Induction of Osteogenesis in Mesenchymal Stem Cells by Activated Monocytes/Macrophages Depends on Oncostatin M Signaling

Abstract

Bone resorption by osteoclasts and bone formation by osteoblasts are tightly coupled processes implicating factors in TNF, bone morphogenetic protein, and Wnt families. In osteoimmunology, macrophages were described as another critical cell population regulating bone formation by osteoblasts but the coupling factors were not identified. Using a high-throughput approach, we identified here Oncostatin M (OSM), a cytokine of the IL-6 family, as a major coupling factor produced by activated circulating CD14 1 or bone marrow CD11b 1 monocytes/macrophages that induce osteoblast differentiation and matrix mineralization from human mesenchymal stem cells while inhibiting adipogenesis. Upon activation of toll-like receptors (TLRs) by lipopolysaccharide or endogenous ligands, OSM was produced in classically activated inflammatory M1 and not M2 macrophages, through a cyclooxygenase-2 and prostaglandin-E2 regulatory loop. Stimulation of osteogenesis by activated monocytes/macrophages was prevented using neutralizing antibodies or siRNA to OSM, OSM receptor subunits gp130 and OSMR, or to the downstream transcription factor STAT3. The induced osteoblast differentiation program culminated with enhanced expression of CCAAT-enhancer-binding protein d, Cbfa1, and alkaline phosphatase. Overexpression of OSM in the tibia of mice has led to new bone apposition with no sign of bone resorption. Two other cytokines have also a potent role in bone formation induced by monocytes/macrophages and activation of TLRs: IL-6 and leukemia inhibitory factor. We propose that during bone inflammation, infection, or injury, the IL-6 family signaling network activated by macrophages and TLR ligands stimulates bone formation that is largely uncoupled from bone resorption and is thus an important target for anabolic bone therapies. STEM CELLS 2012;30:762-772 Disclosure of potential conflicts of interest is found at the end of this article.

The contribution of immune infiltrates and the local microenvironment in the pathogenesis of osteosarcoma

“…The role of macrophages in bone biology has been extensively exemplified [58]. These cells are involved in bone resorption acting as osteoclast precursors in presence of M-CSF and RANKL [59] and contributing also to bone formation [60]. Indeed, macrophages control osteogenesis from mesenchymal stem cells, mechanism dependent on Oncostatin M signaling.…”

The roles of immune cells in bone healing; what we know, do not know and future perspectives

“…Toll-like receptors (TLRs) stimulate MSC migration and osteogenic differentiation utilising NFk-b and PI3 kinase signalling pathways [48]. Additionally, macrophages existing in the fractured bone are a source of bone morphogenetic proteins (BMPs) and Oncostatin M that enhance the proliferation and osteogenic function of MSCs [49,50]. Furthermore, activated monocytes induce the expression level of Cbfa1/Runx2 and alkaline phosphatase (ALP) by MSCs and hence drive the bone formation [51].I n contrast, a conditioned media from CD4 T-lymphocytes and not CD8 has been shown to increase the osteogenesis markers of MSCs [52].…”

New chondrosarcoma cell lines and mouse models to study the link between chondrogenesis and chemoresistance

“…30 For human MSCs, 10 ml of bone marrow was harvested by iliac crest aspiration from a 39-year-old male donor (after informed consent and ethical approval). MSCs were obtained as previously described 31 and cultured in a medium composed of MEM-a (Gibco Life-Technologies), 1% P/S, 10% FBS, 1 ng/ml basic fibroblast growth factor (bFGF; R&D systems, Minneapolis, MN, USA) and 2 mM L-glutamine. Adherent cells were frozen at passage 2 after characterization by flow cytometry (CD45 À , CD34 À , CD105 þ , CD73 þ and CD90 þ , purityX99%) before further experiments.…”

“…The cells were fixed with 70% ethanol for 1 h at 4 1C and stained for 10 min with alizarin red S (40 mM, pH 7.4; Sigma-Aldrich). 31 For adipogenic differentiation, 2 Â 10 4 cells were plated per well of a Millicell EZ SLIDE four-well glass (Millipore, Merck, Darmstadt, Germany) and grown in DMEM supplemented with 10% FBS, 1% P/S, 1 mM dexamethasone, 500 mM 3-isobutyl-1-methylxanthine and 60 mM indomethacine (Sigma-Aldrich). The medium was changed three times for 1 week.…”

“…The cells were fixed with 4% paraformaldehyde for 15 min at RT and intracytoplasmic lipid droplets and nuclei were stained in the dark with 0.1 mg/ml Nile Red (SigmaAldrich) for 15 min and DAPI (Invitrogen Life-Technologies) for 5 min at RT. 31 For chondrocytic differentiation, 2.5 Â 10 5 cells were placed in a 15-ml polypropylene tube (Corning, Capitol Scientific, Austin, TX, USA) and centrifuged. The pellet was cultured in 500 ml standard medium or ready-to-use complete chondrogenic differentiation medium (following the manufacturer's recommendations, Lonza) containing FBS, dexamethasone, ITS (insulin transferrin selenium) and 10 ng/ ml freshly added transforming growth factor b3 (TGF-b3, Peprotech, Rocky Hill, NJ, USA).…”