increased ROS generation in BV2 cells with sgRNAs targeting GRN and SLC33A1 cells under baseline conditions and in SLC33A1 sgRNA expressing cells upon LPS treatment (Fig. 6h).”

In the paper

“Production of NO and ROS was the second most significantly regulated pathway in LDAM (Fig. 2e) with over 90% of the differentially expressed genes increased (Fig. 5a).”

In the paper

“Interestingly, we observed characteristic lipid droplets in aged but rarely in young microglia and they were frequently adjacent to dense lysosomal material (Fig. 1a).”

In the paper

“Unsupervised cluster analysis segregated LD-lo from LD-hi microglia and revealed prominent differences between their transcriptome with 692 significantly differentially expressed genes (Fig. 2c,d).”

In the paper

“We found that microglia in the hippocampus of GRN−/− mice contained high numbers of lipid droplets, resulting in a twofold higher percentage of BODIPY+ microglia and twice as many lipid droplets per cell in GRN−/− mice compared with wild type littermates (Fig. 7a–c).”

In the paper

“In addition, lipid droplets from BV2 cells and from aged microglia showed a similar chain length distribution of TAG-associated fatty acids with peaks at 38:2 and 44:5, while liver lipid droplets had a shift towards longer TAG chain fatty acids with a peak at 52:2 carbon atoms, which is in agreement with previous reports26 (Fig. 3g,h).”

In the paper

“Interestingly, phagosome maturation was the top regulated pathway associated with the transcriptome of LDAM (Fig. 2e), characterized by upregulation of endosomal and lysosomal genes (Fig. 4a) and increased immunoreactivity for the lysosome-associated protein CD68 in BODIPY+ microglia in the hippocampus of aged mice (Fig. 4b,c).”

In the paper

“We found that although only nine common genes were differentially expressed in all three data sets (one of them was the lipid droplet specific gene PLIN3), the directionality of expression changes of LDAM genes was remarkably similar for all groups and almost identical for LDAM and LD-hi GRN−/− microglia (Fig. 7l,m; Extended Data Figure 6).”

In the paper

“Lipid droplets were primarily found in microglia but not in other cell types.”

In the paper

“Interestingly, they had a highly similar overall lipid content and a similar composition of neutral lipids, with low amounts of cholesteryl esters but high levels of glycerolipids (MAG, TAG).”

In the paper

“In addition, sgRNAs targeting GRN and SLC33A1 induced significant defects in phagocytosis and increased ROS production in BV2 cells, hence recapitulating the functional impairments of LDAM.”

In the paper

“Interestingly, we found that LPS treatment, which provokes an acute inflammatory response in the brain, led to lipid droplet formation in hippocampal microglia in young mice in vivo and in the microglia cell line BV2 in vitro.”

In the paper

“We did not find ultrastructural evidence for cholesterol crystals, and lipidomics analysis revealed that these lipid droplets contained mainly glycerolipids and only low amounts of cholesteryl ester.”

In the paper

“Indeed, sgRNAs targeting these genes were able to increase (SLC33A1, GRN, VPS35) and decrease (SNX17) lipid droplet load in microglial BV2 cells.”

In the paper

“Intriguingly, we observed that LDAM contain high numbers of lysosomes, and moreover, these lysosomes accumulate in close contact to lipid droplets.”

In the paper

“These lipid droplet rich microglia in GRN−/− mice show a similar transcriptome signature and the same functional impairments as LDAM.”

In the paper

“We found that although only nine common genes were differentially expressed in all three data sets (one of them was the lipid droplet specific gene PLIN3), the directionality of expression changes of LDAM genes was remarkably similar for all groups and almost identical for LDAM and LD-hi GRN−/− microglia (Fig. 7l,m; Extended Data Figure 6).”

In the paper

“BODIPY+/Iba1+ cells were frequently found in the thalamus and were detected to a lesser extent in cortex and corpus callosum.”

In the paper

“Lipid droplet accumulating microglia are abundant in the hippocampus but rare in other brain regions of aged mice.”

In the paper

“Paired dot plot showing FPKM values of LD-lo and LD-hi microglia for ApoE (paired Student’s t-test; P= 0.423).”

In the paper

“Since triacylglycerides (TAG) are a major component of lipid droplets in LDAM, it is possible that lipid droplet accumulation in GRN deficient microglia contributes to elevated TAG levels in brains lacking GRN.”

In the paper

“Pie charts showing that the lipid composition of lipid droplets from young and aged microglia is highly similar, but differs between young and aged liver tissue.”

In the paper

“LPS treatment induces lipid droplet formation in microglia and in BV2 cells.”

In the paper

“Here, lipid droplets are production and storage sites for eicosanoids and inflammatory cytokines, and are further involved in antigen presentation and pathogen clearance9.”

