Placental steroid hormones

Transcriptomic and histochemical analysis reveal the complex regulatory networks in equine Chorioallantois during spontaneous term labor

The equine chorioallantois (CA) undergoes complex physical and biochemical changes during labor. However, the molecular mechanisms controlling these changes are still unclear. Therefore, the current study aimed to characterize the transcriptome of equine CA during spontaneous labor and compare it to that of normal preterm CA. Placental samples were collected postpartum from mares with normal term labor (TL group, n = 4) and from preterm not in labor mares (330 days GA; PTNL group, n = 4). Our study identified 4137 differentially expressed genes (DEGs) (1820 upregulated and 2317 downregulated) in CA during TL as compared to PTNL. TL was associated with the upregulation of several pro-inflammatory mediators (MHC-I, MHC-II, NLRP3, CXCL8, and MIF). Also, TL was associated with the upregulation of matrix metalloproteinase (MMP1, MMP2, MMP3, and MMP9) with subsequent extracellular matrix degradation and apoptosis, as reflected by upregulation of several apoptosis-related genes (ATF3, ATF4, FAS, FOS, and BIRC3). In addition, TL was associated with downregulation of 21 transcripts coding for collagens. The upregulation of proteases, along with the downregulation of collagens, is believed to be implicated in separation and rupture of the CA during TL. Additionally, TL was associated with downregulation of transcripts coding for proteins essential for progestin synthesis (SRD5A1 and AKR1C1) and angiogenesis (VEGFA and RTL1), as well as upregulation of prostaglandin synthesis-related genes (PTGS2 and PTGES), which could reflect the physiological switch in placental endocrinology and function during TL. In conclusion, our findings revealed the equine CA gene expression signature in spontaneous labor at term, which improves our understanding of the molecular mechanisms triggering labor.

Influence of Low Protein Diet-Induced Fetal Growth Restriction on the Neuroplacental Corticosterone Axis in the Rat

Objectives: Placental steroid metabolism is linked to the fetal hypothalamus-pituitary-adrenal axis. Intrauterine growth restriction (IUGR) might alter this cross-talk and lead to maternal stress, in turn contributing to the pathogenesis of anxiety-related disorders of the offspring, which might be mediated by fetal overexposure to, or a reduced local enzymatic protection against maternal glucocorticoids. So far, direct evidence of altered levels of circulating/local glucocorticoids is scarce. Liquid chromatography tandem-mass spectrometry (LC-MS/MS) allows quantitative endocrine assessment of blood and tissue. Using a rat model of maternal protein restriction (low protein [LP] vs. normal protein [NP]) to induce IUGR, we analyzed fetal and maternal steroid levels via LC-MS/MS along with the local expression of 11beta-hydroxysteroid-dehydrogenase (Hsd11b). Methods: Pregnant Wistar dams were fed a low protein (8%, LP; IUGR) or an isocaloric normal protein diet (17%, NP; controls). At E18.5, the expression of Hsd11b1 and 2 was determined by RT-PCR in fetal placenta and brain. Steroid profiling of maternal and fetal whole blood, fetal brain, and placenta was performed via LC-MS/MS. Results: In animals with LP-induced reduced body (p < 0.001) and placental weights (p < 0.05) we did not observe any difference in the expressional Hsd11b1/2-ratio in brain or placenta. Moreover, LP diet did not alter corticosterone (Cort) or 11-dehydrocorticosterone (DH-Cort) levels in dams, while fetal whole blood levels of Cort were significantly lower in the LP group (p < 0.001) and concomitantly in LP brain (p = 0.003) and LP placenta (p = 0.002). Maternal and fetal progesterone levels (whole blood and tissue) were not influenced by LP diet. Conclusion: Various rat models of intrauterine stress show profound alterations in placental Hsd11b2 gatekeeper function and fetal overexposure to corticosterone. In contrast, LP diet in our model induced IUGR without altering maternal steroid levels or placental enzymatic glucocorticoid barrier function. In fact, IUGR offspring showed significantly reduced levels of circulating and local corticosterone. Thus, our LP model might not represent a genuine model of intrauterine stress. Hypothetically, the observed changes might reflect a fetal attempt to maintain anabolic conditions in the light of protein restriction to sustain regular brain development. This may contribute to fetal origins of later neurodevelopmental sequelae.

