Figure 7. MSC-derived MVs inhibit TLR signalling in macrophages.
(a) Upper panels, confocal microscopy showing intracellular localization of Cy5-labelled exosomes within macrophages 18 min post administration. Lower panel, nuclear localization of NF-κB in macrophages 2 h post administration of exosomes. Scale bars, 15 μ. (b) Partial heatmap illustrating mRNA levels of 84 TLR-associated transcripts in macrophages at 8 h post treatment with silica (20 mg cm−2), human or mouse MSCs (1:10 ratio) or human MSC-derived exosomes (40 μg protein). Transcript order is highest (top) to lowest (bottom), and each row represents a gene and each column a specific treatment. Red and green illustrates increased or decreased gene expression, respectively. Experiments were repeated four times. (c) Effect of exosome treatment on PGE2, TNF and IL-10 secretion in macrophages from the indicated mouse strains. Plotted data (mean±s.e.m.) were from experiments repeated five times. *P<0.05 compared with C57BL/6J or BALB/CJ macrophages as determined by ANOVA). (d) Upper panel, western blot illustrating the time-dependent effect of silica or human MSC-derived exosomes on expression of TLR7 in macrophages. Lower panel, fold change in expression of the indicated transcripts in macrophages RT–PCR demonstrating the negative regulation of exosomes on macrophage expression of TLR genes. Plotted data (mean±s.e.m.) are from experiments repeated four times. *P<0.05 compared with baseline. #P<0.05 compared with native exosomes by Student’ t-test. †P<0.05 compared with the effect of native exosomes and indomethacin (Indo) treated by Student’s t-test.