Current topic: pre-eclampsia and the placenta

Expression of urokinase, plasminogen activator inhibitors and urokinase receptor in pregnant rhesus monkey uterus during early placentation

We have investigated plasmin mediated proteolysis associated with trophoblast invasion during early stages of pregnancy in the rhesus monkey. In situ hybridization and immunocytochemical localization were used to define the cellular and tissue distribution of urokinase plasminogen activator (uPA), plasminogen activator inhibitor type 1 (PAI-1) and 2 (PAI-2) and urokinase receptor in early monkey placenta and uterus. Our results indicate: (1) uPA is expressed in proliferating and invasive cytotrophoblast located in chorionic villi as well as in extravillous trophoblast associated with uterine arterioles. This raises the possibility that urokinase may play an important role in trophoblast invasion. (2) PAI-1 mRNA is specifically localized in two areas where invasive trophoblast cells encounter maternal tissue directly. The extravillous cytotrophoblast cells at the maternofetal junction express PAI-1 mRNA. The invasive endovascular trophoblast cells within the uterine arterioles also express PAI-1 mRNA. The location sensitive expression of PAI-1 mRNA at the maternofetal junction may imply a protective function of this protease inhibitor that might be induced through interaction with decidual cells. (3) Urokinase receptor antigen has also been found at the maternofetal junction and in endovascular trophoblast cells of the invaded maternal blood vessel. (4) PAI-2 immunoreactivity is found in association with cytotrophoblast cells in anchoring choronic villi suggesting its association with early placentation. In conclusion, we propose that the plasmin/plasminogen activator system may not only regulate extracellular matrix degradation, but also modify migration and invasive behaviour of extravillous trophoblast cells, during early placentation.

Adhesion molecules of syncytiotrophoblast microvillous membranes inhibit proliferation of human umbilical vein endothelial cells

It has been shown previously that syncytiotrophoblast microvillous membranes (STBM), isolated from normal or pre-eclampsia placentae, specifically inhibit the proliferation of cultured human umbilical vein endothelial cells (HUVEC) and disrupt the cell monolayer without causing cell death. We have previously shown that this anti-proliferative activity resides in a self-aggregating complex in which eight proteins, namely integrins alpha(5)(CD49e) and alpha(V)(CD51), dipeptidyl peptidase IV (DPP IV, CD26), alpha-actinin, transferrin receptor (TfR, CD71), transferrin, placental alkaline phosphatase (PLAP) and monoamine oxidase A (MAO-A) were identified. In the present study, we investigated which of these components causes the anti-proliferative activity of STBM. Antibodies against integrin alpha(5)and alpha(V)and DPP IV all reduced the STBM-induced inhibition of proliferation of HUVEC, which was also reversed by added fibronectin. A preparation of PLAP inhibited endothelial proliferation, but this was not due to enzymatic activity. The preparation was shown to be impure with more than 12 bands present on Coomassie blue stained SDS-PAGE gels. These included integrins alpha(5)and alpha(V), which could account, at least in part, for the inhibitory activity. We could not exclude, however, the possibility of other unidentified factors being involved. We conclude that adhesion molecules account for a major part of the anti-proliferative activity of STBM; these appear to compete for ligands in the extracellular matrix or serum with the appropriate receptors on HUVEC.

Preeclampsia: what we know and what we do not know

Preeclampsia remains a major health problem for mothers and infants. Studying the entire pathophysiology of preeclampsia rather than "pregnancy-induced hypertension" has greatly expanded our knowledge of the disorder. Current thinking approaches preeclampsia as a 2 stage disorder: reduced placental perfusion usually secondary to abnormal implantation and a consequent maternal disorder characterized by endothelial dysfunction and subsequent pathophysiological changes. We know much about the 2 stages and less about their linkage. It is evident that reduced placental perfusion is not sufficient to account for the pathophysiology. Reduced perfusion and abnormal implantation occur in other conditions (intrauterine growth restriction and preterm labor) without the maternal syndrome. This leads to the hypothesis that reduced placental perfusion must interact with maternal constitutional factors to generate the systemic pathophysiology of preeclampsia. The similarities of these risk factors and metabolic alterations between preeclampsia and atherosclerosis suggest a common pathophysiology. Oxidative stress is postulated as the genesis of endothelial dysfunction in atherosclerosis. The author proposes that oxidative stress secondary to reduced placental perfusion leads to endothelial dysfunction, linking the 2 stages of the syndrome.

Inositol phosphoglycans and signal transduction systems in pregnancy in preeclampsia and diabetes: evidence for a significant regulatory role in preeclampsia at placental and systemic levels

Measurements have been made of the urinary content of inositol phosphoglycans IPG P-type and IPG A-type, putative insulin second messengers, in preeclampsia, in type I insulin-treated diabetic pregnant women and their matched control subjects, and nonpregnant women of child-bearing age. The content of IPG P-type and IPG A-type was also measured in the placenta from preeclamptic patients and from normal pregnancies. Pregnancy was associated with an increase, approximately twofold, in urinary output of IPG-P-type relative to nonpregnant controls (P<0.01). The 24-h output of IPG P-type in urine in preeclamptic women was significantly higher (2- to 3-fold) than in pregnant control subjects matched for age, parity, and stage of gestation (P<0.02). In contrast, insulin-dependent diabetic pregnant women did not show any significant change in urinary output of IPG P-type or IPG A-type relative to pregnant control subjects. Evidence for a possible relationship and correlation between the urinary excretion of IPG P-type and markers of preeclampsia, including proteinuria (r = 0.720, P<0.01), plasma aspartate transaminase (r = 0.658, P<0.05), and platelet counts (r = 0.613, P<0.05) is presented. A high yield of IPG P-type was extracted from human placenta, in preeclampsia some 3-fold higher (P = 0.03) than the normal value, whereas no IPG A-type (with lipogenic-stimulating activity) was found. Low concentrations of placental IPG A-type were detected relative to IPG P-type using assay systems dependent upon the effect of this mediator on cAMP-dependent protein kinase or on a proliferation assay using thymidine incorporation into DNA of EGFR T17 fibroblasts. It is postulated that the high urinary excretion IPG P-type in preeclampsia reflects high placental levels and relates to the accumulation of glycogen in the placenta. The paracrine effects of placental IPG P-type (stimulation off other endocrine glands and/or endothelial cells) could contribute to the pathogenesis of the maternal syndrome. A possible theoretical link between elevated placental IPG P-type and apoptosis is proposed.

Antiplatelet agents for preventing and treating pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, and low dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia, and to those with established pre-eclampsia.

SEARCH STRATEGY

This review drew on the search strategy developed for the Pregnancy and Childbirth Group as a whole. The Cochrane Controlled Trials Register was also searched, The Cochrane Library 1999 Issue 1, Embase was searched from 1994-1999 and hand searches were performed of the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia, and those with pre-eclampsia before delivery. Women treated postpartum were excluded. Interventions were any comparisons of an antiplatelet agent (such as low dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Assessment of trials for inclusion in the review and extraction of data was performed independently and unblinded by two reviewers. Data were entered into the Review Manager software and double checked.

MAIN RESULTS

Forty two trials involving over 32,000 women were included in this review, with 30,563 women in the prevention trials. There is a 15% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents [32 trials with 29,331 women; relative risk (RR) 0.85, 95% confidence interval (0.78, 0.92); Number needed to treat (NNT) 89, (59, 167)]. This reduction is regardless of risk status at trial entry or whether a placebo was used, and irrespective of the dose of asprin or gestation at randomisation. Twenty three trials (28,268 women) reported preterm delivery. There is a small (8%) reduction in the risk of delivery before 37 completed weeks [RR 0.92, (0.88, 0.97); NNT 72 (44, 200)]. Baby deaths were reported in 30 trials (30,093 women). Overall there is a 14% reduction in baby deaths in the antiplatelet group [RR 0.86, (0. 75, 0.98); NNT 250 (125, >10000)]. Small for gestational age babies were reported in 25 trials (20,349 women), with no overall difference between the groups, RR 0.92, (0.84, 1.01). There were no significant differences between treatment and control groups in any other measures of outcome. Five trials compared antiplatelet agents with placebo or no antiplatelet agent for the treatment of pre-eclampsia. There are insufficient data for any firm conclusions about the possible effects of these agents when used for treatment of pre-eclampsia.

