Pattern of expression of cyclin D1/CDK4 complex in human placenta during gestation

Progression through the cell cycle in eukaryotic cells is controlled by a family of protein kinases, termed cyclin-dependent kinases (CDKs), and their specific partners, the cyclins. In particular, the control of mammalian cell proliferation occurs largely during the G1 phase of the cell cycle. Five mammalian G1 cyclins have been enumerated to date: cyclins D1, D2, and D3 (D-type cyclins), and cyclins E and E2. By the use of immunohistochemistry and immunoelectron microscopy, we observed that in the first trimester of gestation of human placenta, cyclin D1 was distributed in the nuclei of the cytotrophoblast compartment together with a weak positivity of endothelial cells surrounding blood vessels. The endothelial positivity of cyclin D1 strongly increased in the third trimester of gestation. Moreover, we observed the subcellular localization of cyclin D1 that was present both in the stroma of placental villi and in the nuclei of syncytiotrophoblast cells. Therefore, we observed that CDK4 was localized in the nuclei of the cytotrophoblast compartment during the first and third trimesters and it also had a nuclear positivity in the endothelial cells of blood vessels at the end of the third trimester of gestation. In conclusion we may hypothesize that cyclin D1/CDK4 complex functions to regulate the cell cycle progression in the proliferative compartment of human placenta, the cytotrophoblast, during the first trimester through interaction with p107 and p130. Therefore, cyclin D1 and CDK4 seem to be involved in the control of placental angiogenesis during the third trimester of gestation.

C2360, a nuclear protein expressed in human proliferative cytotrophoblasts, is a representative member of a novel protein family with a conserved coiled coil–helix–coiled coil–helix domain

In this study, we describe the identification of nine novel genes isolated from a unique human first-trimester cDNA library generated from the placental bed. One of these clones, called C2360 and located on chromosome 10q22, was selected as it showed restricted expression in placental bed tissue as well as in JEG3 choriocarcinoma cells with absent expression in adult tissues. We show that the expression is restricted to first-trimester proliferative trophoblasts of the proximal column and show that C2360 is a nuclear protein. No detectable transactivation potential was observed for different domains of the protein. Secondary structure prediction showed that C2360 is a representative member of a eukaryotic family of proteins with a low conservation at the amino acid level, but with strong conservation at the structural level, sharing the general domain (coiled coil 1)-(helix 1)-(coiled coil 2)-(helix 2), or CHCH domain. Each alpha-helix within this domain contains two cysteine amino acids, and these intrahelical cysteines are separated by nine amino acids (C-X(9)-C motif). The fixed position within each helix indicated that both helices could form a hairpin structure stabilized by two interhelical disulfide bonds. Other proteins belonging to the family include estrogen-induced gene 2 and the ethanol-induced 6 protein. The conserved motif was found in yeast, plant, Drosophila, Caenorhabditis elegans, mouse, and human proteins, indicating that the ancestor of this protein family is of eukaryotic origin. These results indicate that C2360 is a representative member of a multifamily of proteins, sharing a protein domain that is conserved in eukaryotes.

Cytoskeletal filaments and associated proteins during restricted trophoblast invasion in bovine placentomes: light and transmission electron microscopy and RT-PCR

Trophoblast cell migration is unusual in epitheliochorial placentae but occurs in placentomes of cows as "restricted" trophoblast invasion of binucleated trophoblast giant cells (TGC). Migration may be induced by integrin binding to the extracellular matrix initiating two pathways: (1) conformational changes of the actin cytoskeleton induced by an accumulation of its associated proteins and (2) integrin-dependent phosphorylation of various protein kinases. In cow placentomes, actin, its associated proteins (alpha-actinin, vinculin) and a key protein kinase of the signal transduction cascade (phosphorylated mitogen-activated protein kinase, pMAPK) were localized by immunogold-silver enhancement and immunoperoxidase staining at the light- and transmission electron-microscopical levels. Findings were confirmed by amplification of specific mRNA transcripts by reverse transcriptase/polymerase chain reaction. Actin and alpha-actinin were co-localized apically in mononuclear trophoblast cells, along the cytoplasmic membrane of TGC and apically in maternal crypt cells. The actin and alpha-actinin immunoreaction occurred as a band of electron-dense particles beneath the cytoplasmic membrane. Vinculin labelling was membrane-associated in TGC and in fetal and maternal endothelial cells. MAPK was observed as nuclear clusters in both kinds of trophoblast cells and was less dense in single uterine epithelial cells. Most MAPK immunoreactivity was detected in the nuclei of the trophoblast epithelium but was also sometimes membrane-associated in the cytoplasm. Thus, actin, alpha-actinin, MAPK and vinculin may be involved in the regulation of TGC migration. "Restricted" trophoblast invasion could serve as a model for invasive processes.

Intrauterine growth retardation: study of placental apoptosis

We studied the rate of apoptosis in the placental tissue of pregnancies complicated with intrauterine growth retardation (IUGR) and compared it with the results obtained in normal placentas. Our results clearly demonstrate a strongly increased rate of apoptosis in placentas of children born with IUGR, suggesting severe placental dysfunction. The significance of these findings needs further study.

