PS-BPB04-7: PRO-ANGIOGENIC EFFECTS OF LSKL, A THROMBOSPONDIN-1 INHIBITOR, IN HUMAN AND EXPERIMENTAL MODELS OF PREECLAMPSIA

Abstract

Introduction: Preeclampsia (PE) is a hypertensive disorder of pregnancy characterized by blood pressure above 140/90 mmHg. It accounts for 10% of all pregnancies and is responsible for 25% of preterm births and low birth weight. To date, no medications can treat or prevent PE. We identified an activation of the anti-angiogenic protein thrombospondin-1 (THBS1) in human and experimental preeclampsia. THBS1 is also a main activator of TGF-β. We postulate that THBS1-mediated TGF-β activation may contribute to impair placental angiogenesis during PE. Objective: We aimed to test the effects of LSKL, an inhibitor of THBS1-mediated TGF-β activation, on angiogenesis in placentas of a mouse model of PE and in human placental endothelial cells. Methods: Peptide LSKL or its control peptide SLLK (280 μM in 0.5 ml saline, s.c.) was administered at gestational day (GD) 14.5 in heterozygous transgenic mice overexpressing human renin and human angiotensinogen and controls (C57BL/6). Placentas (n = 12/group) were removed at GD 18.5. Protein expression of TGF-β1, TGF-β2, total and phosphorylated SMAD2 were assessed by western blot of placental lysates. Placental angiogenesis was assessed by CD31+ immunohistochemistry in placental sections. CD31+ endothelial cells were extracted by magnetic sorting from human placentas (n = 4) of healthy pregnancies. Cells (2–5 passages) were treated with LSKL or SLLK (30 μM) under hypoxia (0.5% vs. 8% O2) or thrombin (10 u/mL) exposure (4 hours). THBS1 expression in placental endothelial cells was assessed by immunofluorescence. Cell angiogenesis was quantified by the number of closed tubes formed on matrigel (per 15,000 cells, 4 hours). Results: Maternal LSKL treatment significantly reduced the expression of TGF-β2 (P < 0.01) and SMAD2 phosphorylation (P < 0.05) while improving angiogenesis (P < 0.05) in placentas of transgenic preeclamptic mouse compared to controls. In human placental endothelial cells, both thrombin (P < 0.05) and hypoxia (P < 0.05) significantly increased THBS1 expression. Thrombin (P < 0.01) and hypoxia (P < 0.05) significantly impaired cell angiogenesis on matrigel (P < 0.01), which was prevented by LSKL treatment (P < 0.01). In human cells, LSKL similarly reduced TGB-β2 (p < 0.05) and phospho-SMAD2 (P < 0.05) expressions under thrombin and hypoxia cell exposure. Conclusion: Our results describe a significant pro-angiogenic effect of LSKL treatment by regulating THBS1 and TGF-β2 mechanisms in human and experimental models of PE.