Koshihara Y, Hoshi K
Department of Biosignal Research, Tokyo Metropolitan Institute of Gerontology, Japan.
J Bone Miner Res. 1997 Mar;12(3):431-8. doi: 10.1359/jbmr.1997.12.3.431.
The role of vitamin K in osteocalcin accumulation in the extracellular matrix of normal human osteoblasts in culture was investigated by using a human intact osteocalcin-specific assay system. Human osteoblasts produced osteocalcin by treatment with 10(-9) M 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) for 20 days in culture. With the addition of vitamin K2 (1.5-5.0 microM), osteocalcin accumulation in the extracellular matrix of the osteoblasts was increased, but the osteocalcin content in the conditioned medium decreased, in comparison with that treated with 10-9 M 1,25(OH)2D3 alone. The enhancement of osteocalcin accumulation induced by vitamin K2 was dependent on the duration of the treatment. The vitamin K2 plus 1,25(OH)2D3-induced osteocalcin accumulation was blocked by the addition of warfarin 2 days before the vitamin treatment. At that time, warfarin significantly reduced the mineralization by osteoblasts in vitro. Osteocalcin accumulated in the extracellular matrix was almost completely precipitated by a low concentration of hydroxyapatite, 10 mg/ml. Moreover, the gamma-carboxyglutamic acid (Gla)-containing osteocalcin level was increased by the vitamin K2 plus 1,25(OH)2D3 treatment. These results proved that vitamin K2 increased Gla-containing osteocalcin, which accumulated osteocalcin in the extracellular matrix, and facilitated mineralization in vitro. Vitamin K2 also enhanced the 1,25(OH)2D3-induced osteocalcin mRNA level, but vitamin K2 alone did not show osteocalcin mRNA expression. We thus demonstrated that vitamin K2 enhanced not only the accumulation of Gla osteocalcin, but also the osteocalcin production induced by 1,25(OH)2D3 in human osteoblasts in culture.
通过使用人完整骨钙素特异性检测系统，研究了维生素K在培养的正常人成骨细胞细胞外基质中骨钙素积累中的作用。在培养中用10(-9)M 1,25-二羟基维生素D3（1,25(OH)2D3）处理20天，人成骨细胞产生骨钙素。与单独用10-9M 1,25(OH)2D3处理相比，添加维生素K2（1.5 - 5.0 microM）后，成骨细胞细胞外基质中骨钙素的积累增加，但条件培养基中的骨钙素含量降低。维生素K2诱导的骨钙素积累增强取决于处理持续时间。在维生素处理前2天添加华法林可阻断维生素K2加1,25(OH)2D3诱导的骨钙素积累。此时，华法林显著降低了成骨细胞在体外的矿化作用。细胞外基质中积累的骨钙素几乎完全被低浓度的羟基磷灰石（10 mg/ml）沉淀。此外，维生素K2加1,25(OH)2D3处理可提高含γ-羧基谷氨酸（Gla）的骨钙素水平。这些结果证明，维生素K2增加了含Gla的骨钙素，使其在细胞外基质中积累骨钙素，并促进了体外矿化。维生素K2还增强了1,25(OH)2D3诱导的骨钙素mRNA水平，但单独的维生素K2未显示骨钙素mRNA表达。因此，我们证明维生素K2不仅增强了Gla骨钙素的积累，还增强了培养的人成骨细胞中1,25(OH)2D3诱导的骨钙素产生。
