牙周膜成纤维细胞外泌体递送的骨保护素对再植牙根吸收的保护作用及机制研究

牙再植术失败的重要原因为牙根吸收，因具体机制不清难以有效预防。骨保护素（osteoprotegerin, OPG）是抑制骨吸收的关键保护分子，在牙根吸收微环境即牙周膜中抑制牙根吸收的作用机制尚无系统研究。前期实验发现：OPG敲除小鼠发生根吸收；牙周膜成纤维细胞高表达OPG；其分泌外泌体中含有大量OPG，能被破骨前体细胞摄取；沉默外泌体中的OPG促进破骨前体细胞增殖。据此本课题提出“牙周膜成纤维细胞可通过外泌体中的OPG作用于破牙细胞和牙周膜而保护牙根，减少根吸收”。本项目将在前期实验的基础上，通过在、离体实验，敲减和过表达OPG及建立再植牙根吸收疾病模型，重点探讨：①牙周膜微环境中OPG的主要细胞来源；②OPG保护牙根的作用和可能机制；③外泌体是否为OPG的主要运送方式；④通过引入富含OPG的外泌体“预防”或“挽救”再植牙根吸收。本课题有望为牙根吸收预防和治疗提供理论依据。

Root resorption is an adverse outcome of tooth replantation. However, no efficient approaches are available for the protection and repair of root resorption. Osteoprotegerin (OPG) has revealed as a powerful inhibitor of bone resorption and plays a critical role in root protection. However, little is known about its molecular mechanisms underlying inhibition of root resorption in the periodontal ligament. Our preliminary results confirmed that osteoprotegerin-knockout mice developed root resorption. OPG was highly expressed in periodontal fibroblasts. The exosomes released by periodontal fibroblasts contained plenty of OPG which can be uptaken by osteoclast precursors. If OPG was removed from exosomes by genetic methods, the proliferation of osteoclast precursors increased. Accordingly, we propose that periodontal fibroblasts could secrete exsomes-encapsulated OPG, which could have some effects on odontoclasts to inhibit root resorption. By OPG knockdown or overexpression in vivo and in vitro, and establishing root resorption models of tooth replantation, this project aimed mainly to investigate: ①the main cell sources of OPG in periodontal ligament microenvironment; ②the roles of OPG in tooth protection and the possible mechanisms; ③whether OPG mainly delivered by exosomes; ④ whether the exsomes-encapsulated OPG could prevent the root resorption. The results are expected to reveal a novel mechanism responsible for the prevention and treatment strategies for root resorption.