from the greenfluorescentblog by Gal Haimovich –
Exosomes are extracellular vesicles that are thought to mediate cell-to-cell communication in eukaryotes. Briefly, exosomes are 50-100 nanometer (nm) sized vesicles produced by the endosomal system. They are exported out of the cell and can be found in every bodily fluid: plasma, saliva, milk, urine and more. These vesicles then enter recipient cells, and the cargo they carry (proteins, RNA molecules and lipids) modulate the physiology and/or gene expression of the recipient cell. Exosomes catch a lot of attention lately because of their clinical significance. First, exosomes might be used as biomarkers for some diseases (most importantly tumors). Second, they are being considered for therapeutics as a delivery system.
Although the formation and secretion of exosomes is fairly understood (though we are just beginning to understand how some cargo is being packed), it is less clear how exosomes enter recipient cells. Even less clear is what happens to them once they enter the cell.
I myself have been concerned with the math of exosome-mediated communication. In most papers, exosomes are isolated from the donor cells (e.g. from culture media), then concentrated before applying them on top of recipient cells in vitro. However, it is not always mentioned what is the ratio of exosomes/cells and it is also unclear how many exosomes actually enter the cells. Furthermore, it is still unclear how much cargo is carried by a single exosome. (read more…)
Source – greenfluorescentblog