Suppression of human chorionic gonadotropin by progestational steroids

Quantitative evaluation of the influence of ovarian steroids on plasminogen activators and inhibitors in human endometrial cells and trophoblasts

INTRODUCTION

Plasminogen activators and inhibitors were quantitated in cultured human endometrial and trophoblast cells under the influence of ovarian steroids in order to investigate the role of the fibrinolytic system for trophoblast invasion and anchorage.

MATERIALS AND METHODS

Plasminogen activators (t-PA and u-PA) and their inhibitors (PAI-1 and PAI-2) secretions were assayed in cultures of epithelial, stromal, and trophoblast cells. These cells were also cultured on a fibrin substrate for microscopic examination of the fibrinolytic degradation.

RESULTS

The u-PA from epithelial cells was predominant among PAs and PAI-1 in endometrial cells. Estradiol (E2) enhanced t-PA production in stromal cells and PAI-1 production in epithelial cells. Progesterone (P4) suppressed u-PA production in epithelial cells and enhanced PAI-1 production in both epithelial and stromal cells. Trophoblasts produced PAI-1, PAI-2, and small quantities of t-PA and u-PA, none of which were notably influenced by E2 or P4. The PAI-1 production in trophoblasts was more than four-fold greater than the u-PA production in epithelial cells. Epithelial and stromal cells initially grew on fibrin substrate but were gradually detached from the substrate with fibrinolytic degradation, with the exception of the stromal cells grown in the presence of P4 (or E2+P4). Trophoblasts grew well on fibrin substrate without fibrinolytic degradation both in the presence and absence of the steroids tested.

CONCLUSIONS

Fibrinolytic balance seemed to be basically maintained between the endometrial PAs and the relative excess of trophoblasts-derived PAI-1. This balance might be regulated principally by P4 and focally by E2 in the endometrial tissue for placental implantation.

Progesterone inhibits transcriptional activation of human chorionic gonadotropin-alpha gene through protein kinase A pathway in trophoblast cells

The purpose of this study was to analyze the mechanism of transcriptional inhibition of human chorionic gonadotropin-alpha (hCGalpha) gene by progesterone in trophoblast cells. We stably transfected -290 bp hCGalpha promoter-CAT constructs (-290halphaCAT) into Rcho-1 cells and monitored the promoter activities. Differentiation-dependent activation of -290 bp hCGalpha promoter containing a tandem repeat of cAMP response element (CRE) was inhibited by progesterone in a dose-dependent manner. To further analyze the mechanism of the progesterone action, Rcho-1 cells stably transfected with -290halphaCAT were treated with forskolin in the presence of progesterone. Progesterone inhibited forskolin-induced transcriptional activation of hCGalpha gene. Moreover, progesterone inhibited forskolin-induced transcriptional activation of CRE-CRE-tk-CAT. These results suggest that progesterone may inhibit cAMP-induced transcriptional activation of hCGalpha gene through CRE. Although progesterone did not alter the amount of CRE-binding protein (CREB), which is a main transcriptional factor bound to CRE(s) on hCGalpha promoter, progesterone abolished forskolin-induced CREB phosphorylation. In addition, pretreatment with progesterone abolished forskolin-induced activation of nuclear protein kinase A (PKA). In conclusion, progesterone inhibits hCGalpha gene transcription, at least in part, via the CRE region by inhibiting CREB phosphorylation through PKA pathway in trophoblast 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.

Effect of gonadal steroids on gonadotropin-releasing hormones stimulated human chorionic gonadotropin release by trophoblast cells

The effect of gonadal steroids on basal and GnRH-stimulated hCG release was studied using collagenase-dispersed trophoblast cells from early pregnancy. Both GnRH and a GnRH superagonist, Buserelin, stimulated hCG release with a similar dose dependency. Progesterone (0.1 to 10 micrograms/ml) inhibited GnRH-stimulated hCG release in a dose dependent manner as well as basal hCG release. Relatively high concentrations of estradiol (10 micrograms/ml) stimulated both basal and GnRH-mediated hCG release and antagonized the inhibitory effect of progesterone on hCG release at 1 micrograms/ml as well as RU486 (1 microgram/ml). These results indicate that progesterone has an important role in both basal and GnRH-mediated hCG regulatory system in the placenta.

