title: Mechanisms and optimization of in vivo delivery of lipophilic siRNAs.
abstract: Cholesterol-conjugated siRNAs can silence gene expression in vivo. Here we synthesize a variety of lipophilic siRNAs and use them to elucidate the requirements for siRNA delivery in vivo. We show that conjugation to bile acids and long-chain fatty acids, in addition to cholesterol, mediates siRNA uptake into cells and gene silencing in vivo. Efficient and selective uptake of these siRNA conjugates depends on interactions with lipoprotein particles, lipoprotein receptors and transmembrane proteins. High-density lipoprotein (HDL) directs siRNA delivery into liver, gut, kidney and steroidogenic organs, whereas low-density lipoprotein (LDL) targets siRNA primarily to the liver. LDL-receptor expression is essential for siRNA delivery by LDL particles, and SR-BI receptor expression is required for uptake of HDL-bound siRNAs. Cellular uptake also requires the mammalian homolog of the Caenorhabditis elegans transmembrane protein Sid1. Our results demonstrate that conjugation to lipophilic molecules enables effective siRNA uptake through a common mechanism that can be exploited to optimize therapeutic siRNA delivery.
authors.affiliation: Institute of Molecular Systems Biology, Swiss Federal Institute of Technology, ETH Zürich, HPT E73.
authors.forename: Christian
authors.initials: C
authors.lastname: Wolfrum
authors.forename: Shuanping
authors.initials: S
authors.lastname: Shi
authors.forename: K Narayanannair
authors.initials: KN
authors.lastname: Jayaprakash
authors.forename: Muthusamy
authors.initials: M
authors.lastname: Jayaraman
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Pandey
authors.forename: Kallanthottathil G
authors.initials: KG
authors.lastname: Rajeev
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nakayama
authors.forename: Klaus
authors.initials: K
authors.lastname: Charrise
authors.forename: Esther M
authors.initials: EM
authors.lastname: Ndungo
authors.forename: Tracy
authors.initials: T
authors.lastname: Zimmermann
authors.forename: Victor
authors.initials: V
authors.lastname: Koteliansky
authors.forename: Muthiah
authors.initials: M
authors.lastname: Manoharan
authors.forename: Markus
authors.initials: M
authors.lastname: Stoffel
mesh_terms: D000818:Animals; D001055:Apolipoproteins B / Q000235:genetics / Q000378:metabolism; D002784:Cholesterol; D006224:Cricetinae; D018014:Gene Transfer Techniques; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL / Q000235:genetics / Q000378:metabolism; D008647:Mesocricetus; D051379:Mice; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics*; D018110:Receptors, Lipoprotein / Q000378:metabolism
chemical_list: D001055:Apolipoproteins B; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D034741:RNA, Small Interfering; D018110:Receptors, Lipoprotein; D002784:Cholesterol