Self-assembled Micelle Interfering RNA for Effective and Safe Targeting of Dysregulated Genes in Pulmonary Fibrosis.

Abstract SiRNA silencing approach has long been used as a method to regulate the expression of specific target gene in vitro and in vivo. However, the effectiveness of delivery and the nonspecific immune stimulatory function of siRNA are the limiting factors for therapeutic application of siRNAs. To overcome these limitations, we developed self-assembled micelle inhibitory RNA (SAMiRNA) nanoparticles made of individually bi-conjugated siRNAs with hydrophilic polymer and lipid on their ends and characterized their stability, immune stimulatory function and in vivo silencing efficacy. SAMiRNAs form very stable nanoparticles with no significant degradation in the size distribution and polydispersity index over 1 year. Overnight incubation of SAMiRNAs (3μM) on murine PBMCs did not cause any significant elaboration of innate immune cytokines such as TNF-α, IL-12 or IL-6, while unmodified siRNAs or liposome or liposome complex significantly stimulated the expression of these cytokines. Lastly, in vivo silencing efficacy of SAMiRNAs was evaluated by targeting amphiregulin (AR) and connective tissue growth factor (CTGF) in bleomycin or TGF-β transgenic (Tg) animal models of pulmonary fibrosis. Only two or three times of intratracheal (i.t.) or intravenous (i.v.) delivery of AR or CTGF SAMiRNAs significantly reduced the bleomycin- or TGF-β -stimulated collagen accumulation in the lung and substantially restored the lung function of TGF-β Tg mice. These studies demonstrated that SAMiRNA nanoparticles as a less-toxic, stable siRNA silencing platform for efficient in vivo targeting of genes implicated in the pathogenesis of pulmonary fibrosis.