Modulation of prostacyclin and thromboxane secretion by cytotrophoblasts from normal and pre-eclamptic human pregnancies

We and others have previously observed an imbalance in cytotrophoblast secretion of the vasoactive prostanoids prostacyclin and thromboxane A(2) in pre-eclampsia. To examine the effects of potential modulators of this imbalance, cytotrophoblasts isolated from normal and pre-eclamptic pregnancies were incubated in the presence of lipopolysaccharide, the calcium ionophore A23187, tumour necrosis factor alpha, or interleukin 1beta, with or without the cyclo-oxygenase inhibitor, indomethacin. Further incubations included the drugs tranylcypromine, a prostacyclin synthetase inhibitor (0.1, 10 microM ), or the thromboxane synthetase inhibitor, pirmagrel (0.001, 1 microM ). Results showed that cytotrophoblasts from pre-eclamptic pregnancies had increased thromboxane production and significant stimulation of prostacyclin production by lipopolysaccharide and calcium ionophore. Lipopolysaccharide stimulated thromboxane production in normal cytotrophoblasts, while indomethacin almost completely inhibited production of both prostanoids. Tranylcypromine mildly inhibited prostacyclin production in normal cytotrophoblasts only, whereas pirmagrel strongly inhibited thromboxane production in a dose-related manner, with reciprocal increase in prostacyclin production occurring in cytotrophoblasts from pre-eclamptic pregnancies. This study confirmed that cytotrophoblasts from pre-eclamptic women had increased thromboxane production and showed that pirmagrel, at the relatively low dose of 0.001 microM, was able to normalize the imbalance of thromboxane and prostacylin production and may therefore warrant further investigation as a treatment for pre-eclampsia.

A novel in vitro co-culture system for the study of maternal decidual endothelial cell-trophoblast interactions in human pregnancy

Investigation of the pathophysiology of pre-eclampsia (characterised by insufficient invasion of the intrauterine vasculature by cytotrophoblasts) has been hampered by the absence of a suitable animal model, and ethical constraints in clinical studies. We have developed a novel in vitro human cell co-culture system allowing direct assessment of cytotrophoblast invasion of a decidual endothelial cell monolayer from the abluminal side, as occurs in vivo. This model will facilitate detection, at the cellular level, of abnormal endothelial cell-trophoblast functional interactions in pre-eclampsia and other pregnancy disorders with abnormal placentation.

Regulation of insulin-like growth factor-binding protein-3 ternary complex formation in pregnancy

The IGFs are believed to be important in pregnancy and are implicated in the pathophysiology of pre-eclampsia. In adults the IGFs circulate primarily with IGF-binding protein-3 (IGFBP-3) and an acid-labile glycoprotein (ALS) in a 140 kDa complex which limits IGF bioavailability. Less than 10% of IGFBP-3 is in lower molecular weight forms. We have investigated the developmental regulation of the IGF/IGFBP system in normal and pre-eclamptic pregnancies with particular emphasis on the IGFBP-3 ternary complex. Circulating levels of IGF-I, IGFBP-3 and ALS, and their degree of association in the ternary complex in the fetus increased with gestational age. In neonatal serum from deliveries <35 weeks' gestation IGFBP-3 was predominantly in 30-50 kDa form(s) and ALS was a limiting factor for ternary complex formation. In serum from deliveries >35 weeks both ALS and IGFs were limiting but approximately 25% of IGFBP-3 was unable to form the ternary complex even in the presence of excess ALS and IGF-I. Serum IGFBP-1, -2 and -6 concentrations tended to decrease with increasing gestational age. In pre-eclamptic pregnancies, amniotic fluid IGFBP-2, -3 and -6 levels decreased with gestational age while IGFBP-1 levels did not show the normal decline. We speculate that the endocrine IGF system develops in the fetus during the third trimester of pregnancy when ALS levels increase.

Prenatal screening in the first trimester of pregnancy

Prenatal screening for fetal abnormalities in an accepted part of modern obstetric management. Improvements on current screening procedures need to address increased diagnostic efficacy and earlier diagnosis. This study evaluates diagnostic efficacy of PAPP-A and F beta-hCG in the detection of first trimester pregnancy abnormalities, including Down syndrome (DS). Of 731 pregnant volunteers, obtained from a mature age population undergoing chorionic villus sampling (CVS), 17 DS and 11 compromised (six numerical (excluding sex chromosome) aneuploidies, five spontaneously failed) pregnancies were detected. Application of an algorithm, which combines PAPP-A and F beta-hCG levels with material age, detected 66.6 per cent of DS pregnancies for a five per cent false positive rate. Similarly, for a 1-2 per cent recall rate, 72.2 per cent of compromised pregnancies were detected. This report supports the notion that prenatal screening at 9-12 weeks of pregnancy is achievable with PAPP-A and F beta hCG quantitation. Whereas mid-gestational screening targetted the detection of fetal abnormalities, screening earlier in pregnancy will detect other pregnancy-related abnormalities, in addition to aneuploidy.

Serum from women with preeclampsia partially corrects the abnormal in vitro prostacyclin secretion of preeclamptic villous cytotrophoblasts but not that of prostaglandin E2 or endothelin-1

OBJECTIVE

This study was conducted (1) to determine in vitro placental villous cytotrophoblast secretion of prostacyclin, prostaglandin E2, and endothelin-1, (2) to examine the effect of serum from normal and preeclamptic women on secretion of these vasoactive substances, and (3) to determine whether responses to these sera by cytotrophoblasts from preeclamptic pregnancies are different from those of normal pregnancies.