The effects of various hormones on human chorionic gonadotropin production in early and late placental explant cultures

Although human chorionic gonadotropin production peaks in early pregnancy, little is known of the factors regulating it at this time. We have compared human chorionic gonadotropin output in placental explants of 6 to 12 and 37 to 40 weeks' gestational age after addition of hormones on days 4 and 5 of 8 days of culture. Human chorionic gonadotropin production was sevenfold greater in early versus late cultures. In early cultures human chorionic gonadotropin output was increased threefold to fourfold by progesterone, dehydroepiandrosterone, and cortisol whereas late cultures responded only to progesterone and dehydroepiandrosterone. The output of combinations of steroids was additive or better (up to fifteenfold). Gonadotropin-releasing hormone increased human chorionic gonadotropin output only slightly (onefold to twofold) while testosterone was inhibitory (early) or ineffective (late). Estradiol had no effect. These studies demonstrate that explants of early placental tissue provide a useful model for study of human chorionic gonadotropin production, that there are many similarities but some clear differences between early and late secretion, and that steroids exert significant effects on human chorionic gonadotropin production of placental cultures.

Termination of early pregnancy by the 3 beta-hydroxysteroid dehydrogenase inhibitor epostane

Progesterone is essential to sustain pregnancy in the first eight weeks. Its synthesis requires the enzyme 3 beta-hydroxysteroid dehydrogenase (3-HSD). We tested the efficacy of an orally administered 3-HSD inhibitor, epostane, in terminating unwanted early pregnancy. Fifty women in the fifth through eight weeks of pregnancy took epostane (200 mg orally every six hours) for seven days. By day 14, pregnancy had been terminated in 42 of the 50 patients (84 percent). Eight women (16 percent) did not abort and underwent dilation and curettage. Vaginal blood loss occurred on average on the third day of epostane treatment, and abortion on the fifth day. Two patients had incomplete abortions; one required a transfusion because of blood loss. Nausea was frequent (in 86 percent), but 76 percent of the participants concluded that epostane was preferable to dilation and curettage. The mean (+/- SD) pretreatment progesterone level (76 +/- 16 nmol per liter) decreased by day 7 (to 16 +/- 11 nmol per liter) and day 14 (to 10 +/- 9 nmol per liter) in those who aborted; levels of human chorionic gonadotropin also decreased from the mean at base line (73 +/- 72 kIU per liter) to 18 +/- 7 kIU per liter on day 7 and 9 +/- 5 kIU per liter on day 14. In those who did not abort after epostane treatment, progesterone levels decreased only slightly by day 7 (to 52 +/- 21 nmol per liter) and rose again (to 81 +/- 18 nmol per liter) by day 14. Among women who responded to epostane, normal menstrual periods had resumed by day 42 after the beginning of treatment in 72 percent. We conclude that epostane taken orally is an effective and safe method for the noninvasive termination of undesired early pregnancy.

Estrogen synthetase (aromatase) in cultured human term placental cells and neoplastic human trophoblast

Estrogen synthetase (aromatase) is present in large amounts in human term placenta. However, the localization of aromatase within the cellular structure of the placental villus is obscure. By immunocytochemical techniques using antibodies that separately recognize each component of the aromatase cytochrome P-450 enzyme system, the fraction of term placental trophoblast cells in primary culture expressing each aromatase component antigen increased from 20% in fresh mononucleated cells to about 65% for multinucleated giant cells after 72 h. In contrast, about 80% of human choriocarcinoma cells in continuous culture (JAr line) expressed each aromatase component antigen. The fraction of trophoblast cells in primary culture containing human chorionic gonadotropin increased from about 14% in fresh mononucleated cells to about 45% after 72 h and was about 30% in the choriocarcinoma cells. Fibroblast cells in culture, derived from trypsin-treated placental villi, contained aromatase activity, albeit much lower than term placental trophoblast cells. Aromatase specific activity in these placental fibroblasts did not change following growth with dibutyryl cAMP plus theophylline for 72 h.

Human chorionic gonadotropin, prolactin, estriol, and dehydroepiandrosterone sulfate concentrations in cord blood of premature and term newborn infants: relationship to the sex of the neonate

Although the composition of human chorionic gonadotropin, prolactin, estriol, and dehydroepiandrosterone sulfate in the umbilical cord blood has been studied, less information is available on the effect of fetal sex on the cord blood concentrations. We assayed these hormones in cord blood from 405 newborn infants delivered between 23 and 43 weeks of gestation. In pooled data for both sexes, human chorionic gonadotropin showed a declining trend from the beginning to the end of the sampling interval. By contrast, in 398 newborn infants of known sex, prolactin, estriol, and dehydroepiandrosterone sulfate levels increased during the same period. Sex differences were observed for human chorionic gonadotropin only; female newborn infants had higher cord blood concentrations throughout the sampling period, with the differences becoming statistically significant between 29 and 36 weeks.