What the sources say

• ?Not checked — no full text of the sourcecites [9] Bozza, P. T. & Viola, J. P. Lipid droplets in inflammation and cancer. Prostaglandins Leukot. Essent Fatty Acids 82, 243–250 (2010). source

In the paper

“In particular, lipid droplets, which are lipid storing organelles that contain neutral lipids such as glycerolipids and cholesterol, are increasingly accepted as structural markers of inflammation8.”

What the sources say

• ?Not checked — no full text of the sourcecites [8] Fowler, S. D., Mayer, E. P. & Greenspan, P. Foam cells and atherogenesis. Ann. NY Acad. Sci. 454, 79–90 (1985). source

In the paper

“Myeloid cells form lipid droplets in response to inflammation and stress, including the aforementioned macrophages in atherosclerotic lesions, leukocytes in inflammatory arthritis, and eosinophils in allergic inflammation.”

What the sources say

• ?Not checked — no full text of the sourcecites [9] Bozza, P. T. & Viola, J. P. Lipid droplets in inflammation and cancer. Prostaglandins Leukot. Essent Fatty Acids 82, 243–250 (2010). source

In the paper

“Collectively, these data suggest that lipid droplet-rich microglia have phagocytosis deficits and that increased lipid storage is associated with impaired phagocytosis.”

In the paper

“These findings suggest that LDAM are in a primed activation state that becomes hyperactivated upon stimulation with LPS.”

In the paper

“Together, these findings demonstrate that LDAM have elevated concentrations of ROS and suggest that lipid droplets mediate LPS-induced ROS generation.”

In the paper

“Importantly, lipid-droplet rich foam cells in atherosclerosis show hallmarks of senescent cells and they seem deleterious at all stages of disease10.”

What the sources say

• ?Not checked — no full text of the sourcecites [10] den Brok, M. H., Raaijmakers, T. K., Collado-Camps, E. & Adema, G. J. Lipid droplets as immune modulators in myeloid cells. Trends Immunol. 39, 380–392 (2018). source

In the paper

“That they may have important functions in disease has recently been suggested in a drosophila model where lipid droplet formation has been reported in glia at the onset of neurodegeneration13.”

What the sources say

• ?Not checked — no full text of the sourcecites [13] Lee, S. C., Moore, G. R., Golenwsky, G. & Raine, C. S. Multiple sclerosis: a role for astroglia in active demyelination suggested by class II MHC expression and ultrastructural study. J. Neuropathol. Exp. Neurol. 49, 122–136 (1990). source

In the paper

“Together, these findings demonstrate that LPS triggers lipid droplet formation in microglia in vitro and in vivo, and lipid droplet containing microglia in young LPS-treated mice show a transcriptional signature that partially overlaps with LDAM.”

In the paper

“Furthermore, LPS-induced lipid droplets in BV2 cells are highly similar to lipid droplets in aged microglia, thus making this in vitro assay a useful model to study lipid droplets in LDAM.”

In the paper

“Overall, these data suggest that lipid droplet-containing aged microglia show transcriptional changes of genes related to key microglia functions such as phagocytosis, ROS production and immune signaling, yet they have a unique transcriptome signature that is distinct from previously described microglia states observed in aging and neurodegeneration.”

In the paper

“In a drosophila model for neurodegeneration13, lipid droplets in glia form due to an APOE dependent transfer of lipids from neurons to glia.”

What the sources say

• ?Not checked — no full text of the sourcecites [13] Lee, S. C., Moore, G. R., Golenwsky, G. & Raine, C. S. Multiple sclerosis: a role for astroglia in active demyelination suggested by class II MHC expression and ultrastructural study. J. Neuropathol. Exp. Neurol. 49, 122–136 (1990). source

In the paper

“This finding is in line with a previous report which observed that at the sites of atherosclerotic lesions, lipid droplet rich foamy macrophages show decreased phagocytosis activity compared to macrophages without lipid droplets46.”

What the sources say

• ?Not checked — no full text of the sourcecites [46] Nadjar, A. Role of metabolic programming in the modulation of microglia phagocytosis by lipids. Prostaglandins Leukot. Essent. Fatty Acids 135, 63–73 (2018). source

In the paper

“Together, these findings validate the in vivo relevance of our in vitro CRISPR screen and confirm that microglia from GRN−/− mice contain lipid droplets.”

In the paper

“Together, these findings indicate that LDAM represent a dysfunctional and pro-inflammatory microglia state in the aging brain, and further suggest that LDAM might contribute to neurodegenerative diseases.”

In the paper

“In this study, we identify a novel, lipid droplet accumulating microglia (LDAM) state in the aging brain and show that LDAM are characterized by a unique transcriptional signature, severe functional deficits and a pro-inflammatory phenotype.”

In the paper

“LDAM and DAM also show different functional phenotypes; while DAM are actively phagocytic populations, LDAM are severely impaired in this function.”