[Ultrastructural examination of the placenta in pregnancy complicated by diabetes mellitus]

BACKGROUND

Causes of fetal hypoxia in diabetic pregnancy are still unknown. Investigation of placental vascular network seems of great importance in this research area. Abnormalities in the structure of capillaries in the vasculo-epithelial membranes and role of perivascular space may be an essential factor in explanation for fetal hypoxia in diabetic pregnant women. The aim of the study was to evaluate the relationship between the vascular surface of the terminal villi to its total surface, evaluation of the endothelial structure, perivascular space and basal membrane of the trophoblast as well as analysis of the studied parameters in relation to the classes of diabetes and metabolic control.

MATERIAL AND METHODS

The study was performed on 32 placentas from women with PGDM and GDM. There were 8 pregnant women in class G1 and G2, 15 in class B, C, D, 9 in class R/F and 8 in control group. The mean diurnal glycemia in the analysed groups ranged between 90 + 22 mg/dl and 100 + 55 mg/dl (in control group 80 + 12 mg/dl). HbA1c concentrations were between 6.7 + 0.9% and 7.6 + 1.0% (in control group 6.0 + 0.5%). Placentas were examined using light microscopy and electron microscopy Opton-Zeiss EM-900.

RESULTS

Decrease in the vascular surface of terminal villi was found in PGDM with fetal hypotrophy. In this cases we observed separation of basal membranes in basal capillaries and distention and proliferation of endothelial cells, disarrangements of perivascular space,. In placentas of women with hyperglycemia and fetal macrosomia there was a significant thickening of basal membranes of the trophoblast, and structural abnormalities in perivascular space with proliferation of collagen in terminal villi. Intensity of these changes was related to the degree of hyperglycemia and affected fetal and neonatal wellbeing. Examination of the placentas in women with PGDM with normal sugar levels before and during pregnancy revealed no or very limited pathological changes on light and electron microscopy. No significant relationships were shown between vascular surface in terminal villi and selected biochemical parameters and neonatal condition in diabetic pregnant women with fetal eutrophy

CONCLUSIONS

Pathologic changes in the placentas of diabetic women (significant thickening of basal membranes of trophoblast separation of basal membranes in basal capillaries, distention and proliferation of endothelial cells, disarrangements of perivascular space and decrease of vascular surface of terminal villi are significant factors contributing to fetal anoxia in pregnancy complicated by diabetes mellitus.

Genome multiplication of extravillous trophoblast cells in human placenta in the course of differentiation and invasion into endometrium and myometrium. II. Mechanisms of polyploidization

Peculiarities of the structure of interphase nuclei, mitotic activity, and Ki-67 protein intranuclear immunolocalization were studied to elucidate mechanisms of genome multiplication in proliferative and differentiating invasive extravillous trophoblast cells in the human placenta. The presence of numerous chromocenters was shown to be a characteristic feature of proliferative cell nuclei of both villous and extravillous trophoblast. At the beginning of extravillous trophoblast cell differentiation, i.e. in the proximal part of cell columns, some amount of cells with large nuclei containing enlarged chromocenters were found. DNA content was measured simultaneously with counting the number of chromocenters in similarly looking nuclei of squash preparations of placental villi. The increase in the ploidy level up to 4c-8c, accompanied by a slight increase in the number of chromocenters being not proportional to the ploidy level and not exceeding the diploid number of chromosomes of the human genome, was demonstrated. This suggests that genome multiplication of extravillous trophoblast cells may be accomplished by endoreduplication. In addition, pictures of endomitosis were seen at early steps of differentiation of EVT cells. The lack of polyploid mitotic figures or any obvious polyploidizing or restitutional mitoses suggests that these are not of considerable importance in genome multiplication of human EVT cells. However, the prevalence of metaphases at the boundary of the distal part of cell columns suggests that restitutional mitoses may be involved, even partly, in human trophoblast cell polyploidization. At later steps of differentiation, i.e. in the distal part of cell columns, the nuclear structure obviously changes, with a uniform "network" chromatin arrangement prevailing, whereas numerous chromocenters and features of endomitosis are no longer seen. The pattern of Ki-67 protein immunolocalization is also changing along the invasive pathway. In the proliferating stem cells and trophoblast cells of the proximal part of cell columns, Ki-67 was localized in the karyoplasm, chromocenters and numerous small nucleoli, whereas in the distal part of cell columns this protein was detected predominantly in 1-2 large nucleoli. The comparative analysis of the literature data on Ki-67 localization at different stages of cell cycle provided another evidence that EVT cells in the course of invasion may switch to the endoreduplication cycle. In agreement with the relevant report on rodent placentation, our present data suggest that acquirement of an invasive phenotype of EVT cells is accompanied by switching from mitotic division to endoreduplication cycle.

