Angiogenic balance (sFlt-1/PlGF) and preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy associated with important maternal and perinatal mortality and morbidity. Although symptomatic management has improved, there is currently no curative treatment, and only childbirth and delivery of the placenta, usually prematurely, alleviate the mother's symptoms. Placental insufficiency plays a central role in the pathophysiology of preeclampsia. Abnormal placentation during the first trimester leads to defective remodeling of the uterine vascularization. This results progressively in placental hypoperfusion, which induces trophoblast dysfunction and the release in maternal circulation of trophoblastic factors leading to an excessive inflammatory response, endothelial dysfunction and glomerular damage. Among these factors, the most important is sFlt-1, which is a soluble form of the VEGF and PlGF receptor. sFlt-1 binds to free VEGF and PlGF in the maternal circulation, thus reducing their bioavailability for their membrane receptor. The result is inhibition of the effects of VEGF and PlGF on maternal endothelial cells and podocytes. The sFlt-1/PlGF ratio reflects the circulating angiogenic balance and is correlated with severity of the disease.     

Correlation between soluble endoglin, vascular endothelial growth factor receptor-1, and adipocytokines in preeclampsia

CONTEXT: Recent reports have demonstrated that soluble endoglin (sEng), an antiangiogenic protein thought to impair TGF-beta binding to receptors, and soluble vascular endothelial growth factor receptor (sVEGFR)-1 play important roles in the pathophysiology of preeclampsia (PE). Moreover, insulin resistance, which is greatly influenced by adipocytokines, characterizes PE. OBJECTIVES: We examined possible links between sEng, VEGF, sVEGFR, and adipocytokines in the pathophysiology of PE. STUDY DESIGN: We performed a cross-sectional study in 30 PE patients and controls matched for gestational age and body mass index. Blood samples were collected soon after disease onset. We measured serum concentrations of leptin, adiponectin, sEng, VEGF, placental growth factor (PlGF), and sVEGFR [soluble fms-like tyrosine kinase 1 (sFlt-1) and soluble fetal liver kinase 1 (sFlk-1)], and examined the placental protein content of sEng and sFlt-1. RESULTS: sEng concentrations in PE patients (60.9 +/- 28.8 ng/ml) were significantly higher than those in controls (11.2 +/- 4.4 ng/ml). There was a significant correlation between sEng and sFlt-1 or PlGF. Moreover, there were significant differences in mean blood pressure between the high and low sEng groups, and in proteinuria between the high and low sFlt-1 groups, and significant differences in placental sEng and sFlt-1 contents between patients with and without severe hypertension or proteinuria. sEng was also correlated positively with adiponectin levels and negatively with the leptin to adiponectin ratio. CONCLUSIONS: Along with sFlt-1 and PlGF, sEng might play a role in the pathophysiology of PE, especially in elevating blood pressure, while the association with hypoadiponectinemia and the high leptin to adiponectin ratio in pregnancy seem to be risk factors for PE.     

Cytotrophoblasts up-regulate soluble fms-like tyrosine kinase-1 expression under reduced oxygen: an implication for the placental vascular development and the pathophysiology of preeclampsia

Sufficient cytotrophoblast (CT) invasion into the uterine wall and subsequent remodeling of maternal uterine vasculature is critical to establish uteroplacental circulation. The production of vascular endothelial growth factor (VEGF) family molecules is confirmed in placental cells including CTs, but it is not elucidated how the VEGF system in CTs is controlled by oxygen tension and how it is involved in the development of placental circulation. To address this, we explored the effect of oxygen tension on the expression of VEGF, placenta growth factor (PlGF), and their antagonist, soluble fms-like tyrosine kinase-1 (sFlt-1) using ELISA and real-time PCR in a primary CT cell culture. For comparison, the same was conducted in parallel using other cells comprising placenta, such as human umbilical vein endothelial cells (HUVECs) and villous fibroblasts (VFs). Reduced oxygen resulted in a pronounced increase in sFlt-1 mRNA amount and sFlt-1 release into the culture media in CTs, whereas this was not the case with HUVECs and VFs. Free (not bound to sFlt-1) VEGF was not detected in CT culture media regardless of oxygen concentration, even though VEGF expression was stimulated by reduced oxygen in CTs, which was similar to the stimulation in HUVECs and VFs. Free PlGF was also diminished in CT culture media by reduced oxygen. These results implicate that CTs possess a unique property to enhance sFlt-1 production under reduced oxygen, which could consequently antagonize angiogenic activity of VEGF and PlGF. The presented findings might provide a framework with which to understand the mechanism of uterine vascular remodeling and its perturbations as exemplified in preeclampsia.     

