Reactive astrocyte nomenclature, definitions, and future directions

May combine two claims.

GFAP expression is modulated by physiological stimuli such as physical activity, enriched environments, and glucocorticoids, and fluctuates with circadian rhythms in the suprachiasmatic nucleus.

“Expression of GFAP is also modulated by physiological stimuli such as physical activity19, exposure to enriched environments19, and glucocorticoids20, and it fluctuates with circadian rhythms in the suprachiasmatic nucleus21.”

• cites [19] Rodríguez, J. J., Terzieva, S., Olabarria, M., Lanza, R. G. & Verkhratsky, A. Enriched environment and physical activity reverse astrogliodegeneration in the hippocampus of AD transgenic mice. Cell Death Dis 4, e678 (2013). sourcePartly supported

  The paper reports that voluntary running and enriched environments increased the surface area and volume of GFAP-positive astrocyte profiles in the hippocampus of mice (main text; page not provided). It does not establish that GFAP expression itself changed. The glucocorticoid and circadian-rhythm clauses are attached to other citations, not this source. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [20] O’Callaghan, J. P., Brinton, R. E. & McEwen, B. S. Glucocorticoids regulate the synthesis of glial fibrillary acidic protein in intact and adrenalectomized rats but do not affect its expression following brain injury. J. Neurochem. 57, 860–869 (1991). sourceNot checked — no full text of the source
• cites [21] Gerics, B., Szalay, F. & Hajós, F. Glial fibrillary acidic protein immunoreactivity in the rat suprachiasmatic nucleus: circadian changes and their seasonal dependence. J. Anat. 209, 231–237 (2006). Early demonstration that GFAP is regulated in a physiological context. sourceNot checked — no full text of the source

May combine two claims.

The degree of GFAP upregulation in reactive astrocytes often parallels the severity of injury, but this correlation is not always proportional, perhaps due to regional differences of astrocytes including basal GFAP content.

“However, while the degree of GFAP upregulation in reactive astrocytes often parallels the severity of the injury6, this correlation is not always proportional, perhaps due to regional differences of astrocytes, including basal GFAP content13,14.”

• cites [6] Escartin, C., Guillemaud, O. & Carrillo-de Sauvage, M. A. Questions and (some) answers on reactive astrocytes. Glia 67, 2221–2247 (2019). sourceCould not verify

  The passages available from our copy are repository metadata and navigation text, not the paper’s discussion; they have no section or page labels. Searches for GFAP upregulation, injury severity, regional differences, and basal GFAP content returned no passage addressing the claim, so it cannot be assessed from this copy. (LLM, conf=0.72)

  Experimental — accuracy not yet measured
• cites [13] Griemsmann, S. et al. Characterization of panglial gap junction networks in the thalamus, neocortex, and hippocampus reveals a unique population of glial cells. Cereb. Cortex 25, 3420–3433 (2015). sourceSupported
• cites [14] Ben Haim, L. & Rowitch, D. H. Functional diversity of astrocytes in neural circuit regulation. Nat. Rev. Neurosci. 18, 31–41 (2017). sourceNot checked — no full text of the source

May combine two claims.

Dye-filling methods can visualize whole astrocytes in mice and in human brain samples from surgical resections.

“Further, dye-filling methods can be used to visualize whole astrocytes in mice23, as well as in human brain samples from surgical resections (Fig. 1b)24.”

• cites [23] Wilhelmsson, U. et al. Redefining the concept of reactive astrocytes as cells that remain within their unique domains upon reaction to injury. Proc. Natl Acad. Sci. USA 103, 17513–17518 (2006). The complete visualization of astrocytes using whole-cell filling techniques revealed that reactive astrocytes display subtle morphological changes and remain in their 3D territorial domain, highlighting that GFAP immunostaining overestimates the true degree of astrocyte hypertrophy. sourceSupported
• cites [24] Sosunov, A. A. et al. Phenotypic heterogeneity and plasticity of isocortical and hippocampal astrocytes in the human brain. J. Neurosci. 34, 2285–2298 (2014). sourceSupported

May combine two claims.

GFAP is expressed by progenitor cells and its expression depends on developmental stages.

“GFAP is also expressed by progenitor cells15 and its expression depends on developmental stages16,17.”

