title: Human Enteroids as a Model of Upper Small Intestinal Ion Transport Physiology and Pathophysiology.
abstract: OBJECTIVE
  Human intestinal crypt-derived enteroids are a model of intestinal ion transport that require validation by comparison with cell culture and animal models. We used human small intestinal enteroids to study neutral Na(+) absorption and stimulated fluid and anion secretion under basal and regulated conditions in undifferentiated and differentiated cultures to show their functional relevance to ion transport physiology and pathophysiology.
  
  
  METHODS
  Human intestinal tissue specimens were obtained from an endoscopic biopsy or surgical resections performed at Johns Hopkins Hospital. Crypts were isolated, enteroids were propagated in culture, induced to undergo differentiation, and transduced with lentiviral vectors. Crypt markers, surface cell enzymes, and membrane ion transporters were characterized using quantitative reverse-transcription polymerase chain reaction, immunoblot, or immunofluorescence analyses. We used multiphoton and time-lapse confocal microscopy to monitor intracellular pH and luminal dilatation in enteroids under basal and regulated conditions.
  
  
  RESULTS
  Enteroids differentiated upon withdrawal of WNT3A, yielding decreased crypt markers and increased villus-like characteristics. Na(+)/H(+) exchanger 3 activity was similar in undifferentiated and differentiated enteroids, and was affected by known inhibitors, second messengers, and bacterial enterotoxins. Forskolin-induced swelling was completely dependent on cystic fibrosis transmembrane conductance regulator and partially dependent on Na(+)/H(+) exchanger 3 and Na(+)/K(+)/2Cl(-) cotransporter 1 inhibition in undifferentiated and differentiated enteroids. Increases in cyclic adenosine monophosphate with forskolin caused enteroid intracellular acidification in HCO3(-)-free buffer. Cyclic adenosine monophosphate-induced enteroid intracellular pH acidification as part of duodenal HCO3(-) secretion appears to require cystic fibrosis transmembrane conductance regulator and electrogenic Na(+)/HCO3(-) cotransporter 1.
  
  
  CONCLUSIONS
  Undifferentiated or crypt-like, and differentiated or villus-like, human enteroids represent distinct points along the crypt-villus axis; they can be used to characterize electrolyte transport processes along the vertical axis of the small intestine. The duodenal enteroid model showed that electrogenic Na(+)/HCO3(-) cotransporter 1 might be a target in the intestinal mucosa for treatment of secretory diarrheas.
authors.affiliation: Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Foulke-Abel
authors.affiliation: Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Julie
authors.initials: J
authors.lastname: In
authors.affiliation: Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Jianyi
authors.initials: J
authors.lastname: Yin
authors.affiliation: Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Zachos
authors.affiliation: Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Olga
authors.initials: O
authors.lastname: Kovbasnjuk
authors.affiliation: Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Estes
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Hugo
authors.initials: H
authors.lastname: de Jonge
authors.affiliation: Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: mdonowit@jhmi.edu.
authors.forename: Mark
authors.initials: M
authors.lastname: Donowitz
mesh_terms: D002454:Cell Differentiation; D005786:Gene Expression Regulation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007419:Intestinal Secretions / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D017136:Ion Transport; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D036641:Microscopy, Fluorescence, Multiphoton; D018715:Microscopy, Video; D012964:Sodium / Q000378:metabolism*; D059008:Time-Lapse Imaging; D046509:Tissue Culture Techniques; D014161:Transduction, Genetic; D014162:Transfection
chemical_list: D026901:Membrane Transport Proteins; D012964:Sodium
keywords: Intestinal Organoids; NHE3 Activity; Na(+) Absorption; Stimulated Secretion