title: Characteristics of hepatic stem/progenitor cells in the fetal and adult liver.
abstract: BACKGROUND
  The liver is an essential organ that maintains vital activity through its numerous important functions. It has a unique capability of fully regenerating after injury. Regulating a balance between self-renewal and differentiation of hepatic stem cells that are resources for functional mature liver cells is required for maintenance of tissue homeostasis.
  
  
  METHODS
  This review describes the characteristics of hepatic stem/progenitor cells and the regulatory mechanism of their self-renewal and differentiation capacity.
  
  
  RESULTS
  In liver organogenesis, undifferentiated hepatic stem/progenitor cells expand their pool by repeated self-renewal in the early stage of liver development and then differentiate into two different types of cell lineage, namely hepatocytes and cholangiocytes. Liver development is regulated by expression of stem cell transcription factors in a complex multistep process. Recent studies suggest that stem cells are maintained by integrative regulation of gene expression patterns related to self-renewal and differentiation by epigenetic mechanisms such as histone modification and DNA methylation.
  
  
  CONCLUSIONS
  Analysis of the proper regulatory mechanism of hepatic stem/progenitor cells is important for regenerative medicine that utilizes hepatic stem cells and for preventing liver cancer through clarification of the carcinogenetic mechanism involved in stem cell system failure.
authors.affiliation: Department of Regenerative Medicine, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Kanazawa-ku, Yokohama, Kanagawa, 236-0004, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koike
authors.forename: Hideki
authors.initials: H
authors.lastname: Taniguchi
mesh_terms: D002454:Cell Differentiation; D019070:Cell Lineage / Q000502:physiology*; D002478:Cells, Cultured; D005333:Fetus / Q000166:cytology*; D022781:Hepatocytes / Q000166:cytology; D006801:Humans; D008099:Liver / Q000196:embryology* / Q000648:ultrastructure*; D017348:Microscopy, Electron, Scanning Transmission; D013234:Stem Cells / Q000648:ultrastructure*