Expression of the complement system's activation factors in plasma of patients with early/late-onset severe pre-eclampsia

Pregnancy as a susceptible state for thrombotic microangiopathies

Pregnancy and the postpartum period represent phases of heightened vulnerability to thrombotic microangiopathies (TMAs), as evidenced by distinct patterns of pregnancy-specific TMAs (e.g., preeclampsia, HELLP syndrome), as well as a higher incidence of nonspecific TMAs, such as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, during pregnancy. Significant strides have been taken in understanding the underlying mechanisms of these disorders in the past 40 years. This progress has involved the identification of pivotal factors contributing to TMAs, such as the complement system, ADAMTS13, and the soluble VEGF receptor Flt1. Regardless of the specific causal factor (which is not generally unique in relation to the usual multifactorial origin of TMAs), the endothelial cell stands as a central player in the pathophysiology of TMAs. Pregnancy has a major impact on the physiology of the endothelium. Besides to the development of placenta and its vascular consequences, pregnancy modifies the characteristics of the women's microvascular endothelium and tends to render it more prone to thrombosis. This review aims to delineate the distinct features of pregnancy-related TMAs and explore the contributing mechanisms that lead to this increased susceptibility, particularly influenced by the "gravid endothelium." Furthermore, we will discuss the potential contribution of histopathological studies in facilitating the etiological diagnosis of pregnancy-related TMAs.

Pre-eclampsia is associated with complement pathway activation in the maternal and fetal circulation, and placental tissue

OBJECTIVES

Pre-eclampsia (PE) is a leading cause of obstetric morbidity, with no definitive therapy other than delivery. We aimed to compare complement markers in maternal and fetal circulation, and placental tissue, between women with PE and healthy pregnant controls.

STUDY DESIGN

Maternal and umbilical cord blood was tested for iC3b, C3, C4, properdin, Ba and C5b-9, and placental tissue for C3d, C4d, C9 and C1q, from women with PE (n = 34) and healthy pregnant controls (n = 33). Maternal properdin and Ba tests were repeated in a separate validation cohort (PE n = 35; healthy pregnant controls n = 35).

MAIN OUTCOME MEASURES

Complement concentrations in maternal and umbilical cord blood, and placental immunohistochemical complement deposition.

RESULTS

Women with PE had significantly lower concentrations of properdin (mean: 4828 vs 6877 ng/ml, p < 0.001) and C4 (mean: 0.20 vs 0.31 g/l, p < 0.001), and higher Ba (median: 150 vs 113 ng/ml, p = 0.012), compared to controls. After controlling for gestational age at blood draw, average properdin concentration was 1945 ng/ml lower in PE vs controls (95 % CI: 1487-2402, p < 0.001). Of the cord blood markers assessed, only Ba differed significantly between PE and controls (median: 337 vs 233 ng/ml, p = 0.004). C4d staining of the syncytiotrophoblast membrane was increased in PE vs controls (median immunoreactivity score 3 vs 0, p < 0.001). Maternal properdin and C4 were significantly negatively correlated with placental C4d staining.

CONCLUSIONS

Our data confirm excessive placental complement deposition associated with significant concurrent changes in maternal and fetal circulating complement biomarkers in PE. Inhibition of complement activation is a potential therapeutic target.

The role of immune cells and mediators in preeclampsia

Preeclampsia is a hypertensive disorder of major concern in pregnancy than can lead to intrauterine growth restriction, placental abruption and stillbirth. The pathophysiology of preeclampsia is multifactorial, including not only kidney dysfunction but also endothelial dysfunction, as the maternal endothelium becomes exposed to placental factors that are released into the circulation and increase systemic levels of vasoconstrictors, oxidative stress, anti-angiogenic factors and inflammatory mediators. Importantly, inflammation can lead to insufficient placental perfusion and low birthweight in offspring. Various innate and adaptive immune cells and mediators have been implicated in the development of preeclampsia, in which oxidative stress is associated with activation of the maternal inflammatory response. Immune cells such as regulatory T cells, macrophages, natural killer cells, and neutrophils are known to have major causative roles in the pathology of preeclampsia, but the contributions of additional immune cells such as B cells, inflammatory cytokines and anti-angiotensin II type 1 receptor autoantibodies are also now recognized. Immunological interventions, therefore, have therapeutic potential in this disease. Here, we provide an overview of the immune responses that are involved in the pathogenesis of preeclampsia, including the role of innate and adaptive immune cells and mediators.

Urine excretion of C3dg and sC5b-9 coincide with proteinuria and development of preeclampsia in pregnant women with type-1 diabetes

OBJECTIVE

Pregnant women with type-1 diabetes have an increased risk of preeclampsia with kidney injury and cardiovascular complications. Urine excretion of plasmin and soluble membrane attack complex (sC5b-9) is elevated in severe preeclampsia. We hypothesized a coupling between these events and that active plasmin promotes intratubular complement activation and membrane deposition.

METHODS

Stored urine and plasma samples from pregnant women with type-1 diabetes (n = 88) collected at gestational weeks 12, 20, 28, 32, 36 and 38 were used. In the cohort, 14 women developed preeclampsia and were compared with 16 nonpreeclampsia controls.

RESULTS

Urine C3dg and sC5b-9-associated C9 neoantigen/creatinine ratios increased and were significantly higher in women who developed preeclampsia. Plasma concentrations did not change with gestation. Urine plasmin(ogen) correlated to urine C3dg (r = 0.51, P < 0.001) and C9 neoantigen (r = 0.68, P < 0.001); urine albumin correlated to C3dg (r = 0.44, P < 0.001) and C9 (r = 0.59, P < 0.001). Membrane-associated C3dg and C9 neoantigen was detected in urinary extracellular vesicles from patients but not controls at 36 weeks. Receiver operating characteristic curves showed that C3dg and C9 neoantigen were inferior to albumin as predictive biomarkers for preeclampsia.

