Cited by 1,968Neuroinflammation and Neurodegeneration MechanismsNeurogenesis and neuroplasticity mechanismsMultiple Sclerosis Research Studies

Colony-Stimulating Factor 1 Receptor Signaling Is Necessary for Microglia Viability, Unmasking a Microglia Progenitor Cell in the Adult Brain

Open access
Elmore, Monica R.P., Najafi, Allison R., Koike, Maya A., Dagher, Nabil N., Spangenberg, Elizabeth E., Rice, Rachel A., Kitazawa, Masashi, Matusow, Bernice +3 more·2014·Neuron

Abstract

The colony-stimulating factor 1 receptor (CSF1R) is a key regulator of myeloid lineage cells. Genetic loss of the CSF1R blocks the normal population of resident microglia in the brain that originates from the yolk sac during early development. However, the role of CSF1R signaling in microglial homeostasis in the adult brain is largely unknown. To this end, we tested the effects of selective CSF1R inhibitors on microglia in adult mice. Surprisingly, extensive treatment results in elimination of ∼99% of all microglia brain-wide, showing that microglia in the adult brain are physiologically dependent upon CSF1R signaling. Mice depleted of microglia show no behavioral or cognitive abnormalities, revealing that microglia are not necessary for these tasks. Finally, we discovered that the microglia-depleted brain completely repopulates with new microglia within 1 week of inhibitor cessation. Microglial repopulation throughout the CNS occurs through proliferation of nestin-positive cells that then differentiate into microglia.

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Registry

Crossref · 10.1016/j.neuron.2014.02.040

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45 of 45 references verified0 citation errors · 0 not checkable

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  • After inhibiting CSF-1R, the resident microglia display elevated proliferation and inflammation markers.

    “In addition, it was reported that after inhibiting CSF-1R, the resident microglia display elevated proliferation and inflammation markers (64, 65)”

    From Arresting the bad seed: HDAC3 regulates proliferation of different microglia after ischemic stroke (2024) · cites this paper as [65]

    In Results (‘CSF1R inhibitors dramatically reduce microglia numbers in the adult brain’; page unavailable), inhibition prevented an LPS-induced increase in the inflammatory marker IBA1 and markedly reduced microglial numbers. Results (‘Rapid restoration of CNS microglia following drug removal’; page unavailable) place the proliferation marker Ki67 in newly repopulating cells after inhibitor withdrawal, not in resident microglia during inhibition. (LLM, conf=0.88)

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  • Tgfbr2 and Csf1r play an essential signaling role in microglia development, with absence or inhibition causing marked reduction or complete absence of microglia.

    “Tgfbr2 and Csf1r have also been demonstrated to play an essential signaling role in microglia development, where the absence of these genes or inhibition of their signaling shows marked reduction or complete absence of microglia”

    From Cross-Species Single-Cell Analysis Reveals Divergence of the Primate Microglia Program (2019) · cites this paper as Elmore et al., 2014

    The Introduction (page not provided) says microglial development depends on CSF1R and that CSF1R-knockout mice are devoid of microglia. The Discussion reports that CSF1R inhibition eliminates virtually all microglia in the adult CNS. Our copy does not support the claim about Tgfbr2; searches for Tgfbr2 and transforming growth factor beta receptor 2 found no relevant passage. (LLM, conf=0.90)

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  • PLX treatment near completely eliminates microglia in the healthy brain after about 1 week, and cessation of PLX treatment is followed by a rapid rebound in microglia numbers after about 1 week.

    “Treatment with PLX is a highly effective and well tolerated strategy, with near complete elimination of microglia in the healthy brain after ~ 1 week. Cessation of PLX treatment is followed by a rapid (~ 1 week) rebound in microglia numbers.”

    From Activated microglia drive demyelination via <scp>CSF1R</scp> signaling (2021) · cites this paper as Monica R. P. Elmore et al., 2014

    The Results sections on early repopulation and rapid restoration report that microglia rebound after PLX3397 withdrawal, exceeding control numbers by seven days in aged mice. But the seven-day treatment experiment eliminated about 70% of microglia, not nearly all; the paper reports essentially microglia-devoid brains after 21 days of treatment. The claimed timing of near-complete elimination is therefore not supported. (LLM, conf=0.88)

    Experimental — accuracy not yet measured
  • Withdrawal of PLX5622 treatment results in rapid and robust repopulation of microglia via self-renewal.

