Phosphatidylserine/phosphatidylcholine microvesicles can induce preeclampsia-like changes in pregnant mice

We established a phosphatidylserine (PS)/phosphatidylcholine (PC) microvesicles-induced preeclampsia-like model in mice. PS/PC were prepared by mixing 80% PC and 20% PS, and suspended in 0.05 M Tris-HCl at a concentration of 10 mg/mL. One hundred microliters of PS/PC (n = 6) and saline as a control (n = 10) were injected in tail veins of Institute of Cancer Research (ICR) mice every day from days 5.5 to 16.5 of pregnancy. Systolic blood pressure (SBP) was measured by means of the tail-cuff method. On day 17.5, the mice were anesthetized by diethyl ether and euthanized with the collapse of the circulation by drawing blood from the heart. The animals were dissected and the fetuses and placentas removed. Fetal weight and placental weight were evaluated. Plasma antithrombin activity (AT), thrombin-antithrombin complex (TAT), platelet counts, and proteinuria were measured on day 17.5. Placentas were fixed in 4% paraformaldehyde for histologic studies. Statistical analysis was evaluated by analysis of variance and Welch's t-test. Mice injected with PS/PC showed a significant elevation in SBP (124 versus 101 mm Hg; p < 0.001), a significant increase in TAT levels (23 versus 6.6 mug/L; p < 0.05), a significant decrease in platelet counts (88 versus 102 x 10 (10)/L; p < 0.05), a decrease in AT, an increase in proteinuria, and a significant reduction in fetal weight (1.2 versus 1.3 g; p < 0.0001) and placental weight (0.13 versus 0.15 g; p < 0.001), compared with controls. Placentas of mice injected with PS/PC showed diffuse fibrin depositions in the labyrinth layer. We have demonstrated that the artificial PS/PC vesicles induce intrauterine growth restriction with elevations of SBP. The elevation of plasma TAT and the diffuse fibrin depositions in the placentas indicate enhanced thrombin formation, and the significant elevations of SBP indicate preeclampsia-like changes that can be induced by hypercoagulation in the placenta.