CONCLUSION

In preeclampsia, urinary excretion of activated complement relates significantly to albuminuria and to plasmin(ogen) but not to activation in plasma. Intratubular complement activation in preeclampsia is a postfiltration event tightly related to proteinuria/plasminogenuria and a possible mechanistic link to cellular damage and kidney injury.

Variation of Complement Protein Levels in Maternal Plasma and Umbilical Cord Blood during Normal Pregnancy: An Observational Study

The complement system constitutes a crucial part of the innate immunity, mediating opsonization, lysis, inflammation, and elimination of potential pathogens. In general, there is an increased activity of the complement system during pregnancy, which is essential for maintaining the host’s defense and fetal survival. Unbalanced or excessive activation of the complement system in the placenta is associated with pregnancy complications, such as miscarriage, preeclampsia, and premature birth. Nonetheless, the actual clinical value of monitoring the activation of the complement system during pregnancy remains to be investigated. Unfortunately, normal reference values specifically for pregnant women are missing, and for umbilical cord blood (UCB), data on complement protein levels are scarce. Herein, complement protein analyses (C1q, C3, C4, C3d levels, and C3d/C3 ratio) were performed in plasma samples from 100 healthy, non-medicated and non-smoking pregnant women, collected during different trimesters and at the time of delivery. In addition, UCB was collected at all deliveries. Maternal plasma C1q and C3d/C3 ratio showed the highest mean values during the first trimester, whereas C3, C4, and C3d had rising values until delivery. We observed low levels of C1q and C4 as well as increased C3d and C3d/C3 ratio, particularly during the first trimester, as a sign of complement activation in some women. However, the reference limits of complement analyses applied for the general population appeared appropriate for the majority of the samples. As expected, the mean complement concentrations in UCB were much lower than in maternal plasma, due to the immature complement system in neonates.

Complement activation and regulation in preeclampsia and hemolysis, elevated liver enzymes, and low platelet count syndrome

The complement system is critical to human health owing to its central role in host defense and innate immunity. During pregnancy, the complement system must be appropriately regulated to allow for immunologic tolerance to the developing fetus and placenta. Although some degree of complement activation can be seen in normal pregnancy, the fetus seems to be protected in part through the placental expression of complement regulatory proteins, which inhibit complement activation at different steps along the complement activation cascade. In women who develop preeclampsia and hemolysis, elevated liver enzymes, and low platelet count syndrome, there is a shift toward increased complement activation and decreased complement regulation. There is an increase in placental deposition of C5b-9, which is the terminal effector of classical, lectin, and alternative complement pathways. C5b-9 deposition stimulates trophoblasts to secrete soluble fms-like tyrosine kinase-1, which sequesters vascular endothelial growth factor and placental growth factor. Pathogenic mutations or deletions in complement regulatory genes, which predispose to increased complement activation, have been detected in women with preeclampsia and hemolysis, elevated liver enzymes, and low platelet count syndrome. Before the disease, biomarkers of alternative complement pathway activation are increased; during active disease, biomarkers of terminal complement pathway activation are increased. Urinary excretion of C5b-9 is associated with preeclampsia with severe features and distinguishes it from other hypertensive disorders of pregnancy. Taken together, existing data link preeclampsia and hemolysis, elevated liver enzymes, and low platelet count syndrome with increased activation of the terminal complement pathway that, in some cases, may be influenced by genetic alterations in complement regulators. These findings suggest that the inhibition of the terminal complement pathway, possibly through C5 blockade, may be an effective strategy to treat preeclampsia and hemolysis, elevated liver enzymes, and low platelet count syndrome, but this strategy warrants further evaluation in clinical trials.

Influence of FOXP3 gene polymorphisms on the risk of preeclampsia: a meta-analysis and a bioinformatic approach

BACKGROUND AND AIM

Preeclampsia (PE), a multifactorial disorder, is the main cause of maternal mortality and morbidity. Genetic polymorphisms in key proteins involved in the immune system may change the risk of PE risk. In this study, we examined the association of two rs2232365 and rs3761548 common polymorphisms of the FOXP3 immune response gene with PE susceptibility by a meta-analysis which was followed by an in-silico analysis.

MATERIALS AND METHODS

Through a systematic search in databases including PubMed, MEDLINE, Google Scholar, and Science Direct, we find eligible studies for meta-analysis. Some bioinformatics tools were used to detect the impact of rs2232365 and rs3761548 polymorphisms on the FOXP3 gene function.

RESULTS

Our data revealed that there is a significant association between rs3761548 polymorphism and decreased risk of PE. In addition, we observed a significant association between rs2232365 and increased risk of mild preeclampsia. Also, our bioinformatic analysis showed that both rs2232365 and rs3761548 polymorphisms could affect FOXP3 gene function.

CONCLUSION

Based on our findings, the rs3761548 genetic variation could be a protective factor against PE risk. While the rs2232365 polymorphism may be a genetic risk factor for mild preeclampsia. Therefore, as a preliminary study, these genetic variations could be considered molecular biomarkers for PE disorder.

Phosphatidylserine Exposing Extracellular Vesicles in Pre-eclamptic Patients

Background: Pre-eclampsia (P-EC) is associated with systemic inflammation, endothelial dysfunction and hypercoagulability. The role of extracellular vesicles (EVs) in coagulation disturbances affecting the development and severity of P-EC remains elusive. We aimed to evaluate the concentration of EVs expressing phosphatidylserine (PS) and specific markers in relation to the thrombin and fibrin formation as well as fibrin clot properties, in pregnant women with P-EC in comparison to healthy pregnant women of similar gestational age.