Partial characterization of human choriocarcinoma cell line JAR cells in regard to oxidative stress

Characterization of free radical-induced cell injury processes of placenta cells is of vital importance for clinical medicine for the maintenance of intrauterine fetal life. The present study has analyzed cell injury processes in cells of the choriocarcinoma cell line JAR treated with menadione, an anticancer drug, and H(2)O(2) in comparison to osteosarcoma 143B cells using electron microscopic and flow cytometric techniques. Flow cytometry on JAR cells exposed to 100 muM menadione and double-stained with Annexin V and propidium iodide (PI) detected apoptotic cells reaching the maximum after 4 h of incubation with a rapid decrease thereafter. Viable cells became decreased to 46% of the control after 2 h of incubation, reaching 5% after 4 h. Cells stainable with both Annexin V and PI began to increase distinctly after 2 h of incubation, reaching 55% after 4 h. Electron microscopy showed that cells stainable with both dyes specified above had condensed nuclei and swollen cytoplasm, suggesting that they were undergoing a switch of the cell death mode from apoptosis to necrosis. On the other hand, 90% of 143B cells remained intact after 4 h of menadione treatment although the intracellular levels of superoxide were always higher than those of JAR cells treated with the drug. In contrast, JAR cells were more resistant than 143B cells to H(2)O(2)-induced cytotoxicity. These results may suggest that cytotoxicity of menadione cannot be explained simply by oxygen free radicals generated from the drug. The resistance of JAR cells to oxygen free radical-induced cytotoxicity may be advantageous for intrauterine fetal life.

Bromodichloromethane inhibits human placental trophoblast differentiation

Epidemiological data suggest an association between exposures to bromodichloromethane (BDCM), a trihalomethane found in drinking water as a result of drinking water disinfection, and an increased risk of spontaneous abortion. We previously hypothesized that BDCM targets the placenta and showed that the secretion of chorionic gonadotrophin (CG) was reduced in primary cultures of human term syncytiotrophoblasts exposed to BDCM. In the present study we extend this observation by evaluating the effects of BDCM on the morphological differentiation of mononucleated cytotrophoblast cells to multinucleated syncytiotrophoblast-like colonies. Addition of BDCM to cytotrophoblast cultures inhibited the subsequent formation of multinucleated colonies in a dose-dependent manner, as determined by immunocytochemical staining for desmosomes and nuclei. The effect was seen at BDCM concentrations between 0.02 and 2 mM and was confirmed by quantitative image analysis. Secretion of bioactive and immunoreactive chorionic gonadotropin was also significantly inhibited in a dose-dependent manner under these culture conditions, and cellular levels of CG were also reduced. Trophoblast viability was not compromised by exposure to BDCM. We conclude that BDCM disrupts syncytiotrophoblast formation and inhibits CG secretion in vitro. Although other tissue targets are not ruled out, these data substantiate the idea that BDCM targets the placenta and could have implications for understanding the adverse pregnancy outcomes associated with BDCM exposure in humans.

Alpha-2 Macroglobulin Controls Trophoblast Positioning in Mouse Implantation Sites

In humans, functional deficiency of alpha-2M is not known, implying alpha 2M is essential for gestational success. Mice, deficient in two members of the alpha-2 Macroglobulin (alpha 2M) family, i.e. alpha-2 macroglobulin (MAM) and murinoglobulin-1 (MUG-1) are viable, fertile and phenotypically normal, unless stressed (Am J Pathol, 155 (1999), 983). Here, we analysed implantation sites in MAM(-/-)/MUG-1(-/-)mice during pregnancy, a strong physiological stressor. Despite some post-implantation fetal loss, mean litter size was comparable to congenic C57Bl/6J (B6) mice, but MAM(-/-)/MUG-1(-/-)pups were significantly lighter and the sex ratio was skewed towards males. Implantation sites appeared histologically normal up to gestational day (gd) 8. By gd 10, extensive over-development of trophoblasts was evident, accompanied by relative deficits in decidua, in the mural mesometrial lymphoid aggregates of pregnancy and in uterine Natural Killer cells. At gd 10-12, decidual spiral arteries were dilated but abnormally cuffed by trophoblasts that extended anomalously, for midgestation, to the myometrial circular smooth muscle. Ultrastructurally, trophoblasts in the mesometrial decidua made intimate contact with endothelial cells that were shedding membrane fragments. These findings demonstrate that alpha 2M, and thereby proteinases and/or cytokines whose bio-availability is regulated by alpha 2M, exert significant decidual regulation on trophoblast invasion.

[Effect of insulin on apoptosis of cultured human trophoblast cells and its mechanism]

AIM

To explore the effect of insulin on apoptosis of cultured human trophoblast cells and its possible mechanism.

METHODS

Human trophoblast cells from early pregnancy women were cultured and divided into 3 groups; normal control group; H2O2, treatment group and insulin plus H2O2 treatment group. H2O2 was used to induce apoptosis of trophoblasts cells. Apoptotic rate was detected by flow cytometry. The effects of insulin on Bcl-2 expression and caspase-3 activity were also detected.

