Defining Cell Lineages in the Bladder Urothelium

描述（由申请人提供）：揭示正常组织发育和更新的调节机制不仅是发育生物学的主要目标之一，也是阐明病理过程发展机制的重要步骤。尿路上皮形成和维持的方式在很大程度上是未知的，尿路上皮干细胞的存在是有争议的。本研究旨在确定膀胱尿路上皮的细胞系和分化程序。我们最近证明了p53同源基因p63是尿路上皮基底细胞和中间细胞发育所必需的。此外，通过囊胚互补实验，我们已经证明尿路上皮的伞细胞可以独立于p63阳性的基底细胞和中间细胞而发育和维持。这些结果挑战了目前基底/中间细胞是伞细胞祖细胞的观点，支持了基底/中间细胞和伞细胞代表完全独立细胞系的假设。这个提议的目的是为这个假设是否正确提供一个明确的答案。事实上，尽管p53阳性的基础/中间细胞不是伞细胞形成所必需的，但在其他情况下（如衰老或细胞损伤后）或与其他细胞类型结合时，p53阳性的基础/中间细胞也可能表现出干细胞的能力。在这里，我们建议通过以下方法来验证中心假设：1)确定在衰老或细胞损伤期间尿路上皮保护伞细胞的更新是否需要p53阳性的基础细胞和中间细胞；2)通过遗传谱系追踪确定p53阳性的基础细胞和中间细胞是否产生保护伞细胞。这些研究将澄清膀胱上皮细胞之间的谱系关系，并为尿路上皮干细胞的性质提供重要的见解。

DESCRIPTION (provided by applicant): Unraveling the mechanisms regulating the development and renewal of normal tissues is not only one of the main goals of developmental biology but also an essential step for the elucidation of the mechanisms underlying the development of pathological processes. The way the urothelium is formed and maintained is largely unknown and the existence of urothelial stem cells is controversial. This proposal aims at defining cell lineages and differentiation programs in the bladder urothelium. We have recently demonstrated that the p53-homologue p63 is required for the development of basal and intermediate cells of the urothelium. Additionally, by performing blastocyst complementation experiments we have shown that umbrella cells of the urothelium of can develop and be maintained independently from p63-positive basal and intermediate cells. These results challenge the current view that basal/intermediate cells are the progenitors of umbrella cells and support the hypothesis that basal/intermediate cells and umbrella cells represent entirely independent cell lineages. The goal of this proposal is to provide a definitive answer on whether or not this hypothesis is correct. In fact, although p63-positive basal/intermediate cells are not required for the formation of umbrella cells, it is possible that p63-positive basal/intermediate cells exhibit stem cells capabilities in other circumstances (i.e. during aging or after cell damage) or in conjunction with other cell types. Here we propose to test the central hypothesis by 1) determining if p63-positive basal and intermediate cells are required for the renewal of urothelial umbrella cells during aging or after cell injury 2) determining if p63-positive basal and intermediate cells give rise to umbrella cells by performing genetic lineage tracing. These studies will clarify lineage relationships among bladder epithelial cells and provide important insights into the nature of urothelial stem cells.