The prevailing motor neuron-centric view of amyotrophic lateral sclerosis (ALS) pathogenesis could be an important factor in the failure to identify disease-modifying therapy for this neurodegenerative disorder. Non-neuronal cells have crucial homeostatic functions within the CNS and evidence of involvement of these cells in the pathophysiology of several neurodegenerative disorders, including ALS, is accumulating. Microglia and astrocytes, in crosstalk with peripheral immune cells, can exert both neuroprotective and adverse effects, resulting in a highly nuanced range of neuronal and non-neuronal cell interactions. This Review provides an overview of the diverse roles of non-neuronal cells in relation to the pathogenesis of ALS and the emerging potential of non-neuronal cell biomarkers to advance therapeutic development.
Accumulating evidence suggests that an exclusively motor neuron-centred model of pathogenesis in amyotrophic lateral sclerosis (ALS) is untenable, with important implications for therapeutic development strategies.
Brain-resident microglia, astrocytes and oligodendrocytes as well as peripheral immune cells all have vital functions in CNS homeostasis and physiology.
In multiple experimental models of ALS, non-neuronal cells seem to exert neurotoxic effects via both gain-of-function and loss-of-function mechanisms but also apparently show neuroprotective activity at certain disease stages.
Many of the hypotheses surrounding the roles of non-neuronal cells in ALS pathogenesis were developed using rodent models, some of which have limited relevance to the TDP43 neuropathological hallmark of human ALS.
Human induced pluripotent stem cells permit the investigation of non-neuronal cells carrying ALS-associated genetic mutations, but multicellular co-cultures might be needed to disentangle their nuanced interactions with motor neurons.
Human biofluid biomarkers derived from non-neuronal cells offer an important window into the in vivo pathological milieu and show potential as early markers of therapeutic response.
Subscribe to Journal
Get full journal access for 1 year
only $4.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Talbot, K., Feneberg, E., Scaber, J., Thompson, A. G. & Turner, M. R. Amyotrophic lateral sclerosis: the complex path to precision medicine. J. Neurol. 265, 2454–2462 (2018).
Al-Chalabi, A., van den Berg, L. H. & Veldink, J. Gene discovery in amyotrophic lateral sclerosis: implications for clinical management. Nat. Rev. Neurol. 13, 96–104 (2017).
Renton, A. E., Chio, A. & Traynor, B. J. State of play in amyotrophic lateral sclerosis genetics. Nat. Neurosci. 17, 17–23 (2014).
DeJesus-Hernandez, M. et al. Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS. Neuron 72, 245–256 (2011).
Rosen, D. R. et al. Mutations in Cu/Zn superoxide dismutase gene are associated with familial amyotrophic lateral sclerosis. Nature 362, 59–62 (1993).
Sreedharan, J. et al. TDP-43 mutations in familial and sporadic amyotrophic lateral sclerosis. Science 319, 1668–1672 (2008).
Vance, C. et al. Mutations in FUS, an RNA processing protein, cause familial amyotrophic lateral sclerosis type 6. Science 323, 1208–1211 (2009).
Neumann, M. et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science 314, 130–133 (2006).
Brown, R. H. Jr & Al-Chalabi, A. Amyotrophic lateral sclerosis. N. Engl. J. Med. 377, 1602 (2017).
Thompson, A. G. et al. Cerebrospinal fluid macrophage biomarkers in amyotrophic lateral sclerosis. Ann. Neurol. 83, 258–268 (2018).
von Bartheld, C. S., Bahney, J. & Herculano-Houzel, S. The search for true numbers of neurons and glial cells in the human brain: a review of 150 years of cell counting. J. Comp. Neurol. 524, 3865–3895 (2016).
Jakel, S. & Dimou, L. Glial cells and their function in the adult brain: a journey through the history of their ablation. Front. Cell Neurosci. 11, 24 (2017).
Allen, N. J. & Lyons, D. A. Glia as architects of central nervous system formation and function. Science 362, 181–185 (2018).
Greenhalgh, A. D., David, S. & Bennett, F. C. Immune cell regulation of glia during CNS injury and disease. Nat. Rev. Neurosci. 21, 139–152 (2020).
Pelvig, D. P., Pakkenberg, H., Stark, A. K. & Pakkenberg, B. Neocortical glial cell numbers in human brains. Neurobiol. Aging 29, 1754–1762 (2008).
Alliot, F., Godin, I. & Pessac, B. Microglia derive from progenitors, originating from the yolk sac, and which proliferate in the brain. Brain Res. Dev. Brain Res 117, 145–152 (1999).
Ginhoux, F. et al. Fate mapping analysis reveals that adult microglia derive from primitive macrophages. Science 330, 841–845 (2010).
Bruttger, J. et al. Genetic cell ablation reveals clusters of local self-renewing microglia in the mammalian central nervous system. Immunity 43, 92–106 (2015).
Kettenmann, H., Hanisch, U. K., Noda, M. & Verkhratsky, A. Physiology of microglia. Physiol. Rev. 91, 461–553 (2011).
Nimmerjahn, A., Kirchhoff, F. & Helmchen, F. Resting microglial cells are highly dynamic surveillants of brain parenchyma in vivo. Science 308, 1314–1318 (2005).
Li, Q. & Barres, B. A. Microglia and macrophages in brain homeostasis and disease. Nat. Rev. Immunol. 18, 225–242 (2018).
Butovsky, O. & Weiner, H. L. Microglial signatures and their role in health and disease. Nat. Rev. Neurosci. 19, 622–635 (2018).