• cites [15] Kriegstein, A. & Alvarez-Buylla, A. The glial nature of embryonic and adult neural stem cells. Annu. Rev. Neurosci. 32, 149–184 (2009). sourceSupported
• cites [16] Cahoy, J. D. et al. A transcriptome database for astrocytes, neurons, and oligodendrocytes: a new resource for understanding brain development and function. J. Neurosci. 28, 264–278 (2008). This study represented a technical and conceptual breakthrough in the neurosciences as the first unbiased classification of brain cell populations based on transcriptomic profiles using early microarray analyses. The resulting transcriptomes are a powerful tool to gain insight into novel brain cell functions. More recently, the classification of brain cells has been further refined and enriched by sc/snRNAs sourceCould not verify

  The citation to this paper is attached to the developmental-stage part of the sentence, not the progenitor-cell part. The section on gene expression changes during astrocyte and oligodendrocyte development compares developmental stages, and the Aldh1L1 marker section discusses GFAP, but neither passage says that GFAP expression changes with developmental stage. Searches for GFAP at P1, P7, and P17 found no decisive passage. (LLM, conf=0.70)

  Experimental — accuracy not yet measured
• cites [17] Roybon, L. et al. Human stem cell-derived spinal cord astrocytes with defined mature or reactive phenotypes. Cell Rep 4, 1035–1048 (2013). sourceSupported

May combine two claims.

Astrocytes undergo distinct morphological changes other than hypertrophy in pathological contexts, including elongation, process extension toward injury site, and some 3D domain overlap.

“Thorough visualization is necessary because astrocytes undergo distinct morphological changes other than hypertrophy in pathological contexts, including elongation, process extension toward injury site, and some three-dimensional (3D) domain overlap26.”

• cites [26] Schiweck, J., Eickholt, B. J. & Murk, K. Important shapeshifter: mechanisms allowing astrocytes to respond to the changing nervous system during development, injury and disease. Front. Cell. Neurosci. 12, 261 (2018). sourceSupported

May combine two claims.

Increased GFAP immunoreactivity largely reflects changes in the astrocytic cytoskeleton and tends to exaggerate the degree of hypertrophy because, except for scar-border astrocytes, the volume accessed by reactive astrocytes does not change, as they remain in their territorial domains.

“Increased GFAP immunoreactivity largely reflects changes in the astrocytic cytoskeleton and tends to exaggerate the degree of hypertrophy because, with the exception of scar-border astrocytes, the volume accessed by reactive astrocytes does not change, as they remain in their territorial domains23.”

• cites [23] Wilhelmsson, U. et al. Redefining the concept of reactive astrocytes as cells that remain within their unique domains upon reaction to injury. Proc. Natl Acad. Sci. USA 103, 17513–17518 (2006). The complete visualization of astrocytes using whole-cell filling techniques revealed that reactive astrocytes display subtle morphological changes and remain in their 3D territorial domain, highlighting that GFAP immunostaining overestimates the true degree of astrocyte hypertrophy. sourcePartly supported

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

  Experimental — accuracy not yet measured

May combine two claims.

Expression of some astrocyte proteins may change in reactive astrocytes, and some might be expressed by other cell types in specific brain regions.

“In addition, the expression of some of these proteins may change in reactive astrocytes22 (Table 1), and some might be expressed by other cell types in specific brain regions13.”

• cites [22] Serrano-Pozo, A., Gómez-Isla, T., Growdon, J. H., Frosch, M. P. & Hyman, B. T. A phenotypic change but not proliferation underlies glial responses in Alzheimer disease. Am. J. Pathol. 182, 2332–2344 (2013). sourceSupported
• cites [13] Griemsmann, S. et al. Characterization of panglial gap junction networks in the thalamus, neocortex, and hippocampus reveals a unique population of glial cells. Cereb. Cortex 25, 3420–3433 (2015). sourceSupported

May combine two claims.

Transcriptomic profiling shows that reactive astrocytes adopt distinct molecular states in different disease models, in different CNS regions, and in brain tumors.

“Such transcriptomic profiling specifically shows that reactive astrocytes adopt distinct molecular states in different disease models48,66–70, in different CNS regions70, and in brain tumors71.”

• cites [48] Anderson, M. A. et al. Astrocyte scar formation aids central nervous system axon regeneration. Nature 532, 195–200 (2016). sourcePartly supported

  The Extended Data compare RNA-seq profiles of spinal-cord-injury reactive astrocytes with previously reported forebrain stroke-reactive astrocytes; only 58.5% of the top elevated forebrain genes were also significantly elevated after spinal cord injury. This supports molecular differences between those contexts, but disease model and CNS region change together, so the paper does not establish distinct states attributable to region independently. The brain-tumor clause is attached to a different citation. (LLM, conf=0.83)

  Experimental — accuracy not yet measured
• cites [66] Zamanian, J. L. et al. Genomic analysis of reactive astrogliosis. J. Neurosci. 32, 6391–6410 (2012). First evidence for molecular heterogeneity of reactive astrocytes using microarray-based transcriptomics of acutely isolated astrocytes from mouse models of ischemia and septic shock. Studies in virtually all models of CNS diseases followed. sourceSupported
• cites [67] Orre, M. et al. Isolation of glia from Alzheimer’s mice reveals inflammation and dysfunction. Neurobiol. Aging 35, 2746–2760 (2014). sourceNot checked — no full text of the source
• cites [68] Sirko, S. et al. Astrocyte reactivity after brain injury-: The role of galectins 1 and 3. Glia 63, 2340–2361 (2015). sourcePartly supported