Atorvastatin increases plasma soluble Fms-like tyrosine kinase-1 and decreases vascular endothelial growth factor and placental growth factor in association with improvement of ventricular function in acute myocardial infarction.

OBJECTIVES: This study examined whether atorvastatin increases plasma levels of soluble Fms-like tyrosine kinase 1 (sFlt-1) and reciprocally decreases vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) levels in patients with acute myocardial infarction (AMI). BACKGROUND: Statins exert cardioprotective actions partly through anti-inflammatory actions. By capturing VEGF and PlGF in plasma, sFlt-1 acts as a natural inhibitor of VEGF and PlGF, which have proinflammatory properties. METHODS: Left ventriculography and enzyme-linked immunosorbent assay of plasma levels of sFlt-1, VEGF, and PlGF were repeated after AMI in 50 consecutive patients with a first AMI. Patients were randomized to treatment with atorvastatin (10 mg/day; n=25) or placebo (n=25) within 3 days after AMI, and therapy was continued for 6 months. RESULTS: The sFlt-1 levels were low in the acute phase, followed by an increase at 2 weeks after AMI, whereas free VEGF and PlGF levels were high in the acute phase, followed by a decrease at 2 weeks. Atorvastatin increased sFlt-1 levels and reciprocally decreased VEGF and PlGF levels at 6 months compared with placebo. The increase in sFlt-1 levels and the decrease in VEGF and PlGF levels were correlated with improvement of left ventricular ejection fraction during the follow-up period. CONCLUSIONS: There was a reciprocal relationship between changes in sFlt-1 levels and changes in VEGF and PlGF levels after AMI; and atorvastatin increased sFlt-1 levels while decreasing VEGF and PlGF levels. These changes were associated with late improvement of post-MI ventricular function, and may represent an additional benefit of statin therapy.     

VEGF function for upregulation of endogenous PlGF expression during FGF-2-mediated therapeutic angiogenesis

Vascular endothelial growth factor (VEGF) is a major positive angiogenic factor. Using a murine hindlimb ischemia model, we previously showed that fibroblast growth factor-2 (FGF-2) enhances the expression of endogenous VEGF which highly contribute to the therapeutic effect of FGF-2 gene transfer. Recently, placental growth factor (PlGF) has been shown to play an important role in angiogenesis. However, the molecular mechanism of endogenous PlGF during FGF-2-mediated angiogenesis has not been elucidated. Severe hindlimb ischemia stimulated PlGF expression that was more strongly enhanced by FGF-2 gene transfer, and a blockade of PlGF activity diminished the recovery of blood flow by FGF-2-mediated angiogenesis. The PlGF expression in cultured endothelial cells was significantly enhanced by VEGF stimulation, but not by FGF-2. The upregulation of endogenous PlGF expression was significantly decreased by the inhibition of endogenous VEGF activity in vivo. Subsequent signal inhibition experiments revealed that the PKC, MEK, and possibly NF-κB-related pathways were essential in stimulating PlGF expression with VEGF, while p70S6K is the regulator for VEGF expression. These results indicate that the FGF-2-mediated enhancement of PlGF expression was dependent on VEGF function, and the FGF-2/VEGF axis participates in FGF-2-mediated angiogenesis indirectly via PlGF as well as directly.     