Ransohoff, R. M. A polarizing question: do M1 and M2 microglia exist? Nat. Neurosci. 19, 987–991 (2016).
Mantovani, A., Sica, A. & Locati, M. Macrophage polarization comes of age. Immunity 23, 344–346 (2005).
Hu, X. et al. Microglial and macrophage polarization-new prospects for brain repair. Nat. Rev. Neurol. 11, 56–64 (2015).
Ashford, B. A. et al. Review: microglia in motor neuron disease. Neuropathol. Appl. Neurobiol. 47, 179–197 (2021).
Tang, Y. & Le, W. Differential roles of M1 and M2 microglia in neurodegenerative diseases. Mol. Neurobiol. 53, 1181–1194 (2016).
Cherry, J. D., Olschowka, J. A. & O’Banion, M. K. Neuroinflammation and M2 microglia: the good, the bad, and the inflamed. J. Neuroinflammation 11, 98 (2014).
Vass, K. & Lassmann, H. Intrathecal application of interferon gamma. Progressive appearance of MHC antigens within the rat nervous system. Am. J. Pathol. 137, 789–800 (1990).
Colonna, M. & Butovsky, O. Microglia function in the central nervous system during health and neurodegeneration. Annu. Rev. Immunol. 35, 441–468 (2017).
Turner, M. R. et al. Evidence of widespread cerebral microglial activation in amyotrophic lateral sclerosis: an [11C](R)-PK11195 positron emission tomography study. Neurobiol. Dis. 15, 601–609 (2004).
Zurcher, N. R. et al. Increased in vivo glial activation in patients with amyotrophic lateral sclerosis: assessed with [(11)C]-PBR28. Neuroimage Clin. 7, 409–414 (2015).
Tondo, G. et al. 11C-PK11195 PET-based molecular study of microglia activation in SOD1 amyotrophic lateral sclerosis. Ann. Clin. Transl. Neurol. 7, 1513–1523 (2020).
Henkel, J. S. et al. Presence of dendritic cells, MCP-1, and activated microglia/macrophages in amyotrophic lateral sclerosis spinal cord tissue. Ann. Neurol. 55, 221–235 (2004).
Brettschneider, J. et al. Microglial activation correlates with disease progression and upper motor neuron clinical symptoms in amyotrophic lateral sclerosis. PLoS ONE 7, e39216 (2012).
Brettschneider, J. et al. Microglial activation and TDP-43 pathology correlate with executive dysfunction in amyotrophic lateral sclerosis. Acta Neuropathol. 123, 395–407 (2012).
Verkhratsky, A. & Nedergaard, M. Physiology of astroglia. Physiol. Rev. 98, 239–389 (2018).
Kriegstein, A. & Alvarez-Buylla, A. The glial nature of embryonic and adult neural stem cells. Annu. Rev. Neurosci. 32, 149–184 (2009).
Vainchtein, I. D. & Molofsky, A. V. Astrocytes and microglia: in sickness and in health. Trends Neurosci. 43, 144–154 (2020).
Zamanian, J. L. et al. Genomic analysis of reactive astrogliosis. J. Neurosci. 32, 6391–6410 (2012).
Sofroniew, M. V. & Vinters, H. V. Astrocytes: biology and pathology. Acta Neuropathol. 119, 7–35 (2010).
Liddelow, S. A. et al. Neurotoxic reactive astrocytes are induced by activated microglia. Nature 541, 481–487 (2017).
Miller, S. J. Astrocyte heterogeneity in the adult central nervous system. Front. Cell Neurosci. 12, 401 (2018).
Clarke, L. E. et al. Normal aging induces A1-like astrocyte reactivity. Proc. Natl Acad. Sci. USA 115, E1896–E1905 (2018).
Liddelow, S. A. & Barres, B. A. Reactive astrocytes: production, function, and therapeutic potential. Immunity 46, 957–967 (2017).
Kawamata, T., Akiyama, H., Yamada, T. & McGeer, P. L. Immunologic reactions in amyotrophic lateral sclerosis brain and spinal cord tissue. Am. J. Pathol. 140, 691–707 (1992).
Tam, O. H. et al. Postmortem cortex samples identify distinct molecular subtypes of ALS: retrotransposon activation, oxidative stress, and activated glia. Cell Rep. 29, 1164–1177.e5 (2019).
Schiffer, D., Cordera, S., Cavalla, P. & Migheli, A. Reactive astrogliosis of the spinal cord in amyotrophic lateral sclerosis. J. Neurol. Sci. 139, 27–33 (1996).
Nagy, D., Kato, T. & Kushner, P. D. Reactive astrocytes are widespread in the cortical gray matter of amyotrophic lateral sclerosis. J. Neurosci. Res. 38, 336–347 (1994).
Kushner, P. D., Stephenson, D. T. & Wright, S. Reactive astrogliosis is widespread in the subcortical white matter of amyotrophic lateral sclerosis brain. J. Neuropathol. Exp. Neurol. 50, 263–277 (1991).
Johansson, A. et al. Evidence for astrocytosis in ALS demonstrated by [11C](L)-deprenyl-D2 PET. J. Neurol. Sci. 255, 17–22 (2007).
Valerio-Gomes, B., Guimaraes, D. M., Szczupak, D. & Lent, R. The absolute number of oligodendrocytes in the adult mouse brain. Front. Neuroanat. 12, 90 (2018).
Bergles, D. E. & Richardson, W. D. Oligodendrocyte development and plasticity. Cold Spring Harb. Perspect. Biol. 8, a020453 (2015).
Philips, T. & Rothstein, J. D. Oligodendroglia: metabolic supporters of neurons. J. Clin. Invest. 127, 3271–3280 (2017).
