Figure 5. MiR-199a-3p eliminated the spread of senescence among cardiomyocytes. (A) Representative electron micrograph of isolated exosomes. Scale bar: 100 nm. (B) Size of exosomes measured using a Zetasizer Nano ZS instrument. (C) Protein levels of CD63 and CD81, two exosome markers. (D) DiI-labeled exosomes (red) were internalized into DAPI-labeled cardiomyocytes (blue). Scale bar, 20 μm. (E) Cellular proliferation was measured using the CCK-8 assay. (F) Representative images of SA-β-gal staining (senescent cells are stained green). Scale bars, 20 μm. (G) The percentage of senescent cells was calculated. (H) SASP factor protein levels quantified by Luminex of the medium. The medium was collected from cells as follows: treated with exosome, exosomeDox, exosomeDox+miR-199a-3p mimic, and exosomeDox+miR-NC mimic. The untreated cardiomyocytes were used as control. *P < 0.05 versus control; ▲P < 0.05 versus exosome; #P < 0.05 versus exosomeDox+ miR-199a-3p mimic in repeated-measures ANOVA, n = 6 per group.