title: Expression and Localization of Aquaporin Water Channels in Human Middle Ear Epithelium.
abstract: BACKGROUND
  Although aquaporins (AQPs) are known to play critical roles as the basis for water and solute transport in water homeostasis, AQPs in normal human middle ear epithelium (NHMEE) has not previously been investigated.
  
  
  OBJECTIVE
  To investigate the expressions of AQP water channels in NHMEE in situ, in proliferating epithelial cell cultures in vitro.
  
  
  METHODS
  AQP 0-12 expressions by cultured NHMEE cells in situ were assessed by reverse transcriptase-polymerase chain reaction. Normal middle ear epithelial tissue was harvested and investigated for expressions of AQPs (1, 3, 4, and 5) by immunohistochemistry. Expression screening was also carried out on the differentiated NHMEE cells.
  
  
  RESULTS
  Transcripts for AQP 1, 2, 3, 4, 5, 6, 8, 10, and 11 were expressed consistently in cultured NHMEE cells; however, AQP 0, 7, 9, and 12 subtypes were not expressed. Immunochemistry confirmed the expressions of AQP 1, 3, and 5 at the protein level. AQP 1 was localized at capillary endothelial cells and fibroblasts in lamina propria mucosae; AQP 3 was present solely at the basolateral membrane of ciliated cells, whereas AQP 5 was on the apical surface of ciliated cells. AQP 3 and 5 were intensely expressed in both cultured NHMEE cells in situ and NHMEE tissue in vitro.
  
  
  CONCLUSIONS
  This is the first study to demonstrate that AQPs are expressed by human middle ear epithelium in situ and in vitro, suggesting a potential role in otitis media with effusion. Our study suggests that the presence of AQP 1, 3, and 5 in the middle ear cavity may be to have an important role for water transportation.
authors.affiliation: *Department of Otorhinolaryngology, Yonsei University College of Medicine, Wonju; and the †Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Young Joon
authors.initials: YJ
authors.lastname: Seo
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Choi
mesh_terms: D020346:Aquaporins / Q000096:biosynthesis* / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D002923:Cilia / Q000378:metabolism; D004432:Ear, Middle / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009092:Mucous Membrane / Q000378:metabolism; D016133:Polymerase Chain Reaction; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D014867:Water