Differential synthesis of human placental lactogen and human chorionic gonadotropin in vitro

Expression of endometrial immune-related genes possibly functioning during early pregnancy in the mare

Despite enormous efforts, biochemical and molecular mechanisms associated with equine reproduction, particularly processes of pregnancy establishment, have not been well characterized. Previously, PCR-selected suppression subtraction hybridization analysis was executed to identify unique molecules functioning in the equine endometrium during periods of pregnancy establishment, and granzyme B (GZMB) cDNA was found in the pregnant endometrial cDNA library. Because GZMB is produced from natural killer (NK) cells, endometrial expression of GZMB and immune-related transcripts were characterized in this study. The level of GZMB mRNA is higher in the pregnant endometrium than in non-pregnant ones. This expression was also confirmed through Western blot and immunohistochemical analyses. IL-2 mRNA declined as pregnancy progressed, while IL-15, IFNG and TGFB1 transcripts increased on day 19 and/or 25. Analyses of IL-4 and IL-12 mRNAs demonstrated the increase in these transcripts as pregnancy progressed. Increase in CCR5 and CCR4 mRNAs indicated that both Th1 and Th2 cells coexisted in the day 25 pregnant endometrium. Taken together, the endometrial expression of immune-related transcripts suggests that immunological responses are present even before the trophectoderm actually attaches to the uterine epithelial cells.

Innate and adaptive immunity in female genital tract: cellular responses and interactions

The mucosal immune system in the female reproductive tract (FRT) has evolved to meet the unique requirements of dealing with sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and the immunologically distinct fetus. Analysis of the FRT indicates that the key cells of the innate and adaptive immune systems are present and functionally responsive to antigens. Acting through Toll-like receptors in the Fallopian tubes, uterus, cervix, and in the vagina, epithelial cells, macrophages, natural killer cells, and neutrophils confer protection through the production of chemokines and cytokines, which recruit and activate immune cells, as well as bactericidal and virucidal agents, which confer protection at times when adaptive immunity is downregulated by sex hormones to meet the constraints of procreation. The overall goal of this paper is to define the innate immune system in the FRT and, where possible, to define the regulatory influences that occur during the menstrual cycle that contribute to protection from and susceptibility to potential pathogens. By understanding the nature of this protection and the ways in which innate and adaptive immunity interact, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

Human macrophage colony-stimulating factor induces the differentiation of trophoblast

When human cytotrophoblastic cells in the early stage of pregnancy were cultured in a serum-free medium in the presence of human macrophage colony-stimulating factor (M-CSF), the cytotrophoblastic cells fused and formed a typical syncytiotrophoblast which had a dense distribution of microvilli revealed under an electron microscope. On the other hand, cytotrophoblasts incubated with anti-M-CSF antibody showed hardly any syncytiotrophoblast formation. Following this finding, we studied the differentiation of chorionic cells from the viewpoint of hormone secretion. When cytotrophoblasts were incubated in the presence of M-CSF, the supernatant of the culture showed an increase in human chorionic gonadotropin and human placental lactogen levels in proportion to the concentration of M-CSF added. When cytotrophoblasts were incubated in the presence of anti-M-CSF antibody or anti-fms antibody, human chorionic gonadotropin and human placental lactogen secretion were suppressed. Thus, M-CSF was morphologically and endocrinologically found to induce the differentiation of chorionic cells.

Decidua produces a protein that inhibits choriogonadotrophin release from human trophoblasts

To test the hypothesis that uterine decidua may modulate trophoblast function, trophoblasts and decidual cells were isolated from term placentas by enzymatic digestion and Percoll gradient centrifugation. Placental trophoblasts were cocultured with decidual cells and trophoblasts or JEG-3 choriocarcinoma cells were incubated with medium conditioned by decidual cells (DCM) for 72-96 h. In cocultures decidual cells inhibited choriogonadotropin (hCG) release from trophoblasts by 75% in comparison with controls (P less than 0.001). The DCM contained a factor that markedly inhibited hCG release from trophoblasts and JEG cells in vitro compared with controls. The inhibitory effect of the factor on hCG release was dose dependent, and could be eliminated by boiling the DCM for 30 min or proteolytic enzyme treatment. Ultrafiltration and Sephadex G-50 fractionation of the DCM indicated that the apparent molecular mass was 7,000-10,000 D. DCM also inhibited the stimulatory effect of exogenous cAMP on hCG secretion by JEG-3 cells, suggesting that DCM may interfere with activation of the cAMP-dependent protein kinases or transcription of hCG genes. These results suggest that the release of trophoblast hCG is under local paracrine control, regulated in part by a protein released by decidual cells.

