Circulating cell-derived microparticles in severe preeclampsia and in fetal growth restriction

The pathogenesis of obstetric APS: a 2023 update

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the persistent presence of antibodies directed against phospholipids and phospholipid-binding proteins that are associated with thrombosis and pregnancy-related morbidity. The latter includes fetal deaths, premature birth and maternal complications. In the early 1990s, a distinct set of autoantibodies, termed collectively antiphospholipid antibodies (aPL), were identified as the causative agents of this disorder. Subsequently histological analyses of the placenta from APS pregnancies revealed various abnormalities, including inflammation at maternal-fetal interface and poor placentation manifested by reduced trophoblast invasion and limited uterine spiral artery remodeling. Further preclinical investigations identified the molecular targets of aPL and the downstream intracellular pathways of key placental cell types. While these discoveries suggest potential therapeutics for this disorder, definitive clinical trials have not been completed. This concise review focuses on the recent developments in the field of basic and translational research pursuing novel mechanisms underlying obstetric APS.

Pravastatin reduces plasma levels of extracellular vesicles in pregnancies at high risk of term preeclampsia

Introduction: Elevated plasma levels of extracellular vesicles have been associated with impaired placentation, angiogenesis imbalance, intravascular inflammation, and endothelial dysfunction in women with preeclampsia, thus suggesting that circulating vesicles may be a good therapeutic target for the treatment of the disease. Recently, statins have been considered a potential treatment for the prevention of preeclampsia because of their pleiotropic effects, including the improvement of endothelial dysfunction and inhibition of inflammatory responses. However, the effects of these drugs on circulating vesicles concentration in women at risk of preeclampsia have not been established. Herein, we aimed to assess the effects of pravastatin on circulating extracellular vesicle generation in women at high risk of term preeclampsia. Methods: In a sample of 68 singleton pregnant women participating in the multicenter, double-blind, placebo-controlled STATIN trial (Nº EducraCT 2016-005206-19 ISRCTN), 35 women received a placebo and 33 women received a 20 mg/day dose of pravastatin for approximately 3 weeks (from 35 to 37 weeks of gestation until delivery). Large extracellular vesicles were characterized and quantified by flow cytometry using annexin V and cell-specific antibodies directed against platelet, endothelial, leukocyte, and syncytiotrophoblast cell surface markers. Results: In women who received the placebo, a significant increase in the plasma levels of large extracellular vesicles from platelets (34%, p < 0.01), leukocytes (33%, p < 0.01), monocytes (60%, p < 0.01), endothelial cells (40%, p < 0.05), and syncytiotrophoblast cells (22%, p < 0.05) were observed. However, treatment with pravastatin significantly reduced the plasma levels of large extracellular vesicles from platelets (42%, p < 0.001), leukocytes (25%, p < 0.001), monocytes (61%, p < 0.001), endothelial cells (69%, p < 0.001), activated endothelial cells (55%, p < 0.001), and syncytiotrophoblast cells (44%, p < 0.001). Discussion: These results indicate that pravastatin reduces the levels of activated cell-derived membrane vesicles from the maternal vasculature, blood, and placental syncytiotrophoblast of women at high risk of term preeclampsia, suggesting that this statin may be beneficial in reducing endothelial dysfunction and pro-inflammatory and pro-coagulatory state characteristics of the disease.

Expression of placental glycans and its role in regulating peripheral blood NK cells during preeclampsia: a perspective

Preeclampsia is a pregnancy-related multisystem disorder characterized by altered trophoblast invasion, oxidative stress, exacerbation of systemic inflammatory response, and endothelial damage. The pathogenesis includes hypertension and mild-to-severe microangiopathy in the kidney, liver, placenta, and brain. The main mechanisms involved in its pathogenesis have been proposed to limit trophoblast invasion and increase the release of extracellular vesicles from the syncytiotrophoblast into the maternal circulation, exacerbating the systemic inflammatory response. The placenta expresses glycans as part of its development and maternal immune tolerance during gestation. The expression profile of glycans at the maternal-fetal interface may play a fundamental role in physiological pregnancy changes and disorders such as preeclampsia. It is unclear whether glycans and their lectin-like receptors are involved in the mechanisms of maternal-fetal recognition by immune cells during pregnancy homeostasis. The expression profile of glycans appears to be altered in hypertensive disorders of pregnancy, which could lead to alterations in the placental microenvironment and vascular endothelium in pregnancy conditions such as preeclampsia. Glycans with immunomodulatory properties at the maternal-fetal interface are altered in early-onset severe preeclampsia, implying that innate immune system components, such as NK cells, exacerbate the systemic inflammatory response observed in preeclampsia. In this article, we discuss the evidence for the role of glycans in gestational physiology and the perspective of glycobiology on the pathophysiology of hypertensive disorders in gestation.

