Placental expression profiling in preeclampsia: local overproduction of hemoglobin may drive pathological changes

Abstract

Using microarrays made with cDNAs from subtracted placental libraries, we show increased hemoglobin production in the preeclamptic placenta. Heme and hemoglobin may cause endothelial damage and inflammation and drive pathological changes in the placenta if they are released there. Study Objective:To create a library enriched in cDNAs from preeclamptic placentas to print on to microarrays for placental profiling of preeclampsia (PE) and high risk pregnancies. Design: Prospective study.Setting: University women's clinic and academic research laboratory.Patients: Ten patients with PE, 5 with PE and bilateral notching, 5 with bilateral notching without PE, and 15 normotensive patients were recruited.Interventions: Placenta and placenta bed biopsies were collected after delivery. Main Outcome Measures:Subtracted libraries of PE transcripts were produced, and cDNAs from these libraries were used to make PE-specific cDNA arrays. Results were verified quantitatively using real-time PCR and histologically using in situ hybridization and immunohistochemistry.Results: 30 genes were significantly altered in at least one group comparison. Differences in two candidate genes were confirmed using quantitative rt-PCR. Hemoglobin α2 and γ transcripts were significantly over-expressed in the PE placenta. Scattered cells in the placenta and placental blood vessels were shown to express genes encoding these hemoglobin-chains. Conclusions:We demonstrate increased hemoglobin production in the PE placenta. The hemoglobin may be released into the placenta blood vessel lumen. Free heme and hemoglobin are potent toxins which cause endothelial damage and inflammation.

Perfusion of human placenta with hemoglobin introduces preeclampsia-like injuries that are prevented by α1-microglobulin

“…Hb-perfusion, in general, led to a massive up-regulation 23 of genes. The gene ontology-analyses showed that apoptosis-, oxidative stress-, and immune-related genes were frequently represented, confirming data from previously reported findings based on gene array studies on PE placentas [6,[47][48][49].…”

“…1). The PCR reactions were carried out in duplicates including negative controls (without template) in each run as previously described [6]. Gene transcript of the A1M gene was quantified using SYBR green in an iCycler Thermal Cycler (Bio-Rad Laboratories, Hercules, CA, USA) as previously described [20].…”

“…By using gene and protein profiling techniques, we have previously been able to show increased mRNA levels of fetal hemoglobin (HbF) in the placental tissue and evidence of free HbF in the placental vascular lumen in PE [6]. Furthermore, we have shown increased plasma and serum concentrations of HbF in the mother, suggesting that free HbF leaks over the blood-placenta barrier, into the maternal circulation where the plasma concentration is increasing from early pregnancy and later correlates to the severity of the the disease [7,8].…”

Increased levels of cell-free hemoglobin, oxidation markers, and the antioxidative heme scavenger α1-microglobulin in preeclampsia

“…By gene expression microarray technology, it was recently shown that PE is associated with overexpression of the hemoglobin (Hb) subunits α2 and γ in the placenta [4]. Hb, the oxygen-carrying molecule in red blood cells, consists of four globin chains, each binding an iron-containing heme group.…”

Iron, Oxidative Stress and Health

“…HO-1 has antioxidative, anti-inflammatory and anti-apoptotic effects. Centlow et al, (2008) observed that placental tissue from preeclamptic women exhibited increased expression of Hb and Hb mRNA than placentas from normal pregnant women. Increased number of cells expressed Hb in the preeclamptic patients' placentas suggesting that either the cells were migrating into or out of the vessels or there may be binding sites on the vessel walls.…”