Activin A secretion by muscle-repairing macrophages induces heterotopic ossification in mice
Wenqiang Yin, Kazuo Okamoto, Asuka Terashima, Warunee Pluemsakunthai, Takehito Ono, Taku Ito-Kureha, Shizuo Akira, Yoshinobu Hashizume, Roland Baron, Satoshi Ueha, Kouji Matsushima, Martin M. Matzuk, Yuji Mishina, Hiroshi Takayanagi
Wenqiang Yin, Kazuo Okamoto, Asuka Terashima, Warunee Pluemsakunthai, Takehito Ono, Taku Ito-Kureha, Shizuo Akira, Yoshinobu Hashizume, Roland Baron, Satoshi Ueha, Kouji Matsushima, Martin M. Matzuk, Yuji Mishina, Hiroshi Takayanagi
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Research Article Bone biology Immunology Muscle biology

Activin A secretion by muscle-repairing macrophages induces heterotopic ossification in mice

Abstract

The immune system is not only essential for host defense, but it is also involved in tissue maintenance and disease pathogenesis. Macrophages play a key role in tissue repair, fibrosis, and tumorigenesis, but the mechanisms underlying their multifunctionality have not been fully explored. Here, we identified Mrep (Ly6ChiCX3CR1loPDPN+CD9+) as a crucial subset of macrophages for muscle regeneration after muscle injury. Muscle regeneration required Mrep-derived activin A, which was produced via the TLR4/TIR domain–containing adapter-inducing interferon-β/TANK-binding kinase 1/interferon regulatory factor 3/7 signaling pathway in response to muscle injury. Mrep exerted pathological effects by secreting activin A in a model of genetically induced heterotopic ossification (HO), which was suppressed by TLR4 inhibition. Thus, this study elucidates the context-dependent functions of macrophages and the link between injury and HO, suggesting that Mrep is a potential therapeutic target for regenerating muscles and suppressing HO.

Authors

Wenqiang Yin, Kazuo Okamoto, Asuka Terashima, Warunee Pluemsakunthai, Takehito Ono, Taku Ito-Kureha, Shizuo Akira, Yoshinobu Hashizume, Roland Baron, Satoshi Ueha, Kouji Matsushima, Martin M. Matzuk, Yuji Mishina, Hiroshi Takayanagi

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Figure 1

Macrophage depletion reduces muscle injury–induced activin A expression.

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Macrophage depletion reduces muscle injury–induced activin A expression....
(A–C) Representative flow cytometry plots (A) and statistical analysis (B and C) showing the frequency and number of neutrophils (CD11b+Ly6G+) and MDMs (CD11b+Ly6G–) in muscle tissue at 1 dpi of the mice treated with either 150 μL vehicle (n = 4) or clodronate (n = 4). (D) Experimental timeline of sample preparation for bulk RNA-seq. WT mice were injected intraperitoneally with 150 μL of vehicle or clodronate 2 days prior to muscle injury. Muscle injury was induced on day 0. Injured muscle samples were harvested at 1 dpi (vehicle, n = 2; clodronate, n = 3) and 4 dpi (vehicle, n = 2; clodronate, n = 2). (E and F) DEGs in muscle of clodronate-injected mice at 1 dpi (E) and 4 dpi (F) compared with vehicle-injected mice. Cutoff lines are drawn at log2fold change (FC) = ±1 and P = 0.05. Red dots represent genes with an absolute log2FC ≥ 1 and P < 0.05. Blue dots represent genes with an absolute log2FC < 1 and P < 0.05. Green dots represent genes with an absolute log2FC ≥ 1 and P > 0.05. (G and H) Top 10 DEGs encoding soluble factors (GO term: cytokine activity), ranked by FC, in muscles of clodronate-injected mice compared with vehicle-injected mice at 1 dpi (G) and 4 dpi (H). The P values were calculated using unpaired 2-tailed t test (B and C). A P value < 0.05 was considered significant. Data are shown as the mean ± SEM, and symbols represent individual mice (B and C).