Michalski, J. P. & Kothary, R. Oligodendrocytes in a nutshell. Front. Cell Neurosci. 9, 340 (2015).
Zhang, S. Z. et al. NG2 glia regulate brain innate immunity via TGF-beta2/TGFBR2 axis. BMC Med. 17, 204 (2019).
Nolan, M. et al. Quantitative patterns of motor cortex proteinopathy across ALS genotypes. Acta Neuropathol. Commun. 8, 98 (2020).
Kierdorf, K., Masuda, T., Jordao, M. J. C. & Prinz, M. Macrophages at CNS interfaces: ontogeny and function in health and disease. Nat. Rev. Neurosci. 20, 547–562 (2019).
Prinz, M., Erny, D. & Hagemeyer, N. Ontogeny and homeostasis of CNS myeloid cells. Nat. Immunol. 18, 385–392 (2017).
Galea, I. et al. An antigen-specific pathway for CD8 T cells across the blood-brain barrier. J. Exp. Med. 204, 2023–2030 (2007).
Hickey, W. F., Hsu, B. L. & Kimura, H. T-lymphocyte entry into the central nervous system. J. Neurosci. Res. 28, 254–260 (1991).
Engelhardt, B., Vajkoczy, P. & Weller, R. O. The movers and shapers in immune privilege of the CNS. Nat. Immunol. 18, 123–131 (2017).
Daar, A. S., Fuggle, S. V., Fabre, J. W., Ting, A. & Morris, P. J. The detailed distribution of MHC Class II antigens in normal human organs. Transplantation 38, 293–298 (1984).
Jarmin, S. J. et al. T cell receptor-induced phosphoinositide-3-kinase p110delta activity is required for T cell localization to antigenic tissue in mice. J. Clin. Invest. 118, 1154–1164 (2008).
David, R. et al. T-cell receptor- and CD28-induced Vav1 activity is required for the accumulation of primed T cells into antigenic tissue. Blood 113, 3696–3705 (2009).
Garofalo, S. et al. Natural killer cells modulate motor neuron-immune cell cross talk in models of amyotrophic lateral sclerosis. Nat. Commun. 11, 1773 (2020).
Gurney, M. E. et al. Motor neuron degeneration in mice that express a human Cu,Zn superoxide dismutase mutation. Science 264, 1772–1775 (1994).
Philips, T. & Rothstein, J. D. Rodent models of amyotrophic lateral sclerosis. Curr. Protoc. Pharmacol. 69, 5.67.1–5.67.21 (2015).
Turner, B. J. & Talbot, K. Transgenics, toxicity and therapeutics in rodent models of mutant SOD1-mediated familial ALS. Prog. Neurobiol. 85, 94–134 (2008).
Hall, E. D., Oostveen, J. A. & Gurney, M. E. Relationship of microglial and astrocytic activation to disease onset and progression in a transgenic model of familial ALS. Glia 23, 249–256 (1998).
Alexianu, M. E., Kozovska, M. & Appel, S. H. Immune reactivity in a mouse model of familial ALS correlates with disease progression. Neurology 57, 1282–1289 (2001).
Philips, T. & Robberecht, W. Neuroinflammation in amyotrophic lateral sclerosis: role of glial activation in motor neuron disease. Lancet Neurol. 10, 253–263 (2011).
Pramatarova, A., Laganière, J., Roussel, J., Brisebois, K. & Rouleau, G. A. Neuron-specific expression of mutant superoxide dismutase 1 in transgenic mice does not lead to motor impairment. J. Neurosci. 21, 3369–3374 (2001).
Lino, M. M., Schneider, C. & Caroni, P. Accumulation of SOD1 mutants in postnatal motoneurons does not cause motoneuron pathology or motoneuron disease. J. Neurosci. 22, 4825–4832 (2002).
Wang, L. et al. Restricted expression of mutant SOD1 in spinal motor neurons and interneurons induces motor neuron pathology. Neurobiol. Dis. 29, 400–408 (2008).
Jaarsma, D., Teuling, E., Haasdijk, E. D., De Zeeuw, C. I. & Hoogenraad, C. C. Neuron-specific expression of mutant superoxide dismutase is sufficient to induce amyotrophic lateral sclerosis in transgenic mice. J. Neurosci. 28, 2075–2088 (2008).
Beers, D. R. et al. Wild-type microglia extend survival in PU.1 knockout mice with familial amyotrophic lateral sclerosis. Proc. Natl Acad. Sci. USA 103, 16021–16026 (2006).
Ralph, G. S. et al. Silencing mutant SOD1 using RNAi protects against neurodegeneration and extends survival in an ALS model. Nat. Med. 11, 429–433 (2005).
Boillee, S. et al. Onset and progression in inherited ALS determined by motor neurons and microglia. Science 312, 1389–1392 (2006).
Liao, B., Zhao, W., Beers, D. R., Henkel, J. S. & Appel, S. H. Transformation from a neuroprotective to a neurotoxic microglial phenotype in a mouse model of ALS. Exp. Neurol. 237, 147–152 (2012).
Gravel, M. et al. IL-10 controls early microglial phenotypes and disease onset in ALS caused by misfolded superoxide dismutase 1. J. Neurosci. 36, 1031–1048 (2016).
Xiao, Q. et al. Mutant SOD1(G93A) microglia are more neurotoxic relative to wild-type microglia. J. Neurochem. 102, 2008–2019 (2007).
Zhao, W. et al. Extracellular mutant SOD1 induces microglial-mediated motoneuron injury. Glia 58, 231–243 (2010).
