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Loading of non-coding nucleic acids in exosomes: microRNA, lncRNA, circRNA, and their functional significance

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In recent years, extracellular vesicles (EVs)—particularly exosomes—have emerged as key players in cellular communication. These nanosized vesicles released by cells act as carriers of biological information, transporting lipids, proteins, and nucleic acids. Among these, non-coding RNAs (ncRNAs)—including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs)—have gained increasing attention. They act as crucial regulators of intracellular signaling pathways. They are also promising tools for diagnostic and therapeutic applications.

This article explores how different types of ncRNAs transported by exosomes regulate cellular pathways. It also examines how this knowledge can be harnessed for diagnostic and therapeutic purposes.

Exosomes and Their Relevance in ncRNA Biology

Exosomes are extracellular vesicles ranging from 30 to 100 nm in diameter, released when multivesicular bodies (MVBs) fuse with the plasma membrane. Their cargo includes lipids, proteins, DNA, and a wide variety of RNAs—particularly non-coding RNAs. Because exosomes can travel between cells, they serve as vehicles of intercellular communication, with their ncRNA content capable of modifying the function and phenotype of recipient cells.

Research on ncRNAs within exosomes is expanding rapidly, offering enormous potential for biotechnology companies such as Immunostep. Understanding exosomal ncRNA biology may enable the development of advanced liquid biopsy biomarkers and next-generation therapeutic delivery platforms.

Types of Non-Coding RNAs in Exosomes

microRNAs (miRNAs)

miRNAs are small (~21–24 nucleotides) regulatory RNAs that bind to complementary sequences in the 3′ untranslated regions (3′UTR) of target mRNAs, promoting mRNA degradation or inhibiting translation (SpringerLink).

When encapsulated in exosomes, miRNAs act as mobile messengers, allowing donor cells to influence gene expression and behavior in recipient cells.

Long Non-Coding RNAs (lncRNAs)

lncRNAs are transcripts longer than 200 nucleotides that lack protein-coding potential but exert regulatory functions through mechanisms such as epigenetic modulation, chromatin remodeling, miRNA sponging, and transcriptional regulation (exRNA Journal)

Cells selectively package exosomal lncRNAs, which can induce transcriptional reprogramming in target cells and contribute to proliferation, differentiation, and tumor progression.

Circular RNAs (circRNAs)

circRNAs are covalently closed RNA molecules generated by back-splicing, forming circular structures resistant to exonucleases. These molecules are abundant and stable in exosomes (Cancer Cell Int.) circRNAs often act as miRNA sponges, regulating pathways involved in cell proliferation, apoptosis, and metastasis (PubMed)

Functional Mechanisms: How Exosomal ncRNAs Regulate Cellular Pathways

The ncRNAs carried by exosomes participate in multiple regulatory mechanisms that affect gene expression and cell signaling:

  • miRNA sponging: Both lncRNAs and circRNAs contain miRNA response elements (MREs) that sequester specific miRNAs, thereby modulating the expression of downstream target genes involved in proliferation, apoptosis, or migration (PubMed)

  • Epigenetic and chromatin modulation: Some exosomal lncRNAs can localize to the nucleus of recipient cells, interact with chromatin-modifying complexes, and reshape gene expression programs (SpringerLink)
  • Intercellular signaling transfer: Cells can alter their microenvironment through the release of ncRNA-loaded exosomes that influence neighboring or distant cells. In the cardiovascular system, for example, exosomal ncRNAs modulate hypertrophy, fibrosis, and apoptosis during cardiac remodeling (MedSci)
  • Regulation of drug resistance: Exosomes containing miRNAs, lncRNAs, or circRNAs can mediate chemoresistance by transferring regulatory RNA molecules that activate survival pathways in recipient tumor cells (PubMed)

Collectively, exosomal ncRNAs act as regulatory messengers capable of reprogramming gene expression, modifying signal transduction cascades, and altering cellular phenotypes.

Implications for Diagnosis and Therapy

The presence of ncRNAs in exosomes provides two major translational opportunities: biomarker discovery and therapeutic innovation.

Diagnosis: Non-Invasive Biomarkers

  • Exosomes circulate in body fluids (blood, urine, cerebrospinal fluid) and protect their RNA cargo from degradation, making them ideal for liquid biopsy applications.

  • Studies have shown that exosomal lncRNAs and circRNAs can serve as diagnostic and prognostic biomarkers in cancer, diabetes, and cardiovascular diseases (exRNA Journal)

  • In breast cancer, validated lncRNA/circRNA–miRNA–mRNA axes within exosomes have been proposed as prognostic indicators (PubMed)
  • In cardiac remodeling, circulating exosomal ncRNAs can predict fibrosis, hypertrophy, or heart failure progression (MedSci)

For companies like Immunostep, the characterization of exosomal ncRNAs represents a potential route to develop specialized reagents for biomarker profiling and clinical monitoring.

Therapy: Vehicles and Targets

  • Exosomes can be engineered as natural delivery vehicles for therapeutic RNA molecules (miRNAs, siRNAs, or circRNAs), taking advantage of their biocompatibility and stability (Cihan University ePrints)

  • Conversely, targeting exosomal ncRNAs—either by blocking their secretion or inhibiting their uptake—may suppress oncogenic signaling and prevent drug resistance (Translational Medicine)
  • Early-stage ncRNA-based therapeutics are already being tested in clinical trials, validating this approach as a realistic therapeutic strategy (Translational Medicine)

Thus, both diagnostic and therapeutic exploitation of exosomal ncRNAs represent powerful directions for translational biotechnology and precision medicine.

Challenges and Future Directions

Despite the promise, several challenges remain before exosomal ncRNA research reaches full clinical maturity:

  • Standardization of exosome isolation and ncRNA quantification methods (MDPI ncRNA Journal) 

  • Understanding selective cargo loading: mechanisms governing ncRNA packaging into exosomes remain incompletely defined.

  • Functional validation: many ncRNA–pathway associations are correlative and require mechanistic elucidation.

  • Targeted delivery and safety: ensuring tissue specificity and preventing off-target effects in exosome-based RNA therapeutics.

  • Researchers must rigorously evaluate large patient cohorts and establish regulatory frameworks before clinical deployment.

Conclusion

The loading of non-coding RNAs (miRNAs, lncRNAs, circRNAs) into exosomes represents one of the most exciting frontiers in molecular biology. It is also a key aspect of translational biotechnology. Exosomal ncRNAs play critical roles in cellular communication, gene regulation, and disease modulation. They offer vast potential for diagnostic and therapeutic applications.

For companies like Immunostep, advancing research and product development in this field—through exosome characterization tools, biomarker reagents, or RNA-based delivery systems—could provide a distinct competitive edge. This advantage applies in the evolving landscape of molecular diagnostics and biotherapeutics.