  The Results section, “Injury-Induced Changes of Gene Expression in the Cerebral Cortex GM Astrocytes” (page unavailable), reports transcriptomic differences between reactive and nonreactive astrocytes after cortical injury. The Introduction describes a stab-wound model and comparison with neural stem cells, not reactive astrocytes across different disease models or CNS regions. The brain-tumor clause is attached to citation 71, not this source. (LLM, conf=0.83)

  Experimental — accuracy not yet measured
• cites [69] Diaz-Castro, B., Gangwani, M. R., Yu, X., Coppola, G. & Khakh, B. S. Astrocyte molecular signatures in Huntington’s disease. Sci. Transl. Med. 11, eaaw8546 (2019). sourceNot checked — no full text of the source
• cites [70] Itoh, N. et al. Cell-specific and region-specific transcriptomics in the multiple sclerosis model: Focus on astrocytes. Proc. Natl Acad. Sci. USA 115, E302–E309 (2018). sourcePartly supported

  The Results section, “Regional Differences in Astrocyte-Specific Gene Expression During EAE” (page unavailable), reports distinct astrocyte gene-expression patterns across CNS regions during EAE. This paper studies one disease model, so it does not itself establish differences between disease models. The brain-tumor clause is attached to citation 71, not this source. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [71] John Lin, C. C. et al. Identification of diverse astrocyte populations and their malignant analogs. Nat. Neurosci. 20, 396–405 (2017). sourcePartly supported

  The Results section on malignant glioma reports distinct expression-profile correlations between astrocyte subpopulations and glioblastoma subtypes, and the Discussion describes molecularly distinct populations emerging during tumor progression. This supports the brain-tumor portion attached to this citation, but the paper does not establish that reactive astrocytes adopt those states; it studies astrocyte subpopulations and their malignant glioma analogs. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

Manipulation of reactive astrocytes has resulted in improved outcomes, worse outcomes, and no change in mouse models of AD and MS.

“For example, the manipulation of reactive astrocytes has resulted in improved outcomes38,42,43, worse35 outcomes, and no change44 in mouse models of AD and MS40,45,46.”

• cites [38] Furman, J. L. et al. Targeting astrocytes ameliorates neurologic changes in a mouse model of Alzheimer’s disease. J. Neurosci. 32, 16129–16140 (2012). sourceSupported
• cites [42] Ceyzériat, K. et al. Modulation of astrocyte reactivity improves functional deficits in mouse models of Alzheimer’s disease. Acta Neuropathol. Commun. 6, 104 (2018). sourceSupported
• cites [43] Reichenbach, N. et al. Inhibition of Stat3-mediated astrogliosis ameliorates pathology in an Alzheimer’s disease model. EMBO Mol. Med. 11, e9665 (2019). sourceSupported
• cites [35] Kraft, A. W. et al. Attenuating astrocyte activation accelerates plaque pathogenesis in APP/PS1 mice. FASEB J. 27, 187–198 (2013). sourceSupported
• cites [44] Kamphuis, W. et al. GFAP and vimentin deficiency alters gene expression in astrocytes and microglia in wild-type mice and changes the transcriptional response of reactive glia in mouse model for Alzheimer’s disease. Glia 63, 1036–1056 (2015). sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

In the study of AD transgenic and wild-type mice, homeostatic astrocytes were predominant in healthy mice, whereas disease-associated astrocytes were unique to AD mice.

“In this study, ‘homeostatic astrocytes’ were predominant in healthy mice, whereas ‘disease-associated astrocytes’ were unique to AD mice.”

• cites [78] Habib, N. et al. Disease-associated astrocytes in Alzheimer’s disease and aging. Nat. Neurosci. 23, 701–706 (2020). sourcePartly supported

  The paper reports a homeostatic Gfap-low state in wild-type mice and a disease-associated astrocyte state observed only in AD mice in its initial comparison (Abstract; no page given). But its age-series analysis also finds DAA-like cells in older wild-type mice, so the unqualified claim that they were unique to AD mice overstates the finding. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

May combine two claims.

Functions lost or altered in reactive astrocytes include neurotransmitter and ion buffering in mouse HD models, communication via gap junctions in the sclerotic hippocampus of patients with epilepsy, phagocytic clearance of dystrophic neurites, and metabolic coupling by glycolysis-derived d-serine and lactate in mouse AD models.

“Functions lost or altered in reactive astrocytes include neurotransmitter and ion buffering in mouse HD models58, communication via gap junctions in the sclerotic hippocampus of patients with epilepsy59, phagocytic clearance of dystrophic neurites60, and metabolic coupling by glycolysis-derived d-serine61 and lactate62 in mouse AD models.”