Weydt, P., Yuen, E. C., Ransom, B. R. & Moller, T. Increased cytotoxic potential of microglia from ALS-transgenic mice. Glia 48, 179–182 (2004).
Gowing, G., Dequen, F., Soucy, G. & Julien, J. P. Absence of tumor necrosis factor-alpha does not affect motor neuron disease caused by superoxide dismutase 1 mutations. J. Neurosci. 26, 11397–11402 (2006).
Meissner, F., Molawi, K. & Zychlinsky, A. Mutant superoxide dismutase 1-induced IL-1beta accelerates ALS pathogenesis. Proc. Natl Acad. Sci. USA 107, 13046–13050 (2010).
Nguyen, M. D., Julien, J. P. & Rivest, S. Induction of proinflammatory molecules in mice with amyotrophic lateral sclerosis: no requirement for proapoptotic interleukin-1beta in neurodegeneration. Ann. Neurol. 50, 630–639 (2001).
Chiu, I. M. et al. A neurodegeneration-specific gene-expression signature of acutely isolated microglia from an amyotrophic lateral sclerosis mouse model. Cell Rep. 4, 385–401 (2013).
Wegorzewska, I., Bell, S., Cairns, N. J., Miller, T. M. & Baloh, R. H. TDP-43 mutant transgenic mice develop features of ALS and frontotemporal lobar degeneration. Proc. Natl Acad. Sci. USA 106, 18809–18814 (2009).
Jara, J. H. et al. MCP1-CCR2 and neuroinflammation in the ALS motor cortex with TDP-43 pathology. J. Neuroinflammation 16, 196 (2019).
Zhao, W. et al. TDP-43 activates microglia through NF-kappaB and NLRP3 inflammasome. Exp. Neurol. 273, 24–35 (2015).
Deora, V. et al. The microglial NLRP3 inflammasome is activated by amyotrophic lateral sclerosis proteins. Glia 68, 407–421 (2020).
Leal-Lasarte, M. M., Franco, J. M., Labrador-Garrido, A., Pozo, D. & Roodveldt, C. Extracellular TDP-43 aggregates target MAPK/MAK/MRK overlapping kinase (MOK) and trigger caspase-3/IL-18 signaling in microglia. FASEB J. 31, 2797–2816 (2017).
Spiller, K. J. et al. Microglia-mediated recovery from ALS-relevant motor neuron degeneration in a mouse model of TDP-43 proteinopathy. Nat. Neurosci. 21, 329–340 (2018).
Svahn, A. J. et al. Nucleo-cytoplasmic transport of TDP-43 studied in real time: impaired microglia function leads to axonal spreading of TDP-43 in degenerating motor neurons. Acta Neuropathol. 136, 445–459 (2018).
Paolicelli, R. C. et al. TDP-43 depletion in microglia promotes amyloid clearance but also induces synapse loss. Neuron 95, 297–308.e6 (2017).
O’Rourke, J. G. et al. C9orf72 is required for proper macrophage and microglial function in mice. Science 351, 1324–1329 (2016).
Lall, D. & Baloh, R. H. Microglia and C9orf72 in neuroinflammation and ALS and frontotemporal dementia. J. Clin. Invest. 127, 3250–3258 (2017).
O’Rourke, J. G. et al. C9orf72 BAC transgenic mice display typical pathologic features of ALS/FTD. Neuron 88, 892–901 (2015).
Jiang, J. et al. Gain of toxicity from ALS/FTD-linked repeat expansions in c9orf72 is alleviated by antisense oligonucleotides targeting GGGGCC-containing RNAs. Neuron 90, 535–550 (2016).
Peters, O. M. et al. Human C9ORF72 hexanucleotide expansion reproduces RNA foci and dipeptide repeat proteins but not neurodegeneration in BAC transgenic mice. Neuron 88, 902–909 (2015).
Mackenzie, I. R. et al. Quantitative analysis and clinico-pathological correlations of different dipeptide repeat protein pathologies in C9ORF72 mutation carriers. Acta Neuropathol. 130, 845–861 (2015).
Zhou, Q. et al. Active poly-GA vaccination prevents microglia activation and motor deficits in a C9orf72 mouse model. EMBO Mol. Med. 12, e10919 (2020).
Schludi, M. H. et al. Spinal poly-GA inclusions in a C9orf72 mouse model trigger motor deficits and inflammation without neuron loss. Acta Neuropathol. 134, 241–254 (2017).
LaClair, K. D. et al. Congenic expression of poly-GA but not poly-PR in mice triggers selective neuron loss and interferon responses found in C9orf72 ALS. Acta Neuropathol. 140, 121–142 (2020).
Hao, Z. et al. Motor dysfunction and neurodegeneration in a C9orf72 mouse line expressing poly-PR. Nat. Commun. 10, 2906 (2019).
Choi, S. Y. et al. C9ORF72-ALS/FTD-associated poly(GR) binds Atp5a1 and compromises mitochondrial function in vivo. Nat. Neurosci. 22, 851–862 (2019).
Zhang, Y. J. et al. Poly(GR) impairs protein translation and stress granule dynamics in C9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis. Nat. Med. 24, 1136–1142 (2018).
Koppers, M. et al. C9orf72 ablation in mice does not cause motor neuron degeneration or motor deficits. Ann. Neurol. 78, 426–438 (2015).
Burberry, A. et al. Loss-of-function mutations in the C9ORF72 mouse ortholog cause fatal autoimmune disease. Sci. Transl. Med. 8, 347ra393 (2016).
