Exosomes are nano-sized vesicles, secreted by all types of cells and found abundantly in biofluids like blood, saliva and urine. These extracellular vesicles carry multiple functional passengers including DNA, miRNA, non-coding RNA and proteins, and function as intercellular communication vehicles by transporting molecules between specific cells.
microRNAs are small non-coding RNAs that play an intricate role in gene regulation and are negative regulators of gene expression. Similar to exosomes, microRNAs are present in all biofluids, but some circulating miRNAs are sheltered from destruction because they’re protected via the exosome. Therefore researchers are looking towards circulating miRNA for the possibility to be used as noninvasive biomarkers for a variety of indications.
Profiling microRNA is important for understanding how it regulates different biological pathways and contributes to disease. Reliable and reproducible microRNA research depends on sample isolation tools and technologies specifically designed for microRNA.
Step one is isolation of microRNA from starting materials, such as blood samples. Once isolated it can be profiled through universal reverse transcription and quantitative PCR. Data analysis identifies the miRNAs that are most important in the system, and the function of these miRNAs can be probed using miRNA mimics, miRNA inhibitors, or target protectors.
Isolating microRNA from blood can be challenging because some microRNAs are sequestered in exosomes, others are expressed in cells, and others circulate freely in association with proteins like Ago2 or HDL. How can we look at microRNAs from each of these populations, or from all of them? New technologies have improved our ability to specifically extract microRNA in exosomes, improving upon traditional methods that were time-consuming and provided a less pure preparation. These advances are highly likely to quicken the pace of biomarker discovery from exosome-associated miRNAs.