Transforming growth factor-beta 1 does not relate to hypertension in pre-eclampsia

TGFβ signalling: a nexus between inflammation, placental health and preeclampsia throughout pregnancy

BACKGROUND

The placenta is a unique and pivotal organ in reproduction, controlling crucial growth and cell differentiation processes that ensure a successful pregnancy. Placental development is a tightly regulated and dynamic process, in which the transforming growth factor beta (TGFβ) superfamily plays a central role. This family of pleiotropic growth factors is heavily involved in regulating various aspects of reproductive biology, particularly in trophoblast differentiation during the first trimester of pregnancy. TGFβ signalling precisely regulates trophoblast invasion and the cell transition from cytotrophoblasts to extravillous trophoblasts, which is an epithelial-to-mesenchymal transition-like process. Later in pregnancy, TGFβ signalling ensures proper vascularization and angiogenesis in placental endothelial cells. Beyond its role in trophoblasts and endothelial cells, TGFβ signalling contributes to the polarization and function of placental and decidual macrophages by promoting maternal tolerance of the semi-allogeneic foetus. Disturbances in early placental development have been associated with several pregnancy complications, including preeclampsia (PE) which is one of the severe complications. Emerging evidence suggests that TGFβ is involved in the pathogenesis of PE, thereby offering a potential target for intervention in the human placenta.

OBJECTIVE AND RATIONALE

This comprehensive review aims to explore and elucidate the roles of the major members of the TGFβ superfamily, including TGFβs, bone morphogenetic proteins (BMPs), activins, inhibins, nodals, and growth differentiation factors (GDFs), in the context of placental development and function. The review focusses on their interactions within the major cell types of the placenta, namely trophoblasts, endothelial cells, and immune cells, in both normal pregnancies and pregnancies complicated by PE throughout pregnancy.

SEARCH METHODS

A literature search was carried out using PubMed and Google Scholar, searching terms: 'TGF signalling preeclampsia', 'pregnancy TGF signalling', 'preeclampsia tgfβ', 'preeclampsia bmp', 'preeclampsia gdf', 'preeclampsia activin', 'endoglin preeclampsia', 'endoglin pregnancy', 'tgfβ signalling pregnancy', 'bmp signalling pregnancy', 'gdf signalling pregnancy', 'activin signalling pregnancy', 'Hofbauer cell tgfβ signalling', 'placental macrophages tgfβ', 'endothelial cells tgfβ', 'endothelium tgfβ signalling', 'trophoblast invasion tgfβ signalling', 'trophoblast invasion Smad', 'trophoblast invasion bmp', 'trophoblast invasion tgfβ', 'tgfβ preeclampsia', 'tgfβ placental development', 'TGFβ placental function', 'endothelial dysfunction preeclampsia tgfβ signalling', 'vascular remodelling placenta TGFβ', 'inflammation pregnancy tgfβ', 'immune response pregnancy tgfβ', 'immune tolerance pregnancy tgfβ', 'TGFβ pregnancy NK cells', 'bmp pregnancy NK cells', 'bmp pregnancy tregs', 'tgfβ pregnancy tregs', 'TGFβ placenta NK cells', 'TGFβ placenta tregs', 'NK cells preeclampsia', 'Tregs preeclampsia'. Only articles published in English until 2023 were used.

OUTCOMES

A comprehensive understanding of TGFβ signalling and its role in regulating interconnected cell functions of the main placental cell types provides valuable insights into the processes essential for successful placental development and growth of the foetus during pregnancy. By orchestrating trophoblast invasion, vascularization, immune tolerance, and tissue remodelling, TGFβ ligands contribute to the proper functioning of a healthy maternal-foetal interface. However, dysregulation of TGFβ signalling has been implicated in the pathogenesis of PE, where the shallow trophoblast invasion, defective vascular remodelling, decreased uteroplacental perfusion, and endothelial cell and immune dysfunction observed in PE, are all affected by an altered TGFβ signalling.

