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Exosomes; Biomarkers; Graft rejection; Organ transplantation; Early detection; Immunology; Extracellular vesicles; Diagnostics; Non-invasive monitoring; Immune response; Precision medicine; Transplant immunology; T-cell activation; Allograft; Molecular diagnostics

Introduction

Organ transplantation remains the gold standard treatment for end-stage organ failure, but graft rejection continues to be a major complication that threatens transplant survival. Early and accurate detection of rejection episodes is essential for timely therapeutic intervention and long-term graft function. Traditional diagnostic methods, such as biopsies and serum biomarkers, are either invasive or insufficiently sensitive. In recent years, exosomes—small extracellular vesicles secreted by nearly all cell types—have emerged as promising biomarkers due to their role in cell communication and their cargo of proteins, lipids, and nucleic acids reflective of their cell of origin. This review highlights the potential of exosome-based biomarkers for the early detection of graft rejection [1-5].

Description

Exosomes are nano-sized vesicles (30–150 nm) released by donor and recipient immune cells, which carry molecular signatures indicative of ongoing immunological processes. They can be isolated from bodily fluids such as blood, urine, and saliva, offering a non-invasive window into transplant health. In the context of organ transplantation, exosomes released from injured graft tissues or activated immune cells may contain specific proteins, mRNAs, and microRNAs (miRNAs) associated with rejection. For example, miR-155, HLA-G, and donor-derived exosomal RNA have shown potential as early indicators of acute rejection. These biomarkers provide insight into immune activation, inflammation, and tissue injury before clinical symptoms or histological damage becomes evident [6-10].

Discussion

The utility of exosome-based biomarkers lies in their stability, specificity, and ability to reflect real-time pathological changes. Unlike traditional serum biomarkers that may lack specificity, or biopsies that are invasive and time-consuming, exosomes can be routinely sampled and analyzed using techniques such as nanoparticle tracking analysis, RNA sequencing, and immunocapture assays. Studies in kidney, heart, and liver transplantation have demonstrated that exosomal miRNAs correlate with acute rejection episodes, and in some cases, precede detectable histological changes. Moreover, the ability to distinguish between different types of rejection—such as antibody-mediated versus T-cell mediated rejection—through exosomal content further enhances their diagnostic value. However, standardization of isolation protocols, analytical platforms, and validation in large-scale clinical trials are necessary before these biomarkers can be integrated into routine practice.

Conclusion

Exosome-based biomarkers offer a transformative approach for the non-invasive, early detection of graft rejection in organ transplantation. Their molecular richness and origin-specificity make them ideal candidates for monitoring immune activity and graft health in real-time. While preliminary studies are promising, clinical translation requires overcoming technical and regulatory challenges. Future research should focus on multi-center validation, refinement of exosome isolation techniques, and development of standardized diagnostic panels. Integrating exosome analysis into transplant care has the potential to improve outcomes through earlier diagnosis, personalized therapy, and reduced reliance on invasive procedures.

References

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