Milk miRNAs encapsulated in exosomes are stable to human digestion and permeable to intestinal barrier in vitro

Milk exosomal miRNAs are bioactive nucleic acids. However, their stability against the digestive processes and bioavailability to the cellular functions is still controversial. In the present study, a novel in vitro digestion model has been used to investigate the stability of miRNAs encapsulated in the cow milk exosomes against the digestive processes, along with their uptake and trans-epithelial transport by intestinal epithelial cells. Milk exosomal miRNAs were found resistant to in vitro digestion with different digestive juice including saliva, gastric, bile and pancreatic juice. Milk exosomes were internalized by in vitro cultured intestinal epithelial cells in linear pattern until 2 h. Moreover, trans-epithelial transport of bovine milk exosomal miRNAs across the Caco-2 monolayer indicated their potential to cross the intestinal barrier. Overall, the results demonstrated that cow milk exosomes protect miRNAs against harsh digestive processes and they are able to cross the intestinal barrier to reach blood circulation for cellular function.