RESULTS

H2O2 might induce apoptosis of trophoblast cells and typical morphological features of apoptotic cells was observed under electron microscope. Flow cytometry detection exhibited that insulin could reduce markedly H2O2-induced apoptotic rate of trophoblasts cells (P < 0. 01). Bcl-2 expression rate inH,O, treatment group was significantly lower than that in control group (P < 0. 01), while caspase-3 activity was distinctly higher than that in control group (P < 0. 01).

CONCLUSION

Insulin could inhibit apoptosis of human trophoblasts cells induced by H2O2, which be may through decreased caspase-3 activity and increased Bcl-2 protein expression.

Trypanosoma cruzi infection induces microfilament depletion in human placenta syncytiotrophoblast

Congenital Chagas disease, endemic in Latin America, is associated with premature labour, miscarriage, and placentitis. Metacyclic trypomastigotes adhere to specific receptors on the outer membrane of host cells as a prelude to intracellular invasion, causing calcium ion mobilization, rearrangement of host cell microfilaments, recruitment of lysosomes and parasite internalization. The actin cytoskeleton plays an important role in many cellular processes including the parasite invasion into mammalian cells. In order to observe if placental cytoskeleton is altered in the process of parasite invasion into placental villi, actin microfilaments were studied. Using immunohistochemical techniques, it was observed that the presence of actin in the syncytiotrophoblast was intense throughout the brush border in control placentae belonging to non-chagasic women. But after culture with the trypomastigote, this labelling disappeared, indicating that the parasite induced disassembly of the cortical actin cytoskeleton when the placenta was infected. As a control, placentae from chagasic women were studied, and no actin was found. The same results were obtained by the electron microscope. We confirmed that cortical actin rearrangements may be an early step in the Trypanosoma cruzi invasion mechanism into placental cells, in order to allow lysosomes access to the plasma membrane, and formation of the parasitophorous vacuole. The recruitment of lysosomes occurs directly beneath the invasion site, and this process is required for parasite internalization.

Human invasive trophoblasts transformed with simian virus 40 provide a new tool to study the role of PPARgamma in cell invasion process

Invasive cytotrophoblasts play a key role in the development of human placenta and is therefore essential for subsequent development of the embryo. Human implantation is characterized by a major trophoblastic invasion that offers a unique model of a controlled and oriented tumor-like process. The ligand-activated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) modulates cell growth and differentiation and might be therefore considered as a tumor suppressor. We have recently reported that PPARgamma, in synergy with its dimerization partner retinoid X receptor (RXR)alpha, controls the invasion of human primary cytotrophoblasts. Because these cells are unable to replicate in culture, we have, in the present study, transformed these primary cells with the simian virus 40 large T antigen for studying the role of PPARgamma in cell invasion process. Our results show that the cell line human invasive proliferative extravillous cytotrophoblast (HIPEC) 65 expressed markers of human invasive primary cytotrophoblast as determined by immunocytochemistry, immunobloting and real-time RT-PCR, and were highly invasive in vitro. We have next studied the role of PPARgamma/RXRalpha heterodimers in cell proliferation and invasion. Our results show that PPARgamma and RXRalpha are co-expressed by HIPEC 65 and that, as commonly observed, activation of PPARgamma/RXRalpha heterodimers with the specific PPARgamma agonist rosiglitazone induced lipid droplet accumulation as revealed by oil red O staining. Treatment with rosiglitazone or with the natural PPARgamma agonist 15-deoxy-delta-(12,14) PGJ2 did not modify cell growth, but interestingly, activation of PPARgamma by this synthetic (rosiglitazone) or natural (15d-PGJ2) ligand markedly inhibited cell invasion in a concentration-dependent manner. Finally, we showed that other potential natural PPARgamma ligand such as oxidized-but not native-low-density lipoprotein inhibited cell invasion. This proliferative and invasive human cytotrophoblast cell line from extravillous origin provides a new tool for studying specifically the role of PPARgamma in the control of cell invasion.

Targeted disruption of the mouse rho-associated kinase 2 gene results in intrauterine growth retardation and fetal death

Rho-associated kinase (ROCK), including the ROCK-I and ROCK-II isoforms, is a protein kinase involved in signaling from Rho to actin cytoskeleton. However, in vivo functions of each ROCK isoform remain largely unknown. We generated mice deficient in ROCK-II by gene targeting. ROCK-II(-/-) embryos were found at the expected Mendelian frequency until 13.5 days postcoitum, but approximately 90% died thereafter in utero. ROCK-II(-/-) mice of both genders that survived were born runts, subsequently developed without gross abnormality, and were fertile. Whole-mount staining for a knocked-in lacZ reporter gene revealed that ROCK-II was highly expressed in the labyrinth layer of the placenta. Disruption of architecture and extensive thrombus formation were found in the labyrinth layer of ROCK-II(-/-) mice. While no obvious alteration in actin filament structures was found in the labyrinth layer of ROCK-II(-/-) placenta and stress fibers were formed in cultured ROCK-II(-/-) trophoblasts, elevated expression of plasminogen activator inhibitor 1 was found in ROCK-II(-/-) placenta. These results suggest that ROCK-II is essential in inhibiting blood coagulation and maintaining blood flow in the endothelium-free labyrinth layer and that loss of ROCK-II leads to thrombus formation, placental dysfunction, intrauterine growth retardation, and fetal death.

