Four Pathways Involving Innate Immunity in the Pathogenesis of Preeclampsia

Preeclamptic Placental CD19+ B Cells Are Causal to Hypertension During Pregnancy

BACKGROUND

Patients with preeclampsia exhibit hypertension and chronic inflammation characterized by CD (cluster determinant) 4+T cells, B cells secreting AT1-AA (agonistic autoantibody against the angiotensin II type 1 receptor), inflammatory cytokines, and complement activation. Importantly, a history of COVID-19 during pregnancy is associated with an increased incidence of a preeclampsia-like phenotype and is partly mediated by CD4+T cells. We recently showed pregnant patients with a history of COVID-19 with or without preeclampsia produce AT1-AA, indicating the importance of B lymphocytes in the progression of preeclampsia and possibly of COVID-19. Therefore, we hypothesize that B cells from patients with preeclampsia with or without COVID-19 history induce the preeclampsia phenotype through AT1-AA.

METHODS

Placental B cells were isolated from normal pregnant, patients with preeclampsia, normotensive COVID-19 history, or preeclampsia COVID-19 history at delivery. Then, 3×105 B cells were transferred intraperitoneally into pregnant athymic rats at gestational day 12. On gestational day 18, carotid catheters were inserted. On gestational day 19, mean arterial pressure was measured, and tissues were collected.

RESULTS

Preeclampsia B-cell recipients had significantly increased mean arterial pressure, AT1-AA, inflammatory cytokines, and complement activation compared with normal pregnant B-cell recipients. Recipients of B cells with COVID-19 history had markers of inflammation and hypertension but not to the level of significance as recipients of preeclampsia B cells. Inhibition of AT1-AA attenuated the hypertension that occurred in response to preeclampsia or preeclampsia B cells with COVID-19 history.

CONCLUSIONS

This study demonstrates the important role of B cells in contributing to hypertension and chronic inflammation during preeclampsia with or without COVID-19 history through secretion of AT1-AA.

Trained innate immunity as a potential link between preeclampsia and future cardiovascular disease

Preeclampsia (PE) is a complex pregnancy syndrome characterized by hypertension with or without proteinuria, affecting 2-6% of pregnancies globally. PE is characterized by excessive release of damage-associated molecular patterns (DAMPs) into the maternal circulation. This DAMP-rich milieu acts on innate immune cells, inducing a proinflammatory state characterized by elevated cytokines such as IL-1β and IL-18. This proinflammatory state in the mother and placenta results in the endothelial dysfunction strongly associated with cardiovascular disorders. While the immediate maternal and fetal risks of PE are well-documented, accumulating evidence indicates that PE also confers long-term cardiovascular risks to the mother, including hypertension, coronary heart disease, stroke, and heart failure. The underlying mechanisms connecting PE to these chronic cardiovascular conditions remain unclear. This article explores the potential role of trained innate immunity (TRIM) as a mechanistic link between PE and increased long-term cardiovascular risk. We propose that the persistent exposure to DAMPs during PE may epigenetically reprogram maternal innate immune cells and their progenitors, leading to TRIM. This reprogramming enhances the inflammatory response to subsequent stimuli, potentially contributing to endothelial dysfunction and chronic inflammation that predispose women to cardiovascular diseases later in life. Understanding the role of TRIM in PE could provide novel insights into the pathophysiology of PE-related cardiovascular complications and identify potential targets for therapeutic intervention. Further research is warranted to investigate the epigenetic and metabolic alterations in innate immune cells induced by PE and to determine how these changes may influence long-term maternal cardiovascular health.

