“…Thus, exosomes released by neurons, astrocytes, oligodendrocytes, microglia, endothelial cells and pericytes can be differentiated according to antibody-based purification utilizing L1CAM (L1 cell adhesion molecule), GLAST (Glutamate aspartate transporter), PLP1 (Proteolipid protein 1), TMEM119 (Transmembrane protein 119), CD31 (cluster of differentiation 31) and PDGFRβ (platelet-derived growth factor receptor beta), respectively ( Frühbeis et al, 2020 ; Kumar et al, 2020 ). The capacity to identify a given exosome’s parent cell is particularly valuable given that peripheral exosomes can penetrate the blood-brain-barrier (BBB), while brain derived exosomes can be readily detected in systemic samples ( Alvarez-Erviti et al, 2011 ; Banks et al, 2020 ; Kumar et al, 2021 ). It should be noted that a recent investigation suggested L1CAM may not be an appropriate marker to identify neuronal specific exosomes ( Norman et al, 2021 ); however, the interpretation of such data as well as the reliability of these findings remain contested, including contrary evidence of L1CAM positive vesicles enriched for neuronal proteins (e.g., BDNF, neuronal enolase) ( Mustapic et al, 2017 ; Suire et al, 2017 ).…”