REVIEWER'S CONCLUSIONS

Antiplatelet agents, in this review largely low dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment should be started, and at what dose.

Epidermal growth factor in maternal urine--a predictor of intrauterine growth restriction?

Epidermal growth factor (EGF), an angiogenic and mitogenic peptide, is known to be essential for normal fetal development in mice. Hypothetically, low maternal urine EGF levels might be associated with intrauterine growth restriction (IUGR) or pre-eclampsia (PE). We carried out a prospective study of 1009 consecutive women whose urine was sampled in early pregnancy (at a median of 13 weeks of gestation) between January and November 1993. Thirty women gave birth to IUGR babies and 24 developed PE. The study was designed as a nested case-control study with two matched controls for each case. EGF and human chorionic gonadotrophin (HCG) levels were measured and expressed in ng EGF/mg creatinine and IU HCG/mg creatinine. Logistic regression analysis was made with EGF or HCG levels as explanatory variables. Urinary EGF levels were significantly lower in the IUGR subgroup than in their controls, but no such difference was found between the PE subgroup and their controls. In the series as a whole, smokers were found to have lower EGF and HCG levels than non-smokers. In addition, correlation was found to exist between EGF and HCG levels (Spearman's rho 0.35; P<0.001). We conclude that a relative deficiency of EGF in early pregnancy might be one of the pathophysiological mechanisms of IUGR. However, the EGF level was an insufficiently discriminative variable to be of use for screening purposes.

Interleukin-8 stimulates placental prostacyclin production in preeclampsia

PROBLEM

Our purpose was to determine placental interleukin (IL)-8 production and its correlation with the prostacyclin production in normal and preeclamptic pregnancies and to evaluate the beneficial effect of IL-8 on prostacyclin production.

METHOD OF STUDY

We determined 1) the in vitro production of IL-8 and prostacyclin by placental villous tissues from normal and preeclamptic pregnancies and 2) the production of prostacyclin by villous tissues from preeclampsia treated with recombinant human IL-8 (rhIL-8). IL-8 levels were measured by enzyme-linked immunosorbent assay and prostacyclin by radioimmunoassay of 6-keto PGF1alpha, the stable metabolite of prostacyclin.

RESULTS

1) Placental production of IL-8 and 6-keto PGF1alpha were significantly less in preeclampsia than in normal pregnancies, P<0.05. 2) Placental production of 6-keto PGF1alpha and IL-8 was significantly correlated in preeclampsia, P<0.01. 3) Placental tissues treated with IL-8 exhibited a concentration-dependent increase in 6-keto PGF1alpha production.

CONCLUSIONS

Placental tissues from preeclampsia produce significantly less IL-8 than tissues from normal pregnancies, which correlates with decreased prostacyclin production. IL-8 improves placental prostacyclin production in preeclampsia.

Fluid management in pre-eclampsia

We review the evidence base for fluid management in pre-eclampsia. Current understanding of the relevant pathophysiology and the possible impact of styles of fluid management on maternal and fetal outcome are presented. There is little evidence upon which to base the management of fluid balance in pre-eclampsia. Reports are conflicting and no large prospective outcome studies of fluid management have been performed. Volume expansion does not appear to reduce the incidence of fetal distress. Pulmonary oedema and oliguria receive particular attention. There is no evidence of long-term renal damage in pre-eclampsia, but there are strong suggestions that pulmonary oedema is linked to fluid administration. Monitoring is discussed and some principles of management are suggested

Folic acid and homocyst(e)ine metabolic defects and the risk of placental abruption, pre-eclampsia and spontaneous pregnancy loss: A systematic review

Placental infarction or abruption, recurrent pregnancy loss and pre-eclampsia are thought to arise due to defects within the placental vascular bed. Deficiencies of vitamin B12 and folate, or other abnormalities within the methionine-homocyst(e)ine pathway have been implicated in the development of such placental diseases. We conducted a systematic literature review to quantify the risk of placental disease in the presence of these metabolic defects. Studies were identified through OVID Medline between 1966 and February 1999. Terms relating to the measurement of vitamin B12, folic acid, methylenetetrahydrofolate reductase or homocyst(e)ine were combined with those of pre-eclampsia, placental abruption/infarction or spontaneous and habitual abortion. Human studies comprising both cases and controls and published in the English language were accepted. Their references were explored for other publications. Data were abstracted on the matching of cases with controls, the mean levels of folate, B12 or homocyst(e)ine in each group or the frequency of the homozygous state for the thermolabile variant of methylenetetrahydrofolate reductase. The definition of 'abnormal' for each exposure was noted and the presence or absence of the exposure of interest for each outcome was calculated as an absolute rate with a 95 per cent confidence interval. The crude odds ratios were calculated for each study and then pooled using a random effects model. Eighteen studies were finally included. Eight studies examined the risk of placental abruption/infarction in the presence of vitamin B12 or folate deficiency, or hyperhomocyst(e)inaemia. Folate deficiency was a prominent risk factor for placental abruption/infarction among four studies, though not statistically significant (pooled odds ratio 25.9, 95 per cent CI 0.9-736.3). Hyperhomocyst(e)inaemia was also associated with placental abruption/infarction both without (pooled odds ratio 5.3, 95 per cent CI 1.8-15.9) and with methionine loading (pooled odds ratio 4.2, 95 per cent CI 1.2-15.0), as was the homozygous state for methylenetetrahydrofolate reductase (pooled odds ratio 2.3, 95 per cent CI 1.1-4.9). Vitamin B12 deficiency was not a demonstrable risk factor. Eight studies examined blood levels among women with spontaneous abortion or recurrent pregnancy loss. The pooled odds ratios were 3.4 (95 per cent CI 1.2-9.9) for folate deficiency, 3.7 (95 per cent CI 0.96-16.5) for hyperhomocyst(e)inaemia following methionine challenge, and 3.3 (95 per cent CI 1.2-9.2) for the methylenetetrahydrofolate reductase mutation. Five case-control studies examined the relationship between pre-eclampsia and abnormal levels of vitamin B12, folate, homocyst(e)ine or methylenetetrahydrofolate reductase. Folate deficiency was not an associated risk factor (odds ratio 1.2, 95 per cent CI 0.5-2.7), but hyper-homocyst(e)inaemia was (pooled odds ratio 20.9, 95 per cent CI 3.6-121.6). Similarly, homozygosity for the methylenetetrahydrofolate reductase thermolabile variant was associated with a moderate risk of preeclampsia (odds ratio 2.6, 95 per cent CI 1.4-5.1). Some pooled data were associated with significant statistical heterogeneity, however. There is a general agreement among several observational studies that folate deficiency, hyperhomocyst(e)inaemia and homozygosity for the methylenetetrahydrofolate reductase thermolabile variant are probable risk factors for placenta-mediated diseases, such as pre-eclampsia, spontaneous abortion and placental abruption. Vitamin B12 deficiency is less well defined as an important risk factor. Due to the limited quality of these data, including insufficient matching of cases with controls, and possible laboratory measurement bias relating to pregnancy, prospective studies are needed to confirm these findings and guide future preventative and therapeutic research.

Maternal peripheral blood leukocytes in normal and pre-eclamptic pregnancies

OBJECTIVE

To analyse activation of maternal peripheral blood leukocytes by flow cytometric measurements of intracellular free-ionised calcium of lymphocytes, granulocytes and monocytes, separately.

DESIGN

Case-control study.

SETTING

High risk pregnancy service in a regional centre.

MATERIAL

Samples from 10 women with pre-eclampsia, 10 appropriately-matched women with normal pregnancy, nine multigravid normal women at mid-gestation selected as being least likely to demonstrate any tendencies towards pre-eclampsia, and 11 healthy nonpregnant women of reproductive age were studied.