WIDER IMPLICATIONS

The dysregulation of TGFβ signalling in PE has important implications for research and clinical practice. Further investigation is required to understand the underlying mechanisms, including the role of different ligands and their regulation under pathophysiological conditions, in order to discover new therapeutic targets. Distinguishing between clinically manifested subtypes of PE and studying TGFβ signalling in different placental cell types holistically is an important first step. To put this knowledge into practice, pre-clinical animal models combined with new technologies are needed. This may also lead to improved human research models and identify potential therapeutic targets, ultimately improving outcomes for affected pregnancies and reducing the burden of PE.

Circulating levels of transforming growth factor beta-1, 2 and 3 in HIV associated preeclamptic pregnancies

The active role of transforming growth factor-beta in implantation, embryonic development and decidualization has driven our interest to evaluate circulating TGF-β(1-3) in the synergy of HIV associated pregnancy. Serum TGF-β(1-3) was quantified in normotensive (n = 38) and preeclamptic (n = 38) pregnant women, who were stratified by HIV status, HIV negative (n = 19) and HIV positive (n = 19), using a Bioplex immunoassay.Based on HIV status, we report no significant difference in TGF-β-1 (p = .95) and TGF-β2 (p = .80) however, TGF-β3 was significantly downregulated in HIV positive (p = .03) vs the HIV negative groups. A significant positive correlation (p < .05) was noted between TGF-β3 and gestational age (p = .03) (r = 0.51), birth weight (p = .04) (r = 0.53) and CD4 count (p = .02) (r = 0.53). Bivariate correlation between isoforms based on HIV status showed several significant positive associations. In the synergy of HIV infected PE, we demonstrate an association between TGF-β(1-3) with PE emanating from the hypoxic microenvironment that affects receptor-SMAD activity. Decreased TGF-β3 levels in HIV infected PE, may originate from ARV usage and/or the mutational/physiological dysregulation of SMAD expression. Impact StatementWhat is already known on this subject? TGF-β overexpression can convert its protective functions into pathogenic variants. It has a significant role in the oxidatively stressed and inflammatory condition of tissue fibrosis and hence may also be dysregulated in the microenvironment of PE. In HIV infection, TGF-β promotes viral replication and spreading through the induction of cellular proteins which induce TGF-β production. Also, mononuclear phagocytes infected with HIV also produce increased TGF-β mRNA and proteins.What do the results of the study add? Our results show no association of TGF-β isoforms (1-3) based on pregnancy type (PE vs normotensive pregnant) at term. The lack of association may be linked to TGF-βs dual promoter/suppresser nature or to gestational age.What are the implications of these findings for clinical practice and/or further research? Large-scale comprehensive clinical trials are warranted to elucidate the association and mechanistic role of TGF-β receptor-SMAD signalling, the effect of its inhibitors on cell invasion and angiogenesis as well as to deliver valuable data for the detection of novel therapeutic agents in pregnancies complicated by HIV infection.

TGF-β1 inhibits human trophoblast cell invasion by upregulating kisspeptin expression through ERK1/2 but not SMAD signaling pathway

BACKGROUND

Tightly regulation of extravillous cytotrophoblast (EVT) cell invasion is critical for the placentation and establishment of a successful pregnancy. Insufficient EVT cell invasion leads to the development of preeclampsia (PE) which is a leading cause of maternal and perinatal mortality and morbidity. Transforming growth factor-beta1 (TGF-β1) and kisspeptin are expressed in the human placenta and have been shown to inhibit EVT cell invasion. Kisspeptin is a downstream target of TGF-β1 in human breast cancer cells. However, whether kisspeptin is regulated by TGF-β1 and mediates TGF-β1-suppressed human EVT cell invasion remains unclear.

METHODS

The effect of TGF-β1 on kisspeptin expression and the underlying mechanisms were explored by a series of in vitro experiments in a human EVT cell line, HTR-8/SVneo, and primary cultures of human EVT cells. Serum levels of TGF-β1 and kisspeptin in patients with or without PE were measured by ELISA.