Mononuclear Cells Negatively Regulate Endothelial Ca2+ Signaling

Endothelial Ca2+ signaling has important roles to play in maintaining pregnancy associated vasodilation in the utero-placenta. Inflammatory cytokines, often elevated in vascular complications of pregnancy, negatively regulate ATP-stimulated endothelial Ca2+ signaling and associated nitric oxide production. However, the role of direct engagement of immune cells on endothelial Ca2+ signaling and therefore endothelial function is unclear. To model immune-endothelial interactions, herein, we evaluate the effects of peripheral blood mononuclear cells (PBMCs) in short-term interaction with human umbilical vein endothelial cells (HUVECs) on agonist-stimulated Ca2+ signaling in HUVECs. We find that mononuclear cells (10:1 and 25:1 mononuclear: HUVEC) cause decreased ATP-stimulated Ca2+ signaling; worsened by activated mononuclear cells possibly due to increased cytokine secretion. Additionally, monocytes, natural killers, and T-cells cause decrease in ATP-stimulated Ca2+ signaling using THP-1 (monocyte), NKL (natural killer cells), and Jurkat (T-cell) cell lines, respectively. PBMCs with Golgi-restricted protein transport prior to interaction with endothelial cells display rescue in Ca2+ signaling, strongly suggesting that secreted proteins from PBMCs mediate changes in HUVEC Ca2+ signaling. We propose that endothelial cells from normal pregnancy interacting with PBMCs may model preeclamptic endothelial-immune interaction and resultant endothelial dysfunction.

Circulating miRNAs as Epigenetic Mediators of Periodontitis and Preeclampsia Association

Objective

Periodontal disease has been associated with pregnancy complications including preeclampsia. This bioinformatic study is aimed at investigating the possible role of circulating microRNAs (miRNAs) as mediators of the association between maternal periodontal disease and preeclampsia.

Methods

Peripheral blood miRNA profiles of periodontitis and controls were sought from Gene Expression Omnibus (GEO), and differential expression analysis was performed. Experimentally validated circulating miRNAs associated with preeclampsia were determined from the Human MicroRNA Disease Database (HMDD v3.0). Venn diagrams were drawn to identify shared circulating differential miRNAs (DEmiRNAs). Significantly enriched target genes, KEGG pathways, and Gene Ontology (GO) terms for the set of shared DEmiRNA were predicted using miRNA enrichment analysis and annotation tool (miEAA v 2.0). Additionally, the shared DEmiRNA-enriched target genes were analyzed for enriched WikiPathways, BioCarta metabolic pathways, and tissue proteins in the human proteome map.

Results

Among 183 circulating DEmiRNA in periodontitis and 60 experimentally validated miRNA in preeclampsia, 9 shared DEmiRNA were identified. The top among 32 overrepresented target genes included MAFB, PSAP, and CDK5RAP2, top among 14 enriched KEGG pathways were renin-angiotensin system and graft-versus-host disease, and that among enriched 44 GO profiles included “positive regulation of epidermal growth factor-activated receptor activity” and “sequestering of calcium ion.” In the overrepresented target gene set, among 10 enriched WikiPathways, the top included “NAD metabolism, sirtuins, and aging” and “regulation of Wnt/B-catenin signaling by small molecule compounds” and PPAR-related mechanisms was top among 13 enriched BioCarta metabolic pathways.

Conclusion

A circulating 9-DEmiRNA set was significantly linked to both periodontitis and preeclampsia. Enrichment analysis identified specific genes, pathways, and functional mechanisms, which may be epigenetically altered and thereby mediate the biological association of periodontitis and preeclampsia.

Neutrophil count is a useful marker to predict the severity of preeclampsia

BACKGROUND

At present, pre-eclampsia is a growing concern and still a diagnostic challenge for obstetricians.

AIMS

This study aimed to evaluate whether the relationship of second trimester of pregnancy neutrophil count differed among pregnancies with mild preeclampsia, severe preeclampsia, and healthy status and explore whether or not neutrophil count in the second trimester of pregnancy would be useful as new predictors of subsequent preeclampsia.

PATIENTS AND METHODS

This study involved 933 pregnancies from 1 January 2018 to 30 January 2021, comprising 396 healthy pregnancies, 222 pregnancies with mild preeclampsia, and 315 pregnancies with severe preeclampsia. The relationship between preeclampsia and neutrophil count was analyzed by multiple logistic regression. In addition, maternal placental tissues of three groups were immunohistochemically stained for myeloperoxidase (MPO).

RESULTS

Neutrophil count was significantly higher in pregnancies with preeclampsia (including pregnancies with mild and severe preeclampsia) than that in healthy pregnancies. The neutrophil count level was prominently higher in patients with severe preeclampsia compared with those with mild preeclampsia (p < .001). The neutrophil count level was significantly positively associated with preeclampsia after adjusting for gestational week at time of blood sampling, BMI, and age (β:1.23; 95%CI:1.09-1.36; p < .0001). In addition, MPO expressions of placental tissues in preeclamptic groups were significantly increased than these in healthy pregnant controls (p < .05).

