Platelet activation and vascular damage in gestational hypertension

Exploring the role of exosomal MicroRNAs as potential biomarkers in preeclampsia

The complex pathogenesis of preeclampsia (PE), a significant contributor to maternal and neonatal mortality globally, is poorly understood despite substantial research. This review explores the involvement of exosomal microRNAs (exomiRs) in PE, focusing on their impact on the protein kinase B (AKT)/hypoxia-inducible factor 1-α (HIF1α)/vascular endothelial growth factor (VEGF) signaling pathway as well as endothelial cell proliferation and migration. Specifically, this article amalgamates existing evidence to reveal the pivotal role of exomiRs in regulating mesenchymal stem cell and trophoblast function, placental angiogenesis, the renin-angiotensin system, and nitric oxide production, which may contribute to PE etiology. This review emphasizes the limited knowledge regarding the role of exomiRs in PE while underscoring the potential of exomiRs as non-invasive biomarkers for PE diagnosis, prediction, and treatment. Further, it provides valuable insights into the mechanisms of PE, highlighting exomiRs as key players with clinical implications, warranting further exploration to enhance the current understanding and the development of novel therapeutic interventions.

Predictive values of combined platelet count, neutrophil-lymphocyte ratio, and platelet-lymphocyte ratio in preeclampsia

We aimed to determine predictive values of the platelet count (PC), Neutrophil lymphocyte ratio (NLR), and platelet lymphocyte ratio (PLR) in preeclampsia independently and in combination. One hundred and eighty pregnant women (96 normal pregnancies, 84 preeclampsia) were included in this study. ROC evaluated the predictive value of PC, NLR, and PLR. AUC, Youden's index, and optimal cut-off thresholds were calculated independently and in combination. The PC significantly decreased in preeclampsia (p < .0001, 95% CI -60.6437 to -24.5963) with cut-off level ≤250.3, whereas NLR was significantly increased in preeclampsia (5.28 ± 4.77, p = .0001, 95% CI 0.9813-2.9187) with cut-off level >4.47. In preeclampsia, PLR significantly decreased (94.32 ± 30.81, p = .0001, 95% CI 58.2583 to -29.6817) with cut-off level ≤100.48. Combined indices of PC, NLR, and PLR were significantly more predictive of preeclampsia when compared to independent indices (AUC 0.86, p < .001, 95% CI 0.801-0.907, sensitivity 75.0, and specificity 81.2) compared to independent indices.IMPACT STATEMENTWhat is already known on this subject? Many studies have tried to find out a simple screening test that would predict the risk of developing preeclampsia. Platelet count, Neutrophil lymphocyte ratio, and platelet lymphocyte ratio have been investigated independently to predict preeclampsia. These parameters are simple, cheap, and are usually available for all patients. Unfortunately, there are no universal cut-off levels accepted.What do the results of this study add? The use of a combination of platelet count, neutrophil-lymphocyte ratio, and platelet lymphocyte ratio is a simple and effective test to predict preeclampsia. The use of a scoring system involving cut-off levels of platelet count, neutrophil-lymphocyte ratio, and platelet lymphocyte ratio is a highly predictive index for developing preeclampsia.What are the implications of these findings for clinical practice and/or further research? In this study, we aimed to highlight the importance of using a combination of platelet count, neutrophil-lymphocyte ratio, and platelet lymphocyte ratio as a scoring index instead of using these parameters independently. More studies are needed to reach a universal cut-off level for each parameter.

Pathophysiology of Preeclampsia: The Role of Exosomes

The pathogenesis of preeclampsia begins when a fertilized egg infiltrates the decidua, resulting in implantation failure (e.g., due to extravillous trophoblast infiltration disturbance and abnormal spiral artery remodeling). Thereafter, large amounts of serum factors (e.g., soluble fms-like tyrosine kinase 1 and soluble endoglin) are released into the blood from the hypoplastic placenta, and preeclampsia characterized by multiorgan disorder caused by vascular disorders develops. Successful implantation and placentation require immune tolerance to the fertilized egg as a semi-allograft and the stimulation of extravillous trophoblast infiltration. Recently, exosomes with diameters of 50-100 nm have been recognized to be involved in cell-cell communication. Exosomes affect cell functions in autocrine and paracrine manners via their encapsulating microRNA/DNA and membrane-bound proteins. The microRNA profiles of blood exosomes have been demonstrated to be useful for the evaluation of preeclampsia pathophysiology and prediction of the disease. In addition, exosomes derived from mesenchymal stem cells have been found to have cancer-suppressing effects. These exosomes may repair the pathophysiology of preeclampsia through the suppression of extravillous trophoblast apoptosis and promotion of these cells' invasive ability. Exosomes secreted by various cells have received much recent attention and may be involved in the maintenance of pregnancy and pathogenesis of preeclampsia.

Evaluating platelet activation related to the degradation products of biomaterials using molecular markers

Increasing numbers of biodegradable medical devices may be used in the circulatory system. The effects of the released degradation products from these medical devices on the blood may be gradual and cumulative. When they reach critical levels, they may cause thrombosis and other complications. For this reason, it is important to evaluate the blood compatibility of degradation products for quality control and development of these devices. In the present study, we evaluated the degradation products of four biodegradable materials (collagen, polylactic acid, calcium phosphate ceramics, and magnesium) using platelet activation molecular markers that are associated with thrombosis. We found that the degradation products activate platelets to a certain extent, and that the degradation products produced during various degradation time periods activate platelets to varying degrees. This platelet activation occurs via several mechanisms, most of which are associated with the physicochemical properties of the degradation products, including ion concentration, pH, molecular microstructure, and molecular weight. Our findings not only provide a clearer understanding of the effects of degradation products from blood-contacting biodegradable devices, but also provide material for screening of degradation behavior so as to improve quality control for these devices.