Placentation in the African elephant (Loxodonta africana): II morphological changes in the uterus and placenta throughout gestation

The gross and microscopic development of the zonary endotheliochorial placenta in the African elephant was studied in 22 gravid uteri that ranged in gestational stage from 0.5 to 20.6 months. The conceptus only ever occupies one horn of the uterus and is associated with 2-5 large corpora lutea that persist in the ipsilateral ovary throughout gestation. Initially, the trophoblast in the equatorial region of the conceptus completely replaces the lumenal epithelium of the endometrium to which it is apposed. Blunt upgrowths of endometrial stroma then develop, each closely invested by trophoblast, and containing the capillaries that will vascularize this maternal component of the resulting placental band. With advancing gestation the lamellate stromal upgrowths increase markedly in length and become much thinner, thereby bringing the trophoblast into intimate contact with the endothelium of the maternal capillaries. They also become folded or pleated to increase the total area of intimate feto-maternal contact. At the lateral edges of the placental band the lamellae bend over towards the endometrium to form a blind cleft. Leakage of blood into this area creates haemophagous zones in which phenotypically specialized trophoblast cells phagocytose the blood components. The presence of large resorbing blood clots and circumferential scars in the uteri of three post parturient animals initiated the hypothesis that, when the standing elephant gives birth at term, the passage of the 120 kg fetus through the vagina may wrench the placenta off the endometrium by severing its very narrow maternal placental hilus. The resulting intrauterine haemorrhage may then play a role in preventing further conception for around 2 years.

Placentation in the alpaca Lama pacos

Reproduction in South American camelids is poorly studied. To extend our knowledge of the development and cellular physiology of the placenta in the alpaca Lama pacos, we have examined specimens from day 150 of pregnancy to term. Morphological investigations using light, transmission and scanning electron microscopy, the histochemical localization of iron, alkaline and acid phosphatase activity, and the immunodetection of placental lactogen hormone were performed. Throughout pregnancy there was a progressive increase in the depths of folds on the uterine mucosa surface together with a thickening of the endometrium. Glandular cells exhibited PAS and acid phosphatase (AcP) positive secretion granules. In the chorion, giant trophoblast polyploid cells gradually became more numerous and larger. Non-giant cells exhibited positive granules for PAS, alkaline phosphatase (AkP) reaction and immunostaining for bovine placental lactogen hormone (PLH). SDS -PAGE electrophoresis and Western blotting procedures also confirmed the presence of a bovine PLH-like glycoprotein in the fetal alpaca placenta. Over the glandular openings, the chorion formed typical areolae, where the trophoblast exhibited AcP and PAS positive reactions. At these sites, the fetal endothelial cells contained iron-storage granules in their cytoplasm. The trophoblast-epithelial interface exhibited a complex microvillous interdigitation, in which an AkP reaction was very prominent. The chorionic capillaries progressively indented adjacent trophoblast cells. These data suggest that although the epitheliochorial alpaca placenta is diffuse, various trophoblast cell types and specialized areas of the maternofetal interface give the placenta micro-regional functions where histiotrophic nutrition, hormone production and molecular exchange are prevalent.

Activity and protein expression of Na+/K+ ATPase are reduced in microvillous syncytiotrophoblast plasma membranes isolated from pregnancies complicated by intrauterine growth restriction

In contrast to classical transporting epithelia, the Na(+)/K(+) ATPase is distributed to both the microvillous membrane (MVM) and the basal membrane (BM) of the placental syncytiotrophoblast. Na(+)/K(+) ATPase is important in maintaining the electrochemical gradient for Na(+), which represents the driving force for Na(+)-coupled transport of nutrients. We hypothesized that syncytiotrophoblast Na(+)/K(+)-ATPase activity is reduced in intrauterine growth restriction (IUGR). We isolated MVM and BM from control (n = 10) and IUGR placentas (n = 11). The protein expression of Na(+)/K(+)-ATPase alpha(1)-subunit was determined by Western blotting and found to be slightly reduced in MVM isolated from IUGR (-10%; P < 0.05) placentas. Na(+)/K(+) ATPase activity was measured as the ouabain-sensitive, K(+)-dependent cleavage of the fluorescent pseudosubstrate 3-O-methylfluorescein phosphate and was reduced by 35% in MVM obtained from IUGR placentas (P < 0.02). To assess the transcriptional levels of Na(+)/K(+)-ATPase mRNA, real time PCR was used. No significant changes in steady state mRNA levels for Na(+)/K(+)-ATPase were detected. The expression of the Na(+)/K(+)-ATPase alpha(1)-subunit and Na(+)/K(+)-ATPase activity in the BM were unaffected in cases of IUGR. These data suggest that Na(+)/K(+)-ATPase activity is reduced in the MVM of placentas from IUGR pregnancies. These changes might impair the function of Na(+)-coupled transporters and contribute to the reduced growth of these fetuses.

