Placental melatonin system is present throughout pregnancy and regulates villous trophoblast differentiation.

Melatonin is highly produced in the placenta where it protects against molecular damage and cellular dysfunction arising from hypoxia/re-oxygenation-induced oxidative stress as observed in primary cultures of syncytiotrophoblast. However, little is known about melatonin and its receptors in the human placenta throughout pregnancy and their role in villous trophoblast development. The purpose of this study was to determine melatonin-synthesizing enzymes, arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole O-methyltransferase (HIOMT), and melatonin receptors (MT1 and MT2) expression throughout pregnancy as well as the role of melatonin and its receptors in villous trophoblast syncytialization. Our data show that the melatonin generating system is expressed throughout pregnancy (from week 7 to term) in placental tissues. AANAT and HIOMT show maximal expression at the 3rd trimester of pregnancy. MT1 receptor expression is maximal at the 1st trimester compared to the 2nd and 3rd trimesters, while MT2 receptor expression does not change significantly during pregnancy. Moreover, during primary villous cytotrophoblast syncytialization, MT1 receptor expression increases, while MT2 receptor expression decreases. Treatment of primary villous cytotrophoblast with an increasing concentration of melatonin (10 pM-1 mM) increases the fusion index (syncytium formation; 21% augmentation at 1 mM melatonin vs. vehicle) and ß-hCG secretion (121% augmentation at 1 mM melatonin vs. vehicle). This effect of melatonin appears to be mediated via its MT1 and MT2 receptors. In sum, melatonin machinery (synthetizing enzymes and receptors) is expressed in human placenta throughout pregnancy and promotes syncytium formation, suggesting an essential role of this indolamine in placental function and pregnancy well-being.

Novel role of the renin-angiotensin system in preeclampsia superimposed on chronic hypertension and the effects of exercise in a mouse model.

Gestational hypertensive disorders, such as preeclampsia, affect 6% to 8% of all pregnancies in North America, and they are the leading cause of maternal mortality in industrialized countries, accounting for 16% of deaths. Women with hypertension have an increased risk (15% to 25%) of developing preeclampsia. Our aim was to investigate the mechanisms implicated in preeclampsia superimposed on chronic hypertension and in the protective effects of exercise in a mouse model. Female mice overexpressing human angiotensinogen and human renin were used as a model of preeclampsia superimposed on chronic hypertension. In the trained group, mothers were placed in cages with access to a wheel before mating, and they remained within these throughout gestation. Blood pressure was measured by telemetry. We found that angiotensin II type I receptor was increased, whereas the Mas receptor was decreased in the placenta and the aorta of pregnant sedentary transgenic mice. This would produce a decrease in angiotensin-(1-7) effects in favor of angiotensin II. Supporting the functional contribution of this modulation, we found that the prevention of most pathological features in trained transgenic mice was associated with a normalization of placental angiotensin II type 1 and Mas receptors and an increase in aortic Mas receptor. We also found reduced circulating and placental soluble Fms-like tyrosine kinase-1 in trained transgenic mice compared with sedentary mice. This study demonstrates that modulation of the renin-angiotensin system is a key mechanism in the development of preeclampsia superimposed on chronic hypertension, which can be altered by exercise training to prevent disease features in an animal model.

Melatonin: the watchdog of villous trophoblast homeostasis against hypoxia/reoxygenation-induced oxidative stress and apoptosis.

Human placenta produces melatonin and expresses its receptors. We propose that melatonin, an antioxidant, protects the human placenta against hypoxia/reoxygenation (H/R)-induced damage. Primary term villous cytotrophoblasts were cultured under normoxia (8% O2) with or without 1mM melatonin for 72h to induce differentiation into the syncytiotrophoblast. The cells were then cultured for an additional 22h under normoxia or subjected to hypoxia (0.5% O2) for 4h followed by 18h reoxygenation (8% O2) with or without melatonin. H/R induced oxidative stress, which activated the Bax/Bcl-2 mitochondrial apoptosis pathway and the downstream fragmentation of DNA. Villous trophoblast treatment with melatonin reversed all the negative effects induced by H/R to normoxic levels. This study shows that melatonin protects the villous trophoblast against H/R-induced oxidative stress and apoptosis and suggests a potential preventive and therapeutic use of this indolamine in pregnancy complications characterized by syncytiotrophoblast survival alteration.