Study of platelet indices in pregnancy-induced hypertension

Background

Hypertension encountered during pregnancy could be the first sign of a preexisting pathology that can significantly attribute to unfavorable maternal, fetal, and neonatal outcomes. Resolving hypertensive disorders at an early age may not alter the course and proficiency of the disease, but timely detection and treatment can not only prevent hypertensive crisis but also alter unfavorable fetal outcomes. Ipso facto, an early cataloging plays an essential role in predicting the outcome of pregnancy, both for mother and baby. Platelet indices correlate with functional status of platelets and are an emerging risk marker for detecting an impending adverse outcome in pregnancy-induced hypertension (PIH). The aim of this study was to analyze the consociation between platelet indices and severity of PIH.

Methods

A prospective hospital-based study was undertaken on 100 cases diagnosed with PIH (preeclampsia [PE; 88 cases] and eclampsia [12 cases and 100 controls]).

Results

Most cases occurred in the age group of 22-26 years (43.3%) and in primigravidae (55.8%). Analysis of platelet volume indices (PVI) indicated mean platelet volume (MPV), platelet distribution width (PDW), and platelet-large cell ratio (P-LCR) as significant risk factors for developing hypertensive crisis. This was in concordance with the elevated blood pressures.

Conclusion

The study concludes that platelet indices are raised in patients who have PIH as compared with normal pregnancies.

Maternal cardiac function at 35-37 weeks' gestation: prediction of pre-eclampsia and gestational hypertension

OBJECTIVE

To investigate the potential value of combining maternal factors with multiples of the normal median values of maternal cardiovascular parameters at 35-37 weeks' gestation in the prediction of pre-eclampsia (PE) and gestational hypertension (GH).

METHODS

In 2764 singleton pregnancies maternal characteristics and medical history were recorded; uterine artery pulsatility index (UtA-PI), mean arterial pressure (MAP) and maternal cardiovascular parameters were measured. Multivariable logistic regression analysis was then used to determine if the maternal factors and maternal cardiovascular parameters made a significant contribution to predicting PE and GH. The performance of screening was determined by the area under receiver-operating characteristics curves.

RESULTS

In pregnancies that subsequently delivered with PE or GH, total peripheral resistance and MAP were higher and maternal cardiac output was lower, mainly owing to a decrease in heart rate in PE and a decrease in stroke volume in GH. The increases in total peripheral resistance and MAP were inversely related to gestational age at delivery. The performance of screening for PE and GH achieved by maternal characteristics and medical history was improved by the inclusion of MAP, but not by UtA-PI or maternal cardiovascular parameters.

CONCLUSIONS

In women developing term PE total peripheral resistance and MAP are increased and maternal cardiac output is reduced. However, assessment of maternal cardiac function at 35-37 weeks' gestation is unlikely to improve the performance of screening for PE provided by maternal factors and MAP alone. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

The Influence of Labor and Placental Separation on Hemostasis in Term Pregnancy

We studied the hemostatic effects in 68 term preg nant subjects with normal pregnancy (n = 39), gestational diabetes mellitus (n = 21), pregnancy-induced hypertension (n = 8), during labor, after placental separation, and at 24 hours postpartum. During labor, a hypercoagulable state with en hanced fibrinolysis and platelet activation along with elevated plasminogen activator inhibitor-1 and plasminogen activator inhibitor-2 were seen. In all cases following placental separa tion, enhanced fibrinolysis persisted with further elevated tissue plasminogen activator antigen and D-dimer levels, increased thrombin generation and platelet activation with decreasing plasminogen activator inhibitor-1 levels. By 24 hours postpar tum, thrombin generation (thrombin-antithrombin complex) decreased to a nonpregnant level except for pregnancy induced hypertension, but enhanced prothrombin activation (F1+2) was evident in normal, gestational diabetes mellitus and pregnancy- induced hypertension. Reduced total protein S and antithrom bin III activity with normal protein C and elevated fibrinogen levels seen during labor were not affected by delivery. How ever, although factor VII showed a decreasing trend at 24 hours postpartum it remained elevated above the normal nonpregnant level. At 24 hours postpartum, a hypercoagulable state still persisted in normal, gestational diabetes mellitus and preg nancy-induced hypertension term pregnancy accompanied by enhanced fibrinolysis and elevated plasminogen substrate for fibrinolysis, suggesting a critical dynamic equilibrium between a thrombotic and hemorrhagic state.

Evidence of maternal platelet activation, excessive thrombin generation, and high amniotic fluid tissue factor immunoreactivity and functional activity in patients with fetal death

OBJECTIVE

Fetal death can lead to disseminated intravascular coagulation or fetal death syndrome. However, currently it is not clear what are the changes in the coagulation system in patients with a fetal death without the fetal death syndrome. This study was undertaken to determine: (1) whether fetal death in the absence of fetal death syndrome is associated with changes in hemostatic markers in maternal plasma and amniotic fluid; and (2) whether maternal hypertension or placental abruption are associated with further changes in the hemostatic profile of these patients.

METHODS

A cross-sectional study included the following: (1) determination of changes in markers of coagulation and platelet activation in patients with a normal pregnancy (n = 71) and patients with fetal demise (FD) without disseminated intravascular coagulation (n = 65); (2) determination of the amniotic fluid (AF)-tissue factor concentration and activity, as well as the concentrations of thrombin-antithrombin III (TAT) complexes in patients with a normal pregnancy (n = 25) and those with a FD (n = 36) who underwent amniocentesis. Plasma and AF concentrations of TAT complexes and TF (an index of thrombin generation), as well as maternal plasma concentrations of sCD40L (a marker of platelet activation), tissue factor pathway inhibitor (TFPI) and prothrombin fragments (PF) 1 + 2 (also an indicator of in vivo thrombin generation) were measured by ELISA. TF and TFPI activity were measured using chromogenic assays.

