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.

Arrangement of chromatin in intact chicken erythrocyte nuclei was investigated by small angle neutron scattering. The scattering spectra have revealed that on the scales between 15 nm and 1.5 μm the ...

This study was initiated to determine the relationship between the fertilizing potential of spermatozoa and abnormalities in the compact packing of their chromatin which occurs in the final stage of male germ cell differentiation. Chromatin packing involves disulphide bridge covalent cross-linking. The degree of packing was determined from the accessibility of DNA to a fluorescent dye, ethidium bromide, following detergent treatment of the spermatozoa. The amount of dye bound was determined by flow cytometry in the presence or absence of heparin, a polyanion which removes only non-disulphide bridge-linked proteins. The results of a number of different sperm samples were compared with their results following in-vitro fertilization, and a relationship between disordered sperm chromatin packing and rates of embryo cleavage was observed. This study suggests that abnormal chromatin packing in spermatozoa may contribute to male fertility.

The chromatin organization in chicken erythrocyte nuclei was studied by small-angle neutron scattering in the scattering-vector range from 1.5 × 10⁻¹ to 10⁻⁴ Å⁻¹ with the use of the contrast-variation technique. This scattering-vector range corresponds to linear dimensions from 4 nm to 6 μm and covers the whole hierarchy of chromatin structures, from the nucleosomal structure to the entire nucleus. The results of the present study allowed the following conclusions to be drawn: (1) both the chromatin-protein structure and the structure of the nucleic acid component in chicken erythrocyte nuclei have mass-fractal properties, (2) the structure of the protein component of chromatin exhibits a fractal behavior on scales extending over two orders of magnitude, from the nucleosomal size to the size of an entire nucleus, and (3) the structure of the nucleic acid component of chromatin in chicken erythrocyte nuclei is likewise of a fractal nature and has two levels of organization or two phases with the crossover point at about 300–400 nm.