First Trimester Mean Platelet Volume, Neutrophil to Lymphocyte Ratio, and Platelet to Lymphocyte Ratio Values Are Useful Markers for Predicting Preeclampsia

Background: Preeclampsia complicates 2% to 8% of all pregnancies. Systemic inflammatory response (SIR) markers are widely used in the diagnosis of many inflammatory diseases and in the prediction of complicated pregnancies. This study examined the diagnostic value of SIR markers during the first trimester of pregnancy to predict preeclampsia development.

Methods: This retrospective case-control study was conducted from January 2020 to May 2020. We included 94 patients diagnosed with mild preeclampsia, 107 patients diagnosed with severe preeclampsia, and 100 normotensive pregnant patients as controls. We obtained the first trimester (6 to 14 weeks) complete blood cell counts for all patients. We used a receiver operating characteristic curve to evaluate the cutoff, sensitivity, and specificity values.

Results: First trimester mean platelet volume (MPV), neutrophil to lymphocyte ratio (NLR), and platelet to lymphocyte ratio (PLR) values were significantly higher in patients who developed preeclampsia in later pregnancy weeks. The optimal cutoff value for MPV was 10.65 fL, with a sensitivity of 63.7% and a specificity of 65.0%. The best predictor for preeclampsia was NLR at an optimal cutoff value of 4.12, with a sensitivity of 82.1% and specificity of 62.0%. At a cutoff value of 131.8, PLR predicted preeclampsia with a sensitivity rate of 65.0% and a specificity rate of 60.2%.

Conclusion: The results of this study suggest that first trimester MPV, NLR, and PLR values are clinically useful markers in the prediction of preeclampsia. The increased first trimester values of MPV, NLR, and PLR also indicate that inflammation may play a crucial role in preeclampsia pathogenesis.

Extracellular Vesicles and Preeclampsia: Current Knowledge and Future Research Directions

Preeclampsia (PE) is associated with long-term morbidity in mothers and lifelong morbidities for their children, ranging from cerebral palsy and cognitive delay in preterm infants, to hypertension, diabetes and obesity in adolescents and young adults. There are several processes that are critical for development of materno-fetal exchange, including establishing adequate perfusion of the placenta by maternal blood, and the formation of the placental villous vascular tree. Recent studies provide persuasive evidence that placenta-derived extracellular vesicles (EVs) represent a significant intercellular communication pathway, and that they may play an important role in placental and endothelial cell (both fetal and maternal) function. These functions are known to be altered in PE. EVs can carry and transport a wide range of bioactive molescules that have potential to be used as biomarkers and therapeutic delivery tools for PE. EV content is often parent cell specific, thus providing an insight or "thumbprint" of the intracellular environment of the originating cell (e.g., human placenta). EV have been identified in plasma under both normal and pathological conditions, including PE. The concentration of EVs and their content in plasma has been reported to increase in association with disease severity and/or progression. Placenta-derived EVs have been identified in maternal plasma during normal pregnancy and PE pregnancies. They contain placenta-specific proteins and miRNAs and, as such, may be differentiated from maternally-derived EVs. The aim of this review, thus, is to describe the potential roles of EVs in preecmpatic pregnancies, focussing on EVs secreted from placental cells. The biogenesis, specificity of placental EVs, and methods used to characterise EVs in the context of PE pregnancies will be also discussed.

Increased circulating microparticles in women with preeclampsia

INTRODUCTION

Preeclampsia (PE) is associated with hypercoagulability, endothelial dysfunction and inflammation, which generate microparticles (MPs). Therefore, MPs may be important for PE.

