Reaction of intercellular network of osteocytes in alveolar bone during experimental tooth movement

骨细胞埋藏在骨基质中，在邻近的骨细胞和/或骨表面的成骨细胞之间形成复杂的细胞网络。目前认为，骨细胞在骨重建中起着非常重要的作用。然而，机械应力对正畸牙移动过程中牙槽骨中的骨细胞及其细胞间网络的影响还知之甚少。本研究的目的是利用形态计量学、免疫组织化学和原位杂交技术检测实验性牙齿移动过程中受压侧和张力侧牙槽骨中细胞间网络的变化。动物和实验性牙齿移动：在8周龄雄性Wistar大鼠上第一磨牙被镍钛超弹性钢丝(直径0.01英寸)以平均10g的载荷近中移动。我们先前报道，该方法适用于观察玻璃化牙周组织附近的骨细胞。建立了用Alexa 488标记的鬼臼乙素和DAPI在激光共聚焦扫描显微镜(CLSM)下进行骨细胞免疫荧光观察的方法。激光共聚焦显微镜下可见玻璃化牙周组织邻近的几个骨细胞出现染色质凝集、核碎裂和细胞质破坏。此外，我们还进行了TUNEL法和电子显微镜观察，以确定骨细胞的细胞死亡。结果表明，在实验性牙齿移动过程中，骨细胞的死亡可能是由于成骨细胞与骨细胞之间的细胞间网络的破坏，而不是由于机械应力对骨细胞的直接反应。为了了解牙槽骨细胞间网络的动力学，有必要进一步研究与骨代谢相关的几种生长因子和细胞因子的参与。

Osteocytes are buried within the bone matrix and form complicated cellular networks between neighboring osteocytes and/or osteoblasts on bone surfaces. It is proposed that osteocytes have very important role of bone remodeling. However little is known on the effect of mechanical stress on osteocytes and their intercellular network in the alveolar bone during orthodontic tooth movement. The purpose of this study was to examine the intercellular network in alveolar bone on pressure and tension sides during experimental tooth movement, using morphometrical analysis, immunohistochemistry and in situ hybridization technique.1. Animals and experimental tooth movement.In 8-week-old male Wistar rats, the upper first molar was forced to move mesially with an average load of 10g by a nickel-titanium superelastic wire (0.01 inch in diam.). We previously reported that the method was suitable for the observation of osteocytes adjacent to the hyalinized periodontal tissue.2. Morphological change of osteocytes during experimental tooth movement.We developed a method to observe osteocytes by immunofluoresence with Alexa 488 labelled phalloidin and DAPI under confocal laser scanning microscopy (CLSM). CLSM showed that chromatin condensation, nuclear fragmentation and cytoplasmic destruction appeared in several osteocytes adjacent to the hyalinized periodontal tissues. Also, we carried out TUNEL method and electronmicroscopic observation to identify the cell death of osteocytes. The results indicate that cell death of osteocytes during experimental tooth movement may be due to disruption of intercellular network between osteoblasts and osteocyte, but not to direct reaction of osteocytes by mechanical stress. To know the dynamics of intercellular network in alveolar bone, further investigations concerning involvement of several growth factors and cytokines related to bone metabolism is necessary.