Placental productions and expressions of soluble endoglin, soluble fms-like tyrosine kinase receptor-1, and placental growth factor in normal and preeclamptic pregnancies

CONTEXT: Increased production of antiangiogenic factors soluble endoglin (sEng) and soluble fms-like tyrosine kinase receptor-1 (sFlt-1) by the placenta contributes to the pathophysiology in preeclampsia (PE). OBJECTIVE: Our objective was to determine the differences in endoglin (Eng), fms-like tyrosine kinase receptor-1 (Flt-1), and placental growth factor (PlGF) expressions between normal and PE placentas and sEng, sFlt-1, and PlGF production by trophoblast cells (TC) cultured under lowered oxygen conditions. METHODS: TCs isolated from normal and PE placentas were cultured under regular (5% CO2/air) and lowered (2% O2/5% CO2/93% N2) oxygen conditions. sEng, sFlt-1, and PlGF productions were determined by ELISA. Protein expressions for Eng, Flt-1, and PlGF in the placental tissues were accessed by immunohistochemical staining and Western blot analysis. Deglycosylated Eng, Flt-1, and PlGF protein expressions in placental tissues were also examined. RESULTS: PE TCs produced significantly more sEng, sFlt-1, and PlGF compared with those from normal TCs (P < 0.05). Under lowered oxygen conditions, PE TCs, but not normal TCs, released more sEng and sFlt-1. In contrast, both normal and PE TCs released less PlGF (P < 0.05). Enhanced expressions of Eng and Flt-1, as well as glycosylated Eng and Flt-1, were observed in PE placentas. Immunoblot also revealed that TCs released glycosylated sFlt-1, but not sEng, in culture. CONCLUSIONS: PE TCs produce more sEng, sFlt-1, and PlGF than normal TCs. Lowered oxygen conditions promote sEng and sFlt-1, but reduce PlGF, productions by PE TCs. More glycosylated sEng and sFlt-1 are present in PE placentas. Trophoblasts release glycosylated sFlt-1, but unglycosylated sEng, in culture.     

Imbalanced Angiogenesis in Pregnancies Complicated by SARS-CoV-2 Infection

COVID-19 and preeclampsia (preE) share the ANG-II mediated endothelial dysfunction, resulting from a significant dysregulation of RAS and an imbalanced proportion of anti-angiogenic and pro-angiogenic soluble plasmatic factors. Of note, an increased incidence of preE has been reported among COVID-19-infected mothers compared to the general pregnant population. The two most promising angiogenic markers are the soluble fms-like tyrosine kinase receptor-1 (sFlt-1), the major antiangiogenic factor, and the placental growth factor (PlGF), a powerful angiogenic factor. Since these markers have proven useful in the prediction, diagnosis, and severity of preE, this study aimed to evaluate their maternal serum levels in pregnancies complicated by SARS-CoV-2 infection and to assess their potential use to guide the management of these women. A retrospective analysis of SARS-CoV-2-positive pregnant women was performed. The serum levels of sFlt-1 and PlGF were collected at the diagnosis of SARS-CoV-2 infection at the hospital, before the beginning of steroid/hydroxychloroquine and/or antithrombotic therapy. The sFlt-1/PlGF ratio was stratified using cut-off values clinically utilized in the diagnosis and prediction of preE (low < 38, intermediate 38–85/110* and high >85/110*, * if before or after the 34th week of gestation). A total of 57 women were included, of whom 20 (35%) had signs and symptoms of COVID-19 at hospital presentation and 37 (65%) were asymptomatic. None were vaccinated. The mean gestational age at diagnosis of SARS-CoV-2 infection was 32 weeks in symptomatic patients and 37 weeks and 5 days in asymptomatic ones (p = 0.089). sFlt-1 serum levels were higher in SARS-CoV-2 positive asymptomatic patients compared to women with COVID-19 related symptoms (4899 ± 4357 pg/mL vs. 3187 ± 2426 pg/mL, p = 0.005). sFlt-1/PlGF at admission was <38 in 18 of the 20 symptomatic women (90%) compared to 22 (59%) of the asymptomatic patients (p = 0.018). Of note, two of the three women admitted to the intensive care unit had a very low ratio (<2). In turn, rates of patients with sFlt-1/PlGF at admission > 85/110 were not significantly different between the two groups: 11% in asymptomatic patients (4/37) vs. none of the symptomatic patients (p = 0.286), and all of them presented a placental dysfunction, like preE (n = 1) and FGR (n = 3). Of note, there were no stillbirths or maternal or neonatal deaths among symptomatic patients; also, no cases of preE, FGR, or small for gestational age neonates were diagnosed. In conclusion, our data suggest that SARS-CoV-2 infection during pregnancy could influence the angiogenic balance. A significant pathological alteration of the sFlt-1/PlGF ratio cannot be identified during the symptomatic phase; however, if left untreated, SARS-CoV-2 infection could potentially trigger placental dysfunction.     