Simultaneous autoradiography and line immunoelectrophoresis (ARLIE): a novel combination to identify de novo protein synthesis by pregnancy tissues

A novel combination of two conventional techniques (autoradiography, AR and line immunoelectrophoresis, LIE; ARLIE) for identification of specific proteins synthesized de novo by explants is described. The incorporation rate of [35S]-methionine was linear in proteins derived from cytosol fractions and supernatants of first trimester human trophoblast and gestational endometrium for up to 18 h. SDS-PAGE analysis of these fractions provided further evidence of the protein synthesis and secretion by the tissue explants. The ARLIE system was evaluated by investigating the synthesis and secretion of five test proteins (PP12, PP14, hPL, FA-1 and FA-2) by trophoblast and gestational endometrium. The synthesis P12 and PP14 could be demonstrated by gestational endometrium only. Similarly the synthesis of hPL could be demonstrated by the trophoblast alone. The synthesis of the fetal proteins (FA-1 and FA-2) could not be demonstrated by either tissue. The control procedure, Protein A assisted immunoprecipitation, yielded similar results for PP14 but not hPL. This novel combination (ARLIE) provides a simple technique with which to study the de novo synthesis of several proteins simultaneously which is independent of the subclass and species of origin of antibodies.

Effects of fetal sex, stage of gestation, dibutyryl cyclic adenosine monophosphate, and gonadotropin releasing hormone on secretion of human chorionic gonadotropin by placental explants in vitro

Explants from 16 term and 6 midtrimester placentas were cultured for 6 days. Statistically significant increases in secretion of human chorionic gonadotropin occurred in control medium cultures of both term and midtrimester explants during the 6-day culture period (p less than 0.01). Statistically significant increases in secretion of human chorionic gonadotropin were produced by 2 mmol/L dibutyryl cyclic adenosine monophosphate in both the term (p less than 0.01) and the midtrimester (p less than 0.01) explants. There was no effect of gonadotropin releasing hormone. The ratio of human chorionic gonadotropin secretion from midtrimester explants to that from term explants varied under different conditions, dropping from twentyfold in day 1 cultures to elevenfold for maximum secretion produced after culture in control medium for up to 6 days. A further drop in the ratio to fourfold was observed for the maximal response to 2 mmol/L dibutyryl cyclic adenosine monophosphate treatment. Explants from term female infants produced significantly more human chorionic gonadotropin than those from term male infants (p less than 0.05), but the sex difference disappeared after stimulation with 2 mmol/L dibutyryl cyclic adenosine monophosphate.

Characterization of placental lactogen release from perifused human trophoblast cells

The dynamics of the release of human placental lactogen (hPL) under basal conditions and response to various secretogogues has been studied in perifused enriched hPL-producing cells from term placentae prepared by the isopycnic centrifugation of collagenase/hyaluronidase-dispersed placental cells on Percoll gradients. Under basal conditions, the perifused cells released hPL at a relatively constant rate for up to 24 h in culture. The mean rates of hPL release from cells (5 x 10(6) cells) from 18 normal full-term placentae varied from 1.8 to 20.2 ng/5 min (mean 7.7 ng/5 min). The cells from term placentae, however, did not release detectable amounts of chorionic gonadotrophin or the cytosolic enzymes lactic dehydrogenase and alkaline phosphatase. The amounts of hPL released by the perifused cells were inversely related to cell density with mean rates of hPL release by 2, 5, and 10 x 10(6) cells of 15.8, 8.6, and 5.7 ng/10(6) cells/0.5 h. The perifused cells responded to provocative stimuli (high-density lipoproteins (HDL), apolipoproteins AI, AII, and CI, partially purified hPL-releasing factor, phorbol esters, sn-1,2-diacylglycerol, and cAMP) in a manner qualitatively similar to enriched trophoblast cells and placental explants in static culture. Release of hPL in response to HDL, apoproteins AI, AII, and CI, and partially purified hPL-releasing factor was dose-dependent and occurred within 5 min of exposure. Basal and stimulated hPL release by perifused trophoblast cells that had been previously frozen at -70 degrees C for four weeks was identical to that of freshly dispersed cells from the same placenta. These experiments indicate that perifused trophoblast cells may be used as a model system to examine the dynamics of hPL release under basal conditions and in response to provocative stimuli.

