Maternal plasma level of thrombomodulin is increased in mild preeclampsia

Circulating concentrations of glycocalyx degradation products in preeclampsia

Background and Objectives: Preeclampsia is a multisystem disorder that affects maternal endothelium. The glycocalyx lines and protects the endothelial surface. In severe systemic diseases, like sepsis, it is shed and glycocalyx degradation products can be detected in increased concentrations in plasma. The aim of this study was to compare circulating concentrations of glycocalyx degradation products in degrees of preeclampsia severity.

Study design: In this observational study, we included women from the South African PROVE biobank. Women were divided into normotensive controls, women with preeclampsia without end-organ complications, women with a single end-organ complication and women with multiple end-organ complications. Plasma samples taken at inclusion after diagnosis (preeclampsia cases) or at admission for delivery (normotensive controls) were analyzed with ELISA for syndecan-1, hyaluronic acid and thrombomodulin and compared between groups.

Results: Women with preeclampsia (n = 47) had increased plasma concentrations of hyaluronic acid (100.3 ng/ml IQR 54.2–204 vs. 27.0 ng/ml IQR (13.5–66.6), p < 0,001) and thrombomodulin (4.22 ng/ml IQR 3.55–5.17 vs. 3.49 ng/ml IQR 3.01–3.68, p = 0.007) but not syndecan-1 compared with normotensive women (n = 10). There were no differences in plasma concentration in any of these biomarkers in women with preeclampsia with no end-organ complications (n = 10) compared with women with preeclampsia and one end-organ complication (n = 24). Women with preeclampsia with two or more end-organ complications (n = 13) had increased plasma concentrations of thrombomodulin (5.46 ng/ml, IQR 4.85–7.83 vs. 4.66 ng/ml, IQR 3.45–4.88, p = 0.042) compared with women with preeclampsia and no end-organ complications.

Conclusion: Thrombomodulin was associated with disease severity and may be valuable for risk-stratifying women with preeclampsia.

Circulating Thrombomodulin: Release Mechanisms, Measurements, and Levels in Diseases and Medical Procedures

Thrombomodulin (TM) is a type-I transmembrane protein that is mainly expressed on endothelial cells and plays important roles in many biological processes. Circulating TM of different forms are also present in biofluids, such as blood and urine. Soluble TM (sTM), comprised of several domains of TM, is the major circulating TM which is generated by either enzymatic or chemical cleavage of the intact protein under different conditions. Under normal conditions, sTM is present in low concentrations (<10 ng/mL) in the blood but is elevated in several pathological conditions associated with endothelial dysfunction such as cardiovascular, inflammatory, infection, and metabolic diseases. Therefore, sTM level has been examined for monitoring disease development, such as disseminated intravascular coagulation (DIC), sepsis and multiple organ dysfunction syndrome in patients with novel coronavirus disease 2019 (COVID-19) recently. In addition, microvesicles (MVs) that contain membrane TM (MV-TM) have been found to be released from activated cells which also contribute to levels of circulating TM in certain diseases. Several release mechanisms of sTM and MV-TM have been reported, including enzymatic, chemical, and TM mutation mechanisms. Measurements of sTM and MV-TM have been developed and explored as biomarkers in many diseases. In this review, we summarize all these advances in three categories as follows: (1) release mechanisms of circulating TM, (2) methods for measuring circulating TM in biological samples, and (3) correlation of circulating TM with diseases. Altogether, it provides a whole picture of recent advances on circulating TM in health and disease.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Microcirculation in Pregnancy

The microcirculation, like all physiological systems undergoes modifications during the course of pregnancy. These changes aid the adaption to the new anatomical and physiological environment of pregnancy and ensure adequate oxygen supply to the fetus. Even though the microcirculation is believed to be involved in major pregnancy related pathologies, it remains poorly understood. The availability of safe and non-interventional technologies enabling scientists to study the intact microcirculation of the pregnant patient will hopefully expand our understanding. In this article we review the physiological changes occurring in the microcirculation during pregnancy and the role of the microcirculation in gestational related pathologies. We will also describe the available techniques for the measurement and evaluation of the microcirculation. Lastly we will highlight the possible fields in which these techniques could be utilized to help provide a clearer view of the microcirculation in the pregnant woman.

