Table 1.
The classification of extracellular vesicles and their main characteristics.
| Types of Extracellular Vesicles | Size [nm] | Appearance by Electron Microscopy | Markers | Genetical Information | Mechanism of Information | Release Process | Pathways | Lipid Membrane Composition | Protein Components | Intracellular Origin | References |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Exosomes | 50–150 | Cup shape | CD63, TSG101, Alix, flottlin, tetraspanins, Rab5a/b, HSP70, HSP90 | DNA, non-coding RNA, miRNA | Multivesicular bodies fusion with plasma membrane | Constitutive and/or cellular activation | ESCRT-dependent, tetraspanins-, ceramide-, stimuli- dependent | Enriched in cholesterol, sphingomyelin, ceramide, lipid rafts, phosphatidylserine | Tetraspanins (CD9, CD63, CD81, CD82), Multivesicular body biogenesis (ALIX, TSG101) | Endosomes | [21] |
| Microvesicles | 100–1000 | Irregular shape | Integrin, selectin, flittilin-2 | mRNA, miRNA | Outward blebbing of the plasma membrane | Constitutive and/or cellular activation | Ca2+ - dependent, cell- and stimuli-dependent | Expose phosphatidylserine, enriched in cholesterol, diacylglycerol, lipid rafts | Cell adhesion (integrins, selectins), death receptors (CD40 ligands) | Plasma membranes | [22] |
| Ectosomes | 100–500 | Bilamellar round structures | β1 integrins, selectins, CD40, MMP, lineage markers, erzin | mRNA, miRNA | Outward blebbing of the plasma membrane | Constitutive and/or cellular activation | Ca2+ - dependent, cell- and stimuli- dependent | Enriched in cholesterol, diacylglycerol, phosphatidylserine | Enzyme (proteolytic enzymes) | Plasma membranes | [23] |
| Large oncosomes | 100–400 | Heterogeneous | Cytokeratin-18, CD9, CD63, CD81, Cav-1 | mRNA, miRNA | Outward blebbing of the plasma membrane | Constitutive and/or cellular activation | EGFR & AKT pathways, silencing of the cytoskeletal regulator DIAPH3 by ERK | Phospholipid phosphatidylserine | Cytoskeleton components (cytokeratin 18), tetraspanins (CD9, CD81), cell adhesion molecules (integrin-α3, integrin-αV, ICAM, CD44) | Plasma membranes | [24] |
| Exosome-like vesicles | 20–50 | Irregular shape | VSV-G | mRNA, miRNA | From Golgi organelle membrane | Overexpression of VSV glycoprotein | Do not contain lipid rafts | Growth factors and cytokine (TNFR1) | Internal compartments | [25] | |
| Apoptotic vesicles | 1000–5000 | Heterogeneous | Histones, DNA, Annexin V | mRNA, miRNA, DNA | Programmed cell death and cell shrinkage | Apoptosis | Apoptosis-related | Phosphatidylserine | Transcription and protein synthesis (histones) | Plasma membrane, cellular fragments | [22] |
TSG101: tumor susceptibility gene 101; DNA: deoxyribonucleic acid; ESCRT: The endosomal sorting complexes required for transport; HSP: heat shock protein; RNA: ribonucleic acid; mRNA: messenger RNA; miRNA: microRNA; MMP: matrix metalloproteinase; Cav-1: caveolin-1; EGFR: epithelial growth factor receptor; ICAM: intercellular adhesion molecule 1; ERK: the extracellular-signal-regulated kinase; DIAPH3: diaphanous related formin 3; VSV-G: vesicular stomatitis virus G protein; TNFR1: tumor necrosis factor receptor 1.