The effects of insulin-like growth factor-I and insulin on placental lactogen production by human term placental explants

The effects of insulin-like growth factor (IGF)-I and insulin on placental lactogen production (hPL) by term human placental explants were studied. The hPL content in medium and explant decreased rapidly after first 24 hours of culture. The decrease thereafter was gradual and reached a plateau by day 4 of culture. The decrease of HPL content in placental culture has previously been suggested being due to the depletion of a rapidly secreting preformed pool of hPL. Addition of IGF-I (0.1-10 micrograms/ml) and insulin (1-20 micrograms/ml) stimulated the decreased level of hPL in tissue and medium after 24 hours in culture. IGF-I was 10 times more potent than insulin in stimulating hPL. These findings suggest that IGF-I and insulin effects the production of hPL by placenta. The lower potency of insulin may indicate that the effect of insulin on hPL production is via IGF-I receptor.

Cyclic AMP inhibits the synthesis and release of prolactin from human decidual cells

Exposure of human decidual cells for 0.5 h to dibutyryl cAMP, isobutyl-methylxanthine (IBMX), cholera toxin or forskolin caused a dose-dependent inhibition of prolactin release with maximal inhibition by each agent of 50-60%. Dibutyryl cAMP (5 mM), IBMX (0.5 mM), and cholera toxin (10 micrograms/ml) also inhibited prolactin synthesis to the same extent as prolactin release. Dibutyryl cAMP, IBMX, and cholera toxin, however, had no effect on the release of 35S-methionyl-prolactin from decidual cells preincubated for 24 h in medium with 35S-methionine. These agents, however, had no effects on the synthesis or release of TCA-precipitable 35S-decidual proteins and did not cause the degradation of intracellular or released prolactin. The demonstration that agents which increase intracellular cAMP levels inhibit the synthesis and release of decidual prolactin strongly implicates cAMP as a second messenger in the regulation of the synthesis and release of the hormone. The inhibitory effect of cAMP on prolactin release appears to be on the release from a rapidly releasable, newly synthesized intracellular prolactin pool.

Apolipoproteins AI, AII, and CI stimulate placental lactogen release from human placental tissue. A novel action of high density lipoprotein apolipoproteins

High density lipoproteins (HDL) stimulated a dose-dependent increase in the release of placental lactogen (hPL) from human placental explants. The stimulation was not prevented by delipidation of HDL but was completely blocked by tryptic digestion. Delipidated apolipoproteins (Apo) AI, AII, and CI also stimulated hPL release but other apolipoproteins were without effect. HDL and Apo CI had no effects on the release of luteinizing hormone and follicle-stimulating hormone from rat pituitary cells or the release of prolactin from human decidual cells. Because placental cells have specific HDL receptors and plasma HDL concentrations increase during pregnancy, these results strongly suggest a role for HDL in the regulation of hPL release during pregnancy possibly independent of their usual role in plasma lipid transport.

Cytoskeletal markers and specific protein production in cells cultured from human first and third trimester placentae

In primary, short-term cultures derived from first and third trimester placentae, 60 to 90 and 70 to 95%, respectively, of the total cell population positively stain for cytokeratin intermediate filaments, typical of epithelial, i.e. trophoblastic cells. The rest of the cells express only vimentin intermediate filaments and thus are of mesenchymal origin. Only the cytokeratin-positive cells express human chorionic gonadotropin (hCG), whereas both the epithelial and the mesenchymal cells stain positively for pregnancy-specific beta-1-glycoprotein (SP1). Cytokeratin-negative and vimentin-positive cell overgrowth is observed in cultures derived from first and early third trimester placentae. The cells constituting the monolayer thus formed are of fetal origin as evidenced by the expression of Y-body in over 80% of them. The cultured cells synthesize and secrete hCG and SP1. The activity of these trophoblast-specific functions is inversely proportional to the gestational age of the placenta. Production of specific proteins and expression of intermediate filaments are proposed as criteria for defining the nature and origin of placental cells in primary, short-term cultures.

