L'effetto dei microRNA della mela sulle cellule intestinali: l'importanza del trans-kingdom nella regolazione della proliferazione della mucosa intestinale

MicroRNAs (miRNAs) are small, endogenous, single-stranded RNAs that act on gene silencing at post-transcriptional level, by binding to a target messenger RNA (mRNA), leading to its degradation or inhibiting translation into functional proteins. The crucial role of miRNAs in development, proliferation, differentiation, and apoptosis has been deeply investigated, revealing that deregulation in their expression is critical to the onset of various human diseases, such as metabolic disorders and cancer. Since these small molecules initially evolved as a mechanism of defence against viruses and transposable elements, the idea that they can move between organisms of the same species as well as of different species arises. When the migration occurs between species, it is termed “trans-kingdom”. This mechanism has been well analysed between plants and their pests, in order to boost defence and increase pathogenicity. In the last decades, the hypothesis that also plant-human trans-kingdom, via food intake can occur, emerged. In particular, various studies highlighted the ability of exogenous miRNAs, abundant in the mainly consumed plant-derived food, to enter the human body affecting gene expression. Notably, plant miRNAs can resist the strict conditions of the gastrointestinal tract through a methylation step that occurs during plant miRNA maturation, conferring high stability to these small molecules. Recent studies observed the ability of exogenous plant miRNAs to modulate human genes involved in tumour onset, immune modulation and inflammatory pathways, thus leading to increasing interest in the trans-kingdom, via plant-derived food ingestion. In order to study the trans-kingdom hypothesis between plant and human, we focused on apple (Malus domestica), one of the most consumed fruit worldwide, that is rich in bioactive compounds (polyphenols and flavonoids), the molecules involved in the beneficial effect of fruit consumption. In this study, we show, for the first time, the trans-kingdom between apple miRNAs and human body. In particular, fruit miRNAs, derived from apple and a fruit mix, have been extracted, in order to identify apple-specific miRNAs. MiR-482a-3p and miR-858 have been selected and used to evaluate their ability to affect human intestinal cells, in vitro. MiRNA mimicking apple ones have been transfected in human intestinal cell lines, HT-29 and HCT116, demonstrating the ability of exogenous miRNAs to enter human cells and affect cell proliferation. Subsequently, using an in silico approach, we investigated the putative human target genes for the two apple-derived miRNAs, which could be involved in cell proliferation inhibition. In particular, we focused on gene mainly involved in cancer onset and progression. Among the putative targets, the oncogene c-MYB showed a down-regulation, both at mRNA and at protein level, in cell lines transfected with apple-derived miR-482a-3p, directly participating in the regulation of the enterocytes cell cycle. This study contributes to the intriguing trans-kingdom hypothesis, highlighting that plant-derived miRNAs could directly modulate enterocyte lifespan and metabolic action, thus leading to the possibility of using exogenous miRNAs as novel therapeutic molecules.