Platelet MPs and endothelial characteristics. (A) Platelet MPs were generated by activating platelets with thrombin, labeled with a fluorescence-conjugated lectin (MP D/R), and incubated with the monocytic THP-1 cell line. An uptake of labeled platelet MPs by THP-1 cells was observed within 1 to 2 hours. (B) THP-1 cells bound UEA-1 after coincubation with intact platelets or platelet MPs. PLT denotes platelets; arrows depict platelets among THP-1 cells. After incubation with platelet MPs for 2 days, THP-1 cells stained positive for CD31 (C) and VWF (D), but also for integrin αIIb (CD41) confirming that platelet MPs can be responsible for the markers used to prove the “endothelial” potential of EPCs. Scale bar represents 25 μm.