METHODS

We established a verified MP measurement procedure to detect MPs in nonpregnant women (n = 25), healthy pregnant women (n = 29) and PE women (n = 73) and compared their MP levels.

RESULTS

Microparticles prepared from platelets (PMPs), endothelial cells (EMPs) and leucocytes (LMPs) were confirmed by transmission electron microscopy and were analysed by our established flow cytofluorimetric approach, which showed good specificity for determining the cell origin and level of MPs. The levels of total MPs (tMPs) and PMPs in the healthy pregnant group were significantly higher than those in the nonpregnant group (158.78 vs 93.00 and 45.04 vs 17.41, P = .004 and P = .007, respectively) but were not significantly different from those of the PE group. However, EMPs and LMPs were significantly higher in the PE group than in the healthy pregnant group (14.62 vs 11.48 and 8.94 vs 5.03, P = .015 and P < .001, respectively). Furthermore, the area under the receiver operating characteristic curves (AUC) for EMPs, LMPs and the combined sum of EMPs and LMPs were 0.661, 0.746 and 0.718, respectively (P < . 05); at their optimal cut-off values, the sensitivities were 50.68%, 87.67% and 46.58%, respectively, and the specificities were 80.77%, 58.33% and 95.65%, respectively.

CONCLUSION

Determining the MP level, especially that of EMPs and LMPs, by a specificity-verified method may reflect the endothelial dysfunction and inflammation involved in PE pathogenesis.

Circulating microparticles: challenges and perspectives of flow cytometric assessment

Circulating blood microparticles are likely to play a significant role as messengers of biological information. Their accurate quantification and characterisation is challenging and needs to be carefully designed with preferable usage of fresh minimally-processed blood samples. Utilisation of flow cytometers specifically designed for analysis of small-size particles is likely to provide considerable methodological advantages and should be the preferable option. This viewpoint manuscript provides a critical summary of the key methodological aspects of microparticle analysis.

Note: The review process for this viewpoint article was fully handled by Christian Weber, Editor in Chief.

Preeclampsia and Extracellular Vesicles

Preeclampsia is a hypertensive pregnancy disorder characterized by development of hypertension and proteinuria after 20 weeks of gestation that remains a leading cause of maternal and neonatal morbidity and mortality. While preeclampsia is believed to result from complex interactions between maternal and placental factors, the proximate pathophysiology of this syndrome remains elusive. Cell-to-cell communication is a critical signaling mechanism for feto-placental development in normal pregnancies. One mechanism of cellular communication relates to activated cell-derived sealed membrane vesicles called extracellular vesicles (EVs). The concentrations and contents of EVs in biological fluids depend upon their cells of origin and the stimuli which trigger their production. Research on EVs in preeclampsia has focused on EVs derived from the maternal vasculature (endothelium, vascular smooth muscle) and blood (erythrocytes, leukocytes, and platelets), as well as placental syncytiotrophoblasts. Changes in the concentrations and contents of these EVs may contribute to the pathophysiology of preeclampsia by accentuating the pro-inflammatory and pro-coagulatory states of pregnancy. This review focuses on possible interactions among placental- and maternal-derived EVs and their contents in the initiation and progression of the pathogenesis of preeclampsia. Understanding the contributions of EVs in the pathogenesis of preeclampsia may facilitate their use as diagnostic and prognostic biomarkers.

PLAC1 is involved in human trophoblast syncytialization

Placenta specific protein 1 (PLAC1) is thought to be important for murine and human placentation because of its abundant expression in placenta; however, the trophoblast subtypes that express PLAC1 at the fetomaternal interface and the major role of PLAC1 in placentation are still unclear. This study investigated the expression pattern of PLAC1 at the human fetomaternal interface and its involvement in trophoblast syncytialization. Localization of PLAC1 at the fetomaternal interface was studied using in situ hybridization (ISH) and immunohistochemistry (IHC) assays. Real time RT-PCR and Western Blot were employed to exhibit the expression pattern of PLAC1 during human spontaneous syncytialization of term primary cytotrophoblast cells (CTBs). Spontaneous syncytialization of a primary term CTBs model transfected with siRNA specific to PLAC1 was used to investigate the role of PLAC1 during human trophoblast syncytialization. The results showed that PLAC1 was mainly expressed in the human villous syncytiotrophoblast (STB) layer throughout gestation, and the expression level of PLAC1 was significantly elevated during human trophoblast syncytialization. Down-regulation of PLAC1 via specific PLAC1 siRNA transfection attenuated spontaneous syncytialization of primary term CTBs (p<0.05) as indicated by cell fusion index and the expression patterns of the corresponding markers. These data demonstrate the facilitative role of PLAC1 in normal human trophoblast syncytialization.

