Exosomes are small membrane vesicles or microvesicles, shed by cells into the bloodstream. They were considered as biological trash cans with the function of discarding or cleaning unwanted cellular particles, but scientists have discovered that they play an integral role in intercellular communication.
Each exosome transmits DNA and RNA molecules through the blood and other biofluids. They can be isolated from the biofluid, and their high-quality DNA and RNA cargo can be extracted for analysis. Exosomes play an integral role in complex long-distance delivery because as they move between different cell types they transfer specific genetic information from their original host cells. Cells shed exosomes under both normal and pathological conditions, influencing other cells in either a positive or negative way. Thus, exosomes shed from a virus-infected cell behave like a virus because they bring with them genetic cargo that is translated to proteins in the other cells they come in contact with.
Exosomes also hold promise in biomarker identification, as tumor cells release exosomes which contain tumor-specific RNAs that can be easily isolated and identified from biofluids. Specific exosome contents vary depending on the cell of origin, but to identify and explore further, there must first be effective isolation and purification of the nucleic acids. Also, miRNA can be isolated from inside of the exosomes.
Ultracentrifugation is the current method for isolating exosomes, but it is not the most practical. Drawbacks of ultracentrifugation include the extended amount of time and labor involved, as well as low reproducibility and high levels of unavoidable contamination with cellular debris. When trying to capture just the exosome and not all the other cellular material, scientists will require cleaner, more reliable methods that produce highly pure exosome preparations, so they can trust that the nucleic acids they isolate are truly exosome-associated.
Scientists need a fast and convenient isolation method of mRNA and miRNA from extracellular vesicles present in fresh or frozen samples. This method needs to efficiently isolate all mRNA from the sample, enrich the vesicle-bound miRNAs and needs to work with both plasma and serum.
As we learn more about the role of exosomes, we will be able to decipher their role in the body and their importance in medical research. Developing the right technology to isolate exosomes will be critical.