RESULTS

TGF-β1 upregulates kisspeptin expression in HTR-8/SVneo cells and primary cultures of human EVT cells. Using pharmacological inhibitor and siRNA, we demonstrate that the stimulatory effect of TGF-β1 on kisspeptin expression is mediated via the ALK5 receptor. Treatment with TGF-β1 activates SMAD2/3 canonical pathways as well as ERK1/2 and PI3K/AKT non-canonical pathways. However, only inhibition of ERK1/2 activation attenuates the stimulatory effect of TGF-β1 on kisspeptin expression. In addition, siRNA-mediated knockdown of kisspeptin attenuated TGF-β1-suppressed EVT cell invasion. Moreover, we report that serum levels of TGF-β1 and kisspeptin are significantly upregulated in patients with PE.

CONCLUSIONS

By illustrating the potential physiological role of TGF-β1 in the regulation of kisspeptin expression, our results may serve to improve current strategies used to treat placental diseases.

Cardiac dysfunction after preeclampsia; an overview of pro- and anti-fibrotic circulating effector molecules

Preeclampsia (PE) is strongly associated with heart failure (HF) later in life. The aberrant cardiac remodelling is likely initiated or amplified during preeclamptic pregnancy. Aberrant remodelling often persists after delivery and is known to relate strongly to cardiac fibrosis. This review provides an overview of pro- and anti- fibrotic circulating effector molecules that are involved in cardiac fibrosis and their association with PE. Women with PE complicated pregnancies show increased ANG-II sensitivity and elevated levels of the pro-fibrotic factors IL-6, TNF-α, TGs and FFAs compared to uncomplicated pregnancies. In the postpartum period, PE pregnancies compared to uncomplicated pregnancies have increased ANG-II sensitivity, elevated levels of the pro-fibrotic factors IL-6, TNF-α, LDL cholesterol and leptin, as well as decreased levels of the anti-fibrotic factor adiponectin. The review revealed several profibrotic molecules that associate to cardiac fibrosis during and after PE. The role that these fibrotic factors have on the heart during and after PE may improve the understanding of the link between PE and HF. Furthermore they may provide insight into the pathways in which the relation between both diseases can be understood as potential mechanisms which interfere in the process of cardiovascular disease (CVD). Unravelling the molecular mechanism and pathways involved might bring the diagnostic and therapeutic abilities of those factors a step closer.

The transforming growth factor β superfamily as possible biomarkers of preeclampsia: a comprehensive review

The etiology of preeclampsia - an abnormal placentation-mediated disease - is not fully understood; and there are very few biomarkers with which to predict and diagnose it. Early prediction and diagnosis of this pathology can lead to a significant improvement in maternal and perinatal outcomes. Since members of the transforming growth factor β superfamily influence placentation, and are released from the placenta into the maternal circulatory system, several studies have investigated the involvement of these cytokines in preeclampsia and the possibility of using their serum levels as biomarkers of the disease. In this review, we have summarized the reported relationships between the levels of this superfamily of cytokines and preeclampsia. The available information indicates that altered levels of some of these cytokines are involved in the pathogenesis and pathophysiology of preeclampsia, suggesting their likelihood of serving as predictive and diagnostic biomarkers of the disease.

Transforming growth factor beta-1 (TGF-β1) gene single nucleotide polymorphisms (SNPs) and susceptibility to pre-eclampsia in Iranian women: A case-control study

OBJECTIVES

Pre-eclampsia (PE) is a disorder of pregnancy characterized by high blood pressure and proteinuria. Transforming growth factor beta-1 (TGF-β1) is an important replicated PE candidate gene, and few studies have evaluated the direct association of TGF-β polymorphisms and risk to PE. The aim of this study was to investigate the association between three SNPs of TGF-β1 and serum level of this cytokine in PE patients and controls.

DESIGN AND METHODS

In this study the polymorphisms of the TGF-β1 gene at the coding region, and positions 29T→C (Leu 10 Pro), 74G→C (Arg 25 Pro) and 788C→T (Thr 263 Ile) were studied in 123 PE and 120 normal subjects using PCR-restriction fragment length polymorphism PCR-(RFLP) and amplification refractory mutation system (ARMS)-PCR methods. Moreover, serum TGF-β1 was determined by enzyme-linked immunosorbent assay (ELISA) technique.

