Delivery of exosomal miRNAs in vitro and in vivo

Exosomes are nano vesicles secreted by cells, and contain various molecules including protein, lipid and DNA/RNA. They are crucial mediators of the intercellular communication and serve as promising vehicles for drug delivery and gene therapy. Recently, accumulating evidence suggest that microRNAs (miRNAs) may serve as new and potentially powerful targets for therapeutic interventions against various human diseases. However, steadily and effectively delivering miRNA mimics or inhibitors to target cells remains a major obstacle. To enhance the efficacy of exosome-mediated delivery of miRNA molecules, it is crucial to develop a convenient and efficient method to enrich specific miRNAs or anti-sense oligos in isolated exosomes.

Here researchers from Boston University report a novel method to prepare specific miRNA molecule-loaded exosomes. Using a modified calcium chloride-mediated transfection method, they successfully enhanced the designated miRNA mimics or inhibitors in isolated exosomes directly, instead of transfecting their mother cells. They also compared this method with direct transfection of exosomes using electroporation. Both methods confirmed that exosomes can serve as cargos to deliver a robustly increased amount of selected miRNA mimic(s) or inhibitor(s) to the recipient cells. Delivery of these miRNA molecule enriched-exosomes subsequently results in highly efficient over-expression or deletion of the designated miRNAs in the recipient cells both in vivo and in vitro. Additionally, the researchers confirmed that exosome-delivered miRNA mimics or inhibitors are functional in the recipient cells. Collectively, they developed a novel protocol to conveniently manipulate exosomal miRNAs with high efficiency and successfully deliver the exosomal miRNA molecules to recipient cells.

Strategy to deliver miRNA-loaded exosomes in vivo and in vitro. Schematic experimental design for delivering miRNA-loaded exosomes.