• cites [58] Tong, X. et al. Astrocyte Kir4.1 ion channel deficits contribute to neuronal dysfunction in Huntington’s disease model mice. Nat. Neurosci. 17, 694–703 (2014). Demonstration with targeted molecular manipulations that loss of astrocyte homeostatic functions contributes to HD pathogenesis. sourcePartly supported

  The Discussion reports reduced GLT-1 and Kir4.1 expression and impaired extracellular potassium maintenance in HD mouse models, supporting altered neurotransmitter and ion buffering. But it says these early functional changes occurred without astrogliosis; the Results likewise found little or no striatal astrogliosis at symptomatic ages. This source therefore does not support describing the affected astrocytes as reactive. (LLM, conf=0.90)

  Experimental — accuracy not yet measured
• cites [59] Bedner, P. et al. Astrocyte uncoupling as a cause of human temporal lobe epilepsy. Brain 138, 1208–1222 (2015). sourceSupported
• cites [60] Gomez-Arboledas, A. et al. Phagocytic clearance of presynaptic dystrophies by reactive astrocytes in Alzheimer’s disease. Glia 66, 637–653 (2018). sourceSupported

May combine two claims.

hiPSC-derived astrocytes are amenable to study responses to viral infection and to specific stimuli.

“hiPSC-derived astrocytes are also amenable to study responses to viral infection83 and to specific stimuli84.”

• cites [83] Ledur, P. F. et al. Zika virus infection leads to mitochondrial failure, oxidative stress and DNA damage in human iPSC-derived astrocytes. Sci. Rep. 10, 1218 (2020). sourceSupported
• cites [84] Perriot, S. et al. Human induced pluripotent stem cell-derived astrocytes are differentially activated by multiple sclerosis-associated cytokines. Stem Cell Reports 11, 1199–1210 (2018). sourceSupported

May combine two claims.

Studies in rodents document region-dependent and often contradictory changes in aging astrocytes, such as an increase in cellular volume and overlap of astrocyte processes, but also atrophy, increase in GFAP content, or even a reduction in the number of GFAP+ and GS+ astrocytes.

“Studies in rodents document region-dependent and often contradictory changes in aging astrocytes, such as an increase in cellular volume and overlap of astrocyte processes, but also atrophy, increase in GFAP content, or even a reduction in the number of GFAP+ and GS+ astrocytes87–89.”

• cites [87] Rodríguez, J. J. et al. Complex and region-specific changes in astroglial markers in the aging brain. Neurobiol. Aging 35, 15–23 (2014). sourceNot checked — no full text of the source
• cites [88] Cerbai, F. et al. The neuron-astrocyte-microglia triad in normal brain ageing and in a model of neuroinflammation in the rat hippocampus. PLoS One 7, e45250 (2012). sourcePartly supported

  Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured
• cites [89] O’Callaghan, J. P. & Miller, D. B. The concentration of glial fibrillary acidic protein increases with age in the mouse and rat brain. Neurobiol. Aging 12, 171–174 (1991). sourceNot checked — no full text of the source

May combine two claims.

Astrocytes generated from hiPSC derived from fibroblasts of patients with CNS diseases show pathological phenotypes, including dysregulation of lipid metabolism, alteration in extracellular vesicles, reduced autophagy, or altered STAT3 signaling.

“Interestingly, astrocytes generated from hiPSC derived from fibroblasts obtained from patients with CNS diseases (usually with a genetic mutation causative of disease or a risk polymorphism) show pathological phenotypes, including dysregulation of lipid metabolism11, alteration in the contents of the extracellular vesicles released by astrocytes80, reduced autophagy81, or altered STAT3 signaling82”

• cites [11] Lin, Y. T. et al. APOE4 causes widespread molecular and cellular alterations associated with Alzheimer’s disease phenotypes in human iPSC-derived brain cell types. Neuron 98, 1141–1154.e7 (2018). Technically improved generation of hiPSC-derived astrocytes demonstrates that astrocytes harboring a genetic risk factor for AD are diseased astrocytes that may further exacerbate ongoing pathology. sourceSupported
• cites [80] Varcianna, A. et al. Micro-RNAs secreted through astrocyte-derived extracellular vesicles cause neuronal network degeneration in C9orf72 ALS. EBioMedicine 40, 626–635 (2019). sourcePartly supported

  The Results section (“MicroRNAs regulating axonal maintenance are selectively dysregulated in C9 patient ADEVs”; page unavailable) reports altered miRNA cargo in extracellular vesicles released by C9orf72-ALS patient astrocytes, supporting the point attached to this citation. However, the Materials and methods section (“Conversion of skin fibroblasts to induced neural progenitor cells”; page unavailable) describes direct conversion of patient fibroblasts to neural progenitor cells and then astrocytes, not generation through hiPSCs. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [81] di Domenico, A. et al. Patient-specific iPSC-derived astrocytes contribute to non-cell-autonomous neurodegeneration in Parkinson’s disease. Stem Cell Reports 12, 213–229 (2019). sourceSupported

May combine two claims.