Methods: Blood samples of 30 pregnant women diagnosed with P-EC were collected on the morning following admission to hospital and after delivery (mean duration 5 days). The concentration of the PS-exposing EVs (PS+ EVs) from platelets (CD42a⁺, endothelial cells (CD62E⁺), and PS+ EVs expressing tissue factor (TF) and vascular cell adhesion molecule 1 (VCAM-1) were measured by flow cytometry. Further phenotyping of EVs also included expression of PlGF. Markers of maternal haemostasis were correlated with EVs concentration in plasma.

Results: Preeclamptic pregnancy was associated with significantly higher plasma levels of PS+ CD42a⁺ EVs and PS+ VCAM-1⁺ EVs in comparison with normotensive pregnancy. P-EC patients after delivery had markedly elevated concentration of PS+ CD42a⁺ EVs, CD62E⁺ EVs, TF⁺ EVs, and VCAM-1⁺ EVs compared to those before delivery. Inverse correlation was observed between EVs concentrations (PS+, PS+ TF⁺, and PlGF⁺) and parameters of overall haemostatic potential (OHP) and fibrin formation, while PS+ VCAM-1⁺ EVs directly correlated with FVIII activity in plasma.

Conclusion: Increased levels of PS+ EVs subpopulations in P-EC and their association with global haemostatic parameters, as well as with fibrin clot properties may suggest EVs involvement in intravascular fibrin deposition leading to subsequent microcirculation disorders.

Dysregulation of complement system in HELLP syndrome

OBJECTIVE

To investigate the expression of complement system's activation factors in patients with HELLP syndrome.

METHODS

A case-control study was performed. Sixteen HELLP syndrome patients, 32 severe preeclampsia patients, and 48 normal pregnancy women were involved in this studyELISA was used to test C1q, C4d, MBL, Bb, C3a, C5a, sC5b-9, s-Endoglin, and sflt-1 in the plasma.

RESULTS

The levels of C5a (P < 0.01) and sC5b-9 (P = 0.014) in HELLP syndrome were higher than those in severe preeclampsia patients.

CONCLUSIONS

The abnormal activation of the complement system is more significant in the pathogenesis of HELLP syndrome than in severe preeclampsia.

Adipsin of the Alternative Complement Pathway Is a Potential Predictor for Preeclampsia in Early Pregnancy

Objective

The concentrations of complement proteins (adipsin, C3a, and C5a) and soluble endoglin (sENG) in the plasma were measured in this study, and their value as early-pregnancy predictors and potential diagnostic marker of preeclampsia was assessed, respectively.

Experimental Design

Plasma samples were obtained from healthy and preeclampsia pregnant women before delivery for a cross-sectional study. Plasma samples were collected from healthy and preeclampsia pregnant women throughout pregnancy and postpartum for a follow-up study. Enzyme-linked immunosorbent assays were used to detect plasma levels of several complement proteins (adipsin, C3a, and C5a) and sENG.

Results

The plasma levels of adipsin, C5a, and sENG were significantly increased before delivery in pregnant women with preeclampsia. During pregnancy, the plasma adipsin, C5a, and sENG levels were increased from the third trimester in healthy pregnant women; plasma adipsin levels remained stable after delivery, while C3a levels increased in the second trimester and remained stable afterward. Furthermore, levels of adipsin, C5a, and sENG were higher in preeclampsia patients at different stages of pregnancy; the C3a level presents a similar change and no difference was found in the third trimester. In the first trimester, receiver-operating curve (ROC) curve analysis showed that adipsin (AUC, 0.83 ± 0.06, P=0.001) and sENG (AUC, 0.74 ± 0.09, P=0.021) presented high value as predictors of early pregnancy.

Conclusions

Adipsin is likely a novel plasma biomarker to monitor the increased risk of preeclampsia in early pregnancy. Moreover, the increased plasma levels of adipsin, C5a, and sENG before delivery may be associated with preeclampsia.

The proteomes of endometrial stromal cell-derived extracellular vesicles following a decidualizing stimulus define the cells' potential for decidualization success

Adequate endometrial stromal cell (ESC) decidualization is vital for endometrial health. Given the importance of extracellular vesicles (EVs) in intercellular communication, we investigated how their protein landscape is reprogrammed and dysregulated during decidual response. Small EVs (sEVs) from human ESC-conditioned media at Day-2 and -14 following decidual stimuli were grouped as well- (WD) or poorly decidualized (PD) based on their prolactin secretion and subjected to mass spectrometry-based quantitative proteomics. On Day 2, in PD- versus WD-ESC-sEVs, 17 sEV- proteins were down-regulated (C5, C6; complement/coagulation cascades, and SERPING1, HRG; platelet degranulation and fibrinolysis) and 39 up-regulated (FLNA, COL1A1; focal adhesion, ENO1, PKM; glycolysis/gluconeogenesis, and RAP1B, MSN; leukocyte transendothelial migration). On Day 14, in PD- versus WD-ESC-sEVs, FLNA was down-regulated while 21 proteins were up-regulated involved in complement/coagulation cascades (C3, C6), platelet degranulation (SERPINA4, ITIH4), B-cell receptor signalling and innate immune response (immunoglobulins). Changes from Days 2 to 14 suggested a subsequent response in PD-ESC-sEVs with 89 differentially expressed proteins mostly involved in complement and coagulation cascades (C3, C6, C5), but no change in WD-ESC-sEVs ESC. Poor decidualization was also associated with loss of crucial sEV-proteins for cell adhesion and invasion (ITGA5, PFN1), glycolysis (ALDOA, PGK1) and cytoskeletal reorganization (VCL, RAC1). Overall, this study indicates varied ESC response even prior to decidualization and provides insight into sEVs-proteomes as a benchmark of well-decidualized ESC. It shows distinct variation in sEV-protein composition depending on the ESC decidual response that is critical for embryo implantation, enabling and limiting trophoblast invasion during placentation and sensing a healthy embryo.

