title: Formation and regeneration of the urothelium.
abstract: OBJECTIVE
  This review addresses significant changes in our understanding of urothelial development and regeneration. Understanding urothelial differentiation will be important in the push to find new methods of bladder reconstruction and augmentation, as well as identification of bladder cancer stem cells.
  
  
  RESULTS
  This review will cover recent findings including the identification of novel progenitor cells in the embryo and adult urothelium, function of the urothelium, and regeneration of the urothelium. Using Cre-lox recombination with cell-type-specific Cre lines, lineage studies from our laboratory have revealed novel urothelial cell types and progenitors that are critical for formation and regeneration of the urothelium. Interestingly, our studies indicate that Keratin-5-expressing basal cells, which have previously been proposed to be urothelial stem cells, are a self-renewing unipotent population, whereas P-cells, a novel urothelial cell type, are progenitors in the embryo, and intermediate cells serve as a progenitor pool in the adult.
  
  
  CONCLUSIONS
  These findings could have important implications for our understanding of cancer tumorigenesis and could move the fields of regeneration and reconstruction forward.
authors.affiliation: aDepartment of Urology bDepartment of Genetics and Development cDepartment of Pathology, Columbia University, New York, New York, USA.
authors.forename: Tammer
authors.initials: T
authors.lastname: Yamany
authors.forename: Jason
authors.initials: J
authors.lastname: Van Batavia
authors.forename: Cathy
authors.initials: C
authors.lastname: Mendelsohn
mesh_terms: D053687:Adult Stem Cells / Q000166:cytology; D000818:Animals; D002454:Cell Differentiation; D053595:Embryonic Stem Cells / Q000166:cytology; D004847:Epithelial Cells / Q000166:cytology; D006801:Humans; D014411:Neoplastic Stem Cells / Q000473:pathology; D012038:Regeneration; D001749:Urinary Bladder Neoplasms / Q000473:pathology; D019459:Urothelium / Q000502:physiology*