骨细胞是力学刺激和代谢活动调控骨重塑的重要效应细胞，活性氧簇（ROS）和去乙酰化酶1（SIRT1）在外界信号的氧化还原调控中起枢纽作用。SIRT1作为骨重塑的重要调节因子，能抑制骨硬化蛋白（SOST）的表达，影响经典Wnt通路。同时，SIRT1-FOXO是机体对ROS进行氧化防御的核心。由此推测： 外界信号通过ROS调控SIRT1的核浆转运，SIRT1通过去乙酰化SOST和FOXO，并与经典Wnt通路整合形成信号网络，在外界信号调控骨细胞代谢中发挥枢纽作用。本课题拟以ROS-SIRT1-SOST/FOXO信号网络为主线，构建骨细胞特异性SIRT1过表达转基因小鼠模型，通过咬合应力缺失小鼠模型和氧化应激小鼠模型，结合体外三维应力加载系统和氧化应激系统，多角度阐明力学刺激和代谢活动中SIRT1介导氧化还原信号对骨细胞代谢的调控机制，为促进应力微环境和病理状态下骨重塑探索新的手段。

Osteocyte is the important effector of bone to regulate the bone remodeling under mechanical stimuli and metabolic activity; reactive oxygen species (ROS) and NAD+ dependent sirtuin type 1 (SIRT1) play the pivot role in redox regulation to external signals. SIRT1, a significant regulatory factor of bone remodeling, inhibits sclerostin/SOST expression by histone deacetylation and promotes the canonical Wnt signaling pathway. Meanwhile, SIRT1-FOXO pathway is the unique oxidative defense mechanism to ROS. Our hypotheses are following: The external signals regulate the SIRT1 nucleoplasm translocation via ROS. SIRT1 may deacetylate SOST and FOXO, and integrate with canonical Wnt signaling pathway to build a redox signaling network. Then SIRT1 regulates the osteocyte metabolism via this signaling network. Therefore, this project intends to investigate the molecular mechanism that SIRT1 regulates osteocyte metabolism via ROS-SIRT1-SOST/FOXO redox signaling network. We will establish osteocyte-specific SIRT1 overexpression transgenic mice. Then we will conduct the bite unloading and the oxidative stress mice model in vivo, and set up three-dimensional mechanical loading system and oxidative stress system in vitro. The implementation of this project might enrich the theory of bone remodeling, and explore the novel method to enhance bone remodeling under mechanical and pathological microenvironment.

成骨细胞是力学刺激和代谢活动调控骨重塑的重要效应细胞,活性氧簇(ROS)和去乙酰化酶1(SIRT1)在外界信号的氧化还原调控中起枢纽作用。本课题组通过建立大鼠咬合应力缺失模型和体外培养的MC3T3-E1成骨细胞，研究了异常应力和氧化应激状态下，SIRT1-FOXO1对成骨细胞功能影响的作用机制。结果发现：（1）异常应力（生理咬合应力缺失、体外应力过载）可诱导成骨细胞的凋亡，同时SIRT1表达显著降低，FOXO1表达降低，FOXO1核转移增加。应用SIRT1激动剂或抑制剂后，可通过调节SIRT1的功能，缓解或加重成骨细胞的凋亡。表明异常应力作用下，成骨细胞的凋亡与SIRT1密切相关，其可能机制是通过增加FOXO1的核转移来实现的。（2）氧化应激状态下，成骨细胞成骨相关转录因子OSX，OCN，RUNX2表达下降，同时SIRT1表达显著降低，FOXO1表达降低。SIRT1激动剂可通过调节SIRT1的功能，缓解氧化应激对成骨细胞功能的影响。本研究揭示了SIRT1在成骨代谢中发挥的重要作用，异常应力和氧化应激可通过SIRT1-FOXO1通路调控成骨细胞的功能状态。