New views on endothelial dysfunction in gestational hypertension and potential therapy targets

The placenta has vital roles in metabolite exchange, fetal growth, and pre-eclampsia (PE). In this review, we discuss the pathogenesis of hypertension in pregnancy, focusing on four major theories to explain PE, discussing endothelial roles in those theories. We focus in particular on the roles of nitric oxide (NO) and prostacyclin (PGI₂) in placental endothelium, and propose new hypotheses for the influence and mechanisms of endothelial NO and PGI₂ signaling pathways in PE.

Effect of magnesium sulfate combined with labetalol on serum sFlt-1/PlGF ratio in patients with early-onset severe pre-eclampsia

The aim of the present study was to investigate the therapeutic effect of magnesium sulfate combined with labetalol on the early-onset severe pre-eclampsia (ES-PE) and explore the role of soluble fms-like tyrosine kinase-1 (sFlT-1), placental growth factor (PlGF), and sFlt-1/PlGF ratio in the treatment. A total of 164 ES-PE patients admitted to the Maternity and Child Health Care Hospital of Hubei (Wuhan, China) were assigned to this observational study. Among them, 83 patients were enrolled in group A and treated with magnesium sulfate combined with labetalol hydrochloride, and 81 patients were enrolled in group B and treated with magnesium sulfate. The therapeutic effect, adverse reactions and pregnancy outcomes in the two groups were analyzed. Serum sFlt-1 and PlGF concentrations, before and after treatment, were measured by enzyme-linked immunosorbent assay (ELISA). Receiver operating characteristic (ROC) curve analysis was performed to assess the predictive value of pre-treatment serum sFlt-1/PlGF ratio for the clinical outcome. The effective rate was significantly higher in group A than that in group B. Group A presented superior pregnancy outcomes over group B. The serum sFlt-1 concentration and sFlt-1/PlGF ratio after treatment were significantly lower than those before treatment in groups A and B, whereas PlGF concentration was significantly higher after treatment in both groups. After treatment, group A had markedly lower serum sFlt-1 concentration and sFlt-1/PlGF ratio than group B, and markedly higher PlGF concentration than group B. The area under curve (AUC) of serum sFlt-1/PlGF ratio before treatment for the prediction of the clinical efficacy was 0.737. In conclusion, magnesium sulfate combined with labetalol could be effectively used for the treatment of ES-PE. The results of ELISA revealed that the balance of sFlT-1 and PlGF was improved after treatment and the sFlT-1/PlGF ratio was decreased. The assessment of sFlt-1/PlGF ratio before treatment was shown to have a certain predictive value for the efficacy of ES-PE treatment.

Mechanisms of Key Innate Immune Cells in Early- and Late-Onset Preeclampsia

Preeclampsia is a complex cardiovascular disorder of pregnancy with underlying multifactorial pathogeneses; however, its etiology is not fully understood. It is characterized by the new onset of maternal hypertension after 20 weeks of gestation, accompanied by proteinuria, maternal organ damage, and/or uteroplacental dysfunction. Preeclampsia can be subdivided into early- and late-onset phenotypes (EOPE and LOPE), diagnosed before 34 weeks or from 34 weeks of gestation, respectively. Impaired placental development in early pregnancy and subsequent growth restriction is often associated with EOPE, while LOPE is associated with maternal endothelial dysfunction. The innate immune system plays an essential role in normal progression of physiological pregnancy and fetal development. However, inappropriate or excessive activation of this system can lead to placental dysfunction or poor maternal vascular adaptation and contribute to the development of preeclampsia. This review aims to comprehensively outline the mechanisms of key innate immune cells including macrophages, neutrophils, natural killer (NK) cells, and innate B1 cells, in normal physiological pregnancy, EOPE and LOPE. The roles of the complement system, syncytiotrophoblast extracellular vesicles and mesenchymal stem cells (MSCs) are also discussed in the context of innate immune system regulation and preeclampsia. The outlined molecular mechanisms, which represent potential therapeutic targets, and associated emerging treatments, are evaluated as treatments for preeclampsia. Therefore, by addressing the current understanding of innate immunity in the pathogenesis of EOPE and LOPE, this review will contribute to the body of research that could lead to the development of better diagnosis, prevention, and treatment strategies. Importantly, it will delineate the differences in the mechanisms of the innate immune system in two different types of preeclampsia, which is necessary for a more personalized approach to the monitoring and treatment of affected women.