Steroidogenic enzyme activities in the pre- and post-parturient equine placenta

Steroidogenic enzymes in placentas shape steroid hormone profiles in the maternal circulation of each mammalian species. These include 3β-hydroxysteroid dehydrogenase/Δ5-4 isomerase (3βHSD) and 17α-hydroxylase/17,20-lyase cytochrome P450 (P450c17) crucial for progesterone and androgen synthesis, respectively, as well as aromatase cytochrome P450 (P450arom) that converts Δ4-androgens to estrogens. 5α-reductase is another important enzyme in equine placentas because 5α-dihydroprogesterone (DHP) sustains pregnancy in the absence of progesterone in the second half of equine pregnancy. DHP and its metabolites decline dramatically days before foaling, but few studies have investigated placental enzyme activity before or at parturition in mares. Thus, key enzyme activities and transcript abundance were investigated in equine placentas at 300 days of gestation (GD300) and post-partum (term). Equine testis was used as a positive control for P450c17 activity. Substrates were incubated with microsomal preparations, together with enzyme inhibitors, and products were measured by liquid chromatography tandem mass spectrometry or radiometric methods (aromatase). Equine placenta expressed high levels of 3βHSD, 5α-reductase and aromatase, and minimal P450c17 activity at GD300 compared with testis (600-fold higher). At foaling, 3βHSD and aromatase activities and transcript abundance were unchanged but 5α-reductase (and P450c17) was no longer detectable (P < 0.05) and transcript was decreased. Trilostane inhibited 3βHSD significantly more in testis than placenta, suggesting possible existence of different 3βHSD isoforms. Equine placentas have significant capacity for steroid metabolism by 5α-reductase, 3βHSD and aromatase but little for androgen synthesis lacking P450c17. Declining pre-partum 5α-reduced pregnane concentrations coincide with selective loss of placental 5α-reductase activity and expression at parturition in horses.

Equine fetal adrenal, gonadal and placental steroidogenesis

Equine fetuses have substantial circulating pregnenolone concentrations and thus have been postulated to provide significant substrate for placental 5α-reduced pregnane production, but the fetal site of pregnenolone synthesis remains unclear. The current studies investigated steroid concentrations in blood, adrenal glands, gonads and placenta from fetuses (4, 6, 9 and 10 months of gestational age (GA)), as well as tissue steroidogenic enzyme transcript levels. Pregnenolone and dehydroepiandrosterone (DHEA) were the most abundant steroids in fetal blood, pregnenolone was consistently higher but decreased progressively with GA. Tissue steroid concentrations generally paralleled those in serum with time. Adrenal and gonadal tissue pregnenolone concentrations were similar and 100-fold higher than those in allantochorion. DHEA was far higher in gonads than adrenals and progesterone was higher in adrenals than gonads. Androstenedione decreased with GA in adrenals but not in gonads. Transcript analysis generally supported these data.CYP17A1was higher in fetal gonads than adrenals or allantochorion, andHSD3B1was higher in fetal adrenals and allantochorion than gonads.CYP11A1transcript was also significantly higher in adrenals and gonads than allantochorion andCYP19and SRD5A1 transcripts were higher in allantochorion than either fetal adrenals or gonads. Given these data, and their much greater size, the fetal gonads are the source of DHEA and likely contribute more than fetal adrenal glands to circulating fetal pregnenolone concentrations. LowCYP11A1but highHSD3B1andSRD5A1transcript abundance in allantochorion, and low tissue pregnenolone, suggests that endogenous placental pregnenolone synthesis is low and likely contributes little to equine placental 5α-reduced pregnane secretion.

