Exosomes as a Future Diagnostic Tool for Brain Disorders

The brain is a highly complex interconnected neuronal network with a specialized blood–brain barrier (BBB). The BBB is a diffusion barrier crucial for protecting normal brain function by blocking dangerous compounds from crossing the bloodstream to the brain; only small molecules can cross the BBB. However, brain diseases, such as Alzheimer’s disease, Parkinson’s disease, seizures, multiple sclerosis, stroke, and brain cancers, are some of the most dominant, traumatic, and nevertheless poorly treated diseases. The development of drug delivery systems for brain disorders has had the poorest achievement rates as compared to other therapeutic areas. Exosomes are extracellular nanovesicles consisting of proteins, messenger RNAs, and microRNAs. They are the most prominent mediators of intercellular communication, regulating, instructing, and re-educating their surrounding environment as well as targeting different organs through their surface modifications. Exosomes are secreted by blood cells and endothelial cells directly into the blood circulation in response to CNS pathological conditions. Secreted exosomes express their markers and offer to track their cellular origin, in addition to making them useful for diagnostic purposes and disease treatments. In this book chapter, we have focused on the biogenesis of exosomes along with their functions and contribution to the treatment of brain disorders. We end this chapter with an account of diagnostic tools and their future prospects with respect to diseases associated with the central nervous system.