Fujita S, Yamaguchi M, Utsunomiya T, Yamamoto H, Kasai K
Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Orthod Craniofac Res. 2008 Aug;11(3):143-55. doi: 10.1111/j.1601-6343.2008.00423.x.
Recent studies have demonstrated that low-energy laser irradiation stimulates bone formation in vitro and in vivo. However, very little is known about the effects of laser irradiation on osteoclastogenesis. The receptor activator of the nuclear factor-kB (RANK) / RANK ligand (RANKL) / osteoprotegerin (OPG) system is essential and sufficient for osteoclastogenesis. The present study was designed to examine the effects of low-energy laser irradiation on expressions of RANK, RANKL, and OPG during experimental tooth movement.
To induce experimental tooth movement in rats, 10 g of orthodontic force was applied to the molars. Next, a Ga-Al-As diode laser was used to irradiate the area around the moved tooth and the amount of tooth movement was measured for 7 days. Immunohistochemical staining with RANK, RANKL, and OPG was performed. Real time PCR was also performed to elucidate the expression of RANK in irradiated rat osteoclast precursor cells in vitro.
In the irradiation group, the amount of tooth movement was significantly greater than in the non-irradiation group by the end of the experimental period. Cells that showed positive immunoreactions to the primary antibodies of RANKL and RANK were significantly increased in the irradiation group on day 2 and 3, compared with the non-irradiation group. In contrast, the expression of OPG was not changed. Further, RANK expression in osteoclast precursor cells was detected at an early stage (day 2 and 3) in the irradiation group.
These findings suggest that low-energy laser irradiation stimulates the velocity of tooth movement via induction of RANK and RANKL.
近期研究表明，低能量激光照射在体外和体内均可刺激骨形成。然而，关于激光照射对破骨细胞生成的影响却知之甚少。核因子-κB受体激活剂（RANK）/RANK配体（RANKL）/骨保护素（OPG）系统对破骨细胞生成至关重要且充分。本研究旨在探讨低能量激光照射对实验性牙齿移动过程中RANK、RANKL和OPG表达的影响。
为诱导大鼠实验性牙齿移动，对磨牙施加10g正畸力。接下来，使用Ga-Al-As二极管激光照射移动牙齿周围区域，并测量7天内的牙齿移动量。进行RANK、RANKL和OPG的免疫组织化学染色。还进行了实时PCR以阐明体外照射大鼠破骨细胞前体细胞中RANK的表达。
在照射组中，到实验期结束时，牙齿移动量显著大于未照射组。与未照射组相比，照射组在第2天和第3天对RANKL和RANK一抗呈阳性免疫反应的细胞显著增加。相比之下，OPG的表达没有变化。此外，在照射组的早期阶段（第2天和第3天）检测到破骨细胞前体细胞中的RANK表达。
这些发现表明，低能量激光照射通过诱导RANK和RANKL来刺激牙齿移动速度。
