Caby et al. examined plasma samples from healthy donors and successfully identified vesicles of 50–90 nm in diameter that have the molecular and biophysical properties of exosomes.[70] Besides blood, exosomes have also been detected in various bodily fluids such as urine, cerebrospinal fluid, saliva, breast learn more milk, semen, amniotic fluid, malignant ascites, bronchoalveolar lavage fluid and synovial fluid.[71] The presence of urinary exosomes was verified when small vesicles (<100 nm in diameter) orientated ‘cytoplasmic-side inward’

were observed in normal urine with functions in urinary secretion of aquaporin-2 and other membrane-associated proteins[72] (see Fig. 2). The proteomic analysis of urinary exosomes identified proteins

characteristically restricted in expression to renal epithelia of the glomerular podocytes, the proximal tubule, the thick ascending limb of Henle, the distal convoluted tubule and the collecting duct. Proteins from the transitional epithelium of the urinary bladder were also identified, suggesting urinary exosomes may be derived from cells throughout the renal tract.[72-74] Thus, analysis of urinary exosomes provides an attractive non-invasive means of acquiring information about the pathophysiological state of their renal cells of origin. CD24, a small but extensively glycosylated protein linked to the cell surface by means of a glycosyl-phosphatidylinositol anchor, has been reported to be a marker for urinary exosomes.[75] It was previously thought that the main physiological role for urinary see more exosomes is the disposal of senescent Farnesyltransferase proteins from cells, which may be a more efficient way of protein elimination than proteasomal and lysosomal degradation,[76] similar to the process by which maturing

reticulocytes shed obsolete membrane proteins and remodel their plasma membrane through the exosomal pathway.[52] However, increasing evidence is suggesting that urinary exosomes play a role beyond exocytic cell waste elimination.[75, 77] Another possible role of exosomes in the urinary tract is to regulate the co-functioning between different parts of the nephron, through secretion and reuptake of their contents such as mRNAs and miRNAs that can affect the function of the recipient cell[73] (Fig. 1). Functional transfer of molecules such as aquaporin-2 between different renal cells has been described[78] and could mediate coordinate adaptation of nephron function. The role of circulating exosomes in physiological messaging remains poorly defined, but pathophysiological roles have been increasingly explored. Endothelial dysfunction is thought to be the key event in the pathogenesis of atherosclerosis. Endothelial dysfunction is a systemic inflammatory process associated with increased adhesion molecule expression, loss of anti-thrombotic factors, increase in vasoconstrictor products and platelet activation.