METHODS

Using flow cytometry, intracellular free ionised calcium ([Ca2+]i) was estimated by loading the cells with Fluo-3 and measuring the changes in fluorescence intensity induced by free ionised calcium. After the basal levels were measured, the response of phagocytes to stimulation with n-formylmethionyl-leucyl-phenylalanine (fMLP) was determined.

MAIN OUTCOME MEASURES

Basal [Ca2+]i of peripheral blood leukocytes.

RESULTS

Median basal [Ca2+]i was significantly increased in all three subsets of leukocytes--lymphocytes, granulocytes and monocytes in pre-eclampsia--compared with the three control groups. Samples from both groups of women with normal pregnancy did not differ from those from nonpregnant women. The peak responses of monocytes to stimulation with 10 nmol fMLP were greater in samples from pre-eclamptic women, giving evidence of priming.

CONCLUSIONS

Peripheral blood leukocytes are activated in pre-eclampsia in terms of basal changes in the intracellular second messenger--free ionised calcium. Peripheral blood monocytes are primed to give greater responses after stimulation with fMLP.

Inhibition of TGF-beta 3 restores the invasive capability of extravillous trophoblasts in preeclamptic pregnancies

Preeclampsia, the major cause of maternal morbidity and mortality in developed countries, is associated with abnormalities of placenta function due to shallow invasion of the maternal decidua by trophoblasts. Data suggest that TGF-beta may play a role in inhibiting trophoblast outgrowth or invasion, or both. We report that placental TGF-beta 3 expression is high in early pregnancy but falls at around 9 weeks' gestation. This pattern is inversely correlated with trophoblast outgrowth and fibronectin synthesis, markers of early trophoblast differentiation toward an invasive phenotype. We demonstrate that TGF-beta 3 is overexpressed in preeclamptic placentae. In contrast to control placentae, explants from preeclamptic pregnancies fail to exhibit spontaneous invasion in vitro. Significantly, antisense-induced inhibition of TGF-beta 3 expression, and inhibition of TGF-beta 3 activity with antibodies, induces the formation of columns of trophoblast cells, which migrate out of the explant into the underlying Matrigel. To our knowledge, this is the first demonstration that the hypoinvasive placental phenotype characteristic of preeclampsia can be essentially normalized in vitro by biochemical manipulation. We speculate that a failure to downregulate expression of TGF-beta 3 at around 9 weeks' gestation results in shallow trophoblast invasion and predisposes the pregnancy to preeclampsia.

Ketanserin versus dihydralazine in the management of severe early-onset preeclampsia: maternal outcome

OBJECTIVE

An open, randomized, prospective, multicenter trial was conducted to compare the efficacy and safety of intravenous ketanserin, a selective serotonin 2 receptor blocker, with that of intravenous dihydralazine in the management of severe early-onset (<32 weeks' gestation) preeclampsia. End points of this study were blood pressure control and maternal outcome.

STUDY DESIGN

Patients with a diastolic blood pressure >110 mm Hg were randomly assigned to receive either ketanserin (n = 22) or dihydralazine (n = 22) as initial therapy. Plasma volume expansion preceded antihypertensive treatment, which was administered according to a fixed schedule.

RESULTS

The reductions in blood pressure with the 2 drugs were similar; however, adequate blood pressure control was reached significantly earlier with ketanserin (84 +/_ 63 vs 171 +/- 142 minutes, P = .017). Occurrence of maternal complications was significantly lower among patients who received ketanserin than among patients who received dihydralazine (n = 6 vs n = 18, P =.0007). A significant difference in favor of ketanserin was noted in daily fluid balance.

CONCLUSION

Antihypertensive efficacies of ketanserin and dihydralazine were comparable, but significantly fewer maternal complications were noted among the patients receiving ketanserin. Ketanserin is an attractive alternative in the management of severe early-onset preeclampsia.

Preeclampsia: an excessive maternal inflammatory response to pregnancy

The maternal syndrome of preeclampsia has previously been ascribed to generalized maternal endothelial cell dysfunction. In this review we suggest that the endothelial dysfunction is a part of a more generalized intravascular inflammatory reaction involving intravascular leukocytes as well as the clotting and complement systems. We provide evidence from our recent work and that of others that not only supports this proposal but indicates that such an inflammatory response is already well developed in normal pregnancy and that the differences between normal pregnancy and preeclampsia are less striking than those between the normal pregnant and nonpregnant states. From this we argue that preeclampsia arises when a universal maternal intravascular inflammatory response to pregnancy decompensates in particular cases, which may occur because either the stimulus or the maternal response is too strong. We conclude that there is no specific cause for the disorder, which can be better considered as the extreme end of the range of maternal adaptation to pregnancy. We propose that poor placentation is not the cause of preeclampsia but is a powerful predisposing factor. We predict that a single preeclampsia gene will not be found, nor will either a single specific predictive test or single preventive effective measure be devised. Aspects of the hypothesis are testable, and future work should allow its confirmation or refutation.

New insights into the genetics of preeclampsia

Preeclampsia is familial. Pedigree analyses suggest that one or more common alleles may act as "preeclampsia susceptibility genes." The authors speculate that genes involved in blood pressure control, volume regulation, placental health, vascular disease, and vascular remodeling, underlie familial susceptibility to preeclampsia. Several candidate genes have been examined. These data suggest that a common mutation in the angiotensinogen promoter, A(-6), leads to elevated expression of this gene and pleiotropic effects, including abnormal spiral artery remodeling and failed hypervolemia of pregnancy. The factor V Leiden mutation, which predisposes women to thromboembolic disorders during pregnancy, has been implicated as another preeclampsia susceptibility gene. New insights into the genetics of preeclampsia will contribute to the understanding of this disease and should ultimately lead to improved diagnosis and treatment.

Angiotensinogen Thr235 variant is associated with abnormal physiologic change of the uterine spiral arteries in first-trimester decidua

OBJECTIVE

The angiotensinogen Thr235 polymorphism associated with preeclampsia is tightly linked to a mutation in the angiotensinogen promoter A(-6), which may lead to elevated expression in decidual spiral arteries. We hypothesize that locally elevated angiotensin II levels play a role in failed physiologic change leading to preeclampsia. Our objective was to determine whether spiral artery morphologic characteristics were different in first-trimester decidual samples from women homozygous for the angiotensinogen Thr235 allele and women homozygous for the normal angiotensinogen Met235 allele.

STUDY DESIGN

We used quantitative histologic analysis to study 1266 spiral artery cross-sections in decidual samples obtained from normal pregnancies (n = 53) terminated at 8 weeks' gestation. To define vessel characteristics before pregnancy-induced remodeling, we also examined 60 arteries in nonpregnant endometrial control samples (n = 5). We measured the aspect ratio, media area, and external diameter of each cross-section with Image-Pro plus software. Maternal angiotensinogen genotypes were determined by means of mutagenically separated polymerase chain reaction. Average spiral artery morphologic measurements were compared between genotypes with the Student t test.

RESULTS

The media area/external diameter ratio was lower in decidual samples than in endometrial samples (P <.0001), consistent with pregnancy-induced physiologic changes. Women homozygous for the angiotensinogen Thr235 allele (n = 11) had a greater area/diameter ratio than did women homozygous for the normal angiotensinogen Met235 allele (n = 11, P <.05). Samples from heterozygous women (n = 31) had intermediate values.

CONCLUSION

Our results suggest that the angiotensinogen Thr235 allele predisposes women toward abnormal physiologic change, potentially beginning the cascade of events leading to preeclampsia.

Vascular cell adhesion molecule-1 (VCAM-1) and leukocyte activation in pre-eclampsia and eclampsia

OBJECTIVE

To evaluate the levels of VCAM-1 in pre-eclampsia/eclampsia as a possible marker of leukocyte activation and endothelial damage.

METHODS

We performed a case-control study on 25 healthy pregnant women and 35 patients diagnosed as pre-eclampsia or eclampsia which were randomly selected. Peripheral venous blood samples were obtained and serum levels of VCAM-1 were measured by enzyme-linked immunoassay (ELISA).

