The ultimate goal of this proposal is to develop gene therapy for the treatment of hereditary kidney diseases. The carbonic anhydrase (CA) II deficient mouse is an ideal model for kidney-specific gene therapy since it manifests renal tubular acidosis and effects of gene therapy can be easily monitored. CA II is an enzyme present in cells of the kidney and other organs such as the brain and bones, and is important for acid-base homeostasis at both cellular and whole body levels. The investigators have developed a novel approach by infusing the CA II gene, driven by a viral promoter, into the urinary space of the kidney of the CA II deficient mice using liposomes as carriers, and shown a transient (3 week) correction of renal tubular acidosis. During this grant period, new strategies will be tested to improve the efficacy and duration of gene expression using this gene therapy model. Specifically, the goals will be: 1) to add polycations, polymers of positive-charged organic compounds such as basic amino acids, to the liposome delivery system in order to enhance the transfection efficiency in vivo. These polycations may serve as signals for the therapeutic gene to be delivered to the nucleus; 2) to replace the viral promoter of the therapeutic gene with the CA II promoter in order to produce a cell-specific, regulatable, and long-term gene expression in mice; 3) to evaluate the safety of the liposome/polycation-mediated gene therapy in mice; and 4) to determine whether gene therapy in CA II deficient mice will convert the phenotypical changes associated with CA II deficiency, i.e., up-regulation of CA IV, and depletion of intercalated cells, which are responsible for acid secretion in the kidney. It is hoped that results obtained from the proposed study will lead to an optimum gene therapy suitable for future clinical trials on a broad range of renal diseases in humans.
