Placental Aromatase Is Deficient in Placental Ischemia and Preeclampsia.

Preeclampsia is a maternal hypertensive disorder with uncertain etiology and a leading cause of maternal and fetal mortality worldwide, causing nearly 40% of premature births delivered before 35 weeks of gestation. The first stage of preeclampsia is characterized by reduction of utero-placental blood flow which is reflected in high blood pressure and proteinuria during the second half of pregnancy. In human placenta androgens derived from the maternal and fetal adrenal glands are converted into estrogens by the enzymatic action of placental aromatase. This implies that alterations in placental steroidogenesis and, subsequently, in the functionality or bioavailability of placental aromatase may be mechanistically involved in the pathophysiology of PE.Serum samples were collected at 32-36 weeks of gestation and placenta biopsies were collected at time of delivery from PE patients (n = 16) and pregnant controls (n = 32). The effect of oxygen tension on placental cells was assessed by incubation JEG-3 cells under 1% and 8% O2 for different time periods, Timed-mated, pregnant New Zealand white rabbits (n = 6) were used to establish an in vivo model of placental ischemia (achieved by ligature of uteroplacental vessels). Aromatase content and estrogens and androgens concentrations were measured.The protein and mRNA content of placental aromatase significantly diminished in placentae obtained from preeclamptic patients compared to controls. Similarly, the circulating concentrations of 17-β-estradiol/testosterone and estrone/androstenedione were reduced in preeclamptic patients vs. controls. These data are consistent with a concomitant decrease in aromatase activity. Aromatase content was reduced in response to low oxygen tension in the choriocarcinoma JEG-3 cell line and in rabbit placentae in response to partial ligation of uterine spiral arteries, suggesting that reduced placental aromatase activity in preeclamptic patients may be associated with chronic placental ischemia and hypoxia later in gestation.Placental aromatase expression and functionality are diminished in pregnancies complicated by preeclampsia in comparison with healthy pregnant controls

Aromatase metabolite levels are dysregulated in PE patients.

<p>Aromatase functionality was measured in PE and normotensive pregnancies. The levels of aromatase precursors and metabolites including, <b>A</b>. testosterone, <b>B</b>. androstenedione, <b>C</b>. 17-β-estradiol, and <b>D</b>. estrone were measured by RIA in maternal serum samples collected at 32–36 weeks of gestation. Also shown are <b>E</b>. 17-β-estradiol/testosterone and <b>F</b>. estrone/androstenedione ratios. Data are reported as mean±SEM from 32 controls and 16 PE patients. Statistical analysis was performed using Mann-Whitney test. *<i>P</i>≤0.05; **<i>P</i>≤0.01, significant; n.s., non-significant.</p

Clinical characteristics of controls and preeclampsia patients at different times of gestation.

<p>Values are given as Mean±SEM. Statistical significance was assessed using Mann Whitney test and Fisher's exact test.</p><p>*p≤0.05</p><p>**p≤0.01</p><p>***p≤0.001</p><p>Clinical characteristics of controls and preeclampsia patients at different times of gestation.</p

Aromatase is downregulated in JEG–3 cell line in response to hypoxia.

<p>JEG–3 cell line was exposed either to 8% or to 1% O₂ in an hypoxic chamber for 0, 4, 8, 16 and 24 h. <b>A</b>. Cells were collected at indicated times and protein lysates analyzed by western blot to determine the protein expression levels of aromatase, HIF–1α and β-Tubulin. Upper panel shows representative western blots and lower panels show aromatase and HIF–1α proteins densitometry data normalized to β-Tubulin loading control from n = 3 experiments. Data are shown in arbitrary units (A.U.) ±SEM. <b>B</b>. Cells were collected at indicated times and analyzed by qRT–PCR to determine aromatase mRNA transcript levels. Statistical analyses were performed using Student’s <i>t</i>-test and compared with the correspondent time point in the control, 8% O₂, cells. Columns are the mean of four independent experiments in duplicate; Data are reported as mean±SEM. *<i>P</i>≤0.05; **<i>P</i>≤0.01; *** <i>P</i>≤0.001, significant; n.s., non-significant.</p

Effect of hypoxia on placental aromatase expression <i>in vivo</i>.

<p><b>A</b>. Pups of timed-pregnant rabbits derived either from one uterine horn which placental spiral arteries had been ligated or from the non-ligated placentas on the contralateral horn (control horn, n = 17) were weighted <b>B</b>. and RNA was extracted from the correspondent placentas. Aromatase mRNA levels were analyzed by qRT-PCR in the control (n = 17) and hypoxic horn (n = 10). At least one hypoxic and one no-hypoxic placenta were collected from each of the 6 pregnant rabbits. Data are reported as mean±SEM. Statistical analysis was conducted using Mann-Whitney test. *<i>P</i>≤0.05; **<i>P</i>≤0.01, significant.</p