The relationship between circulating endothelin-1, soluble fms-like tyrosine kinase-1 and soluble endoglin in preeclampsia

Placental overproduction of anti-angiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng) has a key role in the development of preeclampsia (PE). Circulating endothelin-1 (ET-1) levels are also elevated in PE. In this study, we investigated the correlation between ET-1 and sFlt-1, placental growth factor (PlGF), sEng levels during uncomplicated normotensive pregnancy and PE. A total of 218 pregnant primigravid women were enrolled: 110 with PE and 108 uncomplicated normotensive pregnancies. PE was defined as new onset of elevated blood pressure (BP) >140/90?mm?Hg and ≥2+ proteinuria on two occasions after 20 weeks of gestation in previously normotensive pregnant women. Circulating ET-1, sFlt-1, sEng and PlGF levels were estimated using enzyme immunoassays, and correlation between variables was ascertained. Women with PE showed higher levels of sFlt-1 (41.5±15.7 vs 6.15±3.4?ng?ml(-1), P<0.001), sEng (84.9±38.8 vs 13.2±6.3?ng?ml(-1), P<0.001), ET-1 (1.52±0.55 vs 0.88±0.35 pg?ml(-1), P<0.001) and sFlt-1:PlGF ratio (591.1±468.4 vs 18.3±2.1, P<0.001); and lower levels of PlGF (96.3±47.2 vs 497.6±328.2 pg?ml(-1), P<0.001). BP levels showed an independent relationship with sFlt-1:PlGF ratio in normotensive pregnant women and with sFlt-1:PlGF ratio and ET-1 in PE. sFlt-1 and sFlt-1:PlGF ratio correlated with proteinuria. ET-1 correlated significantly with sFlt-1, sEng and sFlt-1:PlGF ratio in PE. Our results show an association between elevation of sFlt-1 and sEng and ET-1 in the maternal circulation in PE, and strengthen the possibility that ET-1 may be a mediator in genesis of PE syndrome secondary to anti-angiogenic factors released by the placenta.     

Elevated placental soluble vascular endothelial growth factor receptor-1 inhibits angiogenesis in preeclampsia

Preeclampsia is an inflammatory disorder in which serum levels of vascular endothelial growth factor (VEGF) and its soluble receptor-1 (sVEGFR-1, also known as sFlt-1) are elevated. We hypothesize that VEGF and placenta growth factor (PlGF) are dysregulated in preeclampsia due to high levels of sVEGFR-1, which leads to impaired placental angiogenesis. Analysis of supernatants taken from preeclamptic placental villous explants showed a four-fold increase in sVEGFR-1 than normal pregnancies, suggesting that villous explants in vitro retain a hypoxia memory reflecting long-term fetal programming. The relative ratios of VEGF to sVEGFR-1 and PlGF to sVEGFR-1 released from explants decreased by 53% and 70%, respectively, in preeclampsia compared with normal pregnancies. Exposure of normal villous explants to hypoxia increased sVEGFR-1 release compared with tissue normoxia (P<0.001), as did stimulation with tumor necrosis factor-alpha (P<0.01). Conditioned medium (CM) from normal villous explants induced endothelial cell migration and in vitro tube formation, which were both attenuated by pre-incubation with exogenous sVEGFR-1 (P<0.001). In contrast, endothelial cells treated with preeclamptic CM showed substantially reduced angiogenesis compared with normal CM (P<0.001), which was not further decreased by the addition of exogenous sVEGFR-1, indicating a saturation of the soluble receptor. Removal of sVEGFR-1 by immunoprecipitation from preeclamptic CM significantly restored migration (P<0.001) and tube formation (P<0.001) to levels comparable to that induced by normal CM, demonstrating that elevated levels of sVEGFR-1 in preeclampsia are responsible for inhibiting angiogenesis. Our finding demonstrates the dysregulation of the VEGF/PlGF axis in preeclampsia and offers an entirely new therapeutic approach to its treatment.     

