Extracellular Vesicle
The general term for a membrane-enclosed particle released from a cell that cannot reproduce independently.
CELLMEX Scientific Library
Small Extracellular Vesicles
Small extracellular vesicles are nanoscale, membrane-enclosed particles released by cells. They carry proteins, lipids, nucleic acids and other biological components capable of participating in intercellular communication.
Scientific Definition
What exactly is a small extracellular vesicle?
Extracellular vesicles are lipid-bilayer-enclosed particles naturally released by cells into tissues, biological fluids or laboratory culture media.
Small extracellular vesicles, commonly abbreviated as sEVs, are an operational EV category generally separated or described according to small particle size and related physical characteristics.
The designation sEV does not identify one uniform vesicle type. An sEV preparation may contain vesicles formed through more than one cellular pathway and may include exosome-associated populations.
Small Extracellular Vesicle
An operational category based principally on physical properties, size range or separation conditions.
Exosome
An EV associated with intraluminal formation inside multivesicular endosomal compartments before extracellular release.
Vesicle Biology
sEVs participate in cell-to-cell communication
Their biological properties reflect the originating cell, its physiological condition and the environment in which the vesicles were produced.
Lipid Membrane
A lipid bilayer encloses the vesicle and protects internal molecular components from the surrounding environment.
- Phospholipids
- Cholesterol
- Sphingolipids
- Membrane-associated proteins
Molecular Cargo
sEV preparations may contain several classes of biological material.
- Membrane and cytosolic proteins
- Messenger RNA
- MicroRNA and other non-coding RNA
- Lipids and metabolites
- DNA-associated material in some preparations
Recipient-Cell Interaction
sEVs may interact with recipient cells through several non-exclusive pathways.
- Cell-surface receptor binding
- Endocytic uptake
- Membrane interaction or fusion
- Endosomal signalling
- Transfer of selected molecular cargo
Biological Response
Recipient-cell responses may include changes in signalling, metabolism, gene expression or functional behaviour.
- Immune-cell communication
- Inflammatory signalling
- Vascular-cell responses
- Cellular stress responses
- Tissue-homeostasis signalling
Laboratory Production
From source cells to an sEV-enriched preparation
The resulting product is influenced by every stage of cell culture, collection, separation, formulation and storage.
Source-Cell Qualification
Define cell type, tissue origin, donor, passage number, identity and culture history.
Controlled Cell Culture
Maintain cells under documented media, supplement, oxygen, density and environmental conditions.
Conditioning and Collection
Collect culture medium after a defined period during which cells release soluble and vesicular components.
Clarification
Remove cells, large debris and selected larger particles through centrifugation, filtration or related processing.
Separation and Enrichment
Enrich sEVs using size-exclusion chromatography, filtration, ultracentrifugation, density separation or combined methods.
Concentration and Formulation
Prepare the intended particle concentration, carrier solution, container and final presentation.
Storage
Define temperature, storage duration, freeze–thaw limits and transport conditions.
Quality Review
Review particle, compositional, contaminant, microbiological, stability and functional information.
Scientific Characterisation
No single assay defines an sEV preparation
Characterisation requires complementary methods that examine physical properties, composition, contaminants, safety and biological function.
Particle Size and Concentration
Particle-tracking, resistive-pulse or related methods may estimate size distribution and concentration.
Morphology
Electron microscopy or comparable imaging may demonstrate membrane-enclosed vesicular structures.
EV-Associated Components
Protein, lipid or molecular analysis may identify selected components associated with EV-enriched preparations.
Non-Vesicular Components
Testing should consider soluble proteins, lipoproteins, aggregates and residual culture-media components.
Microbiological Quality
Sterility-related parameters, mycoplasma, endotoxin and source-material controls may be relevant to intended use.
Functional Assessment
Fit-for-purpose assays should measure a defined activity connected to the proposed mechanism of action.
Current Medical Use
How sEVs are presently used in medicine
Their principal medical uses remain within research, product development, clinical trials and diagnostic investigation rather than routine standard-of-care therapy.
Investigational Therapeutics
Defined sEV or EV preparations are administered in controlled clinical studies to evaluate safety, dose, feasibility and preliminary efficacy.
Biomarker Research
sEVs from blood, urine, saliva, cerebrospinal fluid and other specimens are studied as indicators of disease state or treatment response.