Plasma steroid dynamics in late- and near-term naturally and artificially conceived bovine pregnancies as elucidated by multihormone high-resolution LC-MS/MS

The plasma levels of corticosteroids and sex steroids during pregnancy are key indicators of mammalian placental function and the onset of parturition. Steroid hormones are believed to be disturbed in pregnancies produced using assisted reproductive technologies (ARTs) due to placental dysfunction and the frequently observed lack of parturition signals. To elucidate the plasma steroid dynamics, a liquid chromatography-tandem mass spectrometry method was developed and used to determine the levels of corticosteroids (corticosterone, 11-deoxycortisol, and cortisol) and their direct precursors (progesterone and 17α-OH-progesterone) as well as sex steroids (androstenedione, estrone, estrone sulfate, testosterone, and 17β-estradiol) in bovine plasma. The levels of these 10 steroids in recipient cows carrying naturally conceived (control), in vitro fertilized (IVF), or cloned (somatic cell nuclear transfer) conceptuses were compared during late-term pregnancy (30 days before parturition), during near-term pregnancy (1 day before parturition), and on the day of parturition (day 0). Significant differences were observed among the corticosteroid levels: higher levels of corticosterone, 11-deoxycortisol, and cortisol were detected in cloned pregnancies at day 30; lower levels of corticosterone were observed in ART-derived pregnancies at days 1 and 0; and estrone and estradiol levels were higher in IVF pregnancies throughout the final development. These results suggested an upregulation of the P450C11 and P450C21 enzymes 30 days before parturition in somatic cell nuclear transfer pregnancies and an overactivation of the aromatase enzyme in IVF pregnancies. Taken together, the monitoring of multiple steroid hormones revealed that the pregnancies obtained using ART exhibited plasma steroid concentration dynamics compatible with the dysregulation of steroidogenic tissues.

In ovo inhibition of steroid metabolism by bisphenol-A as a potential mechanism of endocrine disruption

During embryonic development, endogenous signals, for example steroid hormones, and exogenous signals, for example endocrine disrupting chemicals (EDCs), have the capacity to produce phenotypic effects that persist into adulthood. As the actions of steroids are mediated through the binding of steroid receptors, most studies of EDCs have assumed that they too elicit their effects by binding steroid receptors. We tested an alternative hypothesis, namely that EDCs elicit their effects during embryonic development by disrupting the metabolism of maternally derived steroids, thereby allowing maternally derived steroids to bind steroid receptors and elicit effects. Specifically, we examined the ability of the EDC, bisphenol-A (BPA) to inhibit the normal metabolism of oestradiol during the first nine days of embryonic development in the red-eared slider turtle (Trachemys scripta). We found that, when BPA was present, oestrogen metabolism was inhibited when compared to control eggs. In particular, the formation of oestrone sulfate was blocked in BPA-treated eggs. We postulate that the oestrogenic effects of EDCs may be driven, at least in part, by inappropriate oestrogen signalling. The retention of oestrogens at points of development when they would normally be metabolized to inactive forms might also help explain low-dose effects frequently reported for EDCs.

