The role of Wnt1 in posteruptive tooth development

转基因小鼠模型是分析体内基因功能的重要工具，并为当前牙齿发育的分子理解提供了基础。这些知识不仅有助于诊断患者的牙齿异常，而且还为再生牙科提供了新的治疗策略。特别令人感兴趣的是控制干细胞分化为骨和牙齿形成细胞的信号通路。我们的研究所专门从事人类遗传性骨病小鼠模型的骨和牙齿的组织学和分子分析。最近已经发现，成骨不全的形式是由WNT1基因突变引起的。由于WNT 1在牙齿形成神经嵴细胞的发育中具有核心作用，我们分析了诱导型WNT 1过表达的小鼠模型的牙齿表型。使用显微计算机断层扫描对12周龄小鼠进行的分析表明，WNT 1对颌骨具有深刻的骨合成代谢作用。此外，6周龄小鼠的组织学检查显示，Wnt 1抑制牙本质形成并促进牙骨质形成。因此，我们的假设是，Wnt 1控制间充质干细胞分化成骨细胞，成牙本质细胞和成牙骨质细胞。DFG Nachwuchsakademie Zahnmedizin计划的这项资助的目的是描述Wnt 1过表达小鼠的出生后牙齿发育的特征，并首次深入了解Wnt 1对体外成牙骨质细胞分化的分子效应。将解决以下问题：1）Wnt 1如何调节牙根发育和牙齿萌出？为了确定Wnt 1对萌出前牙齿发育的影响，将通过显微计算机断层扫描、组织学和组织化学分析出生后立即过表达Wnt 1的转基因小鼠。2）Wnt 1如何调节骨和牙齿组织的质量以及Wnt 1长期过表达的影响是什么？将使用免疫组织化学和微量分析方法研究Wnt 1过表达小鼠的骨和牙齿组织的质量和功能。此外，我们还将分析Wnt 1长期过表达（9周）的小鼠。3）Wnt 1在体外是如何调控成牙骨质细胞分化的？我们将用重组Wnt 1处理成牙骨质细胞系（OCCM-30），并使用矿化试验和成牙骨质细胞分化标记物的QPCR分析来分析这些细胞。这些分析应该为随后的DFG资助提供基础，在DFG资助中，我们希望评估抑制Wnt 1及其假定受体对转基因小鼠牙齿发育的影响。因此，我们可以扩展牙齿发育的分子理解，并为开发Wnt 1特异性药物奠定分子基础。

Genetically modified mouse models serve as important tools for analyzing gene functions in vivo and provided the basis for the current molecular understanding of tooth development. Not only does this knowledge help with the diagnosis of dental abnormalities in patients, but it also offers new therapeutic strategies for regenerative dentistry. Of particular interest are the signaling pathways that control the differentiation of stem cells to bone- and tooth-forming cells. Our Institute is specialized on histological and molecular analysis of bone and teeth from mouse models of human genetic bone diseases. It has been recently discovered that forms of osteogenesis imperfecta are caused by mutations in the WNT1 gene. Due to the fact that WNT1 has a central role in the development of tooth-forming neural crest cells, we analyzed the dental phenotype of a mouse model with inducible Wnt1-overexpression.The analysis of 12 week old mice using micro-computed tomography scanning demonstrated a profound osteoanabolic effect of Wnt1 on the jaw. Moreover, histological examinations of 6 week old mice revealed that Wnt1 inhibits dentin formation and promotes cementum formation. Therefore, our hypothesis is that Wnt1 controls differentiation of mesenchymal stem cells to osteoblasts, odontoblasts and cementoblasts. The aim of this grant of the DFG Nachwuchsakademie Zahnmedizin initiative is to characterize the post-natal tooth development in Wnt1-overexpressing mice and to gain first insights into the molecular effects of Wnt1 on differentiation of cementoblasts in vitro.The following questions will be addressed:1) How does Wnt1 regulate root development and tooth eruption? In order to determine the effect of Wnt1 on pre-eruptive tooth development, transgenic mice with immediate post-natal overexpression of Wnt1 will be analyzed by micro-computed tomography, histology and immunohistochemistry.2) How does Wnt1 regulate the quality of bone and tooth tissues and what is the effect of long-term Wnt1 overexpression? The quality and function of bone and tooth tissues in Wnt1-overexpressing mice will be studied using immunohistochemistry and micro-analytical methods. In addition, we will analyze mice with long-term overexpression of Wnt1 (9 weeks).3) How does Wnt1 regulate the differentiation of cementoblasts in vitro? We will treat a cementoblastic cell line (OCCM-30) with a recombinant Wnt1 and analyze these cells using mineralization assays and QPCR analysis of cementoblast differentiation markers.These analyses should provide the basis for a following DFG grant, in which we would like to evaluate the effect of inhibiting Wnt1 and its putative receptors on tooth development in genetically modified mice. Thereby, we could expand the molecular understanding of tooth development and establish the molecular basis for the development of Wnt1-specific drugs in dentistry.