Influence of peripheral blood microparticles of pregnant women with preeclampsia on the phenotype of monocytes

Platelet- and endothelial-derived microparticles influence the phenotype of peripheral blood leukocytes and induce production of proinflammatory cytokines. The influence of blood plasma microparticles of pregnant women on the surface receptor expression on intact or activated monocytes is still unexplored. This study was carried out to test the hypothesis that peripheral blood microparticles of women with normal pregnancy and women with preeclampsia have different influence on the expression of surface molecules on monocytes. The objective of the study was to evaluate the influence of blood plasma microparticles of pregnant women on the phenotypic properties of intact and activated THP-1 monocytes. Microparticles were isolated from peripheral blood samples of nonpregnant women, healthy pregnant women, and women with preeclampsia. THP-1 cell line was used as a model of monocytes. Microparticles of nonpregnant women decreased CD18, CD49d, and CD54 expressions and increased CD11c, CD31, CD47, and vascular endothelial growth factor receptor 2 expressions. Microparticles of healthy pregnant women increased CD18, CD54, and integrin β7 expressions and decreased CD11a and CD29 expressions. Microparticles of women with preeclampsia decreased CD18 expression on tumor necrosis factor α (TNF-α)-activated ТНР-1 cells. Microparticles of nonpregnant women, women with normal pregnancy, and pregnant women with preeclampsia decreased CD181 expression on intact and TNF-α-activated THP-1 cells. Therefore, blood plasma microparticles of women with normal pregnancy and women with preeclampsia have different influences on the expression of surface molecules on THP-1 monocytes.

Association of microparticles and preeclampsia

Preeclampsia (PE) is a syndrome characterized by poor placentation and endothelial dysfunction. The diagnosis for this syndrome is based in hypertension and proteinuria presented after the 20th week of pregnancy. Despite intensive research, PE is still one of the leading causes of maternal mortality, although reliable screening tests or effective treatments of this disease have yet to be proposed. Microparticles (MPs) are small vesicles released after cell activation or apoptosis, which contain membrane proteins that are characteristic of the original parent cell. MPs have been proven to play key role in thrombosis, inflammation, and angiogenesis, as well as to mediate cell-cell communication by transferring mRNAs and microRNA from the cell of origin to target cells. Placenta-derived syncytiotrophoblast MPs are one of the most increased MPs during PE and may play an important role in the pathogenesis of this syndrome. Therefore, a better overall understanding of the role of MPs in PE may be useful for new clinical diagnoses and therapeutic approaches.

Role of microparticles in recurrent miscarriages and other adverse pregnancies: a review

The multiple functions attributed to microparticles (MPs) include blood coagulation, inflammation, tumorigenesis, angiogenesis, immunomodulatory functions and intercellular cross talk. These have drawn considerable interest during the last few years. The prothrombotic nature of MPs has linked them with almost all groups of thrombotic disorders including recurrent miscarriage (RM) and other abnormal pregnancy outcomes. Two authors (SS and RP) conducted a search independently on the computerized databases MEDLINE and EMBASE using relevant key words. Contradictory reports were observed on the association of MPs with RM. While most of the reports showed increased prevalence of MPs, both platelet and endothelial cell derived, in RM, some did not show any association. Almost all the reports showed a strong association of MPs with preeclampsia (PE), while the association with other adverse pregnancy conditions was not very conclusive. It may be concluded that MPs by themselves may result in adverse conditions or that they may be additive factors to an already existing prothrombotic state due to acquired or genetic thrombophilia or some unknown thrombophilic condition, besides the pre-existing hypercoagulable status of pregnancy.