Department of Endodontics, School & Hospital of Stomatology, Tongji University, Shanghai Engineering Research Center of Tooth Restoration and Regeneration, Shanghai, China.
J Mol Histol. 2018 Jun;49(3):329-338. doi: 10.1007/s10735-018-9771-6. Epub 2018 Apr 11.
Epithelial rests of Malassez (ERM), the only odontogenic epithelial structures in periodontal tissue, are proposed to correlate with root resorption, but the detailed mechanism remains unclear. Osteoprotegerin (OPG), the main inhibitor of osteoclastogenesis, plays a pivotal role in inhibiting root resorption, and ERM cells express OPG mRNA in vitro. Thus, in this study, we aimed to clarify OPG expression in ERM in vivo and to explore the role of OPG in ERM to determine whether ERM are associated with root resorption via OPG. We established Opg-knockout (Opg-KO) mice and detected the OPG expression in ERM by immunohistochemical staining in 4-, 6-, 10-, 26- and 52-week-old mice. The ERM of wild-type (WT) mice and Opg-KO mice were evaluated histologically at 4, 10 and 26 weeks of age. Orthodontic root resorption models were established, maxillae were collected after 4 weeks, and ERM were analysed by histomorphometric analysis. In our study, OPG displayed sustained expression in ERM, and OPG deficiency caused the destruction of ERM, characterized by irregular morphology and reduced numbers. Moreover, after orthodontic treatment, the loss of OPG severely damaged ERM, aggravating root resorption. Together, our results demonstrated that ERM expressed the OPG protein in vivo and that OPG deficiency resulted in morphological and quantitative damage to ERM. Furthermore, ERM may be associated with root resorption via OPG, thus helping to explain the mechanism underlying root resorption.
牙周膜上皮剩余（ERM）是牙周组织中唯一的牙源性上皮结构，被认为与牙根吸收有关，但详细机制尚不清楚。护骨素（OPG）是破骨细胞生成的主要抑制剂，在抑制牙根吸收中起关键作用，体外ERM 细胞表达 OPGmRNA。因此，本研究旨在阐明体内 ERM 中的 OPG 表达，并探讨 OPG 在 ERM 中的作用，以确定 ERM 是否通过 OPG 与牙根吸收有关。我们建立了 Opg 基因敲除（Opg-KO）小鼠，并通过免疫组织化学染色检测 4、6、10、26 和 52 周龄小鼠 ERM 中的 OPG 表达。在 4、10 和 26 周龄时，对 WT 小鼠和 Opg-KO 小鼠的 ERM 进行组织学评估。建立正畸牙根吸收模型，4 周后收集上颌骨，通过组织形态计量学分析研究 ERM。在本研究中，OPG 在 ERM 中持续表达，OPG 缺乏导致 ERM 破坏，表现为形态不规则和数量减少。此外，正畸治疗后，OPG 的丢失严重破坏 ERM，加重牙根吸收。总之，我们的结果表明 ERM 在体内表达 OPG 蛋白，OPG 缺乏导致 ERM 形态和数量损伤。此外，ERM 可能通过 OPG 与牙根吸收有关，从而有助于解释牙根吸收的机制。
