Placental Release of Distinct DNA-associated Micro-particles into Maternal Circulation: Reflective of Gestation Time and Preeclampsia

Background: The aim of this study was to determine whether DNA-associated micro-particles (MPs) in maternal plasma express fetal-derived human leukocyte antigen-G (HLA-G) or placental alkaline phosphatase (PLAP) and whether the levels differ between women with normotensive pregnancies and preeclampsia. Methods: DNA-associated MPs expressing HLA-G or PLAP were examined in the plasma of normal pregnant women and preeclamptic patients using flow cytometric analysis. Results: DNA-associated HLA-G⁺ MPs were significantly increased in maternal plasma compared to plasma from non-pregnant controls (p < 0.005), with highest levels found in the first and second trimesters. DNA-associated PLAP⁺ MPs were also increased in maternal plasma compared to plasma from non-pregnant controls (p < 0.006), with highest levels in the second and third trimesters. Term preeclamptic women had higher levels of DNA-associated MPs than control pregnant women. HLA-G⁺ MPs from the plasma of preeclamptic women had more DNA per MP than HLA-G⁺ MPs from the plasma of normal pregnant women (p < 0.03). Conclusions: HLA-G⁺ and PLAP⁺ MPs increase in maternal circulation at different times during gestation. DNA amounts per HLA-G⁺ MP increase in preeclamptic women which might indicate dysfunctional extravillous cytotrophoblasts.