In vitro secretory patterns of human chorionic gonadotrophin, placental lactogen and pregnancy-specific beta 1-glycoprotein

The control of secretion of the placental hormones human chorionic gonadotrophin (hCG) and human placental lactogen (hPL), and the trophoblastic protein pregnancy-specific beta-glycoprotein (SP1), is not well understood. During pregnancy, the hCG concentrations peak in the first trimester then decrease, while hPL and SP1 increase steadily throughout gestation. In order to determine whether the discordance between hCG secretion and that of hPL and SP1 observed in vivo also occur in vitro, we cultured placental explants with and without dibutyryl cyclic AMP (dbcAMP) and theophylline. Between 5 and 12 explants were used for each treatment in each experiment. The concentration of the proteins secreted into the media each day was measured by specific radioimmunoassays. The quantities of hPL and SP1 secreted per day declined in a parallel fashion after 24 hours under both basal and dbcAMP-stimulated conditions. The hCG output progressively decreased in the unstimulated cultures until 48 hours, at which time an increase in hCG secretion was observed. The dbcAMP-stimulated placentae significantly increased their hCG output at both 48 and 72 hours. These data show that hCG secretion is regulated differently from that of hPL and SP1. The results do not negate the possibility that term placental tissue may contain an inhibitor of hCG release that is removed by experimental manipulation in vitro.

Effect of estradiol and progesterone on human chorionic gonadotropin secretion in vitro

Many of the substances known to control the secretion of pituitary gonadotropins also modulate the secretion of human chorionic gonadotropin (hCG) by the placenta. In order to study the effect of estrogens and progestins on hCG secretion, term placental explants were cultured in culture media for 144 hours. During the culture period, hCG secretion increased after 48 hours, and a fortyfold increase was observed after 144 hours (p less than 0.001). Compared to concentrations of hCG in control cultures, secretion of hCG was markedly suppressed in the presence of progesterone 2.25 X 10(-5)M (p less than 0.001), a concentration similar to that found in term placental tissue (1.7 +/- 0.2 micrograms/gm of tissue). Suppression of hCG by progesterone occurred in a dose-response manner (r = -0.9100, p less than 0.01). Estradiol, an important steroid modulator of pituitary gonadotropins, did not significantly suppress the secretion of hCG, except in pharmacologic concentrations (10(-4)M), and physiologic concentrations of estradiol had no effect on the suppression of hCG by progesterone. These results suggest that the mechanism by which progesterone suppresses the secretion of hCG differs from the manner in which steroids modulate the secretion of pituitary gonadotropins.

Stimulation of human chorionic gonadotropin secretion by glucocorticoids

The effects of glucocorticoids on hormone secretion by human placenta in organ culture were studied. The addition of cortisol resulted in a fourfold increase in human chorionic gonadotropin (hCG) secretion over that in untreated cultures after 144 hours' incubation (P less than 0.05), and a twofold increase in hCG was observed in the presence of cortisone (P less than 0.01). Dexamethasone stimulated hCG secretion in a dose-response manner (r = 0.9542; P less than 0.01). Progesterone, which suppresses hCG under these conditions, decreased the cortisol-enhanced secretion of hCG (r = -0.9794; P less than 0.01). No change in the secretion of human chorionic somatomammotropin was observed, but glucocorticoids increased heat-stable alkaline phosphatase activity (P less than 0.001). The physiologic significance of glucocorticoid effects on placental hormone synthesis is discussed.

Human placental lactogen release in vitro: paradoxical effects of calcium

To study the effects of calcium on the release of human placental lactogen (hPL), placental explants were exposed to media containing lower or higher concentrations of calcium than normally available to the placenta. Explants exposed for 2 h to calcium-poor medium or medium containing either 2 mM EDTA or 2 mM EGTA released 160, 248, and 253% more hPL, respectively, than control explants. In contrast, explants exposed to medium containing higher than normal calcium concentrations released the same amounts of hPL as the control explants. At lower than normal extracellular calcium concentrations, the increased hPL release was inversely proportional to the calcium concentration. The increased release in calcium-poor medium was inhibited by subsequent exposure of the explants to medium containing calcium and was prevented by either barium or magnesium. Changes in barium or magnesium concentrations, however, had no effects on hPL release in the presence of normal extracellular calcium concentrations. Methoxyverapamil (D 600), an inhibitor of calcium flux, stimulated hPL release. Because low extracellular calcium and methoxyverapamil both inhibit calcium influx, these experiments suggest that calcium influx inhibits hPL release. The role of calcium in the regulation of hPL release therefore appears to be different from that reported in other release systems.