Lagier-Tourenne, C. et al. Targeted degradation of sense and antisense C9orf72 RNA foci as therapy for ALS and frontotemporal degeneration. Proc. Natl Acad. Sci. USA 110, E4530–E4539 (2013).
Zhu, Q. et al. Reduced C9ORF72 function exacerbates gain of toxicity from ALS/FTD-causing repeat expansion in C9orf72. Nat. Neurosci. 23, 615–624 (2020).
Rostalski, H. et al. Astrocytes and microglia as potential contributors to the pathogenesis of C9orf72 repeat expansion-associated FTLD and ALS. Front. Neurosci. 13, 486 (2019).
Yamanaka, K. et al. Astrocytes as determinants of disease progression in inherited amyotrophic lateral sclerosis. Nat. Neurosci. 11, 251–253 (2008).
Gong, Y. H., Parsadanian, A. S., Andreeva, A., Snider, W. D. & Elliott, J. L. Restricted expression of G86R Cu/Zn superoxide dismutase in astrocytes results in astrocytosis but does not cause motoneuron degeneration. J. Neurosci. 20, 660–665 (2000).
Wang, L., Gutmann, D. H. & Roos, R. P. Astrocyte loss of mutant SOD1 delays ALS disease onset and progression in G85R transgenic mice. Hum. Mol. Genet. 20, 286–293 (2011).
Lepore, A. C. et al. Focal transplantation-based astrocyte replacement is neuroprotective in a model of motor neuron disease. Nat. Neurosci. 11, 1294–1301 (2008).
Papadeas, S. T., Kraig, S. E., O’Banion, C., Lepore, A. C. & Maragakis, N. J. Astrocytes carrying the superoxide dismutase 1 (SOD1G93A) mutation induce wild-type motor neuron degeneration in vivo. Proc. Natl Acad. Sci. USA 108, 17803–17808 (2011).
Nagai, M. et al. Astrocytes expressing ALS-linked mutated SOD1 release factors selectively toxic to motor neurons. Nat. Neurosci. 10, 615–622 (2007).
Di Giorgio, F. P., Carrasco, M. A., Siao, M. C., Maniatis, T. & Eggan, K. Non-cell autonomous effect of glia on motor neurons in an embryonic stem cell-based ALS model. Nat. Neurosci. 10, 608–614 (2007).
Di Giorgio, F. P., Boulting, G. L., Bobrowicz, S. & Eggan, K. C. Human embryonic stem cell-derived motor neurons are sensitive to the toxic effect of glial cells carrying an ALS-causing mutation. Cell Stem Cell 3, 637–648 (2008).
Marchetto, M. C. et al. Non-cell-autonomous effect of human SOD1 G37R astrocytes on motor neurons derived from human embryonic stem cells. Cell Stem Cell 3, 649–657 (2008).
Haidet-Phillips, A. M. et al. Astrocytes from familial and sporadic ALS patients are toxic to motor neurons. Nat. Biotechnol. 29, 824–828 (2011).
Phatnani, H. P. et al. Intricate interplay between astrocytes and motor neurons in ALS. Proc. Natl Acad. Sci. USA 110, E756–E765 (2013).
Ferraiuolo, L. et al. Dysregulation of astrocyte-motoneuron cross-talk in mutant superoxide dismutase 1-related amyotrophic lateral sclerosis. Brain 134, 2627–2641 (2011).
Vargas, M. R., Johnson, D. A., Sirkis, D. W., Messing, A. & Johnson, J. A. Nrf2 activation in astrocytes protects against neurodegeneration in mouse models of familial amyotrophic lateral sclerosis. J. Neurosci. 28, 13574–13581 (2008).
Pehar, M., Harlan, B. A., Killoy, K. M. & Vargas, M. R. Role and therapeutic potential of astrocytes in amyotrophic lateral sclerosis. Curr. Pharm. Des. 23, 5010–5021 (2017).
Yamanaka, K. & Komine, O. The multi-dimensional roles of astrocytes in ALS. Neurosci. Res. 126, 31–38 (2018).
Endo, F. et al. Astrocyte-derived TGF-β1 accelerates disease progression in ALS mice by interfering with the neuroprotective functions of microglia and T cells. Cell Rep. 11, 592–604 (2015).
Guttenplan, K. A. et al. Knockout of reactive astrocyte activating factors slows disease progression in an ALS mouse model. Nat. Commun. 11, 3753 (2020).
Mishra, V. et al. Systematic elucidation of neuron-astrocyte interaction in models of amyotrophic lateral sclerosis using multi-modal integrated bioinformatics workflow. Nat. Commun. 11, 5579 (2020).
Howland, D. S. et al. Focal loss of the glutamate transporter EAAT2 in a transgenic rat model of SOD1 mutant-mediated amyotrophic lateral sclerosis (ALS). Proc. Natl Acad. Sci. USA 99, 1604–1609 (2002).
Bruijn, L. I. et al. ALS-linked SOD1 mutant G85R mediates damage to astrocytes and promotes rapidly progressive disease with SOD1-containing inclusions. Neuron 18, 327–338 (1997).
Ditsworth, D. et al. Mutant TDP-43 within motor neurons drives disease onset but not progression in amyotrophic lateral sclerosis. Acta Neuropathol. 133, 907–922 (2017).
Tong, J. et al. Expression of ALS-linked TDP-43 mutant in astrocytes causes non-cell-autonomous motor neuron death in rats. EMBO J. 32, 1917–1926 (2013).
Velebit, J. et al. Astrocytes with TDP-43 inclusions exhibit reduced noradrenergic cAMP and Ca2+ signaling and dysregulated cell metabolism. Sci. Rep. 10, 6003 (2020).
