Plant MicroRNAs—Novel Players in Natural Medicine?

MicroRNAs (miRNAs) represent a class of small non-coding RNAs that act as efficient gene expression regulators and thus play many important roles in living organisms. Due to their involvement in several known human pathological and pathogenic states, miRNA molecules have become an important issue in medicine and gained the attention of scientists from the pharmaceutical industry. In recent few years, a growing number of studies have provided evidence that miRNAs may be transferred from one species to another and regulate gene expression in the recipients' cells. The most intriguing results revealed that stable miRNAs derived from food plants may enter the mammals' circulatory system and, after reaching the target, inhibit the production of specific mammalian protein. Part of the scientific community has perceived this as an attractive hypothesis that may provide a foundation for novel therapeutic approaches. In turn, others are convinced about the "false positive" effect of performed experiments from which the mentioned results were achieved. In this article, we review the recent literature that provides evidence (from both fronts) of dietary, plant miRNA uptake and functionality in various consumers. Additionally, we discuss possible miRNA transport mechanisms from plant food sources to human cells.