Astrocyte Ca2+ dynamics and network responses become aberrant in mouse models of HD, AD, and ALS, possibly contributing to cognitive impairment and neuropathology.

“Astrocyte Ca2+ dynamics and network responses become aberrant in mouse models of HD53, AD54, and ALS55, possibly contributing to cognitive impairment and neuropathology43,53,56.”

• cites [53] Jiang, R., Diaz-Castro, B., Looger, L. L. & Khakh, B. S. Dysfunctional calcium and glutamate signaling in striatal astrocytes from Huntington’s disease model mice. J. Neurosci. 36, 3453–3470 (2016). sourcePartly supported

  The Significance Statement (p. 2) and Discussion (p. 16) support aberrant astrocyte Ca2+ signaling and altered circuit engagement in HD model mice. The paper suggests these changes may contribute to altered striatal function, but it does not establish a contribution to cognitive impairment; the Discussion (p. 17) says a mechanism linking the cellular findings to HD symptoms remains unresolved. The AD and ALS portions of the citing sentence have separate citations and are not attributed to this source. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [54] Kuchibhotla, K. V., Lattarulo, C. R., Hyman, B. T. & Bacskai, B. J. Synchronous hyperactivity and intercellular calcium waves in astrocytes in Alzheimer mice. Science 323, 1211–1215 (2009). sourceSupported
• cites [55] Agarwal, A. et al. Transient opening of the mitochondrial permeability transition pore induces microdomain calcium transients in astrocyte processes. Neuron 93, 587–605.e7 (2017). Technically refined application of Ca2+ imaging approaches and machine learning unraveled dysregulation of Ca2+ responses in a mouse model of ALS. sourceSupported

May combine two claims.

Transcriptomic studies suggested complex functional changes in reactive astrocytes, including novel regenerative functions, proliferation, neural stem cell potential, and loss of homeostatic functions.

“These studies also suggested complex functional changes in reactive astrocytes, including novel regenerative functions70, proliferation, and neural stem cell potential68, as well as loss of homeostatic functions66.”

• cites [70] Itoh, N. et al. Cell-specific and region-specific transcriptomics in the multiple sclerosis model: Focus on astrocytes. Proc. Natl Acad. Sci. USA 115, E302–E309 (2018). sourceSupported
• cites [68] Sirko, S. et al. Astrocyte reactivity after brain injury-: The role of galectins 1 and 3. Glia 63, 2340–2361 (2015). sourceSupported
• cites [66] Zamanian, J. L. et al. Genomic analysis of reactive astrogliosis. J. Neurosci. 32, 6391–6410 (2012). First evidence for molecular heterogeneity of reactive astrocytes using microarray-based transcriptomics of acutely isolated astrocytes from mouse models of ischemia and septic shock. Studies in virtually all models of CNS diseases followed. sourceCould not verify

  Citation 66 is attached to the claim that reactive astrocytes lose homeostatic functions. The Discussion describes extensive gene-expression changes and identifies transporters and channels involved in homeostasis, but does not say that homeostatic functions are lost. Searches for loss of homeostatic function and down-regulation of homeostatic genes found no passage establishing that point. (LLM, conf=0.73)

  Experimental — accuracy not yet measured

May combine two claims.

Activation of STAT3-dependent transcription is beneficial in neonatal white matter injury, traumatic brain injury, spinal cord injury, and motor neuron injury, but detrimental in AD models.

“For example, activation of STAT3-dependent transcription is beneficial in neonatal white matter injury47, traumatic brain injury30, spinal cord injury48,49, and motor neuron injury50, but detrimental in AD models42,43.”

• cites [47] Nobuta, H. et al. STAT3-mediated astrogliosis protects myelin development in neonatal brain injury. Ann. Neurol. 72, 750–765 (2012). sourceSupported
• cites [30] Levine, J. et al. Traumatically injured astrocytes release a proteomic signature modulated by STAT3-dependent cell survival. Glia 64, 668–694 (2016). sourcePartly supported

  The Results section ('Acute STAT3 activation is important for cell integrity and apoptosis after astrocyte injury'; page unavailable) reports that STAT3-deficient astrocytes survived mechanical stretching less well than controls. The paper also reports protective effects after spinal cord injury, but the cited evidence does not establish a benefit of STAT3-dependent transcription in traumatic brain injury specifically. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [48] Anderson, M. A. et al. Astrocyte scar formation aids central nervous system axon regeneration. Nature 532, 195–200 (2016). sourceSupported
• cites [49] Herrmann, J. E. et al. STAT3 is a critical regulator of astrogliosis and scar formation after spinal cord injury. J. Neurosci. 28, 7231–7243 (2008). sourceSupported

May combine two claims.

Responses of reactive astrocytes may be maladaptive and result in malfunctional astrocytes, which, in addition to losing homeostatic functions, may gain detrimental functions, thus exacerbating ongoing pathology.