RESULTS

In pre-eclampsia/eclampsia, VCAM-1 levels were higher than in normal pregnancy. Serum concentrations of VCAM-1 were significantly higher in severe pre-eclampsia and eclampsia compared to mild pre-eclampsia or healthy controls. ROC analysis detected that VCAM-1 > or = 450 ng/ml had a sensitivity of 0.79 and a specificity of 0.90 in detecting severe pre-eclampsia and eclampsia.

CONCLUSION

This is the first study to correlate VCAM-1 levels with severity of disease in pre-eclampsia. Our findings indicate that increasing levels of soluble VCAM-1 are present in the circulation of patients with severe pre-eclampsia/eclampsia compared to mild pre-eclampsia or healthy pregnant women. Elevated VCAM-1 levels may represent a possible mechanism by which endothelial cells attract leukocytes and cause endothelial cell damage.

Midtrimester urine human chorionic gonadotropin beta-subunit core fragment levels and the subsequent development of pre-eclampsia

OBJECTIVE

Our purpose was to determine whether midtrimester maternal urine human chorionic gonadotropin beta-subunit core fragment predicts later pre-eclampsia.

STUDY DESIGN

Urine beta-core fragment levels standardized to spot creatinine concentration and expressed as multiples of the median were prospectively determined in 347 midtrimester singleton pregnancies undergoing genetic amniocentesis. All women considered in the analysis were white and nonsmokers. Obstetric chart review was undertaken after delivery to identify cases in which pre-eclampsia developed. The risk of pre-eclampsia at different threshold levels of beta-core fragment of human chorionic gonadotropin was determined.

RESULTS

The median maternal age was 36.0 years, with a median gestational age at urine collection of 16.0 weeks. The median level of the beta-core fragment of human chorionic gonadotropin was 1385.5 ng/mg of creatinine in those with pre-eclampsia, whereas that in those without pre-eclampsia was 1061.2 ng/mg. The difference was significant (Mann-Whitney U test, P = .03). A significant linear association was found between the beta-core fragment concentration and the risk of pre-eclampsia (Mantel-Haenszel test of linear association, P = .03). The relative risk and 95% confidence interval of subsequent pre-eclampsia increased from 2.07 (1.06 to 4.05) at beta-core fragment levels of human chorionic gonadotropin > or = 2.0 multiples of the median to 5.17 (1.95 to 13.7) at > or = 4.0 multiples of the median.

CONCLUSION

Clinically normal patients with elevated midtrimester levels of urine beta-core fragment of human chorionic gonadotropin are at increased risk for the subsequent development of pre-eclampsia. The clinical value of this urine analyte as a marker for pre-eclampsia needs to be further investigated.

Oxygen regulates human cytotrophoblast differentiation and invasion: implications for endovascular invasion in normal pregnancy and in pre-eclampsia

This review article focuses on the unique process by which the human placenta normally forms and how changes in this process can lead to serious pregnancy complications such as pre-eclampsia. One way to compare normal and pathologic pregnancies is to examine biopsy specimens of the placenta and placental bed for disease-associated morphological changes in cellular architecture. Our recent work has verified the decades-old observation that pre-eclampsia is associated with abnormally shallow placentation. We also discuss how these morphological observations prompted us to use a combination of in vitro modeling and in situ immunolocalization techniques to gain insights into the molecular bases of normal placentation and how these mechanisms go awry in pre-eclampsia.

Pre-eclampsia: a disorder of placental mitochondria?

Pre-eclampsia is a common, pregnancy-induced, multisystem disease leading to severe complications in the mother and foetus. The aetiology of pre-eclampsia remains a mystery, but a growing body of evidence suggests that a mitochondrial defect might cause the impairement of differentiation and invasion of the trophoblast that leads to this disorder. This hypothesis is the topic of ongoing studies that, if confirmed, would be highly relevant to preventative strategies for this disease.

A role for noradrenaline in pre-eclampsia: towards a unifying hypothesis for the pathophysiology

OBJECTIVE

To compare plasma catecholamine (noradrenaline and adrenaline) levels in pre-eclamptic to normotensive pregnancy, and to study the activity of synthetic enzymes for catecholamines in placental and trophoblastic cell cultures. We postulated that catecholamines might be an important signal secreted by the fetoplacental unit in pre-eclampsia.

METHODS

We recruited 12 women with pre-eclampsia and 12 pregnant women with nonproteinuric hypertension undergoing delivery by caesarean section, 23 normotensive women undergoing elective caesarean section at term, and 26 normotensive primigravid women with ongoing pregnancies at gestations equivalent to those women with pre-eclampsia. We measured venous blood concentrations of catecholamines. Following delivery, we studied tyrosine hydroxylase (the rate limiting enzyme for catecholamine synthesis) activity in placental tissue of these women as well as from four eclamptic women not in the observer study. We used Northern blot analysis to quantify mRNA for tyrosine hydroxylase and dopamine-beta-hydroxylase (D-beta-H, a non-rate-limiting synthetic enzyme for catecholamine) in placental tissue, as well as in trophoblast cells in primary culture and trophoblast cell lines.

RESULTS

Venous blood concentrations of noradrenaline were significantly higher in pre-eclamptic women compared with normotensive women. Tyrosine hydroxylase activity was greater in placental tissue from pre-eclamptic and eclamptic compared with normotensive pregnancies, as were mRNA levels for this enzyme. The mRNA levels for the non-rate-limiting D-beta-H in women with pre-eclampsia were similar to those in normotensive pregnancies. First trimester trophoblast cells in primary culture and trophoblast cell lines transcript mRNA for tyrosine hydroxylase and D-beta-H.

CONCLUSIONS

Trophoblasts have the capacity to secrete catecholamines, and we found increased activity of the rate-limiting synthetic enzyme in placental tissue from pre-eclamptic pregnancies. We postulate that the higher levels of catecholamines we found in the plasma of women with pre-eclampsia might be of placental origin. We hypothesise that in pre-eclampsia ischaemic trophoblast tissue secretes catecholamines as a physiological signal to increase maternal blood flow to the fetoplacental unit, which itself is spared the vasoconstrictor effects of catecholamines (placental vessels are known to be unresponsive to catecholamines). However, since the basic pathology--defective trophoblast invasion--is not corrected, the increased blood flow fails to resolve the ischaemia, and the secretion of catecholamines is therefore sustained or even enhanced. Noradrenaline is known to cause lipolysis. This results in breakdown of triglycerides to free fatty acids, which are oxidized to lipid peroxides. The latter are cytotoxic and cause widespread endothelial cell damage and dysfunction, culminating in the clinical syndrome of pre-eclampsia.

Pathogenesis of preeclampsia: a comprehensive model

The objective of this review was to provide a comprehensive and practical concept on the pathogenesis of preeclampsia on the basis of the currently available scientific evidence. A MEDLINE search was performed of English-language articles published between 1966 and 1997, supplemented with references cited in relevant research articles. Using our data sources, we developed a scheme describing the sequence of events between implantation and the time of manifest clinical disease characterized by generalized endothelial cell dysfunction. A yet unidentified toxic circulating factor released by the ischemic placenta, is held responsible for the impaired endothelial cell function. Particularly, epidemiological studies point to a concept in which immune maladaptation to the fetal allograft plays a key role in causing defective placentation leading to placental ischaemia. The incidence of preeclampsia in sisters and daughters of women who had had preeclampsia is raised. Disease states with vascular involvement, like chronic hypertension and diabetes mellites, are associated with an increased risk for preeclampsia. Recently subclinical abnormalities in hemostasis, metabolism and volume homeostasis have been described in patients with a history of preeclampsia. Placental ischemia secondary to defective placentation, a prerequisite for the development of preeclampsia, has a multifactorial origin consisting of three major components: immune maladaptation, genetic predisposition, and vascular mediated factors. Probably, a summation of these factors will determine whether a pregnant woman is to develop the syndrome. The recently described subclinical abnormalities in hemostasis, metabolism, and vascular function in patients with a history of preeclampsia might give the clinician the opportunity to reduce the recurrence risk by pharmacotherapeutic intervention.

