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The development and function of mammalian cells, like other multicellular animals, requires cell to cell interactions, which are carried out directly via cellular junctions or indirectly by secretion of secretory molecules such as hormones. During the last two decades, exosomes have been introduced as the third mechanism for cellular interactions. Exosomes are small vesicles with membranes and 30 to 100 nm in size that exist in blood, urine, saliva, semen, and serum. Exosomes play an important role in a variety of biological processes such as immune response and inflammation, pregnancy, tissue generalization, blood coagulation, and angiogenesis. Exosomes are also involved in pathologic process such as neurological disorders, cancer, infectious diseases, and cardiovascular diseases. Because of their small size, exosomes are able to cross the cell membrane and protect the proteins from degradation. They also have the potential of transferring different compounds into the cell. Due to their receiver specificity, lack of inducing immune system, and more importantly having the capacity to be engineered as drug carriers, exosomes have been introduced as new agents for the transfer of genetic material and disease treatment.

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Objective: Cell-derived microvesicles are described as a new mechanism for cell-to-cell communication. Stem cell-derived exosomes have been described as a new mechanism for the paracrine effects of mesenchymal stem cells (MSCs). In this regard, exosomes may play a relevant role in the intercellular communication between MSCs and tumor cells. Methods: Exosomes were purified from the conditioned medium of MSCs by differential centrifugation. Exosome size and morphology were examined by scanning electron microscope and sized with dynamic light scattering (DLS). Western blot analysis confirmed the exosomes by using CD9 as a marker. Purified exosomes were labeled with a PKH26 red fluorescent labeling kit. The labeled exosomes were incubated with SKOV3 ovarian tumor cells for 12 h at 37°C, and we used an inverted fluorescence microscope to monitor cellular uptake. Results: Scanning electron microscopy revealed that the purified MSCs-derived exosomes had a spherical shape with a diameter of approximately 30-100 nm. Exosome size measurement by dynamic light scattering analysis also showed a single bell-shaped size distribution with a peak of ~80 nm. Western blot analysis also demonstrated the presence of CD9 (a representative marker of exosomes) in the purified exosomes. These data confirmed that the vesicles isolated from MSCs-conditioned media were the exosomes based on their size and presence of the protein marker CD9. Florescent microscopy showed that PKH26-labeled exosomes could be taken up by SKOV3 tumor cells with high efficiency. Conclusion: Our approach for isolation, characterization and cellular uptake of exosomes derived from MSCs is valuable and a prerequisite for future studies that intend to discover exosome function in tumor cells. The ability to study the biology of exosome uptake in cancer cells could provide opportunities for functional studies of these natural nanovesicles and their contents in cancer therapy.

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Aims: Exosomes are considered as a protective and enriched source of shuttle microRNAs. However, the precise biological mechanism of exosomal microRNAs in recipient cells remains to be further clarified. The aim of this study waz to investigate Expression level of miR-9 in exosomes derived from ovarian epithelial carcinoma cells and the effects of exosome treatment on Vascular Endothelial Growth Factor )VEGF( expression in human umbilical vein endothelial cells.
Material and Methods: Exosomes were purified from the conditioned medium of ovarian epithelial carcinoma cells. Exosome size and morphology were examined by a scanning electron microscope. Purified exosomes were labeled with PKH26 red fluorescent labeling kit, then labeled exosomes were incubated with human umbilical vein endothelial cells (HUVECs) for 12h at 37°C, and the cellular uptake was monitored using an inverted fluorescence microscope. Expression levels of miR-9 and VEGF were measured by real-time PCR. Paired t-test was used for data analysis.
Findings: The purified MSCs-derived exosomes had a spherical shape with a diameter between 50 to 100nm. PKH26-labeled exosomes can be taken up by SKOV3 tumor cells with high efficiency. The expression levels of miR-9 in both ovarian tumor cells and their exosomes. Exosomes derived from ovarian tumor cells caused increased expression of VEGF in exosome-treated endothelial cells.
Conclusion: Exosomes derived from ovarian tumor cells led to increased expression of VEGF in endothelial cells. As miR-9 was enriched in both ovarian tumor cells and their exosomes, it seems that exosomal transfer of miR-9 may affect the expression of VEGF in endothelial cells during tumor angiogenesis.

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