“Lastly, responses of reactive astrocytes may be maladaptive and result in malfunctional astrocytes, which, in addition to losing homeostatic functions, may also gain detrimental functions, thus exacerbating ongoing pathology6.”

• cites [6] Escartin, C., Guillemaud, O. & Carrillo-de Sauvage, M. A. Questions and (some) answers on reactive astrocytes. Glia 67, 2221–2247 (2019). sourceCould not verify

  The indexed passages are a HAL repository listing and site navigation, with no section or page of the paper’s substantive text. Searches for maladaptive responses, loss of homeostatic functions, detrimental functions, and worsening pathology returned no passage addressing the claim. (LLM, conf=0.72)

  Experimental — accuracy not yet measured

May combine two claims.

hiPSC-derived astrocytes are rapidly becoming commonplace in basic research and therapy development.

“are rapidly becoming commonplace in basic research11,82 and therapy development109”

• cites [11] Lin, Y. T. et al. APOE4 causes widespread molecular and cellular alterations associated with Alzheimer’s disease phenotypes in human iPSC-derived brain cell types. Neuron 98, 1141–1154.e7 (2018). Technically improved generation of hiPSC-derived astrocytes demonstrates that astrocytes harboring a genetic risk factor for AD are diseased astrocytes that may further exacerbate ongoing pathology. sourceSupported
• cites [82] Tyzack, G. E. et al. A neuroprotective astrocyte state is induced by neuronal signal EphB1 but fails in ALS models. Nat. Commun. 8, 1164 (2017). sourcePartly supported

  The Methods describe experiments with hiPSC-derived astrocytes, and the Discussion says human iPSC models can help identify astrocytic targets for potential treatment. This supports their relevance to therapy development, but the paper does not establish that their use is rapidly becoming commonplace. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [109] Colombo, E. et al. Siponimod (BAF312) activates Nrf2 while hampering NFκB in human astrocytes, and protects from astrocyte-induced neurodegeneration. Front. Immunol. 11, 635 (2020). sourcePartly supported

  The Results section (“Generation and Characterization of Human iAstrocytes”; page unavailable) shows that the authors generated hiPSC-derived astrocytes as a research model, and the Methods show their use in testing siponimod. This provides an example relevant to basic research and therapy investigation, but the paper does not establish that such use is rapidly becoming commonplace. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

May combine two claims.

hiPSC-derived astrocytes can be generated with a fast protocol in 2D layers or integrated in 3D systems such as spheroids and organoids.

“hiPSC-derived astrocytes, which can be generated with a fast protocol in 2D layers104 or integrated in 3D systems such as spheroids and organoids105–108”

• cites [104] Tchieu, J. et al. NFIA is a gliogenic switch enabling rapid derivation of functional human astrocytes from pluripotent stem cells. Nat. Biotechnol. 37, 267–275 (2019). sourceSupported
• cites [105] Sloan, S. A. et al. Human astrocyte maturation captured in 3D cerebral cortical spheroids derived from pluripotent stem cells. Neuron 95, 779–790.e6 (2017). sourceSupported
• cites [106] Lancaster, M. A. et al. Cerebral organoids model human brain development and microcephaly. Nature 501, 373–379 (2013). sourcePartly supported

  The Results section (‘Generation of cerebral organoids’; page unavailable) reports 3D cerebral organoids generated from human induced pluripotent stem cells. It does not report hiPSC-derived astrocytes being integrated into those organoids or into spheroids. The fast 2D protocol is attached to a different citation and is not assessed here. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [107] Quadrato, G. et al. Cell diversity and network dynamics in photosensitive human brain organoids. Nature 545, 48–53 (2017). sourceSupported
• cites [108] Giandomenico, S. L. et al. Cerebral organoids at the air-liquid interface generate diverse nerve tracts with functional output. Nat. Neurosci. 22, 669–679 (2019). sourcePartly supported

  The Results section (‘Air-liquid interface culture of cerebral organoids leads to improved survival and maturation’; page unavailable) reports astrocytes in cerebral organoids, supporting the 3D-organoid part of the cited claim. The Methods section (‘Human pluripotent stem cell culture and genome editing’; page unavailable) specifies that the organoids were generated from human embryonic stem cells, not hiPSCs. The fast 2D protocol is attached to a different citation and is not assessed here. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

May combine two claims.

Emerging reactive-astrocyte biomarkers are either measured in blood or cerebrospinal fluid (for example, YKL-40) or used for brain imaging, such as MAO-B-based positron emission tomography (PET).

