Dickkopf1调控血管形成的分子机制研究

Angiogenesis is the foundation of periodontal tissue remodeling, and closely related with bone remodeling during orthodontic tooth movement. Notch signal maintains the vascular homeostasis by regulating the proliferation and differentiation of tip cells and stalk cells in the process of angiogenesis. Dickkopf1 (Dkk1) is the antagonist of canonical Wnt/β-catenin signal pathway. Recently, we unexpectedly found that osteoblast-specific Dkk1 overexpression driven by 2.3 kb Col1a1 promoter can inhibit neovessel formation significantly. Our hypothesis is that the mechanism may be the coordinative regulation of Wnt and Notch signals. Therefore, this project intends to investigate the molecular mechanism that how Dkk1 regulates angiogenesis and impacts bone mineralization indirectly via the crosstalk between Wnt and Notch signal pathways. We plan to establish epithelium-specific Tie2 promoter driven Dkk1 overexpression transgenic mice, as well as subcutaneous and corneal neovascularization mouse models in vivo； and overexpress or silence Dkk1 in human umbilical vascular epithelial cells with plasmid and lentivirus transfection in vitro. The implementation of this project might make a breakthrough in the molecular mechanism of angiogenesis, and further clarify the biological mechanism of orthodontic tooth movement.

血管形成是牙周组织改建的基础，与正畸牙移动骨重塑密切相关。在血管形成中，Notch信号通过调控尖细胞和柄细胞增殖与分化的动态平衡以维持血管稳态。Dickkopf1（DKK1）是经典Wnt/β-catenin信号通路的拮抗剂，近期我们意外地发现2.3 kb Col1a1启动子驱动的成骨细胞特异性过表达DKK1能显著抑制血管形成，推测其机制可能是DKK1通过Wnt和Notch信号通路协同作用的结果。据此，本课题拟建立小鼠皮下、角膜血管新生模型，构建Tie2启动子驱动的内皮细胞特异性过表达DKK1转基因小鼠；在体外采用质粒和慢病毒转染使DKK1在人脐静脉内皮细胞过表达或沉默，深入研究DKK1通过Wnt信号和Notch信号的级联串话调控血管形成的分子机制及其对骨重塑的间接影响。本课题的成功实施，有望在血管形成分子机制的研究领域产生新的突破，可为进一步阐明正畸牙移动生物学机理提供新的思路。

血管形成是牙周组织改建的基础，与正畸牙移动骨重塑密切相关。而骨组织作为适应性反馈调控系统，与机械信号、生化信号、神经信号持续性整合。在血管形成中，Notch信号通过调控尖细胞和柄细胞增殖与分化的动态平衡以维持血管稳态。Dickkopf1（DKK1）是经典Wnt/β-catenin信号通路的拮抗剂，本课题建立小鼠皮下血管新生模型，构建Cdh5启动子驱动的内皮细胞特异性过表达DKK1转基因小鼠；在体外采用慢病毒转染使DKK1在人脐静脉内皮细胞过表达，发现并得出以下结果：1)在血管形成的过程中，DKK1对血管内皮细胞的增殖无明显影响，但对细胞的分化能力有调控作用, 而β-catenin信号通路极有可能位于Notch信号通路的上游，二者或存在级联串话关系。2) Cdh5驱动内皮细胞中DKK1表达的增加引起股骨远端生长板增宽、肥大细胞比重增大等生长板改变，导致股骨和牙槽骨骨小梁密度增加、髓腔缩窄等骨量增多、破骨活动减弱的现象，与软骨细胞的分化、骨小梁的形成密切相关。3）牙周组织和骨组织中DKK1的高表达却并未导致明显的组织破坏。该研究结果初步阐释骨形成、软骨发育与血管形成之间可能存在的关系，为血管形成分子机制的研究领域以及丰富骨骼系统组织调控理论提供新的证据，可为进一步阐明正畸牙移动生物学机理提供新的思路。