RESULTS

At positions 74G→C and 29T→C the genotypes and allele frequencies showed no significant differences between PE patients and normal controls (P=0.3 and P=0.5 respectively). While in the case of position 788C→T both genotypes and allele frequencies were significantly different between PE patients and controls (P=0.02). Haplotype analysis on three polymorphic sites showed no significant differences between PE and control individuals (P=0.8). TGC and CGC haplotypes were the most frequent in both studied groups. The mean serum TGF-β1 level was significantly higher (62.73ng/ml) in PE patients compared with pregnant (47.01ng/ml) and non-pregnant (40.68ng/ml) control groups (P=0.0001).

CONCLUSIONS

The results of this study suggest that TGF-β1 gene 788C→T polymorphism is an important factor mediating the casual pathway of preeclampsia.

Polymorphisms and plasma level of transforming growth factor-Beta 1 and risk for preeclampsia: a systematic review

BACKGROUND

Transforming growth factor-beta 1 (TGF-β1) is thought to be involved in the pathogenesis of preeclampsia (PE), but the results are inconsistent among studies. This article aims to compile an overview of the studies about the associations of TGF-β 1 polymorphism and plasma level with PE risk and to provide recommendations for future research.

METHODS AND RESULTS

The databases PubMed, Embase and Web of Science were searched up to December 2013. Five studies investigating the associations of four polymorphisms with the risks of PE were involved. A meta-analysis was conducted for the 869T>C polymorphism and PE risk. The results show that genotype TT of 869T>C polymorphism is a protective factor of PE (pooled odds ratio=0.73, 95% CI: 0.56, 0.95). Eight case-control studies reported the plasma level of TGF-β 1. The substantial heterogeneity among studies may be attributed to the differences in the blood sample processing and the TGF-β 1 analysis kits. The results suggest that plasma TGF-β 1 level in the second trimester was significantly lower in the PE group than in the normal pregnancy group, but was significantly higher in the PE group during the third trimester.

CONCLUSIONS

The current results support that the TGF-β 1 869 T>C polymorphism was associated with the risk of PE. However, the number of eligible studies is small and more studies are needed to clarify whether this association can be detected on larger sample sizes and different populations. Owing to the heterogeneity between studies, no conclusion on the association between plasma TGF-β 1 level and PE risk can be drawn from this review. Further studies about the TGF-β 1 levels at different stages of pregnancy and the development of TGF-β 1 assay methodology are required to reveal the role of TGF-β 1 in the pathological development of PE.

Promoter region polymorphisms in the transforming growth factor beta-1 (TGFβ1) gene and serum TGFβ1 concentration in preeclamptic and control Iranian women

Preeclampsia (PE) is a pregnancy associated disorder characterized by hypertension and proteinuria, which causes neonatal and maternal morbidity and mortality. The Th1/Th2 cytokine paradigm of the immune adaptation in pregnancy is now expanded to include Th1/Th2/Th17 and regulatory T (Treg) cells. Among cytokines, TGFβ1 has properties that justify evaluation of its role in PE etiopathology. In this investigation the polymorphisms of the TGFβ1 gene at promoter region, positions -800G→A and -509C→T, were studied in 142 PE and 140 normal pregnant female subjects using PCR-RFLP. Additionally, serum TGFβ1 was determined by ELISA. At position -800G→A genotypes and allele frequencies showed no significant differences between PE patients (GG 73.9%; GA 21.1%; AA 4.93%) and normal control (GG 70%; GA 28.6%; AA 1.4%) women. However the AA genotype at this position was more frequent in PE patients than in the control group. At -509C→T position, genotypes and allele frequencies showed no significant differences between PE patients and control individuals. The CC genotype at -509C→T position was more prevalent in PE patients than in the control group. The mean serum TGFβ1 level was significantly higher (62.14 ng/ml) in PE patients compared with pregnant and non-pregnant control groups (and 47.01 and 40.68 ng/ml, respectively). In conclusion, the promoter region polymorphisms of TGFβ1 may not be associated with PE, but serum levels of this cytokine may contribute to the etiopathology of PE.