RESULTS

(1) patients with FD without hypertension had a higher median maternal plasma sCD40L concentration than normal pregnant women (P < 0.001); (2) patients with FD had a higher median maternal plasma TAT III complexes than women with a normal pregnancy (P < 0.001); (3) the median AF-TF concentration and activity were higher in the FD group than in the normal pregnancy group (P < 0.001 for both); (4) patients with preeclampsia and FD had a higher median maternal plasma immunoreactive TF concentration than both normotensive patients with FD and women with normal pregnancies (P < 0.001 and P = 0.001, respectively); (5) the median plasma TF activity was higher in patients with preeclampsia and FD than that of women with normal pregnancies (P = 0.003); (6) among patients with a FD, those with placental abruption had a higher median AF-TAT complexes concentration than those without abruption (P = 0.0004).

CONCLUSIONS

Our findings indicate that: (1) mothers with a FD have evidence of increased in vivo thrombin generation and platelet activation than women with normal pregnancies; (2) patients with a FD and hypertension had a higher degree of TF activation than those with fetal death but without hypertension; (3) the AF of women with a FD had a higher median TF concentration and activity than that of normal pregnant women. AF can be a potential source for tissue factor and it participates in the development of fetal death syndrome in patients with a retained dead fetus.

Preeclampsia: a renal perspective

Preeclampsia is a syndrome that affects 5% of all pregnancies, producing substantial maternal and perinatal morbidity and mortality. The aim of this review is to summarize our current understanding of the pathogenesis of preeclampsia with special emphasis on the recent discovery that circulating anti-angiogenic proteins of placental origin may play an important role in the pathogenesis of proteinuria and hypertension of preeclampsia.

Hypertensive Disorders of Pregnancy

Hypertensive disorders occur in 6% to 8% of all pregnancies, are the second leading cause of maternal death, and contribute to significant neonatal morbidity and mortality. This is a problem not only in inpatient settings, as ambulatory and home-care nurses are increasingly being called upon to monitor women who are at high risk and may have hypertensive disorders. To prevent hypertension-induced problems in pregnant women, nurses must have strong assessment, advocacy, and counseling skills. Nurses also must provide care based on the latest national standards as described in this article.

Elevated levels of adhesion molecules derived from leukocytes and endothelial cells in patients with pregnancy-induced hypertension

OBJECTIVE

Our purpose was to elucidate the role of adhesion molecules in the pathogenesis of pregnancy-induced hypertension (PIH).

METHODS

Sera, peripheral lymphocytes, and polymorphonuclear cells (PMN) from PIH patients, normal pregnant women, and nonpregnant women were collected. Soluble intercellular adhesion molecule-1 (sICAM-1) in sera was measured by ELISA. ICAM-1 expression on endothelial cells (EC) incubated with sera was analyzed by flow cytometry and RT-PCR. CD11a, CD11b, and CD18 expression on lymphocytes and PMN were also measured by flow cytometory.

RESULTS

CD11a and CD18 expression levels on PMN and lymphocytes of PIH patients were significantly higher than those of normal pregnant women (p<0.05). The expression of CD11b was significantly increased in normal pregnancy compared with that in nonpregnant women (p<0.05). Serum sICAM-1 in PIH patients was higher than that in normal pregnant women (p<0.05). ICAM-1 expression level on EC incubated with PIH serum for 24 hr was significantly higher than that with normal pregnant serum (p<0.0005). ICAM-1 mRNA expression after 12-hr incubation with PIH serum was also significantly increased compared with serum from normal pregnant women (p<0.05).

CONCLUSION

Adhesion molecules may play an important role in the pathogenesis of PIH.

Pathophysiology of preeclampsia and the role of serotonin

Hypertensive disorders constitute the most common medical complications of pregnancy. In normal pregnancy, impressive physiological changes take place in the maternal cardiovascular system. Morphological changes are the result of invasion of migratory trophoblast cells into the walls of the spiral arteries. After destruction of elastic, muscular and neural tissue in the media, the trophoblast cells get incorporated into the vessel wall and the endothelial lining of the spiral arteries is restored. The physiological changes create a low-resistance, low-pressure, high-flow system with the absence of maternal vasomotor control. Biochemical adaptations in maternal vasculature include changes in the prostaglandin system, the renin-angiotensin-aldosteron system and the kallikrein-kinin system. In preeclampsia, physiological changes in the spiral arteries are confined to the decidual portion of the arteries. Myometrial segments remain anatomically intact and fail to dilate. In addition, the adrenergic nerve supply is left intact. The cause of this impaired endovascular trophoblast invasion is not yet elucidated. But in combination with the imbalance between vasodilator and vasoconstrictor eicosanoids, it gives rise to reduced perfusion of the intervillous space. In the absence of an adequate production of antiaggregatory prostacyclin (PGI(2)), nitric oxide, or both, surface-mediated platelet activation is supposed to occur on the surface of the spiral arteries. Because platelets are the principal source of circulating serotonin, the increased platelet aggregation in preeclampsia causes an increase in serotonin levels. Interaction of serotonin with serotonin(1)- or serotonin(2)-receptors depends on the state of the endovascular trophoblast or endothelium in the spiral arteries and has opposite effects with regard to vasodilating and vasoconstrictive influences.

