Preeclampsia is a major cause of morbidity and mortality during pregnancy. To date, the pathogenesis of the disease is not fully understood. Recent studies show that preeclampsia is associated with overexpression of hemoglobin genes α2 and γ and accumulation of the protein in the vascular lumen of the placenta. Hypothesizing that cell-free hemoglobin leaks from the placenta into the maternal circulation and contributes to the endothelial damage and symptoms by inducing oxidative stress, we analysed fetal and adult hemoglobin (HbF, HbA), haptoglobin, oxidation markers and the heme scavenger and antioxidant α 1 -microglobulin in plasma, urine and placenta in preeclamptic women (n=28) and normal pregnancies (n=27).The mean plasma concentrations of HbF, HbA, protein carbonyl groups, membrane peroxidation capacity and α 1 -microglobulin were significantly increased in preeclamptic women. The levels of total plasma Hb correlated strongly with the systolic blood pressure.The plasma haptoglobin concentrations of women with preeclampsia were significantly depressed. Increased amounts of α 1 -microglobulin-mRNA and protein were found in placenta from preeclamptic women and the levels of plasma and placenta α 1 -microglobulin correlated to plasma Hb-concentrations. The heme-degrading form t-α 1 -microglobulin was significantly increased in urine in preeclampsia. These results support that hemoglobin-induced oxidative stress is a pathogenic factor in preeclampsia.

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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.

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The underlying mechanisms behind the obstetric condition pre-eclampsia (PE) are still unclear. Manifestation of PE is heterogeneous and it has therefore been proposed to be a syndrome with different causes rather than one disease with a specific aetiology. Recently, we showed differences in circulating angiogenic factors between two subgroups-early- and late-onset PE. To further elucidate the differences between the two, we investigated placental gene expression profiles. Whole genome microarray technology and bioinformatic analysis were used to evaluate gene expression profiles in placentae from early- (24-32 gestational weeks, n = 8) and late-onset (36-41 gestational weeks, n = 7) PE. The results were verified by using quantitative real-time (qRT)-PCR. We found significant differences in the expression of 196 genes in early- compared with late-onset PE, 45 of these genes showing a fold change above 2. Bioinformatic analysis revealed alterations in angiogenesis and regulation of cell motility. Two angiogenesis-associated transcripts (Egfl7 and Acvrl1) showed lower expression in early-onset PE versus late-onset PE (P = 0.037 and P = 0.003) and versus gestational age-matched controls (P = 0.007 and P = 0.011). We conclude that angiogenesis-associated genes are regulated in a different manner in the two subgroups, and that the gene expression profiles of early- and late-onset PE diverge, supporting the hypothesis of early- and late-onset PE being at least partly two separate entities.