Patients with high bone mass phenotype exhibit enhanced osteoblast differentiation and inhibition of adipogenesis of human mesenchymal stem cells
Patients with high bone mass phenotype exhibit enhanced osteoblast differentiation and inhibition of adipogenesis of human mesenchymal stem cells
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DOI：
10.1359/jbmr.070721
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发表时间：
2007-11-01
影响因子：
6.2
通讯作者：
Kassem, Moustapha
中科院分区：
文献类型：
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作者：
Qiu, Weimin;Andersen, Tom E.;Kassem, Moustapha
LRP5基因的基因突变影响Wnt信号传导并导致人类骨量的变化。我们的体内和体外实验结果表明，激活的LRP5突变T253I促进了骨生成，抑制了脂肪生成。LRP5的失活突变T244M具有相反的作用。Writ共受体LRP5突变导致典型Writ信号减少或增加，分别导致骨质疏松症或高骨量（HBM）表型。然而，LRP5突变导致骨量变化的机制尚不清楚。材料和方法：我们研究了HBM表型患者和对照组的髂骨骨活检中的骨髓成分。我们还利用逆转录病毒介导的基因转导建立了三种不同的人间充质干细胞（hMSC）株，稳定表达野生型LRP5（hMSC-LRP5(WT)）、LRP5(t44) （hMSC-LRP5(t44)，失活突变导致骨质疏松）或LRP5(T253) （hMSC-LRP5（T253）激活突变导致高骨量）。我们使用双荧光素酶测定、细胞增殖、实时PCR的谱系生物标志物和体内骨形成来表征Writ信号激活。结果：在骨活检中，我们发现HBM表型患者（n - 9）与对照组（n = 5）相比，骨小梁骨体积增加，骨髓脂肪体积减少。hMSC-LRP5（WT）和hMSC-LRP5（T253）能高水平转导Writ信号，而hMSC-LRP5（T244）则不能。Wnt3a抑制hMSC-LRP5（WT）和hMSC-LRP5（T253）的细胞增殖，这种作用与DKK1的下调有关。在体外实验中，hMSC-LRP5（WT）和hMSC-LRP5（T253）均表现出增强成骨细胞分化和抑制脂肪生成的作用，而hMSC-LRP5（t144）则表现出相反的作用。同样，在SCID/NOD小鼠皮下植入羟基磷灰石/磷酸三钙后，hMSC-LRP5（WT）和hMSC-LRP5（T253）而非hMSC-LRP5（t144）形成异位矿化骨。结论：LRP5突变和Writ信号水平决定了hMSCs向成骨细胞或脂肪细胞分化的命运。因此，激活Writ信号可以提供一种新的方法，通过防止与年龄相关的骨生成和脂肪生成的相互减少来增加骨量。
Genetic mutations in the LRP5 gene affect Wnt signaling and lead to changes in bone mass in humans. Our in vivo and in vitro results show that activated mutation T253I of LRP5 enhances osteogenesis and inhibits adipogenesis. Inactivating mutation T244M of LRP5 exerts opposite effects.Introduction: Mutations in the Writ co-receptor, LRP5, leading to decreased or increased canonical Writ signaling, result in osteoporosis or a high bone mass (HBM) phenotype, respectively. However, the mechanisms whereby mutated LRP5 causes changes in bone mass are not known.Materials and Methods: We studied bone marrow composition in iliac crest bone biopsies from patients with the HBM phenotype and controls. We also used retrovirus-mediated gene transduction to establish three different human mesenchymal stem cell (hMSC) strains stably expressing wildtype LRP5 (hMSC-LRP5(WT)), LRP5(T244) (hMSC-LRP5(T244), inactivation mutation leading to osteoporosis), or LRP5(T253) (hMSC-LRP5(T253) activation mutation leading to high bone mass). We characterized Writ signaling activation using a dual luciferase assay, cell proliferation, lineage biomarkers using real-time PCR, and in vivo bone formation.Results: In bone biopsies, we found increased trabecular bone volume and decreased bone marrow fat volume in patients with the HBM phenotype (n - 9) compared with controls (n = 5). The hMSC-LRP5(WT) and hMSC-LRP5(T253) but not hMSC-LRP5(T244) transduced high level of Writ signaling. Wnt3a inhibited cell proliferation in hMSC-LRP5(WT) and hMSC-LRP5(T253), and this effect was associated with downregulation of DKK1. Both hMSC-LRP5(WT) and hMSC-LRP5(T253) showed enhanced osteoblast differentiation and inhibited adipogenesis in vitro, and the opposite effect was observed in hMSC-LRP5(T244). Similarly, hMSC-LRP5(WT) and hMSC-LRP5(T253) but not hMSC-LRP5(T244) formed ectopic mineralized bone when implanted subcutaneously with hydroxyapatite/tricalcium phosphate in SCID/NOD mice.Conclusions: LRP5 mutations and the level of Writ signaling determine differentiation fate of hMSCs into osteoblasts or adipocytes. Activation of Writ signaling can thus provide a novel approach to increase bone mass by preventing the age-related reciprocal decrease in osteogenesis and increase in adipogenesis.