Platelet responsiveness to L-arginine in hypertensive disorders of pregnancy

OBJECTIVE

In chronically hypertensive (CH), preeclamptic (PE), and normotensive pregnant women (N), we investigated ex vivo platelet aggregation in response to L-arginine (L-Arg) and sodium nitroprusside (SN), which are respectively the substrate and donor of nitric oxide (NO).

METHODS

Platelet aggregation was determined with a dual-channel aggregometer by measuring transmittance of light through the sample in comparison to platelet poor plasma, as a reference. Aggregation induced by adenosine diphosphate was continuously recorded for 3 min and measured before and after preincubation with L-Arg and SN.

RESULTS

Preincubation with L-Arg significantly reduced platelet aggregation in N and CH patients (p < 0.05) but not in PE women. Preincubation with SN affected aggregation in PE women also (p < 0.001). No correlation was found between platelet response to L-Arg or SN stimuli and the severity of hypertensive disorders expressed as week of gestation at delivery or birth weight.

CONCLUSIONS

The present study demonstrates that a decreased platelet sensitivity to L-Arg characterizes PE women, whereas SN maintains its antithrombotic power. This impairment seems to be specific for PE, because platelets of CH patients utilize L-Arg normally. This finding supports the involvement of the L-Arg-NO pathway in the pathogenesis of the procoagulative features of PE and probably in the onset of the disease. The maintained response to SN in PE patients suggests a possible therapeutical use of NO donors in the disease.

Nitric oxide activity in the peripheral vasculature during normotensive and preeclamptic pregnancy

We investigated the role of nitric oxide (NO) in the vascular resistance changes of normotensive and preeclamptic pregnancy. Forearm blood flow (FBF) responses to brachial artery infusion of N(G)-monomethyl-L-arginine (L-NMMA), an NO synthase inhibitor, and angiotensin II (ANG II), an NO-independent vasoconstrictor, were determined by plethysmography in 20 nonpregnant women, 20 normotensive primigravidae, and 15 primigravidae with untreated preeclampsia. In pregnant subjects, FBF was reduced to nonpregnancy levels by infusion of norepinephrine (NE), which was then coinfused with ANG II (2, 4, and 8 ng/min) and L-NMMA (200, 400, and 800 microgram/min) each for 5 min. In separate studies, responses to NE (20, 50, and 100 ng/min) were determined in 8 nonpregnant women, with FBF elevated to pregnancy levels by concomitant infusion of glyceryl trinitrate, and 10 pregnant women. Vasoconstrictor responses to L-NMMA were increased in pregnant compared with nonpregnant subjects [mean +/- SE summary measure (in arbitrary units): 60 +/- 7 vs. 89 +/- 8, respectively; P < 0.01], whereas responses to ANG II were blunted (125 +/- 11 vs. 79 +/- 7, respectively; P < 0.001). Compared with normotensive pregnant subjects, preeclamptic subjects had an enhanced response to ANG II (79 +/- 7 vs. 103 +/- 8, respectively; P < 0.05) but no difference in response to L-NMMA (89 +/- 8 vs. 73 +/- 10, respectively; P = 0.30). Responses to NE were similar in pregnant and nonpregnant subjects (110 +/- 20 vs. 95 +/- 33, respectively; P = 0.66). During the third trimester of pregnancy, forearm constrictor responses to L-NMMA are increased. The responses to NE are unchanged, whereas responses to ANG II are blunted. Increased NO activity contributes to the fall in peripheral resistance. In preeclampsia, forearm constrictor responses to ANG II but not L-NMMA are increased compared with those in normal pregnancy. Changes in vascular NO activity are unlikely to account for the increased vascular tone in this condition.

Anesthetic management of preeclampsia/eclampsia

Preeclampsia/eclampsia affects only a small proportion of all pregnancies, yet accounts for much of the obstetric morbidity and mortality seen in the USA and UK. A full understanding of preeclampsia/eclampsia, its variable presentation and complex pathophysiology allows the consulting anesthesiologist to optimize a plan for anesthetic management of the afflicted patient.

Class II major histocompatibility complex typing across the ethnic barrier in pemphigoid gestationis. A study in Mexicans

BACKGROUND

Pemphigoid gestationis (PG), also called herpes gestationis, is a rare autoimmune disease of pregnancy or puerperium (estimated 1 out of 50,000 pregnancies among Caucasians). A previous series has demonstrated an association of PG with human leukocyte antigen (HLA)-DR3 or HLA-DR4 haplotypes. While these haplotypes are most commonly found in individuals of European ancestry, they have also been found in African-American patients affected with PG. PG has rarely been reported in other ethnic groups, and the HLA association in non-Europeans has not been examined.

METHODS

We have characterized eight patients of Mexican ancestry who have PG by clinical, histologic, and immunofluorescence criteria. Class I and class II major histocompatibility complex (MHC) antigens were studied by standard microlymphocytotoxicity assays. Class II MHC antigens were further studied by polymerase chain reaction (PCR) amplification of HLA-DRB1, DQA, and DQB genes and allele-specific oligonucleotide hybridization. For comparison purposes, we used results obtained from a group of 100 ethnically matched healthy individuals.

RESULTS

We found that all eight patients had the HLA-DR3/DR4 phenotype; all HLA-DR3 haplotypes were HLA-DRB1*0301, DQA1*0501, and DQB1*0201, whereas half of the HLA-DR4 haplotypes were from the DRB1*0401 subtype and the other half were DRB1 *0407.

CONCLUSIONS

These results suggest that, in Mexicans, the genetic susceptibility for the development of PG is strongly influenced by the genetic admixture of Caucasian origin, and the role of class II MHC antigens in the pathophysiology of this disease is confirmed.

