One hundred microliters of Magna Bind goat anti-mouse IgG Magnetic Beads (Thermo Fisher Scientific) were washed three times with PBS solution (200 μl) and incubated with 10 μg of mouse monoclonal anti-AGO2 (ab57113, Abcam) or mouse IgG (Santa Cruz Biotechnology) antibodies for 2 hr at 4°C. The pre-incubated beads and antibodies were then added to 200 μL of PF and incubated overnight at 4°C. Beads were washed 3 times with 1% Nonidet P-40 buffer and re-suspended in 200 μL of PBS. One half of each sample was eluted in loading buffer followed by western blot analysis. Protein extracted from HUVECs was used as a positive control. The other half was eluted in 750 μL of QIAzol and processed for RNA isolation and miRNA detection (see above). Exosomes and cells were lysed with RIPA buffer (Santa Cruz Biotechnology) with an added protease inhibitor cocktail. Samples were centrifuged at 14,000 × g for 15 min at 4°C, and the supernatant fractions were used for western blot. Western blot was performed as previously described.46 The following antibodies were used: Alix (Millipore, ABC40; 1:1,000; Merk Millipore), Flotillin-1 (BD, 610820, 1:1,000), EPCAM (Cell Signaling Technology, 2626; 1:1,000), CD63 (Abcam, ab59479; 1:1,000), AGO2 (Abcam, ab57113; 1:1,000), DICER (Abcam, ab14601, 1:500), β-Actin (Sigma, A5441; 1:50,000), ECL Mouse IgG (GE Healthcare, NA931; 1:2,000), and ECL Rabbit IgG (GE Healthcare, NA934; 1:2,000).