Apoptosis in human term placenta is not increased during labor but can be massively induced in vitro

The role of apoptosis in the complex pathogenesis of the most common obstetrics and gynaecology diseases

Purpose

We aimed to assess the etiological role of apoptotic genes Bcl-2 and Bax in the background of major obstetric and gynaecological diseases.

Methods

Placental tissue samples were collected from 101 pregnancies with intrauterine growth restriction and 104 pregnancies with premature birth with 140 controll samples from term, eutrophic newborns. In addition, gene expression assessment of the genes Bax and Bcl-2 was performed in 101 uterine leiomyoma tissue samples at our disposal with 110 control cases. Gene expression levels were assessed by PCR method.

Results

The expression of the Bcl-2 gene was decreased in placental samples with intrauterine growth restriction. Significant overexpression of the proapoptotic Bax gene was detected in samples from premature infants. Antiapoptotic Bcl-2 gene expression was found to be significantly increased in fibroid tissues.

Conclusion

Apoptosis plays a crucial role in the development of the most common OB/GYN conditions. Decrease in the placental expression of the antiapoptotic gene Bcl-2 may upset the balance of programmed cell death.

Gene expression patterns of the Bcl-2 and Bax genes in preterm birth

OBJECTIVE

The apoptotic genes Bax and Bcl-2 are both involved in the pathogenesis of preterm delivery in conjunction with additional factors. We characterized gene expression patterns of these apoptotic regulatory genes as well as relevant environmental factors.

DESIGN

A gene expression study with evaluation of clinical data.

SETTING

Semmelweis University, Budapest, Hungary.

SAMPLE

Human placental samples from 104 preterm and 140 full-term pregnancies.

METHODS

Gene tests were performed using real-time PCR to assess gene expression patterns of Bax and Bcl-2 in human placental samples. Clinical data were collected from our computerized database.

MAIN OUTCOME MEASURES

Apoptotic gene expression pattern and clinical information against the background of preterm delivery.

RESULTS

In placental samples from preterm delivery pregnancies, expression of the Bcl-2 gene was unchanged, whereas the Bax gene was overexpressed. Placental gene expression of Bax in preterm delivery was dependent on gestational age with gestational weeks 28-32 and 32-36 associated with overexpression, and no overexpression in gestational weeks 24-28. Preterm delivery began with premature rupture of membranes in 70.2% and spontaneous uterine activity in 29.8%.

CONCLUSIONS

The Bax gene was overexpressed in preterm delivery, whereas expression of the Bcl-2 gene remained unchanged. After the 28(th) gestational week, apoptosis appears to be a key factor in the pathogenesis of preterm delivery.

Regulatory mechanisms for apoptosis in placental tissue during normal pregnancy and gestosis-complicated pregnancy

The localization of apoptosis and expression of proapoptotic and antiapoptotic factors by the placental tissue were compared during normal pregnancy and gestosis-complicated pregnancy. The degree of apoptosis did not differ in the third trimester of normal pregnancy and gestosis-complicated pregnancy. Increased expression of Fas, caspase-8, and caspase-3 in placental tissue during normal pregnancy was shown to contribute to the suppression of angiogenesis and growth of placental tissue. No differences were found in the expression of FasL (CD95L), caspase-2, caspase-9, and Mcl-1 by placental cells during normal pregnancy and gestosis-complicated pregnancy. Increased expression of TRAIL by trophoblast cells is a protective mechanism from apoptotic signals of maternal cytotoxic lymphocytes and NK cells during gestosis.

Bcl-2 and Bax expressions in pre-term, term and post-term placentas

PROBLEM

Placental apoptosis-associated protein imbalance might contribute to the pathogenesis of pre- and post-term birth. Therefore, we evaluated the expression and distribution of pro-apoptotic (Bax) and anti-apoptotic (Bcl-2) molecules in term, pre-term and post-term placentas.