Etiology and pathogenesis of preeclampsia: current concepts

The etiology of preeclampsia is unknown. At present, 4 hypotheses are the subject of extensive investigation, as follows: (1) Placental ischemia-Increased trophoblast deportation, as a consequence of ischemia, may inflict endothelial cell dysfunction. (2) Very low-density lipoprotein versus toxicity-preventing activity-In compensation for increased energy demand during pregnancy, nonesterified fatty acids are mobilized. In women with low albumin concentrations, transporting extra nonesterified fatty acids from adipose tissues to the liver is likely to reduce albumin's antitoxic activity to a point at which very-low density lipoprotein toxicity is expressed. (3) Immune maladaptation-Interaction between decidual leukocytes and invading cytotrophoblast cells is essential for normal trophoblast invasion and development. Immune maladaptation may cause shallow invasion of spiral arteries by endovascular cytotrophoblast cells and endothelial cell dysfunction mediated by an increased decidual release of cytokines, proteolytic enzymes, and free radical species. (4) Genetic imprinting-Development of preeclampsia-eclampsia may be based on a single recessive gene or a dominant gene with incomplete penetrance. Penetrance may be dependent on fetal genotype. The possibility of genetic imprinting should be considered in future genetic investigations of preeclampsia.

Maternal and fetal plasma concentrations of endothelin, lipidhydroperoxides, glutathione peroxidase and fibronectin in relation to abnormal umbilical artery velocimetry

OBJECTIVE

To study plasma concentrations of endothelin (ET), lipidhydroperoxides (LOOH), glutathione peroxidase (GSHpx) and fibronectin in relation to abnormal umbilical artery velocimetry.

STUDY DESIGN

Plasma concentrations of ET, LOOH, GSHpx and fibronectin were measured in fetal and maternal venous blood in: (i) a control group (n=10); (ii) in pregnancies complicated by intrauterine growth retardation (IUGR) (n=6) or preeclampsia (n=5) with positive end diastolic flow; and in (iii) pregnancies complicated by absent or reversed end diastolic (ARED) flow in the umbilical artery (n=18). All children were delivered by primary caesarean section.

RESULTS

The significantly highest maternal and fetal ET concentrations were found in plasma collected in pregnancies complicated by ARED flow in the umbilical artery. Maternal fibronectin levels were significantly raised in the ARED flow group. Maternal plasma ET levels were lowest in pregnancies complicated by IUGR. The maternal and fetal plasma concentrations of LOOH and GSHpx did not differ significantly between the groups.

CONCLUSION

Abnormal Doppler velocimetry, especially ARED flow is associated with elevated maternal and fetal plasma levels of ET. The exact mechanism causing the placental vasoconstriction is unknown yet, but oxidative stress seems not to be involved.

Preeclampsia: haemostatic status and the short-term effects of methyldopa and isradipine therapy

OBJECTIVE

To determine the haemostatic status in preeclampsia and to investigate the effects of short-term use of anti-hypertensive drugs, methyldopa and isradipine.

METHODS

Thirty preeclamptic (PE) women admitted to the hospital for observation and treatment were randomized to receive either methyldopa or isradipine for 2 weeks. Their blood pressure were monitored for 24 h before treatment and again at 7 days and 14 days after treatment using the programmable automated ambulatory blood pressure (ABP) monitoring system. Blood sampling was performed before commencement of anti-hypertensive treatment, 7 days and 14 days after treatment and the haemostatic parameters studied was compared before treatment with normal pregnancy and the effect of anti-hypertensive treatment. Nineteen normal pregnant subjects with a total of 30 blood sampling at various gestation and good pregnancy outcome served as controls. The following haemostatic parameters were determined; thrombelastography, fibrinogen, antithrombin III (ATIII), thrombin-antithrombin (TAT)-complex, beta-thromboglobulin (beta-TG), plasminogen activators (t-PA, u-PA), plasminogen activator inhibitors (PAI-1, PAI-2), and plasminogen.

RESULTS

Significant lowering of blood pressure was evident at Days 7 and 14 of therapy with either methyldopa or isradipine. Increased mean plasma fibrinogen and decreased ATIII levels were seen in preeclampsia together with decreased u-PA and t-PA activity levels in contrast to increased t-PA antigen and beta-TG. No significant differences were seen for TAT-complex, PAI-1, plasminogen and D-dimer levels although their mean levels were higher than observed in non-pregnant subject except for PAI-2, the level was significantly reduced when compared with normal pregnancy. Two-way analysis of variance showed no significant alteration on all haemostatic parameters studied in preeclamptic women receiving either methyldopa or isradipine after 7 and 14 days of therapy.

CONCLUSION

Enhance activation of coagulation was observed together with raised fibrinolysis in normal pregnancy and PE. However, in PE a further reduction in ATIII, u-PA and PAI-2 with increased fibrinogen and platelet activation could lead to an imbalance in the coagulation/fibrinolysis equilibrium which favours fibrin deposition. All these changes seen in PE including the coagulation kinetics were not altered by the short term effects of methyldopa and isradipine even though significantly lowered blood pressure were observed during therapy.

The prediction of preeclampsia: reassessment of clinical value of increased plasma levels of fibronectin

OBJECTIVE

To determine whether assessment of plasma fibronectin in primigravidae could predict the pregnant women expected to become preeclamptic.

METHODS

We performed a prospective blinded analysis of 156 apparently normotensive primigravidae in an outpatient clinic. Blood samples were taken at 6 week intervals from the 18th week and immediately after delivery or at the onset of preeclampsia. Plasma fibronectin was evaluated by ELISA. Evolution with gestational age was studied using regression curves.

