Exosomes are natural carriers of exogenous siRNA to human cells in vitro.
BACKGROUND
Exosomes 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.


RESULTS
This 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.


CONCLUSIONS
The 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.
Division of Molecular and Radiation Biophysics, SFBI Petersburg Nuclear Physics Institute, Gatchina 188300, Russia. filatov@omrb.pnpi.spb.ru.
Tatyana A
TA
Shtam
Roman A
RA
Kovalev
Elena Yu
EY
Varfolomeeva
Evgeny M
EM
Makarov
Yury V
YV
Kil
Michael V
MV
Filatov
D001202:Ascitic Fluid / Q000166:cytology; D045744:Cell Line, Tumor; D055354:Exosomes; D018014:Gene Transfer Techniques; D006801:Humans; D034741:RNA, Small Interfering / Q000008:administration & dosage*; D051135:Rad51 Recombinase / Q000235:genetics; D051721:Rad52 DNA Repair and Recombination Protein / Q000235:genetics
C497194:RAD52 protein, human; D034741:RNA, Small Interfering; D051721:Rad52 DNA Repair and Recombination Protein; C495153:RAD51 protein, human; D051135:Rad51 Recombinase