Am. J. Respir. Cell Mol. Biol.,
Volume 24, Number 3, March, 2001 224-234
Expression and Localization of Epithelial Aquaporins in the
Adult Human Lung
Silvia M.
Kreda,*
Michael C.
Gynn,*
David A.
Fenstermacher,
Richard C.
Boucher,
and
Sherif E.
Gabriel
Cystic Fibrosis/Pulmonary Research and Clinical Treatment Center, University of North Carolina at Chapel Hill,
Chapel Hill, North Carolina
Aquaporins (AQPs) facilitate water transport across epithelia
and play an important role in normal physiology and disease in the human airways. We used in situ hybridization and immunofluorescence to determine the expression and cellular
localization of AQPs 5, 4, and 3 in human airway sections. In
nose and bronchial epithelia, AQP5 is expressed at the apical
membrane of columnar cells of the superficial epithelium and
submucosal gland acinar cells. AQP4 was detected in basolateral membranes in ciliated ducts and by in situ in gland acinar
cells. AQP3 is present on basal cells of both superficial epithelium and gland acinus. In these regions AQPs 5, 4, and 3 are appropriately situated to permit transepithelial water permeability. In the small airways (proximal and terminal bronchioles)
AQP3 distribution shifts from basal cell to surface expression
(i.e., localized to the apical membrane of proximal and terminal bronchioles) and is the only AQP identified in this region
of the human lung. The alveolar epithelium has all three AQPs
represented, with AQP5 and AQP4 localized to type I pneumocytes and AQP3 to type II cells. This study describes an intricate network of AQP expression that mediates water transport across the human airway epithelium.
*
These authors contributed equally to this manuscript.
Abbreviations: airway surface liquid, ASL; aquaporin, AQP; complementary DNA, cDNA; hematoxylin and eosin, H&E; immunofluorescence, IF;
immunoglobulin, Ig; in situ hybridization, ISH; messenger RNA, mRNA;
water permeability, Pf; surfactant protein, SP.