Maternal imbalance between pro-angiogenic and anti-angiogenic factors in HIV-infected women with pre-eclampsia

Abstract

Angiogenic imbalance contributes to the development of preeclampsia. We evaluated the protein expression of the proangiogenic placental growth factor (PlGF) and transforming growth factor beta 1 (TGF-β₁) compared with the anti-angiogenic soluble fms-like tyrosine kinase receptor (sFlt1) and soluble endoglin (sEng) in HIV-infected normotensive and pre-eclamptic pregnancies.Blood was obtained from 110 pregnant women, enrolled in four groups, namely, HIV-negative normotensives (27); HIV-positive normotensives (31); HIV-negative pre-eclamptics (27) and HIV-positive pre-eclamptics (25), and was used to measure PlGF, TGF-β1, sFlt1 and sEng levels.Increased sFlt1 and sEng levels were associated with the pre-eclamptics (HIV negative and positive) compared with their counterparts. Decreased PlGF levels were observed between the HIV-negative pre-eclamptics versus HIV-negative normotensives, but levels differed significantly (p = 0.02) among the normotensives (HIV negative and positive). TGF-β₁ remained unchanged across all groups. Higher sEng/TGF-β₁ ratios were associated with the pre-eclamptics (HIV negative and positive) compared with their counterparts. This study demonstrated increased sFlt1 and sEng levels in pre-eclamptic compared with normotensive pregnancies, irrespective of the HIV status.     

Role of complement component C1q in the onset of preeclampsia in mice

Preeclampsia (PE) is a life-threatening, pregnancy-induced disease and a leading cause of maternal and fetal morbidity and mortality. Despite considerable research, the causes of PE remain unclear, and there is no effective treatment. Studies in animal models that resemble this complex pregnancy-related disorder may help to identify possible therapies for PE. Complement component C1q has an important role in trophoblast migration, spiral arteries remodeling, and normal placentation. Here we show that pregnant C1q-deficient (C1q(-/-)) mice recapitulate the key features of human PE: hypertension, albuminuria, endotheliosis, decreased placental vascular endothelial growth factor (VEGF) and elevated levels of soluble VEGF receptor 1 (sFlt-1) that correlate with increased fetal death. In addition, decreased blood flow and increased oxidative stress are observed in placentas from C1q(-/-) mice. Treatment of C1q(-/-) mice with pravastatin restored trophoblast invasiveness, placental blood flow, and angiogenic balance and, thus, prevented the onset of PE. Serum-soluble receptors for VEGF-1 levels were reduced and placental VEGF levels were significantly increased in C1q(-/-) mice treated with pravastatin compared with untreated C1q(-/-) mice (VEGF: 1067±171 versus 419±194 pg/mL; P<0.01). Pravastatin treatment reduced hypertension (change in mean arterial pressure: 1±1 versus 18±3 mm Hg in C1q(-/-) untreated mice), and albuminuria (of creatinine) was reduced from 820±175 to 117±45 μg/mg (both P<0.01). Renal damage and endothelial dysfunction were significantly attenuated with pravastatin. This model that highlights the causative role of impaired trophoblast invasion in the pathogenesis of PE allowed us to identify pravastatin as a good therapeutic option to prevent PE.     

Jumonji domain-containing protein 6 (Jmjd6) is required for angiogenic sprouting and regulates splicing of VEGF-receptor 1

JmjC domain-containing proteins play a crucial role in the control of gene expression by acting as protein hydroxylases or demethylases, thereby controlling histone methylation or splicing. Here, we demonstrate that silencing of Jumonji domain-containing protein 6 (Jmjd6) impairs angiogenic functions of endothelial cells by changing the gene expression and modulating the splicing of the VEGF-receptor 1 (Flt1). Reduction of Jmjd6 expression altered splicing of Flt1 and increased the levels of the soluble form of Flt1, which binds to VEGF and placental growth factor (PlGF) and thereby inhibits angiogenesis. Saturating VEGF or PlGF or neutralizing antibodies directed against soluble Flt1 rescued the angiogenic defects induced by Jmjd6 silencing. Jmjd6 interacts with the splicing factors U2AF65 that binds to Flt1 mRNA. In conclusion, Jmjd6 regulates the splicing of Flt1, thereby controlling angiogenic sprouting.     