Dysregulation of complement system during pregnancy in patients with preeclampsia: A prospective study

Recent studies have shown that aberrant activation of the complement system plays an important role in the pathogenesis of preeclampsia. There is evidence to suggest that aberrant activation of the complement system may already be present during the first trimester. Here, we performed a prospective study in which peripheral blood samples were collected from 500 women during pregnancy. Twenty-one patients (41 specimens) suffering from preeclampsia later in pregnancy were classified into the study group, and sixty-three gravidas with normal pregnancies (136 specimens) were selected as the control group. The plasma concentrations of complement factor B (CFB), C1q, complement factor H (CFH), C3c, C4, C3a, C5a and soluble C5b-9 (sC5b-9) were measured. The levels of CFB (P = 0.004), CFH (P = 0.002), C1q (P = 0.044), C3c (P = 0.032) and C4 (P = 0.015) were significantly higher in preeclampsia than in normal pregnancy during the first trimester, and these levels became similar to those in normal pregnancy thereafter. Before the onset of preeclampsia, the levels of C3a, C5a and sC5b-9 in the preeclampsia group were similar to those in control group even in late pregnancy. C3a levels showed a significant positive correlation with C5a in normal pregnancy (r=0.658, P<0.01) but not in preeclampsia (r = 0.001, P = 1).Thus, we found that aberrant activation of the complement system in patients with preeclampsia was initiated during the first trimester but returned to normal pregnancy levels in the second trimester. At the same time, there is aberrant regulation of complement activation at the C3a-C5a level in preeclampsia during pregnancy.

Inflammation in Hypertension

For more than 50 years, evidence has accumulated that inflammation contributes to the pathogenesis of hypertension. Immune cells have been observed in vessels and kidneys of hypertensive humans. Biomarkers of inflammation, including high sensitivity C-reactive protein, various cytokines, and products of the complement pathway are elevated in humans with hypertension. Emerging evidence suggests that hypertension is accompanied and indeed initiated by activation of complement, the inflammasome, and by a change in the phenotype of circulating immune cells, particularly myeloid cells. High-dimensional transcriptomic analyses are providing insight into new subclasses of immune cells that are likely injurious in hypertension. These inflammatory events are interdependent and there is ultimately engagement of the adaptive immune system through mechanisms involving oxidative stress, modification of endogenous proteins, and alterations in antigen processing and presentation. These observations suggest new therapeutic opportunities to reduce end organ damage in hypertension might be used and guided by levels of inflammatory biomarkers.

Normal range of complement components during pregnancy: A prospective study

Problem

The complement system plays a key role in normal placentation, and delicate regulation of complement system activation is critical for successful pregnancy. Therefore, establishing a normal range of complement components during pregnancy is important for clinical evaluation and research.

Methods

We performed a prospective study to investigate the normal range of complement components in circulation during different stages of pregnancy. Plasma concentrations of complement factor B (CFB), C1q, complement factor H (CFH), C3, C3c, and C4 were measured using an immunoturbidimetric assay; mannan‐binding lectin (MBL), C3a, C5a, and soluble C5b‐9 (sC5b‐9) levels at different time points of pregnancy were determined by enzyme‐linked immunosorbent assay (ELISA).

Results

A total of 733 plasma samples were collected from 362 women with a normal pregnancy and 65 samples from non‐pregnant women. In the first trimester of pregnancy, the levels of CFB, CFH, MBL, C3c, C4, and C3a were 414.5 ± 85.9 mg/L (95% CI for mean: 402.4‐426.6 mg/L), 381.0 ± 89.0 mg/L (95% CI for mean: 368.5‐393.6 mg/L), 4274.5 ± 2752 ng/mL (95% CI for mean: 3881.1‐4656.4 ng/mL), 1346.9 ± 419.8 mg/L (95% CI for mean: 1287.7‐1406.0 mg/L), 357.4 ± 101.8 mg/L (95% CI for mean: 343.0‐371.7 mg/L), and 182.5 ± 150.0 ng/mL (95% CI for mean: 186.9‐229.1 ng/mL), respectively. The levels of C3 and C4 increased gradually throughout pregnancy. The levels of C1q, C5a, and sC5b‐9 in the first and second trimesters were nearly the same as those in non‐pregnant women.

Conclusion

The results of this study show that pregnancy itself may influence the plasma levels of complement system components.

Alterations in complement and coagulation pathways of human placentae subjected to in vitro fertilization and embryo transfer in the first trimester

The mechanisms underlying the potential risks of in vitro fertilization and embryo transfer (IVF-ET) have not been fully elucidated. The aim of this study was to explore changes in the complement and coagulation pathways in placentae subjected to IVF-ET in the first trimester compared to placentae from normal pregnancies. Four placenta samples in the first trimester were obtained from patients undergoing IVF-ET owing to oviductal factors only. An additional 4 control placentae were obtained from volunteers with normal pregnancies. A GeneChip Affymetrix HG-U133 Plus 2.0 Array was utilized to analyze the changes in gene expression between the normal and IVF-ET placentae. Differentially expressed genes (DEGs) were analyzed using the Database for Annotation and Visualization and Integrated Discovery bioinformatics resource, and gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted. Using real-time PCR, we confirmed the obtained microarray data in 10 dysregulated genes. Five of the gene products were further analyzed by immunohistochemistry (IHC) to determine their protein expression and localization. A total of fifty DEGs were identified in the complement and coagulation pathways in the IVF-ET treated placentae: 38 upregulated and 12 down-regulated. KEGG pathway analysis indicated that IVF-ET manipulation substantially over-activated the coagulation and complement pathways, while urokinase plasminogen activator- and urokinase plasminogen activator receptor-mediated trophoblastic invasion and tissue remodeling were inhibited. Furthermore, the 5 proteins analyzed by IHC were found to be localized specifically to the placenta. This is the first study to compare DEGs relating to the placental complement and coagulation pathways from patients undergoing IVF-ET treatment compared to those undergoing normal pregnancy. These findings identified valuable biomarkers and potential novel therapeutic targets to combat the unfavorable effects of IVF-ET.

Serum Levels of Complement Factors C1q, Bb, and H in Normal Pregnancy and Severe Pre-Eclampsia

Background

This study aimed to determine the diagnostic role of serum levels of complement C1q, Bb, and H in nonpregnant women, women with normal pregnancy, and women with severe pre-eclampsia.

