Studies in recent years have established that RNA contents in exosomes can serve as biomarkers for certain cancers (1). As exosomal RNA becomes more critical to research, successful isolation of these nanovesicles has become equally fundamental.
Exosomes are small (40–100 nm) nanovesicles containing RNA that can move between cells. Found in several biological fluids, including blood plasma and breast milk, exosomes differ from their donor cells in size, RNA, protein and liquid composition (2). Researchers use several different techniques for extraction of exosomal RNA, but these generally fall under 3 categories: phenol-based, column-based and combination phenol-and-column-based.
All 3 categories of extraction result in high-purity, high-quality RNA. However, each also results in significantly different yields and patterns, so it’s important to determine the optimal method for the study at hand. For example, a pure column-based isolation can result in a high RNA yield and a broad RNA size distribution pattern compared to phenol-based techniques. Meanwhile, a pure phenol-based approach or combination phenol-and-column-based approach can lose large RNAs, resulting in reduced overall yield of exosomal RNA, with a more narrow size distribution. This creates an enrichment of small RNA, including microRNA (2).
In conclusion, phenol-based approaches are more efficient for researchers extracting smaller-sized RNA where the sample amount isn’t as important, while pure column-based approaches are better for isolating larger samples in greater quantities. As exosomal RNA extraction becomes more necessary to the advancement of clinical and academic studies around the world, researchers should experiment with different extraction solutions within phenol-based, column-based and hybrid categories to determine what works best for their desired workflow and project goals.
Check out the exoRNeasy Serum/Plasma Kits which use a membrane affinity spin column-based approach to purify RNA from exosomes and other extracellular vesicles out of serum or plasma samples.
1. Eldh, M. (2014) MicroRNA in exosomes isolated directly from the liver circulation in patients with metastatic uveal melanoma. BMC Cancer 14, 962. Link See also: Rabinowits, G. et al. (2009) Exosomal microRNA: a diagnostic marker for lung cancer. Clin. Lung Cancer, 2009. 10, 42. Link
2. Eldh, M. et al. (2012) Importance of RNA isolation methods for analysis of exosomal RNA: Evaluation of different methods. Mol. Immunol. 50, 278. Link