CONCLUSIONS

Increased neutrophil count in the second trimester of pregnancy was significantly positively associated with preeclampsia. Hence, neutrophil count plays a role in predicting the severity of preeclampsia. At the same time, it may be an independent predictor of subsequent preeclampsia.Abbreviations: BMI: body mass index; MPO: myeloperoxidase.

Exosomal mRNA and lncRNA profiles in cord blood of preeclampsia patients

BACKGROUND

Exosomes are endosome-derived membrane vesicles that contain numerous RNAs and allow intercellular communication. The roles of mRNAs and lncRNAs from umbilical cord blood exosomes in the development of preeclampsia (PE) remain unclear.

METHODS

In the study, microarray technology was used to construct the differential mRNA and lncRNA expression profiles in umbilical cord blood exosomes between PE patients and normal controls.

RESULTS

Totally, 120 differentially expressed mRNAs and 248 differentially expressed lncRNAs were identified. Pathway analysis showed that the differentially expressed mRNAs were related to glycolysis/gluconeogenesis, PI3K-Akt signaling pathway and JAK-STAT signaling pathway, which are critical in PE development. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted for the differential lncRNA-associated mRNAs. We found several significantly enriched pathways were closely associated with metabolic process, cell proliferation, differentiation, and apoptosis. Moreover, the constructed pathway network revealed key pathways in PE, including apoptosis and TGF-beta signaling pathway. Further analysis of lncRNA/miRNA interactions showed that most of the lncRNAs had miRNA binding sites, and some of them were associated with PE.

CONCLUSIONS

The study highlights the importance of exosomal mRNAs and lncRNAs in umbilical cord blood, and provides new insight into the development of PE.

Association Between TLR4 Gene Polymorphisms and Risk of Preeclampsia: Systematic Review and Meta-Analysis

BACKGROUND Toll-like receptor 4 (TLR4) plays a pivotal role in the innate immune response and is hyperactivated in preeclampsia (PE). Several researchers have published conflicting evidence for TLR4 rs4986790 and rs4986791 single nucleotide polymorphisms (SNPs) as risk factors for PE. The present meta-analysis was conducted to obtain a more definitive conclusion about the effects of these SNPs on PE susceptibility. MATERIAL AND METHODS To determine the correlation between rs4986790 and rs4986791 polymorphisms in the TLR4 gene and susceptibility to PE, the PubMed, Web of Science, EMBASE, Chinese National Knowledge Infrastructure, and Chinese WANFANG databases were searched for eligible articles. Statistical analysis was performed with STATA software, version 12.0. Pooled odds ratios with corresponding 95% confidence intervals (CIs) were extracted for assessment of correlation strength. RESULTS We identified 5 studies including 578 cases and 631 controls for the rs4986790 SNP and 4 studies including 469 cases and 457 controls for the rs4986791 SNP, mainly from a White population. The pooled analyses showed no statistical relationship between the polymorphisms rs4986790 and rs4986791 and PE susceptibility in 5 genetic models (all P>0.05). Moreover, the allelic and dominant gene models of rs4986790 and the allelic, heterozygous, and dominant gene models of rs4986791 had high heterogeneity. The sensitivity analysis explored potential sources of heterogeneity and confirmed the findings of this meta-analysis. CONCLUSIONS TLR4 rs4986790 and rs4986791 polymorphisms may not be implicated in PE susceptibility, primarily in a White population. More high-quality studies of genetic associations with PE are warranted.

Placental Microbial Colonization and Its Association With Pre-eclampsia

The existence and role of the microbiome in regulating physiological and pathophysiological conditions including metabolism, energy homeostasis, immune tolerance, behavior, obesity, diabetes, and cardiovascular-related diseases is of immense interest. It is now clear that the human placenta is not sterile, but rather colonized with microbes. The placental and vaginal microbiomes are distinct however, the placental microbiome is comparable with the oral microbiome, with a limited variation when compared with the gut microbiome. Pre-eclampsia (PE), a pregnancy-specific hypertensive disorder, remains the leading cause of maternal-fetal morbidity and mortality. This is largely due to the lack of a clear etiology of PE and consequently, diagnostic strategies, and treatment are sub-optimal. The present review focuses on the current understanding of the placental microbiome and its implication in the etiology of PE. It provides a perspective on the alteration of placental microbiome as a possible therapeutic approach in the prevention and management of PE.

