Exosome mediate communication between BMSCs and MM cells. (A) Transmission electron microscopy images of exosomes derived from BMSCs and 5T33MMvt cells. The scale bars indicate 100 nm, and the arrows indicate the typical exosomes. (B) Size distributions of BMSC- and MM cell-derived exosomes were identified using the NTA. (C) Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel after separation of total lysates from naive BMSC, 5T33 BMSC-derived, and 5T33MMvt cell-derived exosomes. Arrows indicate different protein bands between naive and 5T33 BMSC-derived exosomes. (D) Exosomal positive markers Hsp90, Hsp70, CD63, and flotillin-1 were detected in naive, 5T33 BMSC-derived, and 5T33MMvt cell-derived exosomes using western blot, whereas negative marker calreticulin was not. (E) DID-labeled 5T33MMvt cells (red) were incubated with DIO-labeled naive or 5T33 BMSC-derived exosomes (100 μg/mL, green) for 2 hours, and the exosome uptake by MM cells was detected (original magnification, ×740). Arrows indicate the fusion of the membrane. (F) DID-labeled naive or 5T33 BMSCs (red) were incubated with DIO-labeled 5T33MMvt exosomes (100 μg/mL, green) for 2 hours, and the exosome uptake by BMSCs was detected (original magnification, ×740). Arrows indicate the fusions of the membrane. (G) Cytokines in BMSC-derived and 5T33MMvt cell-derived exosomes were analyzed using a mouse cytokine array. (H) The pixel densities of proteins in cytokine array were quantified and presented as the fold of reference.