Altered methylation and expression patterns of genes regulating placental angiogenesis in preterm pregnancy.

INTRODUCTION: Altered angiogenesis has been implicated in the pathogenesis of various pregnancy complications, particularly preeclampsia. At present, there is a lack of data on the possible role of angiogenesis and its molecular mechanism in preterm pregnancy. We have previously reported reduced placental global DNA methylation levels in preterm pregnancy. Now, we have extended the study to examine plasma levels of angiogenic factors from maternal and cord blood and correlate them with placental promoter CpG methylation and messenger RNA expression of these angiogenic genes in preterm pregnancies. METHODS: We recruited 99 women delivering at term and 90 women delivering preterm. Plasma levels of angiogenic factors, vascular endothelial growth factor (VEGF), placental growth factor (PlGF), fms-related tyrosine kinase 1 (FLT-1), and kinase insert domain receptor (KDR) were analyzed by enzyme-linked immunosorbent assay. Expression levels and promoter CpG methylation of angiogenic genes in placentae were determined by quantitative real-time polymerase chain reaction and by the Sequenom EpiTYPER technology, respectively. RESULTS: Maternal VEGF and PlGF levels (P < .01 for both) were lower but soluble FLT-1 (sFLT-1) levels and sFLT-1-PlGF ratio (P < .05 for both) were higher in the preterm group. Placental VEGF expression (P < .05) was lower, and CpG site 14 in the VEGF promoter was hypermethylated (P < .05) in the preterm group. The KDR expression (P < .05) was higher in women delivering preterm. CONCLUSIONS: Our study provides first evidence of differential placental CpG methylation patterns and expression of VEGF, FLT-1, and KDR genes in women delivering preterm. This may explain the possible mechanism for angiogenic imbalance in the pathophysiology of preterm pregnancy.

Differential placental methylation and expression of VEGF, FLT-1 and KDR genes in human term and preterm preeclampsia.

BACKGROUND: Preeclampsia, a pregnancy complication of placental origin is associated with altered expression of angiogenic factors and their receptors. Recently, there is considerable interest in understanding the role of adverse intrauterine conditions in placental dysfunction and adverse pregnancy outcomes. Since we have observed changes in placental global DNA methylation levels in preeclampsia, this study was undertaken to examine gene promoter CpG methylation and expression of several angiogenic genes.We recruited 139 women comprising, 46 normotensive women with term delivery (≥37 weeks), 45 women with preeclampsia delivering preterm (<37 weeks) and 48 women with preeclampsia delivering at term. Expression levels and promoter CpG methylation of VEGF, FLT-1 and KDR genes in placentae from respective groups were determined by Taqman-based quantitative real time PCR and by the Sequenom® EpiTYPER™ technology respectively. RESULTS: We observed several differentially methylated CpG sites in the promoter regions of VEGF, FLT-1 and KDR between the normotensive and preeclampsia groups. We specifically observed hypomethylated CpGs in the promoter region and an increased expression of VEGF gene between term and preterm preeclampsia. However, mean promoter CpG methylation could not account for the higher expression of FLT-1 and KDR in preterm preeclampsia as compared to normotensive group. CONCLUSIONS: Our data indicates altered DNA methylation patterns in the VEGF, FLT-1 and KDR genes in preeclampsia as compared to the normotensive group, which could be involved in the pathophysiology of preeclampsia. Hypomethylation of VEGF promoter and consequent upregulation of VEGF mRNA levels could be a compensatory mechanism to restore normal angiogenesis and blood flow in preterm preeclampsia. This study suggests a role of altered DNA methylation in placental angiogenesis and in determining adverse pregnancy outcomes.