“Emerging reactive-astrocyte biomarkers are either measured in blood or cerebrospinal fluid (for example, YKL-40)115 or used for brain imaging, such as MAO-B-based positron emission tomography (PET)116”

• cites [115] Craig-Schapiro, R. et al. YKL-40: a novel prognostic fluid biomarker for preclinical Alzheimer’s disease. Biol. Psychiatry 68, 903–912 (2010). sourceSupported
• cites [116] Carter, S. F. et al. Evidence for astrocytosis in prodromal Alzheimer disease provided by 11C-deuterium-L-deprenyl: a multitracer PET paradigm combining 11C-Pittsburgh compound B and 18F-FDG. J. Nucl. Med. 53, 37–46 (2012). Non-invasive imaging of reactive astrocytes in human patients. sourceNot checked — no full text of the source

May combine two claims.

Optogenetics and DREADDs are potential tools to manipulate reactive astrocytes or to restore their aberrant Ca2+ signaling observed in mouse models of neurodegenerative diseases.

“Optogenetics25 and designer receptors exclusively activated by designer drugs (DREADDs)25 are potential tools to manipulate reactive astrocytes or to restore their aberrant Ca2+ signaling observed in mouse models of neurodegenerative diseases53–55.”

• cites [25] Yu, X., Nagai, J. & Khakh, B. S. Improved tools to study astrocytes. Nat. Rev. Neurosci. 21, 121–138 (2020). sourceNot checked — no full text of the source
• cites [53] Jiang, R., Diaz-Castro, B., Looger, L. L. & Khakh, B. S. Dysfunctional calcium and glutamate signaling in striatal astrocytes from Huntington’s disease model mice. J. Neurosci. 36, 3453–3470 (2016). sourceSupported
• cites [54] Kuchibhotla, K. V., Lattarulo, C. R., Hyman, B. T. & Bacskai, B. J. Synchronous hyperactivity and intercellular calcium waves in astrocytes in Alzheimer mice. Science 323, 1211–1215 (2009). sourceSupported
• cites [55] Agarwal, A. et al. Transient opening of the mitochondrial permeability transition pore induces microdomain calcium transients in astrocyte processes. Neuron 93, 587–605.e7 (2017). Technically refined application of Ca2+ imaging approaches and machine learning unraveled dysregulation of Ca2+ responses in a mouse model of ALS. sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

Diversity within astrocyte populations from mouse models may be dissected by combining FACS and cell-surface markers identified in screens.

“Alternatively, the diversity within astrocyte populations from mouse models may be dissected out by combining fluorescence-activated cell sorting (FACS) and cell-surface markers identified in screens71.”

• cites [71] John Lin, C. C. et al. Identification of diverse astrocyte populations and their malignant analogs. Nat. Neurosci. 20, 396–405 (2017). sourceSupported

May combine two claims.

Immunohistochemical staining for cytosolic enzymes such as ALDH1L1, ALDOC, GS, and S100B allows visualization of the somata and proximal processes of astrocytes, although these markers fail to reveal small processes.

“Immunohistochemical staining for cytosolic enzymes such as ALDH1L1, ALDOC, GS, and S100B allow the visualization of the somata and proximal processes of astrocytes, although, like GFAP, these markers fail to reveal small processes.”

May combine two claims.

In the healthy mouse brain, hippocampal astrocytes have a higher GFAP content than cortical, thalamic, or striatal astrocytes, but this does not make hippocampal astrocytes more reactive.

“In the healthy mouse brain, hippocampal astrocytes have a higher GFAP content than cortical, thalamic, or striatal astrocytes; this, however, does not make hippocampal astrocytes more reactive.”

Probably not a substantial claim: may not pass S4 (based).

There are discrepancies between observed GFAP mRNA and protein levels, perhaps due to differential regulation of translation, post-translational modifications, protein half-life, and antibody epitope accessibility.

“Finally, there are discrepancies between observed GFAP mRNA and protein levels, perhaps due to differential regulation of translation, post-translational modifications, protein half-life, and antibody epitope accessibility.”

Classified as probably not a substantial claim. May combine two claims.

Astrocyte reactivity is secondary to an extrinsic signal, may evolve with time, and in many situations is reversible.

“By definition, astrocyte reactivity is secondary to an extrinsic signal, may evolve with time, and, in many situations, is reversible.”

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based). May combine two claims.

Numerous mixed scenarios of malfunctional and resilient astrocytes plausibly exist, with multidirectional transitions among them.

“Numerous mixed scenarios of malfunctional and resilient astrocytes plausibly exist, with multidirectional transitions among them.”

May combine two claims.

GFAP upregulation and hypertrophy are useful but insufficient markers of astrocyte reactivity that need to be complemented by additional markers.

“In summary, GFAP upregulation and hypertrophy are useful but insufficient markers of astrocyte reactivity that need to be complemented by additional markers (Table 1 and Box 1).”

May combine two claims.

Isolation protocols may not always be optimal for astrocytes, resulting in low numbers of cells or nuclei being sequenced, and some highly relevant but weakly expressed transcripts may be overlooked, particularly in snRNAseq.

