Holm Erik, Gleberzon Jared S, Liao Yinyin, Sørensen Esben S, Beier Frank, Hunter Graeme K, Goldberg Harvey A
*Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada, N6A 5C1.
†Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000 Aarhus, Denmark.
Biochem J. 2014 Dec 15;464(3):355-64. doi: 10.1042/BJ20140702.
Biomineralization is a complex process in the development of mineralized tissues such as bone and pathological calcifications such as atherosclerotic plaques, kidney stones and gout. Osteopontin (OPN), an anionic phosphoprotein, is expressed in mineralizing tissues and has previously been demonstrated to be a potent inhibitor of hydroxyapatite formation. The OPN-deficient (Opn-/-) mouse displays a hypermineralized bone phenotype starting at 12 weeks postnatally. By isolating and culturing Opn-/- and wild-type (WT) osteoblasts, we sought to determine the role of OPN and two of its functional peptides in osteoblast development and mineralization. Opn-/- osteoblasts had significantly increased mineral deposition relative to their WT counterparts, with no physiologically relevant change in gene expression of osteogenic markers. Supplementation with bovine milk OPN (mOPN) led to a dramatic reduction in mineral deposition by the Opn-/- osteoblasts. Treatment with OPN-derived peptides corresponding to phosphorylated OPN-(220-235) (P3) and non-phosphorylated OPN-(65-80) (OPAR) also rescued the hypermineralization phenotype of Opn-/- osteogenic cultures. Supplementation with mOPN or the OPN-derived peptides did not alter the expression of terminal osteogenic markers. These data suggest that OPN plays an important role in the regulation of biomineralization, but that OPN does not appear to affect osteoblast cell development in vitro.
生物矿化是矿化组织（如骨骼）发育以及病理性钙化（如动脉粥样硬化斑块、肾结石和痛风）过程中的一个复杂过程。骨桥蛋白（OPN）是一种阴离子磷蛋白，在矿化组织中表达，此前已被证明是羟基磷灰石形成的有效抑制剂。OPN基因缺陷（Opn-/-）小鼠在出生后12周开始表现出骨矿化过度的表型。通过分离和培养Opn-/-和野生型（WT）成骨细胞，我们试图确定OPN及其两个功能肽在成骨细胞发育和矿化中的作用。与野生型成骨细胞相比，Opn-/-成骨细胞的矿物质沉积显著增加，而成骨标志物的基因表达没有发生生理相关变化。补充牛乳OPN（mOPN）可导致Opn-/-成骨细胞的矿物质沉积显著减少。用与磷酸化OPN-（220-235）（P3）和非磷酸化OPN-（65-80）（OPAR）对应的OPN衍生肽处理也挽救了Opn-/-成骨培养物的矿化过度表型。补充mOPN或OPN衍生肽不会改变终末成骨标志物的表达。这些数据表明，OPN在生物矿化调节中起重要作用，但OPN似乎不影响体外成骨细胞的发育。
