Liu D, Yao S, Pan F, Wise G E
Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
Eur J Oral Sci. 2005 Oct;113(5):404-9. doi: 10.1111/j.1600-0722.2005.00245.x.
Tooth eruption in the rat requires bone resorption resulting from a major burst of osteoclastogenesis on postnatal day 3 and a minor burst of osteoclastogenesis on postnatal day 10 in the alveolar bone of the first mandibular molar. The dental follicle regulates the major burst on postnatal day 3 by down-regulating its osteoprotegerin (OPG) gene expression to enable osteoclastogenesis to occur. To determine the role of receptor activator of nuclear factor-kappa B ligand (RANKL) in tooth eruption, its gene expression was measured on postnatal days 1-11 in the dental follicle. The results show that RANKL expression was significantly elevated on postnatal days 9-11 in comparison to low expression levels at earlier time-points. As OPG expression is high at this latter time-point, this increase in RANKL expression would be needed for stimulating the minor burst of osteoclastogenesis. Tumor necrosis factor-alpha enhances RANKL gene expression in vitro and it may be responsible for up-regulating RANKL in vivo. Transforming growth factor-beta1 and interleukin-1alpha also enhance RANKL gene expression in vitro but probably have no effect in vivo because they are maximally expressed early. Bone morphogenetic protein-2 acts to down-regulate RANKL expression in vitro and, in vivo, may promote alveolar bone growth in the basal region of the tooth.
大鼠牙齿萌出需要破骨细胞生成的爆发，这导致出生后第3天在第一下颌磨牙的牙槽骨中出现一次主要的破骨细胞生成爆发，以及出生后第10天出现一次较小的破骨细胞生成爆发。牙囊通过下调其骨保护素（OPG）基因表达来调节出生后第3天的主要破骨细胞生成爆发，从而使破骨细胞生成得以发生。为了确定核因子κB受体活化因子配体（RANKL）在牙齿萌出中的作用，在出生后第1 - 11天测量了牙囊中RANKL的基因表达。结果表明，与早期时间点的低表达水平相比，出生后第9 - 11天RANKL表达显著升高。由于后期这个时间点OPG表达较高，因此需要RANKL表达的这种增加来刺激较小的破骨细胞生成爆发。肿瘤坏死因子α在体外增强RANKL基因表达，它可能负责在体内上调RANKL。转化生长因子β1和白细胞介素 - 1α在体外也增强RANKL基因表达，但可能在体内没有作用，因为它们在早期就达到最大表达。骨形态发生蛋白 - 2在体外起到下调RANKL表达的作用，在体内可能促进牙齿基部区域的牙槽骨生长。
