Uptake of dehydroepiandrosterone-3-sulfate by isolated trophoblasts from human term placenta, JEG-3, BeWo, Jar, BHK cells, and BHK cells transfected with human sterylsulfatase-cDNA

The human placenta lacks the enzyme 17-hydroxylase/17-20-lyase, and is thus unable to convert cholesterol into estrogens. Therefore estrogen synthesis of trophoblast cells depends on the supply of precursors such as dehydroepiandrosterone-3-sulfate (DHEA-S) and 16-hydroxy-dehydroepiandrosterone-3-sulfate by maternal and fetal blood. To investigate the cellular internalisation of these anionic hydrophilic precursors, the uptake of [³H]-/[³⁵S]-DHEA-S and [³H]-taurocholate by isolated cytotrophoblasts, cells of choriocarcinoma cell lines (JEG-3, BeWo, Jar), BHK and BHK cells transfected with human sterylsulfatase-cDNA (BHK-STS cells) was studied. Furthermore, the activity of sterylsulfatase of these cells in suspension and in corresponding cell homogenate was measured.

During the first 5 min of incubation with [³H]-DHEA-S or [³⁵S]-DHEA-S, radioactivity of cytotrophoblasts increased significantly, while radioactivity of JEG-3, Jar, BHK and BHK-STS cells did not increase. Radioactivity of BeWo cells increased slightly. For all cell types, there was no significant difference for uptake of either substrate. During incubation with [³H]-taurocholate, radioactivity of cytotrophoblasts did not increase. Sterylsulfatase activity of cytotrophoblast homogenate was significantly lower than that of cytotrophoblast suspension. Sterylsulfatase activity of BHK-STS, JEG-3 or BeWo cell homogenate was significantly higher than that of the corresponding cell suspension. In BHK and Jar cells sterylsulfatase activity was not detectable.

Cytotrophoblasts take up DHEA-S without prior hydrolysis. BHK, BHK-STS, JEG-3, and Jar cells do not take up and BeWo cells slowly take up DHEA-S. In cytotrophoblasts extracellular DHEA-S rapidly gains access to intracellular sterylsulfatase, while in choriocarcinoma and BHK-STS cells access of DHEA-S to sterylsulfatase is limited. Our results indicate, that uptake by cytotrophoblasts is mediated by a carrier which is not expressed in choriocarcinoma or BHK cells and which is different from the known taurocholate-transporting organic anion transporting polypetides.     

Regulation of the gene for estrogenic 17-ketosteroid reductase lying on chromosome 17cen----q25

17-Ketosteroid reductase (17KSR), also known as 17 beta-hydroxysteroid dehydrogenase, catalyzes the reversible interconversion of estradiol to estrone and of androstenedione to testosterone. Using a recently cloned human placental 17KSR cDNA, we show that the 1.4-kilobase mRNA for this enzyme is detected only in tissues producing estrogens, and a 2.4-kilobase mRNA is detected in some estrogenic tissues and some androgenic tissues. This tissue distribution suggests that the interconversion of androstenedione and testosterone may be mediated by a different enzyme. Southern blotting studies show that the mRNA for this estrogenic 17KSR is encoded by two very similar genes localized to chromosome 17cen----q25 by analysis of DNA from mouse/human somatic hybrid cell lines. 8-Br-cAMP increases the abundance of estrogenic 17KSR mRNA as well as mRNAs for other steroidogenic enzymes in JEG-3 choriocarcinoma cells. By contrast, cAMP decreases estrogenic 17KSR mRNA in primary cultures of human cytotrophoblasts and human granulosa cells, a pattern of tropic regulation that differs from other steroidogenic enzyme mRNAs.     