Moujalled, D. et al. TDP-43 mutations causing amyotrophic lateral sclerosis are associated with altered expression of RNA-binding protein hnRNP K and affect the Nrf2 antioxidant pathway. Hum. Mol. Genet. 26, 1732–1746 (2017).
Rojas, F., Cortes, N., Abarzua, S., Dyrda, A. & van Zundert, B. Astrocytes expressing mutant SOD1 and TDP43 trigger motoneuron death that is mediated via sodium channels and nitroxidative stress. Front. Cell Neurosci. 8, 24 (2014).
Huang, C. et al. Profiling the genes affected by pathogenic TDP-43 in astrocytes. J. Neurochem. 129, 932–939 (2014).
Bi, F. et al. Reactive astrocytes secrete lcn2 to promote neuron death. Proc. Natl Acad. Sci. USA 110, 4069–4074 (2013).
Iguchi, Y. et al. Loss of TDP-43 causes age-dependent progressive motor neuron degeneration. Brain 136, 1371–1382 (2013).
Wu, L. S., Cheng, W. C. & Shen, C. K. Targeted depletion of TDP-43 expression in the spinal cord motor neurons leads to the development of amyotrophic lateral sclerosis-like phenotypes in mice. J. Biol. Chem. 287, 27335–27344 (2012).
Yang, C. et al. Partial loss of TDP-43 function causes phenotypes of amyotrophic lateral sclerosis. Proc. Natl Acad. Sci. USA 111, E1121–E1129 (2014).
LaRocca, T. J., Mariani, A., Watkins, L. R. & Link, C. D. TDP-43 knockdown causes innate immune activation via protein kinase R in astrocytes. Neurobiol. Dis. 132, 104514 (2019).
Kraemer, B. C. et al. Loss of murine TDP-43 disrupts motor function and plays an essential role in embryogenesis. Acta Neuropathol. 119, 409–419 (2010).
Chiang, P. M. et al. Deletion of TDP-43 down-regulates Tbc1d1, a gene linked to obesity, and alters body fat metabolism. Proc. Natl Acad. Sci. USA 107, 16320–16324 (2010).
Serio, A. et al. Astrocyte pathology and the absence of non-cell autonomy in an induced pluripotent stem cell model of TDP-43 proteinopathy. Proc. Natl Acad. Sci. USA 110, 4697–4702 (2013).
Haidet-Phillips, A. M. et al. Altered astrocytic expression of TDP-43 does not influence motor neuron survival. Exp. Neurol. 250, 250–259 (2013).
Smethurst, P. et al. Distinct responses of neurons and astrocytes to TDP-43 proteinopathy in amyotrophic lateral sclerosis. Brain 143, 430–440 (2020).
Chew, J. et al. Neurodegeneration. C9ORF72 repeat expansions in mice cause TDP-43 pathology, neuronal loss, and behavioral deficits. Science 348, 1151–1154 (2015).
Zhang, Y. J. et al. C9ORF72 poly(GA) aggregates sequester and impair HR23 and nucleocytoplasmic transport proteins. Nat. Neurosci. 19, 668–677 (2016).
Chew, J. et al. Aberrant deposition of stress granule-resident proteins linked to C9orf72-associated TDP-43 proteinopathy. Mol. Neurodegener. 14, 9 (2019).
Meyer, K. et al. Direct conversion of patient fibroblasts demonstrates non-cell autonomous toxicity of astrocytes to motor neurons in familial and sporadic ALS. Proc. Natl Acad. Sci. USA 111, 829–832 (2014).
Hautbergue, G. M. et al. SRSF1-dependent nuclear export inhibition of C9ORF72 repeat transcripts prevents neurodegeneration and associated motor deficits. Nat. Commun. 8, 16063 (2017).
Birger, A. et al. Human iPSC-derived astrocytes from ALS patients with mutated C9ORF72 show increased oxidative stress and neurotoxicity. EBioMedicine 50, 274–289 (2019).
Allen, S. P. et al. Astrocyte adenosine deaminase loss increases motor neuron toxicity in amyotrophic lateral sclerosis. Brain 142, 586–605 (2019).
Allen, S. P. et al. C9orf72 expansion within astrocytes reduces metabolic flexibility in amyotrophic lateral sclerosis. Brain 142, 3771–3790 (2019).
Fomin, V. et al. The C9ORF72 gene, implicated in amyotrophic lateral sclerosis and frontotemporal dementia, encodes a protein that functions in control of endothelin and glutamate signaling. Mol. Cell Biol. 38, e00155-18 (2018).
Varcianna, A. et al. Micro-RNAs secreted through astrocyte-derived extracellular vesicles cause neuronal network degeneration in C9orf72 ALS. EBioMedicine 40, 626–635 (2019).
Thompson, A. G. et al. Extracellular vesicles in neurodegenerative disease - pathogenesis to biomarkers. Nat. Rev. Neurol. 12, 346–357 (2016).
Zhao, C. et al. Mutant C9orf72 human iPSC-derived astrocytes cause non-cell autonomous motor neuron pathophysiology. Glia 68, 1046–1064 (2020).
Kang, S. H. et al. Degeneration and impaired regeneration of gray matter oligodendrocytes in amyotrophic lateral sclerosis. Nat. Neurosci. 16, 571–579 (2013).
Philips, T. et al. Oligodendrocyte dysfunction in the pathogenesis of amyotrophic lateral sclerosis. Brain 136, 471–482 (2013).