Syndecan 4, galectin 2, and death receptor 3 (DR3) as novel proteins in pathophysiology of preeclampsia

INTRODUCTION

Preeclampsia has the highest rate of obstetric morbidity and mortality.

METHODS

We recruited 21 women with preeclampsia and 27 women with uncomplicated pregnancies. We used a quantitative protein macroarray that allowed for analysis of 40 proteins.

RESULTS

We found a statistically significant increase in the concentration of DR3, LIF and a significant decrease of VEGF, PlGF, syndecan-4 and galectin-2, in the plasma of women with preeclampsia.

CONCLUSIONS

There are no previous studies assessing syndecan 4, galectin 2, and DR3 concentrations in women with preeclampsia; Our results indicate these proteins are new factors that play important roles in the immunological pathomechanism of preeclampsia.

Deep targeted sequencing reveals the diversity of TRB-CDR3 repertoire in patients with preeclampsia

Preeclampsia (PE) is one of the major causes of maternal and perinatal mortality worldwide. This study aimed to determine the immunological characteristics of PE patients and normal pregnancy at the T cell receptor beta-chain (TRB) level by using high-throughput sequencing. High-throughput sequencing was performed to analyze the expression of TRB-CDR3 in circulating T cells. T cells were isolated from 36 healthy pregnant women, 24 patients with severe PE, and 18 patients with moderate PE. Rearranged mRNA sequences were assigned to their germline V, D, and J counterparts, and translated into proper amino acids by the IMGT database. In general, PE samples had more TRB-CDR3 reads and types than those of normal pregnant woman in the circulation, but the mean number of TRB-CDR3 reads and unique TRB-CDR3 reads in severe group was lower than that in the moderate group. In PE patients, the V7_9 and V20_1 gene loci were more prevalent than in healthy pregnant women. In addition, 4 kinds of TRB-CDR3 peptides were found to be highly relevant to the pathogenesis of PE. Of them, peptides matched to herpes simplex virus antigen-specific T cells were much lower in PE samples.

Exploration of the regulation and control mechanisms of miR-145 in trophoblast cell proliferation and invasion

Preeclampsia (PE) is the leading cause of maternal and fetal mortality and morbidity. Furthermore, recent studies have reported that miR-145 within the preeclamptic trophoblast debris may cause the high blood pressure via interacting with the maternal endothelium. The aim of the present study was to investigate the functions of miR-145 in PE. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to assess the expression of miR-145 and mucin (MUC1), respectively. TargetScan, miRBase and miRWalk were used to predict the targets of miR-145. Constructed miR-145 mimic plasmids were transfected into HTR-8/SVneo cells for further experiments, including an MTT assay for cell proliferation, Transwell assay for cell invasion and flow cytometry for cell apoptosis analysis. Additionally, the luciferase reporter gene system was employed for target verification. The results demonstrated that miR-145 is downregulated and MUC1 is upregulated in PE tissues and cells compared with normal placenta tissues and cells. The correlation analysis suggests that the expression of miR-145 is negatively correlated with MUC1. Meanwhile, increased proliferation, enhanced invasion and decreased apoptosis of HTR-8/SVneo cells was observed in miR-145 mimic groups compared with mimic control group. Also, the decreased luciferase activity in the miR-145 mimic group indicates that MUC1 may be a target of miR-145. In summary, the results of the present study suggest that miR-145 may serve key roles in the regulation of trophoblast cell proliferation and invasion by targeting MUC1.

Toll-like receptors signaling network in pre-eclampsia: An updated review

Toll-like receptors (TLRs) are innate immune cells receptors. They are expressed on leukocytes, epithelial cells, and more particularly on placental immune cells and chorion trophoblast. Upregulation of innate immune response occurs during normal pregnancy, but its excessive activity is involved in the pathology of pregnancy complications including pregnancy-induced hypertension and pre-eclampsia (PE). The recent studies about the overmuch inflammatory responses and aberrant placentation are associated with increased expression of TLRs in PE patients. This review has tried to focus on the relationship between some activities of TLRs and the risk of preeclampsia development.

Targeting toll-like receptor 4 signalling pathways: can therapeutics pay the toll for hypertension?