Nitric oxide in preeclampsia: lack of evidence for decreased production

The purpose of our study was to determine the involvement of the L-arginine-NO system in preeclampsia. We studied 26 patients with preeclampsia and 27 normotensive pregnancies. Maternal and cord plasma, urine and amniotic fluid were assayed for nitric oxide metabolites (nitrite and nitrate) using the Griess reaction. Sections of placenta and fetal membranes were immunostained with polyclonal anti-endothelial and anti-neuronal nitric oxide synthase antibodies. The concentration of nitrate in the amniotic fluid of preeclamptic patients (median 10.3 mumol/mg creatinine) was significantly higher (P < 0.001) than in the normotensive group (5.6 mumol/mg creatinine). Nitrate concentrations in maternal and cord plasma and in urine were similar in the two groups. Endothelial cells of the villi of preeclamptic placentas showed a higher positivity in endothelial nitric oxide synthase immunostaining with respect to normotensive controls. Our results indicate that feto-placental NO production is not reduced in preeclampsia. In contrast, the increased concentrations of NO metabolites in amniotic fluid and the positive immunostaining of endothelial nitric oxide synthase in the placental villi suggest that the placental L-arginine-NO system is up-regulated in preeclampsia.

Antiphospholipid antibodies or not? The role of beta 2 glycoprotein 1 in autoantibody-mediated pregnancy loss

Antiphospholipid antibodies are a family of autoantibodies including lupus anticoagulant and anticardiolipin antibodies that appear to react with negatively charged phospholipids. These antibodies induce thrombosis and pregnancy complications including recurrent stillbirth, recurrent miscarriage, pre-eclampsia and intra-uterine growth retardation. Recent evidence indicates that antiphospholipid antibodies do not bind directly to phospholipid but rather to phospholipid-binding proteins or to a combination of phospholipid and phospholipid-binding proteins. This opens the possibility that antiphospholipid antibodies may be pathogenic by disrupting the function of phospholipid-binding proteins rather than membrane phospholipid. The antigenic role of one phospholipid-binding protein, beta 2 glycoprotein, has been studied in the greatest detail and is reviewed. Despite being highly conserved and expressed at high levels, the physiological function of beta 2 glycoprotein 1 remains unknown. However, a number of putative roles have been proposed which allow speculation as to the mechanism by which antiphospholipid antibodies may disrupt haemostasis and pregnancy.

Hypoxia stimulates ecNOS mRNA expression by differentiated human trophoblasts

Cytotrophoblasts isolated from normal human placenta cultured under normoxic conditions (20% O2, pO2 = 130 mmHg) for 48-72 h differentiate to a form which expresses high levels of hCG and which morphologically resembles syncytiotrophoblast. We had previously shown that hypoxia (0-1% O2, pO2 = 12-14 mmHg) blocks this differentiation process, although trophoblasts exposed to hypoxia for up to 96 h were completely viable. In this article we showed that trophoblast responds to hypoxia by expressing the hypoxia-sensitive DNA binding protein HIF-1. We also showed that in trophoblast cultured under normoxic conditions, expression of endothelial cell nitric oxide synthase (ecNOS) mRNA increases with time, reaching a maximum in 48-72 h. However, in trophoblast maintained under hypoxic conditions for 48 h (after an initial 24 h in normoxia), expression of ecNOS mRNA is greatly reduced. These observations are consistent with the expression of ecNOS by syncytiotrophoblast but not by cytotrophoblast. In contrast, exposure of differentiated trophoblasts to hypoxia for 24 h (after 48-72 h in normoxia) significantly stimulates expression of ecNoS mRNA over that of cells maintained continuously in normoxia. These results suggest that in differentiated trophoblast hypoxia can stimulate ecNOS expression.

Angiotensinogen T235 expression is elevated in decidual spiral arteries

Preeclampsia is associated with a common molecular variant of angiotensinogen (Met235Thr). This variant is in tight linkage disequilibrium with a mutation in the angiotensinogen promoter, G(-6)A, which leads to elevated expression in vitro. Since angiotensin II levels could play a role in atherotic changes of the uterine spiral arteries associated with preeclampsia, we investigated angiotensinogen expression in the first trimester uterus. We localized angiotensinogen transcription in uterine decidua using in situ reverse transcription PCR. We then compared decidual T235 expression levels to M235 levels in heterozygous women using an allele-specific ligation assay and a single nucleotide primer extension assay. In human decidua, angiotensinogen is expressed only in spiral artery smooth muscle cells. Heterozygous women have significantly elevated expression of the T235 allele compared to the M235 allele (P < 0.0001). These observations suggest that elevated expression of the T235 allele in decidual spiral arteries may cause first trimester atherotic changes leading to preeclampsia.

Can flow cytometric detection of platelet activation early in pregnancy predict the occurrence of preeclampsia? A prospective study

OBJECTIVES

An increased platelet activation status is present in patients with preeclampsia. Our purpose was (1) to establish by means of flow cytometry whether platelets circulate in an activated state during the first and second trimesters of pregnancy and (2) to establish whether early platelet activation predicts the onset of preeclampsia.

STUDY DESIGN

Consecutively, 244 pregnant women were included in a prospective study design. Platelets in whole blood samples from the pregnant women in the first trimester, the second trimester, and after delivery were labeled with the following antibodies associated with platelet activation: anti-CD62P (P-selectin, alpha-granule secretion), anti-CD63 (GP53, lysosomal secretion), anti-CD31 (GPIIa', platelet endothelial cell adhesion molecule-1). The surface antigen exposure was determined by double-label flow cytometry with anti-CD42b (GPIb, a platelet-specific monoclonal glycoprotein) to select platelets and platelet-derived materials. Preeclampsia was defined as a diastolic blood pressure > or = 90 mm Hg and proteinuria > or = 0.3 gm in a 24-hour urine sample (International Society for Study of Hypertension in Pregnancy criteria).

RESULTS

Seventeen of 244 patients had preeclampsia (6.9%). Only first-trimester CD63 expression had an area under the curve > 0.5 by receiver-operator characteristic curve analysis and was selected as a possible predictor of preeclampsia. We found a sensitivity of 47% and a specificity of 76% with use of a percentage of activated platelets above 2% as a positive test. Likelihood ratios were 1.94 for positive likelihood and 0.69 for negative likelihood. Univariate logistic regression analysis results were odds ratio 2.8 (95% confidence interval 1.0 to 7.6). Multivariate logistic regression analysis results were odds ratio 2.9 (95% confidence interval 0.92 to 8.9). However, the odds ratio of first antenatal diastolic blood pressure was two to four times higher than the odds ratio of first-trimester CD63 expression. The combination of first-trimester CD63 and first antenatal diastolic blood pressure increases the positive likelihood ratio from 1.94 to 9.4, with a sensitivity of 41%, a specificity of 96%, and a negative likelihood ratio of 0.62.

CONCLUSIONS

Increased first-trimester CD63 expression is an independent risk factor for development of preeclampsia. CD63 expression might be useful to identify a subgroup of patients with a high risk for development of preeclampsia, especially in combination with first-trimester antenatal diastolic blood pressure. This method of patient selection may enable more efficient intervention studies in patients at risk than do the selection methods used so far.

Aspirin induces increased expression of both prostaglandin H synthase-1 and prostaglandin H synthase-2 in cultured human placental trophoblast

OBJECTIVE

We tested the hypothesis that aspirin affects trophoblast like other epithelial cells do, by inhibiting prostanoid production, inducing prostaglandin H synthase-2 expression, and enhancing secretion of 15-hydroxyeicosatetraenoic acid.

STUDY DESIGN

Cytotrophoblast from placentas (n = 15) of uncomplicated singleton pregnancies were cultured in medium 199 for 4 to 72 hours in the presence or absence of aspirin.