RESULTS

We had 148 normal primigravidae (592 determinations). In three women, increased fibronectin anticipated preeclampsia by 3-4 weeks. Five women showed high levels only at the onset of preeclampsia. Sensitivity, specificity, positive and negative predictive values of increased fibronectin levels were 37.5% (95% CI=3.3-71.7), 96.6% (95% CI=93.7-99.6), 37.5% (95% CI=3.3-71.7) and 96.6% (95% CI=93.7-99.6), respectively.

CONCLUSIONS

This study shows that plasma fibronectin levels could represent a specific marker for preeclampsia. Its sensitivity has to be improved but its high negative predictive value strongly argues against the development of preeclampsia within the next 4 weeks after the blood sampling.

The diagnostic accuracy of cervico-vaginal fetal fibronectin in predicting preterm delivery: an overview

OBJECTIVE

To determine the accuracy with which cervico-vaginal fetal fibronectin predicts preterm delivery using systematic quantitative overview of the available literature.

DESIGN

Online searching of MEDLINE database (1966 to April 1996), scanning of bibliography of known primary and review articles and review of recent journal issues. Study selection, assessment of study quality and data extraction were performed in duplicate under masked conditions. Likelihood ratios were generated in subgroups of symptomatic and asymptomatic pregnant women by pooling data from different studies. An LR of > 10 or < 0.1 indicated conclusive changes in the pretest probability of preterm delivery while an LR of 5-10 or 0.2-0.1 indicated only moderate changes.

PARTICIPANTS

Seven hundred and twenty-three symptomatic women with threatened preterm labour included in nine studies and 847 asymptomatic women (635 low risk and 212 high risk) included in six studies selected for meta-analyses.

MAIN OUTCOME MEASURES

Likelihood ratios for positive and negative test results using delivery at < 37 and < 34 weeks of gestation, and within one week of testing as outcome measures.

RESULTS

In symptomatic women a positive test predicted delivery < 37 weeks of gestation with a pooled likelihood ratio (LR) of 4.6 (95% CI 3.5-6.1) while a negative test had a pooled LR of 0.5 (95% CI 0.4-0.6). For delivery < 34 weeks of gestation, the pooled LR was 2.6 (95% CI 1.8-3.7) for a positive test and 0.2 (95% CI 0.1-0.5) for a negative test. For delivery within one week of testing, the pooled LR was 5.0 (95% CI 3.8-6.4) for a positive test and 0.2 (95% CI 0.1-0.4) for a negative test. In asymptomatic women at low risk of delivery < 37 weeks of gestation the pooled LR was 3.2 (95% CI 2.2-4.8) for a positive test and 0.8 (95% CI 0.7-0.9) for a negative test. In high risk asymptomatic women using delivery < 37 weeks of gestation as an outcome measure the pooled LR was 2.0 (95% CI 1.5-2.6) for a positive test and 0.4 (95% CI 0.2-0.8) for a negative test. For delivery < 34 weeks of gestation in high risk, asymptomatic women the pooled LR was 2.4 (95% CI 1.8-3.2) for a positive test and 0.6 (95% CI 0.4-0.9) for a negative test.

CONCLUSION

The presence of fetal fibronectin in cervico-vaginal mucus has limited accuracy in predicting preterm delivery as the likelihood ratios for positive and negative test results generated only minimal to moderate changes in the pretest probability of preterm birth.

Placental cytokines and the pathogenesis of preeclampsia

The authors explore the hypothesis that tumor necrosis factor-alpha (TNF-alpha) and possibly other inflammatory cytokines are overproduced by the placenta in response to local ischemia/hypoxia contributing to increased plasma levels, and subsequent endothelial activation and dysfunction in the pregnancy disorder, preeclampsia. It is widely held that inadequate trophoblast invasion and physiologic remodeling of spiral arteries initiate placental ischemia/hypoxia in preeclampsia. Furthermore, focal areas of placental hypoxia have been implicated in the production of "toxic" factor(s) by the placenta, which circulate and cause maternal disease. Placental trophoblast cells and fetoplacental macrophages normally produce TNF-alpha and interleukin-1 (IL-1), which are capable of producing endothelial cell activation and dysfunction. Hypoxia has recently been reported to increase TNF-alpha and IL-1 production by term villous explants from the human placenta. Placental cells also express erythropoietin (EPO), which is the prototype molecule for transcriptional regulation by hypoxia in mammals. Interestingly, TNF-alpha and IL-1 have DNA sequence homologous or nearly homologous to the hypoxia-responsive enhancer element of the EPO gene, thus providing a potential, but as of yet, untested molecular link between placental hypoxia and stimulation of cytokine production. Inflammatory cytokines overproduced by the placenta in response to hypoxia may then lead to increased plasma levels and endothelial activation and dysfunction in preeclampsia. The purpose of this short review is to critically evaluate the hypothesis that placental cytokines contribute to the pathogenesis of preeclampsia. Of note, the etiology of the disease presumably related to deficient trophoblast invasion is beyond the scope of this work.