Material/Methods

Healthy nonpregnant women (n=30), women with early, middle, and late normal pregnancy (n=30, respectively), and women with severe pre-eclampsia (n=73) were studied. The pre-eclampsia study group included early-onset cases (n=43) and late-onset cases (n=30). Serum levels of Bb were determined by enzyme-linked immunosorbent assay (ELISA), and C1q and H were tested by a turbidimetric immunoassay method.

Results

In the pre-eclampsia study group, compared with women with normal pregnancy, serum levels of C1q remained stable throughout pregnancy, and Bb levels declined from mid-pregnancy (p=0.250). Serum levels of factor H increased in the middle and late stages of pregnancy, and C1q and H were lower in early-onset severe pre-eclampsia (p<0.001, p=0.009, respectively) and late-onset severe pre-eclampsia (p<0.001, p=0.031, respectively) compared with the early-onset control and late-onset control groups. Serum levels of Bb increased in early-onset severe pre-eclampsia (p=0.001) and late-onset severe pre-eclampsia (p=0.003) compared with early-onset control and late-onset control groups. The area under the receiver operator curve (ROC) for serum C1q, Bb, and H for the diagnosis of early-onset severe pre-eclampsia were 0.814 (95% CI, 0.712–0.917), 0.743 (95% CI, 0.638–0.859), and 0.681(95% CI, 0.556–0.806), and late-onset severe pre-eclampsia were 0.805 (95% CI, 0.694–0.913), 0.796 (95% CI, 0.680–0.911), and 0.662 (95% CI, 0.524–0.800).

Conclusions

The classical and alternative pathways of complement were activated in patients with severe pre-eclampsia. Serum levels of C1q, Bb, and H should be studied further as potential diagnostic markers for severe pre-eclampsia.

Pre-eclampsia: pathophysiology and clinical implications

Pre-eclampsia is a common disorder that particularly affects first pregnancies. The clinical presentation is highly variable but hypertension and proteinuria are usually seen. These systemic signs arise from soluble factors released from the placenta as a result of a response to stress of syncytiotrophoblast. There are two sub-types: early and late onset pre-eclampsia, with others almost certainly yet to be identified. Early onset pre-eclampsia arises owing to defective placentation, whilst late onset pre-eclampsia may center around interactions between normal senescence of the placenta and a maternal genetic predisposition to cardiovascular and metabolic disease. The causes, placental and maternal, vary among individuals. Recent research has focused on placental-uterine interactions in early pregnancy. The aim now is to translate these findings into new ways to predict, prevent, and treat pre-eclampsia.

Placental sFLT1 is associated with complement activation and syncytiotrophoblast damage in preeclampsia

The immune complement system protects against pathogens; however, excess activation results in disease like hemolytic uremic syndrome, a clinical imitator of preeclampsia. Vascular endothelial factor (VEGF) protects against aberrant complement activation and is inhibited by soluble fms-like tyrosine kinase-1 (sFLT1) in other organs. We hypothesize that sFLT1 promotes complement-mediated placental damage through VEGF inhibition in preeclampsia. Objective: Quantify placental complement activity and sFLT1 expression in preeclampsia, and the subgroup of preeclampsia with hemolysis elevated liver enzymes low platelets (HELLP) syndrome. Methods: Placental complement activation marker C4d, membrane attack complex (MAC), and sFLT1 expression was quantified using immunofluores cence microscopy. Results: Placentas from 18 controls, 25 preeclampsia, including 6 cases of HELLP syndrome were identified. Placental C4d expression was greater in PE (median 6.4 [IQR: 5.1, 8.3]) compared to controls (4.4 [3.6, 5.5]; p = 0.003). MAC expression was also increased in preeclampsia compared to controls (6.5 [5.8, 8.7]; 5.4 [2.9, 5.9], p = 0.001). Placental sFLT1 expression was also higher in preeclampsia (p <0.0001). C4d and MAC were strongly correlated with sFLT1 levels in the placenta (R = 0.72; p < 0.0001 and R = 0.59; p = 0.01, respectively). Complement and sFLT1 expression was elevated in HELLP compared to preeclampsia without laboratory abnormalities, but this difference did not reach statistical significance. Conclusion: Increased placental complement activation and damage was seen in preeclampsia and correlates with sFLT1 expression. Our findings support the importance of the complement pathway in preeclampsia.

Lectin pathway proteins of the complement system in normotensive pregnancy and pre-eclampsia

PROBLEM

The lectin pathway of the complement system may be involved in the pathogenesis of pre-eclampsia. We aimed to investigate changes in serum concentrations of a broad range of lectin pathway proteins during normal pregnancy and their association with pre-eclampsia, placental infarctions and intrauterine growth restriction (IUGR).

METHOD OF STUDY

We included 51 women with normotensive pregnancies and 54 women with pregnancies complicated by pre-eclampsia. Blood samples were obtained at gestational weeks 16, 33, 37, and after delivery for the normotensive pregnant women and before and after delivery for women with pre-eclampsia. Mannose-binding lectin (MBL), H- and M-ficolin, collectin liver-1 (CL-L1), MBL-associated serine protease (MASP)-1, MASP-2 and MASP-3 and MBL-associated proteins of 19 (MAp19) and 44 (MAp44) kDa were analysed. Clinical information was obtained from medical records. The placentae were examined by two experienced perinatal pathologists.

