ABSTRACT Background: Cell-free microRNAs (miRNAs) exist in body fluid. Previous studies showed that cell-free mi-RNAs are partly bound in microvesicles, and could transfer between cells via fusion with cell membrane. Methods: We quantified the amount of a panel of mi-RNA targets in and outside microvesicles in human proximal tubular epithelial cell (HK2) medium by microarray and real-time quantitative polymerase chain reaction (RT-QPCR). Intercellular miRNA transfer was explored by medium transfer experiments. Results: We identified a portion of cell-free miRNAs that exists as non-vesicle bound, truly naked form. More importantly, these non-vesicle bound free miRNA could transfer between cells and exert biological effects. By miRNA microarray, we showed that the expression of many miRNA targets in HK-2 cells were altered, either up- or down-regulated, after exposure to extrinsic free miRNAs. The miRNA-200 family was the most affected in our model, with a corresponding alteration in the messenger RNA expression of down-stream targets including ZEB1 and vimentin. Conclusion: Our results suggest that free miRNA may serve as an intercellular messenger, a phenomenon that needs further exploration.
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Wang, G. , Lai, K. , Kwa, B. , Chow, K. , Li, P. and Szeto, C. (2012) Non-vesicle-bound free microRNAs could enter cells and affect gene expression. Advances in Bioscience and Biotechnology, 3, 181-185. doi: 10.4236/abb.2012.33026.
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