RESULTS

Aspirin (10(-4) M) inhibited (p < 0.01) average trophoblast prostaglandin E2 release by 60% and thromboxane B2 by 86%. Western immunoblotting showed the prostaglandin H synthase-1 was constitutively expressed in cytotrophoblast, and aspirin treatment caused a twofold increase in prostaglandin H synthase-1 expression. Prostaglandin H synthase-2 was also constitutively expressed in untreated cytotrophoblast but at lower levels than prostaglandin H synthase-1. Aspirin enhanced prostaglandin H synthase-2 expression in trophoblast cultures, but prostaglandin H synthase-2 contributed a range of only 10% to 33% (n = 4) of the total cellular prostaglandin H synthase protein pool even after aspirin induction. The increased prostaglandin H synthase expression depended on both transcription and translation because actinomycin D and cycloheximide each inhibited the increased prostaglandin H synthase protein expression after aspirin treatment. The aspirin induction of prostaglandin H synthase was accompanied by decreased release of 15-hydroxyeicosatetraenoic acid.

CONCLUSIONS

Trophoblast differs from other cells studied because aspirin enhances expression of both prostaglandin H synthase-1 and prostaglandin H synthase-2 isozymes while decreasing, instead of increasing, the secretion of 15-hydroxyeicosatetraenoic acid. The aspirin effects on prostaglandin H synthase synthesis and 15-hydroxyeicosatetraenoic acid release in trophoblast suggest that the mechanisms of action for aspirin in the prophylaxis of preeclampsia may be more diverse than simply altering platelet thromboxane production.

Activin A and inhibin A as possible endocrine markers for pre-eclampsia

BACKGROUND

Inhibin A and activin A are produced by the placenta during human pregnancy. This study aimed to measure circulating concentrations of inhibin A, pro alpha C-containing inhibins, and activin A in the serum of women with pre-eclampsia and of healthy matched control pregnant women, and to establish the molecular-weight forms of circulating inhibin A and activin A in pre-eclampsia.

METHODS

In a retrospective cross-sectional study, blood samples were taken from 20 women in hospital with established pre-eclampsia, and from 20 control pregnant women attending antenatal clinics, who were matched for duration of gestation (pre-eclampsia mean 29.15 [SD 3.75] weeks; controls 29.30 [3.93] weeks), parity, and maternal age. Serum samples were analysed for inhibin A, inhibin B, pro alpha C, and activin A. Pooled samples of control (n = 3) and pre-eclampsia serum (n = 3) subsequently underwent fast protein liquid chromatographic analysis to assess the molecular-weight forms of inhibin A and activin A. Results are expressed as mean and SD for all variables measured.

FINDINGS

Serum concentrations of inhibin A, activin A, and pro alpha C were significantly higher in pre-eclampsia than in control normal pregnancy (inhibin A 3.05 [1.8] vs 0.36 [0.14] ng/mL, p < 0.001; activin A 38.08 [25.88] vs 3.95 [2.32] ng/mL, p < 0.001; pro alpha C-containing inhibins 2.2 [0.81] vs 0.71 [0.33] ng/mL, p < 0.001). Inhibin B concentrations in maternal serum were not increased. Molecular-weight forms of inhibin A (32 kDa) and activin A (> 100 kDa) were similar in pre-eclampsia and normal pregnancy. The mean concentrations of hCG were 59.05 [43.98] and 16.3 [8.72] ng/mL, respectively.

INTERPRETATION

Higher maternal serum concentrations of inhibin A, pro alpha C, and total activin A in pre-eclampsia than in control pregnancies could be helpful in the diagnosis of pre-eclampsia. These changes are interpreted as further evidence for trophoblast dysfunction in pre-eclampsia.

The solid state environment orchestrates embryonic development and tissue remodeling

Cell interactions with extracellular matrix and with other cells play critical roles in morphogenesis during development and in tissue homeostasis and remodeling throughout life. Extracellular matrix is information-rich, not only because it is comprised of multifunctional structural ligands for cell surface adhesion receptors, but also because it contains peptide signaling factors, and proteinases and their inhibitors. The functions of these groups of molecules are extensively interrelated. In this review, three primary cell culture models are described that focus on adhesion receptors and their roles in complex aspects of morphogenesis and remodeling: the regulation of proteinase expression by fibronectin and integrins in synovial fibroblasts; the regulation of osteoblast differentiation and survival by fibronectin, and the regulation of trophoblast differentiation and invasion by integrins, cadherins and immunoglobulin family adhesion receptors.

The effect of nifedipine and methyldopa on maternal cerebral circulation

OBJECTIVE

To study how the treatment of severe gestational hypertension affects maternal middle cerebral artery velocimetry.

DESIGN

Prospective, clinical, descriptive study.

SETTING

John Radcliffe Maternity Hospital, Oxford, England.

PARTICIPANTS

Pregnant and puerperal women who required acute or chronic antihypertensive treatment with nifedipine (n = 46) or methyldopa (n = 26), respectively.

METHODS

Transcranial Doppler ultrasound examinations of maternal middle cerebral arteries were performed before and 45 min after nifedipine; and before and 48 hours after the onset of methyldopa therapy. Blood pressure and heart rate were also recorded.

MAIN OUTCOME MEASURES

Clinical and transcranial Doppler changes induced by the antihypertensive medication.

RESULTS

Blood pressure and middle cerebral artery velocities decreased significantly following both short- and long-acting antihypertensive therapy. Nifedipine-induced changes were more pronounced and uniform than those found after methyldopa (16.7% and 6.4% decrease in middle cerebral artery mean velocity, respectively). The middle cerebral artery mean velocity decrease was independent of changes in the blood pressure or heart rate.

CONCLUSIONS

Maternal cerebral haemodynamics are influenced by antihypertensive treatment. The reduction of middle cerebral artery flow velocities following administration of nifedipine and methyldopa may suggest that cerebral vasodilatation is occurring, which is consistent with the concept that cerebral vasospasm is present in women with pre-eclampsia. The cerebral vasodilatation could result from a direct effect of the medication on the arteries in question.

Human cytotrophoblasts adopt a vascular phenotype as they differentiate. A strategy for successful endovascular invasion?

Establishment of the human placenta requires that fetal cytotrophoblast stem cells in anchoring chorionic villi become invasive. These cytotrophoblasts aggregate into cell columns and invade both the uterine interstitium and vasculature, anchoring the fetus to the mother and establishing blood flow to the placenta. Cytotrophoblasts colonizing spiral arterioles replace maternal endothelium as far as the first third of the myometrium. We show here that differentiating cytotrophoblasts transform their adhesion receptor phenotype so as to resemble the endothelial cells they replace. Cytotrophoblasts in cell columns show reduced E-cadherin staining and express VE-(endothelial) cadherin, platelet-endothelial adhesion molecule-1, vascular endothelial adhesion molecule-1, and alpha-4-integrins. Cytotrophoblasts in the uterine interstitium and maternal vasculature continue to express these receptors, and, like endothelial cells during angiogenesis, also stain for alphaVbeta3. In functional studies, alphaVbeta3 and VE-cadherin enhance, while E-cadherin restrains, cytotrophoblast invasiveness. Cytotrophoblasts expressing alpha4 integrins bound immobilized VCAM-1 in vitro, suggesting that this receptor-pair could mediate cytotrophoblast-endothelium or cytotrophoblast-cytotrophoblast interactions in vivo, during endovascular invasion. In the pregnancy disorder preeclampsia, in which endovascular invasion remains superficial, cytotrophoblasts fail to express most of these endothelial markers (Zhou et al., 1997. J. Clin. Invest. 99:2152-2164.), suggesting that this adhesion phenotype switch is required for successful endovascular invasion and normal placentation.

Human placental syncytiotrophoblast microvillous membranes impair maternal vascular endothelial function

OBJECTIVE

To investigate the hypothesis that, should there be an increase in deported syncytiotrophoblast microvillous membrane fragments in pre-eclampsia, it may cause maternal vascular endothelial dysfunction.