Placental expression of estrogen receptor beta and its hormone binding variant--comparison with estrogen receptor alpha and a role for estrogen receptors in asymmetric division and differentiation of estrogen-dependent cells

During human pregnancy, the production of 17-beta-estradiol (E2) rises steadily to eighty fold at term, and placenta has been found to specifically bind estrogens. We have recently demonstrated the expression of estrogen receptor alpha (ER-alpha) protein in human placenta and its localization in villous cytotrophoblast (CT), vascular pericytes, and amniotic fibroblasts. In vitro, E2 stimulated development of large syncytiotrophoblast (ST) aggregates. In the present study we utilized ER-beta affinity purified polyclonal (N19:sc6820) and ER-alpha monoclonal (clone h-151) antibodies. Western blot analysis revealed a single approximately 52 kDa ER-beta band in chorionic villi (CV) protein extracts. In CV, strong cytoplasmic ER-beta immunoreactivity was confined to ST. Dual color immunohistochemistry revealed asymmetric segregation of ER-alpha in dividing villous CT cells. Prior to separation, the cell nuclei more distant from ST exhibited high ER-alpha, while cell nuclei associated with ST showed diminution of ER-alpha and appearance of ER-beta. In trophoblast cultures, development of ST aggregates was associated with diminution of ER-alpha and appearance of ER-beta immunoreactivity. ER-beta was also detected in endothelial cells, amniotic epithelial cells and fibroblasts, extravillous trophoblast (nuclear and cytoplasmic) and decidual cells (cytoplasmic only). In addition, CFK-E12 (E12) and CWK-F12 (F12) monoclonal antibodies, which recognize approximately 64 kDa ER-beta with hormone binding domain, showed nuclear-specific reactivity with villous ST, extravillous trophoblast, and amniotic epithelium and fibroblasts. Western blot analysis indicated abundant expression of a approximately 64 kDa ER-beta variant in trophoblast cultures, significantly higher when compared to the chorionic villi and freshly isolated trophoblast cell protein extracts. This is the first report on ER-beta expression in human placenta and cultured trophoblast. Our data indicate that during trophoblast differentiation, the ER-alpha is associated with a less, and ER-beta with the more differentiated state. Enhanced expression of approximately 64 kDa ER-beta variant in trophoblast cultures suggests a unique role of ER-beta hormone binding domain in the regulation of trophoblast differentiation. Our data also indicate that asymmetric segregation of ER-alpha may play a role in asymmetric division of estrogen-dependent cells.

Effect of labor on glucocorticoid receptor (GR(Total), GRalpha, and GRbeta) proteins in ovine intrauterine tissues

OBJECTIVE

Activation of the fetal hypothalamic-pituitary-adrenal axis and a concurrent increase in plasma cortisol concentration plays a crucial role in parturition in sheep. The effects of cortisol on intrauterine tissues are mediated, in part, by glucocorticoid receptors (GR). In the present study, we determined the temporal and tissue-specific expression of GR(Total), GRalpha, and GRbeta isoforms in ovine placenta, fetal membranes, and uterus during the onset and progression of labor.

METHODS

Intrauterine tissues were collected from following three groups of pregnant ewes at term (147-149 days of gestation): animals not in labor (NIL; 140-145 days; n = 5), early labor (EL; 143-149 days; n = 6), and active labor (L; 145-149 days; n = 6). They were analyzed for GR(Total), GRalpha, and GRbeta by immunohistochemical and Western blot analyses.

RESULTS

GR(Total), GRalpha, and GRbeta proteins were present in trophoblast cells but not maternal tissue of the placentome. GRalpha and beta were distinctly expressed in trophoblast nuclei and cytosol, respectively. GR(Total), GRalpha, and GRbeta were also detected in amnion epithelial cells and chorionic epithelium of the fetal membranes, and the maternal endometrial epithelium. GR(Total) and GRalpha were also present in amnion mesenchymal and glandular epithelium. GR(Total) and GRalpha (95 kDa) protein levels were significantly (P < .05) higher during labor; GRbeta (90 kDa) levels remained unchanged.

CONCLUSION

The temporal and tissue-specific pattern of GR expression within ovine intrauterine tissues during labor implicates GR in regulating cortisol action to induce enzymatic changes controlling labor in sheep.

Alphavbeta3 integrin signaling pathway is involved in insulin-like growth factor I-stimulated human extravillous trophoblast cell migration

