Elevated circulating endothelial membrane microparticles in paroxysmal nocturnal haemoglobinuria

We analysed endothelial cell membrane microparticles (ECMP) in the peripheral blood of patients with paroxysmal nocturnal haemoglobinuria (PNH) (n = 9), aplastic anaemia (AA) (n = 10), sickle cell disease (SCD) (n = 8), and healthy donors (HD) (n = 11). There was no clinically manifested thrombosis in the PNH or AA group, except one cured thrombophlebitis (PNH), while all SCD patients had a history of vaso-occlusive crises. We used three-colour flow cytometry with blood cell-specific antibodies and antibodies to endothelial antigens CD105 and CD144. Phosphatidylserine-positive microparticles were detected using the annexin V-binding (AVB) assay. The population of CD105+AVB+ ECMP was significantly (P < 0.05) higher in SCD (median: 0.568 x 10(9)/l; 25-75th percentile range: 0.351-0.976 x 10(9)/l) and PNH (0.401 x 10(9)/l ; 0.19-0.441 x 10(9)/l) patients when compared with AA (0.122 x 10(9)/l; 0.061-0.172 x 10(9)/l) or HD (0.180 x 10(9)/l; 0.137-0.217 x 10(9)/l) group. Even more pronounced differences were observed in ECMP exhibiting a marker of inflammatory stimulation CD54 (CD105+CD54+). Similarly, ECMP that exhibited endothelial specific and proteolysis-sensitive antigen CD144 were increased in SCD and PNH, but not in AA. Elevated CD54+ ECMP may reflect the inflammatory status of endothelial cells in SCD and PNH, while CD144+ ECMP could indicate continuous endothelial stimulation and/or injury. Analysis of circulating ECMP appears promising to provide useful information on the status of the vascular endothelium in PNH and SCD.