Threshold of soluble fms-like tyrosine kinase 1/placental growth factor ratio for the imminent onset of preeclampsia

It has not been clarified whether thresholds of soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF), soluble endoglin, and the sFlt-1/PlGF ratio for the imminent onset of preeclampsia (PE) exist. We hypothesized that onset thresholds for the imminent onset of PE could be determined by the distributions of these 4 markers just after the onset of PE. Study subjects were 51 PE after the onset of PE; 36 of PE, 20 of gestational hypertension, 142 of a small-for-gestational-age infant, and 400 of normal pregnant controls at 19 to 25 and 27 to 31 weeks of gestation in a prospective cohort study. The current data supported our hypothesis that onset thresholds of sFlt-1 and the sFlt-1/PlGF ratio exist. The onset thresholds of the sFlt-1/PlGF at 26 to 31 weeks of gestation were useful for detecting imminent PE with the onset at <36 weeks of gestation, showing sensitivity of 0.36 and a positive likelihood ratio and 95th percent CIs of 38 (11-132); when positive, PE occurred at 2.2±0.6 weeks (range: 1.4-3.0 weeks) after the measurement of the sFlt-1/PlGF ratio. The combination of sFlt-1 at 26 to 31 weeks of gestation, past history of gestational hypertension or PE, prepregnancy body mass index, and mean blood pressure at 16 to 23 weeks of gestation was useful for detecting PE with onset of <36 weeks of gestation, showing sensitivity of 0.82, and a positive likelihood ratio (95% CI) of 42 (20-88). In conclusion, the onset threshold of sFlt-1/PlGF existed and might be useful for detecting the imminent onset of PE.     

Expression of soluble vascular endothelial growth factor receptor-1 and placental growth factor in fetal growth restriction cases and intervention effect of tetramethylpyrazine

Objective:To investigate the expression of soluble vascular endothelial growth factor receptor-1(sFlt-1) and placental growth factor(PLGF) in the fetal growth restriction(FGR) cases and the intervention mechanism of tetramelhylpyrazine.Methods:A total of 60 fetal growth restriction cases that admitted lo our hospital were randomly divided into ligustrazine intervention group(group A) and nutritional support group(group B).A total of 50 healthy pregnant women were also enrolled as control group(group C).Expression level of maternal serum sFlt1,FLGF and fetal growth parameters including HC,AC,FL,BPD,EFW as well as placenta PLGF,sFlt-1 mRNA expression were recorded and compared among the three groups.A total of 15 SD rats were selected and were divided into lliree groups.TMP group,alcohol and tobacco group and blank control group.Three groups of rats were dissected on the twentieth day of gestation.Result:Expression level of sFlt-1 and PLGF in group A was not significantly different from that of group C(P0.05):but significant difference in SFlt1 and PLGF expression level was observed between group C and group B(P0.05).Before treatment.HC,AC,FL,BPD and EFW of group A and group B were significant lower than those of group C.hut after treatment,those parameters in group A were significantly improved(P0.05).In the animal experiment there was no significant difference in sFlt-1 between treatment group and FGR group without treatment or control group(P0.05).There was significant difference in PLGF between FGR group with treatment and FGR group without treatment or control group(P0.01).Conclusions:PLGF level is decreased and sFlt-1 increased in patients suffered from fetal growth restriction,and FGR rats show increased sFlt-1 and decreased PLGF.thus they can be indicator of the fetal growth restriction.Ligustrazinc can effectively improve sFlt-1,PLGF expression level in fetal growth restriction cases,which can be used as treatment for FGR.     

Soluble Fms-like tyrosine kinase associated with preeclampsia in pregnancy in systemic lupus erythematosus

