Antigenic characterization of endothelial cell-derived microparticles and their detection ex vivo.
BACKGROUND
Endothelial activation and dysfunction are associated with several diseases. However, hardly any specific markers are available. Microparticles (MP) from endothelial cells (EC; EMP) were reported in patient groups and healthy individuals. The antibodies used to detect EMP, however, were mainly directed against antigens without EC specificity.


OBJECTIVE
We evaluated the antigens on EC and EMP to establish proper markers for EMP detection.


METHODS
EMP were isolated from supernatants of resting and interleukin (IL)-1alpha activated human umbilical vein EC (HUVEC; n=3; 0-72 h), stained with annexin V and monoclonal antibodies, and analyzed by flow cytometry. Human platelet-MP (PMP), the main MP population in plasma, were prepared in vitro. EMP and PMP were studied in plasma from systemic lupus erythematosus (SLE) patients (n=11) and healthy individuals (n=10).


RESULTS
Platelet-endothelial cell adhesion molecule-1 (PECAM-1), alphanu and beta3 were constitutively exposed on HUVEC, but (almost) absent on EMP (<15% positive for alphanu and beta3), or only exposed on a subpopulation (PECAM-1; 30-60%). Activated HUVEC (>80%) and (subpopulations of) EMP exposed E-selectin and tissue factor. PMP strongly exposed PECAM-1, beta3, and glycoprotein (GP)Ib (CD42b), but not alphanu or E-selectin. GPIb and P-selectin (CD62P) were absent on EMP. Plasma samples contained 0.5% MP staining for E-selectin and/or alphanu. Plasma from one SLE patient contained E-selectin exposing MP (21%), but little alphanu-positive MP.


CONCLUSIONS
EC release EMP in vitro. The antigenic phenotype of EMP released from resting and IL-1alpha-stimulated EC differs among each other as well as from resting and stimulated EC, respectively. E-selectin exposed on IL-1alpha-stimulated EC is a valid marker for EMP detection ex vivo to establish endothelial cell activation.
Abid Hussein
M N
MN
Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, The Netherlands. m.n.abidhussein@amc.uva.nl
Meesters
E W
EW
Osmanovic
N
N
Romijn
F P H Th M
FP
Nieuwland
R
R
Sturk
A
A
D000328:Adult; D000941:Antigens / Q000032:analysis*; D015415:Biomarkers / Q000032:analysis; D016022:Case-Control Studies; D019040:E-Selectin / Q000032:analysis* / Q000276:immunology; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000473:pathology*; D005089:Exocytosis; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D008180:Lupus Erythematosus, Systemic / Q000473:pathology; D008875:Middle Aged; D010316:Particle Size; D014471:Umbilical Veins
D000941:Antigens; D015415:Biomarkers; D019040:E-Selectin; D007375:Interleukin-1