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Nature. 2019 Aug;572(7771):670-675. doi: 10.1038/s41586-019-1471-1. Epub 2019 Aug 7.

Locally renewing resident synovial macrophages provide a protective barrier for the joint.

Author information

1
Department of Internal Medicine 3 - Rheumatology and Immunology, Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
2
Nikolaus Fiebiger Center of Molecular Medicine, Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
3
Area of Cell and Developmental Biology, Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain.
4
Institute of Human Genetics, Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
5
Department of Infection Biology, Universitätsklinikum Erlangen, Friedrich Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
6
Laboratory of Systems Tumor Immunology, Department of Dermatology, Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
7
Department of Functional and Clinical Anatomy, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
8
Department of Trauma Surgery, Universitätsklinikum Erlangen, Friedrich Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
9
Leibniz Research Institute of Molecular Pharmacology, Berlin, Germany.
10
Institute of Radiology, PIPE (Preclinical Imaging Platform Erlangen), Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
11
Department of Internal Medicine 3 - Rheumatology and Immunology, Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany. gerhard.kroenke@uk-erlangen.de.
12
Nikolaus Fiebiger Center of Molecular Medicine, Universitätsklinikum Erlangen and Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany. gerhard.kroenke@uk-erlangen.de.

Abstract

Macrophages are considered to contribute to chronic inflammatory diseases such as rheumatoid arthritis1. However, both the exact origin and the role of macrophages in inflammatory joint disease remain unclear. Here we use fate-mapping approaches in conjunction with three-dimensional light-sheet fluorescence microscopy and single-cell RNA sequencing to perform a comprehensive spatiotemporal analysis of the composition, origin and differentiation of subsets of macrophages within healthy and inflamed joints, and study the roles of these macrophages during arthritis. We find that dynamic membrane-like structures, consisting of a distinct population of CX3CR1+ tissue-resident macrophages, form an internal immunological barrier at the synovial lining and physically seclude the joint. These barrier-forming macrophages display features that are otherwise typical of epithelial cells, and maintain their numbers through a pool of locally proliferating CX3CR1- mononuclear cells that are embedded into the synovial tissue. Unlike recruited monocyte-derived macrophages, which actively contribute to joint inflammation, these epithelial-like CX3CR1+ lining macrophages restrict the inflammatory reaction by providing a tight-junction-mediated shield for intra-articular structures. Our data reveal an unexpected functional diversification among synovial macrophages and have important implications for the general role of macrophages in health and disease.

PMID:
31391580
DOI:
10.1038/s41586-019-1471-1

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