The Expression of Neuropilin-1 in Human Placentas from Normal and Preeclamptic Pregnancies

Preeclampsia (PET) is a hypertensive disorder that affects 2% to 8% of pregnant women. Recent observations support the hypothesis that upregulation of placental anti-angiogenic factors are responsible for the clinical manifestations of the disease. Neuropilin-1 (NP-1) is a transmembrane protein that acts as a coreceptor for vascular endothelial growth factor and as a regulatory protein in the immune system. The aim of the study was to evaluate the expression of NP-1 in PET and normal placentas. Nineteen placental specimens from severe PET pregnancies were compared with 20 placental specimens of women with low-risk pregnancy. All the specimens underwent immunohistochemical staining with anti-human NP-1 antibody. The degree of NP-1 staining was measured both for intensity and extent. Our study demonstrated NP-1 immunoreactivity mainly in the decidual cells, the intermediate trophoblast, and the syncytiotrophoblast, particularly in the areas in the syncytial knots and shed particles. The particles were strongly NP-1 immunoreactive. The expression of NP-1 in the syncytiotrophoblast was lower in placentas of PET compared with control (P = 0.017). Shedding of syncytiotrophoblast particles from placenta to maternal blood occurs in normal pregnancies and is enhanced during PET and contributes to the maternal vascular injury that characterizes PET. Our new observation that shows strong NP-1 immunoreactivity of these particles, and decreased NP1 expression in syncytiotrophoblast of PET placentas in comparison to the control group, may imply a role of NP-1 in PET.