Yamanaka, K. et al. Mutant SOD1 in cell types other than motor neurons and oligodendrocytes accelerates onset of disease in ALS mice. Proc. Natl Acad. Sci. USA 105, 7594–7599 (2008).
Ferraiuolo, L. et al. Oligodendrocytes contribute to motor neuron death in ALS via SOD1-dependent mechanism. Proc. Natl Acad. Sci. USA 113, E6496–E6505 (2016).
Lee, Y. et al. Oligodendroglia metabolically support axons and contribute to neurodegeneration. Nature 487, 443–448 (2012).
Kim, S. et al. Myelin degeneration induced by mutant superoxide dismutase 1 accumulation promotes amyotrophic lateral sclerosis. Glia 67, 1910–1921 (2019).
Sun, S. et al. Translational profiling identifies a cascade of damage initiated in motor neurons and spreading to glia in mutant SOD1-mediated ALS. Proc. Natl Acad. Sci. USA 112, E6993–E7002 (2015).
Livesey, M. R. et al. Maturation and electrophysiological properties of human pluripotent stem cell-derived oligodendrocytes. Stem Cell 34, 1040–1053 (2016).
Butovsky, O. et al. Modulating inflammatory monocytes with a unique microRNA gene signature ameliorates murine ALS. J. Clin. Invest. 122, 3063–3087 (2012).
Zhao, W. et al. Characterization of gene expression phenotype in amyotrophic lateral sclerosis monocytes. JAMA Neurol. 74, 677–685 (2017).
Du, Y. et al. Increased activation ability of monocytes from ALS patients. Exp. Neurol. 328, 113259 (2020).
Zondler, L. et al. Peripheral monocytes are functionally altered and invade the CNS in ALS patients. Acta Neuropathol. 132, 391–411 (2016).
McCauley, M. E. et al. C9orf72 in myeloid cells suppresses STING-induced inflammation. Nature 585, 96–101 (2020).
Park, L. et al. Brain perivascular macrophages initiate the neurovascular dysfunction of Alzheimer Aβ peptides. Circ. Res. 121, 258–269 (2017).
Chiu, I. M. et al. T lymphocytes potentiate endogenous neuroprotective inflammation in a mouse model of ALS. Proc. Natl Acad. Sci. USA 105, 17913–17918 (2008).
Beers, D. R., Henkel, J. S., Zhao, W., Wang, J. & Appel, S. H. CD4+ T cells support glial neuroprotection, slow disease progression, and modify glial morphology in an animal model of inherited ALS. Proc. Natl Acad. Sci. USA 105, 15558–15563 (2008).
Beers, D. R. et al. Endogenous regulatory T lymphocytes ameliorate amyotrophic lateral sclerosis in mice and correlate with disease progression in patients with amyotrophic lateral sclerosis. Brain 134, 1293–1314 (2011).
Zhao, W., Beers, D. R., Liao, B., Henkel, J. S. & Appel, S. H. Regulatory T lymphocytes from ALS mice suppress microglia and effector T lymphocytes through different cytokine-mediated mechanisms. Neurobiol. Dis. 48, 418–428 (2012).
Beers, D. R. et al. ALS patients’ regulatory T lymphocytes are dysfunctional, and correlate with disease progression rate and severity. JCI Insight 2, e89530 (2017).
Henkel, J. S. et al. Regulatory T-lymphocytes mediate amyotrophic lateral sclerosis progression and survival. EMBO Mol. Med. 5, 64–79 (2013).
Sheean, R. K. et al. Association of regulatory T-cell expansion with progression of amyotrophic lateral sclerosis: a study of humans and a transgenic mouse model. JAMA Neurol. 75, 681–689 (2018).
Komine, O. et al. Innate immune adaptor TRIF deficiency accelerates disease progression of ALS mice with accumulation of aberrantly activated astrocytes. Cell Death Differ. 25, 2130–2146 (2018).
Nardo, G. et al. Counteracting roles of MHCI and CD8+ T cells in the peripheral and central nervous system of ALS SOD1(G93A) mice. Mol. Neurodegener. 13, 42 (2018).
Coque, E. et al. Cytotoxic CD8+ T lymphocytes expressing ALS-causing SOD1 mutant selectively trigger death of spinal motoneurons. Proc. Natl Acad. Sci. USA 116, 2312–2317 (2019).
Atanasio, A. et al. C9orf72 ablation causes immune dysregulation characterized by leukocyte expansion, autoantibody production, and glomerulonephropathy in mice. Sci. Rep. 6, 23204 (2016).
Zhao, W. et al. Immunosuppressive functions of M2 macrophages derived from iPSCs of patients with ALS and healthy controls. iScience 23, 101192 (2020).
Finkelstein, A. et al. Abnormal changes in NKT cells, the IGF-1 axis, and liver pathology in an animal model of ALS. PLoS ONE 6, e22374 (2011).
Murdock, B. J. et al. Correlation of peripheral immunity with rapid amyotrophic lateral sclerosis progression. JAMA Neurol. 74, 1446–1454 (2017).
Vijayakumar, U. G. et al. A systematic review of suggested molecular strata, biomarkers and their tissue sources in ALS. Front. Neurol. 10, 400 (2019).
Verber, N. & Shaw, P. J. Biomarkers in amyotrophic lateral sclerosis: a review of new developments. Curr. Opin. Neurol. 33, 662–668 (2020).
Varghese, A. M. et al. Chitotriosidase — a putative biomarker for sporadic amyotrophic lateral sclerosis. Clin. Proteom. 10, 19 (2013).
