Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors
Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors
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DOI：
10.3324/haematol.2016.144808
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发表时间：
2016-12-01
期刊：
影响因子：
10.1
通讯作者：
Hofbauer, Lorenz C.
中科院分区：
文献类型：
--
作者：
Baschant, Ulrike;Rauner, Mar Tina;Hofbauer, Lorenz C.
血色素沉着症或慢性输血引起的铁超载与骨质疏松症的发生有关。然而，铁稳态变化对成骨细胞功能的影响及其潜在机制尚不明确。由于Wnt信号是骨重塑的关键调节因子，我们旨在分析铁超载和铁缺乏对成骨细胞功能的影响，并进一步明确Wnt信号在这些过程中的作用。因此，从野生型小鼠中分离骨髓基质细胞并向成骨细胞分化。在矿化和成骨基因表达方面，细胞暴露于铁剂量依赖性减弱了成骨细胞的分化，而铁与去铁胺的螯合作用以时间和剂量依赖性的方式促进成骨分化，可达3倍。在人骨髓基质细胞中也得到了类似的结果。为了阐明去铁胺的促成骨作用是否通过Wnt信号介导，我们对去铁胺处理的成骨细胞进行了Wnt谱仪阵列。Wnt5a是诱导程度最高的基因之一。进一步分析显示，在50 μ M去铁胺作用48小时后，Wnt5a的诱导上调2倍，具有时间和剂量依赖性。利用特异性抑制剂进行通路分析发现，去铁胺利用活化T细胞通路的磷脂酰肌醇-3激酶和核因子诱导Wnt5a表达。最后，我们通过分析Wnt5a缺陷细胞的基质矿化，证实了Wnt5a在去铁胺介导的成骨促进作用中的必要性。去铁胺对野生型细胞基质矿化的促进作用在Wnt5a（-/-）细胞中被完全消除。因此，这些数据表明Wnt5a对于铁螯合使用去铁胺的促成骨作用至关重要。
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 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 deferoxamine is mediated via Wnt signaling, we performed a Wnt profiler array of deferoxamine-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time-and dose-dependent induction of Wnt5a being up-regulated 2-fold after 48 h at 50 mu M deferoxamine. Pathway analysis using specific inhibitors revealed that deferoxamine utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cell pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the deferoxamine-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The promoting effect of deferoxamine 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 deferoxamine.