应力微环境下Twist1调控牙槽骨-牙周膜界面组织改建的转录机制

The interface linking alveolar bone (AB) and periodontal ligament (PDL) is the key anatomic structure of periodontal tissue remodeling during orthodontic tooth movement. Twist1 is an important transcription factor expressed in this interface. Recently, we found that decreased expression of periostin in PDL could result in defected fiberious connection in (Twist1 f/+; Twist2 Cre/+) mutant mice. Additionally, Sost gene deletion or sclerostin monoclonal antibody injection could repair the periodontal tissue defects in Postn KO mice. Accordingly, we hypothesize that Twist1 could up-regulate the expression of Postn by binding with Twist-box element in stress microenvironment, which locates in the upstream of Postn. Periostin could promote the cross-linking of periodontal ligament fibers. By binding with integrin αvβ3 on osteoblast membrane, periostin could also activate FAK and Akt/PKB pathway, affect the differentiation and maturation of osteoblast towards osteocyte, and reduce sclersotin secretion，thus enabling periodontal tissue remodeling and mechanotransduction. We plan to establish Twist1 cKO (Postn-Cre/ERT2; Twist1 f/f) which conditionally knock out Twist1 in periodontal tissue, and Postn KO mice model, then apply lentivirus and plasmid transfection in vitro to overexpress or silence Twist1 and Postn gene in osteoblasts and fibroblasts. By investigating the mechanism of Twist1-mediated AB-PDL interface remodeling in stress microenvironment, this study aims to elucidate how AB-PDL interface would response to stress, and to provide new theoretical foundation and perspective in mechanotransduction.

牙槽骨-牙周膜界面是正畸牙移动牙周组织改建的关键结构，Twist1是该界面的重要转录因子。我们发现（Twist1 f/+; Twist2 Cre/+）小鼠牙周膜和牙槽骨的periostin表达下降，纤维连接松散；Sost基因缺失或注射sclerostin抗体能修复Postn KO小鼠的牙周组织缺陷。据此猜想：应力作用下Twist1通过结合Twist-box上调Postn表达；periostin可促进纤维交联，与整合素αvβ3结合激活FAK及Akt/PKB通路而降低Sost表达，最终实现机械力生物学转导，调控牙周组织改建。本课题拟构建Twist1 cKO（Postn-Cre/ERT2; Twist1 f/f）和Postn KO小鼠，采用慢病毒和质粒转染使Twist1和Postn基因过表达或沉默，研究应力微环境下Twist1与牙周组织改建的关联，为深入理解生物力学响应机制提供新的基础和视角。

牙槽骨-牙周膜界面是正畸牙移动牙周组织改建的关键结构，Twist1是该界面的重要转录因子。本课题通过构建Postn-Cre/ERT2工具鼠和Twist1 flox/+工程鼠，结合基因工程技术、细胞生物学、分子生物学等方法与技术，对Twist1调控牙槽骨改建的分子机制进行了初步研究。首先，构建他莫昔芬诱导的牙周膜特异性表达Cre重组酶的Postn-Cre/ERT2工具鼠，运用lineage tracing将Cre重组酶表达位置与Periostin表达位置共定位，确定该工具鼠的牙周膜特异性高表达，在其他组织内的散在表达。进一步构建Twist1 flox/+工程鼠，配对获得基因型为Postn-Cre/ERT2; Twist1 flox/flox的小鼠，通过小鼠单侧下颌后牙应力缺失模型发现Twist1对维护骨稳态方面的重要作用。随后培养TGF-β1诱导的肌成纤维细胞，发现肌成纤维细胞分化过程中Periostin表达上调，Periostin亦可促进成骨相关基因和蛋白的表达，由此确定Periostin是牙周膜肌成纤维细胞向骨组织传递生物学信号的重要功能蛋白，并且Periostin在牙周膜中的表达变化参与了牙周组织改建的生物学过程。综合上述结果，本研究为探讨应力微环境下Twist1与牙周组织改建的关联奠定了坚实的工作基础，同时为深入理解牙周膜复合体生物力学响应机制提供新的基础和视角。