| Abstract
| - A hepatocyte-directed vector has been developed; it includes several keyfeatures thought to favor invivo gene delivery to the liver: electrostatically neutralparticles which avoid nonspecific binding toother cells, to the extracellular matrix, and to complement proteins;asialoglycoprotein receptor-mediated endocytosis which may address the complexes to the perinuclearregion; and polyethylenimine(PEI)-mediated endosome buffering and swelling as an escape mechanismto the cytoplasm. Thissystem is based on a 5% galactose-bearing polyethylenimine (PEI−gal)polymer which is condensedwith plasmid DNA to neutrality. Murine (BNL CL.2) and human(HepG2) hepatocyte-derived celllines were transfected 104−105-fold moreefficiently than murine fibroblasts (3T3), whethertransfectionwas assessed globally (luciferase expression from the cell extract) orfollowing histochemical staining(β-galactosidase). Under these conditions, over 50% of thehepatocytes were selectively transfectedin the presence of 10% serum. Transfection was suppressed byremoval of the targeting galactoseresidues, by their replacement with glucose, or by the addition ofexcess asialofetuin. Thus, resultsfrom comparative and competitive experiments indicate theasialoglycoprotein receptor is involved intransfection of hepatocytes with neutral PEI−gal/DNAcomplexes.
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