Exosomes are nanovesicles secreted into the extracellular environment upon internal vesicle fusion with the plasma membrane. The molecular content of exosomes is a fingerprint of the releasing cell type and of its status. For this reason, and because they are released in easily accessible body fluids such as blood and urine, they represent a precious biomedical tool. A growing body of evidence suggests that exosomes may be used as biomarkers for the diagnosis and prognosis of malignant tumors. This article focuses on the exploitation of exosomes as diagnostic tools for human tumors and discusses possible applications of the same strategies to other pathologies, such as neurodegenerative diseases.

Chondroitin sulphate proteoglycans (CSPGs) are up-regulated in the CNS after injury and inhibit axon regeneration mainly through their glycosaminoglycan (CS-GAG) chains. We have analysed the mRNA levels of the CS-GAG synthesizing enzymes and measured the CS-GAG disaccharide composition by chromatography and immunocytochemistry. Chondroitin 6-sulfotransferase 1 (C6ST1) is up-regulated in most glial types around cortical injuries, and its sulphated product CS-C is also selectively up-regulated. Treatment with TGFalpha and TGFbeta, which are released after brain injury, promotes the expression of C6ST1 and the synthesis of 6-sulphated CS-GAGs in primary astrocytes. Oligodendrocytes, oligodendrocyte precursors and meningeal cells are all inhibitory to axon regeneration, and all express high levels of CS-GAG, including high levels of 6-sulphated GAG. In axon growth-inhibitory Neu7 astrocytes C6ST1 and 6-sulphated GAGs are expressed at high levels, whereas in permissive A7 astrocytes they are not detectable. These results suggest that the up-regulation of CSPG after CNS injury is associated with a specific sulphation pattern on CS-GAGs, mediating the inhibitory properties of proteoglycans on axonal regeneration.

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