title: In vivo gene silencing following non-invasive siRNA delivery into the skin using a novel topical formulation.
abstract: Therapeutics based on short interfering RNAs (siRNAs), which act by inhibiting the expression of target transcripts, represent a novel class of potent and highly specific next-generation treatments for human skin diseases. Unfortunately, the intrinsic barrier properties of the skin combined with the large size and negative charge of siRNAs make epidermal delivery of these macromolecules quite challenging. To help evaluate the in vivo activity of these therapeutics and refine delivery strategies we generated an innovative reporter mouse model that predominantly expresses firefly luciferase (luc2p) in the paw epidermis--the region of murine epidermis that most closely models the tissue architecture of human skin. Combining this animal model with state-of-the-art live animal imaging techniques, we have developed a real-time in vivo analysis work-flow that has allowed us to compare and contrast the efficacies of a wide range nucleic acid-based gene silencing reagents in the skin of live animals. While inhibition was achieved with all of the reagents tested, only the commercially available "self-delivery" modified Accell-siRNAs (Dharmacon) produced potent and sustained in vivo gene silencing. Together, these findings highlight just how informative reliable reporter mouse models can be when assessing novel therapeutics in vivo. Using this work-flow, we developed a novel clinically-relevant topical formulation that facilitates non-invasive epidermal delivery of unmodified and "self-delivery" siRNAs. Remarkably, a sustained >40% luc2p inhibition was observed after two 1-hour treatments with Accell-siRNAs in our topical formulation. Importantly, our ability to successfully deliver siRNA molecules topically brings these novel RNAi-based therapeutics one-step closer to clinical use.
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Vikas
authors.initials: V
authors.lastname: Hegde
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Robyn P
authors.initials: RP
authors.lastname: Hickerson
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Sitheswaran
authors.initials: S
authors.lastname: Nainamalai
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK; Carnegie Physics Laboratory, University of Dundee, Dundee DD1 4HN, Scotland, UK.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Campbell
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Frances J D
authors.initials: FJ
authors.lastname: Smith
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK. Electronic address: w.h.i.mclean@dundee.ac.uk.
authors.forename: W H Irwin
authors.initials: WH
authors.lastname: McLean
authors.affiliation: Centre for Dermatology and Genetic Medicine, Division of Molecular Medicine, University of Dundee, Dundee DD1 5EH, Scotland, UK. Electronic address: d.lesliepedrioli@dundee.ac.uk.
authors.forename: Deena M Leslie
authors.initials: DM
authors.lastname: Pedrioli
mesh_terms: D000287:Administration, Topical; D000818:Animals; D002626:Chemistry, Pharmaceutical; D016503:Drug Delivery Systems; D004817:Epidermis / Q000187:drug effects; D000091344:Filaggrin Proteins; D020868:Gene Silencing; D017930:Genes, Reporter / Q000187:drug effects; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D007271:Injections, Intradermal; D007381:Intermediate Filament Proteins / Q000008:administration & dosage / Q000235:genetics; D051379:Mice; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D034741:RNA, Small Interfering
keywords: Filaggrin; Luciferase reporter mouse model; Propylene glycol (PubChem CID: 1030); RNAi-based therapeutics; Topical formulation; Transepidermal siRNA delivery