Abstract: Objective To evaluate the biological characteristics of exosomes secreted by adipose-tissue derived mesenchymal stem cells(AD-MSCs) and to evaluate the effects of these exosomes on microRNA expression of breast cancer cell MCF7. Methods Exosomes were isolated from supernatant of AD-MSCs by ultracentrifugation and ultrafiltration. The morphology was observed under electron microscope. Surface marker expression of exosomes was detected by Western blot. Dil-labeled exosomes were added into MCF7 culture medium and the internalization of exosomes by MCF7 was observed under fluorescence microscope. MicroRNA array chip was used to investigate the microRNA expression changes in MCF7 before and after exosome treatment for 24 h. MicroRNA array chip was also used to detect the expression of microRNAs in exosomes. Results AD-MSCs secreted 30~100 nm exosomes which expressed protein makers CD63 and HSP70. Exosomes from AD-MSCs could be internalized by MCF7 and cause microRNA expression changes in MCF7. 244 microRNAs were differentially expressed in MCF7 after treatment with exosomes for 24 h(174 were up-regulated and 70 were down-regulated, with fold change>2). MicroRNA array analysis of exosomes indicated that most of the increased microRNAs in MCF7 were generated endogenously, not derived from exosomes. Conclusion Exosomes from AD-MSCs can regulate microRNA expression of breast cancer cell MCF7, which might be the new mechanism by which AD-MSCs affect MCF7.

Key words: Exosomes, Mesenchymal stem cell, MicroRNA, MCF7