STUDY DESIGN

Cytotrophoblasts isolated from human placentas collected at cesarean section from normal and preeclamptic women were incubated for 20 hours in 20% (vol/vol) sera from preeclamptic or gestational age-matched normal pregnant women. Levels of prostacyclin (measured as 6-keto-prostaglandin F1alpha), prostaglandin E2, and endothelin-1 were measured in cytotrophoblast supernatants.

RESULTS

In normal pregnancy sera preeclamptic cytotrophoblasts secreted significantly lower amounts of prostacyclin and prostaglandin E2 but higher amounts of endothelin-1 than did normal cytotrophoblasts. In preeclamptic sera the abnormality of prostacyclin secretion by preeclamptic cytotrophoblasts was partially corrected, but there was no effect on prostaglandin E2 or endothelin-1 secretion. Preeclamptic sera had no effect on secretion by normal cytotrophoblasts.

CONCLUSIONS

The differences between normal and preeclamptic cytotrophoblasts in prostacyclin, PGE2, and endothelin-1 secretion and in response to preeclamptic serum suggest altered arachidonic acid metabolism in preeclampsia.

In-vitro secretion of prostanoids by placental villous cytotrophoblasts in pre-eclampsia

Villous trophoblasts isolated from term placentae of normal pregnancies, and pregnancies complicated by chronic hypertension or pre-eclampsia, were examined over 7 days in primary culture. Low levels of prostaglandin E2 and prostacyclin (measured as 6-keto prostaglandin Fl alpha) were secreted by trophoblast cells from all three clinical groups. Secretion was maximal at day 1 and decreased exponentially thereafter. Thromboxane secretion also fell sequentially from day 1. Thromboxane secretion by pre-eclamptic trophoblasts was three to four times that of cells from normal or chronically hypertensive subjects. Prostanoid secretion by isolated cultured cytotrophoblasts was not dependent on aggregation or morphological alteration, nor related to changes in progesterone or human chorionic gonadotrophin production. Because the local maternal circulation is exposed to substances secreted by this cell population, thromboxane could be the trigger for vasoconstriction and coagulation found within the maternal uteroplacental circulation in pre-eclampsia.

Trophoblast antigen levels in the first trimester of a trisomy 22 pregnancy

We report trophoblast antigen (pregnancy-associated plasma protein-A, PAPP-A; free beta-human chorionic gonadotrophin, F beta hCG) expression in a trimosy 22 pregnancy. Maternal concentrations of these antigens were depressed prior to detection of abnormalities by ultrasonography. Immunohistochemical findings were consistent with depressed marker expression.

Triple test for prenatal detection of Edwards syndrome (trisomy 18)

OBJECTIVE(S)

To demonstrate the limitation of complete reliance on computer generated interpretations and to highlight the need for understanding of pregnancy-related biochemistry when offering prenatal screening.

METHODS

Four cases of cytogenetically confirmed trisomy 18 pregnancies are presented. All four cases underwent prenatal screening (Triple Test-AFP, uE3, t beta-hCG) at midgestation and risk assessment by the alpha algorithm.

RESULTS

All four cases of trisomy 18 were assessed as being at low risk for DS and/or open NTD. Although marker levels were not consistent with either of these clinical situations, they were indicative of a compromised pregnancy. Circulating levels of trophoblast-derived antigens (uE3, t beta-hCG) were depressed (< or = 0.5 MoM) in all four cases. Further investigations (ultrasonography, amniocentesis) confirmed a trisomy 18 fetus.

CONCLUSIONS

Risk assessment by computer based algorithms relies on maternal factors and specific DS/NTD marker profiles. Aberrant marker profiles are not distinguished from normal. Therefore, it is essential that prenatal screening is offered only by those competent in pregnancy biochemistry and able to identify these abnormal situations.

Isolation of ERp72 from guinea pig term placentae using heparin Sepharose affinity chromatography

The mammalian placenta synthesises many varied antigens, including proteins, such as hormones, enzymes and protease inhibitors. In this report, we isolated and purified the two protein isomerase-related protein precursor ERp72 isoforms from aqueous extracts of guinea pig placenta, by four (4) chromatographic procedures; i) affinity chromatography on immobilised heparin, ii) gel filtration (Ultrogel AcA-54), iii) anion exchange chromatography (Mono-Q), and, iv) negative immunoaffinity chromatography. From 20 term placentae, the final yield of ERp72 isoforms was 2.4mg (Mr 71.5 kDa) and 1.5mg (Mr 75.8 kDa). Identity was confirmed by NH2-terminal amino acid sequencing which demonstrated 85% homology to human ERp72. By indirect immunofluorecence. ER p72 expression was demonstrated in tunicamycin stressed pre-implantation embryos and unfertilised oocytes. These findings demonstrate the potential for immunological monitoring of ERp72 expression, by cultured oocytes and embryos, during manipulation by assisted reproductive technologies.

Influence of fetectomy on serum pregnancy-associated plasma protein-A concentrations in the baboon

In baboons as in humans, the placenta is a source of various peptides, including pregnancy-associated plasma protein-A (PAPP-A). However, our present understanding of the regulation of PAPP-A production is incomplete. We have demonstrated that after fetectomy, the baboon placenta retains steroidogenic capacity and is maintained in utero until delivered spontaneously close to term. We have suggested, therefore, that fetectomy provides a valuable in vivo approach to elucidating the role(s) of the fetus, and of the hormones (e.g., estrogen and progesterone) dependent upon the presence of the fetus, in the regulation of placental steroidogenesis during primate pregnancy. Therefore in the present study we utilized the fetectomy model to evaluate the respective roles of the fetus, estrogen, and progesterone on placental PAPP-A. Estradiol, progesterone, and PAPP-A concentrations were determined by RIA in maternal blood collected under ketamine anesthesia on Days 78-100 (n = 5), Days 102-144 (n = 4), and Days 146-164 (n = 3) of gestation (term = Day 184) in control baboons (Papio anubis) and on Days 110-164 in baboons fetectomized on Day 100 (n = 9). Studies were also conducted in five animals in which placental estrogen was increased by maternal treatment on Days 70-100 with androstenedione and in three animals treated on Days 140-164 with the antiestrogen, ethamoxytriphetol (MER-25; 25 mg/day/kg BW).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis and management of extrauterine pregnancies