Sulfonation of maternal steroids is a conserved metabolic pathway in vertebrates

All vertebrate embryos develop in the presence of maternally derived steroids, and maternal steroids have been hypothesized to link phenotype of the offspring to maternal physiology. In placental vertebrates, it is known that maternally derived steroids are metabolized during development via the sulfonation pathway. We used eggs from the red-eared slider turtle (Trachemys scripta) to determine whether the same metabolic pathway is used to metabolize maternally derived steroids in an oviparous vertebrate. To examine the relationship between estradiol and estrogen sulfates during development, levels of maternally derived estradiol were compared with levels of estradiol sulfate, estrone sulfate, and estriol sulfate at oviposition and after 20 days of embryonic development. Estrone sulfate was the only detectable estrogen sulfate. At oviposition, levels of both estradiol and estrone sulfate varied seasonally with clutches from later in the nesting season having significantly higher concentrations of both steroids. Levels of estrone sulfate increased during development, demonstrating that the sulfonation of maternally derived steroids occurs in oviparous vertebrates as well as in placental vertebrates. We also found that exogenous estrone sulfate increases the production of female hatchlings, thereby demonstrating the ability of this metabolite to influence embryonic development. To examine the role of sulfonation in the metabolism of maternal progesterone and testosterone, we characterized the metabolic fate of both steroids by applying tritiated forms of each steroid at oviposition and characterizing metabolites after 20 days of incubation. Similar to what was demonstrated for estradiol, both progesterone and testosterone are converted to sulfonated metabolites during embryonic development. These data suggest that steroid sulfates, both those that are maternally derived and those resulting from the metabolism of maternal steroids, are a key component of the mechanism underlying steroid-mediated maternal effects.

Bioengineering anembryonic human trophoblast vesicles

INTRODUCTION

Trophoblast cells in vivo form a 3-dimensional structure that promotes complex cell-to-cell interactions that cannot be studied with traditional monolayer culture. We describe a 3-dimensional trophoblast bioreactor to study cellular interactions.

METHODS

Nonadhesive agarose hydrogels were cast from molds using computer-assisted prototyping. Trophoblast cells were seeded into the gels for 10 days. Morphology, viability, and vesicle behavior were assessed.

RESULTS

Trophoblast cells formed uniform spheroids. Serial sectioning on days 3, 7, and 10 revealed central vacuolization with a consistent outer rim 12.3-μ thick. The vesicle configuration has been confirmed with confocal imaging. Electron Microscopic (EM) imaging revealed its ultrastructure. The vesicles migrate across a fibronectin-coated surface and invaded basement membrane.

CONCLUSIONS

Trophoblast cells cultured in a novel substrate-free 3-dimensional system form trophoblast vesicles. This new cell culture technique allows us to better study placental cell-to-cell interactions with the potential of forming microtissues.

Placental ABCA1 and ABCG1 transporters efflux cholesterol and protect trophoblasts from oxysterol induced toxicity

ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 mediate the efflux of cholesterol and other sterols. Both transporters are expressed on the fetal capillaries of the placenta and are involved in maternal-to-fetal cholesterol delivery. In this study, we report that ABCA1 and ABCG1 are also present on the syncytiotrophoblast, the maternal facing placental membrane. Syncytial ABCA1 expression is apical, suggesting a role in cholesterol efflux to the mother, while ABCG1 is expressed basolaterally indicating transport to the fetus. Silencing of ABCA1 expression in primary trophoblasts in culture, or pharmacological antagonism by glyburide, decreased cholesterol efflux to apolipoprotein A-I (apoA-I) compared to controls, while ABCG1-silencing decreased cholesterol efflux to high density lipoproteins (HDL). In contrast, treatment with endogenous or synthetic LXR alpha/beta ligands such as T0901317 increased ABCA1 and ABCG1 expression and enhanced cholesterol efflux to apoA-I and HDL, respectively, while treatment with pharmacological PPAR-alpha or -gamma ligands was without effect. Trophoblasts transfected with ABCA1 or ABCG1 siRNA were more sensitive to toxic oxysterols substrates (25-hydroxycholesterol and 7-ketocholesterol) compared to mock-transfected cells, while prior treatment with T0901317 reduced oxysterol-mediated toxicity. These results identify syncytial ABCA1 and ABCG1 as important, inducible cholesterol transporters which also prevent placental accumulation of cytotoxic oxysterols.