    “Withdrawal of PLX5622 treatment is known to result in a rapid and robust repopulation of microglia via self-renewal (28, 29)”

    From Microglia depletion exacerbates demyelination and impairs remyelination in a neurotropic coronavirus infection (2020) · cites this paper as [28]

    The Results section, “Early microglial repopulation events,” reports rapid repopulation after withdrawal of PLX3397, not PLX5622. The Results section, “Surviving microglia cannot solely account for repopulation,” says surviving microglia alone cannot explain it and points to a CNS progenitor cell; thus the claimed self-renewal mechanism is not fully supported. (LLM, conf=0.90)

    Experimental — accuracy not yet measured
  • CSF-1, IL-34, and TGF-β1 have been shown to play important roles in microglial proliferation and/or survival.

    “because these cytokines have been shown to play important roles in microglial proliferation and/or survival [43, 44].”

    From IL-1β-driven amyloid plaque clearance is associated with an expansion of transcriptionally reprogrammed microglia (2019) · cites this paper as [44]

    The Discussion ('Dependence of microglia on CSF1R signaling in the adult brain'; page not supplied) reports reduced microglial densities in mice lacking CSF-1 or IL-34 and finds that adult microglia depend on CSF1R signaling for survival. Our copy does not establish a role for TGF-β1 in microglial proliferation or survival; its References list a TGF-β1 study concerning macrophages instead. (LLM, conf=0.88)

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Research works printed but not linked: 1

  1. Nandi S Gokhan S Dai XM Wei S Enikolopov G Lin H Mehler MF Stanley ER 2012b The CSF-1 receptor ligands IL-34 and CSF-1 exhibit distinct developmental brain expression patterns and regulate neural progenitor cell maintenance and maturation Dev Biol 367 100 113 22542597 PMC3388946

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Authors
Elmore, M. R. P., Najafi, A. R., Koike, M. A., Dagher, N. N., Spangenberg, E. E., Rice, R. A., Kitazawa, M., Matusow, B., Nguyen, H., West, B. L., & Green, K. N.
Affiliations
  • University of California, Irvine (US)
  • University of California, Merced (US)
  • Plexxikon (United States) (US)
Corresponding author
Green, Kim N.
Venue
Neuron
Publisher
Elsevier BV
Published
2014-04
Volume
82
Issue
2
Pages
380-397
ISSN
0896-6273 (ISSN-L)
OpenAlex
W2104431737
Cited by
1,968
References
46
Citations by year
2026: 161 · 2025: 182 · 2024: 240 · 2023: 172 · 2022: 201 · 2021: 245 · 2020: 191 · 2019: 154 · 2018: 128 · 2017: 101 · 2016: 88 · 2015: 75 · 2014: 27
FWCI
50.08
Type
journal article
Language
en
Open access
Locations
  • Neuron (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion)
  • PubMed Central (acceptedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
  • National Institutes of Health (1R01NS083801, F31NS086409, UL1 TR000153)
  • Whitehall Foundation
  • National Institute of Neurological Disorders and Stroke
  • American Federation for Aging Research
  • Alzheimer&apos;s Association (AG00538)
Topics
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Life Sciences › Neuroscience › Developmental Neuroscience › Neurogenesis and neuroplasticity mechanisms
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Multiple Sclerosis Research Studies
Keywords
colony-stimulating factor 1 receptor, CSF1R signaling, microglia, CSF1R inhibitor, microglial depletion, microglial repopulation, nestin-positive cells, microglial proliferation, microglial differentiation, adult brain, microglial homeostasis, myeloid lineage
MeSH terms
Animals, Animals, Newborn, Brain, Enzyme Inhibitors, Gene Expression Regulation, Lipopolysaccharides, Male, Mice, Inbred C57BL, Mice, Transgenic, Nerve Tissue Proteins, Time Factors, Signal Transduction, Macrophage Colony-Stimulating Factor, Receptor, Macrophage Colony-Stimulating Factor, Cell Death, Microglia, Maze Learning, Cell Proliferation, Mice, Adult Stem Cells

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