DISTURBED ASSOCIATION BETWEEN PLACENTAL SODIUM CONTENT AND GLYCOSAMINOGLYCANS IN GESTATIONAL HYPERTENSION BUT NOT IN PRE-ECLAMPSIA

Abstract

Objective: Glycosaminoglycans (GAGs) facilitate tissue sodium accumulation which plays an important role in regulation of sodium homeostasis, water balance and blood pressure. During pregnancy, GAGs are also highly expressed in placental tissue. We studied placental sodium concentration and GAG content from normotensive and hypertensive pregnancies to explore a link between placental sodium and blood pressure during pregnancy. Design and method: We performed a prospective case-control study in singleton pregnancies with normal blood pressure (nBP, n = 22), gestational hypertension (GH, n = 12) and pre-eclampsia (PE, n = 10). Two full thickness placental biopsies (central [near umbilical cord insertion] and peripheral) were collected after delivery for analysis of placental electrolyte concentration (ICP-OES) and GAG content (UPLC-MS/MS). Linear associations were explored with a linear regression analysis with correction for gestational age, mode of delivery and treatment with antihypertensive drugs. Results: Placental sodium concentration in GH was 10.1% (p = 0.01) lower in central and 9.4% (p = 0.04) lower in peripheral biopsies compared to nBP. Total peripheral heparan sulfate (HS) expression was 32.3% lower in GH compared to nBP (p = 0.04). Also, di-sulfated HS as percentage of total HS was lower in peripheral biopsies of GH compared to nBP (11.0% [IQR 10.0-11.4] vs 12.3% [IQR 11.3-14.5], p = 0.02). In PE, placental GAG and sodium content were not significantly different from nBP. Placental sodium concentration was linearly associated with percentage of di-sulfated HS (Fig A), while in central biopsies it was negatively associated with systolic BP (Fig B). Conclusions: We show that GH is accompanied by lower placental sodium content when compared to pregnancies with normal blood pressure. Also, lower placental sodium content during pregnancy is associated with lower placental GAG content and higher BP. This indicates that placental sodium homeostasis might be involved in chronic maternal blood pressure regulation.