Adenoassociated virus-mediated transfer of a functional water channel into salivary epithelial cells in vitro and in vivo

Aquaporin 1 (AQP1) is the archetypal member of a family of integral membrane proteins that function as water channels. Previously we have shown that this protein can be expressed transiently from a recombinant adenovirus (AdhAQP1) in vitro in different epithelial cell lines, and in vivo in rat submandibular glands. In the present study we have constructed a recombinant adenoassociated virus (rAAV) containing the human aquaporin 1 gene (rAA VhAQP1). rAA VhAQP1 was produced at relatively high titers. ≃ 10¹¹-10¹² particles/ml and ≃ 10⁸-10⁹ transducing units/ml. We show that the rAA VhAQP1 can transduce in vitro four epithelial cell lines of different origins, at a level sufficient to detect the recombinant hAQP1 protein by either Western blot or confocal microscopic analysis. The recombinant hAQP1 was correctly targeted to the plasma membranes in all cell lines. Function of the recombinant hAQP1 was measured as fluid flow, in response to an osmotic gradient, across a monolayer of transduced epithelial cells. The data show that even at a low level of transduction, typically ≃ 10% of the cells in the monolayer, transepithelial fluid movement is enhanced about threefold above basal levels. In addition, we report that rAA VhAQP1 can transduce epithelial cells in the salivary glands and liver of mice in vivo. These results suggest that rAAVs may be useful gene transfer vectors to direct the production of functional transgenes in salivary epithelial cell types.