RESULTS

Lectin pathway protein concentrations generally increased during normal pregnancy and decreased after delivery in both normotensive pregnant women and women with pre-eclampsia. Exceptions were MASP-3 which increased after delivery in both groups (P < 0.0001) and H-ficolin which increased after delivery in pre-eclampsia (P < 0.0001). H-ficolin (P < 0.0001), M-ficolin (P = 0.005) and MASP-3 (P = 0.03) concentrations were lower in women with pre-eclampsia than in normotensive pregnant women. Low MASP-3 concentrations were associated with placental infarction (P = 0.03) and IUGR (P = 0.04). Low H-ficolin concentrations were associated with IUGR (P < 0.01).

CONCLUSION

In general, lectin pathway protein serum concentrations increased during normal pregnancy. H-ficolin and MASP-3 may be involved in the pathophysiology of pre-eclampsia and IUGR and could be potential future pre-eclampsia biomarkers.

The Immunogenetic Conundrum of Preeclampsia

Pregnancy is an immunological challenge to the mother. The fetal tissues including the placenta must be protected from activation of the maternal immune system. On the other hand, the placental tissue sheds into the maternal circulation and must be adequately identified and phagocytized by the maternal immune system. During a healthy pregnancy, numerous immunosuppressive processes take place that allow the allograft fetus to thrive under exposure to humoral and cellular components of the maternal immune system. Breakdown of immune tolerance may result in sterile inflammation and cause adverse pregnancy outcomes such as preeclampsia, a vascular disease of the pregnancy with unpredictable course and symptoms from several organs. Immunological incompatibility between mother and fetus is strongly indicated in preeclampsia. Recently, genetic factors linking immunological pathways to predisposition to preeclampsia have been identified. In this mini-review genetic variation in immunological factors are discussed in the context of preeclampsia. Specifically, we explore immunogenetic and immunomodulary mechanisms contributing to loss of tolerance, inflammation, and autoimmunity in preeclampsia.

ELABELA plasma concentrations are increased in women with late-onset preeclampsia

Objective: ELABELA is a newly discovered peptide hormone that appears to be implicated in the mechanisms leading to preeclampsia, independently of angiogenic factors. The aim of the current study was to investigate whether women with early- or late-onset preeclampsia have altered ELABELA plasma concentrations compared to gestational-age-matched normal pregnant women.Methods: This retrospective cross-sectional study focused on the maternal plasma samples collected from 232 women with a singleton pregnancy who were allocated into the following groups: (1) early-onset preeclampsia (<34 weeks of gestation, N = 56); (2) late-onset preeclampsia (≥34 weeks of gestation, N = 57); and (3) gestational-age-matched controls with a normal pregnancy [(<34 weeks of gestation, N = 59); (≥34 weeks of gestation, N = 60)]. ELABELA plasma concentrations were determined using a validated enzyme immunoassay.Results: (1) ELABELA plasma concentrations are higher in patients with late-onset preeclampsia compared with those from gestational-age-matched controls with a normal pregnancy [median: 7.99 ng/mL (IQR, 5.3-13.95 ng/mL) versus median: 4.17 ng/mL (IQR, 3-11.19 ng/mL), p =.001]; (2) ELABELA plasma concentrations in patients with early-onset preeclampsia do not differ from those of normal pregnant women [median: 6.09 ng/mL (IQR, 2.8-10.66 ng/mL) versus median: 4.02 ng/mL (IQR, 3.26-7.49), p = .32]; and (3) ELABELA plasma concentrations are higher in patients with late-onset preeclampsia compared to those with early-onset preeclampsia [median: 7.99 ng/mL (IQR, 5.3-13.95 ng/mL) versus median: 6.09 ng/mL (IQR, 2.8-10.66 ng/mL), p = .01].Conclusion: ELABELA plasma concentrations are higher in patients with late-onset preeclampsia than in those with a normal pregnancy. However, women with early-onset preeclampsia have similar ELABELA plasma concentrations to those with a normal pregnancy. These findings provide insight into the ELABELA axis during the human syndrome of preeclampsia. In addition, these data support the concept that different pathophysiologic mechanisms are implicated in early- and late-onset preeclampsia.

Placental inflammation in pre-eclampsia by Nod-like receptor protein (NLRP)3 inflammasome activation in trophoblasts

Pre-eclampsia is associated with increased levels of cholesterol and uric acid and an inflamed placenta expressing danger-sensing pattern recognition receptors (PRRs). Crystalline cholesterol and uric acid activate the PRR Nod-like receptor protein (NLRP)3 inflammasome to release interleukin (IL)-1β and result in vigorous inflammation. We aimed to characterize crystal-induced NLRP3 activation in placental inflammation and examine its role in pre-eclampsia. We confirmed that serum total cholesterol and uric acid were elevated in pre-eclamptic compared to healthy pregnancies and correlated positively to high sensitivity C-reactive protein (hsCRP) and the pre-eclampsia marker soluble fms-like tyrosine kinase-1 (sFlt-1). The NLRP3 inflammasome pathway components (NLRP3, caspase-1, IL-1β) and priming factors [complement component 5a (C5a) and terminal complement complex (TCC)] were co-expressed by the syncytiotrophoblast layer which covers the placental surface and interacts with maternal blood. The expression of IL-1β and TCC was increased significantly and C5a-positive regions in the syncytiotrophoblast layer appeared more frequent in pre-eclamptic compared to normal pregnancies. In-vitro activation of placental explants and trophoblasts confirmed NLRP3 inflammasome pathway functionality by complement-primed crystal-induced release of IL-1β. This study confirms crystal-induced NLRP3 inflammasome activation located at the syncytiotrophoblast layer as a mechanism of placental inflammation and suggests contribution of enhanced NLRP3 activation to the harmful placental inflammation in pre-eclampsia.