Therapeutic Delivery Research
Natural or engineered vesicles are investigated as delivery systems for RNA, proteins and selected therapeutic compounds.
Treatment-Response Monitoring
Changes in EV number or cargo may be evaluated as pharmacodynamic or disease-monitoring biomarkers.
Tissue and Disease Modelling
Laboratory studies use sEVs to examine signalling between immune, vascular, stromal, tumour and specialised tissue cells.
Regenerative Product Development
MSC-derived and other cell-derived sEVs are being developed as potential cell-free biologic platforms.
Uses and Indications
Principal areas of clinical investigation
These categories describe active research areas. They are not a declaration that sEV therapy is approved, established or clinically effective for each condition.
Pulmonary and Critical Care
Clinical studies have investigated MSC-derived EV preparations in acute respiratory distress and related inflammatory lung injury.
Neurological Disorders
Research includes stroke, neuroinflammation, neurodegeneration, neural injury and delivery across specialised biological barriers.
Wound and Skin Disorders
Studies examine epithelial repair, fibroblast signalling, vascular responses and inherited wound disorders.
Musculoskeletal Medicine
Research includes osteoarthritis, cartilage, tendon, bone, muscle and inflammatory joint environments.
Ocular Disease
Early clinical development includes topical or local vesicle-based preparations for selected ocular surface and retinal conditions.
Immune-Mediated Disorders
Studies examine how vesicular signals influence macrophages, lymphocytes, dendritic cells and inflammatory pathways.
Cardiovascular Disease
Preclinical and translational programmes examine vascular signalling, cardiac injury, angiogenesis and cellular survival.
Renal and Hepatic Injury
Research evaluates inflammatory, vascular, anti-apoptotic and tissue-support pathways in organ injury models.
Oncology
Tumour-derived EVs are investigated as biomarkers and therapeutic targets, while engineered EVs are studied as potential delivery systems.
Clinical and regulatory qualification
Small extracellular vesicles, exosomes, purified exosomes, secretome and conditioned medium are related but distinct biological materials. The terms should not be used interchangeably.
Research activity in cultured cells or animals does not independently establish safety or effectiveness in human patients.
Product quality depends on source cells, culture conditions, separation methods, formulation, storage, dose and route of administration. Preparations produced by different laboratories cannot be assumed to be equivalent.
At present, therapeutic sEV applications remain predominantly investigational. Participation in a properly authorised clinical study is different from purchasing an unverified commercial procedure.
sEV products should not be presented as established cures for neurological, autoimmune, cardiovascular, pulmonary, metabolic, orthopaedic or other diseases without appropriate product-specific human evidence and applicable regulatory authorisation.
The CELLMEX Approach
Source, process and function must be defined together
Defined Source Cells
Tissue source, donor, cellular identity, passage number and culture history should be documented.
Controlled Vesicle Production
Medium, conditioning period, cell density, environmental conditions and collection procedures should be standardised.
Appropriate Enrichment
Separation methods should reflect the intended particle population, purity requirement and downstream application.
Integrated Characterisation
Particle, morphology, composition, contaminant, stability and functional data should be interpreted together.
Selected Scientific References
sEV biology, characterisation and clinical development
Welsh JA, et al. Minimal information for studies of extracellular vesicles: MISEV2023.
Journal of Extracellular Vesicles. 2024;13:e12404.
View publicationThéry C, et al. Minimal information for studies of extracellular vesicles 2018: MISEV2018.
Journal of Extracellular Vesicles. 2018;7(1):1535750.
View publicationvan Niel G, D'Angelo G, Raposo G. Shedding Light on the Cell Biology of Extracellular Vesicles.
Nature Reviews Molecular Cell Biology. 2018;19:213–228.
View publicationYáñez-Mó M, et al. Biological properties of extracellular vesicles and their physiological functions.
Journal of Extracellular Vesicles. 2015;4:27066.
View publicationU.S. Food and Drug Administration. Consumer information concerning regenerative-medicine and exosome products.
Regulatory and patient-safety information.
View FDA informationEuropean Medicines Agency. MSC-derived small extracellular vesicles loaded with siRNA for spinal-cord-injury development.
EU orphan designation EU/3/24/2990. Orphan designation does not constitute marketing authorisation.
View EMA designation
Scientific Information
Explore CELLMEX small extracellular-vesicle research
Physicians, researchers and institutions may request information concerning source-cell systems, sEV enrichment, characterisation, functional assays and scientific collaboration.