IN-VITRO GENE DELIVERY TO HEPATOCYTES WITH GALACTOSYLATED POLYETHYLENIMINE

A hepatocyte-directed vector has been developed; it includes several k ey featured thought to favor in vivo gene delivery to the liver: elect rostatically neutral particles which avoid nonspecific binding to othe r cells, to the extracellular matrix, and to complement proteins; asia loglycoprotein receptor-mediated endocytosis which may address the com plexes to the perinuclear region; and polyethylenimine (PEI)-mediated endosome buffering and swelling as an escape mechanism to the cytoplas m. This system is based on a 5% galactose-bearing polyethylenimine (PE I-gal) polymer which is condensed with plasmid DNA to neutrality. Muri ne (BNL CL.2) and human (HepG2) hepatocyte-derived cell lines were tra nsfected 10(4)-10(5)-fold more efficiently than murine fibroblasts (3T 3), whether transfection was assessed globally (luciferase expression from the cell extract) or following histochemical staining (beta-galac tosidase). Under these conditions, over 50% of the hepatocytes were se lectively transfected in the presence of 10% serum. Transfection was s uppressed by removal of the targeting galactose residues, by their rep lacement with glucose, or by the addition of excess asialofetuin. Thus , results from comparative and competitive experiments indicate the as ialoglycoprotein receptor is involved in transfection of hepatocytes w ith neutral PEI-gal/DNA complexes.