A study on the morphological changes of osteocytes in rat alveolar bone during orthodontic tooth movement

本研究的目的是：1)用免疫组织化学方法检测大鼠正畸牙移动过程中牙槽骨中骨细胞的形态变化；2)确定骨细胞代谢的分子标志物。本研究选用8周龄雄性Wistar大鼠。按照Igarashi等人的描述，使用名义尺寸为0.012英寸的镍钛钢丝膨胀弹簧将上颌第一磨牙颊向移动。(1998年)。在牙齿移动3、6、12、24小时、2、4、7、10和14天后处死动物。实验结束后，动物用4%多聚甲醛+0.5%戊二醛在0.1M PB、pH 7.4的溶液中固定，用10%EDTA溶液脱钙，加工成石蜡包埋。用苏木精-伊红染色或骨钙素抗体、I型、II型和X型胶原及肌动蛋白细丝对6亩厚切片进行染色。结果表明：1)前驱体和成熟骨钙素是检测牙槽骨和骨形成细胞代谢变化的合适分子标志物。2)正畸牙移动3h后，第一磨牙5个牙根的牙周组织压力侧均出现透明组织。10.3)免疫组织化学染色显示，对照组大鼠骨细胞胞浆和细胞突起呈强阳性染色。尤其是年轻的骨细胞染色较深。与之相反，第1天透明组织邻近的骨细胞胞浆染色变弱，第4天其细胞突起的染色消失。结果表明，正畸牙齿移动早期，由于牙周组织细胞间通讯的消失，邻近透明变性组织的骨细胞发生细胞死亡。

The purposes of the present study were 1) to examine the morphological changes of osteocytes in rat alveolar bone during orthodontic tooth movement using immunohistochemistry for actin filaments and 2) to determine a molecular marker for osteocyte metabolism. Eight-week-old male Wistar rats were used in this study. The maxillary first molars were moved buccally by using a expansive spring of Ni-Ti wire with a nominal size of 0.012 inch as described by Igarashi et al. (1998). The animals were killed after 3, 6, 12, 24 hours, 2, 4, 7, 10 and 14 days of tooth movement. After experiments, the animals were fixed with 4 % paraformaldehyde plus 0.5 % glutaraldehyde in 0.1 M PB, pH 7.4, decalcified with 10 % EDTA solution and processed into paraffin embedding. Six-mu in-thick sections were stained with hematoxilin-eosin or antibodies for osteocalcin, typesI,II and X collagen and actin filaments. The results were as follows ;1) Precursor and mature osteocalcin was a proper molecular marker for examining the metabolic changes of alveolar bone and bone-forming cells.2) After 3 hours of orthodontic tooth movement, hyaline tissue appeared in the pressure side of the periodontal tissue of all five roots of the first molar. The hyaline tissue spread and almost dessapered at day 10.3) Immunohistochemistry for actin filament showed intense staining in cytoplasm and cellular processes of osteocytes in control group. Especially young osteocytes showed intense staining. In contrast, the staining of osteocyte cytoplasm adjacent to the hyaline tissue became weak at day 1 and the staining of its cellular processes disappeared at day 4.These results demonstrated that osteocytes adjacent to the hyaline degeneration tissue became cell death during early stage of orthodontic tooth movement due to the disappearance of intercellular communication between the periodontal tissue cells.