BMSC-derived exosomes increase migration of MM cells and home to the BM in vivo. (A) 5T33MMvt or 5T33MMvv cells were incubated with 40 or 80 μg/mL naive or 5T33 BMSC-derived exosomes in transwell system, and transmigrated MM cells were counted using fluorescence-activated cell sorter. The results are presented as the percentage of total MM cells in the transwell system. 5T33MMvt (B) and 5T33MMvv (C) cells pretreated with AMD3100 (50 μM) or CCR2 antagonist (100 nM) for 90 minutes were incubated with 80 μg/mL naive or 5T33 BMSC-derived exosomes in transwell system for another 2 hours. Transmigrated MM cells were counted using fluorescence-activated cell sorter, and the results are presented as percentage of the total MM cells in the transwell system. Mean values ± standard deviation for 3 independent experiments are shown. *P < .05; **P < .01; ***P < .001. (D) Here, 2.5 × 106 DIR-labeled 5T33MMvv cells were intravenously injected into naive mice. At 24 hours after injection, the localization of MM cells was detected using whole-body imaging. The distribution of 5T33MMvv cells in organs was also measured using an imaging system. The fluorescence intensity scale is displayed on the right side of the images. (E) Five hundred micrograms DIR-labeled naive or 5T33 BMSC-derived exosomes were intravenously injected in 5T33 mice for 24 hours. The localization of the exosomes in organs was detected as in C. The fluorescence intensity scale is indicated on the right side of the images. The highest intensity is marked as 100% and indicated by red color, whereas the lowest is indicated by dark blue. Arrows indicate the organs in vivo. Le, Legs; Li, liver, Sc, spinal column; Sp, spleen.
