The miracle of RNA interference in the modern medical research

RNA interference (RNAi) serves as a powerful tool in regulating specific genes. There are two pathways of RNAi that are triggered by endogenous microRNA (pri-miRNA)  or exogenous double-strand RNA (dsRNA). In the initiation step, pri-miRNA or dsRNA is cleaved into miRNA and small interfering RNA duplex (siRNA), respectively. Subsequently the mi/siRNA is incorporated into the RNA induced silencing complex (RISC) and leading the RISC to complementary RNA molecules. RNAi results in not only the knockdown of gene expression but also degradation of the target gene. To date, RNAi technology is indispensable in modern medical research. The goal of RNAi research is to elucidate the biological effects resulting from silencing a target of interest, gene function, as well as host-pathogen interactions. Moreover, the clinical application of RNAi is employed as a novel RNAi therapy for treatment of several diseases including cancers, viral infection and others. However, RNAi therapy has limitation due to cytotoxicity of the existing siRNA delivery method.