Low Soluble Syndecan-1 Precedes Preeclampsia

INTRODUCTION: Syndecan-1 (Sdc1; CD138) is a major transmembrane heparan sulfate proteoglycan expressed on the extracellular, luminal surface of epithelial cells and syncytiotrophoblast, thus comprising a major component of the glycocalyx of these cells. The “soluble” (shed) form of Sdc1 has paracrine and autocrine functions and is normally produced in a regulated fashion. We compared plasma soluble Sdc1 concentrations, in relation to placental Sdc1 expression, in uncomplicated (control) and preeclamptic pregnancies. METHODS: We evaluated soluble Sdc1 across uncomplicated pregnancy, and between preeclamptic, gestational hypertensive and control patients at mid-pregnancy (20 weeks) and 3(rd) trimester by ELISA. Placental expression level of Sdc1 was compared between groups in relation to pre-delivery plasma soluble Sdc1. Participants were recruited from Magee-Womens Hospital. RESULTS: In uncomplicated pregnancy, plasma soluble Sdc1 rose significantly in the 1(st) trimester, and reached an approximate 50-fold increase at term compared to post pregnancy levels. Soluble Sdc1 was lower at mid-pregnancy in women who later developed preeclampsia (P<0.05), but not gestational hypertension, compared to controls, and remained lower at late pregnancy in preeclampsia (P<0.01) compared to controls. Sdc1 was prominently expressed on syncytiotrophoblast of microvilli. Syncytiotrophoblast Sdc1 immunostaining intensities, and mRNA content in villous homogenates, were lower in preeclampsia vs. controls (P<0.05). Soluble Sdc1 and Sdc1 immunostaining scores were inversely associated with systolic blood pressures, and positively correlated with infant birth weight percentile. CONCLUSION: Soluble Sdc1 is significantly lower before the clinical onset of preeclampsia, with reduced expression of Sdc1 in the delivered placenta, suggesting a role for glycocalyx disturbance in preeclampsia pathophysiology.