Strategies to antagonize miRNA functions in vitro and in vivo.

miRNAs are a class of short noncoding RNAs that regulate gene expression post-transcriptionally. Diseased tissues have altered miRNA expression patterns, which could provide potential therapeutic targets. Introducing chemically engineered antisense oligonucleotides to cells can silence upregulated miRNAs. Successful miRNA inhibition can be assessed directly by quantitative reverse transcription PCR or northern blot, or indirectly by measuring de-repression of target genes or using reporter assays. In this review, we will discuss the design of chemically modified antisense oligonucleotides (anti-miRNA), in vivo delivery of anti-miRNA to inhibit disease-related miRNAs and the development of nanoparticle-based anti-miRNA delivery systems. In particular, we will focus on interfering nanoparticles that we designed for in vivo delivery of chemically modified anti-miRNA-122 in mice.