Quantitative PCR pitfalls: the case of the human placenta.

Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) is a rapid and high throughput gene expression quantification technology. In order to obtain accurate results, several key experimental design and standardization steps must be rigorously followed as previously described in the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines. This study investigates the effect of reference gene normalization and the impact of RNA degradation on gene expression of 8-oxoguanine DNA glycosylase in human placenta from pregnancies complicated by preeclampsia and gestational diabetes mellitus and their gestation-matched controls. The data presented here show how RNA quality and appropriate reference gene selection is not only important to obtain accurate and reproducible RT-qPCR data but how different and even opposite results can be reported if the key steps outlined in the MIQE guidelines are not followed. The procedures and associated results presented in this study provide the first practical application of the MIQE guidelines to placental analysis in normal and pathological pregnancies.

Melatonin: the smart killer: the human trophoblast as a model.

Melatonin has both the ability to induce intrinsic apoptosis in tumor cells while it inhibits it in non-tumor cells. Melatonin kills tumor cells through induction of reactive oxygen species generation and activation of pro-apoptotic pathways. In contrast, melatonin promotes the survival of non-tumor cells due to its antioxidant properties and the inhibition of pro-apoptotic pathways. In primary human villous trophoblast, a known pseudo-tumorigenic tissue, melatonin promotes the survival through inhibition of the Bax/Bcl-2 pathway while in BeWo choriocarcinoma cell line melatonin induces permeabilization of the mitochondrial membrane leading to cellular death. These findings suggest that the trophoblast is a good model to study the differential effects of melatonin on the intrinsic apoptosis pathway. This review describes the differential effects of melatonin on the intrinsic apoptosis pathway in tumor and non-tumor cells and presents the trophoblast as a novel model system in which to study these effects of melatonin.

Exercise training can attenuate preeclampsia-like features in an animal model.

OBJECTIVE: Exercise training benefits have been widely investigated and used as alternative treatment for different pathological conditions. Since preeclampsia is a severe pregnancy-associated disease for which no treatment is available, our aim was to investigate the protective role of exercise training on pregnancy outcome using a mouse model of the disease. METHODS: We used transgenic female mice overexpressing human angiotensinogen, which develop preeclampsia when mated with human renin-overexpressing males. Females were placed in exercise cages 4 weeks prior to mating, and remained in these throughout gestation. Blood pressure was measured by telemetry, and proteinuria was quantified by ELISA. Placentas were assessed by histology and immunohistochemistry, whereas vascular endothelial growth factor was measured by real-time PCR and immunoblot. Endothelial function was assessed in isolated mesenteric arteries. RESULTS: Conversely to sedentary transgenic females (131.20 ± 4.08 mmHg), trained dam's mean arterial pressure was no longer different from normal mice at the end of gestation (117.5 ± 10.6 vs. 112.3 ± 5.5 mmHg). Proteinuria observed in transgenic dams (3.364 ± 1.62 µg/mg) was absent in trained mice (0.894 ± 0.43 µg/mg). Placental disease and cardiac hypertrophy were also normalized, whereas vascular reactivity was significantly ameliorated. Furthermore, placental vascular endothelial growth factor was normalized in trained transgenic mice. CONCLUSIONS: To our knowledge, we are the first to clearly demonstrate that exercise training both before and during gestation can reduce preeclampsia features in a mouse model. Consequently, women at risk for this disease could benefit from exercise training to protect themselves and their future fetuses.