Milk-derived exosomes as drug delivery vehicles and regulators of cell function

Exosomes are members of a larger family of extracellular vesicles that play major roles in intercellular communication and cell functions. Milk exosomes are secreted from mammary gland epithelial cells of all mammals including dairy cows, undergo intestinal uptake in rodent and human and deliver their cargos to specific tissues. Recent studies reported that milk exosomes can successfully deliver various drugs both orally and intravenously. Here we examined the uptake and effects of milk exosomes in various cell types and analyzed the ability of these exosomes to deliver RNA-based therapies. Milk exosomes were isolated by differential centrifugation and analyzed by NTA and Western blot analysis for size, quantity and surface markers. Using confocal microscopy and ImageStream analysis, we demonstrated uptake of exosomes to various mouse and human cells, including primary muscle and tumor cells and different cell lines. Milk exosomes increased the proliferation of both human and mouse muscle satellite cells and the expression of MyoD. In contract, treatment of various tumor cells with these exosomes either decreased cell proliferation or had no significant effects. We next demonstrated that milk exosomes can deliver exon skipping antisense oligonucleotides into muscle cells and specific miRNA mimics into muscle and glioma cells. Exosomal delivery of miR-29c into muscle cells increased muscle differentiation, and delivery of miR-145 into glioma cells decreased cell proliferation, indicating functional delivery of the miRNAs. In summary, milk exosomes exert various effects on mouse and human cells and represent a viable nano-carrier of RNA-based therapies for the treatment of various diseases.