The immune system plays a prominent role in the initiation and maintenance of hypertension. The innate immune system, via toll-like receptors (TLRs), identifies distinct signatures of invading microbes and damage-associated molecular patterns and triggers a chain of downstream signalling cascades, leading to secretion of pro-inflammatory cytokines and shaping the adaptive immune response. Over the past decade, a dysfunctional TLR-mediated response, particularly via TLR4, has been suggested to support a chronic inflammatory state in hypertension, inducing deleterious local and systemic effects in host cells and tissues and contributing to disease progression. While the underlying mechanisms triggering TLR4 need further research, evidence suggests that sustained elevations in BP disrupt homeostasis, releasing endogenous TLR4 ligands in hypertension. In this review, we discuss the emerging role of TLR4 in the pathogenesis of hypertension and whether targeting this receptor and its signalling pathways could offer a therapeutic strategy for management of this multifaceted disease. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Both maternal and placental toll-like receptor activation are necessary for the full development of proteinuric hypertension in mice

OBJECTIVE

Innate immune system activation and excessive inflammation contributes to hypertension during pregnancy (HTN-preg). Activation of Toll-like receptors (TLRs), the primary innate immune system sensor, is evident in women with HTN-preg and is sufficient to induce pregnancy-dependent, proteinuric hypertension in animals. However, whether HTN-preg is a maternal disease, a placental disease, or both is unclear. We hypothesized that activation of TLR3, the double-stranded RNA sensor, in both maternal systemic and placental cells would be necessary for the full development of HTN-preg in mice.

STUDY DESIGN

Various mating schemes generated pregnant mice that lacked TLR3 in maternal cells, paternally-derived placental cells, and both. Mice were then injected with a TLR3 agonist on days 13, 15, and 17 of pregnancy.

MAIN OUTCOME MEASURES

Blood pressure, urinary protein excretion, fetal development, maternal vascular endothelial function, and immune system activation were all assessed and compared between groups.

RESULTS

Pregnant mice lacking TLR3 in maternal cells as well as pregnant mice lacking TLR3 in placental cells had significantly attenuated increases in systolic blood pressure, urinary protein excretion, fetal demise, and endothelial dysfunction compared to wild-type pregnant mice following TLR3 activation. Pregnant mice lacking TLR3 in both maternal systemic and placental cells were completely resistant to the hypertension, proteinuria, fetal demise, endothelial dysfunction, splenomegaly, and increases in pro-inflammatory immune cells induced by TLR3 activation.

CONCLUSIONS

These data suggest that both maternal and placental TLR3 activation are crucial for the full development of HTN-preg and that TLR3 antagonists may be beneficial in some women with HTN-preg.

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.

MicroRNAs: New Players in the Pathobiology of Preeclampsia

Our understanding of how microRNAs (miRNAs) regulate gene networks and affect different molecular pathways leading to various human pathologies has significantly improved over the years. In contrary, the role of miRNAs in pregnancy-related hypertensive disorders such as preeclampsia (PE) is only beginning to emerge. Recent papers highlight that adverse pregnancy outcomes are associated with aberrant expression of several miRNAs. Presently, efforts are underway to determine the biologic function of these placental miRNAs which can shed light on their contribution to these pregnancy-related disease conditions. The discovery that miRNAs are stable in circulation coupled with the fact that the placenta is capable of releasing them to the circulation in exosomes generates a lot of enthusiasm to use them as biomarkers. In this review, we will summarize the recent findings of our understanding of miRNA regulation in relation to PE, a hypertensive disorder of pregnancy. Particular emphasis will be given to the role of key miRNA molecules such as miR-210 and miR-155 that are known to be consistently dysregulated in women with PE.

Sphingolipids as a new factor in the pathomechanism of preeclampsia - Mass spectrometry analysis

Objective(s) and design

The aim of the study was to analyse a panel of 11 sphingolipids in plasma and three blood fractions (platelet-poor plasma, platelets and red blood cells) of women with mild preeclampsia.

Materials and methods

We recruited 21 women between 25–40 weeks gestation with diagnosed mild preeclampsia to the study group and 36 healthy women with uncomplicated pregnancies, who corresponded with the study group according to gestational age, to the control group. To assess the concentration of 11 sphingolipids in the blood plasma and blood fractions, we used ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC/MS/MS).