This study was based on 16 women provisionally diagnosed as having extrauterine pregnancies. Of these, 13 (81.3%) were confirmed as positive at operation. Patients were managed according to 1 of 3 regimens; 1) methotrexate (n = 4), 2) methotrexate followed by surgery (n = 3) and 3) surgery (n = 6). Serial blood samples, collected before and after treatment, were analyzed for ovarian (oestradiol, E2; progesterone, P4) uterine (placental protein 14, PP14) and placental markers (chorionic gonadotrophin, HCG; pregnancy-associated plasma protein-A (PAPP-A). Of the pretreatment samples, only 30.4% and 41.7% were depressed for PP14 and HCG, respectively. By contrast, the diagnostic value of PAPP-A (77.8%) and P4 (87.5%) was greater. Biochemical monitoring of treatment was best achieved with trophoblastic derived antigens (HCG), whereas antigens of maternal origin demonstrated widely varied responses. This study established the effectiveness of chemotherapy for treatment of tubal pregnancies as an alternative to surgery, but if a biochemical marker is required, the marker of choice is HCG.

Progesterone antagonist RU 486 accommodates but does not induce labour and delivery in primates

The hormonal mechanisms of parturition in primates remain controversial. Even so, the well-known decrease of plasma progesterone concentration near term is considered by many as the 'labour inducer'. The progesterone antagonist RU 486, which blocks progesterone activity at the cellular receptor level, appears to be a useful hormonal tool by which to study this tissue. Here, we tested its capacity to induce labour and delivery. A total of 23 Cynomolgus monkeys (Macaca fascicularis), within 9-17 days of expected term, were assigned to four different protocols to study various doses, routes and regimens of RU 486 administration. Observations included uterine contractile patterns, pharmacokinetics of RU 486 in plasma and passage of RU 486 into breast milk. None of the protocols tested successfully induced labour resulting in vaginal delivery within 24 h. Instead, the data demonstrate that blockade of progesterone activity by the progesterone antagonist was not sufficient by itself to achieve parturition in these primates. Uterine myometrial contractile activity under RU 486 exposure was not sufficient to induce labour and delivery. Moreover, the progesterone antagonist concentration in breast milk was very low, indicating little passage to suckling newborn infants.

Human preovulatory follicular fluid: inhibin and free steroids related to optimal follicular maturation in ovarian stimulation regimes and possible function in ovulation

Concentrations of inhibin, total and free oestradiol and progesterone were determined in preovulatory follicular fluid from 15 women undergoing in-vitro fertilization and embryo transfer treatment. The women underwent ovarian stimulation using clomiphene citrate and human menopausal gonadotrophin (HMG) (69 follicular fluid samples) in one cycle, and gonadotrophin-releasing hormone agonist (GnRHa) and HMG stimulation in the next treatment cycle (64 follicular fluid samples). The women thereby served as their own control. Inhibin, total oestradiol and progesterone were measured by radioimmunoassay. Concentrations of free steroid were calculated after quantitation of the steroid binding proteins, i.e. sex-hormone binding globulin (SHBG), cortisol binding protein (CBP) and albumin. Levels of inhibin and free and total progesterone were significantly higher in follicular fluids collected after stimulation with the GnRHa compared to the clomiphene regime (P less than 0.05, P less than 0.001, P less than 0.001, respectively). In contrast, levels of total and free oestradiol in follicular fluid were significantly lower after stimulation with GnRHa than after clomiphene stimulation (P less than 0.001). These results indicate that the follicles have achieved a more optimal maturation during the GnRHa regimen than during the clomiphene regime. It is suggested that the concentration of free biologically active steroids in follicular fluid, released into the peritoneal cavity during ovulation, may be physiologically important in stimulating the oviduct and the uterus in connection with ovulation, pre-embryo development and implantation.

Radioimmunoassay of inhibin based on synthetic human inhibin alpha-chain peptide

Polyclonal rabbit antisera were produced against cyclic human inhibin [(Cys6, Tyr7) alpha-(6-30)NH2] peptide, covalently conjugated to bovine serum albumin. The tyrosine residue introduced at position 7 facilitated the oxidative incorporation of radiolabel (125I) to yield a tracer with specific activity of 73.9 Ci/g. These reagents were used to develop a homologous equilibrium radioimmunoassay for human inhibin, with polyethylene glycol, 200 g/L, serving as the separation phase. At a detection limit of 2 micrograms/L (n = 7), immunoactive inhibin was detectable in human pre-ovulatory follicular fluid (128 micrograms/L), seminal plasma (2374 micrograms/L), amniotic fluid (66 micrograms/L), and placental extract (347 micrograms/L). We also demonstrated inhibin immunoreactivity in biological fluids from other mammalian species: macaque, chimpanzee, porcine, and bovine, but not rodent (guinea pig). Although the antisera were raised against a nonbioactive inhibin peptide, immunoglobulins fractionated on Protein A-Sepharose neutralized the bioactivity of human ovarian inhibin. Further characterization of inhibin immuno- and bioactivity was undertaken with immobilized heparin, divalent metal cations, and dye ligands. Only heparin-Sepharose distinguished between immuno- and bioactive inhibin.