Regulation of expression of the 3β-hydroxysteroid dehydrogenases of human placenta and fetal adrenal

The appropriate expression of 3β-hydroxysteroid dehydrogenase/Δ^5→4-isomerase (3β-HSD) is vital for mammalian reproduction, fetal growth and life maintenance. Several isoforms of 3β-HSD, the products of separate genes, have been identified in various species including man. Current investigations are targeted toward defining the processes that regulate the levels of specific isoforms in various steroidogenic tissues of man. High levels of expression of 3β-HSD were observed in placental tissues. It has been generally considered that the multinucleated syncytiotrophoblastic cells are the principal sites of 3β-HSD expression and, moreover, that 3β-HSD expression is intimately associated with cyclic AMP-promoted formation of syncytia. Herein we report the presence of 3β-HSD immunoreactive and mRNA species in uninucleate cytotrophoblasts in the chorion laeve, similar to that in syncytia but not cytotrophoblast placenta. In vitro, 3β-HSD levels in chorion laeve cytotrophoblasts were not increased with time nor after treatment with adenylate cyclase activators, whereas villous cytotrophoblasts spontaneously demonstrated progressive, increased 3β-HSD expression. Moreover, 3β-HSD synthesis appeared to precede morphologic syncytial formation. Thus high steroidogenic enzyme expression in placenta is not necessarily closely linked to formation of syncytia. Both Western immunoblot and enzymic activity analyses also indicated that the 3β-HSD expressed in these cytotrophoblastic populations was the 3β-HSD type I gene product (M_r, 45K) and not 3β-HSD type II (M_r, 44K) expressed in fetal testis. In cultures of fetal zone and definitive zone cell of human fetal adrenal, 3β-HSD expression was not detected until ACTH was added. ACTH, likely acting in a cyclic AMP-dependent process, induced 3β-HSD type II activity and mRNA expression. The higher level of 3β-HSD mRNA in definitive zone compared with fetal zone cells was associated with parallel increases in cortisol secretion relative to dehydroepiandrosterone sulfate formation.     

Regulated Expression of ADAMTS-12 in Human Trophoblastic Cells: A Role for ADAMTS-12 in Epithelial Cell Invasion?

Metastatic carcinoma cells exploit the same molecular machinery that allows human placental cytotrophoblasts to develop an invasive phenotype. As altered expression levels of ADAMTS (ADisintegrin And Metalloproteinase with ThromboSpondin repeats) subtypes have been associated with cancer progression, we have examined the function and regulation of members of this gene family in epithelial cell invasion using cultures of highly invasive extravillous cytotrophoblasts and the poorly invasive JEG-3 cytotrophoblast cell line as model systems. Of the multiple ADAMTS subtypes identified in first trimester human placenta and these two trophoblastic cell types, only ADAMTS-12 was preferentially expressed by extravillous cytotrophoblasts. Transforming growth factor-β1 and interleukin-1β, two cytokines that promote and restrain cytotrophoblast invasion in vitro, were also found to differentially regulate trophoblastic ADAMTS-12 mRNA levels. Loss- or gain-of-function studies confirmed that ADAMTS-12, independent of its proteolytic activity, plays a specific, non-redundant role in trophoblast invasion. Furthermore, we demonstrated that ADAMTS-12 regulated cell-extracellular matrix adhesion and invasion through a mechanism involving the αvβ3 integrin heterodimer. This study identifies a novel biological role for ADAMTS-12, and highlights the importance and complexity of its non-proteolytic domain(s) pertaining to its function.     

Inhibition of progesterone synthesis in normal and transformed human placental cells by tight binding inhibitors of 3 beta-hydroxysteroid dehydrogenase

The biosynthesis of progesterone from [3H]pregnenolone was curvilinear over a 6 h time course in human placenta cytotrophoblasts and in human placenta choriocarcinoma cells (JEG-3 cells). Mass measurements determined independently by radioimmunoassay indicate that the progesterone synthesized by cytotrophoblasts (21.0 +/- 5.20 ng/6 h/mg protein) is substantially higher than that synthesized by the JEG-3 cells (4.48 +/- 0.56 ng/6 h/mg protein). Two tight binding inhibitors of 3 beta-hydroxysteroid dehydrogenase (2 alpha-cyanoprogesterone I and cyanoketone II), and a potent inhibitor of the microsomal conversion of pregnenolone to progesterone (2 alpha-bromo-5 alpha-androstan-3-one-17 beta-acetate III) were compared as inhibitors of progesterone synthesis in the two cell-types. Compounds I and II were very potent inhibitors yielding IC50 values of between 10 and 20 nM. At higher concentrations (100 nM - 1,000 nM) compound I promoted a complete cessation of progesterone synthesis which could be reversed by washing the cells free of inhibitor. By contrast compound III was ineffectual as an inhibitor yielding an IC50 value greater than 10 microM. This 1,000-fold difference in inhibitory potency suggests that 2 alpha-cyano-substituted steroids display an unusual capacity to inhibit progesterone biosynthesis and secretion in normal and transformed human cells.     

