Inhibition of Sox2 Expression in the Adult Neural Stem Cell Niche In Vivo by Monocationic-based siRNA Delivery.

RNA interference (RNAi) is a major tool for basic and applied investigations. However, obtaining RNAi data that have physiological significance requires investigation of regulations and therapeutic strategies in appropriate in vivo settings. To examine in vivo gene regulation and protein function in the adult neural stem cell (NSC) niche, we optimized a new non-viral vector for delivery of siRNA into the subventricular zone (SVZ). This brain region contains the neural stem and progenitor cells populations that express the stem cell marker, SOX2. Temporally and spatially controlled Sox2 knockdown was achieved using the monocationic lipid vector, IC10. siRNA/IC10 complexes were stable over time and smaller (<40 nm) than jetSi complexes (≈400 nm). Immunocytochemistry showed that siRNA/IC10 complexes efficiently target both the progenitor and stem cell populations in the adult SVZ. Injection of the complexes into the lateral brain ventricle resulted in specific knockdown of Sox2 in the SVZ. Furthermore, IC10-mediated transient in vivo knockdown of Sox2-modulated expression of several genes implicated in NSC maintenance. Taken together, these data show that IC10 cationic lipid formulation can efficiently vectorize siRNA in a specific area of the adult mouse brain, achieving spatially and temporally defined loss of function.Molecular Therapy-Nucleic Acids (2013) 2, e89; doi:10.1038/mtna.2013.8; published online 23 April 2013.

Mesomorphic imidazolium salts: new vectors for efficient siRNA transfection.

The preparation of chloride (1(n)) and bromide (2(n)) derivatives of 1-methyl-3-[3,4-bis(alkoxy)benzyl]-4H-imidazolium with n = 6, 12, 16, 18 is described. The two series of salts possess a rich thermotropic mesomorphism, chain-length dependent. Thus, a lamellar smectic A phase, a bicontinuous cubic Ia3d phase, and a columnar hexagonal liquid crystalline mesophase are induced as a function of increasing chain length. The mesomorphic properties were studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction, and with the support of dilatometry and molecular dynamics, models for the various supramolecular arrangements of the salts are proposed. Such cationic amphiphiles were expected to be candidate molecules to design a new delivery reagent for nucleic acid transfection, particularly for short interfering RNA (siRNA). The use of an RNA interference mechanism, by introduction into cells by transfection of chemically synthesized siRNAs, is a powerful method for gene silencing studies. To exploit the potential of these amphilic imidazolium salts, these molecules were formulated with cohelper lipids and tested for their efficacy to deliver active siRNAs. Our results show high transfection efficacy of our formulated compounds and high silencing efficiency with more than 80% inhibition of the targeted gene at 10 nM siRNA concentration. Taken together our results show the potency of amphiphilic imidazolium salts as a new generation of transfection reagents for RNA interference.