Cellular cholesterol delivery, intracellular processing and utilization for biosynthesis of steroid hormones

Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function and various metabolic processes. They are synthesized from cholesterol mainly in the adrenal gland and gonads in response to tissue-specific tropic hormones. These steroidogenic tissues are unique in that they require cholesterol not only for membrane biogenesis, maintenance of membrane fluidity and cell signaling, but also as the starting material for the biosynthesis of steroid hormones. It is not surprising, then, that cells of steroidogenic tissues have evolved with multiple pathways to assure the constant supply of cholesterol needed to maintain optimum steroid synthesis. The cholesterol utilized for steroidogenesis is derived from a combination of sources: 1) de novo synthesis in the endoplasmic reticulum (ER); 2) the mobilization of cholesteryl esters (CEs) stored in lipid droplets through cholesteryl ester hydrolase; 3) plasma lipoprotein-derived CEs obtained by either LDL receptor-mediated endocytic and/or SR-BI-mediated selective uptake; and 4) in some cultured cell systems from plasma membrane-associated free cholesterol. Here, we focus on recent insights into the molecules and cellular processes that mediate the uptake of plasma lipoprotein-derived cholesterol, events connected with the intracellular cholesterol processing and the role of crucial proteins that mediate cholesterol transport to mitochondria for its utilization for steroid hormone production. In particular, we discuss the structure and function of SR-BI, the importance of the selective cholesterol transport pathway in providing cholesterol substrate for steroid biosynthesis and the role of two key proteins, StAR and PBR/TSO in facilitating cholesterol delivery to inner mitochondrial membrane sites, where P450scc (CYP11A) is localized and where the conversion of cholesterol to pregnenolone (the common steroid precursor) takes place.

Delivery of cloned offspring: experience in Zebu cattle (Bos indicus)

The production of a healthy cloned calf is dependent on a multitude of successful steps, including reprogramming mediated by the oocyte, the development of a functional placenta, adequate maternal–fetal interaction, the establishment of a physiological metabolic setting and the formation of a complete set of well-differentiated cells that will eventually result in well-characterised and fully competent tissues and organs. Although the efficiency of nuclear transfer has improved significantly since the first report of a somatic cell nuclear transfer-derived animal, there are many descriptions of anomalies concerning cloned calves leading to high perinatal morbidity and mortality. The present article discusses some our experience regarding perinatal and neonatal procedures for cloned Zebu cattle (B. indicus) that has led to improved survival rates in Nellore cloned calves following the application of such ‘labour-intensive technology’.

Organization of cytochrome P450 enzymes involved in sex steroid synthesis: PROTEIN-PROTEIN INTERACTIONS IN LIPID MEMBRANES

Mounting evidence underscores the importance of protein-protein interactions in the functional regulation of drug-metabolizing P450s, but few studies have been conducted in membrane environments, and none have examined P450s catalyzing sex steroid synthesis. Here we report specific protein-protein interactions for full-length, human, wild type steroidogenic cytochrome P450 (P450, CYP) enzymes: 17alpha-hydroxylase/17,20-lyase (P450c17, CYP17) and aromatase (P450arom, CYP19), as well as their electron donor NADPH-cytochrome P450 oxidoreductase (CPR). Fluorescence resonance energy transfer (FRET)(3) in live cells, coupled with quartz crystal microbalance (QCM), and atomic force microscopy (AFM) studies on phosphatidyl choline +/- cholesterol (mammalian) biomimetic membranes were used to investigate steroidogenic P450 interactions. The FRET results in living cells demonstrated that both P450c17 and P450arom homodimerize but do not heterodimerize, although they each heterodimerize with CPR. The lack of heteroassociation between P450c17 and P450arom was confirmed by QCM, wherein neither enzyme bound a membrane saturated with the other. In contrast, the CPR bound readily to either P450c17- or P450arom-saturated surfaces. Interestingly, N-terminally modified P450arom was stably incorporated and gave similar results to the wild type, although saturation was achieved with much less protein, suggesting that the putative transmembrane domain is not required for membrane association but for orientation. In fact, all of the proteins were remarkably stable in the membrane, such that high resolution AFM images were obtained, further supporting the formation of P450c17, P450arom, and CPR homodimers and oligomers in lipid bilayers. This unique combination of in vivo and in vitro studies has provided strong evidence for homodimerization and perhaps some higher order interactions for both P450c17 and P450arom.

