Glomerular filtration is required for transfection of proximal tubular cells in the rat kidney following injection of DNA complexes into the renal artery

Gene transfer to the kidney can be achieved with various DNA vectors, resul ting in transgene expression in glomerular or tubular districts. Controllin g transgene destination is desirable for targeting defined renal cells for specific therapeutic purposes. We previously showed that injection of polyp lexes into the rat renal artery resulted in transfection of proximal tubula r cells. To investigate whether this process involves glomerular filtration of the DNA-containing particles, fluorescent polyethylenimine polyplexes w ere prepared, containing fluoresceinated poly-L-lysine. This allowed visual ization of the route of the particles into the kidney. Our polyplexes were filtered through the glomerulus, since fluorescent proximal tubuli were obs erved Conversely, fluorescent lipopolyplexes containing the cationic lipid DOTAP were never observed in tubular cells. Size measurements by laser ligh t scattering showed that the mean diameter of polyplexes (93 nm) was smalle r than that of lipopolyplexes (160 nm). The size of the transfecting partic les is therefore a key parameter in this process, as expected by the constr aints imposed by the glomerular filtration barrier. This information is rel evant, in view of modulating the physico-chemical properties of DNA complex es for optimal transgene expression in tubular cells.