The role of mTert-expressing stem cells in tooth formation and renewal

描述(申请人提供)：成人牙齿干细胞在小鼠切牙的持续更新中起着关键作用。虽然最近的功能丧失和功能获得研究已经开始确定与维持正常牙齿形态发生和更新有关的关键因素，包括Wnt/b-catenin信号转导，但这些细胞的标记缺乏阻碍了我们对它们的遗传特征和在切牙中的位置的了解。因此，建立直接鉴定、分离和研究这些细胞的工具将大大促进我们的 了解它们在牙齿生物学中的作用，这最终可能导致改进一系列疾病的治疗选择，包括那些影响牙齿的疾病。端粒酶(TERT)活性可防止细胞衰老，是维持再生组织中干细胞所必需的。最近对人类牙齿的分析发现，在可能的牙齿干细胞中存在端粒酶活性。我们已经建立并验证了转基因报告鼠系(mTert-GFP、mTert-Creer和mTert-RTTA)，允许对表达端粒酶的细胞进行鉴定、分离和遗传操作。此前，我们已经证明mTert-GFP的表达标志着血液和肠道中表达端粒酶的ES细胞、iPS细胞和自我更新组织干细胞。此外，最近的初步研究表明，mTert的表达标志着一群可能的骨髓间充质干细胞。此外，Wnt/b-catenin信号在该人群中的稳定导致与该人群的丧失相一致的骨稳态的戏剧性变化。有趣的是，这些小鼠还表现出多余的牙齿形成，这表明mTert的表达标志着一群可能参与牙齿更新的牙齿干细胞。考虑到我们惊人的初步结果，我们假设mTert的表达是切牙内牙齿干细胞的生物标记物。对mTert表达细胞的进一步研究将使我们能够确定牙齿更新的因素和途径。因此，本研究的目的是：1)鉴定表达mTert的牙细胞的表型和功能；2)确定Wnt/b-catenin信号在mTert表达的牙细胞中的作用。 公共卫生相关性：缺乏明确的牙齿干细胞标志物阻碍了我们对这些细胞的自我更新和分化潜力以及它们在组织再生中的预期作用的了解。我们开发了一种独特的小鼠模型，使我们能够研究表达端粒酶的干细胞在牙齿生物学中的作用。这项研究的结果将确定一个离散的牙齿干细胞群体并对其进行功能表征，这可能最终导致影响牙齿的疾病的治疗方案得到改进。

DESCRIPTION (provided by applicant): Adult dental stem cells play a critical role in the continual renewal of the mouse incisor. Although recent loss and gain of function studies have begun to define key factors involved in maintaining normal tooth morphogenesis and renewal, which include Wnt/b-catenin signaling, the lack of markers for these cells has hampered our understanding of their genetic characteristics and location within the incisor. Therefore, establishing the tools to directly identify, isolate and study these cells will greatly advance our understanding of their role in tooth biology, which may ultimately lead to improved therapeutic treatment options for a wide range of diseases, including those affecting teeth. Telomerase (Tert) activity prevents cellular senescence and is required for maintenance of stem cells in regenerative tissues. Recent analysis of human teeth has identified telomerase activity within putative dental stem cells. We have generated and validated transgenic reporter mouse lines (mTert-GFP, mTert-CreER and mTert-rtTA) that allow for the identification, isolation and genetic manipulation of telomerase-expressing cells. Previously, we have shown that mTert-GFP expression marks telomerase-expressing ES cells, iPS cells and self-renewing tissue stem cells in blood and intestine. In addition, recent preliminary studies indicate that mTert expression marks a population of bone marrow-derived putative mesenchymal stem cells. Moreover, stabilization of Wnt/b-catenin signaling within this population results in dramatic changes in bone homeostasis consistent with a loss of this population. Interestingly, these mice also exhibit supernumerary tooth formation indicating that mTert expression marks a population of putative dental stem cells involved in tooth renewal. Given our striking preliminary results we hypothesize that mTert expression is a biomarker for dental stem cells within the incisor. Further study of mTert-expressing cells will allow us to identify the factors and pathways that underlie tooth renewal. Therefore, this proposal aims to 1) phenotypically and functionally characterize mTert-expressing dental cells and to 2) define the role of Wnt/b- catenin signaling in mTert-expressing dental cells. PUBLIC HEALTH RELEVANCE: A lack of definitive dental stem cell markers has hampered our understanding of the self- renewal and differentiation potential of these cells as well as thei prospective role in tissue regeneration. We have developed a unique mouse model that allows us to investigate the role of telomerase-expressing stem cells in tooth biology. Results from this study will identify and functionally characterize a discrete population of dental stem cells which may ultimately lead to improved therapeutic treatment options for diseases affecting teeth.