title: Aquaporin-1 expression and conventional aqueous outflow in human eyes.
abstract: Aquaporin channels facilitate the enhanced permeability of secretory and absorptive tissues to water. In the conventional drainage tract, aquaporin-1 is expressed but its contribution to outflow facility is unknown. The purpose of the present study was to determine the effect of elevated aquaporin-1 expression by cells of the human conventional drainage pathway on outflow facility. Using 13 pairs of human anterior segments in organ culture, we modified aquaporin-1 protein expression in outflow cells using adenovirus encoding human aquaporin-1. Contralateral anterior segments served as controls and were transduced with adenovirus encoding beta-galactosidase. By confocal immunofluorescence microscopy, we observed that inner trabecular meshwork cells from anterior segments exposed to adenovirus (via injection into the inlet tubing during perfusion) had increased aquaporin-1 protein expression compared to endogenous levels. In contrast, elevation of aquaporin-1 protein in outer meshwork cells (juxtacanalicular region) and Schlemm's canal required transduction of adenovirus into anterior segments using retroperfusion via episcleral veins. Regardless of exposure route, outflow facility of experimental segments was not different than control. Specifically, overexpression of aquaporin-1 in the inner meshwork resulted in an average facility change of -2.0+/-9.2%, while overexpression of aquaporin-1 in the resistance-generating region changed outflow facility by -3.2+/-11.2%. Taken together, these results indicate that a transcellular pathway, mediated by aquaporin-1, does not contribute significantly to bulk outflow through the conventional aqueous outflow tract of human eyes.
authors.affiliation: Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, AZ 85711, USA. dstamer@eyes.arizona.edu
authors.forename: W Daniel
authors.initials: WD
authors.lastname: Stamer
authors.forename: Darren W H
authors.initials: DW
authors.lastname: Chan
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Conley
authors.forename: Serena
authors.initials: S
authors.lastname: Coons
authors.forename: C Ross
authors.initials: CR
authors.lastname: Ethier
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000368:Aged; D000369:Aged, 80 and over; D000869:Anterior Eye Segment / Q000378:metabolism; D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism*; D001082:Aqueous Humor / Q000378:metabolism*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005822:Genetic Vectors; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods; D008875:Middle Aged; D009924:Organ Culture Techniques; D014129:Trabecular Meshwork / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D005136:Eye Proteins; D051398:Aquaporin 1