DESIGN

Syncytiotrophoblast microvillous membrane (STBM) vesicles, prepared from normal term placentae, were perfused through small subcutaneous arteries isolated from fat biopsies obtained at caesarean section. Endothelial function of these arteries was studied by determining acetylcholine-induced relaxation after preconstriction with noradrenaline. As controls, physiological buffer or red blood cell membranes in physiological buffer were used and endothelial function similarly estimated. Transmission electron microscopy was performed on arteries after perfusion.

SAMPLE

STBM vesicles, isolated from the placentae of three healthy women undergoing elective caesarean section for reasons unrelated to pre-eclampsia, were suspended in physiological buffer. Subcutaneous fat arteries were obtained from a separate group of 13 normotensive pregnant women, also undergoing elective caesarean section at term.

RESULTS

Perfusion with red blood cell membranes or physiological buffer had no significant effect on the concentration dependent relaxation in arteries preconstricted with noradrenaline. However, after 2 h perfusion with STBM vesicles, arteries showed a significant reduction in relaxation to acetylcholine, indicative of altered endothelial function. Transmission electron microscopy of arteries perfused with STBM vesicles confirmed endothelial disruption.

CONCLUSIONS

STBM vesicle perfusion specifically altered the relaxation response of preconstricted maternal subcutaneous fat arteries to acetylcholine, suggesting an alteration in endothelial dependent relaxation. Deported microvilli may therefore be capable of producing endothelial cell damage and endothelial dysfunction observed in the maternal syndrome of pre-eclampsia.

Increased maternal plasma levels of soluble adhesion molecules (ICAM-1, VCAM-1, E-selectin) in preeclampsia

The physiological significance of soluble adhesion molecules has not been elucidated but it has been reported that a number of cytokines may increase the cleavage of soluble adhesion molecules. The fact that preeclampsia is associated with both increased cytokine concentrations and endothelial cell damage led us to analyse levels of soluble adhesion molecules in preeclamptic women and to compare these levels to the disease state. Since the cytokine network is altered by reproduction, the present study also raised the question as to whether levels of soluble adhesion molecules differ between pregnant and non-pregnant women, and whether variations occur with relation to gestational age or delivery. Levels of soluble adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin) in 25 preeclamptic women were compared to those in healthy pregnant women matched for age, parity and gestation, and the levels of soluble adhesion molecules of 40 healthy pregnant women at different gestational ages were determined and compared to those of 15 non-pregnant women. Concentrations were measured by ELISAs. Levels of ICAM-1, VCAM-1 and E-selectin concentrations were elevated in preeclamptic pregnancies, whereas serum levels in normal pregnancy did not differ from those of non-pregnant women. No changes were observed in relation to gestational age or delivery.

Comparison of selenium levels in pre-eclamptic and normal pregnancies

Abnormal placentation is the likely cause of the slow fetal growth and the high levels of circulating lipid peroxides found in severe pre-eclampsia. These peroxides are probably responsible for the high thromboxane:prostacyclin ratio found in this disease and may participate in the endothelial cell damage which is its most notable feature. Selenium (Se), because of its role in glutathione peroxidase, is suggested to be an important component of the removal system for these damaging peroxides. Serum-Se concentrations have therefore been measured in 19 pairs of pre-eclamptic women and matched controls. Infant birth-weights were recorded. No significant difference was found in the concentrations of Se in pre-eclamptic and control groups. Serum Se was found to be low in both groups. Birthweights were significantly lower in the pre-eclamptic group. The interpretation of serum-Se measurements from the third trimester of a pre-eclamptic pregnancy is complicated by the reduced fetal growth and probable lower Se take-up by the fetus in such a pregnancy. The merits of alternative measurements, such as total intravascular Se, placental Se, or samples from an earlier stage of gestation, are discussed. The importance of factors other than Se to the activity of glutathione peroxidase, and of other antioxidants to pre-eclamptic, is stressed.

Systemic and fetal-maternal nitric oxide synthesis in normal pregnancy and pre-eclampsia

OBJECTIVE

To investigate systemic and fetal-placental nitric oxide synthesis by biochemical and molecular biology means in normal human pregnancy and pre-eclampsia.

DESIGN AND PARTICIPANTS

Three groups of women were studied: healthy pregnant women (n = 8), pregnant women with pre-eclampsia (n = 8), and age-matched nonpregnant controls (n = 8). Pre-eclamptic patients were treated with nifedipine (30-60 mg/day) for severe hypertension. Systemic nitric oxide synthesis was assessed in normal pregnant women at weeks 18-21, 29-32 and 38-39 and in pre-eclamptic women on admission to the hospital (29-32 weeks, 30 on average), before the morning nifedipine administration. Nonpregnant women were studied twice at four-week intervals as controls. The pattern of nitric oxide biosynthesis in fetal-placental circulation was studied in normal and pre-eclamptic women at the delivery.

SETTING

Mario Negri Institute for Pharmacological Research, Bergamo, and the Division of Obstetrics and Gynaecology of the University of Brescia.

MAIN OUTCOME MEASURES

Plasma cGMP levels and platelet nitric oxide synthesis, assessed by measuring the conversion of [3H]L-arginine to [3H]L-citrulline as well as intracellular cGMP, were evaluated. Constitutive nitric oxide synthase (EC-NOS) gene expression by Northern blot analysis and nitric oxide release by the conversion of [3H]L-arginine to [3H]L-citrulline were assessed in umbilical vein endothelial cells (HUVEC) and in placenta. Inducible nitric oxide synthase activity was also evaluated in HUVEC exposed to tumour necrosis factor alpha (TNF alpha) and in placenta homogenates incubated in calcium free medium.

RESULTS

Plasma cGMP was higher in both normal pregnant and pre-eclamptic women than in nonpregnant controls. In normal pregnancy cGMP rose as early as 18-21 weeks and remained elevated throughout pregnancy. [3H]L-citrulline production and intracellular cGMP were comparable in platelets from all women. EC-NOS gene expression and nitric oxide synthesis were identical in HUVEC and placenta from normal pregnant and pre-eclamptic women.

CONCLUSIONS

Systemic levels of CGMP, the nitric oxide second messenger, are increased in normal pregnancy. Excessive nitric oxide production does not derive from platelets. Pre-eclampsia is not associated with changes in fetal-placental nitric oxide synthesis.

The effect of hypoxia on term trophoblast: hormone synthesis and release

Isolated trophoblast in culture remained viable when exposed to severe hypoxia (Po2 12-14 mmHg) for at least 72 h as indicated by trypan blue exclusion and the synthesis and secretion of metabolically labelled proteins. However, release of hCG, hPL, progesterone and estradiol was reduced to < 10 per cent when compared to trophoblast in normoxia (Po2 120-130 mmHg). hCG mRNA was also reduced demonstrating interruption of synthesis at transcription. Acute exposure to hypoxia (2 h) suppressed progesterone release but not hCG, whereas inhibitors of oxidative phosphorylation suppressed hCG release but not progesterone. hCG release increases progressively during culture in normoxia, peaking at 72 h. Exposure of trophoblast to hypoxia for 48 h after 24, 48 and 72 h in normoxia interrupted this progression but did not suppress hCG release. Progesterone release, in contrast, was reduced by hypoxia. Exogenous dibutyryl cAMP increased hCG and progesterone release by normoxic trophoblast but not by hypoxic cells. Trophoblast returned to normoxia after 24 h in hypoxia increased hCG and progesterone release, suggesting early recovery. Conservation of oxygen and ATP by reducing hormone synthesis may contribute to survival of trophoblast in hypoxia.