Trophoblast infiltration

Sexual reproduction in the ocean necessitates only the combination of gametes, followed by absorption of nutrients and oxygen from the surrounding watery medium. As life moved from the sea to the land, reproductive strategies required compensation for the loss of this aquatic environment. For the mammals, and scattered other animals, the solution to this problem was the development of the placenta, the means by which the fetus extracts nutrients from its environment. As the animals that utilized the placenta evolved from small rodent-like creatures with short gestations to larger animals with prolonged gestations, the demands of the developing fetus grew. Whereas the placenta of the fetal pig, with a gestational period of a little less than four months, can extract sufficient nutrients from the mother by simple diffusion across the uterus to the placenta, the human fetus needs a far more complex uteroplacental relationship.

Oxygen tension directs the differentiation pathway of human cytotrophoblast cells

During placental development, human cytotrophoblast cells can differentiate to either villous syncytiotrophoblast cells or invasive extravillous trophoblast cells. We hypothesize that oxygen tension plays a critical role in determining the pathway of cytotrophoblast differentiation. A highly purified preparation of cytotrophoblast cells from human third trimester placenta was cultured for 5 days in either 20% or 1% oxygen tension. The cells incubated at 20% oxygen formed a syncytium as determined by immunohistochemistry using an anti-desmosomal protein antibody that identifies cell membranes. In addition, the mRNA was markedly induced for syncytin, a glycoprotein shown to be essential for syncytiotrophoblast formation, and for human placental lactogen (hPL), which is a specific marker for syncytiotrophoblast cells. In contrast, the cell incubated at 1% oxygen tension did not fuse by morphologic analysis and did not express syncytin or hPL mRNA. However, these cells expressed abundant amounts of HLA-G, a specific marker for extravillous trophoblast cells, which was not seen in cells incubated at 20% oxygen tension. These results suggest that low oxygen tension directs differentiation along the extravillous trophoblast cell pathway while greater oxygen tension directs differentiation along the villous trophoblast cell pathway.

Expression of 3β-hydroxysteroid dehydrogenase type 1, P450 aromatase, and 17β-hydroxysteroid dehydrogenase types 1, 2, 5 and 7 mRNAs in human early and mid-gestation placentas

The placenta is responsible for the production of progesterone (P) and estrogens during human pregnancy. In this study, the expression of several key steroidogenic enzymes was investigated in different cell types of human placenta during early and mid-gestation by in situ hybridization. 3Beta-hydroxysteroid dehydrogenase type 1 (3beta-HSD1), P450 aromatase (P450arom) and 17beta-hydroxysteroid dehydrogenase type 1 (17HSD1) were expressed abundantly in syncytiotrophoblast (ST) cells. These three enzymes were also detected in some column cytotrophoblast (CCT) cells. 17HSD5 was found in intravillous stromal (IS) cells in low levels, suggesting that androgens may be synthesized and metabolized in the placenta. 17HSD7 was found in all types of placental cells. Moreover, 17HSD2 was localized in IS cells. The expression level of 17HSD2 gradually increased during pregnancy weeks 7-16, concurrently with the androgen production by the male fetus. The present study provides evidence that CCT and IS cells participate in P and estrogen biosynthesis, in addition to ST cells. 17HSD2 also converts 20alpha-dihydroprogesterone (20-OH-P) to P, whereas 17HSD5 and 17HSD7 inactivate P. Therefore, the action of 3beta-HSD1 and 17HSD2 on P biosynthesis in the placenta is countered by 17HSD5 and 17HSD7, which may provide an optimal level of P for the maintenance and progression of pregnancy.

