Detection of microRNA Expression in Human Peripheral Blood Microvesicles

Abstract

BackgroundMicroRNAs (miRNA) are small non-coding RNAs that regulate translation of mRNA and protein. Loss or enhanced expression of miRNAs is associated with several diseases, including cancer. However, the identification of circulating miRNA in healthy donors is not well characterized. Microvesicles, also known as exosomes or microparticles, circulate in the peripheral blood and can stimulate cellular signaling. In this study, we hypothesized that under normal healthy conditions, microvesicles contain miRNAs, contributing to biological homeostasis.Methodology/Principal FindingsMicrovesicles were isolated from the plasma of normal healthy individuals. RNA was isolated from both the microvesicles and matched mononuclear cells and profiled for 420 known mature miRNAs by real-time PCR. Hierarchical clustering of the data sets indicated significant differences in miRNA expression between peripheral blood mononuclear cells (PBMC) and plasma microvesicles. We observed 71 miRNAs co-expressed between microvesicles and PBMC. Notably, we found 33 and 4 significantly differentially expressed miRNAs in the plasma microvesicles and mononuclear cells, respectively. Prediction of the gene targets and associated biological pathways regulated by the detected miRNAs was performed. The majority of the miRNAs expressed in the microvesicles from the blood were predicted to regulate cellular differentiation of blood cells and metabolic pathways. Interestingly, a select few miRNAs were also predicted to be important modulators of immune function.ConclusionsThis study is the first to identify and define miRNA expression in circulating plasma microvesicles of normal subjects. The data generated from this study provides a basis for future studies to determine the predictive role of peripheral blood miRNA signatures in human disease and will enable the definition of the biological processes regulated by these miRNA.

Functional delivery of viral miRNAs via exosomes

“…This further emphassizes the potential role of miRNA and exosomal transfer in EBV biology. From the published literature, it is nevertheless clear that cellular miRNAs are present in exosomes from both cultured cells and human sera (5)(6)(7)32). Interestingly, we detected significant numbers of BART-miRNAs in circulating noninfected non-B cells, suggesting that these miRNAs may have been transferred because the EBV genome was absent in these cells.…”

“…Because multiple studies show that miRNAs are present in microvesicles/exosomes secreted by multiple cell types in culture and human sera (5)(6)(7)32), a cellular miRNA-loading mechanism may exist that directs miRNAs to the intraluminal vesicles of MVEs. Indeed two independent reports showed that the RNAinduced silencing complex (RISC) is closely associated with MVEs that regulate miRNA-mediated gene silencing (25,33).…”

Potential relevance of microRNAs in inter-species epigenetic communication, and implications for disease pathogenesis

“…Experimental data support that miRNAs in membranebound vesicles 24 and complexed with HDL 25 might enter cells and influence gene expression. Several findings support that exosomal miRNAs secreted from tumors are involved in intratumoral epigenetic communication by influencing nearby tumor cells, but non-tumorous cells (e.g., interstitial, immune or endothelial cells) are also modulated.…”

Reduction of plasma MicroRNA-21 is associated with chemotherapeutic response in patients with non-small cell lung cancer

“…This result indicated that surgery can decrease miRNA expression, but not to normal level. Several more recent studies have documented that tumor cells released functional miRNA-enriched microparticles into the blood [37][38][39][40] . Nevertheless, the mechanism of plasma miRNAs generation and physiological function are unclear.…”