Pregnancy-associated plasma protein A interaction with heparin: a critical appraisal

Positive affinity chromatography on heparin-Sepharose has proved a most crucial step in the purification of pregnancy-associated plasma protein A (PAPP-A). In this chromatographic procedure, PAPP-A was purified almost 500-fold from term pregnancy serum. Further purification was achieved by gel filtration and negative immunoaffinity chromatography. Both PAPP-A and free heparin inhibited granulocyte elastase (HGE) activity. Whereas free heparin inhibited only in hypotonic buffers, PAPP-A inhibited HGE in hypertonic buffers also. However, PAPP-A did not inhibit other proteases (trypsin, chymotrypsin, plasmin, fibroblast collagenase) or proteolytic cascades (complement activation). Since heparin was not detected in the purified PAPP-A, the inhibition of HGE was not due to desorbed or leeched heparin ligand.

Radioimmunoassay of inhibin based on synthetic human inhibin alpha-chain peptide

Polyclonal rabbit antisera were produced against cyclic human inhibin [(Cys6, Tyr7) alpha-(6-30)NH2] peptide, covalently conjugated to bovine serum albumin. The tyrosine residue introduced at position 7 facilitated the oxidative incorporation of radiolabel (125I) to yield a tracer with specific activity of 73.9 Ci/g. These reagents were used to develop a homologous equilibrium radioimmunoassay for human inhibin, with polyethylene glycol, 200 g/L, serving as the separation phase. At a detection limit of 2 micrograms/L (n = 7), immunoactive inhibin was detectable in human pre-ovulatory follicular fluid (128 micrograms/L), seminal plasma (2374 micrograms/L), amniotic fluid (66 micrograms/L), and placental extract (347 micrograms/L). We also demonstrated inhibin immunoreactivity in biological fluids from other mammalian species: macaque, chimpanzee, porcine, and bovine, but not rodent (guinea pig). Although the antisera were raised against a nonbioactive inhibin peptide, immunoglobulins fractionated on Protein A-Sepharose neutralized the bioactivity of human ovarian inhibin. Further characterization of inhibin immuno- and bioactivity was undertaken with immobilized heparin, divalent metal cations, and dye ligands. Only heparin-Sepharose distinguished between immuno- and bioactive inhibin.

Immunization of merino ewes with a synthetic inhibin peptide or with preparations obtained from bovine and porcine follicular fluids by immunoaffinity chromatography result in different effects on ovulation rate and on plasma gonadotrophin concentrations

Ewes were immunized with either a synthetic peptide (peptide 1-32) that has an amino acid sequence identity with the first 32 amino acids at the amino terminal of the alpha-subunit of porcine inhibin, or with bovine or porcine monoclonal antibody purified inhibin (bMPI and pMPI respectively), obtained by immunochromatography from follicular fluids. The peptide 1-32 was conjugated to albumin before use. Peptide 1-32 and bMPI increased ovulation rate and number of follicles (greater than or equal to 5 mm diameter). Although bMPI increased plasma FSH concentration the peptide did not. pMPI had no effect on ovarian activity but markedly elevated both plasma FSH and LH concentrations. The plasma LH concentration was lowered in ewes immunized with peptide 1-32. It appears, therefore, that ovulation rate can be increased following increased plasma FSH concentrations at luteolysis or in the absence of such an increase. Conversely, greatly increased plasma gonadotrophin concentrations at luteolysis (pMPI) were not followed by an increase in ovulation rate. Antibodies in the plasma of ewes immunized with peptide 1-32 and bMPI bound to iodinated synthetic human inhibin alpha-chain 6-30 peptide. The results suggest that ovulation rate is at least partly determined by intraovarian factors.

Immunocytochemical studies of hamster oocyte activation

By indirect immunofluorescence, using rabbit anti-heparin-binding placental protein (HBPP) antiserum, we studied HBPP expression by physiologically and non-physiologically (microsurgically) activated hamster gametes. Whereas mature gametes (sperm, metaphase II oocytes) were negative, in vivo conceived preimplantation embryos, from pronuclear to two- and four-cell stages, were HBPP positive. No HBPP was demonstrated in the zona pellucida, but HBPP-dependent immunofluorescence was localized in the perivitelline space. Oocytes incubated with hyaluronidase demonstrated variable responses from negative to positive. (Diluent or sperm) microinjected oocytes were all activated and HBPP positive within 4 h after stimulation. Thus neither activation by microinjection nor HBPP expression required paternal gametes. These kinetics suggest that HBPP may be a cortical granule secretogogue which can be applied to monitor oocyte responses during in vitro manipulations.

A protein marker of hamster oocyte fertilization

Using a polyclonal rabbit antiserum directed against guinea-pig heparin-binding placental protein (HBPP), we have demonstrated by indirect immunofluorescence the expression of this antigen by hamster preimplantation embryos. HBPP was localized to blastomeres, but not to the zona pellucida, of hamster preimplantation embryos conceived in vivo. Hamster embryos, from the pronuclear to hatched blastocyst stages, were HBPP-positive with greatest immunofluorescence detected at the pronuclear to 2-cell stages. Thereafter, HBPP-dependent fluorescence diminished. By contrast, mature spermatozoa and unfertilized metaphase II oocytes were HBPP negative. Direct microinjection of spermatozoa or diluent through the zona pellucida and into the ooplasm activated the oocytes to express HBPP. These findings demonstrate that expression of HBPP is a post-conceptional event limited to fertilized (or activated) oocytes and that transcription of paternal genomes was not required for HBPP expression. The distribution and temporal kinetics suggest that HBPP may be secreted or released by activated cortical granules into the perivitelline space and concentrated at the oolemma. Whereas hamster embryos conceived in vivo consistently demonstrated a uniformly distributed immunofluorescence, non-viable and degenerate embryos showed weak and patchy reactions. Thus, we have identified a heparin-interacting protein which may serve as a marker of in-vivo and in-vitro oocyte activation and embryo quality.