AQP1 gene expression is upregulated by arginine vasopressin and cyclic AMP agonists in trophoblast cells

Aquaporins (AQPs) are water channels that regulate water flow in many tissues. As AQP1 is a candidate to regulate placental fluid exchange, we sought to investigate the effect of arginine vasopressin (AVP) and cAMP agonists on AQP1 gene expression in first trimester-derived extravillous cytotrophoblasts (HTR-8/Svneo) and two highly proliferative carcinoma trophoblast-like cell lines but with a number of functional features of the syncytiotrophoblast namely; JAR and JEG-3 cells. Our data demonstrated that AVP (0.1 nM) significantly increased the expression of AQP1 mRNA at 10 h in HTR-8/SVneo and JEG-3 cells (P<0.05). Both SP-cAMP, a membrane-permeable and phosphodiesterase resistant cAMP, and forskolin, an adenylate cyclase stimulator significantly increased AQP1 mRNA expression in all cell lines after 2 h in a dose-dependent manner (P<0.05) with a parallel increase in protein expression. In the time course study, 5 microM of either SP-cAMP or forskolin significantly stimulated AQP1 mRNA expression after 2 h in HTR-8/SVneo cells and after 10 h in JAR and JEG-3 cells. AQP1 protein expression was highest after 20 h in both HTR-8/SVneo and JEG-3 cells (P<0.05). AVP-stimulated cAMP elevation was blocked in the presence of 9-(tetrahydro-2'-furyl) adenine (SQ22536) (100 microM), a cell-permeable adenylate cyclase inhibitor (P<0.05). These results indicate that in trophoblasts-like cells AQP1 gene expression is upregulated by both AVP and cAMP agonists. Furthermore, our data demonstrate that a cAMP-dependent pathway is responsible for the AVP effect on AQP1. Thus, modulation of AQP1 expression by maternal hormones may regulate invasion and fetal-placental-amnion water homeostasis during gestation.     

Differential regulation of hCG alpha and beta subunit mRNAs in JEG-3 choriocarcinoma cells by 8-bromo-cAMP

The coordinate regulation of human chorionic gonadotropin (hCG) subunit synthesis by JEG-3 choriocarcinoma cells was studied at the pretranslational level. The responses of the hCG alpha and beta mRNAs were measured during stimulation with the potent cAMP analog 8-bromo-cAMP (8-Br-cAMP) using 32P-labeled hCG alpha and beta cDNA probes. The hCG alpha mRNA (850 bases) and beta mRNA (1050 bases) from JEG-3 cells were identical in size to that of their respective mRNAs from placenta, by Northern blot analysis. After 48 h of stimulation with 2 mM 8-Br-cAMP, production of immunoreactive alpha and beta subunits increased 25- and 52-fold, respectively; corresponding levels of the alpha and beta mRNAs increased 36- and 43-fold, respectively, in a dot blot hybridization assay. Total cellular protein, DNA content, and messenger RNA pools were not altered by treatment with 8-Br-cAMP. The temporal coordination of the expression of the hCG alpha- and beta-subunit genes was examined by comparing the time course of stimulation of the respective mRNAs and the production of immunoreactive subunits. The kinetic responses of the alpha and beta mRNAs differed: the increase in hCG alpha mRNA preceded the increase in hCG beta mRNA, while levels of free alpha subunit and intact hCG increased in parallel with the increase in beta mRNA. hCG alpha mRNA levels increased rapidly between 8 and 24 h after the addition of 8-Br-cAMP, and approached a plateau by 48 h. The levels of hCG beta mRNA increased steadily throughout the 8-48 h period. These results demonstrate that the cAMP analog 8-Br-cAMP differentially regulates hCG subunit biosynthesis in JEG-3 cells at a pretranslational level, and that the stimulation by 8-Br-cAMP in this system appears to be relatively selective for hCG subunits.     

