Fetal hemoglobin and α1-microglobulin as first- and early second-trimester predictive biomarkers for preeclampsia.

OBJECTIVE: The aim of this study was to evaluate fetal hemoglobin (HbF) and α(1)-microglobulin (A1M) in maternal serum as first-trimester biomarkers for preeclampsia (PE). STUDY DESIGN: The design was a case-control study. We included 96 patients in the first trimester of pregnancy (60 with PE and 36 controls). Venous serum samples were analyzed for HbF and total hemoglobin (Hb) by enzyme-linked immunosorbent assay and for A1M by radioimmunoassay. Sensitivity and specificity was calculated by logistic regression and receiver operating characteristic curve analysis. RESULTS: The HbF/Hb ratio and A1M concentration were significantly elevated in serum from women with subsequent development of PE (P < .0001). The optimal sensitivity and specificity was obtained using the biomarkers in combination; 69% sensitivity for a 5% screen positive rate and 90% sensitivity for a 23% screen positive rate. CONCLUSION: The study suggests that HbF/Hb ratio in combination with A1M is predictive biomarkers for PE.

Tissue proteome profiling of preeclamptic placenta using recombinant antibody microarrays.

PURPOSE: preeclampsia (PE) is a severe, multi-system pregnancy disorder of yet unknown cause, missing means of treatment, and our fundamental understanding of the disease is still impaired. The purpose of this discovery study was to define candidate placenta tissue protein biomarker signatures to further decipher the molecular features of PE. EXPERIMENTAL DESIGN: we used recombinant antibody microarrays for multiplexed protein expression profiling of preeclamptic placenta tissue (n=25) versus normal placenta (n=11) targeting mainly immunoregulatory water-soluble proteins and membrane proteins. Furthermore, the three known subgroups of PE were profiled, including women with early onset preeclampsia and late onset preeclampsia, as well as women with PE and bilateral notching and intrauterine growth restrictions. RESULTS: the data showed that the first generation of candidate PE-associated placenta tissue protein signatures were delineated, indicating that PE (receiver operating characteristics (ROC) AUC value of 0.83) and the subgroups thereof (ROC AUC values ≤ 0.91) could be distinguished. Notably, the data implied that all subgroups, but preeclampsia with bilateral notching and IUGR, could be further classified into novel subsets (ROC AUC values of 1.0) displaying different inflammatory signatures. CONCLUSIONS AND CLINICAL RELEVANCE: we have taken one step further toward de-convoluting the complex features of PE at the molecular level using affinity proteomics.

Increased levels of cell-free hemoglobin, oxidation markers, and the antioxidative heme scavenger alpha(1)-microglobulin in preeclampsia.

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 the hemoglobin genes alpha2 and gamma 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 analyzed fetal and adult hemoglobin (HbF, HbA), haptoglobin, oxidation markers, and the heme scavenger and antioxidant alpha(1)-microglobulin in plasma, urine, and placenta in preeclamptic women (n=28) and women with normal pregnancy (n=27). The mean plasma concentrations of HbF, HbA, protein carbonyl groups, membrane peroxidation capacity, and alpha(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 alpha(1)-microglobulin mRNA and protein were found in placenta from preeclamptic women, and the levels of plasma and placenta alpha(1)-microglobulin correlated with the plasma Hb concentrations. The heme-degrading form t-alpha(1)-microglobulin was significantly increased in urine in preeclampsia. These results support the idea that hemoglobin-induced oxidative stress is a pathogenic factor in preeclampsia.

Differential proteome analysis of the preeclamptic placenta using optimized protein extraction.

The human placenta is a difficult tissue to work with using proteomic technology since it contains large amounts of lipids and glycogen. Both lipids and glycogen are known to interfere with the first step in the two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), the isoelectric focusing. In order to gain the best possible protein separation on 2D-PAGE, an optimized sample preparation protocol for placental proteins was developed. Two different buffers, urea/CHAPS and Hepes, were used for solubilization in combination with six different precipitation methods. The removal of glycogen from the samples by centrifugation was crucial for the final proteome maps. Solubilization with urea/CHAPS in combination with dichloromethane/methanol or acidified acetone proved to be the best precipitation procedures. When applied to clinical placenta samples apolipoprotein A1 was found to be accumulated in the preeclamptic placenta, where it may either have a nutritional effect or act as a modifier of signal transduction.

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

OBJECTIVE: To create a library enriched in cDNAs from preeclamptic placentas to print onto microarrays for placental profiling of preeclampsia (PE) and high risk pregnancies. DESIGN: Prospective study. SETTING: University women's clinic and academic research laboratory. PATIENT(S): Ten patients with PE, 5 with PE and bilateral notching, 5 with bilateral notching without PE, and 15 normotensive patients were recruited. INTERVENTION(S): Placenta and placenta bed biopsies were collected after delivery. MAIN OUTCOME MEASURE(S): 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 polymerase chain reaction (PCR) and histologically using in situ hybridization and immunohistochemistry. RESULT(S): Thirty genes were significantly altered in at least one group comparison. Differences in two candidate genes were confirmed using quantitative real-time PCR. Hemoglobin alpha2 and gamma transcripts were significantly overexpressed in the PE placenta. Scattered cells in the placenta and placental blood vessels were shown to express genes encoding these hemoglobin chains. CONCLUSION(S): 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 that cause endothelial damage and inflammation.