Program Director/Principal Investigator (Last, First, Middle): Mendelsohn, Cathy Lee Project Summary The urothelium is an epithelial barrier that prevents exchange of water and toxic substances between the blood and urinary tract. It is composed of basal cells, Intermediate cells and a luminal layer of superficial cells. Superficial cells are specialized for synthesis and transport of uroplakins, a family of proteins that assemble into the crystalline apical plaque that is the functional urothelial barrier. Superficial cells have a number of interesting features; they are enormous, generally binucleated and are polyploid. The urothelium is one of the most quiescent epithelia in the body, but quickly regenerates in response to acute damage, for example from urinary tract infection. Chronic injury however, from repeated exposure to toxins such as cyclophosphamide, can lead to barrier compromise, inflammation and disease such as bladder pain syndrome, a life altering condition for which there is no cure at present. These proposed studies build on previous findings from our lab that identify novel urothelial progenitors that are important for development and regeneration. In the present application, we will use lineage analysis and an organ culture together with live imaging to visualize the behavior of adult wild type and mutant urothelial progenitors. We will pursue preliminary studies suggesting that Basal cells, which are unipotent during acute injury, acquire the potential to produce Intermediate and Superficial cell daughters after chronic injury. We identify Pparg, a nuclear receptor best known for its role in adipogenesis, as a potential target of Retinoids, and we show that Pparg is critical for formation and regeneration of Superficial cells, and also regulates basal cell homeostasis, preventing squamous differentiation. Besides its critical role in human health, the urothelium is a also source of cells that give rise to different types of bladder cancers. Identification of urothelial progenitors and the signaling pathways that control them will be important for developing therapeutic strategies for regeneration and repair, and for understanding how urothelial differentiation can go wrong.

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Mendelsohn, Cathy Lee Project Narrative In the present application we will examine the roles of RA, the active vitamin A metabolite and Pparg, a nuclear receptor in urothelial formation, and regeneration. We find that these signaling pathways are critical for formation and regeneration of the urothelium and also for suppressing squamous differentiation. Identification of signaling pathways that control urothelial differentiation will be important step in understanding how urothelial differentiation can go wrong.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Kidney Molecular Biology and Genitourinary Organ Development (KMBD)
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Hoshizaki, Deborah K
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Columbia University (N.Y.)
Schools of Medicine
New York
United States
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Wang, Jia; Batourina, Ekatherina; Schneider, Kerry et al. (2018) Polyploid Superficial Cells that Maintain the Urothelial Barrier Are Produced via Incomplete Cytokinesis and Endoreplication. Cell Rep 25:464-477.e4
Joseph, Diya B; Chandrashekar, Anoop S; Abler, Lisa L et al. (2018) In vivo replacement of damaged bladder urothelium by Wolffian duct epithelial cells. Proc Natl Acad Sci U S A 115:8394-8399
Georgas, Kylie M; Armstrong, Jane; Keast, Janet R et al. (2015) An illustrated anatomical ontology of the developing mouse lower urogenital tract. Development 142:1893-908
Yamany, Tammer; Van Batavia, Jason; Mendelsohn, Cathy (2014) Formation and regeneration of the urothelium. Curr Opin Organ Transplant 19:323-30
Gandhi, Devangini; Molotkov, Andrei; Batourina, Ekatherina et al. (2013) Retinoid signaling in progenitors controls specification and regeneration of the urothelium. Dev Cell 26:469-482