Iron overload due to hemochromatosis or chronic blood transfusions has been associated with the development of osteoporosis. However, the impact of changes in iron homeostasis on osteoblast functions and the underlying mechanisms are poorly defined. Since Wnt signaling is a critical regulator of bone remodeling, we aimed to analyze the effects of iron overload and iron deficiency on osteoblast function and further define the role of Wnt signaling in these processes. Therefore, bone marrow stromal cells were isolated from wild-type mice and differentiated towards osteoblasts. Exposure of the cells to iron dose-dependently attenuated osteoblast differentiation in terms of mineralization and osteogenic gene expression, whereas iron chelation with deferoxamine (DFO) promoted osteogenic differentiation in a time- and dose-dependent manner up to 3-fold. Similar results were obtained for human bone marrow stromal cells. To elucidate whether the pro-osteogenic effect of DFO is mediated via Wnt signaling, we performed a Wnt profiler array of DFO-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time- and dose-dependent induction of Wnt5a being up-regulated two-fold after 48 h at 50 mM DFO. Pathway analysis using specific inhibitors revealed that DFO utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cells pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the DFO-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The DFO-promoting effect on matrix mineralization in wild-type cells was completely abolished in Wnt5a-/- cells. Thus, these data demonstrate that Wnt5a is critical for the pro-osteogenic effects of iron chelation using DFO.

Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors

ROETTO, Antonella;
2016

Abstract

Iron overload due to hemochromatosis or chronic blood transfusions has been associated with the development of osteoporosis. However, the impact of changes in iron homeostasis on osteoblast functions and the underlying mechanisms are poorly defined. Since Wnt signaling is a critical regulator of bone remodeling, we aimed to analyze the effects of iron overload and iron deficiency on osteoblast function and further define the role of Wnt signaling in these processes. Therefore, bone marrow stromal cells were isolated from wild-type mice and differentiated towards osteoblasts. Exposure of the cells to iron dose-dependently attenuated osteoblast differentiation in terms of mineralization and osteogenic gene expression, whereas iron chelation with deferoxamine (DFO) promoted osteogenic differentiation in a time- and dose-dependent manner up to 3-fold. Similar results were obtained for human bone marrow stromal cells. To elucidate whether the pro-osteogenic effect of DFO is mediated via Wnt signaling, we performed a Wnt profiler array of DFO-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time- and dose-dependent induction of Wnt5a being up-regulated two-fold after 48 h at 50 mM DFO. Pathway analysis using specific inhibitors revealed that DFO utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cells pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the DFO-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The DFO-promoting effect on matrix mineralization in wild-type cells was completely abolished in Wnt5a-/- cells. Thus, these data demonstrate that Wnt5a is critical for the pro-osteogenic effects of iron chelation using DFO.
1499
1507
Bone Marrow Microenvironment; Iron Metabolism; Mesenchymal Stem Cells
Baschant, Ulrike; Rauner, Martina; Bulycheva, Ekaterina; Weidner, Heike; Roetto, Antonella; Platzbecker, Uwe; Hofbauer, Lorenz C
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/1625319
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