Abstract

As the tissue macrophages of the CNS, microglia are critically involved in diseases of the CNS. However, it remains unknown what controls their maturation and activation under homeostatic conditions. We observed substantial contributions of the host microbiota to microglia homeostasis, as germ-free (GF) mice displayed global defects in microglia with altered cell proportions and an immature phenotype, leading to impaired innate immune responses. Temporal eradication of host microbiota severely changed microglia properties. Limited microbiota complexity also resulted in defective microglia. In contrast, recolonization with a complex microbiota partially restored microglia features. We determined that short-chain fatty acids (SCFA), microbiota-derived bacterial fermentation products, regulated microglia homeostasis. Accordingly, mice deficient for the SCFA receptor FFAR2 mirrored microglia defects found under GF conditions. These findings suggest that host bacteria vitally regulate microglia maturation and function, whereas microglia impairment can be rectified to some extent by complex microbiota.

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Acknowledgements

This work is dedicated to our former friend Uwe-Karsten Hanisch, past Professor for Neuroscience at the Paul-Flechsig-Institute for Brain Research, Leipzig, who devoted his whole life to the exploration of microglia function. We thank M. Oberle, M. Ditter and T. el Gaz for excellent technical assistance. We are grateful to J. Bodinek-Wersing and G. Rappl for cell sorting and to A. Spies for providing cDNA from cell cultures. M.P. was supported by the BMBF-funded competence network of multiple sclerosis (KKNMS), the Sobek Foundation, the DFG (SFB 992, FOR1336, PR 577/8-1), the Fritz-Thyssen Foundation and the Gemeinnützige Hertie Foundation (GHST). B.S. was supported by the SPP1656 “Intestinal Microbiota” (STE 1971/4-1).

Author information

Author notes

    • Daniel Erny
    •  & Anna Lena Hrabě de Angelis

    These authors contributed equally to this work.

Affiliations

  1. Institute of Neuropathology, University of Freiburg, Freiburg, Germany.

    • Daniel Erny
    • , Anna Lena Hrabě de Angelis
    • , Peter Wieghofer
    • , Ori Staszewski
    •  & Marco Prinz
  2. Lab for ImmunoGenomics, Weizmann Institute of Science, Rehovot, Israel.

    • Diego Jaitin
    • , Eyal David
    • , Hadas Keren-Shaul
    •  & Ido Amit
  3. Faculty of Biology, University of Freiburg, Freiburg, Germany.

    • Peter Wieghofer
  4. Department of Virology, University of Freiburg, Freiburg, Germany.

    • Tanel Mahlakoiv
    •  & Peter Staeheli
  5. Institute for Medical Microbiology, Immunology and Hygiene & Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany.

    • Kristin Jakobshagen
    •  & Olaf Utermöhlen
  6. Institute for Medical Microbiology, Immunology, and Hygiene, Technische Universität München, Munich, Germany.

    • Thorsten Buch
  7. Institute of Medical Microbiology and Hygiene, University of Mainz Medical Centre, Mainz, Germany.

    • Vera Schwierzeck
    •  & Andreas Diefenbach
  8. Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA.

    • Eunyoung Chun
    •  & Wendy S Garrett
  9. Mucosal Immunology Lab, Department of Clinical Research, University of Bern, Bern, Switzerland.

    • Kathy D McCoy
  10. Max-von-Pettenkofer Institute, LMU Munich, German Center for Infection Research (DZIF), partner site LMU Munich, Munich, Germany.

    • Bärbel Stecher
  11. BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany.

    • Marco Prinz

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Contributions

D.E., A.L.H.d.A., P.W., D.J., K.J., T.M., B.S., O.U., I.A., H.K.-S., E.D. and K.D.M. conducted the experiments. I.A. and O.S. analyzed the RNA sequencing and microarray data, respectively. T.B., B.S., A.D., P.S., V.S., E.C. and W.S.G. provided mice and designed experiments. M.P. supervised the project and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Marco Prinz.

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  1. 1.

    Supplementary Table 1: Altered microglial gene profile and immaturity in germ-free animals.

    Significantly down- (upper table) and up- (lower table) regulated genes subjected to functional GO cluster analysis. The significance of genes is indicated by the given P values.

  2. 2.

    Supplementary Table 2: Reduced gene induction in microglia from non-colonized GF animals.

    Affymetrix Genome 430A 2.0 array-based gene induction of microglia from SPF mice compared to GF individuals. 78 genes significantly differentially expressed in GF vs. SPF microglia 6 hr after i.c. LPS treatment are shown. Only genes also significantly up- or downregulated by LPS treatment compared to PBS treated controls of the same housing conditions (GF and SPF respectively) are included to account for differences in basal gene regulation. (P < 0.01).

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https://doi.org/10.1038/nn.4030

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