A baboon model for pregnancy-associated antigens (PAPP-A, PP5, PP14)

By radioimmunoassays established on human derived antigens, PAPP-A, PP5 and PP14 immunoreactivity was detected in placental extracts and blood of pregnant baboons. None of the serial dilution curves suggested parallelism between respective human and baboon samples. Based on slopes of regressed logit-log transformed binding data, PAPP-A demonstrated the greatest degree of interspecies immunological crossreactivity. PP14 showed the least conservation of antigenic determinants. Physicochemical characterization on heparin, zinc chelate and bovine thrombin affinity matrices could not distinguish human from baboon-derived antigens. As in the human, baboon PAPP-A and PP5 were not detected in blood of male or non-pregnant animals. PP14 was detected in baboon follicular fluid, and only PP5 immunoreactivity was measured in culture media of baboon embryos. Of the three antigens, PAPP-A was detected in pregnant baboons at about 61 days gestation, that is, 4 weeks before PP5 and PP14. With the exception of PP14 which attained peak concentration at 118 days of pregnancy, PAPP-A and PP5 concentrations were greatest at term. In conjunction with physicochemical and immunological criteria, these physiological kinetics clearly support a role for developing a baboon model to serve for further studies into feto-maternal signals, particularly antigens such as PAPP-A and PP5.

Molecular characterization of pregnancy-associated plasma protein-A by electrophoresis

Gradient polyacrylamide gel electrophoresis, isoelectric focusing and multidimensional immunoelectrophoretic techniques have been applied in order to physico-chemically characterize pregnancy-associated plasma protein-A (PAPP-A). By lectin affinity immunoelectrophoresis, PAPP-A contained sialic acid, glucose/mannose and N-acetyl-alpha-D-galactosamine. Immunoelectrophoretic analyses after incubation with various glycolases confirmed these findings and demonstrated that PAPP-A contained glucuronic acid, perhaps in chondroitin sulphate moities, thus indicating that PAPP-A may be a proteoglycan rather than a glycoprotein. Analysis by metal chelate and dye ligand affinity immunoelectrophoresis demonstrated many similarities between PAPP-A and alpha 2-macroglobulin (alpha 2M). However, unlike alpha 2M, PAPP-A did not form immunologically reactive complexes when incubated with proteases. Furthermore, as demonstrated by autoradiographic studies, PAPP-A did not contain internal thiolester groups, thus indicating that PAPP-A cannot inhibit proteases by molecular entrapment and, despite the homotetrameric molecular conformation, PAPP-A and alpha 2M may not have evolved from a common ancestral protein.

RU 486 mediated leukocytic inflammatory reaction at the utero-placental interface

Placentae obtained from RU 486 treated cynomolgus monkeys, with successful pregnancy outcome, could not be distinguished, by microscopic or macroscopic examination, from normal placental morphology of untreated females. However, circulating PAPP-A levels were markedly depressed in RU 486 treated (114.8 +/- 13.1 IU/l) than in control animals (477.2 +/- 150 IU/l), suggesting compromised placental physiology. Microscopic examination of placental tissue obtained from animals with fetal demise, after RU 486 administration, revealed pathological changes. When fetal demise occurred recently (less than 24 h), active villus destruction by infiltrating polymorphonuclear leukocytes was readily observed. Whereas aqueous extracts of placentae, whether obtained by cesarean section or spontaneous delivery, inhibited neutrophil elastase (HGE) activity, extracts of placenta being degraded by host phagocytic-proteolytic defense system were rich in HGE activity. Thus suggesting that parturition was not mediated by leukocyte lysosomal proteases, such as HGE, and that hemochorrially implanted placentae produce PAPP-A, a specific inhibitor of HGE. Administration of RU 486 decreased placental PAPP-A production and secretion, culminating with a neutrophilic infiltration into placental intervillous blood spaces, destruction of villus structure and fetal demise.

RU 486 induced suppression of placental neutrophil elastase inhibitor levels

After administration of RU 486 to pregnant cynomolgus monkeys, placental morphology varied from normal to pathological. In all cases (n = 5) circulating and placental PAPP-A levels were markedly suppressed by 76.0 per cent and 55.5 per cent, respectively. When fetal demise occurred within 24 h prior to caesarian section, morphological changes consistent with an active inflammatory (polymorphonuclear leukocytosis) reaction was readily observed at the utero-placental interface, degrading the chorionic villi. Whereas heparin-Sepharose fractionated aqueous extracts of placentae inhibited human neutrophil (or granulocyte) elastase (HGE) activity, extracts of placenta being degraded by host phagocytic-proteolytic defense system were rich in HGE activity. This study establishes: (1) the cynomolgus monkey as a model for PAPP-A studies, (2) that haemochorially implanted placentae produce PAPP-A, a heparin-binding inhibitor of HGE, (3) that administration of progesterone receptor antagonist suppressed placental PAPP-A synthesis, and (4) disrupted protease-protease inhibitor equilibrium at the feto-maternal interface. Thus supporting a role for progesterone in placental PAPP-A production and maintenance of a placental barrier against maternal phagocytic-proteolytic defenses.

Pregnancy-associated protein-A does not improve predictability of pregnancy success or failure over human chorionic gonadotropin levels in early normal and abnormal pregnancy

In the present study we sought to compare levels of PAPP-A and hCG produced by different types of pregnancy: normal, ectopic, threatened abortion and molar pregnancy after evacuation. The gestations ranged from 13 to 122 days. Serum levels of both PAPP-A and hCG were measured and compared. Chi squares analysis were predictive only for increasing trends in hCG as well as decreasing trends of both hCG and PAPP-A. Analysis of variance and linear discriminant function used to evaluate results suggested that PAPP-A did not improve predictability of hCG. The values of PAPP-A levels for the postevacuation molar pregnancies barely exceeded the lower limit of detection; thus, no meaningful comparisons could be made.

