Functional heterogeneity of osteocytes in FGF23 production: the possible involvement of DMP1 as a direct negative regulator.
Functional heterogeneity of osteocytes in FGF23 production: the possible involvement of DMP1 as a direct negative regulator.
复制标题
DOI：
10.1038/bonekey.2014.38
复制
发表时间：
2014-01-01
期刊：
影响因子：
--
通讯作者：
Iimura, Tadahiro
中科院分区：
文献类型：
--
作者：
Lee, Ji-Won;Yamaguchi, Akira;Iimura, Tadahiro
成纤维细胞生长因子23（FGF 23）和牙本质基质蛋白（DMP 1）是骨中骨细胞的标志。然而，DMP 1作为调节FGF 23和骨矿化的局部因子的作用机制尚不清楚。我们首先观察到空间上不同的分布FGF 23和DMP 1阳性骨细胞陷窝在大鼠股骨免疫组化。三维免疫荧光形态计量学进一步证明，这两种蛋白的分布和相对表达水平表现出相反的模式，特别是在中段皮质骨。这些体内研究结果表明，DMP 1在骨细胞中的FGF 23表达中具有直接作用。我们接下来观察到，在UMR-106成骨细胞/骨细胞样细胞和长期培养的MC 3 T3-E1成骨细胞中接种重组DMP 1显示出FGF 23产生的显著下调。通过与粘着斑激酶（FAK）抑制剂或MEK（促分裂原活化蛋白激酶（MAPK）/细胞外信号调节激酶（ERK））抑制剂孵育而不是与磷酸肌醇3-激酶或Rho激酶抑制剂孵育来挽救这种作用。结果表明，外源性DMP 1能激活FAK介导的MAPK信号通路，使FAK、ERK和p38磷酸化水平显著升高。这些发现表明，DMP 1是参与FAK介导的MAPK通路的骨细胞中FGF 23产生的局部、直接和负调节剂，提出了协调骨细胞腔隙和骨代谢的细胞外环境的相关通路。
Fibroblast growth factor 23 (FGF23) and dentin matrix protein (DMP1) are hallmarks of osteocytes in bone. However, the mechanisms underlying the actions of DMP1 as a local factor regulating FGF23 and bone mineralization are not well understood. We first observed spatially distinct distributions of FGF23- and DMP1-positive osteocytic lacunae in rat femurs using immunohistochemistry. Three-dimensional immunofluorescence morphometry further demonstrated that the distribution and relative expression levels of these two proteins exhibited reciprocally reversed patterns especially in midshaft cortical bone. These in vivo findings suggest a direct role of DMP1 in FGF23 expression in osteocytes. We next observed that the inoculation of recombinant DMP1 in UMR-106 osteoblast/osteocyte-like cells and long-cultured MC3T3-E1 osteoblastic cells showed significant downregulation of FGF23 production. This effect was rescued by incubation with an focal adhesion kinase (FAK) inhibitor or MEK (mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK)) inhibitor but not inhibitors of phosphoinositide 3-kinase or Rho kinase. Consistently, the levels of phosphorylated FAK, ERK and p38 were significantly elevated, indicating that exogenous DMP1 is capable of activating FAK-mediated MAPK signaling. These findings suggest that DMP1 is a local, direct and negative regulator of FGF23 production in osteocytes involved in the FAK-mediated MAPK pathway, proposing a relevant pathway that coordinates the extracellular environment of osteocytic lacunae and bone metabolism.