Figure 1.

MSC-exosome morphology and composition. (A) Transmission electron microscopy (TEM) images of human bone marrow-derived MSC-exosomes (low magnification, 12,000×, scale bar = 500 nm, and high magnification, 30,000×, scale bar = 100 nm) representative TEM images adapted from Ref. (8). (B) MSC-exosomes are surrounded by a phospholipid bilayer and may contain proteins, such as annexins (these are important for transport); tetraspanins such as CD9, CD81, and CD63; and other proteins, such as Alix and TSG101, that are involved in exosomal biogenesis from endosomes. MSC-exosome therapy has shown beneficial effects in numerous preclinical models, demonstrating histological and functional benefits in multiple organs. Abbreviations: FLOT1, flotillin-1; MHC, major histocompatibility complex; TSG101, tumor susceptibility gene 101.