EVOLUTION OF EXOSOME SCIENCE

Research into vesicles released by cells progressively revealed that extracellular material can contain organised molecular components. Investigations in immune biology and RNA transfer helped establish that some EV populations participate in biological interactions between cells. Studies of B-cell-derived vesicles and exosome-associated RNA transfer were influential examples of this transition. [1, 2]

The functional interpretation of an EV preparation depends on its cellular origin, composition, isolation procedure and experimental context. A demonstrated effect in one model cannot automatically be attributed to all exosomes or EV populations. [3, 4]

Human cell-derived EVs have been investigated in diverse biological systems, including immune, vascular and tissue-related research. Mesenchymal stromal/stem cell (MSC)-derived EVs attracted particular interest because experimental studies suggested that some effects associated with MSC-conditioned media may involve secreted factors, including EVs. [5, 6]

Preclinical investigations have examined EV-associated effects on inflammatory pathways, angiogenesis and tissue responses. These outcomes vary with the source cells, culture conditions, experimental model and EV preparation. Evidence from laboratory or animal studies should be distinguished from evidence of safety and effectiveness in humans. [4–6]

A central challenge in EV research is heterogeneity. Source-cell identity, donor characteristics, culture environment, collection conditions, processing, storage and separation methods can all affect the composition of the final preparation. [3–6]

Comparability therefore requires more than a particle count or a nominal size range. Research reports should describe the biological source, sample processing, separation strategy, relevant contaminants, characterisation measurements and controls used for functional interpretation. [3, 4]

Interest in EVs has contributed to broader research on cell-free biological preparations. EVs are non-cellular particles and do not reproduce as living cells do; nevertheless, their composition, biological activity and possible risks require independent evaluation. [3–6]

The absence of intact administered cells does not, by itself, demonstrate superior safety, predictable biological effects or regulatory simplicity. For investigational therapeutic uses, questions of identity, purity, potency, biodistribution, dose, manufacturing controls and clinical evidence remain central. [5, 6]

EV and EV-like particle research now encompasses multiple biological sources, including mammalian cells, microorganisms and plants. Plant-derived extracellular vesicle research examines the isolation, composition and potential biological interactions of particles obtained from plant materials. [7, 8]

Comparisons across biological sources require care: production pathways, molecular composition, preparation methods and analytical markers are not necessarily interchangeable. Claims concerning immunogenicity, scalability, consistency or suitability for particular applications must be evaluated for the specific material and process studied. [4, 7, 8]

The detailed biology of plant-derived particles is addressed separately in the Plant-Derived Exosome Science section of this library.

As EV studies increased, the International Society for Extracellular Vesicles (ISEV) developed guidance to improve methodological transparency and reproducibility. MISEV2018 and MISEV2023 address sample collection, separation, characterisation, functional studies and reporting practices. [3, 4]

Methods such as size-exclusion chromatography, differential centrifugation and affinity-based capture are used to separate or enrich EV populations. Electron microscopy, particle measurements and molecular assays contribute to characterisation. No single measurement reliably establishes an exosome identity or the biological origin of every particle in a heterogeneous preparation. [3, 4]

EV science spans basic research, preclinical studies, biomarker investigations and exploratory clinical research. The strength of evidence differs substantially across these areas. A mechanistic observation, a positive result in a cell culture model and a controlled clinical outcome answer different scientific questions. [4–6]

Ongoing priorities include robust preparation identity, reproducible manufacturing, relevant potency measurements, appropriate safety evaluation and well-designed clinical studies. These requirements are essential for determining whether particular EV preparations can be translated into specific applications. [4–6]