Partial Correction of the Urinary Concentrating Defect in Aquaporin-1 Null Mice by Adenovirus-Mediated Gene Delivery

The feasibility of water channel gene delivery to kidney tubules and microvessels was evaluated by delivery of an adenovirus encoding aquaporin 1 (AQP1-Ad5) to transgenic AQP1 null mice. In wild-type mice, AQP1 is expressed in kidney proximal tubule, thin descending limb of Henle, and descending vasa recta, where urine osmolality (U _osm) increases from 1000-1500 mOsm (before) to 2500-3500 mOsm after 36 hr of water deprivation. U _osm in AQP1 null mice remains nearly fixed at 650-750 mOsm. AQP1-Ad5 (with a CMV promoter) was generated and purified. Infection of CHO cells gave strong uniform AQP1 expression with plasma membrane localization and eightfold increased water permeability over noninfected cells. AQP1-Ad5 was delivered to 20 to 25-g AQP1 null mice by tail vein infusion(0-10¹⁰ PFU). At 3-7 days, AQP1 protein expression was strongest in liver (∼20 mug of AQP1 protein per liver) and next strongest in kidney, with expression in proximal tubule apical and basolateral membranes, and renal microvessels. Functional analysis showed increased water permeability in apical membrane vesicles from proximal tubule. AQP1 expression was not detected in glomerulus, limb of Henle, or collecting duct. In water-deprived null mice receiving 5 X 10⁹ PFU of AQP1-Ad5, U _osm increased by up to 510 mOsm (mean increase, 225 ± 24 mOsm; n= 33 mice). Whereas the control null mice became lethargic and lost 34.2 ± 0.6% body weight, the virus-treated mice remained relatively active and lost 32.3 ± 0.7% body weight. Viral DNA and AQP1 transcript were detected in kidney and liver of null mice up to 17 weeks after virus infusion; partial correction of the urinary concentrating defect persisted for 3-5 weeks. These results demonstrate partial functional correction of a urinary concentrating defect by adenoviral delivery of the AQP1 gene.