Circulating Platelet-derived and Placenta-derived Microparticles Expose Flt-1 in Preeclampsia

Background. Flt-1 is secreted by various cells and elevated concentrations are present in preeclampsia affecting vascular function. Microparticles from these cells may expose Flt-1. We evaluated whether Flt-1 is microparticle-associated in preeclampsia, and established the origin of Flt-1-exposing microparticles. Methods. The concentration of Flt-1 was measured in samples from preeclamptic patients, pregnant and nonpregnant women by enzyme-linked immunosorbent assay. Microparticles were analyzed by flow cytometry. Western blot determined the different forms of Flt-1. Results. Noncell bound Flt-1 was elevated in preeclampsia compared to controls, A fraction (5%) was associated with microparticles in preeclampsia. Flt-1-exposing microparticles were. increased in preeclampsia compared to normotensive pregnancy (p = 0.02). Full-length Flt-1, was identified in microparticles of platelet and placental origin. Conclusion. Full-length Flt-1 is associated with platelet and placenta-derived microparticles. Possibly, the Presentation of Flt-1 on the membrane of a microparticle might alter its function, particularly if it acts in synergism with other exposed vasoactive molecules.