Maternal gene expression profiling during pregnancy and preeclampsia in human peripheral blood mononuclear cells

Preeclampsia is a major obstetrical complication affecting maternal and fetal health. While it is clear that there is a substantial placental contribution to preeclampsia pathogenesis, the maternal contribution is less well characterized. We therefore performed a genome-wide transcriptome analysis to explore disease-associated changes in maternal gene expression patterns in peripheral blood mononuclear cells (PBMCs).

METHODS

Preeclampsia was defined as gestational hypertension, proteinuria and hyperurecimia. Total RNA was isolated from PBMCs obtained from women with uncomplicated pregnancies (n = 5) and women with preeclamptic pregnancies (n = 5). Gene expression analysis was carried out using Agilent oligonucleotide microarrays. Biological pathway analysis was undertaken using Ingenuity Pathway Analysis software. Quantitative real-time PCR (QRTPCR) was performed to validate the gene expression changes of selected genes in normotensive and preeclamptic patients (n = 12 each).

RESULTS

We identified a total of 368 genes that were differentially expressed in women with preeclampsia compared to normal controls with false discovery rate (FDR) controlled at 10%. In follow up experiments we further analyzed the expression levels of a number of genes that were identified as altered by the microarray data including survivin (BIRC5), caveolin (CAV1), GATA binding protein-1 (GATA1), signal tranducer and activator of transcription 1 (STAT1), E2F transcription factor-1 (E2F1), fibronectin-1 (FN1), interleukin-4 (IL-4), matrix metalloprotease-9 (MMP-9) and WAP four disulfide domain protein (WFDC-1) by QRTPCR. Additionally we performed immuno blot analysis and zymography to verify some of these candidate genes at the protein level. Computational analysis of gene function identified an anti-proliferative and altered immune function cellular phenotype in severe preeclamptic samples.

CONCLUSIONS

We have characterized the genome-wide mRNA expression changes associated with preeclampsia-specific genes in circulating maternal blood cells at the time of delivery. In addition to providing information relating to the biological basis of the preeclampsia phenotype, our data provide a number of potential biomarkers for use in the further characterization of this disease.

Platelet aggregation and TGF-beta(1) plasma levels in pregnant women with preeclampsia

OBJECTIVES

Platelets and transforming growth factor-beta(1) (TGF-beta(1)) are thought to be involved in the pathogenesis of preeclampsia. Our objectives were to determine plasma concentration of TGF-beta(1) in normotensive and preeclamptic women in the third trimester of pregnancy and to evaluate the correlation of TGF-beta(1) plasma levels with platelet count and agonist-induced aggregation capacity.

METHODS

Thirty-three women with preeclampsia were compared with 36 healthy women with uncomplicated pregnancies. Peripheral venous blood samples were obtained, and TGF-beta(1) plasma levels measured by an enzyme-linked immunoassay. Platelet aggregation was induced by the agonist agents adenosine diphosphate (ADP), collagen and epinephrine, and was determined in platelet-rich plasma by aggregometry.

RESULTS

Plasma concentrations of active TGF-beta(1) were significantly higher in preeclamptic women (10.41+/-2.07ng/mL) compared with normotensive pregnant women (7.01+/-3.29ng/mL). Platelet number and platelet agonist-induced aggregation percent were significantly lower in patients with preeclampsia than in healthy pregnant women. A significant correlation was observed between TGF-beta(1) plasma levels and platelet agonist-induced aggregation percent as between plasma levels of TGF-beta(1) and platelet number in preeclamptic patients.

CONCLUSION

The association between impairment in platelet responsiveness and higher levels of TGF-beta(1) in the plasma of patients with preeclampsia suggests that this cytokine may play a role in the pathophysiological events of preeclampsia that are dependent on platelet activation.

Effective prediction of preeclampsia by a combined ratio of angiogenesis-related factors

OBJECTIVE

Imbalance between angiogenesis-related factors is closely related to the development of preeclampsia. The objective was to estimate the most effective and accurate predictive biomarker among levels and ratios of angiogenesis-related factors, including soluble fms-like tyrosine kinase 1 (sFlt-1), soluble endoglin, placental growth factor (PlGF), and transforming growth factor-beta1 (TGF-beta1), in women who subsequently developed preeclampsia.