Results

We showed a significant increase in the concentration of eight sphingolipids in the plasma of women with preeclampsia in comparison to the control group: Sph (p = 0.0032), S1P (p = 0.0289), C20-Cer (p < 0.0001), C18-Cer (p < 0.0001), C16-Cer (p = 0.012), C18:1-Cer (p = 0.003), C22-Cer (p = 0.0071), and C24:1-Cer (p = 0.0085).

Conclusion

We showed that selected sphingolipids, especially C20-Cer and C18-Cer, are totally new factors in the pathomechanism of PE and that these bioactive lipids may play an important role in apoptosis and autophagy.

Preeclampsia and health risks later in life: an immunological link

Pregnancy represents a period of physiological stress, and although this stress is experienced for a very modest portion of life, it is now recognized as a window to women's future health, often by unmasking predispositions to conditions that only become symptomatic later in life. In normal pregnancy, the mother experiences mild metabolic syndrome-like condition through week 20 of gestation. A pronounced phenotype of metabolic syndrome may program pregnancy complications such as preeclampsia. Preeclampsia is a serious complication with a myriad of manifestations for mother and offspring. This pregnancy syndrome is a polygenic disease and has been now linked to higher incidence of cardiovascular disease, diabetes, and several other disorders associated with vulnerable organs. Furthermore, the offspring born to preeclamptic mothers also exhibit an elevated risk of cardiovascular disease, stroke, and mental disorders during adulthood. This suggests that preeclampsia not only exposes the mother and the fetus to complications during pregnancy but also programs chronic diseases in later life. The etiology of preeclampsia is thought to be primarily associated with poor placentation and entails excessive maternal inflammation and endothelial dysfunction. It is well established now that the maternal immune system and the placenta are involved in a highly choreographed cross-talk that underlies adequate spiral artery remodeling required for uteroplacental perfusion and free flow of nutrients to the fetus. Since normal pregnancy is associated with a sequence of events represented by temporal events of inflammation (implantation), anti-inflammation (gestation), and inflammation (parturition), it is quite possible that unscheduled alterations in these regulatory responses may lead to pathologic consequences. Although it is not clear whether immunological alterations occur early in pregnancy, it is proposed that dysregulated systemic and placental immunity contribute to impaired angiogenesis and the onset of preeclampsia. This review will focus on important aspects of the immune system that coordinate with placental dysfunction to program preeclampsia and influence health in later life.

Human placenta-derived stromal cells decrease inflammation, placental injury and blood pressure in hypertensive pregnant mice

Pre-eclampsia, the development of hypertension and proteinuria or end-organ damage during pregnancy, is a leading cause of both maternal and fetal morbidity and mortality, and there are no effective clinical treatments for pre-eclampsia aside from delivery. The development of pre-eclampsia is characterized by maladaptation of the maternal immune system, excessive inflammation and endothelial dysfunction. We have reported that detection of extracellular RNA by the Toll-like receptors (TLRs) 3 and 7 is a key initiating signal that contributes to the development of pre-eclampsia. PLacental eXpanded (PLX-PAD) cells are human placenta-derived, mesenchymal-like, adherent stromal cells that have anti-inflammatory, proangiogenic, cytoprotective and regenerative properties, secondary to paracrine secretion of various molecules in response to environmental stimulation. We hypothesized that PLX-PAD cells would reduce the associated inflammation and tissue damage and lower blood pressure in mice with pre-eclampsia induced by TLR3 or TLR7 activation. Injection of PLX-PAD cells on gestational day 14 significantly decreased systolic blood pressure by day 17 in TLR3-induced and TLR7-induced hypertensive mice (TLR3 144-111 mmHg; TLR7 145-106 mmHg; both P<0.05), and also normalized their elevated urinary protein:creatinine ratios (TLR3 5.68-3.72; TLR7 5.57-3.84; both P<0.05). On gestational day 17, aortic endothelium-dependent relaxation responses improved significantly in TLR3-induced and TLR7-induced hypertensive mice that received PLX-PAD cells on gestational day 14 (TLR3 35-65%; TLR7 37-63%; both P<0.05). In addition, markers of systemic inflammation and placental injury, increased markedly in both groups of TLR-induced hypertensive mice, were reduced by PLX-PAD cells. Importantly, PLX-PAD cell therapy had no effects on these measures in pregnant control mice or on the fetuses. These data demonstrate that PLX-PAD cell therapy can safely reverse pre-eclampsia-like features during pregnancy and have a potential therapeutic role in pre-eclampsia treatment.