An emerging new category of therapeutic agents based on ribonucleic acid has emerged and shown very
promising in vitro, animal and pre-clinical results, known as small interfering RNAs (siRNAs), microRNAs mimics
(miRNA mimics) and their derivates. siRNAs are small RNA molecules that promote potent and specific silencing of
mutant, exogenous or aberrant genes through a mechanism known as RNA interference. These agents have called special
attention to medicine since they have been used to experimentally treat a series of neurological conditions with distinct
etiologies such as prion, viral, bacterial, fungal, genetic disorders and others. siRNAs have also been tested in other
scenarios such as: control of anxiety, alcohol consumption, drug-receptor blockage and inhibition of pain signaling.
Although in a much earlier stage, miRNAs mimics, anti-miRs and small activating RNAs (saRNAs) also promise novel
therapeutic approaches to control gene expression. In this review we intend to introduce clinicians and medical
researchers to the most recent advances in the world of siRNA- and miRNA-mediated gene control, its history,
applications in cells, animals and humans, delivery methods (an yet unsolved hurdle), current status and possible
applications in future clinical practice.