alpha-, beta-, gamma-catenin, and p120(CTN) expression during the terminal differentiation and fusion of human mononucleate cytotrophoblasts in vitro and in vivo

The cadherins play key roles in the formation and organization of the mammalian placenta by mediating cellular interactions and the terminal differentiation of trophoblastic cells. Although cadherin function is regulated by the cytoplasmic proteins, known as the catenins, the identity and expression pattern(s) of the catenins present in the trophoblastic cells of the human placenta have not been characterized. In these studies, we have determined that alpha-, beta-, gamma-catenin, and p120(ctn) expression levels are high in villous cytotrophoblasts isolated from the human term placenta but decline as these cells undergo aggregation and fusion to form syncytium with time in culture. In contrast, the expression levels of these four catenin subtypes remained constant in non-fusing JEG-3 choriocarcinoma cells at all of the time points examined in these studies. alpha-, beta-, gamma-catenin, and p120(ctn) expression was further immunolocalized to the mononucleate cells present in these two trophoblastic cell cultures. Similarly, intense immunostaining for all four catenins was detected in the mononucleate villous cytotrophoblasts of the human first trimester placenta. Collectively, these observations demonstrate that the expression levels of alpha-, beta-, gamma-catenin, and p120(ctn) are tightly regulated during the formation of multinucleated syncytium in vitro and in vivo.     

Autophagy in the Human Placenta throughout Gestation

Background

Autophagy has been reported to be essential for pre-implantation development and embryo survival. However, its role in placental development and regulation of autophagy during pregnancy remain unclear. The aims of this study were to (1) study autophagy by characterizing changes in levels of beclin-1, DRAM, and LC3B in human placenta throughout gestation; (2) determine whether autophagy is involved in regulation of trophoblast invasion in JEG-3 cells (a choriocarcinoma cell line); (3) examine the effects of reduced oxygen and glucose on the autophagic changes; and (4) investigate the effect of reoxygenation and supplementation of glucose after oxygen-glucose deprivation (OGD) on the autophagic changes in primary cytotrophoblasts obtained from normal term pregnancy.

Methodology/Principal Findings

An analysis of 40 placental samples representing different gestational stages showed (1) no significant differences in beclin-1, DRAM, and LC3B-II levels in placentas between early and mid-gestation, and late gestation with vaginal delivery; (2) placentas from late gestation with cesarean section had lower levels of LC3B-II compared to early and mid-gestation, and late gestation with vaginal delivery; levels of DRAM were also lower compared to placentas from early and mid-gestation; and (3) using explant cultures, villous tissues from early and late gestation had similar rates of autophagic flux under physiological oxygen concentrations. Knockdown of BECN1, DRAM, and LC3B had no effects on viability and invasion activity of JEG-3 cells. On the other hand, OGD caused a significant increase in the levels of LC3B-II in primary cytotrophoblasts, while re-supplementation of oxygen and glucose reduced these changes. Furthermore, there were differential changes in levels of beclin-1, DRAM, and LC3B-II in response to changes in oxygen and glucose levels.

Conclusions/Significance

Our results indicate that autophagy is involved in development of the human placenta and that changes in oxygen and glucose levels participate in regulation of autophagic changes in cytotrophoblast cells.     

