Department of Biochemistry, Tokyo Dental College, Tokyo, 101-0061, Japan; Tokyo Dental College Research Branding Project, Tokyo Dental College, Tokyo, 101-0061, Japan.
Tokyo Dental College Research Branding Project, Tokyo Dental College, Tokyo, 101-0061, Japan; Department of Pharmacology, Tokyo Dental College, Tokyo, 101-0061, Japan.
Biochem Biophys Res Commun. 2020 Apr 9;524(3):702-709. doi: 10.1016/j.bbrc.2020.01.136. Epub 2020 Feb 5.
Tissue-nonspecific alkaline phosphatase (TNAP) is expressed in the calcification sites of the skeletal tissue. It promotes hydroxyapatite crystal formation by degrading inorganic pyrophosphate (PP) and increasing inorganic phosphate (P) concentration. However, abnormalities in Alpl mouse-derived osteoblasts are poorly understood, and the involvement of TNAP in osteoblast differentiation remains unclear. Therefore, in this study, we aimed to investigate the precise role of TNAP in osteoblast differentiation. TNAP inhibition by levamisole, a reversible TNAP inhibitor, suppressed the expression of osteoblast differentiation marker genes in wild-type osteoblastic cells. Alpl overexpression increased the expression of master osteoblast transcription factor genes runt-related transcription factor 2 (Runx2) and Sp7 and the mature osteoblast and osteocyte marker genes, bone γ-carboxyglutamate protein 2 (Bglap2) and dentin matrix protein 1 (Dmp1), respectively in Alpl-deficient osteoblastic cells. TNAP regulated Runx2 expression, which in turn regulated the expression of all other osteoblast markers, except Dmp1. Dmp1 expression was independent of RUNX2 but was dependent on extracellular P concentration in Runx2-deficient osteogenic cells. These results suggest that TNAP functions as an osteogenic differentiation regulator either by regulating Runx2 expression or by controlling extracellular P concentration.
组织非特异性碱性磷酸酶（TNAP）在骨骼组织的钙化部位表达。它通过降解无机焦磷酸盐（PP）和增加无机磷酸盐（P）浓度来促进羟基磷灰石晶体的形成。然而，Alpl 小鼠来源的成骨细胞的异常情况知之甚少，TNAP 在成骨细胞分化中的作用仍不清楚。因此，在这项研究中，我们旨在研究 TNAP 在成骨细胞分化中的精确作用。可逆 TNAP 抑制剂左旋咪唑抑制野生型成骨细胞中骨分化标志物基因的表达。Alpl 过表达分别增加了主成骨转录因子基因 runt 相关转录因子 2（Runx2）和 Sp7 以及成熟成骨细胞和骨细胞标志物基因骨γ-羧基谷氨酸蛋白 2（Bglap2）和牙本质基质蛋白 1（Dmp1）的表达在 Alpl 缺陷型成骨细胞中。TNAP 调节 Runx2 的表达，进而调节除 Dmp1 之外的所有其他成骨细胞标志物的表达。Dmp1 的表达不依赖于 RUNX2，但依赖于 Runx2 缺陷型成骨细胞中细胞外 P 浓度。这些结果表明，TNAP 作为成骨分化调节剂的功能，要么通过调节 Runx2 的表达，要么通过控制细胞外 P 浓度。