Cattle and sheep use different promoters to direct the expression of the aromatase cytochrome P450 encoding gene, Cyp19, during pregnancy

Gestagens and oestrogens are important regulators of pregnancy and parturition. The aim of the present study was the comparative quantification of steroidogenic transcripts in placenta and corpus luteum of cattle and sheep during pregnancy and post partum. Cyp19 transcript variants, derived from different promoters, as well as transcripts of Hsd3b, Cyp11A1, and Cyp17, encoding the steroidogenic enzymes P450arom, 3beta-HSD, P450SCC, and P450C17, respectively, were quantified by newly developed real-time PCR assays. All steroidogenic transcripts were detected in ovine and bovine corpus luteum and placenta during pregnancy, however at a very different concentration. In both species Cyp11A1 and especially Hsd3b transcripts predominated in corpus luteum, outnumbering transcripts of Cyp17 and Cyp19 by more than two and three orders of magnitude, respectively. Cyp19 transcript were found at high concentration in the placenta and at a very low concentration in corpus luteum. Cyp17 transcripts had a relatively low concentration in both, placenta and corpus luteum, however showed a peak of expression in the ovine and bovine term placenta. Tissue- and species-specific Cyp19 transcripts derived from different promoters were detected. In order to map all promoters, the bovine Cyp19 locus was reconstructed by in silico analysis. In the placenta, transcripts were primarily derived from the proximal promoter P1.5 in sheep, but from the distally located P1.1 in cattle. Corpora lutea of both species predominantly expressed P1.1 derived transcripts. Contrary to the bovine, the sheep corpus luteum also showed considerable P1.5 derived expression. This demonstrates that cattle and sheep use different promoters to direct Cyp19 expression during pregnancy.

Uterine and placental expression of steroidogenic genes during rodent pregnancy

The ontogeny and functional role of steroidogenesis during mammalian gestation is poorly understood. This review provides a summary of our recent findings on the spatio-temporal expression of key steroidogenic genes controlling progesterone synthesis in the uterus during mouse pregnancy. We have shown that onset of cholesterol side chain cleavage cytochrome P450 (P450scc) and a newly identified isoform of murine 3beta-hydroxysteroid dehydrogenase/isomerase type VI (3betaHSD VI) expression occurs upon decidualization of the uterine wall induced by implantation. This unexpected early expression of the enzymes in the maternal decidua is terminated at mid-pregnancy when the steroidogenic ability reappears in the extraembryonic giant cells at the time of placentation. The giant cells express another protein indispensable for steroid hormone synthesis in the adrenal and gonads, Steroidogenic Acute Regulatory (StAR) protein. Unlike the human placenta, the steroidogenic genes are not expressed in the cells of the mature mouse placenta during the second half of gestation. Finally, our studies suggest that transcriptional regulation of P450scc is mediated by a non-SF-1 protein that substitutes SF-1 functions in the extraembryonic cells. Collectively, the results of the present study suggest that, during early phases of pregnancy, local progesterone synthesis in the maternal decidua and the trophoblast layers surrounding the embryonal cavity is important for successful implantation and/or maintenance of pregnancy. We propose that the local production of progesterone acts as an immunosuppressant at the maternofetal interface preventing the rejection of the fetal allograft.

Bluetongue and equine viral arteritis viruses as models of virus-induced fetal injury and abortion

A number of viruses have the capacity to cross the placenta and infect the fetus to cause, among other potential outcomes, developmental defects (teratogenesis), fetal death and abortion. Bluetongue virus (BTV) infection of fetal ruminants provides an excellent model for the study of virus-induced teratogenesis. This model has shown that only viruses modified by passage in cell culture, such as modified live virus vaccine strains, readily cross the ruminant placenta, and that the timing of fetal infection determines the outcome. Thus, cerebral malformations only occur after fetal infection at critical stages during development and the precise timing of fetal BTV infection determines the severity of the malformation present at birth. Fetal BTV infection also can result in fetal death, followed by abortion or resorption, growth retardation, or no obvious abnormalities, depending on age of the conceptus at infection. Equine arteritis virus (EAV) infection of the equine fetus causes fetal death and abortion but not teratogenesis. These two fetal viral infections are useful not only for the study of teratogenesis and fetal disease, but also to further characterize and compare the complex process that is responsible for normal induction of parturition in ruminants and horses.

