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Updated: Jun 11, 2026
Tracking miRNA Release into Extracellular Vesicles using Flow Cytometry
Published on: October 6, 2023
Export of microRNAs and microRNA-protective protein by mammalian cells
Kai Wang1, Shile Zhang, Jessica Weber
1Institute for Systems Biology, 1441 N. 34th Street, Seattle, WA 98103, USA.
Abstract:
The discovery of microRNAs (miRNAs) as a new class of regulators of gene expression has triggered an explosion of research activities, but has left many unanswered questions about how this regulation functions and how it is integrated with other regulatory mechanisms. A number of miRNAs have been found to be present in plasma and other body fluids of humans and mice in surprisingly high concentrations. This observation was unexpected in two respects: first, the fact that these molecules are present at all outside the cell at significant concentrations and second, that these molecules appear to be stable outside of the cell. In light of this it has been suggested that the biological function of miRNAs may also extend outside of the cell and mediate cell-cell communication. We report here that after serum deprivation several human cell lines tested promptly export a substantial amount of miRNAs into the culture medium and the export process is largely energy dependent. The exported miRNAs are found both within and outside of the 16.5 and 120 K centrifugation pellets which contain most of the known cell-derived vesicles, the microvesicles and exosomes. We have identified some candidate proteins involved in this system, and one of these proteins may also play a role in protecting extracellular miRNAs from degradation. Our results point to a hitherto unrecognized and uncharacterized miRNA trafficking system in mammalian cells that is consistent with the cell-cell communication hypothesis.
Insights
Mammalian cells actively export microRNAs (miRNAs) into the extracellular environment via an energy-dependent process. This suggests a novel mechanism for cell-cell communication and extracellular miRNA stability.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- MicroRNAs (miRNAs) regulate gene expression and are found in body fluids.
- Extracellular miRNAs are stable and present in high concentrations, suggesting a role beyond intracellular regulation.
- The precise mechanisms of miRNA export and extracellular stability remain largely unknown.
Purpose of the Study:
- To investigate the active export of miRNAs from mammalian cells.
- To explore the characteristics and regulation of this miRNA export process.
- To identify potential mechanisms for extracellular miRNA stability and cell-cell communication.
Main Methods:
- Utilized human cell lines subjected to serum deprivation.
- Performed differential centrifugation to isolate extracellular vesicles (microvesicles and exosomes).
- Analyzed miRNA presence within and outside of cellular debris and vesicles.
- Identified candidate proteins involved in miRNA export and protection.
Main Results:
- Human cell lines promptly export substantial amounts of miRNAs into culture media upon serum deprivation.
- The miRNA export process is largely energy-dependent.
- Exported miRNAs are found within and outside of known cell-derived vesicles.
- Candidate proteins involved in miRNA trafficking and extracellular protection were identified.
Conclusions:
- Mammalian cells possess a previously unrecognized miRNA trafficking system.
- This system facilitates the export of miRNAs into the extracellular environment.
- The findings support the hypothesis that extracellular miRNAs mediate cell-cell communication.
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