Maternal plasma concentrations of sST2 and angiogenic/anti-angiogenic factors in preeclampsia

OBJECTIVES

Angiogenic/anti-angiogenic factors have emerged as one of the promising biomarkers for the prediction of preeclampsia. Since not all patients with preeclampsia can be identified by these analytes, the search for additional biomarkers continues. The soluble form of ST2 (sST2), a protein capable of binding to interleukin (IL)-33 and thus contributing to a Th1-biased immune response, has been reported to be elevated in maternal plasma of women with preeclampsia. The aims of this study were to examine: (1) differences in maternal plasma concentrations of sST2 and IL-33 between women diagnosed with preeclampsia and those having uncomplicated pregnancies; (2) the relationship between sST2, umbilical and uterine artery Doppler velocimetry, and the severity of preeclampsia; and (3) the performance of sST2 and angiogenic/anti-angiogenic factors in identifying patients with preeclampsia at the time of diagnosis.

METHODS

This cross-sectional study included women with preeclampsia (n = 106) and women with an uncomplicated pregnancy (n = 131). Plasma concentrations of sST2, IL-33, soluble vascular endothelial growth factor receptor (sVEGFR)-1, soluble endoglin (sEng) and placental growth factor (PlGF) were determined by enzyme linked immune sorbent assay. Area under the receiver operating characteristic curve (AUC) for the identification of preeclampsia was examined for each analyte.

RESULTS

(1) Patients with preeclampsia had a higher mean plasma concentrations of sST2 than those with an uncomplicated pregnancy (p < 0.0001), while no significant difference in the mean plasma concentration of IL-33 between the two groups was observed; (2) the magnitude of this difference was greater in early-onset, compared to late-onset disease, and in severe compared to mild preeclampsia; (3) sST2 plasma concentrations did not correlate with the results of uterine or umbilical artery Doppler velocimetry (p = 0.7 and p = 1, respectively) among women with preeclampsia; (4) sST2 correlated positively with plasma concentrations of sVEGFR1-1 and sEng (Spearman's Rho = 0.72 and 0.63; each p < 0.0001), and negatively with PlGF (Spearman's Rho = -0.56, p < 0.0001); and (5) while the AUC achieved by sST2 and angiogenic/anti-angiogenic factors in identifying women with preeclampsia at the time of diagnosis were non-significantly different prior to term (<37 weeks of gestation), thereafter the AUC achieved by sST2 was significantly less than that achieved by angiogenic/anti-angiogenic factors.

CONCLUSIONS

Preeclampsia is associated with increased maternal plasma concentrations of sST2. The findings that sST2 concentrations do not correlate with uterine or umbilical artery Doppler velocimetry in women with preeclampsia suggest that elevated maternal plasma sST2 concentrations in preeclampsia are not related to the increased impedance to flow in the utero-placental circulation. The performance of sST2 in identifying preeclampsia at the time of diagnosis prior to 37 weeks of gestation was comparable to that of angiogenic/anti-angiogenic factors. It remains to be elucidated if an elevation of maternal plasma sST2 concentrations in pregnancy is specific to preeclampsia.

Pregnancy outcome and fibrinolytic, endothelial and coagulation markers in women undergoing uterine artery Doppler screening at 23 weeks

BACKGROUND

Pre-eclampsia (PET) and/or fetal growth restriction (FGR) remain a major cause of maternal and fetal morbidity and mortality. In pregnancy, fibrinolysis is controlled by the maternal endothelium and placenta, both of which are central to the pathogenesis of PET/FGR. Clinically, uterine artery Doppler screening at 23 weeks is used to predict PET/FGR. An abnormal uterine artery Doppler finding is defined as early diastolic bilateral uterine artery notching (BN) in the waveform. However, about 50% of mothers with BN do not develop PET/FGR.

OBJECTIVES

We investigated fibrinolytic changes and uterine artery Doppler findings in the second trimester, and related them to pregnancy outcome; in particular assessing whether fibrinolytic markers could discriminate between normal and abnormal outcome in mothers with BN.

PATIENTS/METHODS

Plasma levels of tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), plasminogen activator inhibitor-2 (PAI-2), plasmin-alpha(2) antiplasmin (PAP), D-dimers and markers of endothelial dysfunction were measured with Doppler ultrasound at 23 weeks.

RESULTS

Those with BN had decreased PAP and D-dimer levels, and raised PAI-1 and thrombomodulin levels. Mothers with BN and PET/FGR had significantly increased t-PA levels and reduced PAI-2 levels.

CONCLUSIONS

BN at 23 weeks of gestation is associated with increased PAI-1 levels. Within the BN group, mothers who developed PET/FGR had increased t-PA levels and decreased PAI-2 levels, although there was no net change in fibrinolysis as measured by D-dimer levels. No single fibrinolytic marker is helpful in determining pregnancy outcome in those with BN, but t-PA and PAI-2 are worthy of study in a multifactorial algorithm.

