Mechanical loading stimulates dentin matrix protein 1 (DMP1) expression in osteocytes in vivo
Mechanical loading stimulates dentin matrix protein 1 (DMP1) expression in osteocytes in vivo
复制标题
DOI：
10.1359/jbmr.2003.18.5.807
复制
发表时间：
2003-05-01
影响因子：
6.2
通讯作者：
Pavlin, D
中科院分区：
文献类型：
--
作者：
Gluhak-Heinrich, J;Ye, L;Pavlin, D
牙本质基质蛋白1(DMP1)最初被认为是牙本质特异的。进一步的分析表明，DMP1在成熟的软骨和骨中也有表达。在骨组织中，DMPI主要在晚期成骨细胞和骨细胞中表达。DMPI属于小整合素结合配体N-连接糖蛋白家族，还包括骨桥蛋白、骨涎蛋白、牙本质涎磷蛋白等。本研究采用原位杂交和免疫细胞化学的方法，研究了机械载荷对小鼠牙齿移动模型牙槽骨中DMP1mRNA和DMPI蛋白表达的影响。在机械负荷后6h~7d的不同时间点，定量检测DMP1mRNA在机械负荷和对照部位的表达。牙齿移动模型允许同时评估骨吸收和骨形成位置。骨形成和骨吸收部位骨细胞中DMP1mRNA的表达在治疗后6h增加了2倍。4天后，DMPI在骨形成部位和骨吸收部位的表达分别增加到3.7倍和3.5倍。成骨细胞的反应相反，在整个治疗过程中，成骨细胞在骨形成部位的DMP1基因表达持续下降45%，在骨吸收部位的DMP1基因表达持续下降，在第2天达到峰值67%。用抗DMP1的C末端区肽抗体进行免疫细胞化学染色，我们发现在治疗后3d，形成侧和吸收侧的免疫反应性都比对照侧有一过性的下降。然而，在加载7天后，DMP1蛋白在形成侧和吸收侧的免疫反应性都显著增加。这些结果代表了使用该抗体的表位可用性的变化或蛋白质水平的真实变化。这些观察结果表明，在牙槽骨机械负荷后，DMP1蛋白的合成或其他蛋白质/基质相互作用正在经历动态变化。结果表明，DMPI参与了骨细胞和成骨细胞对骨机械负荷的反应。这些结果支持骨细胞改变其基质微环境以响应机械载荷的假说。
Dentin matrix protein 1 (DMP1) was originally postulated to be dentin specific. Further analysis showed that DMP1 is also expressed in mature cartilage and bone. In bone tissue, DMPI is expressed predominantly in late osteoblasts and osteocytes. DMPI belongs to the SIBLING (Small Integrin Binding Ligand N-linked Glycoprotein) family of cellular matrix proteins that also includes osteopontin, bone sialoprotein, dentin sialophosphoprotein, and others. In this study, we examined the effect of mechanical loading on expression of DMP1 mRNA and DMPI protein in alveolar bone in the mouse tooth movement model by in situ hybridization and immunocytochemistry. The expression of DMP1 mRNA was determined quantitatively in mechanically loaded and control sites of dento-alveolar tissue at several time points from 6 h to 7 days after loading. The tooth movement model allows simultaneous evaluation of bone resorption and bone formation sites. Expression of DMP1 mRNA in osteocytes increased 2-fold as early as 6 h after treatment in both the bone formation and bone resorption sites. After 4 days, DMPI expression in osteocytes increased to a maximum of 3.7-fold in the bone formation sites and 3.5-fold in the resorption sites. Osteoblasts responded in the opposite manner and showed a transient 45% decrease of DMP1 mRNA in bone formation sites and a constant decrease of DMP1 mRNA during the entire course of treatment in the bone resorption sites, with a peak inhibition of 67% at day 2. By immunocytochemistry using a C-terminal region peptide antibody to DMP1, we found that there was a transient decrease in immunoreactivity at 3 days after treatment on both the formation side and the resorption side compared with the matched contralateral control tissue. However by 7 days of loading, there was a dramatic increase in DMP1 protein immunoreactivity on both the formation side and the resorption side. These results represent changes in epitope availability using this antibody or true changes in protein levels. The observations imply that the DMP1 protein is undergoing dynamic changes in either synthesis or other protein/matrix interaction after mechanical loading of alveolar bone. The findings indicate that DMPI is involved in the responses of osteocytes and osteoblasts to mechanical loading of bone. These results support the hypothesis that osteocytes alter their matrix microenvironment in response to mechanical loading.