Abstract
BackgroundExosomes are nano-sized vesicles of endocytic origin that are involved in cell-to-cell communication including shuttle RNA, mainly mRNA and microRNA. As exosomes naturally carry RNA between cells, these particles might be useful in gene cancer therapy to deliver therapeutic short interfering RNA (siRNA) to the target cells. Despite the promise of RNA interference (RNAi) for use in therapy, several technical obstacles must be overcome. Exogenous siRNA is prone to degradation, has a limited ability to cross cell membranes and may induce an immune response. Naturally occurring RNA carriers, such as exosomes, might provide an untapped source of effective delivery strategies.ResultsThis study demonstrates that exosomes can deliver siRNA to recipient cells in vitro. The different strategies were used to introduce siRNAs into human exosomes of various origins. The delivery of fluorescently labeled siRNA via exosomes to cells was confirmed using confocal microscopy and flow cytometry. Two different siRNAs against RAD51 and RAD52 were used to transfect into the exosomes for therapeutic delivery into target cells. The exosome-delivered siRNAs were effective at causing post-transcriptional gene silencing in recipient cells. Moreover, the exosome-delivered siRNA against RAD51 was functional and caused the massive reproductive cell death of recipient cancer cells.ConclusionsThe results strongly suggest that exosomes effectively delivered the siRNA into the target cells. The therapeutic potential of exosome-mediated siRNA delivery was demonstrated in vitro by the strong knockdown of RAD51, a prospective therapeutic target for cancer cells. The results give an additional evidence of the ability to use human exosomes as vectors in cancer therapy, including RNAi-based gene therapy.
Highlights
Exosomes are nano-sized vesicles of endocytic origin that are involved in cell-to-cell communication including shuttle RNA, mainly mRNA and microRNA
After the discovery that synthetic small-interfering RNAs (siRNAs) can be exogenously introduced into cells to activate RNA interference (RNAi) [8], this approach has become a powerful method for selective suppression of specific genes of interest in different species, showing potential for use in cancer therapeutics [2,3]
Introduction of siRNA into exosomes and delivery of heterologous siRNAs to recipient cells via exosomes Exosomes originating from HeLa and ascites were isolated by ultracentrifugation, as described earlier [22]
Summary
Exosomes are nano-sized vesicles of endocytic origin that are involved in cell-to-cell communication including shuttle RNA, mainly mRNA and microRNA. The biomedical utility of the synthetic siRNAs is limited by several RNA structure-related factors such as the negative charge (uptake by cells that have a negatively charged surface) and instability in the blood circulation (non-modified siRNAs have a very short half-life in the blood stream, mostly because of degradation by nucleases) [9]. Another major barrier is immunogenicity of the synthetic siRNAs or delivery vehicle, especially if repeated dosing is needed to treat disease [9,10]. Occurring RNA carriers, such as exosomes, might provide an untapped source of effective delivery strategies [11]
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