Medroxyprogesterone acetate in non-metastatic gestational trophoblastic disease

The effect of medroxyprogesterone acetate (MPA: Depo-Provera, Upjohn) as a contraceptive agent was assessed in 45 patients with non-metastatic gestational trophoblastic disease and compared with 13 patients using hormonal and 26 patients using non-hormonal methods of contraception. In the whole group of 84 patients 18 (21.4%) required chemotherapy. There was no statistically significant difference in the incidence of persistent trophoblastic disease between MPA (9/45) and the oral contraceptive group (2/13) and MPA and the non-hormonal contraceptive groups (7/26).

Inhibition of human chorionic gonadotropin production by prolactin from term human trophoblast

In vivo suppression of prolactin concentrations by bromocriptine near term, in a pregnant woman with a prolactinoma, was followed by augmentation of human chorionic gonadotropin levels. Suspension of drug therapy at 38 weeks of gestation was followed by a reversal of this sequence of events. In vitro, both ovine prolactin and human prolactin added to explants of term placental trophoblast significantly inhibited human chorionic gonadotropin production from this tissue. Although, with ovine prolactin, this inhibitory effect was demonstrable up to 5 micrograms/ml of ovine prolactin in the culture medium, only doses of 0.1 to 0.2 micrograms/ml of human prolactin significantly suppressed human chorionic gonadotropin production. Overall, 0.1 and 0.2 micrograms/ml of ovine prolactin and human prolactin most consistently suppressed human chorionic gonadotropin production to a statistically significant extent. In general, the concentrations in the culture medium of both ovine prolactin and human prolactin that inhibited human chorionic gonadotropin production in vitro were comparable to the concentrations of prolactin present in the mother and fetus. These in vivo and in vitro observations suggest that prolactin inhibits human chorionic gonadotropin production from term human trophoblast.

Critical factors in establishing monolayer cultures of normal human placental cells in serum-free medium

Comparative studies have been performed to determine the best method for preparing monolayer cultures of normal human term trophoblast cells. The use of 0.25% trypsin-10 U/ml DNAse I provided the highest cell viability and greatest hormone production, but was critically dependent on the trypsin lot used. Cell function in culture was not improved with various substrata, nor did other factors (medium type, pH, red blood cell removal) affect the results. Optimization of dispersal and culture conditions permitted the trophoblast cells to survive with intact hormone secretion and response to secretagogues under serum-free conditions. These studies thus define the best methodology for establishing trophoblast cells in monolayer 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.

Preservation of human chorionic gonadotropin and placental lactogen secretion and normal morphology following long-term culture of normal human placental cells

In order to study the regulation of hCG and hPL secretion during gestation, a system for the preservation of the functional integrity of normal placental cells in long-term culture was established. Normal term placental cells were dispersed with 0.25% trypsin-500 units DNAse I and cultured in a monolayer in Dulbecco's modified Eagle medium with 10% fetal bovine serum. Normal cell morphology, basal hCG and hPL production and hCG responses to dibutyryl cAMP were preserved till 54 days of culture. This model may be useful for the study of long-term regulation of normal placental hCG and hPL synthesis and secretion.

Daily rhythm of serum human chorionic gonadotropin and human chorionic somatomammotropin in normal pregnancy

We have quantified the human chorionic gonadotropin (HCG) and human chorionic somatomammotropin (HCS) serum levels in normal pregnant women at 1-h intervals during 24 h, through radioimmunoassay procedures. The HCG levels were higher during the first trimester, although no circadian variations were detected. Some variations exceeded by ten fold; these variations decreased with advanced periods of gestation. No diurnal fluctuations in serum HCS were apparent; in a case nearly at term, there was an increase from 05:00 h to 09:00 h simulating a circadian pattern, although it was not statistically significant. These data indicate that the placental protein secretion is autonomous and that HCG levels of fluctuation during early stages of pregnancy might be regulated by factors other than the trophoblast.

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.

Accuracy of serum human chorionic gonadotropin concentrations and ultrasonic fetal measurements in determining gestational age

Prior to 60 days' gestation, the maternal serum concentration of human chorionic gonadotropin (hCG) can predict the estimated date of confinement, but later in pregnancy, hCG concentrations vary widely. The current study was performed to compare the accuracy of hCG measurements with other determinants of gestational age. Fifteen patients in whom gestational age was documented were monitored prospectively throughout pregnancy. One to two determinations of hCG (beta subunit) were obtained during the first 60 days. Then, ultrasonographic measurements of crown-rump length were obtained between 8 and 16 weeks' gestation and two measurements of biparietal diameter were performed between 18 and 32 weeks. These results were compared to actual dates of gestation. The mean (+/- SD) difference between gestational age predicted by single measurements of hCG and actual gestational age was 3.2 +/- 2.5 days (r = 0.94, p less than 0.0001), which compared favorably with estimates by crown-rump measurements (6.7 +/- 6.5 days) and measurements of biparietal diameter (6.3 +/- 5.3 days). These results demonstrate that hCG measurements during the first 60 days accurately predict gestational age and complement ultrasonic determinations of gestational age used later in pregnancy.