METHODS

A nested cohort study was conducted to estimate the levels of sFlt-1, soluble endoglin, PlGF, and TGF-beta1 in plasma collected in the second trimester from 40 women who subsequently developed preeclampsia and 100 contemporaneous normotensive women.

RESULTS

Levels of sFlt-1 and soluble endoglin were significantly higher in women with preeclampsia than in normotensive women, whereas levels of PlGF and TGF-beta1 were lower (P<.001). In women with preeclampsia, sFlt-1/PlGF, soluble endoglin/TGF-beta1, and the combined ratio of (sFlt-1+soluble endoglin)/(PlGF+TGF-beta1) were significantly higher than in normotensive women (P<.001) and even greater in severe preeclampsia with preterm delivery compared with mild preeclampsia with term delivery (P<.05). At equivalent sensitivity (85%), the false-positive rate was 45% for sFlt-1, 41% for soluble endoglin, 33% for sFlt-1/PlGF, 21% for soluble endoglin/TGF-beta1, and 10% for the combined ratio. After adjusting for potential confounding factors, the risks for developing preeclampsia were as follows: odds ratio (OR) 6.9 [95% confidence interval 2.3-20.7] for sFlt-1 level, 7.1 [2.3-21.7] for soluble endoglin level, 6.8 [2.4-19.4] for sFlt-1/PlGF, 38.8 [9.8-154.3] for soluble endoglin/TGF-beta1, and 74.8 [17.6-316.7] for the combined ratio.

CONCLUSION

The combined ratio of angiogenesis-related factors showed the lowest false-positive rate and the highest OR for prediction of preeclampsia, indicating that it may provide more effective prediction of development of preeclampsia.

LEVEL OF EVIDENCE

II.

Inflammatory Changes in Preeclampsia: Current Understanding of the Maternal Innate and Adaptive Immune Response

Preeclampsia is characterized by generalized endothelial dysfunction as a result of an inappropriate maternal immune response against the fetus. It has been postulated that the adaptive immune system plays a key role in the etiology of preeclampsia by generating a pro-inflammatory Th1 type immune reaction. In this review, recent studies on Th1 and Th2 type cytokine mapping in preeclampsia are reviewed, as well as on the sources of pro-inflammatory cytokines and the role of regulatory cytokines and chemokines. In addition, we discuss the possible role of Toll-like receptors of the innate immune system in the pathophysiology of preeclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to summarize the newer concepts related to the pathogenesis of preeclampsia and explain the role of the maternal immune system and the role of pro-inflammatory and regulatory cytokines and chemokines in the pathophysiology of the disease.

Soluble endoglin contributes to the pathogenesis of preeclampsia

Preeclampsia is a pregnancy-specific hypertensive syndrome that causes substantial maternal and fetal morbidity and mortality. Maternal endothelial dysfunction mediated by excess placenta-derived soluble VEGF receptor 1 (sVEGFR1 or sFlt1) is emerging as a prominent component in disease pathogenesis. We report a novel placenta-derived soluble TGF-beta coreceptor, endoglin (sEng), which is elevated in the sera of preeclamptic individuals, correlates with disease severity and falls after delivery. sEng inhibits formation of capillary tubes in vitro and induces vascular permeability and hypertension in vivo. Its effects in pregnant rats are amplified by coadministration of sFlt1, leading to severe preeclampsia including the HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome and restriction of fetal growth. sEng impairs binding of TGF-beta1 to its receptors and downstream signaling including effects on activation of eNOS and vasodilation, suggesting that sEng leads to dysregulated TGF-beta signaling in the vasculature. Our results suggest that sEng may act in concert with sFlt1 to induce severe preeclampsia.

Maternal plasma transforming growth factor-beta1 concentrations in preeclamptic and normotensive pregnant Zimbabwean women

OBJECTIVE

We examined the relationship between maternal plasma transforming growth factor-beta1 (TGF-beta1) concentrations and risk of preeclampsia among women delivering at Harare Maternity Hospital in Zimbabwe. We evaluated the relationship in the context of maternal systemic inflammation using plasma tumor necrosis factor-a soluble receptor p55 (sTNFp55) as a marker.