Predictive value of a single serum pregnancy associated plasma protein-A or progesterone in the diagnosis of abnormal pregnancy

The value of a single measurement of serum levels of pregnancy associated plasma protein-A (PAPP-A) or progesterone (P4) in predicting abnormal gestations was assessed in 65 patients. P4 was greater than 20 ng/ml (mean +/- SEM 61.2 +/- 6.6 ng/ml, range 22.4-100.0 ng/ml) in all patients with normal intrauterine pregnancies (n = 21), and greater than 20 ng/ml (mean +/- SEM 8.5 +/- 3.9 ng/ml, range 0.1-68.8 ng/ml) in 16 out of 17 patients destined to abort spontaneously. Patients with ectopic gestations (n = 27) exhibited P4 values less than 20 ng/ml (mean +/- SEM 6.4 +/- 1.2 ng/ml, range 0.1-17.2 ng/ml). P4 levels in normal pregnancies were significantly higher (P = 0.001) than those of abnormal gestations. PAPP-A levels ranged from undetectable to 6448 mIU/ml in normal gestations. In 42 out of 44 abnormal pregnancies levels of PAPP-A were less than 100 mIU/ml, as were 7 out of 14 normal intrauterine pregnancies of less than 7 weeks gestational age. No ectopic demonstrated a value of PAPP-A greater than 50 mIU/ml and in 23 out of 27 ectopics, levels were undetectable. However, PAPP-A was less specific than P4 in correctly discriminating normal from abnormal gestations and exhibited lower positive and negative predictive values. It can be concluded therefore that a single PAPP-A measurement is of limited value in discerning normal from abnormal pregnancy prior to 8 weeks gestation. However, a single serum P4 is highly accurate and specific in detecting abnormal pregnancy, regardless of gestational age.

Identification of gonadotropin surge-inhibiting factor (GnSIF) in follicular fluid and its differentiation from inhibin

Exposure of rat pituitary cell cultures to charcoal-extracted porcine follicular fluid (pFF) inhibits gonadotropin-releasing hormone (GnRH) stimulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release in a dose-dependent manner. The inhibition of GnRH-stimulated gonadotropin secretion (gonadotropin surge-inhibiting factor [GnSIF] activity) by pituitary cells in vitro requires up to 24-48 h preexposure to pFF. One microliter of pFF inhibits approximately 50% of the GnRH-stimulated LH release and is defined as 1 unit of GnSIF activity. Basal LH secretion is unaltered under these conditions. GnSIF activity is distinct from that of inhibin, which selectively suppresses basal release of FSH but not LH. A partially purified preparation of inhibin contains less than 1% as much GnSIF activity as inhibin activity. GnSIF activity is resistant to moderate heat treatment (60 degrees C for 60 min) and is fully recovered after acetone precipitation. Chromatography of pFF on heparin/Sepharose affinity matrix effectively separates inhibin from GnSIF. Whereas inhibin has a high affinity for heparin, GnSIF activity does not associate with this affinity matrix and is recovered in the column void volume. In summary, we have developed an in vitro bioassay for the detection of GnSIF activity in pFF. Moreover GnSIF activity seemingly derives from a molecular entity distinct from inhibin, having different physicochemical characteristics and differential effects on pituitary gonadotropin secretion.

Erythrocyte cation fluxes during the menstrual cycle in normal female subjects

1. Studies of erythrocyte cation transport mechanisms in vitro were performed on eight normotensive, premenopausal female subjects at the mid-points of the follicular and luteal phases of their menstrual cycles. Concurrent plasma concentrations of 17 beta-oestradiol, progesterone, aldosterone and renin activity were measured. 2. Ouabain-resistant, frusemide-resistant rubidium influx (an index of passive potassium diffusion) was significantly lower in the luteal than the follicular phase. 3. In further studies in four of the eight subjects, the mean rate constant of the rubidium influx measurement was also lower in the luteal than in the follicular phase. 4. There were no changes in Na+-K+ co-transport, sodium pump activity or intracellular cation concentrations throughout the cycle. 5. There was a tenfold fall in the mean plasma 17 beta-oestradiol/progesterone ratio, as well as increases in plasma aldosterone concentration and renin activity between the mid-follicular and mid-luteal phases. 6. We conclude that changes in plasma oestrogen/progesterone ratio during the menstrual cycle may be associated with alterations in passive potassium diffusion.

Production of pregnancy-associated plasma protein-A (PAPP-A) by cultured tumour granulosa cells

Ten ovarian and 2 cervical tumour cell lines were analysed for the production of pregnancy-associated proteins. Pregnancy-associated plasma protein-A (PAPP-A) was detected by radioimmunoassay in culture media of 2 out of 4 (50%) tumour granulosa cell lines (mean = 104 microIU/10(5) cells/24 h) but not in any ovarian (n = 6) or cervical (n = 2) tumour cell lines. By contrast, human chorionic gonadotrophin (hCG), pregnancy specific beta 1-glycoprotein and alpha-fetoprotein (AFP) were not detected in any of the PAPP-A positive media. Only two cell lines produced hCG (58.5 and 25.5 mIU/10(5) cells/24 h). No AFP was produced by any of these 12 cell lines, whereas placental protein 5 was positive in 7. None of these proteins were detected in the culture media of 4 cell lines. In vitro derived PAPP-A was immunologically indistinguishable from either pregnancy or ovarian follicular PAPP-A. All PAPP-A species interacted reversibly with immobilised heparin and were determined by molecular sieve chromatography to have an apparent molecular weight of 820,000 daltons. Cultured tumour granulosa cells specifically synthesised and secreted a large protein which was immunologically and physicochemically indistinguishable from in vivo (pregnancy and ovarian follicular) derived PAPP-A.