Interrelationships of human chorionic gonadotropin, human placental lactogen, and pregnancy-specific beta 1-glycoprotein throughout normal human gestation

Human chorionic gonadotropin (hCG), human placental lactogen (hPL), and pregnancy-specific beta 1-glycoprotein (PSBG) were measured by radioimmunoassay in 270 samples of serum from women with uncomplicated pregnancies. All three proteins were significantly correlated with each other in individual samples of serum and with the estimated trophoblastic mass during the first trimester. No significant correlation could be demonstrated between the concentrations of hCG and PSBG in maternal serum during the second or third trimesters or between the concentrations of hCG and hPL during the second trimester. Levels of PSBG and hPL in serum were significantly correlated throughout all three trimesters. These findings suggest that the secretion of hCG, hPL, and PSBG may be regulated by similar control mechanisms during the first trimester of pregnancy. However, after this period, the factors that modulate the production of hCG differ from those that regulate the production of hPL and PSBG.

Suppression of human chorionic gonadotropin by progestational steroids

The dynamics of the secretion of human chorionic gonadotropin (hCG) were studied by culturing explants of normal term placentas for as long as 144 hours. A significant accumulation of immunoreactive hCG (beta-subunit) was first detected at 48 to 72 hours, and a sixfold increase in hCG was observed in control culture medium at 144 hours. Compared to control cultures, progesterone (P < 0.001) in physiologic tissue levels of 5 to 20 micrograms/ml, pregnenolone (P < 0.001), 20 micrograms/ml, and 20 alpha-dihydroprogesterone (P < 0.001), 20 micrograms/ml, suppressed the secretion of hCG throughout the study period. Progesterone decreased the secretion of hCG in a dose-response manner (r = -0.8S87, P < 0.1). No suppression of hCG was observed in the presence of cortisol, testosterone, dihydrotestosterone, 17 beta-estradiol, or estriol. The secretion of human chorionic somatomammotropin was unchanged in the presence of progesterone. The augmented hCG response in the presence of dibutyl cAMP (P < 0.001) was significantly, but not completely, suppressed by progesterone 20 micrograms/ml culture medium (P < 0.01). Under these conditions progestational steroids or their immediate metabolites suppress the secretion of hCG, and they may be responsible for the decline in the levels of hCG during pregnancy.

A possible role for prolactin in the control of human chorionic gonadotropin and estrogen secretion by the fetoplacental unit

The effects of prolactin (PRL) on fetoplacental function were studied by measuring the beta subunit of human chorionic gonadotropin (hCG-beta), estradiol (E2), progesterone (P), and PRL concentrations throughout seven pregnancies in a control group (N = 6 women) and in three pregnant women with prolactinomas, who were receiving bromocriptine. In one of the latter, estriol (E3) was also assayed. Long-term suppression of PRL was associated with augmentation of hCG-beta at the first-treimester peak and in late pregnancy. Concomitant augmentation of E3 (in late gestation) and possibly E2, but not P, levels was also observed. This effect on hCG appeared dependent on PRL rather than the dopaminergic effect of bromocriptine. Short-term drug induced alterations in PRL (over 3 hours) during early pregnancy did not result in significant changes in hCG-beta or steroid concentrations. In each control pregnancy, a significant negative correlation (p less than 0.05) was observed between hCG-beta and PRL, while a significant positive correlation between the latter and E2 concentrations in these women was also demonstrated. Apart from its effect on lactation, osmoregulation, and gonadal and adrenal function, a further role for PRL during reproduction appears to be in the control of hCG and estrogen secretion in the fetoplacental unit.

Prolactin synthesis by human chorion-decidual tissue: a possible source of prolactin in the amniotic fluid

Explants of human chorion-decidual tissue obtained at delivery from normal, full-term pregnancies synthesize and secrete prolactin. This hormone is indistinguishable from pituitary prolactin by chromatographic, electrophoretic, immunologic, and receptor assay techniques. These results suggest that chorion-decidua may be the source of the large quantities of prolactin in amniotic fluid.