Small interfering RNA delivery into the liver by cationic cholesterol derivative-based liposomes

<p><i>Purpose</i>: Previously, we reported that the cationic liposomes composed of a cationic cholesterol derivative, cholesteryl (2-((2-hydroxyethyl)amino)ethyl)carbamate (OH-C-Chol) and 1,2-dioleoyl-<i>sn</i>-glycero-3-phosphoethanolamine (DOPE) (termed LP-C), could deliver small interfering RNAs (siRNAs) with high transfection efficiency into tumor cells. In this study, to develop a liposomal vector for siRNA delivery <i>in vivo</i>, we prepared the poly(ethyleneglycol) (PEG)-modified cationic liposomes (LP-C-PEG) and evaluated their transfection efficiency <i>in vitro</i> and <i>in vivo</i>.</p> <p><i>Materials and methods</i>: We prepared LP-C-PEG/siRNA complexes (LP-C-PEG lipoplexes) formed in water or 50 mM NaCl solution, and evaluated their siRNA biodistribution and gene silencing effect in mice after intravenous injection.</p> <p><i>Results</i>: LP-C-PEG lipoplexes strongly exhibited <i>in vitro</i> gene silencing effects in human breast tumor MCF-7 cells as well as LP-C lipoplexes. In particular, formation of LP-C and LP-C-PEG lipoplexes in the NaCl solution increased the cellular association. When LP-C-PEG lipoplexes with Cy5.5-labeled siRNA formed in water or NaCl solution were injected into mice, accumulation of the siRNA was observed in the liver. Furthermore, injection of LP-C-PEG lipoplexes with ApoB siRNA could suppress ApoB mRNA levels in the liver and reduce very-low-density lipoprotein/low-density lipoprotein levels in serum compared with that after Cont siRNA transfection, although the presence of NaCl solution in forming the lipoplexes did not affect gene silencing effects <i>in vivo</i>.</p> <p><i>Conclusions</i>: LP-C-PEG may have potential as a gene vector for siRNA delivery to the liver.</p