Potential role of pregnancy-associated plasma protein-A in human reproduction

By radioimmunoassay, pregnancy-associated plasma protein-A (PAPP-A) was undetectable in matched follicular and luteal phase serum samples (n = 17) or in the peripheral circulation of normal males (n = 17). However, seminal plasma (91.5%), cervical mucus (100%) and pre-ovulatory follicular fluid (99.6%) were consistently PaPP-A positive. In addition to PAPP-A, four circulating protease inhibitors (PIs) were detected in pooled seminal plasma whereas pooled follicular fluid contained an additional six. Follicular concentrations of serum PIs were inversely related to molecular size. By contrast, PAPP-A formed a positive concentration gradient across the blood-reproductive tract barrier suggesting PAPP-A production within the reproductive tract. A minor proportion (1.7%) of ejaculated spermatozoa were coated with PAPP-A, as demonstrated by direct immunofluorescence. Since PAPP-A specifically inhibits leucocyte elastase, it is suggested that PAPP-A coated spermatozoa were "selected" to overcome localized phagocytic-proteolytic degradation. The physiological significance of these findings are discussed in relation to human reproduction.

Comparison of different antibody preparations against pregnancy-associated plasma protein-A (PAPP-A) for use in localization and immunoassay studies

Four antibody preparations against pregnancy-associated plasma protein (PAPP-A) were compared in order to find an explanation for the contradictory results published on tissue localization, clinical usefulness and biological function of PAPP-A. One of the preparations studied was a rabbit anti-PAPP-A antiserum which has been offered for general scientific use (Bischof et al. 1979). Only the IgG fraction of anti-PAPP-A antisera which appeared to be monospecific and had been further absorbed with fetal connective tissue gave specific uniform staining of the cytoplasm of the syncytiotrophoblast exclusively. Circulating PAPP-A could not be detected by RIA employing this IgG preparation in the non-pregnant state, or before 18 days after conception. Circulating PAPP-A could be detected in all seven pregnant women studied within 4 weeks after conception. Identical results were obtained with a commercially available IgG fraction against PAPP-A.

Potassium regulation and progesterone-aldosterone interrelationships in human pregnancy: a prospective study

Little is known about the intrinsic renal and hormonal regulation of potassium excretion in pregnancy despite major alterations in many of the potassium regulatory factors. Forty primigravid women on an unrestricted diet were studied during the second and third trimesters and exhibited constant absolute and fractional potassium excretion despite a significant increase in plasma aldosterone concentration between these stages. The plasma progesterone level rose significantly between studies but closer analysis showed no correlation between individual changes in plasma aldosterone concentration and progesterone between trimesters. In the 14 subjects studied post partum, baseline absolute potassium excretion was not significantly altered but filtered potassium fell and fractional potassium excretion tended to rise. After dietary sodium manipulation at these stages, absolute potassium excretion, fractional potassium excretion, and progesterone were unaltered despite significant changes in plasma aldosterone concentration and sodium excretion. These results suggest that potassium excretion is held constant throughout pregnancy and that renal tubular potassium reabsorption adjusts appropriately to the increased filtered potassium load. Progesterone does not appear to be involved in the acute regulation of potassium or sodium excretion but may have effects on sodium and potassium excretion that are constant, proportional to its placental production, and unresponsive to endogenous changes in mineralocorticoid production.

Demonstration of pregnancy-associated plasma protein-A (PAPP-A)-like material in the fallopian tube

The distribution and concentration of pregnancy-associated plasma protein-A (PAPP-A) in the human fallopian tube were examined by the immunoperoxidase staining technique and radioimmunoassay as part of a detailed study of PAPP-A in the nonpregnant state. PAPP-A-like material was identified in the epithelial cells of the mucosa in all fallopian tube specimens examined (n = 21). The intensity of the staining for PAPP-A was unrelated to the phase of the menstrual cycle. PAPP-A-like material was detected in saline extracts from all tubal tissues (n = 14) but not in any of the sera obtained from the same patients. The tissue concentration (mean +/- standard error of the mean) of immunoreactive PAPP-A varied from 15.2 +/- 1.1 to 30.1 +/- 4.2 micrograms/g protein in different parts of the tubes. No difference in the PAPP-A concentration was found between isthmic, ampullar, and fimbrial part of the tube, but proliferative phase tube seems to contain more PAPP-A than secretory phase tube. The PAPP-A measured in the fallopian tube appears to be similar in molecular size and antigenicity to that of pregnancy.

Failure of implantation in human in vitro fertilization and embryo transfer patients: the effects of altered progesterone/estrogen ratios in humans and mice

Daily blood samples were taken for progesterone (P) and estradiol (E2) measurements from women who showed a platelet response consistent with the presence of viable embryos after in vitro fertilization and embryo transfer procedures. A comparison of steroid levels between those women who became pregnant and those who did not revealed the following: at and after the time of transfer, women who failed to become pregnant had significantly higher E2 levels and a lower ratio of P/E2 than women who became pregnant. The P/E2 ratio was a better predictor of implantation failure than was the absolute level of either hormone. Experiments were done in mice to test the hypothesis that P could protect implantation of the embryo against the inhibitory effects of high E2. In mice, implantation was inhibited by relatively high levels of E2. This effect was overcome by concomitant administration of P. There was a significant dose-response-related interaction of P with the E2.