IGF-I and -II provide paracrine and autocrine stimuli, respectively, for extravillous trophoblast (EVT) cell migration. This study examined the role of alpha(v)beta(3) integrin and its signaling pathway in IGF-I-stimulated migration. Migration assays were conducted using cultured EVT cells treated with or without IGF-I in the presence or absence of alphaIR3, Arg-Gly-Asp (RGD) hexapeptide, and antibody against alpha(v)beta(3) integrin. Morphological changes were studied using scanning electron microscopy. Colocalization of alpha(5)beta(1) alpha(v)beta(3) integrins, vinculin, focal adhesion kinase, and paxillin were determined by immuno-cytochemistry and immunoblotting. The results showed that IGF-I could stimulate EVT cell migration in a time- and dose-dependent manner and addition of alphaIR3, Arg-Gly-Asp hexapeptide, and antibody against alpha(v)beta(3) integrin attenuated the IGF-I migratory effect. Scanning electron microscopy images revealed that IGF-I promoted lamellipodia formation. Immunostaining and immunoblotting exhibited the colocalization of alpha(v)beta(3) integrin with phosphorylated focal adhesion kinase, paxillin, and vinculin at focal adhesions after IGF-I treatment. Immunoblotting demonstrated an increase in focal adhesion kinase and paxillin tyrosine phosphorylation followed by tyrosine phosphorylation of IGF-I receptor in a time- and dose-dependent manner. These findings indicated alpha(v)beta(3) integrin localization in the core of focal adhesions of EVT cells and that alpha(v)beta(3) integrin signaling pathways are activated in IGF-I-mediated migration of these cells.

Expression of Fas/Fas-ligand, Bcl-2 protein and apoptosis in extravillous trophoblast along invasion to the decidua in human term placenta

There are two local subtypes of extravillous trophoblast (EVT): one is the proliferative phenotype of EVT, which primarily consists of proximal cells and the other is the invasive phenotype of EVT, which is composed mainly of distal cells of cell columns. The mechanism of invasion of EVT to the decidua remains obscure. In order to elucidate the potential role of apoptosis along the invasion of EVT to the decidua, we have assessed the expression of apoptosis-regulating proteins including Fas antigen (Fas), Fas-ligand (Fas-L) and Bcl-2 protein, and apoptosis in the proliferative phenotype of EVT and the invasive phenotype of EVT in term (37 to 38 wk) placenta Fas, Fas-L and Bcl-2 protein expression were examined by avidin/biotin immunoperoxidase method. Apoptosis was assessed by in situ DNA 3'-end labeling method. Appearance of apoptotic nuclei in EVT was also examined by transmission electron microscopy. Mean percentage of apoptosis-positive nuclei in the invasive phenotype of EVT was significantly higher than that in the proliferative phenotype of EVT. Transmission electron microscopy revealed the presence of apoptotic nuclei in the invasive phenotype of EVT. Immunohistochemical analyses revealed that Fas and Fas-L expression in the invasive phenotype of EVT were more abundant than those in the proliferative phenotype of EVT, while Bcl-2 protein expression in the invasive phenotype of EVT was less abundant than that in the proliferative phenotype of EVT. The present findings suggest that Fas/Fas-L and Bcl-2 protein expression participate in the regulation of apoptosis in EVT along the invasion to the decidua, and that the increased occurrence of apoptosis in the invasive phenotype of EVT may be attributable to the increased expressions of Fas and Fas-L and decreased expression of Bcl-2 protein in those cells in term placentas.

Decidual lymphocytes of human spontaneous abortions induce apoptosis but not necrosis in JEG-3 extravillous trophoblast cells

The human decidua contains an unusually high proportion of lymphocytes, mainly NK and T cells, which are potentially cytotoxic to the trophoblast when they are stimulated with certain cytokines. Given the high incidence of spontaneous abortion in humans and other species, our working hypothesis is that decidual lymphocytes are involved in immunological mechanisms that attack the trophoblast and induce abortion when any gestational problem arises. To test this hypothesis, flow cytometry was used to compare decidual lymphocyte populations in first-trimester spontaneous abortions and elective terminations of first-trimester pregnancy. We found significantly higher proportions of decidual lymphocytes that expressed activation markers, and of T cells (mainly T helper cells) in spontaneous abortions than in elective terminations of pregnancy. Decidual lymphocytes from spontaneous abortion, like decidual lymphocytes from elective termination of pregnancy and peripheral blood lymphocytes, were however, unable to lyse the JEG-3 extravillous cytotrophoblast cell line in a (51)Cr-release assay. Nevertheless, decidual lymphocytes from spontaneous abortion, unlike decidual lymphocytes from elective termination of pregnancy and peripheral blood lymphocytes, induced apoptosis in JEG-3 cells as determined by DNA fragment-release assay. Hematoxylin and eosin staining showed a significantly higher proportion of apoptotic JEG-3 cells when these cells were treated with decidual lymphocytes from spontaneous abortion than when JEG-3 cells were cultured with decidual lymphocytes from elective termination of pregnancy. The ultrastructural signs of apoptosis were confirmed by electron microscopy. These data support the hypothesis that activated decidual lymphocytes participate in human spontaneous abortion by inducing apoptosis but not necrosis of the trophoblast.

