Macrophage-derived oncostatin M contributes to human and mouse neurogenic heterotopic ossifications
Frédéric Torossian, … , Jean-Jacques Lataillade, Marie-Caroline Le Bousse-Kerdilès
Frédéric Torossian, … , Jean-Jacques Lataillade, Marie-Caroline Le Bousse-Kerdilès
Published November 2, 2017
Citation Information: JCI Insight. 2017;2(21):e96034. https://doi.org/10.1172/jci.insight.96034.
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Research Article Bone biology Hematology

Macrophage-derived oncostatin M contributes to human and mouse neurogenic heterotopic ossifications

Abstract

Neurogenic heterotopic ossification (NHO) is the formation of ectopic bone generally in muscles surrounding joints following spinal cord or brain injury. We investigated the mechanisms of NHO formation in 64 patients and a mouse model of spinal cord injury–induced NHO. We show that marrow from human NHOs contains hematopoietic stem cell (HSC) niches, in which mesenchymal stromal cells (MSCs) and endothelial cells provide an environment supporting HSC maintenance, proliferation, and differentiation. The transcriptomic signature of MSCs from NHOs shows a neuronal imprinting associated with a molecular network required for HSC support. We demonstrate that oncostatin M (OSM) produced by activated macrophages promotes osteoblastic differentiation and mineralization of human muscle-derived stromal cells surrounding NHOs. The key role of OSM was confirmed using an experimental model of NHO in mice defective for the OSM receptor (OSMR). Our results provide strong evidence that macrophages contribute to NHO formation through the osteogenic action of OSM on muscle cells within an inflammatory context and suggest that OSM/OSMR could be a suitable therapeutic target. Altogether, the evidence of HSCs in ectopic bones growing at the expense of soft tissue in spinal cord/brain-injured patients indicates that inflammation and muscle contribute to HSC regulation by the brain-bone-blood triad.

Authors

Frédéric Torossian, Bernadette Guerton, Adrienne Anginot, Kylie A. Alexander, Christophe Desterke, Sabrina Soave, Hsu-Wen Tseng, Nassim Arouche, Laetitia Boutin, Irina Kulina, Marjorie Salga, Beulah Jose, Allison R. Pettit, Denis Clay, Nathalie Rochet, Erica Vlachos, Guillaume Genet, Charlotte Debaud, Philippe Denormandie, François Genet, Natalie A. Sims, Sébastien Banzet, Jean-Pierre Levesque, Jean-Jacques Lataillade, Marie-Caroline Le Bousse-Kerdilès

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Figure 6

Activated macrophages contribute to the osteogenic differentiation of human NHO-MDSCs.

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Activated macrophages contribute to the osteogenic differentiation of hu...
(A) CD34+ cells from human neurogenic heterotopic ossification (NHO) were isolated using immunomagnetic cell separation and induced to differentiate into macrophages for 2 weeks in specific medium. Cells were then analyzed by flow cytometry for expression of myeloid marker CD11b, monocyte/macrophage marker CD14, and M2 macrophage activation marker CD163 and CD206. (B) Activated macrophages derived in vitro from NHO CD34+ cells stimulate NHO muscle–derived stromal cells (NHO-MDSCs). NHO-MDSCs were cultured in control medium (CT) or osteogenic medium alone (OB) or were supplemented with LPS (100 ng/ml, OB LPS) with or without the addition of monocytes/macrophages (mac; 2.105/well/500 μl) differentiated from NHO CD34+ cells (NHOmac). After 3 weeks, cells were then stained with Alizarin Red S. Calcium mineralization was quantified and expressed as mean ± SEM (n = 6). (C) Mononuclear cells from human NHO marrows were analyzed by flow cytometry for mac markers, as in A. (D) Medium conditioned by activated macrophages from human NHO stimulate NHO-MDSC mineralization. In that purpose, CD14+ monocytes/macrophages from human NHO were isolated using immunomagnetic cell separation and cultured with or without LPS (100 ng/ml) for 3 days. Conditioned media with (NHOmac CM+) or without LPS (NHOmac CM–) were recovered and added to cultures of NHO-MDSCs. NHO-MDSCs were cultured in control medium (CT) or osteogenic medium alone (OB) or supplemented with NHOmac CM– or NHOmac CM+ (diluted at 1:10) for 3 weeks. Cells were then stained with Alizarin Red S. Calcium mineralization was quantified and expressed as mean ± SEM (n ≥ 3). For statistical analysis, 1-way ANOVA followed by Dunnett’s post-hoc test were used (*P ≤ 0.05 and ***P ≤ 0.001).