Abstract

Exploring the Small RNA World of Extracellular Vesicles

Esther Nolte-‘t Hoen, Assistant Professor, Department of Biochemistry & Cell Biology, Faculty of Veterinary Medicine, Utrecht University

Cell-derived extracellular vesicles (EV) have come in the limelight as biological entities containing unique combinations of lipids, proteins and genetic material containing lipids, proteins, and RNA. RNA present in EV can communicate genetically encoded messages to other cells, and may also be suitable as biomarkers for diseases. However, limited knowledge is available on the heterogeneity in the RNA content of different EV types, on mechanisms regulating RNA incorporation into EV, and on how transferred RNAs function in EV-targeted cells. Within the International Society for Extracellular Vesicles we recently reported on possibilities and limitations of strategies to analyze EV-RNA. Technical challenges include improvement and standardization of methods to purify EV away from non-EV-associated extracellular RNA, efficient recovery of minute quantities of EV-associated RNA, and biases in EV-RNA characterization. The currently most intensely studied EV-RNA biotypes are miRNAs and mRNAs, some of which have been implicated in disease progression and/or proved valuable as biomarkers. However, EV released by many different cell types are particularly rich in other small RNA biotypes such as tRNA, Y-RNA, SRP-RNA, Vault RNA, and snoRNA, which may also exert gene regulatory functions. Using primary immune cells, we investigated which RNA biotypes were consistently present in EV and which types were differentially incorporated depending on the type of stimulation imposed on the cells. Levels of not only miRNAs, but also other non-coding RNA types varied depending on the status of the parent cell and may be further explored as biomarkers or functional entities within EV.