Molecular biological and histomorphometrical study on bone remodeling and root resorption during orthodontic tooth movement.

本研究用非放射性地高辛标记的cRNA原位杂交组织化学方法，研究了大鼠上颌牙槽骨单位中骨桥蛋白(OPN)和骨钙素(OSC)的基因表达，以期在一次加载后产生完全改建的同步波。从这些实验中我们发现，在体内，骨细胞对机械负荷有反应，表达OPN而不表达OSC，这与随后的骨吸收有关。0d时，在7周龄大鼠上颌第一磨牙颊根中隔远中的成骨细胞表面可见OSC表达的强阳性信号，但未见OPN表达。在第一和第二磨牙之间插入橡皮筋后，面对根间隔远中表面的牙周膜被压缩，第1天的牙周间隙比…天变窄更多的0。同时，在压缩应变环境下，神经根间隔远端表面覆盖的细胞OSC mRNA阳性信号消失。相反，OPN的mRNA阳性信号在根间隔远中半部基质内的细胞内有较强的表达，而在近中半部和颊根根尖周围的细胞中没有表达，第一磨牙倾斜移动后，这些部位的压应变必然会发生变化。成骨细胞胞核较大，胞核呈棕黄色，骨细胞陷窝较0d增大。第3天，随着PDL继续受压，面对PDL的骨面衬里细胞消失，神经根间隔远端骨吸收活跃。牙槽骨的破坏吸收区明显，周围有大量的破骨细胞形成Howship‘s陷窝和大量的单核细胞，骨基质中的OPN m RNA表达于第1天，在骨细胞、Howship’s陷窝附近的多核细胞(破骨细胞)和单个核细胞中有较强的表达。相反，在这些区域未观察到OSC的基因表达。这些结果表明，在机械力刺激的改建周期开始时，骨细胞中的OPN促进破骨细胞附着和激活(阶段1)导致骨吸收阶段(阶段2)，骨细胞在机械传感器中起重要作用。较少

In the present study, the gene expression for osteopontin (OPN) and osteocalcin (OSC) in the alveolar bone was investigated by in situ hybridization histochemistry with non-radioisotopic digoxigenin 11-UTP labeled cRNA prove for OPN and OSC in rat maxillary dent-alveolar unit containing molars and intact PDL following a single loading to produce a well synchronized wave of complete remodeling. From these experiments we found osteocytes respond to mechanical loading in vivo with expression of mRNA for OPN but not for OSC,to associate with subsequent bone resorption. On day 0 an intense positive signal of mRNA for OSC but not OPN was demonstrable at osteoblasts on the distal surface of the interradicular septum of buccal roots of the maxillary first molar of 7-week-old rat. After insertion of an elastic band between the first and second molars the PDL facing the distal surface of the interradicular septum was compressed and the periodontal space on day 1 became narrower than that on day … More 0. At the time the positive signal of OSC mRNA disappeared from cells covering the distal surface of interradicular septum under the compressive strain environment. On the contray, a positive signal of mRNA for OPN was intensely expressed at oseocytes within the matrix in the distal half of the interradicular septum but not in the mesial half, and around the apex of buccomesial root, where the change of consequent compressive strains following a tipping movement of the first molar must occur. Thses osteocytes had large and roudish nuclei, and their osteocyte lacunae became enlarged compared with those on day 0. On day 3, as the compression of PDL continued, lining cells disappeared from the bone surface facing PDL and bone resorption on the distal region of the interradicular septum actively occured. The undermining resorption areas of alveolar bone were prominently eveident, and there were many osteoclasts making Howship's lacunae and a plenty of mononuclear cells around resorbing bone surfaces, where bone matrix containing OPN mRNA expressing osteocytes had been present on day 1. A positive signal of OPN mRNA expressed intensely in osteocytes, multinucleated cells adjacent to Howship's lacunae, designated as osteoclasts, and mononuclear cells on day 3. On the contrary, gene expression for OSC could not be observalbe at these areas.These results suggest that at the beginning of a remodeling cycle stimulated by mechanical force, the OPN in osteocytes promotes osteoclast attachment and activation (stage 1), leading to the resorption phase (stage 2) and that osteocytes play an important role for mechanosensor. Less