In the paper

“Remarkably, LD-hi microglia from GRN−/− mice and LDAM in aging have similar functional and transcriptional phenotypes, suggesting that lipid droplet containing GRN−/− microglia share the LDAM state.”

In the paper

“In the brain, a protective role has been reported for lipid droplets in glia in a drosophila model for neurodegeneration13.”

What the sources say

• ?Not checked — no full text of the sourcecites [13] Lee, S. C., Moore, G. R., Golenwsky, G. & Raine, C. S. Multiple sclerosis: a role for astroglia in active demyelination suggested by class II MHC expression and ultrastructural study. J. Neuropathol. Exp. Neurol. 49, 122–136 (1990). source

In the paper

“However, lipid droplets have also been correlated with beneficial functions, such as improved host defense and antigen cross presentation in myeloid cells9.”

What the sources say

• ?Not checked — no full text of the sourcecites [9] Bozza, P. T. & Viola, J. P. Lipid droplets in inflammation and cancer. Prostaglandins Leukot. Essent Fatty Acids 82, 243–250 (2010). source

In the paper

“In peripheral immune cells, lipid droplets form often as a response to inflammation and stress9.”

What the sources say

• ?Not checked — no full text of the sourcecites [9] Bozza, P. T. & Viola, J. P. Lipid droplets in inflammation and cancer. Prostaglandins Leukot. Essent Fatty Acids 82, 243–250 (2010). source

In the paper

“For example, lipid droplets in microglia have been detected in adult mice after induction of ROS by rotenone13, in hippocampal slice culture from P6–8 mice upon treatment with LPS, and in LPS-treated cells of the microglia-like cell line N916.”

What the sources say

• ?Not checked — no full text of the sourcecites [13] Lee, S. C., Moore, G. R., Golenwsky, G. & Raine, C. S. Multiple sclerosis: a role for astroglia in active demyelination suggested by class II MHC expression and ultrastructural study. J. Neuropathol. Exp. Neurol. 49, 122–136 (1990). source

In the paper

“Cholesterol accumulation has recently been observed in phagocytes in an EAE demyelination model in aged mice as a result of excessive uptake of myelin debris43.”

What the sources say

• ?Not checked — no full text of the sourcecites [43] Burke, A. C. & Huff, M. W. ATP-citrate lyase: genetics, molecular biology and therapeutic target for dyslipidemia. Curr. Opin. Lipidol. 28, 193–200 (2017). source

In the paper

“In this context, a study in macrophages has shown that engulfment of cellular debris relies on the availability of free fatty acids, which are released upon degradation of lipid droplets, thus linking effective lysis of lipid droplets with successful phagocytosis47.”

What the sources say

• ?Not checked — no full text of the sourcecites [47] Chinetti-Gbaguidi, G. et al. Human atherosclerotic plaque alternative macrophages display low cholesterol handling but high phagocytosis because of distinct activities of the PPARγ and LXRα pathways. Circ. Res. 108, 985–995 (2011). source

In the paper

“Microglia in the LDAM state, which account for more than 50% of all microglia in the aged hippocampus, but not microglia without lipid droplets, show typical age-related functional impairments and a primed phenotype, suggesting that LDAM may be the primary detrimental microglia state in the aging brain.”

In the paper

“Together, we show that LDAM demonstrate a novel state of microglia with a unique transcriptional signature and functional impairments in the aging brain, and we identified lipid droplet containing microglia in a GRN−/− model for chronic neuroinflammation, and in an LPS-induced acutely inflamed brain milieu.”

In the paper

“Data were replicated in at least three independent experiments.”

In the paper

“All samples used were obtained from individuals without any neurological or psychiatric diagnoses.”

In the paper

“Data in a-b were replicated in at least two independent experiments.”

In the paper

“Data collection was randomized for all experiments.”

In the paper

“For quantification of BODIPY+ microglia, of CD68hi microglia, of BODIPY+ lipid droplet numbers and of lipid droplet size, analyses were performed blinded on coded slides.”

In the paper

“No sample-size calculations were performed.”

In the paper

“Further, sample sizes were chosen based on prior literature using similar experimental paradigms.”

In the paper

“Six randomly selected visual fields per animal were photographed using a confocal scanning laser microscope (LSM 700, Zeiss) with LSM software (ZEN 2011) and used for quantitative analysis.”

In the paper

“For quantification of CARS signal in microglia, 20 randomly selected microglia in the dentate gyrus per animal were imaged.”

In the paper

“False discovery rate was estimated using Benjamini and Hochberg approach (Benjamini and Hochberg, 1995).”

In the paper

“Experimenters were blinded for imaging and data analysis.”

In the paper

“All samples passed a quality control threshold (RIN ≥ 9.0) to proceed to library preparations and RNAseq.”

In the paper

“Sample size was determined to be adequate based on the magnitude and consistency of measurable differences between groups.”

In the paper

“sgRNA infection was confirmed by flow cytometry, which indicated >90% of cells expressed the mCherry reporter.”