Nifedipine reduces thromboxane A2 production by platelets without changing aggregation in hypertensive pregnancy

Platelet aggregation and thromboxane A2 generation were studied in hypertensive pregnant women using normotensive non-pregnant and pregnant controls. In hypertensive pregnancy, adrenaline- and adenosine diphosphate-induced platelet aggregation was at the non-pregnant level and lower than in normotensive pregnancy. Collagen-induced aggregation was at a lower level in hypertensive pregnancy than in both control groups. Thromboxane generation during spontaneous clotting and in platelet-rich plasma did not differ between the three groups. However, thromboxane generation was low during aggregation induced by small collagen concentrations in hypertensive pregnancy, but at higher collagen concentrations the difference between the groups disappeared. During nifedipine treatment (10 mg t.i.d.), aggregation and thromboxane production in platelet-rich plasma induced by the three stimuli remained unaltered in hypertensive pregnancy, while thromboxane synthesis during spontaneous clotting was reduced. In nifedipine-treated non-pregnant controls, only EC80 for adrenaline-induced aggregation decreased. In vitro, pharmacological concentrations of nifedipine inhibited platelet aggregation and thromboxane production. In conclusion, nifedipine reduces thromboxane generation in spontaneous clotting, without inhibiting platelet aggregation and thromboxane production in platelet-rich plasma in hypertensive pregnancy. Reduced aggregability of platelet ex vivo may reflect their continuous activation and desensitization in vivo in hypertensive pregnancy.

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.

Detection of fetal fibronectin as a predictor of preterm delivery in high risk asymptomatic pregnancies

OBJECTIVE

The study was designed to determine whether fetal fibronectin would predict delivery before 37 weeks in women at high risk of preterm delivery.

STUDY METHODS

Forty-three women considered at risk of preterm delivery were recruited antenatally into a blind longitudinal study. Quantitative assays of fetal fibronectin were obtained from sequential high vaginal swabs taken fortnightly from 24 to 34 weeks of gestation. Fibronectin concentrations of 0.05 microgram/ml or more were considered as positive.

RESULTS

Results were calculated by swab and by subject. The sensitivity of an individual fibronectin swab in predicting preterm delivery within 14 days of testing was 71% and the specificity was 93%. The overall positive predictive value was 31% and the negative predictive value was 99%. The sensitivity of the fibronectin swab in predicting delivery before 37 weeks was 17% and the specificity was 93%. The positive predictive value was 50% and the negative predictive value was 73%. For a woman who has had a positive swab the sensitivity in predicting preterm delivery within 14 days of testing was 80% and the specificity was 83%; a woman was counted as positive only if the final swab was positive and preceded delivery by not more than 14 days. The positive predictive value was 36% and the negative predictive value was 97%. For a woman who has had a positive swab the sensitivity in predicting delivery before 37 weeks was 54%. The specificity, the positive predictive value and the negative predictive value were 85%, 64% and 79%, respectively. Women were counted as positive if any swab in the sampling sequence was positive. Fibronectin swabbing when calculated by patient did predict preterm delivery within 14 days of testing (P=0.01) and before 37 weeks (P=0.01). Analysis of the accuracy of predicting delivery from 7 to 28 days after sampling revealed that the best prediction for delivery was within the following 14 days.

CONCLUSION

Serial fetal fibronectin assessment from 24 to 34 weeks of gestation anticipated preterm delivery within 14 days of testing and before 37 weeks for high risk asymptomatic women. Such testing should be performed every two weeks.

Platelet sensitivity to prostaglandin E1 inhibition is reduced in pre-eclampsia but not in nonproteinuric gestational hypertension

OBJECTIVE

Platelet aggregometry was used to discriminate platelet sensitivity to prostaglandin E1 (PGE1) inhibition, to evaluate whether platelet behaviour in pre-eclamptic women was different in this respect than from that in nonproteinuric hypertensive women.

METHODS

The amount of PGE1 required to inhibit in vitro platelet aggregation induced by arachidonic acid was determined in samples from 60 women: 20 nonpregnant controls, 20 women with normal pregnancies, 10 women with gestational hypertension and 10 with pre-eclampsia.

RESULTS

The response to arachidonic acid was similar among the four groups. Amounts of PGE1 necessary to inhibit platelet aggregation were significantly higher in normal pregnant women compared with nonpregnant controls (P<0.001). Platelets from pre-eclamptic women required significantly higher concentrations of PGE1 to inhibit aggregation than the other groups studied (P<0.001). However, there was no significant difference between normal and nonproteinuric hypertensive pregnant women.

CONCLUSIONS

Our findings support the notion that increased platelet reactivity during late pregnancy is exacerbated in pre-eclamptic women but not in nonproteinuric hypertensive women. This is in agreement with the hypothesis that pre-eclampsia and gestational hypertension are different conditions. Prospective studies are required to confirm if this simple test may be useful in the early identification of pregnant women at risk for pre-eclampsia.

