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Am J Pathol. 2015 Mar;185(3):765-75. doi: 10.1016/j.ajpath.2014.11.008. Epub 2015 Jan 2.

Oncostatin m, an inflammatory cytokine produced by macrophages, supports intramembranous bone healing in a mouse model of tibia injury.

Author information

1
INSERM, UMR 957, Ligue Team 2012, Nantes, France; Pathophysiology of Bone Resorption Laboratory and Therapy of Primary Bone Tumors, Medicine Faculty, Université de Nantes, Nantes Atlantique Universités, Nantes, France.
2
INSERM, UMR 957, Ligue Team 2012, Nantes, France; Pathophysiology of Bone Resorption Laboratory and Therapy of Primary Bone Tumors, Medicine Faculty, Université de Nantes, Nantes Atlantique Universités, Nantes, France. Electronic address: frederic.blanchard@univ-nantes.fr.

Abstract

Different macrophage depletion strategies have demonstrated a vital role of macrophages in bone healing, but the underlying molecular mechanisms are poorly understood. Here, with the use of a mouse model of tibia injury, we found that the cytokine oncostatin M [OSM or murine (m)OSM] was overexpressed during the initial inflammatory phase and that depletion of macrophages repressed mOSM expression. In Osm(-/-) mice, by micro-computed tomography and histology we observed a significant reduction in the amount of new intramedullar woven bone formed at the injured site, reduced number of Osterix(+) osteoblastic cells, and reduced expression of the osteoblast markers runt-related transcription factor 2 and alkaline phosphatase. In contrast, osteoclasts were normal throughout the healing period. One day after bone injury, Stat3, the main transcription factor activated by mOSM, was found phosphorylated/activated in endosteal osteoblastic cells located at the hedge of the hematoma. Interestingly, we observed reduced activation of Stat3 in Osm(-/-) mice. In addition, mice deficient in the mOSM receptor (Osmr(-/-)) also had reduced bone formation and osteoblast number within the injury site. These results suggest that mOSM, a product of macrophages, sustains intramembranous bone formation by signaling through Osmr and Stat3, acting on the recruitment, proliferation, and/or osteoblast differentiation of endosteal mesenchymal progenitor cells. Because bone resorption is largely unaltered, OSM could represent a new anabolic treatment for unconsolidated bone fractures.

PMID:
25559270
DOI:
10.1016/j.ajpath.2014.11.008
[Indexed for MEDLINE]

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