Celecoxib restores angiogenic factor expression at the maternal-fetal interface in the BPH/5 mouse model of preeclampsia

Preeclampsia (PE), a hypertensive disease of pregnancy, is a leading cause of fetal and maternal morbidity/mortality. Early angiogenic and inflammatory disturbances within the placenta are thought to underlie the development of the maternal PE syndrome and poor pregnancy outcomes. However, the exact etiology remains largely unknown. Here, we use the BPH/5 mouse model of PE to elucidate the way in which inflammation early in pregnancy contributes to abnormal expression of angiogenic factors at the maternal-fetal interface. We have previously described improvement in maternal hypertension and fetal growth restriction in this model after treatment with the anti-inflammatory cyclooxygenase-2 (Cox2) specific inhibitor celecoxib. To further characterize the mechanisms by which celecoxib improves poor pregnancy outcomes in BPH/5 mice, we determined expression of angiogenic factors and complement pathway components after celecoxib. In BPH/5 implantation sites there was increased hypoxia inducible factor-1α ( Hif1α), heme oxygenase-1 ( Ho-1), and stem cell factor ( Scf) mRNA concomitant with elevated prostaglandin synthase 2 ( Ptgs2), encoding Cox2, and elevated VEGF protein. Angiopoietin 1 ( Ang1), tunica interna endothelial cell kinase-2 receptor ( Tie2), complement factor 3 ( C3), and complement factor B ( CfB) were increased in midgestation BPH/5 placentae. Whereas BPH/5 expression levels of VEGF, Ang1, and Tie2 normalized after celecoxib, placental C3 and CfB mRNA remained unchanged. However, celecoxib did reduce the pregnancy-specific circulating soluble fms-like tyrosine kinase-1 (sFlt-1) rise in BPH/5 mice at midgestation. These data show that elevated Cox2 during implantation contributes to placental angiogenic factor imbalances in the BPH/5 mouse model of PE.

Angiogenic factor imbalance precedes complement deposition in placentae of the BPH/5 model of preeclampsia

Preeclampsia (PE), a hypertensive disorder of pregnancy, is a leading cause of maternal and fetal morbidity and mortality. Although the etiology is unknown, PE is thought to be caused by defective implantation and decidualization in pregnancy. Pregnant blood pressure high (BPH)/5 mice spontaneously develop placentopathies and maternal features of human PE. We hypothesized that BPH/5 implantation sites have transcriptomic alterations. Next-generation RNA sequencing of implantation sites at peak decidualization, embryonic day (E)7.5, revealed complement gene up-regulation in BPH/5 vs. controls. In BPH/5, expression of complement factor 3 was increased around the decidual vasculature of E7.5 implantation sites and in the trophoblast giant cell layer of E10.5 placentae. Altered expression of VEGF pathway genes in E5.5 BPH/5 implantation sites preceded complement dysregulation, which correlated with abnormal vasculature and increased placental growth factor mRNA and VEGF₁₆₄ expression at E7.5. By E10.5, proangiogenic genes were down-regulated, whereas antiangiogenic sFlt-1 was up-regulated in BPH/5 placentae. We found that early local misexpression of VEGF genes and abnormal decidual vasculature preceded sFlt-1 overexpression and increased complement deposition in BPH/5 placentae. Our findings suggest that abnormal decidual angiogenesis precedes complement activation, which in turn contributes to the aberrant trophoblast invasion and poor placentation that underlie PE.-Sones, J. L., Merriam, A. A., Seffens, A., Brown-Grant, D.-A., Butler, S. D., Zhao, A. M., Xu, X., Shawber, C. J., Grenier, J. K., Douglas, N. C. Angiogenic factor imbalance precedes complement deposition in placentae of the BPH/5 model of preeclampsia.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea

Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted in the successful introduction of the complement inhibitor eculizumab into clinical practice. In other TMAs, although complement activation may be seen, its role in the pathogenesis remains to be confirmed by an interventional trial. Although many case reports in TMAs other than complement-mediated aHUS hint at efficacy, publication bias, concurrent therapies and in some cases the self-limiting nature of disease make broader interpretation difficult. In this article, we will review the evidence for the role of complement inhibition in complement-mediated aHUS and other TMAs.

Maternal plasma-soluble ST2 concentrations are elevated prior to the development of early and late onset preeclampsia - a longitudinal study

OBJECTIVE

The objectives of this study were to determine (1) the longitudinal profile of plasma soluble ST2 (sST2) concentrations in patients with preeclampsia and those with uncomplicated pregnancies; (2) whether the changes in sST2 occur prior to the diagnosis of preeclampsia; and (3) the longitudinal sST2 profile of women with early or late preeclampsia.

MATERIALS AND METHODS

This longitudinal nested case-control study included singleton pregnancies in the following groups: (1) uncomplicated pregnancies (n = 160); and (2) those complicated by early (<34 weeks, n = 9) and late (≥34 weeks, n = 31) preeclampsia. sST2 concentrations were determined by enzyme-linked immunosorbent assays. Mixed-effects models were used for the longitudinal analysis.

RESULTS

(1) Plasma sST2 concentration profiles across gestation differed significantly among cases and controls (p < 0.0001); (2) women with early preeclampsia had higher mean sST2 concentrations than controls at >22 weeks of gestation; cases with late preeclampsia had higher mean concentrations at >33 weeks of gestation (both p < 0.05); and (3) these changes started approximately 6 weeks prior to clinical diagnosis.

CONCLUSIONS

Maternal plasma sST2 concentrations are elevated 6 weeks prior to the clinical diagnosis of preeclampsia. An increase in the maternal plasma concentration of sST2 may contribute to an exaggerated intravascular inflammatory response and/or the Th1/Th2 imbalance in some cases.