Heparin Elevates Circulating Soluble fms-Like Tyrosine Kinase-1 Immunoreactivity in Pregnant Women Receiving Anticoagulation Therapy

Abstract

Background-Alterations in circulating levels of pro-and antiangiogenic factors have been associated with adverse pregnancy outcomes. Heparin is routinely administered to pregnant women, but without clear knowledge of its impact on these factors. Methods and Results-We conducted a longitudinal study of 42 pregnant women. Twenty-one women received prophylactic heparin anticoagulation, and 21 healthy pregnant women served as controls. Compared with gestational age-matched controls, heparin treatment was associated with increased circulating levels of soluble fms-like tyrosine kinase-1 (sFlt-1) in the third trimester (PϽ0.05), in the absence of preeclampsia, placental abruption, or fetal growth restriction. Heparin had no effect on circulating levels of vascular endothelial growth factor, placenta growth factor, or soluble endoglin as assessed by ELISA. In vitro, low-molecular weight and unfractionated heparins stimulated sFlt-1 release from placental villous explants, in a dose-and time-dependent manner. This effect was not due to placental apoptosis, necrosis, alteration in protein secretion, or increased transcription. Western blot analysis demonstrated that heparin induced shedding of the N-terminus of Flt-1 both in vivo and in vitro as indicated by a predominant band of 100 -112 kDa. By using an in vitro angiogenesis assay, we demonstrated that serum of heparin-treated cases inhibited both basal and vascular endothelial growth factor-induced capillary-like tube formation. Conclusions-Heparin likely increases the maternal sFlt-1 through shedding of the extracellular domain of Flt-1 receptor.Our results imply that upregulation of circulating sFlt-1 immunoreactivity in pregnancy is not always associated with adverse outcomes, and that heparin's protective effects, if any, cannot be explained by promotion of angiogenesis. (Circulation. 2011;124:2543-2553.)Key Words: anticoagulation Ⅲ angiogenesis Ⅲ sFlt-1 Ⅲ heparin Ⅲ pregnancy A successful pregnancy outcome requires the proper functioning of the molecular mechanisms responsible for regulating vascular endothelial homeostasis at both the systemic and local decidual/placental levels. 1 Derangements of these mechanisms can lead to major pregnancy-related complications. Recent studies have focused on how alterations in placental trophoblast production of angiogenic proteins may help to explain the pathogenesis of preeclampsia, 2,3 placental abruption, 4 intrauterine growth restriction, and stillbirth. 5 A unifying theory is that excessive release of antiangiogenic factors, such as soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng) by hypoxic trophoblasts, antagonize proangiogenic factors such as vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF). 3 This phenomenon causes aberrant placental angiogenesis and vasculogenesis. 6 The end result is an increasingly dysfunctional placenta with local and systemic vascular endothelial damage, activation of inflammatory pathways, and enhanced platelet turnover, which result in the...

Differential Diagnosis of Preeclampsia

“…Of potential concern is a recent finding by Rosenberg et al 34 showing that heparin treatment during pregnancy is associated with increased sFlt-1 levels. This increase was detectable after the 28th week of pregnancy in women who, for various reasons, were treated with prophylactic or therapeutic doses of mostly LMWH but in whom pregnancy course and outcome were uneventful.…”

The role of anti-phospholipid antibodies in autoimmune reproductive failure

“…In a recent meta-analysis, Ziakas et al concluded that heparin plus LDA is not more effective than LDA alone in treating women with APS-related fetal deaths but at least one of the trials included in that meta-analysis included a mixed population of patients only some of whom had APS (Ziakas et al 2010). Moreover, a number of studies have shown that heparin promotes the placental release of sFlt1 (Carroll et al 2011, Rosenberg et al 2011, an anti-angiogenic factor associated with pre-eclampsia (Maynard et al 2003). However, in vitro studies indicate that vitamin D may reverse this LMWH-induced trophoblast sFlt1 secretion (Gysler et al 2015).…”

Management of Women with Recurrent Pregnancy Losses and Antiphospholipid Antibody Syndrome

“…However, LMWH up-regulated soluble fms-like tyrosine kinase receptor-1 (sFlt-1) secretion independently of aPL through shedding of the extracellular domain of Flt-1 receptor. 66 The complicated effects of heparin may explain why women with RPL, who were treated with heparin to prevent early pregnancy loss, have inconsistent outcome and still remain at increased risk of developing later obstetrical complications such as pre-eclampsia. 67 In a recent clinical trial, heparin treatment was reported to be associated with increased circulating levels of sFlt-1 in the third trimester without increased growth restriction, and serum of heparintreated cases inhibited both basal and vascular endothelial growth factor-induced capillary-like tube formation.…”

“…67 In a recent clinical trial, heparin treatment was reported to be associated with increased circulating levels of sFlt-1 in the third trimester without increased growth restriction, and serum of heparintreated cases inhibited both basal and vascular endothelial growth factor-induced capillary-like tube formation. 66 Therefore, upregulation of circulating sFlt-1 immunoreactivity in pregnancy seems not always to be associated with adverse outcomes and whether heparin has any effect to promote angiogenesis is in question. 66 …”

“…66 Therefore, upregulation of circulating sFlt-1 immunoreactivity in pregnancy seems not always to be associated with adverse outcomes and whether heparin has any effect to promote angiogenesis is in question. 66 …”