Department of Orthodontics, School of Dentistry, University of Bonn, Germany.
Eur J Orthod. 2009 Dec;31(6):565-71. doi: 10.1093/ejo/cjp053. Epub 2009 Jul 27.
Previous studies have indicated that periodontal ligament (PDL) cells demonstrate osteogenic potential and osteoblastic differentiation via the extracellular signal-regulated kinase (ERK) pathway under mechanical stress in vitro and in vivo. This study aimed to further analyse this regulatory process experimentally in the rat. The right upper first molars of 25 twelve-week-old male Wistar anaesthetized rats were loaded with forces in order to be moved mesially. Constant forces for 4 hours of 0.25 and 0.5 N were applied in five animals each. Furthermore, constant forces for 2 hours of 0.1 N were applied in 10 animals and afterwards, the first and second molars were permanently separated with composite. In these animals, the antagonists were sliced and five rats were killed after 1 day and five after 2 days. As a last experiment, intermittent forces of 0.1 N and 0.25 Hz were applied in five different animals for 4 hours. The untreated contralateral sides served as the control. Paraffin-embedded sections were analysed by immunohistochemistry for proliferating cell nuclear antigen (PCNA), runt-related transcription factor 2 (Runx2/Cbfa1), and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2). Statistical analysis to determine differences between the groups was carried out using a Student's t-test. In selected areas under tension, the proportion of pERK1/2-positive cells was increased compared with those in control teeth under all types of loading, whereas these proportions in selected areas under pressure were increased only after the application of intermittent forces. In representative areas, both under tension and pressure, the proportion of Runx2-positive cells decreased after the application of constant forces. After the application of constant forces for 4 hours in representative areas, both under tension and pressure, the proportion of PCNA-positive cells was lower than those in control teeth. The involvement of pERK1/2, Runx2/cbfa-1, and PCNA in the reaction of PDL cells to different load regimens was verified.
先前的研究表明，牙周膜（PDL）细胞在体外和体内的机械应力下通过细胞外信号调节激酶（ERK）途径表现出成骨潜能和成骨细胞分化。本研究旨在通过实验进一步分析大鼠的这种调控过程。25 只 12 周龄雄性 Wistar 麻醉大鼠的右上第一磨牙被加载力以向近中移动。5 只动物各施加 0.25 和 0.5 N 的持续 4 小时力。此外，10 只动物施加 0.1 N 的持续 2 小时力，然后用复合材料永久分离第一和第二磨牙。在这些动物中，拮抗剂被切片，其中 5 只动物在第 1 天和 5 只动物在第 2 天死亡。最后一个实验中，5 只不同的动物施加 0.1 N 和 0.25 Hz 的间歇力 4 小时。未处理的对侧作为对照。通过免疫组织化学分析石蜡包埋切片中的增殖细胞核抗原（PCNA）、 Runt 相关转录因子 2（Runx2/Cbfa1）和磷酸化细胞外信号调节激酶 1/2（pERK1/2）。使用 Student's t 检验对组间差异进行统计学分析。在所有类型的加载下，与对照牙相比，在张力作用下选择区域的 pERK1/2 阳性细胞比例增加，而在压力作用下选择区域的 pERK1/2 阳性细胞比例仅在施加间歇力后增加。在代表性区域，无论是在张力还是压力下，施加持续力后 Runx2 阳性细胞的比例均下降。在代表性区域施加 4 小时持续力后，无论是在张力还是压力下，PCNA 阳性细胞的比例均低于对照牙。验证了 pERK1/2、Runx2/cbfa-1 和 PCNA 在牙周膜细胞对不同负荷方案反应中的作用。