OBJECTIVE: Placental synthesis of soluble Fms-like tyrosine kinase (sFlt-1) is responsible for the increased level of serum sFlt-1 in preeclampsia. sFlt-1 binds to the receptor-binding domain of placental growth factor (PlGF) and vascular endothelial growth factor (VEGF), acting as an endogenous inhibitor of VEGF and PlGF signaling in endothelial cells. It has been hypothesized that increased circulating sFlt-1 contributes to the endothelial dysfunction, hypertension, and proteinuria of preeclampsia. We examined the association of sFlt-1 and preeclampsia in pregnancies in patients with systemic lupus erythematosus (SLE). METHODS: A case-control study was performed using stored serum samples. Cases were SLE pregnancies with later preeclampsia and controls were SLE pregnancies without later preeclampsia. RESULTS: The 52 SLE pregnancies occurred from 1998 to 2001. Nine (17%) pregnancies met the definition of preeclampsia and an additional 9 (17%) met the definition of superimposed preeclampsia. sFlt-1 concentration was significantly higher in SLE pregnancies with preeclampsia (1768 +/- 196 pg/ml) than in those without (1177 +/- 143 pg/ml) (p = 0.0185). CONCLUSION: Our study shows for the first time that sFlt-1 is associated with preeclampsia in patients with SLE, as previously shown in the general pregnancy population. This suggests that SLE pregnancies at risk for preeclampsia can be identified early in the pregnancy by sFlt-1, thus identifying them for high-risk obstetric referral and appropriate monitoring.     

Circulating leptin and angiogenic factors in preeclampsia patients

Leptin, one of adipocytokines, plays a wide range of important roles in reproductive biology. We have previously reported that low hypo-adiponectinemia might be involved in the pathophysiology of overweight preeclampsia (PE) patients. Moreover, recent reports have underscored the importance of circulating angiogenic factors in the pathophysiology of PE. Here, we examined whether leptin in conjunction with adiponectin and/or angiogenic factors plays some role in the pathophysiology of PE. We performed a cross-sectional study in 34 PE patients and normal pregnancies matched for gestational age and body mass index as controls. We measured serum concentrations of leptin, adiponectin, the angiogenic factors vascular endothelial growth factor (VEGF), placental growth factor, and the soluble VEGF receptors sFlt-1 and sFlk-1. We observed that leptin levels in PE patients were significantly higher compared with those in controls, but did not observe significant differences between normal- and overweight patients in both groups. We also showed a significant negative correlation between leptin and adiponectin in controls, but not in PE patients. There was a significant correlation between leptin and sFlt-1 in PE patients, while there were significant differences of body mass index, mean blood pressure and proteinuria between high and low leptin/sFlt-1 ratio group in PE patients. Moreover, there was a significant difference of leptin level between IUGR and normal growth group in PE patients. These results suggest that the circulating increased leptin might be derived mainly from the placenta and regulated by the placental hypoxic condition, whereas adiponectin might be derived mainly from adipose tissue; and that leptin might play some role through insulin resistance, autonomic activation, or direct effect on endothelium with other angiogenic factors in pathophysiology of PE compared with the exaggerated release of adiponectin from adipose tissue.     

Angiogenesis in myocardial infarction. An acute or chronic process?

BACKGROUND: In the acute phase of myocardial infarction (acute MI) marked endothelial damage occurs within the first 24h following thrombolysis with streptokinase. We investigated whether this is associated with a change in levels of vascular endothelial growth factor (VEGF, possibly marking angiogenesis) in the first 24h post thrombolysis compared to chronic MI patients (defined as MI>3 months previously). METHODS: We recruited 15 patients (nine male, mean age 59+/-SD 10 years) with first-presentation acute MI, who were given 1.5 million U streptokinase over 1h and aspirin 300mg orally as standard treatment. Plasma samples were taken prior to the start of thrombolysis, followed every 15 min for 1h, at 3h and finally at 24h post-thrombolysis. Baseline levels of measured indices in the acute MI patients were compared to two control groups: (i) 26 chronic MI patients (18 male, mean age 59.9+/-7.0 years); and (ii) 26 apparently healthy controls (17 male, mean age 59.6+/-14.1 years). Plasma VEGF and the soluble form of its receptor Flt-1 (sFlt-1) were measured by ELISA. RESULTS: Plasma levels of VEGF were significantly higher in patients with a history of chronic MI compared to patients with acute MI (P=0.007) and healthy controls (P=0.002) with similar levels between acute MI patients and healthy controls (P=0.755). Levels of sFlt-1 in the acute (P=0.013) and chronic (P<0.001) MI groups were lower compared to healthy controls. In the first 24h post-thrombolysis in the acute MI group, levels of sFlt-1 changed significantly (P=0.039), but there was no change in levels of VEGF (P=0.207). CONCLUSION: In the first 24h of acute MI, significant changes in levels of VEGF receptor sFlt-1, but not VEGF, are seen. Plasma VEGF and sFlt-1 levels are markedly changed in chronic MI patients, suggesting that the activation of angiogenesis in MI patients may be a delayed response.     