METHOD OF STUDY

Placental samples were collected from women with term (n = 25), pre-term (n = 7) and post-term (n = 10) deliveries. The expression of Bcl-2 and Bax was assessed by immunochemistry on paraffin-embedded placental specimens.

RESULTS

The pattern of immunostaining for Bcl-2 and Bax was the same in all samples, but not the intensity. The Bax/Bcl-2 ratio was higher in both pre-term and post-term placental samples compared with term placentas as a result of intense reactivity for the pro-apoptotic factor, Bax in pre-term and post-term placentas and, for Bcl-2 decrease in pre-term placentas.

CONCLUSION

These findings suggest that different unbalance mechanisms in placental apoptotic-associated protein expressions may be involved in the physiopathology of pre-term and post-term births.

The expression of apoptosis related genes in the first trimester human placenta using a short term in vitro model

Using in vitro model for studying the induction and inhibition of spontaneous apoptosis in human first trimester placental villi, mediated by the free radical scavenger SOD, we have examined the expression of bcl-xL, bax, Caspase-3 and PARP (Poly ADP-ribosyl). An increase in apoptosis was associated with activation of PARP and an increase and activation of Caspase-3. There was no significant change in bcl-x or bax. Therefore bcl-x and bax do not appear to have a significant role in apoptosis in the first trimester in vitro. Cleavage of Caspase-3 rather than transcriptional regulation appears to be the main determinant of Caspase-3 activity in first trimester placental villi.

Pre-eclampsia: associated with increased syncytial apoptosis when the infant is small-for-gestational-age

The present investigation was undertaken to study the association between placental apoptosis and pre-eclampsia, discriminating between pre-eclamptic pregnancies with appropriate-, and small-for-gestational-age (SGA), infants. Twenty pregnancies with pre-eclampsia and SGA (birth weight at or below -2 standard deviations) infants were selected in a retrospective study. Subsequently, corresponding numbers of gestational age-matched pre-eclampsia cases with appropriate-gestational-age (AGA) (birth weight at or above the 50% centile) infants and AGA controls without pre-eclampsia were selected. Formalin-fixed placental tissue was obtained from all groups. Apoptosis was assessed by a monoclonal antibody (M30), detecting a neoepitope of cytokeratin that is generated early in the apoptotic cascade. M30-positive cells were counted in villous and decidual/ basal plate tissue fields, and results were given as numbers of M30-positive cells per field. The study was performed blinded. Increased apoptosis was found in the syncytiotrophoblast layer in pre-eclampsia with SGA infants (0.14 apototic incidents per field of villous tissue, with 0.04-0.23 as the corresponding 25-75% inter quartile range (IQR) (P=0.05)). Syncytial apoptosis in the syncytial layer in the pre-eclampsia group with AGA infants was lower (0.09, IQR 0.03-0.15) and corresponded to the level detected among controls (0.06, IQR 0.03-0.17). Apoptosis in other placental cellular compartments did not differ between groups. The increased syncytial apoptosis found in placentas from pregnancies with SGA infants may either be due to specific mechanisms associated with pre-eclampsia complicated with growth restriction, or may simply reflect the presence of syncytiotrophoblast layer damage, regardless of underlying pathological condition.

Regulation of FasL/Fas in human trophoblasts: possible implications for chorioamnionitis

Chorioamnionitis is a common cause of premature birth and is associated with significant morbidity and mortality in the mother and infant. Preterm birth shares similarities with rejection of the fetal allograft, which is characterized by increased apoptosis of placental trophoblasts. We hypothesized that there is increased trophoblast apoptosis in chorioamnionitis and that this increased apoptosis is mediated by the Fas ligand (FasL)/Fas pathway. To test our hypothesis, we examined placental villous tissues from patients with chorioamnionitis and used the TUNEL assay to demonstrate enhanced trophoblast apoptosis in patients with chorioamnionitis. When the same samples were stained for Fas, there was increased trophoblast Fas expression in patients with chorioamnionitis. To define the mechanisms responsible for this increase in trophoblast apoptosis, we cultured villous explants from uncomplicated term placentas with proinflammatory cytokines and demonstrated a marked increase in trophoblast apoptosis. By blocking FasL, we reduced tumor necrosis factor alpha-induced and interferon gamma-induced apoptosis. These data suggest that chorioamnionitis is associated with increased trophoblast apoptosis and enhanced trophoblast Fas expression. As a complement to our in vivo study, we demonstrated that cytokine-induced trophoblast apoptosis is mediated in part by the FasL/Fas pathway, suggesting that cytokines promote sensitivity to Fas-mediated apoptosis. These mechanisms may be important in perpetuating inflammation in the placental microenvironment and may contribute to the pathogenesis of chorioamnionitis.