Retinoic acids increase 17 beta-hydroxysteroid dehydrogenase type 1 expression in JEG-3 and T47D cells, but the stimulation is potentiated by epidermal growth factor, 12-O-tetradecanoylphorbol-13-acetate, and cyclic adenosine 3',5'-monophosphate only in JEG-3 cells

Human 17 beta-hydroxysteroid dehydrogenase type 1 (17HSD type 1) primarily catalyzes the reduction of low activity estrone to high activity estradiol in ovarian granulosa cells and placental trophoblasts 17HSD type 1 is also present in certain peripheral tissues, such as breast tissue. In the present study we investigated the effects of retinoic acids (RAs) together with other stimuli known to modulate estradiol production and/or cell growth on expression of 17HSD type 1 in JEG-3 choriocarcinoma cells and estrogen-responsive T47D breast cancer cells. Treatment of cultured JEG-3 and T47D cells with all-trans-RA and 9-cis-RA increased reductive 17HSD activity and 17HSD type 1 messenger RNA expression severalfold in both cell lines. On the other hand, epidermal growth factor (EGF), Ca ionophore, the protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA), and cAMP elevated 17HSD type 1 expression only in JEG-3 cells. Correspondingly, the effects of RAs were potentiated by EGF, TPA, and cAMP in JEG-3 cells, whereas no such phenomenon was observed in T47D cells. In JEG-3 cells, simultaneous administration of RAs with TPA and EGF maximally resulted in approximately 40- and 20-fold increases in 17HSD type 1 messenger RNA expression, respectively. The present data indicate that RAs may stimulate estradiol biosynthesis by regulating 17HSD type 1 expression in certain breast cancer and choriocarcinoma cells. The results suggest that interaction of multiple regulatory pathways is involved in maintaining high 17HSD type 1 expression in the placenta. In addition, regulation of 17HSD type 1 expression may be different in trophoblast cells from that in breast epithelial cells.

Characterization of 17 beta-hydroxysteroid dehydrogenase type 1 in choriocarcinoma cells: regulation by basic fibroblast growth factor

17 beta-Hydroxysteroid dehydrogenase type 1 (17-HSD type 1) is a steroidogenic enzyme catalyzing reversible interconversion of estradiol and estrone. 17-HSD type 1 is actively expressed in human placenta. We characterized 17-HSD type 1 expression and its regulation by basic fibroblast growth factor (bFGF) in JAR, JEG-3 and BeWo choriocarcinoma cell lines. Based on Southern and Northern analysis, as well as measurement of catalytic activity and immunoreactive protein, all the choriocarcinoma cell lines contained and expressed the gene coding for 17-HSD type 1, identical to that of normal human cells. However, the cell lines showed marked quantitative differences in the levels of expression of the enzyme, being lowest in JAR cells and highest in BeWo cells, as measured by immunofluorometric assay, Northern analysis and catalytic activity. These differences in the basal level of expression were most probably not based on any sequence differences in the putative proximal promoter area of the gene in different cell lines, since no dissimilarities were observed in the 806 bp region upstream from the transcription start site of 1.3 kb mRNA coding for 17-HSD type 1 except for frequent polymorphism characteristic of normal human cells using polymerase chain reaction/single-strand conformation polymorphism (PCR-SSCP) analysis. The reductive (estrone-->estradiol) activity was about 4-7 times higher compared with the oxidative activity (estradiol-->estrone) in all the cell lines studied, indicating that in these choriocarcinoma cell lines, 17-HSD activity favours estradiol formation.(ABSTRACT TRUNCATED AT 250 WORDS)