Steinacker, P. et al. Chitotriosidase (CHIT1) is increased in microglia and macrophages in spinal cord of amyotrophic lateral sclerosis and cerebrospinal fluid levels correlate with disease severity and progression. J. Neurol. Neurosurg. Psychiatry 89, 239–247 (2018).
Varghese, A. M. et al. Chitotriosidase, a biomarker of amyotrophic lateral sclerosis, accentuates neurodegeneration in spinal motor neurons through neuroinflammation. J. Neuroinflammation 17, 232 (2020).
Thompson, A. G. et al. CSF chitinase proteins in amyotrophic lateral sclerosis. J. Neurol. Neurosurg. Psychiatry 90, 1215–1220 (2019).
Gray, E. et al. CSF chitinases before and after symptom onset in amyotrophic lateral sclerosis. Ann. Clin. Transl. Neurol. 7, 1296–1306 (2020).
Oeckl, P. et al. Different neuroinflammatory profile in amyotrophic lateral sclerosis and frontotemporal dementia is linked to the clinical phase. J. Neurol. Neurosurg. Psychiatry 90, 4–10 (2019).
Gille, B. et al. Inflammatory markers in cerebrospinal fluid: independent prognostic biomarkers in amyotrophic lateral sclerosis? J. Neurol. Neurosurg. Psychiatry 90, 1338–1346 (2019).
Illan-Gala, I. et al. CSF sAPPβ, YKL-40, and NfL along the ALS-FTD spectrum. Neurology 91, e1619–e1628 (2018).
Abu-Rumeileh, S. et al. Diagnostic-prognostic value and electrophysiological correlates of CSF biomarkers of neurodegeneration and neuroinflammation in amyotrophic lateral sclerosis. J. Neurol. 267, 1699–1708 (2020).
Gaur, N., Perner, C., Witte, O. W. & Grosskreutz, J. The chitinases as biomarkers for amyotrophic lateral sclerosis: signals from the CNS and beyond. Front. Neurol. 11, 377 (2020).
Castellani, R. J., Perry, G. & Smith, M. A. The role of novel chitin-like polysaccharides in Alzheimer disease. Neurotox. Res. 12, 269–274 (2007).
Vu, L. et al. Cross-sectional and longitudinal measures of chitinase proteins in amyotrophic lateral sclerosis and expression of CHI3L1 in activated astrocytes. J. Neurol. Neurosurg. Psychiatry 91, 350–358 (2020).
Andres-Benito, P. et al. YKL40 in sporadic amyotrophic lateral sclerosis: cerebrospinal fluid levels as a prognosis marker of disease progression. Aging 10, 2367–2382 (2018).
Chen, Y., Xia, K., Chen, L. & Fan, D. Increased interleukin-6 levels in the astrocyte-derived exosomes of sporadic amyotrophic lateral sclerosis patients. Front. Neurosci. 13, 574 (2019).
Henkel, J. S., Beers, D. R., Siklos, L. & Appel, S. H. The chemokine MCP-1 and the dendritic and myeloid cells it attracts are increased in the mSOD1 mouse model of ALS. Mol. Cell Neurosci. 31, 427–437 (2006).
Huang, F. et al. Longitudinal biomarkers in amyotrophic lateral sclerosis. Ann. Clin. Transl. Neurol. 7, 1103–1116 (2020).
Kuhle, J. et al. Increased levels of inflammatory chemokines in amyotrophic lateral sclerosis. Eur. J. Neurol. 16, 771–774 (2009).
Guo, J., Yang, X., Gao, L. & Zang, D. Evaluating the levels of CSF and serum factors in ALS. Brain Behav. 7, e00637 (2017).
Lehnert, S. et al. Multicentre quality control evaluation of different biomarker candidates for amyotrophic lateral sclerosis. Amyotroph. Lateral Scler. Frontotemporal Degener. 15, 344–350 (2014).
Nagata, T. et al. Elevation of MCP-1 and MCP-1/VEGF ratio in cerebrospinal fluid of amyotrophic lateral sclerosis patients. Neurol. Res. 29, 772–776 (2007).
Wilms, H. et al. Intrathecal synthesis of monocyte chemoattractant protein-1 (MCP-1) in amyotrophic lateral sclerosis: further evidence for microglial activation in neurodegeneration. J. Neuroimmunol. 144, 139–142 (2003).
Kiernan, M. C. et al. Improving clinical trial outcomes in amyotrophic lateral sclerosis. Nat. Rev. Neurol. 17, 104–118 (2021).
Mora, J. S. et al. Masitinib as an add-on therapy to riluzole in patients with amyotrophic lateral sclerosis: a randomized clinical trial. Amyotroph. Lateral Scler. Frontotemporal Degener. 21, 5–14 (2020).
B. F. V. is funded by the University of Oxford Clarendon Fund, St John’s College Oxford, the Oxford–Medical Research Council (MRC) Doctoral Training Partnership, and the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre. E. G. is supported by the Motor Neurone Disease Association. A. G. T. is supported by the MRC and Motor Neurone Disease Association Lady Edith Wolfson Clinician Scientist Fellowship. S. A. C. is supported through the Oxford Martin School. M. R. T. is supported by the Motor Neurone Disease Association. The views expressed are those of the authors and not necessarily those of the National Health Service, the NIHR, or the Department of Health and Social Care.
The authors declare no competing interests.
Peer review information
Nature Reviews Neurology thanks L. Barbeito, S. Appel and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Vahsen, B.F., Gray, E., Thompson, A.G. et al. Non-neuronal cells in amyotrophic lateral sclerosis — from pathogenesis to biomarkers. Nat Rev Neurol 17, 333–348 (2021). https://doi.org/10.1038/s41582-021-00487-8