Molecular mechanisms of preeclampsia

Preeclampsia is a major cause of maternal, fetal and neonatal mortality worldwide. The mechanisms that initiate preeclampsia in humans have been elusive, but some parts of the puzzle have begun to come together. A key discovery in the field was the realization that its major phenotypes, such as hypertension and proteinuria, are due to excess circulating soluble fms-like tyrosine kinase-1 (sFlt-1, also referred to as sVEGFR-1). sFlt-1 is an endogenous anti-angiogenic protein that is made by the placenta and acts by neutralizing the pro-angiogenic proteins vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). More recently, soluble endoglin, another circulating anti-angiogenic protein was found to synergize with sFlt-1 and contribute to the pathogenesis of preeclampsia. Abnormalities in these circulating angiogenic proteins are not only present during clinical preeclampsia, but also antedate clinical symptoms by several weeks. This review will summarize our current understanding of the molecular mechanism of preeclampsia, with an emphasis on the recently characterized circulating anti-angiogenic proteins.     

Expression and function of vascular endothelial growth factor receptors (Flt-1 and Flk-1) in vascular adventitial fibroblasts

Vascular endothelial growth factor receptors (VEGFRs) are previously considered to exist exclusively in endothelial cells. However, little is known if the receptors are expressed in other non-endothelial cells. In this study, we measured activation of two VEGFRs, Flk-1 and Flt-1, and their biological functions in cultured adventitial fibroblasts and injured rat carotid injury arteries induced by balloon angioplasty. Our results indicated that Flt-1, but not Flk-1, existed in adventitial fibroblasts. Angiotensin II increased Flt-1 protein expression in a time- and concentration-dependent manner. Adventitial fibroblast migration stimulated by vascular endothelial growth factor (VEGF) and placental growth factor (PIGF) required Flt-1 expression. The Flt-1-induced adventitial fibroblast migration was blocked by anti-Flt-1 neutralizing antibody and soluble VEGFR1 protein (sFlt-1). However, Flt-1 activation did not enhance cell proliferation. In addition, Flt-1 expression was significantly increased in the neointima and adventitia in injured rat carotid arteries. We concluded that functional expression of Flt-1 in adventitial fibroblasts might be an important mediator in the pathogenesis of vascular remodeling after arterial injury.     

Overexpression of the soluble vascular endothelial growth factor receptor in preeclamptic patients: pathophysiological consequences

Several growth factors such as vascular endothelial growth factor (VEGF)-A and placental growth factor (PlGF) are involved in the placental vascular development. We investigated whether dysregulation in the VEGF family may explain the defective uteroplacental vascularization characterizing preeclampsia. We compared pregnancies complicated by early onset severe preeclampsia or intrauterine growth retardation to normal pregnancies. Maternal plasma, placentas, and placental bed biopsies were collected. The mRNA levels of VEGF-A, PlGF, and their receptors were quantified in placentas and placental beds. Levels of VEGF-A, PlGF, and soluble VEGF receptor (VEGFR) were assessed in maternal plasma. In compromised pregnancies, elevated levels of VEGF-A and VEGFR-1 mRNAs may reflect the hypoxic status of the placenta. On contrast, the membrane-bound VEGFR-1 was decreased in the placental bed of preeclamptic patients. Preeclampsia was associated with low levels of circulating PlGF and increased levels of total VEGF-A and soluble VEGFR-1. Free VEGF-A was undetectable in maternal blood. Immunohistochemical studies revealed that VEGF-A and PlGF were localized in trophoblastic cells. Altogether, our results suggest two different pathophysiological mechanisms associated with preeclampsia. The first one is related to an overproduction of competitive soluble VEGFR-1 that may lead to suppression of VEGF-A and PlGF effects. The second one is the down-regulation of its membrane bound form (VEGFR-1) in the placental bed, which may result in the defective uteroplacental development.