Pregnancy hormone concentrations in marijuana users

The maternal serum concentrations of human chorionic gonadotropin, pregnancy-specific beta-l-glycoprotein, placental lactogen, progesterone, 17-hydroxyprogesterone, estradiol and estriol were measured in 13 women who smoked marijuana regularly throughout pregnancy. Cannabinoid use in these women was confirmed by RIA measurements of their serum delta 9-tetrahydrocannabinol (THC) concentrations. These THC using women were matched within 2 1/2 weeks of gestational age with 13 pregnant non-THC using controls drawn from the same population. Placental protein and steroid hormone concentrations were within established normal ranges for gestational age and there were no significant differences between the groups in the concentrations of any of the protein and steroids measured. In addition, no significant differences between THC users were found following linear regression analysis of placental hormone concentrations as a function of gestational age. Thus, this study suggests that marijuana use during pregnancy does not significantly alter the circulating maternal concentrations of trophoblastic protein hormones or major fetoplacental steroid hormones.

Effect of estradiol-17 beta on the conversion of pregnenolone to progesterone in human term placenta incubated in vitro

The effect of different doses of estradiol-17 beta (E2) on the metabolic pregnenolone to progesterone pathway in fragments of human term placenta incubated in vitro was studied. Doses considered as being physiological of 0.09 and 0.9 microM had a stimulatory effect on the conversion (p less than 0.008 to 0.016). However, a supraphysiological dose of 45 microM showed an inhibitory activity related to the maximal stimulation (p less than 0.03). A dose of 0.9 microM E2 favoured the accumulation of (3H)-progesterone in the tissue (p less than 0.05). These results suggest that E2 may regulate the synthesis of progesterone in human term placenta.

The regulation in vitro of placental release of human chorionic gonadotropin, placental lactogen, and prolactin: effects of an adrenergic beta-receptor agonist and antagonist

An experimental model for the study of placental tissue release of hormones has been explored. It has been shown that the trophoblast in Ringer-glucose solution releases human placental lactogen (hPL) and chorionic gonadotropin (hCG) in a time- (10 to 180 minutes) and temperature- (4 degrees and 37 degrees C) dependent manner. The adrenergic beta-receptor agonist terbutaline caused an increase in hCG secretion but did not affect hPL. With a mixed trophoblast/decidua preparation, prolactin release was not found to be time and temperature related. Terbutaline increased prolactin release and timolol decreased it. The data suggest tha adrenergic mechanisms are involved in hCG and prolactin secretion from the placenta.

Plasminogen activator production by trophoblast cells in vitro: effect of steroid hormones and protein synthesis inhibitors

Variations in the production of plasminogen activator (PA), a proteolytic enzyme that has been associated with trophoblast invasiveness, may be critical to the success or failure of placentation. To understand better the mechanisms regulating PA production we have cultured human trophoblast cells and measured the effect of steroid hormones and protein synthesis inhibitors upon their capacity to lyse 125I-fibrinogen. Progesterone (P) and 17 beta-estradiol (E2) at concentrations of 10(-8)M, 10(-7)M, and 10(-5)M did not cause significant changes in PA or chorionic gonadotropin (hCG) production by the trophoblast cells. In contrast, dexamethasone (10(-8)M and 10(-5)M) caused a significant, dose-dependent decrease in PA production. There was no significant difference in PA and hCG production between trophoblast cultures treated with cytosine arabinoside (1 mg/ml) and untreated cultures. When actinomycin D (0.5 microgram/ml) was added to cultures at time zero, the production of PA and hCG during the first 24 hours of incubation was not significantly different from that of untreated cultures. After 24 hours, however, PA and hCG disappeared from the actinomycin-treated cultures while both substances continued to be released in the untreated controls. These experiments indicate that trophoblastic PA and hCG production in vitro are independent of DNA replication and not under P or E2 control. They also show that PA and hCG are stored within the trophoblast cells and released into the medium during the first 24 hours of incubation; after this period the presence of PA and hCG in the medium represents de novo synthesis. The data also suggest that, similar to hCG, PA is produced continuously in vitro as long as the trophoblast cell is functionally active.

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.