Human blood plasma contains a heterogeneous mixture of microvesicles, exosomes, apoptotic bodies, and lipoprotein particles. These particles have been previously shown to carry nucleic acid cargo in the form of microRNAs. Therefore, circulating microRNAs are a mixture of microRNAs present in the aforementioned subcellular particles. These microRNAs are known to be quite stable in blood plasma and the levels of specific circulating microRNAs can differ with diseases, leading to the possibility of using extracellular microRNAs as disease biomarkers.
In order to study only the exosome-associated microRNAs and proteins, it is important to remove as many subcellular particles as possible from blood plasma or serum, particularly lipoprotein particles. Lipoproteins are the major lipid-based particles in the plasma and serum. It has been recently demonstrated that both high-density lipoproteins (HDLs) and low-density-density lipoproteins (LDLs) contain microRNAs. In order to deplete as much of these lipoproteins, which may cause false positive "hits" in analysis of exosome-associated microRNAs, we have developed the kit containing exosome precipitation solution and proprietory pre-clearing reagents to efficiently deplete lipoprotein particles from plasma or serum.