“Notably, isolation protocols may not always be optimal for astrocytes, resulting in low numbers of cells or nuclei being sequenced, and some highly relevant but weakly expressed transcripts, such as transcription factors and plasma-membrane receptors, may be overlooked, particularly in snRNAseq.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Generation of astrocytes from neural stem cells is inherently difficult, and derivation and culture conditions have not yet been standardized, leading to diversity of clone phenotypes.

“In addition, generation of astrocytes from neural stem cells is inherently difficult, and derivation and culture conditions have not yet been standardized, leading to diversity of clone phenotypes.”

Probably not a substantial claim: may not pass S2 (checkable).

Vague and binary terms such as neuroprotective or neurotoxic are best avoided in describing astrocyte phenotypes as they are too simplistic to be meaningful, unless supported by specific molecular mechanisms and direct causative experimental evidence.

“In addition, vague and binary terms such as ‘neuroprotective’ or ‘neurotoxic’ are best avoided in describing astrocyte phenotypes as they are too simplistic to be meaningful, unless they are suppor ted by specific molecular mechanisms and direct causative experi mental evidence.”

May combine two claims.

Although astrocytes appear more resistant than neurons to degeneration and death, loss of primary and secondary astrocyte branches has been reported in mouse models of AD and ALS, and in patients with multiple sclerosis.

“In addition, although astrocytes appear to be more resistant than neurons to degeneration and death, loss of primary and secondary astrocyte branches has been reported in mouse models of AD27 and ALS18, and in patients with multiple sclerosis (MS)28.”

• cites [27] Olabarria, M., Noristani, H. N., Verkhratsky, A. & Rodríguez, J. J. Concomitant astroglial atrophy and astrogliosis in a triple transgenic animal model of Alzheimer’s disease. Glia 58, 831–838 (2010). sourceNot checked — no full text of the source
• cites [18] Rossi, D. et al. Focal degeneration of astrocytes in amyotrophic lateral sclerosis. Cell Death Differ. 15, 1691–1700 (2008). sourceNot checked — no full text of the source
• cites [28] Black, J. A., Newcombe, J. & Waxman, S. G. Astrocytes within multiple sclerosis lesions upregulate sodium channel Nav1.5. Brain 133, 835–846 (2010). sourceNot checked — no full text of the source

May combine two claims.

STAT3-mediated transcriptional programs may contribute to malfunctional astrocyte states in AD models and to resilient states in other conditions.

“That is, STAT3-mediated transcriptional programs may contribute to malfunctional astrocyte states in AD models and to resilient states in other conditions.”

Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

The term homeostatic astrocytes implies the unproven assumption that other transcriptional astrocyte clusters are dys-homeostatic, while they may be successful homeostasis-preserving adaptations to disease.

“In addition, the term ‘homeostatic astrocytes’ implies the unproven assumption that other transcriptional astrocyte clusters are dys-homeostatic, while they may be successful homeostasis-preserving adaptations to disease.”

Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

Healthy brain aging is not pathological and may be defined as an adaptive evolution of global cell physiology over time.

“Healthy brain aging is not pathological and may be defined as an adaptive evolution of global cell physiology over time85.”

• cites [85] Rodríguez-Arellano, J. J., Parpura, V., Zorec, R. & Verkhratsky, A. Astrocytes in physiological aging and Alzheimer’s disease. Neuroscience 323, 170–182 (2016). sourceNot checked — no full text of the source

May combine two claims.

New names are needed to capture the variety of reactive astrocytes, but current knowledge does not yet allow the objective categorizing of reactive astrocytes.

“Arguably, new names are needed to capture the variety of reactive astrocytes, but current knowledge does not yet allow the objective categorizing of reactive astrocytes.”

May combine two claims.

The morphological appearance of astrocytes does not correlate with functional phenotypes or with their impact on other cell types.

“An important conclusion drawn from these studies is that the morphological appearance of astrocytes does not correlate with functional phenotypes or with their impact on other cell types.”

Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

Expression in full or in part of a predetermined correlative signature of molecular markers is not, on its own, sufficient to define a functional phenotype of reactive astrocyte.

“We stress that the expression in full or in part of a predetermined correlative signature of molecular markers is not, on its own, sufficient to define a functional phenotype of reactive astrocyte.”

Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

Molecular signatures based on expression of genes or proteins need to be validated by assessing specific astrocyte functions, since post-transcriptional and post-translational events critically shape functional outcomes.

“Importantly, molecular signatures based on the expression of genes or proteins need to be validated by assessing specific astrocyte functions (Table 2), since post-transcriptional and post-translational events critically shape functional outcomes.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Acute metabolic damage with the mitochondrial toxin MPTP does not replicate chronic Parkinson's disease.

“Acute metabolic damage with the mitochondrial toxin MPTP does not replicate chronic Parkinson’s disease (PD), to cite another example of in vivo inappropriate modelling.”