Cell type-specific regulation of fetal fibronectin expression in amnion: conservation of glucocorticoid responsiveness in human and nonhuman primates

The appearance of oncofetal fibronectin (FFN) in cervical and vaginal secretions is predictive of human labor. Levels of FFN in amnion increase with the onset of labor in rhesus monkeys. Since glucocorticoid (GC) levels in serum and amniotic fluid increase in association with parturition, we compared GC-mediated regulation of FFN expression in cultures of amnion epithelial cells and fibroblasts isolated from human and baboon amnions. Cells were maintained with and without dexamethasone (DEX), and levels of FFN in the conditioned media were determined by ELISA. We observed that DEX treatment suppressed FFN levels in both human and baboon amnion epithelial cells, whereas it increased FFN levels in amnion fibroblasts. DEX treatment reduced FFN levels in cytotrophoblasts from human placenta and increased FFN levels in placental fibroblasts. Northern blots revealed that DEX reduced levels of fibronectin (FN) mRNA in amnion epithelial cells and cytotrophoblasts, whereas it increased FN mRNA in amnion and placental fibroblasts. We conclude that GC differentially regulates FFN expression in epithelial and mesenchymal cells from amnion and placenta. In addition, this pattern of cell type-specific FFN regulation by GC is conserved in human and nonhuman primates and may be responsible for parturition-dependent changes in FFN expression in gestational tissues.     

Death receptor Fas/Apo-1/CD95 expressed by human placental cytotrophoblasts does not mediate apoptosis

Trophoblasts, the fetal cells that line the villous placenta and separate maternal blood from fetal tissue, express both Fas antigen and the tumor necrosis factor (TNF) receptor p55 (TNFRp55), two members of the TNF receptor family that contain a cytoplasmic "death domain" that mediates apoptotic signals. We show that Fas mRNA expressed by cultured villous cytotrophoblasts isolated from term placentas encodes transmembrane sequences and that the protein is full-length (approximately 45 kDa), suggesting that the product is an active plasma membrane-anchored receptor. Its location on the cell surface was confirmed by cellular ELISA analysis of live cells. Although cytotrophoblast apoptosis was induced by TNFalpha, and both anti-Fas antibody (CH11) and FasL-expressing T lymphocyte hybridoma (activated A1.1) cells induced HeLa cell apoptosis, neither CH11 antibody nor activated A1.1 cells stimulated apoptosis in term or first-trimester cytotrophoblasts or in term syncytiotrophoblasts. We conclude that Fas- but not TNFRp55-mediated apoptosis is blocked in primary villous trophoblasts. These data suggest that the Fas response is specifically inactivated by unknown mechanisms to avoid autocrine or paracrine killing by Fas ligand constitutively expressed on neighboring cyto- or syncytiotrophoblasts.     

hCG对绒癌细胞系MMP-2和MMP-8表达的影响

为了探讨人绒毛膜促性腺激素（hCG)对绒并且吕细胞侵袭性相关基因表达的影响作用。采用逆转录多聚酶链反应（RT-PCR）检测方法,观察了不同浓度hCG不同处理时间对JEG-3绒癌细胞系表达基质金属蛋白酶（MMP-2和MMP-8）的影响。结果显示,绒癌细胞系JEG-3表达MMP-2和MMP-8;分别用0、50、500、5000、25000IU/LhCG处理48h后,JEG-3细胞中MMP-2mRNA的含量无明显变化。MMP-8mRNA的表达则被诱导,并随hCG作用浓度增高而增强,进一步研究处理时间对MMP表达的影响。结果发现经25000IU/LhCG处理的JEG-3细胞,MMP-8的表达随处理时间的延长逐渐增强,而MMP-2的表达则在第6h被显著诱导后逐渐降低,以上结果提示,hCG可诱导绒癌细胞系JEG-3中MMP-2和MMP-8两种基质金属蛋白酶的表达,并因此可能对绒癌细胞系的侵袭性具有影响作用。然而hCG对这两者表达的影响规律并不完全一致。     

Unscheduled DNA synthesis in primary cultures of human placentae.

Ultraviolet light-induced unscheduled DNA synthesis in primary cultures of human placentae examined as a function of radiation-dose and repair-incubation period was found to be dependent upon cell type and independent of gestational age. Primary cultures obtained by continuous harvesting of enzymatically released cells from fragments of 11-week and term specimens contained cytotrophoblasts and fibroblasts. Fibroblasts exhibited 3-fold more repair than did cytotrophoblasts from the same organ at both 11 weeks and term.