Fig. 4: Apoptotic exosome-like vesicle internalization is mediated by a phosphatidylserine-dependent mechanism.

A Disruption of ApoExo membrane integrity inhibits uptake. Quantification of ApoExo uptake by serum-starved endothelial cells treated with 5 mM MβCD or vehicle (water; Ctrl), as determined by flow cytometry. ApoExos were treated with 5 mM MβCD for 1 h and then incubated with serum-starved endothelial cells for 1 h, or serum-starved endothelial cells were pretreated for 1 h with 5 mM MβCD followed by incubation with ApoExos for 1 h without MβCD. n = 4 for each condition. Phosphatidylserine sequestration by ApoExos inhibits their uptake by endothelial cells. Quantification by flow cytometry (B) and confocal microscopy (C) of the uptake of ApoExos pretreated for 1 h with 10 µg/mL annexin V or vehicle (water; Ctrl) and then incubated with serum-starved endothelial cells for 1 h. n = 5 for each condition. Flow cytometry data are expressed as the median fluorescence intensity (MFI) (30,000 events/sample) ± SEM. Confocal microscopy experimental data are expressed as corrected total cell fluorescence (CTCF) ± SEM. Representative pictures of ApoExo internalization by confocal microscopy (Scale bar: 20 µm; red—ApoExo, and blue—nucleus). P values were obtained by unpaired t test (*P < 0.05, **P < 0.01, and ***P < 0.001).