Apoptosis and related proteins during parturition in prostaglandin F receptor-deficient mice

This study investigated whether apoptosis and related proteins are involved in parturition by comparative observation of FP-deficient mice without labor and wild type mice with vaginal delivery. We examined the expression of apoptosis, Fas, FasL, active caspase-3 and bcl-2 proteins in the amnion, placenta and decidua. DNA laddering in the amnion, placenta and decidua tissue did not significantly differ between FP-deficient and wild type mice on day 18 of pregnancy. Similar TUNEL staining results were found in all tissues of FP-deficient mice compared with those of wild type mice. A higher intensity of apoptotic cells was found in the decidua basalis. The index of TUNEL-positive cells were not significantly different in the amnion, placenta and decidua of FP-deficient mice compared with that of wild type mice on day 18 of pregnancy. Specific bands for Fas were clearly observed in the amnion, placenta and decidua tissue. FasL specific bands were observed in the placenta and decidua, but a few in amnion tissue. A great number of active caspase-3 specific bands were detected in decidua, while a few such bands were detected in the placenta and few bands in the amniotic tissue. Bands for bcl-2 were detected in the amnion, placenta and decidua tissue. The weakest band was in decidual tissue. Fas, FasL, active caspase-3, and bcl-2 specific bands did not show any significant differences between the two groups. These findings demonstrate that apoptosis, Fas, FasL, caspase-3, and Bcl-2 occur in mouse term placenta that is not involved in parturition.

Placenta detachment: unexpected high concentrations of 5-hydroxytryptamine (serotonin) in fetal blood and its mitogenic effect on placental cells in bovine

The purpose of this study was twofold: (1) to determine whether there is a profile of 5-hydroxytryptamine (5-HT, serotonin) concentrations in fetal bovine blood and tissues during pregnancy, parturition and the early neonatal period and (2) to determine whether 5-HT has a 'mitogenic' effect on cultured placentome cells in bovine. Results revealed a 5-HT concentration profile in fetal blood. Overall concentrations of 5-HT in fetal blood were 6.6 times (P< 0.001) that of adult cows and 2.8 times (P< 0.001) that of blood collected during caesarean section (from umbilical veins) and from 18-72 h old calves. Mid-term and full-term pregnancy fetuses were not statistically different from each other. Overall concentrations of 5-HT in the intestinal wall of the fetus were 4.4 times higher (P< 0.05) than in the 24 h calf. Concentration of 5-HT in full-term muscle was 3.5 times higher than in mid-term muscle and 2.8 times higher than in 24 h old calf muscle (P< 0.05). Concentrations of 5-HT in mid-term and full-term cotyledon were 4.4 times higher (P< 0.05) than in post partum cotyledon. Characterized trophoblast cells and a heterogeneous population of bovine cotyledon cells treated with 5-HT (2.5, 5.0 and 10.0 microm) incorporated between 2.0 and 3.0 times more(3)[H]-thymidine than untreated controls, indicating a dose-dependent (r=0.94) positive mitogenic effect of 5-HT. Both groups of cultured cells responded equally. Five-HT treatment did not affect either cell number or cell size. It was concluded that a 5-HT concentration profile exists in fetal bovine blood and tissues and that 5-HT has the ability to act as a mitogen in bovine placental cells.