Fig. 1.

: A schematic showing the biogenesis and release of exosomes (or small extracellular vesicles) from neural stem cells into the extracellular space. First, endosomes (E) are produced through invaginations of the plasma membrane [95]. Endosomes will next generate many intraluminal vesicles or exosomes via the inward invagination of the endosomal membrane [95]. Through the ESCRT-dependent or independent pathways, exosomes are formed and packaged within endosomes using sphingolipids and tetraspanins [30]. Endosomes then either enter the lysosomal (L) route to get digested or fuse with the plasma membrane resulting in the release of exosomes (Ex Release) into the extracellular space [1]. Exosomes comprise a cargo of miRNAs, mRNAs, proteins (P) including TSG101 and Alix, and the membrane markers CD63 and CD81 [82]. The released exosomes may influence the function of neighboring as well as distant cells [27].