Correlation between maternal plasma thrombomodulin and infant birth weight in hypertensive disorders of pregnancy

OBJECTIVE

To evaluate the association between maternal plasma thrombomodulin levels and infant birth weights in pregnancy-induced hypertension.

STUDY DESIGN

Plasma thrombomodulin levels were measured in 80 pregnant women living in the Trakya region of Turkey. Of these patients, 30 were with severe preeclampsia, 10 with HELLP syndrome, 10 with eclampsia, and 30 were normotensive healthy pregnant women. Plasma thrombomodulin levels were determined by the enzyme-linked immunosorbent assay method. The correlation analysis between thrombomodulin and birth weight and placental weights was done using analysis of variance and Bonferroni test (significance at P < .05). Kruskal-Wallis statistical analysis was performed in comparison of the descriptive and laboratory data (significance at P < .05).

RESULTS

The plasma thrombomodulin values in hypertensive disorders in pregnancy were found to be highly correlated with the infant birth weights (P < .001). In HELLP syndrome, the highest thrombomodulin levels (94.69 + 10.41 ng/mL) were associated with the lowest infant birth weight (1509.70 + 187.55 g) in the study population. Thrombomodulin in eclampsia (81.37 + 3.59 ng/mL) showed an association with infant birth weight (2078 + 132.65 g). Although thrombomodulin levels in severe preeclampsia (67.15 + 3.72 ng/mL) were associated with the values (1748.20 + 132.62 g) in infant birth weight, thrombomodulin levels of the control group demonstrated the mean (48.06 + 2.45) with the highest infant birth weight (3228.85 + 84.83) in the total group.

CONCLUSION

Elevated plasma thrombomodulin levels in hypertensive disorders of pregnancy were well correlated with related infant birth weights of these pathologies. Plasma thrombomodulin levels might point out placental vascular endothelial damage reflecting on infant birth weights.

Increased endothelial thrombomodulin (TM) expression in pregnancies complicated by IUGR

Thrombomodulin (TM) is a cell surface receptor playing an important role in endothelial cell anticoagulant activity. TM is also known as a factor of angiogenesis; low TM activity correlates with impaired angiogenesis. Since vascular lesions with disorders of the placental coagulation and inadequate angiogenesis can be associated with IUGR, we hypothesized that thrombomodulin expression in the villous vasculature and syncytiotrophoblast of placentae complicated by IUGR might differ from those of normal pregnancies. Representative tissue samples of normal, IUGR as well as 1st and 2nd trimester (n = 12) placentae were collected. Immunohistochemistry (APAAP) of paraffin tissue sections was performed using monoclonal antibodies specific for TM and PECAM. The percentage of immunopositive vessels and the intensity of immunoreactivity was assessed. Vascular endothelium and syncytiotrophoblast stained positive for TM. Immunoreactivity for TM in villous vasculature rose significantly with gestational age. Villous vessels of IUGR placentae, showed a higher expression of TM, compared to placentae of appropriately grown fetus (p < 0.05). The number of terminal villi and the number of blood vessels per intermediate villi was significantly reduced in IUGR placentae (p < 0.05). These differences reflect inadequate vascularisation and impaired angiogenesis in IUGR.

Characterization of five marker levels of the hemostatic system and endothelial status in normotensive pregnancy and pre-eclampsia

OBJECTIVES

Pre-eclampsia is associated with changes in the hemostatic system and endothelial status. Urinary 11-dehydrothromboxane B2/creatinine (11-DTXB2/Cr) is a marker for platelet activation and vascular constriction, thrombin-antithrombin complex (TAT) for thrombin formation, serum thrombomodulin (TM) for endothelial damage, and beta-thromboglobulin (beta-TG) and platelet factor 4 (PF-4) for platelet activation and releasing reaction. The present study attempted to evaluate these five markers in normotensive pregnancy and pre-eclampsia.

METHODS

These five markers were simultaneously measured in urine and blood samples from 25 women who were not pregnant (group 1, controls), 31 women with normotensive pregnancy (group 2, second controls), 22 women with mild pre-eclampsia (group 3), and 21 women with severe pre-eclampsia (group 4). The average gestational age was 36 wk.