Partial characterization of an immortalized human trophoblast cell-line, TCL-1, which possesses a CSF-1 autocrine loop

Many previous studies in both mouse and human placenta have implicated a role for colony stimulating factor-1 (CSF-1) in the regulation of placental development. In this study we have examined CSF-1 production by an immortalized cell line (TCL-1) derived from the choriodecidua, transfected with a retrovirus gene coding for the large-T antigen. TCL-1 cells were uniformly positive by immunocytochemistry for the composite sub-units of human chorionic g gonadotrophin (hCG) but were negative for markers of other cell types localized at the fetal-maternal interface. Gelatinase enzymes were secreted by TCL-1 cells cultured on extracellular matrix in a manner indicative of extra-villous trophoblast. Dot-blot immunoassays and ELISA indicated that CSF-1 was secreted by TCL-1 cells, at levels comparable to primary trophoblast cells and BeWo choriocarcinoma (trophoblast tumour) cells. Reverse transcriptase-polymerase chain reaction analysis confirmed the presence in TCL-1 cells of CSF-1 receptor mRNA (c-fms gene product), indicating that the components of a potential autocrine loop were present in these cells. Proliferation of TCL-1 cells was not affected by the addition of exogenous CSF-1 but was elevated in response to treatment with a CSF-1 neutralizing antibody. The immortalized cell line, TCL-1, provides a potential model in which to investigate regulation of growth and differentiation of trophoblast cells in vitro.

Alterations of intrauterine eicosanoid production in pregnancy-induced hypertension: decreased production of 12-hydroxyeicosatetraenoic acid in the placenta

The important role of eicosanoids in pregnancy-induced hypertension is generally accepted. Because of the lack of innervation of the uteroplacental vessels, humoral vasoactive factors are important for the regulation of vascular tone. Until now, mainly the balance of vasodilatative and vasoconstrictive prostaglandins has been studied. We were able to confirm their intrauterine imbalance in hypertensive pregnancies. In addition, the placental production of less known lipoxygenase metabolites has been analyzed in this study. Intrauterine tissues (30-100mg wet weight) were examined for their release of eicosanoids. Short term tissue cultures were performed in Hanks balanced salts solution (HBSS) at 37 degrees C in an atmosphere of 95% air/5% CO2 with and without incorporation of tritiated arachidonic acid. The arachidonate metabolites in culture media were analyzed by High Performance Liquid Chromatography (HPLC) with radioactivity detection or by enzyme immunoassays or radioimmunoassays, respectively. All intrauterine tissues released more lipoxygenase metabolites than cyclooxygenase metabolites with 12-hydroxy-eicosatetraenic acid (12-HETE) as their main metabolite. The placental release of 12-HETE was significantly decreased in hypertensive pregnancies. In hypertensive pregnancies the ratio TXB2/6-keto-PGF1 alpha synthesis was increased. Lipoxygenase metabolites, especially 12-HETE, seem to have important physiological and pathophysiological functions in the intrauterine compartment. Their biological role in this context needs further investigation.

Endothelial cell proliferation is suppressed by plasma but not serum from women with preeclampsia

OBJECTIVES

Evidence has been sought for a circulating factor derived from the placenta that suppresses endothelial cell proliferation and hence contributes to the maternal endothelial cell disturbances of preeclampsia.

STUDY DESIGN

The effects of sera and plasmas from women with proteinuric preeclampsia and from matched normal pregnant control women on endothelial cell proliferation were compared. The recovery of endothelial cell inhibitory activity from syncytiotrophoblast microvesicles added to male blood and prepared as plasma or serum was determined to investigate the possible placental origin of the inhibitory factor.

RESULTS

Sera from women with preeclampsia did not inhibit endothelial cell proliferation. In contrast, plasma from preeclamptic women significantly suppressed endothelial cell growth at 20% dilution compared with controls, and suppression was more pronounced in severe preeclampsia. The inhibitory activity of syncytiotrophoblast microvesicles added to blood could not be recovered from serum, only from plasma, which may explain why there was no suppression with sera from preeclamptic women.

CONCLUSIONS

These results confirm that there is a blood-borne endothelial cell suppressive factor in preeclampsia that may be derived from the placenta.

Hypoxia alters early gestation human cytotrophoblast differentiation/invasion in vitro and models the placental defects that occur in preeclampsia

During normal human pregnancy a subpopulation of fetal cytotrophoblast stem cells differentiate and invade the uterus and its arterioles. In the pregnancy disease preeclampsia, cytotrophoblast differentiation is abnormal and invasion is shallow. Thus, the placenta is relatively hypoxic. We investigated whether lowering oxygen tension affects cytotrophoblast differentiation and invasion. Previously we showed that when early gestation cytotrophoblast stem cells are cultured under standard conditions (20% O2) they differentiate/invade, replicating many aspects of the in vivo process. Specifically, the cells proliferate at a low rate and rapidly invade extracellular matrix (ECM) substrates, a phenomenon that requires switching their repertoire of integrin cell-ECM receptors, which are stage-specific antigens that mark specific transitions in the differentiation process. In this study we found that lowering oxygen tension to 2% did not change many of the cells' basic processes. However, there was a marked increase in their incorporation of [3H]thymidine and 5-bromo-2'-deoxyuridine (BrdU). Moreover, they failed to invade ECM substrates, due at least in part to their inability to completely switch their integrin repertoire. These changes mimic many of the alterations in cytotrophoblast differentiation/invasion that occur in preeclampsia, suggesting that oxygen tension plays an important role in regulating these processes in vivo.

ECPPA: randomised trial of low dose aspirin for the prevention of maternal and fetal complications in high risk pregnant women. ECPPA (Estudo Colaborativo para Prevenção da Pré-eclampsia com Aspirina) Collaborative Group

OBJECTIVE

To determine the effectiveness of low dose aspirin in women at high risk of adverse outcomes associated with pre-eclampsia.

DESIGN

A collaborative randomised trial comparing the effects of low dose aspirin (60 mg) with placebo on pre-eclampsia and other materno-fetal complications associated with hypertension.

SETTING

Twelve teaching maternity hospitals and 182 obstetricians' offices in Brazil.

SUBJECTS

One thousand and nine women considered to be at high risk for the development of pre-eclampsia, or its complications, entered the study between 12 and 32 weeks of gestation. They were randomly allocated to receive aspirin (498 women) or placebo (511 women) until delivery, and follow up was obtained for 96%.

RESULTS

There were no significant differences between the treatment groups in the incidence of proteinuric pre-eclampsia (6.7% aspirin-allocated compared with 6.0% placebo-allocated women), of preterm delivery (22.3% compared with 26.1%), of intrauterine growth retardation (8.5% compared with 10.1%), or of stillbirth and neonatal death (7.3% compared with 6.0%), nor were there significant differences in the incidence of proteinuric pre-eclampsia in any subgroup of women studied, including those who had systolic blood pressures of 120 mmHg or above at entry (8.5% compared with 7.3%) or those who were chronically hypertensive (10.0% compared with 7.1%). Aspirin was not associated with a significant excess of maternal or fetal bleeding.

CONCLUSION

The results of this study do not support the routine prophylactic administration of low dose aspirin in pregnancy to any category of high risk women (even those who have chronic hypertension or who are considered to be especially liable to early onset pre-eclampsia).

Maternal and perinatal outcome of temporizing management in 254 consecutive patients with severe pre-eclampsia remote from term

OBJECTIVE

To assess maternal and perinatal outcomes of expectant management with plasma volume expansion and pharmacologic vasodilatation in patients with severe pre-eclampsia remote from term.

STUDY DESIGN

All women with severe pre-eclampsia between 20 and 32 weeks' gestation, not in labor and with a live, single fetus admitted to the University Hospital Rotterdam from 1985 to 1993 were managed with the intention to prolong gestation. Treatment consisted of correction of the maternal circulation with vasodilatation by means of dihydralazine and plasma volume expansion under central hemodynamic monitoring. Primary end-points of the study were prolongation of gestation, maternal antepartum and postpartum complications, and fetal and neonatal outcome.

RESULTS

Two-hundred fifty-four patients were included. The median prolongation of pregnancy was 14 (range 0-62) days. Hemodynamic treatment was associated with marked objective and subjective improvement in maternal condition. Complications of central hemodynamic monitoring were not observed. Perinatal mortality was 20.5%.

CONCLUSION

Expectant management with plasma volume expansion and pharmacologic vasodilatation under central hemodynamic monitoring of the maternal circulation may delay delivery and enhance fetal maturity and does not appear to be associated with an increased risk of maternal morbidity and mortality.