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FEBS J. 2017 Feb;284(4):517-524. doi: 10.1111/febs.13827. Epub 2016 Aug 18.

Regulatory T cells and skeletal muscle regeneration.

Author information

1
Venetian Institute of Molecular Medicine (VIMM), Padova, Italy.
2
Department of Biomedical Sciences, University of Padova, Italy.
3
Department of Medicine (DIMED), University of Padova, Italy.
4
Division of Immunology, Transplantation and Infectious Disease, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milano, Italy.

Abstract

Skeletal muscle regeneration results from the activation and differentiation of myogenic stem cells, called satellite cells, located beneath the basal lamina of the muscle fibers. Inflammatory and immune cells have a crucial role in the regeneration process. Acute muscle injury causes an immediate transient wave of neutrophils followed by a more persistent infiltration of M1 (proinflammatory) and M2 (anti-inflammatory/proregenerative) macrophages. New studies show that injured muscle is also infiltrated by a specialized population of regulatory T (Treg) cells, which control both the inflammatory response, by promoting the M1-to-M2 switch, and the activation of satellite cells. Treg cells accumulate in injured muscle in response to specific cytokines, such as IL-33, and promote muscle growth by releasing growth factors, such as amphiregulin. Muscle repair during aging is impaired due to reduced number of Treg cells and can be enhanced by IL-33 supplementation. Migration of Treg cells could also contribute to explain the effect of heterochronic parabiosis, whereby muscle regeneration of aged mice can be improved by a parabiotically linked young partners. In mdx dystrophin-deficient mice, a model of human Duchenne muscular dystrophy, muscle injury, and inflammation is mitigated by expansion of the Treg-cell population but exacerbated by Treg-cell depletion. These findings support the notion that immunological mechanisms are not only essential in the response to pathogenic microbes and tumor cells but also have a wider homeostatic role in tissue repair, and open new perspectives for boosting muscle growth in chronic muscle disease and during aging.

KEYWORDS:

Treg cells; aging; macrophages; muscle regeneration; myopathies; parabiosis

PMID:
27479876
DOI:
10.1111/febs.13827
[Indexed for MEDLINE]
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