METHODS

132 women with preeclampsia and 180 controls were included in this case-control study analysis. Maternal post-diagnosis plasma TGF-beta1 and sTNFp55 concentrations were determined using immunoassays. Logistic regression procedures were used to estimate odds ratios (OR) and 95% confidence intervals (CI) adjusted for confounders.

RESULTS

A linear increase in preeclampsia risk was observed with increasing quartiles of TGF-beta1 concentrations (p<0.01). Women whose TGF-beta1 concentrations were >or=25.1 ng/ml (quartile 4) had a 2.5-fold (95% CI 1.2-5.6) increased risk of preeclampsia as compared with those women whose concentrations were <11.2 ng/ml (quartile 1). Relative to women with no evidence of systemic inflammation and no elevated TGF-beta1 concentrations, those women who were jointly positive for elevated TGF-beta1 and sTNFp55 concentrations experienced a 5.3-fold (95% CI 2.3-12.0) increased risk of preeclampsia.

CONCLUSION

Overall, we noted that elevated TGF-beta1 is associated with an increased risk of preeclampsia. We also noted that the preeclampsia risk is exaggerated in the presence of maternal systemic inflammation.

The role of transforming growth factor β1 in the vascular system

The transforming growth factor beta (TGFbeta) family of cytokines exert pleiotropic effects upon a wide variety of cell types. TGFbeta1 has been demonstrated to be of fundamental importance in the development, physiology and pathology of the vascular system. As the role of TGFbeta1 in these processes becomes clearer, influencing its activity for therapeutic benefit is now beginning to be investigated. This review presents an overview of the role of TGFbeta1 in the vasculature. The cellular and extracellular biology of the TGFbeta family is first addressed, followed by an overview of the function of TGFbeta1 during vascular development, atherogenesis, hypertension, and vessel injury.

TGF-beta induces proangiogenic and antiangiogenic factors via parallel but distinct Smad pathways

BACKGROUND

Angiogenesis has a key role in numerous disease processes. One of the most important angiogenic factors is vascular endothelial growth factor (VEGF-A), whereas thrombospondin-1 (TSP-1) is a major antiangiogenic factor. Recent studies have shown that VEGF-A as well as TSP-1 is regulated by transforming growth factor-beta1 (TGF-beta1), but the mechanism remains unclear.

METHODS

We examined the role of TGF-beta1 and its signaling pathways in mediating expression of these two molecules. Rat proximal tubular cells (NRK52E) were stimulated with TGF-beta1 to induce VEGF-A and TSP-1 synthesis. To clarify roles of receptor-activated Smads (R-Smads), we blocked Smad signaling using overexpression of the inhibitory Smad, Smad7, and by using fibroblasts from wild-type or knockout mice. To confirm the antiantigenic role of Smads, soluble Flt-1 regulation in response to TGF-beta1 was also examined. In addition, the effect of conditioned media from NRK52E and Smad knockout cells was examined on endothelial cell proliferation.

RESULTS

Induction of VEGF-A and TSP-1 by TGF-beta1 in NRK52E cells was associated with activation of pathway-restricted R-Smads (Smad2 and 3) and blocking these Smads by overexpression of Smad7 blocked their induction. By using of Smad knockout cells, Smad3 was shown to have a key role in the stimulation of VEGF-A expression whereas Smad2 was critical for TSP-1 expression. Consistent with the hypothesis that Smad2 has an antiangiogenic function, we also demonstrated that Smad2, but not Smad3, mediated the expression of VEGF-A antagonist, soluble VEGF-A receptor sFlt-1, in response to TGF-beta1. Conditioned media from NRK52E, which was stimulated by TGF-beta1 for 24 hours, did not induce endothelial cell proliferation. However, conditioned media from Smad2 knockout induced endothelial cell proliferation, whereas endothelial cell proliferation was inhibited by Smad3 knockout-derived conditioned media.

CONCLUSION

R-Smads have distinct roles in mediating the expression of pro- and antiangiogenic growth factors in response to TGF-beta1.