Circulating and tissue concentrations of pregnancy-associated plasma protein-A (PAPP-A) in tubal ectopic gestation

Concentrations of pregnancy-associated plasma protein-A (PAPP-A), human chorionic gonadotrophin (hCG) and pregnancy specific beta 1-glycoprotein (SP1) were measured by radioimmunoassay in 164 serum and 29 tissue samples obtained from 87 non-pregnant and 29 pregnant women with either tubal (n = 16) or intrauterine (n = 13) pregnancies. Of the 47 serum samples obtained from patients with a tubal pregnancy only two were positive for PAPP-A, whereas in excess of 94% of the samples were positive for both hCG and SP1. Serial measurements of hCG, and SP1, demonstrated an apparently normal growth rate for the tubally implanted trophoblast for the first 6 weeks of pregnancy. Thereafter, the tubal trophoblast is compromised since the tissue content of PAPP-A and hCG was significantly lower than that in intra-uterine derived trophoblastic tissue. By contrast, the content of both PAPP-A and hCG was significantly greater in the trophoblastic, both intra or extra-uterine derived, than in the endometrial/decidual, tissue. Furthermore, the absence of immunoreactive PAPP-A and the severely depressed circulating levels of PAPP-A in women with tubal pregnancies can be attributed to diminished secretion of PAPP-A into the maternal circulation. Therefore, in conjunction with a positive pregnancy test and the patient's clinical history, a severely depressed or absent serum PAPP-A level may aid in the diagnosis of extrauterine pregnancy.

Monitoring of postimplantation embryo viability following successful in vitro fertilization and embryo transfer by measurement of placental proteins

Serum levels of pregnancy-associated plasma protein A (PAPP-A), human chorionic gonadotropin (hCG), and pregnancy-specific beta 1-glycoprotein (SP1) were measured in 21 women after successful in vitro fertilization and embryo transfer. Of the 21 pregnancies, 14, including 1 twin gestation, progressed successfully to term. The remaining seven, composed of tubal (n = 3), anembryonic (n = 1), and spontaneously aborted (n = 3) pregnancies, failed during the first half of pregnancy. Placental protein measurement was of no diagnostic value in the detection of anembryonic pregnancy. Similarly, measurement of hCG and SP1 could not readily distinguish tubal ectopic from normal intrauterine pregnancies. By contrast, the predictive value (38.9%) of a depressed PAPP-A level in conjunction with superior diagnostic sensitivity (70%) and relative risk factor (23.6) proved to be of greater diagnostic value in this potentially lethal condition. In the absence of ultrasonography, the biochemical diagnostic indices were comparable in the prediction of spontaneous abortion. However, in the presence of a live fetus, PAPP-A levels were consistently depressed (sensitivity, 91.7%) many weeks before pregnancy demise. The relative risk factor of depressed PAPP-A levels was 29 times greater than the risk associated with a depressed hCG level. These findings further demonstrate the potential diagnostic value of PAPP-A measurement for monitoring postimplantation embryo viability.

Maternal blood platelet physiology and luteal-phase endocrinology as a means of monitoring pre- and postimplantation embryo viability following in vitro fertilization

The discovery that the fertilized mouse ovum triggers an increased demand for platelets and results in thrombocytopenia during the preimplantation phase of pregnancy provides a monitor for embryo survival and viability. This paper reports a study in which the platelet count was significantly reduced throughout the human preimplantation phase of pregnancy and returned to normal following embryo implantation. The human embryo was shown to produce a platelet activating factor in vitro which caused the reduction in platelet count after embryo transfer. This factor in the embryo culture medium could be measured using a bioassay which provided a means of assessing embryo viability prior to transfer. Some women showed no reduction in platelets after transfer. These embryos failed to produce a platelet activating factor in vitro and pregnancy was not established. Other women displayed a reduction in platelets following transfer but failed to become pregnant. All of these women had elevated luteal-phase plasma E2 levels compared to pregnant patients, which may have interfered with the implantation process. Our observations provide a possible rapid and simple means for monitoring the viability of human embryos cultured in vitro and the survival of embryos in utero.

Pregnancy-associated plasma protein-A and placental protein 5 in human seminal plasma

Human seminal plasma contains two glycoproteins which are physiochemically and immunologically indistinguishable from pregnancy-associated plasma protein-A and placental protein 5. Seminal concentrations of both glycoproteins did not correlate with clinical assessment of semen quality. Furthermore, analysis of split ejaculates indicated a nontesticular origin for both proteins, which are possibly secreted into the distal portions of the tract by the accessory glands (prostate gland and seminal vesicles). The physiological significance of these findings has yet to be determined. However, it is suggested that pregnancy-associated plasma protein-A, a known potent inhibitor of leukocyte elastase, protects the deposited sperm against proteolytic attack originating from the localized leukocyte reaction within the female reproductive tract, thus contributing towards sperm survival within this immunologically hostile environment and enabling fertilization to occur.

Monitoring of postimplantation embryo viability by measurement of PAPP-A, SP1, and hCG

After successful in vitro fertilization and embryo transfer, chorionic gonadotropin, pregnancy-specific beta 1-glycoprotein, and pregnancy-associated plasma protein-A were measured in serum samples collected serially from 21 patients. While 14 pregnancies, including one twin pregnancy, progressed successfully to term, the remaining seven pregnancies failed during the first half of gestation. This latter group consisted of three tubally implanted, one anembryonic, and three spontaneously aborted pregnancies. Circulating levels of hCG, SP1, and PAPP-A in the patient with an anembryonic pregnancy were within normal limits. Similarly, 90.5% of the serum samples obtained from women with tubal pregnancies showed hCG levels within normal limits. By contrast, only two of these samples had detectable PAPP-A, of which only one was within normal limits. Of the samples obtained from the patients who spontaneously aborted, including one patient with normal ultrasonic findings up to 48 hours prior to the event, 85.7% had PAPP-A concentration below the 10th percentile, whereas only 16.7% of these samples showed depressed hCG levels. These data suggest that PAPP-A measurement has great clinical potential in the management of compromised early pregnancies.