Exosomes

Refers to tiny vesicles enriched in nucleic acids and proteins and released from cells.

Implicated in muddling of cell to cell communication and in the transfer of undesirable information from one cell to another.

Results include stimulating proliferation, motility, and invasive properties of recipient cell, transferring drug resistance, inducing formation of endothelial tubules and attracting cancer cells to secondary sites.

Suggestion exosomes of cancer cells are dynamic factories contributing to progression of disease.

Structurally they are lipids-bilayer protective vesicles that maintain stability under varying conditions and protect their contents from degradation.

Contents include multiple types of RNA as well as DNA and proteins.


Exosomes are extracellular vesicles produced in the endosomal compartment of most eukaryotic cells.


The multivesicular body is an endosome defined by intraluminal vesicles that bud inward into the endosomal lumen. 


If the  multivesicular body fuses with the plasma membrane, these intraluminal vesicles are released as exosomes. 


Exosomes are present in tissues and can also be found in biological fluids including blood, urine, and cerebrospinal fluid. 


Exosomes are generally thought to be smaller than most other extracellular vesicles, from about 30 to several hundred nanometres (nm) in diameter.


Exosomes are around the same size as many lipoproteins but much smaller than cells.


EVs including exosomes carry markers of cells of origin and have specialized functions in physiological processes, from coagulation and intercellular signalling to waste management.


Exosomes participate in selective removal of many plasma membrane proteins.


In the reticulocyte, portions of the plasma membrane are regularly internalized as endosomes.


50 to 180% of the plasma of the reticulocyte membrane is recycled every hour.


Parts of the membranes of some endosomes are subsequently internalized as smaller vesicles,

called multivesicular bodies.


Intralumenal endosomal vesicles inside the larger body become exosomes if the MVB merges with the cell membrane, releasing the internal vesicles into the extracellular space.


Exosomes contain  proteins and RNA. 


Exosomes can transfer molecules from one cell to another by  membrane vesicle trafficking


Exosome trafficking influences the immune system, such as dendritic cells and B cells, and may play a functional role in mediating adaptive immune responses to pathogens and tumors.


mRNA in exosomes has been suggested to affect protein production in the recipient cell.


Exosome production  and content may is influenced by the cell of origin. 


Tumor cells exposed to hypoxia secrete exosomes with enhanced angiogenic and metastatic potential.


Exosomes from red blood cells contain the transferrin receptor which is absent in mature erythrocytes. 


Dendritic cell-derived exosomes express MHC I, MHC II


Urinary exosomes may be useful as treatment response markers in prostate cancer.


Exosomes secreted from tumor cells can deliver signals to surrounding cells.


In melanoma, tumor-derived vesicles can enter lymphatics and interact with macrophages and B cells in lymph nodes.


Exosome release positively correlates with the invasiveness of ovarian cancer.


Urinary exosomes are useful in the detection of genitourinary cancers and mineralocorticoid hypertension.


Exosomes appear to play a role in the spread of alpha-synuclein.


Exosomes from immune system, such as dendritic cells and B cells, may play a role in mediating adaptive immune responses to pathogens and tumors, by transferring molecules from one cell to another.


Exosome production and content may be altered by molecular signals received by the cell of origin. 


Tumor cells adapt to a hypoxic microenvironment by secreting exosomes to stimulate angiogenesis or facilitate metastasis to more favorable environment.


Eexosomal protein content may change during the progression of chronic lymphocytic leukemia.


Tumor exosomal communication has the ability to mediate metastasis to different organs. 


Exosomes carry cargo, which can augment innate immune responses,and their proinflammatory effects are partially attributed to lipopolysaccharide, which is encapsulated within exosomes.


The diameter of exosomes is typically below 100 nm.


Exosomes contain RNA, proteins, lipids and metabolites depending on the cell type of origin. 


Mesenchymal stem cell exosomes activate several signaling pathways important in wound healing and bone fracture repair.


Mesenchymal stem cell exosomes induce the expression of growth factors: hepatocyte growth factor (HGF), insulin-like growth factor-1 (IGF1), nerve growth factor (NGF), and stromal-derived growth factor-1 (SDF1)).


Exosomes secreted by circulating fibrocytes, a population of mesenchymal progenitors involved in normal wound healing


Exosomes released from oral keratinocytes can accelerate wound healing.


Exosomes are highly effective drug carriers. 


Because exosomes are made up of cellular membranes with adhesive proteins on their surface, they  are specialize in cell–cell communications and can deliver therapeutic agents to target cells.







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