Placental Dysfunction in Preeclampsia:Regulation of the Angiogenic Balance by the Hypoxia-Inducible Factor-2α

Details

Supervisors

Colson, Arthur ; Debiève, Frédéric

Faculty

Faculté de pharmacie et des sciences biomédicales

Degree label

Master [120] en sciences biomédicales, à finalité approfondie

Abstract

Background: Preeclampsia is a major hypertensive disorder of pregnancy that increases maternal/fetal morbidity and mortality worldwide. This complication is mainly due to a persisting low-oxygen tension in the placenta throughout the gestation. Recent evidence from our group demonstrated that low-oxygen tension inhibits trophoblast differentiation and impairs the placental growth factor (PGF) bioavailability through hypoxia-inducible factor (HIF)-2α signaling. However, the detailed signaling pathway involved is not yet fully understood. Objectives: To elucidate the molecular mechanisms by which HIF-2α inhibits PGF secretion and induces that of its soluble receptor sFLT-1. Materials and Methods: The expression of several transcription factors or microRNAs was studied in primary cytotrophoblasts isolated from human placentas at term and cultured under 2.5% O2 (hypoxia) or infected with an adenoviral vector encoding a stabilized form of HIF-2α. In parallel, overexpression experiments were conducted in the BeWo trophoblastic cell line. The expression of the different elements of the pathway was studied by qPCR, Western blot, or ELISA. The regulation of PGF and FLT-1 promoters were also studied by site-directed mutations and dual-luciferase assay. Results: Using our adenoviral vector, we confirmed that the inhibition of PGF expression under hypoxia was mediated by HIF-2α. Upstream of PGF, the inhibition of GCM1 expression by HIF-2α was also demonstrated. Indeed, mutating GCM1 binding sites in the PGF promoter resulted in almost complete inhibition of its activity. Less clearly, the inhibition of GCM1 expression by HIF-2α appears to be mediated by the inhibition of TWIST1 expression. In BeWo cells, overexpression of TWIST1 restored PGF promoter activity as well as native gene expression. Finally, we found that miR-210-3p expression is induced by hypoxia and is involved in the regulation of PGF, but independently of TWIST1 and GCM1. Finally, our results revealed that HIF-2α increased sFLT-1 expression, probably through a posttranscriptional mechanism. Conclusion: We partially characterized the molecular regulation of PGF and sFLT-1 expression by HIF-2α. In addition to improving our knowledge of placental development, this study brings new insights into placental dysfunction and identifies new therapeutic targets for preeclampsia.