Discovered only about fifteen years ago, research on the non-coding variant of RNA called microRNA (or miRNA) continues to expand its role. New work by Chen-Yu Zhang and colleagues at five Chinese institutions has identified miRNA as an important cell-to-cell and cell-to-organ communication mechanism, one that is more versatile than the traditional notion of cellular communication via hormones or antigens. The discovery opens a research window on a potentially very important ‘two-way’ chemical communication system within living organisms that permits ‘broadcast’ and ‘feedback’ of miRNAs with multiple genes as targets.
Ribonucleic acid, RNA, has many variations but most of them are involved in some form of molecular/chemical translation or communication. miRNA appears to be no exception, only until this recent work it was not fully understood just how sophisticated the communication might be. Dr. Chen-Yu Zhang had already reported in an earlier paper that miRNA could be used as a biomarker for some types of cancer. His research team also wanted to know how this marker miRNA was created, secreted from cells into the bloodstream, and then received by target cells. That became the basis for the new paper, published in the July 9, 2010 issue of the journal Molecular Cell as Secreted Monocytic miR-150 Enhances Targeted Endothelial Cell Migration.
Using human blood and mouse blood circulation as the experimental platform, they discovered that miRNA (specifically miR-150) can be packaged by cells and secreted into the bloodstream, where it travels to cells with appropriate receptors and penetrates into the target cells. Once inside the target cells, the miRNA participates (or initiates) the expression of certain genes (in this case those involved with the production and migration of cells in tiny blood vessels, ones often associated with atherosclerosis).
The present study extends our understanding of the role of miRNAs by illustrating that miRNAs can be secreted and delivered into target cells and that these exogenous miRNAs can alter the cellular functions of the recipient cells by modulating the expression of their target genes,” said Chen-Yu Zhang. “From this point of view, secreted miRNAs represent a novel class of signaling molecules that play an important role in mediating cell-to-cell and organ-to-organ communication.” Moreover, the secretion and targeting of miRNAs establishes a highly regulated complex network under various physiological and pathophysiological conditions.
Scientists have known for a long time that hormones are one primary signaling mechanism; antigen signaling has been known almost as long. Now can be added (subject to confirmation) a third method, microRNAs. Unlike hormones or antigens, which are largely one-way and restricted to certain cells, miRNA signaling can be ‘broadcast’ to a variety of cells, and can also be involved in ‘two-way’ communication between cells. While the exact mechanisms of this more sophisticated ‘network’ communication enabled by miRNAs is wide open for further study, it does hold the potential to widen (that is, complicate) the understanding of how organisms regulate gene expression in a coordinated fashion. Add this research as another piece of the unfolding story of epigenetics (genetic expression altered by environmental factors).