RESULTS

The 11-DTXB2/Cr, TAT, and beta-TG levels were significantly higher (P < 0.01) in groups 2, 3, and 4 than in group 1. The TM and beta-TG levels were significantly higher (P < 0.05) in group 3 than in group 2. The TM, beta-TG, and PF-4 levels were increased significantly (P < 0.05-0.01) in group 4 compared to those in groups 1, 2, and 3.

CONCLUSION

Platelet aggregation, vascular constriction, and thrombin formation (detected by 11-DTXB2/Cr and TAT) may be markedly enhanced even in group 2, but further enhancement may be relatively slight in groups 3 and 4. In contrast, endothelial damage (determined by TM) and platelet release of PF-4 may not increase significantly in group 2, but they may increase in group 4. Platelet-release of beta-TG may be enhanced in groups 2, 3, and 4. Endothelial damage and platelet-releasing reaction (detected by PF-4 and beta-TG) may be significantly more enhanced in group 4 than in group 3.

Interaction of the protein C/protein S anticoagulant system, the endothelium and pregnancy

Normal pregnancy is associated with significant changes in haemostasis, lipid metabolism and endothelial function. This suggests that maternal adaptation in these systems is required for successful pregnancy outcome. A number of acquired and heritable prothrombotic abnormalities are associated with complications in pregnancy. A common feature of these abnormalities is their ability to alter endothelial function or the protein C/protein S system and increase thrombin generation. In this review the normal function of the endothelium and the protein C/protein S system is detailed. The changes which characterize normal and complicated pregnancies are outlined and the evidence for the impact of heritable and acquired disorders of the protein C/protein S system on pre-eclampsia and fetal loss are discussed.

Thrombomodulin: an overview and potential implications in vascular disorders

Thrombomodulin (TM), a high affinity thrombin receptor present on endothelial cell membrane, plays an important role as a natural anticoagulant. It acts as a cofactor of thrombin-catalyzed activation of protein C, and inhibits the procoagulant functions of thrombin. TM is also located in other cells (keratinocytes, osteoblasts, macrophages,...) where it might be involved in cell differentiation or in inflammation. In the presence of cytokines, activated neutrophils and macrophages, endothelial TM is cleaved enzymatically, releasing soluble fragments which circulate in the blood and are eliminated in urine. Plasma TM level (pTM) can be measured using a two-site enzyme-linked immunosorbent assay (ELISA). pTM level is regarded as a molecular marker reflecting injury of endothelial cells. It is often increased in case of diffuse endothelial damage as in disseminated intravascular coagulation, diabetic microangiopathy, Plasmodium falciparum and rickettsial infections. pTM is also a predictive marker of hypertensive complications in pregnancy. In several systemic inflammatory diseases, pTM levels are correlated to the activity of the disease.

Increase in expression and activity of thrombomodulin in term human syncytiotrophoblast microvilli

A comparative study of thrombomodulin (TM), a potent natural anticoagulant, was performed in first trimester and term human placentae. Immunoreactive TM was observed on fetal vascular endothelium and syncytiotrophoblast at both gestational ages. Staining was stronger in term than in early placentae, particularly along the microvillous apical membrane of the syncytiotrophoblast. Similarly, a higher level of TM mRNA was detected by RT-PCR (P<0.02) and Northern blot analysis in extracts of whole term placentae. The localization of TM on syncytial microvilli was confirmed by electron microscopy after immunogold labelling. When isolated microvilli were compared at both gestational ages; a significant 2.3-fold increase in TM protein was observed in term microvilli as compared to first trimester microvilli by Western blot analysis (P<0.005) and ELISA (P<0.05). This higher level of TM in term microvilli was associated with an increase in its ability to activate protein C, from 3.7 +/- 1.2 to 8.7 +/- 4.2 mOD/min/microg protein +/- s.d. (P<0.01) in first trimester and term microvilli, respectively. The modulation of biologically active TM at the syncytial membrane exposed to maternal blood according to the length of gestation suggests that TM may be involved both in maternal haemostasis within the intervillous spaces, and also in the trophoblast differentiation process.

[Thrombomodulin: physiology and clinical applications (excluding systemic diseases)]

Thrombomodulin (TM) is a proteoglycan present on the surface of endothelial and mesothelial cells where it acts as a strong anticoagulant. TM is also located in other cells (keratinocytes, osteoblasts, mononuclear phagocytes...) where it might be involved in cell differentiation or inflammatory processes. The damage of endothelial cells releases cleavage fragments. Plasma TM appears to be a marker of endothelium damage. Plasma TM has been investigated in several disorders: it is usually increased in the case of diffuse endothelial damage.