Developmental changes in the ploidy of mouse implanting trophoblast cells in vitro

Shortly after the onset of implantation, polar mouse trophoblast cells proliferate and give rise to the ectoplacental cone, constituted by two distinct cell populations: undifferentiated, diploid cells and giant cells. Giant cells characteristically exhibit exaggerated dimensions and polyploid nuclei. In this study, we employ ectoplacental cones as a dynamic source of trophoblast giant cells to analyze cell proliferation, cell death, and ploidy under in vitro conditions. Our results show that DNA synthesis and the increase in the cell number are relevant only during the first 24 h of culture. Subsequently, DNA synthesis still occurs, mainly in the giant cell compartment, while the number of cells gradually decreases. Cell death by injury and apoptosis was also observed in the non-giant cell compartment of the ectoplacental cone. These findings suggest that the first 24 h of culture are crucial to the mitotic activity of the ectoplacental cone cells that gradually ceases, favoring the endoreduplication process. The DNA synthesis index during the subsequent experimental intervals emphasizes accumulation of DNA for the polyploidization. There was clear correlation between DNA content and nuclear dimension. The ploidy values for the trophoblast giant cells varied from 2C up to 368C in the giant cells, but were not as expressive as those known from in vivo conditions, probably due to the absence of regulatory factors specific to the embryonic-maternal interface. In situ hybridization and histochemistry for the nucleolus-organizing region showed that trophoblast nuclei have only two marker signals, indicative of a typical polytenic process. This present study elucidates important aspects of trophoblast behavior and provides new information on trophoblast physiology in vivo and in vitro.

Necrotic feature of the trophoblasts lacking HLA-G expression in normal and pre-eclamptic placentas

PROBLEM

Human leukocyte antigen (HLA)-G is thought to be expressed in all placental extravillous trophoblasts (EXTs). In pre-eclamptic placentas, a lack of HLA-G expression on EXTs had been found, and deduced as a possible cause of pre-eclampsia. However, a subset of EXTs lacking expression of HLA-G can also be found in normal placenta. Therefore, we sought to compare these cells in normal and pre-eclamptic placentas.

METHODS OF STUDY

Frozen sections of normal and pre-eclamptic placentas were examined by immunohistochemical staining using HLA-G monoclonal antibody 87G, histochemical enzymatic analysis of succinate dehydrogenase (SDH) and ultrastructural analysis.

RESULTS

A subset of EXTs lacking HLA-G expression was found in both normal and pre-eclamptic placentas. These cells showed necrotic features such as the swelling of cells, eosin-achromatophilia, the loss of SDH activity and swelling mitochondria. Cells from both tissues were identical with regard to these features.

CONCLUSION

The features of the EXTs lacking HLA-G expression indicated they had undergone necrosis and thus could not express HLA-G protein. Therefore, an alternative interpretation to the lack of HLA-G expression in pre-eclamptic placentas is that it is the result of cell death and not the cause.

Effects of Aroclor 1254 on the expression of rat placental PRL-family genes

This study was performed to investigate the effects of Aroclor 1254 (A1254), a commercial polychlorinated biphenyl mixture, on the expression of rat placental prolactin (PRL) family genes and reproductive activity. Placental lactogen-Iv and -II, and prolactin-like protein-A and -C mRNA levels were significantly decreased in the placentas of A1254-treated rats in a dose-dependent manner. The mRNA levels of Pit-1alpha and beta isotypes, which are involved in the regulation of PRL family gene expression, were also decreased in the A1254-treated rat placenta. In the rat placental junctional zone, high-dose A1254 (25 mg/kg B.W.) treatment reduced the number of spongiotrophoblasts, cells in which the PRL family genes are expressed. Finally, maternal exposure to A1254 was shown to have significant toxic effects on reproductive activity, including embryonic and placental growth retardation, delay of parturition, and reduction of the number of pups per litter. The results of the present study indicated that A1254 has an inhibitory effect on PRL family, Pit-1alpha, and beta gene expression in the rat placenta, leading to significant toxic effects on reproductive activity in rats.

Analysis and characterization of differential gene expression during rapid trophoblastic elongation in the pig using suppression subtractive hybridization

During late peri-implantation development, porcine conceptuses undergo a rapid (2-3 hrs) morphological transformation from a 10 mm sphere to a thin filamentous form greater than 150 mm in length. Elongation of the conceptus is important for establishing adequate placental surface area needed for embryo and fetal survival throughout gestation. Genes involved with triggering this unique transition in conceptus development are not well defined. Objective of the present study was to utilize suppression subtractive hybridization (SSH) to characterize the change in gene expression during conceptus transformation from spherical (8-9 mm) to tubular (15-40 mm) to early filamentous (>150 mm) morphology. Spherical, tubular, and filamentous conceptuses were collected from pregnant gilts and subjected to SSH. Forward and reverse subtractions were performed to identify candidate genes differentially expressed during spherical to tubular and tubular to filamentous transition. A total of 384 transcripts were differentially screened to ensure unique expression. Of the transcripts screened, sequences were obtained for 142 that were confirmed to be differentially expressed among the various morphologies. Gene expression profiles during rapid trophoblastic elongation were generated for selected mRNAs using quantitative real-time PCR. During the transition from tubular to early filamentous conceptuses, s-adenosylhomocysteine hydrolase and heat shock cognate 70 kDa expression were significantly enhanced. A novel unknown gene was isolated and shown to be significantly up-regulated at the onset of rapid trophoblastic elongation and further enhanced in filamentous conceptuses.