The pharmacological prevention of pre-eclampsia

The disparate results reported in the literature on the effects of low dose aspirin in preventing pre-eclampsia might be caused by non-compliance in the more recent large trials in low-risk patients. All the earlier small trials were done on identified high-risk patients who consider themselves as patients, as do their doctors. Compliance in these patients will be very high. In fact, the only study in healthy subjects in which aspirin intake was controlled for (Hauth et al 1993) showed a marked reduction in the incidence of pre-eclampsia. However, the recent large trials have demonstrated, without any doubt, that low dose aspirin is not a miracle drug. The combined literature points at a 25% reduction in the incidence of pre-eclampsia in association with the use of aspirin (Collins, 1994). The correct indication for the use of low-dose aspirin appears to be the patient that is at very high risk of developing early-onset (less than 32 weeks gestation) pre-eclampsia. Since early-onset pre-eclampsia can begin at any time after 20 weeks gestation, it is necessary to initiate low-dose aspirin therapy early in pregnancy, preferably at 10-14 weeks gestation. The results of the recent large trials emphasize the need for a reliable, sensitive method of predicting or detecting pre-eclampsia at a very early gestational age (Dekker and Sibai, 1991). Valensise et al (1993) recently confirmed earlier studies (McParland et al, 1990) on the useful combination of uteroplacental Doppler flow velocimetry and aspirin in low-risk primigravidae. Results from current large-scale trials, such as the ECPPA, the BLASP, the WHO Jamaica and the second NICHHD studies, will be available in the near future. The results of especially the second NICHHD study on low-dose aspirin, in more than 2000 high-risk women (previous pre-eclampsia/eclampsia, chronic hypertension, class B to F diabetes or multiple gestation), will hopefully give us a more definitive picture on the potential benificial effects of low-dose aspirin in high-risk patients. The effect of aspirin on placental TXA2 deserves further studies. It might be that the optimal level to inhibit placental TXA2 and lipid peroxide production is actually higher than the minimal effective doses of aspirin that are needed to inhibit platelet TXA2 production (Walsh, 1994). Low-dose aspirin appears to be safe for the fetus and neonate. If there is an increased risk of abruptio placentae, this risk appears to be minimal. The final word on the use of low-dose aspirin has not yet been reached; however, we may be getting closer to profiling patients for whom the therapy may be efficacious and beneficial to both mother and fetus. Further studies are also necessary on combinations of aspirin and other antithrombotic drugs, such as heparin or ketanserin (Tanaka et al, 1993; Bolte et al, 1994; North et al, 1994). North et al (1994) demonstrated that treatment of women with severe renal disease with heparin plus aspirin reduced the prevalence of superimposed pre-eclampsia, compared with no treatment or aspirin alone. Next to low-dose aspirin, there appear to be several new and promising pharmaceutical approaches for reducing the consequences of EC dysfunction. Among these are selective TXA2-synthetase or TXA2-receptor antagonists, Serotonin2-receptor blockers, stable PGI2 analogues and NO donors.

Excretion of prostacyclin and thromboxane metabolites before, during, and after pregnancy-induced hypertension

The aim of the present study was to assess whether changes in prostacyclin (PGI2) and thromboxane (TXA2) generation precede the manifestation of pregnancy-induced hypertension (PH). The metabolites 6-oxo-PGF1 alpha and TXB2 were measured in the urine of 69 randomly selected pregnant women from 16-20 weeks of gestation (wg) until delivery and more than 6 weeks postpartum. Between 16-20 and 21-24 wg 6-oxo-PGF1 alpha excretion did not change in patients who later developed PIH (n = 6) but increased significantly in the control group (n = 63). In contrast, a marked rise in TXB2 excretion was found in the PIH group but not in controls. Thereafter significant differences between both groups persisted from 25 wg until delivery. The 6-oxo-PGF1 alpha/TXB2 ratio was below the 10th percentile from 21-24 wg until delivery in patients with developing PIH. The excretion of both metabolites was substantially lower in the non-pregnant state without any difference between patient groups. These results show an altered urinary excretion of both 6-oxo-PGF1 alpha and TXB2 preceding the onset of the disease. A pathophysiological role of PGI2 deficiency and increased TXA2 formation in PIH appears substantiated.

Hemostasis and diagnosis of preeclampsia

The diagnosis of preeclampsia, with all of its consequences, is at times difficult to establish, especially when the patient has underlying chronic hypertension and is not known from prior prenatal care visits. Many screening tests have been proposed. These should be sensitive, relatively specific, easy to perform, of low cost, and have a reasonable interval from prediction to disease onset. Laboratory assays would obviously be useful. We evaluated hemostasis tests for the diagnosis of preeclampsia, and compared fibronectin, antithrombin III and alpha 2-antiplasmin in 48 preeclamptics and 86 control nulliparas. Receive operator characteristic (ROC) curve analysis suggested that fibronectin is the most effective of these tests. A similar analysis comparing the results of previous studies using serum iron, angiotensin infusion, urinary calcium/creatinine ratio, the rollover test and uric acid suggested a possible role for fibronectin in the diagnosis of preeclampsia. While not ideal, there seems to be, at present, no other, easy to perform laboratory test that outperforms fibronectin in predicting preeclampsia.

Systemic and uterine vascular response to serotonin in third trimester pregnant ewes

Released from aggregating platelets, serotonin (5HT) among other vasoactive components is considered to play an important role in preeclampsia, one of the most common medical complications of pregnancy. This study was designed to evaluate the simultaneous uterine and systemic vascular effects of systemically administered serotonin in pregnant sheep and compare them to the well known effects of angiotensin II and norepinephrine. Nine instrumented pregnant ewes received intravenous (inferior vena cava) infusions of increasing doses of serotonin, norepinephrine and angiotensin II in random order. Cardiac output, arterial blood pressure, heart rate, and uterine blood flow were recorded. Systemic administration of serotonin at doses of 2, 4, and 8 micrograms/kg body weight/min caused a slight increase in mean arterial blood pressure (1, 4 and 11%), a large decrease in uterine blood flow (10, 37, and 71%) but did not change cardiac output. Serotonin led to an increase in uterine vascular resistance with only small changes in systemic vascular resistance (UVR 17, 107, and 363% vs. SVR 3, 10 and 11%). In contrast, angiotensin II increased both systemic and uterine vascular resistance (SVR 16, 37, 56, and 95% and UVR 5, 16, 28 and 99%). Norepinephrine also raised both systemic and uterine vascular resistance, though to a different extent (SVR 5, 17, 37, and 118% vs. UVR 5, 46, 84 and 304%). Systemic infusions of serotonin in third trimester pregnant ewes resulted in uterine vasoconstriction. In contrast to the marked effect on the uterine vasculature, the systemic cardiovascular responses were small, thus demonstrating a nearly selective effect of serotonin on the uterine vasculature at the doses administered.(ABSTRACT TRUNCATED AT 250 WORDS)