Targeted gene delivery to hepatoma cells using galactosylated liposome-polycation-DNA complexes (LPD)

A major goal for gene therapy is to obtain targeted vectors that transfer genes efficiently to specific cell types. The liver possesses a variety of characteristics that make this organ very attractive for gene therapy. In the present study, four cholesterylated thiogalactosides 1a ～ d with different spacer length were synthesized to formulate novel lipid-polycation-DNA (LPD) complexes, which were composed of galactosylated cationic liposomes, protamine sulfate and plasmid DNA. The galactosylated LPD1c significantly improved the levels of gene expression in cultured hepatoma cells HepG2 and SMMC-7721, while LPD1a and LPD1b did not significantly improve the levels compared with non-galactosylated LPD. Meanwhile, increased transfection activity was not observed in mouse fibroblasts L929 for galactosylated LPDs. Cytotoxicity of galactosylated LPDs assay showed they had no obvious toxicities to L929 cells and HepG2 cells. In summary, the length of the spacer between the anchor and galactose residues was important for the recognition of asialoglycoprotein receptor. The LPD1c described here, combining the condensing effect of protamine and the targeting capability of cholesterylated thiogalactosides, are potentially useful gene carriers to liver parenchymal cells.     

己二醇桥联胆甾半乳糖苷的合成

目的合成具有脂水两性的肝靶向脂质体配体胆甾半乳糖苷衍生物。方法将胆固醇3位羟基与己二醇的双甲磺酸酯成醚后再碘代,随后与2,3,4,6-四-O-乙酰基-1-硫代-β-D-吡喃半乳糖成硫醚得到糖苷,经甲醇钠处理脱掉乙酰基得目标物。结果合成了1个胆甾半乳糖苷衍生物。结论合成衍生物及中间体的结构经1HNMR、IR、MS确证。     

Novel synthetic LPDs consisting of different cholesterol derivatives for gene transfer into hepatocytes

In the present study, LPDs composing of a series of novel synthetic cholesterylated derivatives bearing a cluster of galactose residues and different spacer lengths were prepared for performing target gene delivery to hepatocytes and their physiochemical properties as well as gene transfer efficiency were investigated. In agreement with the “clustering effect” known to occur with more complex oligomeric structures, the addition of galactose residues under optimized spatial arrangement condition invariably increased the transfect efficiency into hepatoma cells, which can be owed to the sufficient binding of galactose ligands to the ASGPR on hepatocytes. However, the gene transfer ability to hepatocytes was not always improved with extended spacer arms, suggesting a spatial binding sites arrangement of the receptor. Moreover, our research has established galactosylated LPDs, specifically, LPDIIb, LPDIIIc, and LPDIVe as potential vectors to deliver special genes into hepatocytes with low toxicity, combining the condensing effect of protamine and the targeting capability of cholesterylated thiogalactosides.