Yao Shaomian, Ring Sherry, Henk William G, Wise Gary E
Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
Arch Oral Biol. 2004 Jun;49(6):451-6. doi: 10.1016/j.archoralbio.2004.01.009.
Tooth eruption is a localized event in which many of the genes required for eruption are expressed in the dental follicle. A major function of the follicle is to recruit mononuclear cells for osteoclastogenesis such that the alveolar bone can be resorbed. Osteoclastogenesis is primarily regulated by receptor activator of nuclear factor-kappa B ligand (RANKL), colony-stimulating factor-one (CSF-1) and osteoprotegerin (OPG). In the rat first mandibular molar, osteoclastogenesis is maximal at day 3 and CSF-1 is maximally expressed in the follicle at this time whereas OPG expression is reduced. Whether or not RANKL is expressed in vivo in the follicle is controversial, however. It is critical to determine this because others have shown that in partially-rescued mice null for RANKL, teeth do not erupt. This suggests that RANKL should be expressed in the follicle for eruption to occur. Thus, to precisely determine if RANKL is expressed in the follicle in vivo, laser capture microdissection (LCM) was used to excise dental follicle tissue from frozen sections followed by RNA isolation and RT-PCR. The results show that RANKL is expressed in the dental follicle at days 1-9 postnatally. The technique was confirmed by controls showing that LCM isolates of the follicle, and alveolar bone, express OPG. Also, LCM isolates of alveolar bone were positive for RANKL. Thus, RANKL has now been shown to be expressed in the follicle and it is probable that interactions between it, CSF-1 and OPG regulate locally the osteoclastogenesis needed for tooth eruption.
牙齿萌出是一个局部性事件，其中许多与萌出所需的基因在牙囊表达。牙囊的一个主要功能是募集单核细胞用于破骨细胞生成，以便牙槽骨能够被吸收。破骨细胞生成主要受核因子κB受体激活剂配体（RANKL）、集落刺激因子-1（CSF-1）和骨保护素（OPG）调节。在大鼠第一下颌磨牙中，破骨细胞生成在第3天达到最大值，此时CSF-1在牙囊中最大程度表达，而OPG表达降低。然而，RANKL在牙囊中的体内表达情况存在争议。确定这一点至关重要，因为其他人已经表明，在RANKL基因缺失的部分挽救小鼠中，牙齿不会萌出。这表明RANKL应该在牙囊中表达才能发生萌出。因此，为了精确确定RANKL在体内牙囊中是否表达，使用激光捕获显微切割（LCM）从冰冻切片中切除牙囊组织，随后进行RNA分离和RT-PCR。结果显示，出生后1-9天RANKL在牙囊中表达。通过对照证实了该技术，对照显示牙囊和牙槽骨的LCM分离物表达OPG。此外，牙槽骨的LCM分离物RANKL呈阳性。因此，现已证明RANKL在牙囊中表达，并且它与CSF-1和OPG之间的相互作用可能局部调节牙齿萌出所需的破骨细胞生成。
