Endothelial growth factor therapy improves preeclampsia-like manifestations in a murine model induced by overexpression of sVEGFR-1

Bioflavonoid luteolin prevents sFlt-1 release via HIF-1α inhibition in cultured human placenta

Preeclampsia (PE) is a serious hypertensive complication of pregnancy and is a leading cause of maternal death and major contributor to maternal and perinatal morbidity, including establishment of long-term complications. The continued prevalence of PE stresses the need for identification of novel treatments which can target prohypertensive factors implicated in the disease pathophysiology, such as soluble fms-like tyrosine kinase 1 (sFlt-1). We set out to identify novel compounds to reduce placental sFlt-1 and determine whether this occurs via hypoxia-inducible factor (HIF)-1α inhibition. We utilized a commercially available library of natural compounds to assess their ability to reduce sFlt-1 release from primary human placental cytotrophoblast cells (CTBs). Human placental explants from normotensive (NT) and preeclamptic (PE) pregnancies were treated with varying concentrations of luteolin. Protein and mRNA expression of sFlt-1 and upstream mediators were evaluated using ELISA, western blot, and real-time PCR. Of the natural compounds examined, luteolin showed the most potent inhibition of sFlt-1 release, with >95% reduction compared to vehicle-treated. Luteolin significantly inhibited sFlt-1 in cultured placental explants compared to vehicle-treated in a dose- and time-dependent manner. Additionally, significant decreases in HIF-1α expression were observed in luteolin-treated explants, suggesting a mechanism for sFlt-1 downregulation. The ability of luteolin to inhibit HIF-1α may be mediated through the Akt pathway, as inhibitors to Akt and its upstream regulator phosphatidylinositol-3 kinase (PI3K) resulted in significant HIF-1α reduction. Luteolin reduces anti-angiogenic sFlt-1 through inhibition of HIF-1α, making it a novel candidate for the treatment of PE.

Novel Technologies for Target Delivery of Therapeutics to the Placenta during Pregnancy: A Review

Uterine spiral artery remodeling is essential for placental perfusion and fetal growth and, when impaired, results in placental ischemia and pregnancy complications, e.g., fetal growth restriction, preeclampsia, premature birth. Despite the high incidence of adverse pregnancies, current treatment options are limited. Accordingly, research has shifted to the development of gene therapy technologies that provide targeted delivery of "payloads" to the placenta while limiting maternal and fetal exposure. This review describes the current strategies, including placental targeting peptide-bound liposomes, nanoparticle or adenovirus constructs decorated with specific peptide sequences and placental gene promoters delivered via maternal IV injection, directly into the placenta or the uterine artery, as well as noninvasive site-selective targeting of regulating genes conjugated with microbubbles via contrast-enhanced ultrasound. The review also provides a perspective on the effectiveness of these technologies in various animal models and their practicability and potential use for targeted placental delivery of therapeutics and genes in adverse human pregnancies affected by placental dysfunction.

Regulation of Uterine Spiral Artery Remodeling: a Review

Extravillous trophoblast remodeling of the uterine spiral arteries is essential for promoting blood flow to the placenta and fetal development, but little is known about the regulation of this process. A defect in spiral artery remodeling underpins adverse conditions of human pregnancy, notably early-onset preeclampsia and fetal growth restriction, which result in maternal and fetal morbidity and mortality. Many in vitro studies have been conducted to determine the ability of growth and other factors to stimulate trophoblast cells to migrate across a synthetic membrane. Clinical studies have investigated whether the maternal levels of various factors are altered during abnormal human pregnancy. Animal models have been established to assess the ability of various factors to recapitulate the pathophysiological symptoms of preeclampsia. This review analyzes the results of the in vitro, clinical, and animal studies and describes a nonhuman primate experimental paradigm of defective uterine artery remodeling to study the regulation of vessel remodeling.

Pravastatin for preeclampsia: From animal to human

Preeclampsia is characterized by the emergence of hypertension and proteinuria after 20 weeks of pregnancy, and it threatens both maternal and fetal lives if it proceeds unabated. Despite numerous studies, thus far the only fundamental therapy for preeclampsia is termination of pregnancy, leading to preterm birth. Furthermore, preeclamptic women are reported to be at risk for cardiovascular diseases for 10 years after delivery. Therefore, preventative and therapeutic strategies for preeclampsia are required. Recently, statins have been reported to improve the regeneration of vascular endothelium, and pravastatin has attracted attention as a potential preventative or therapeutic candidate for preeclampsia. Pravastatin has been demonstrated to have preventative effects in preeclampsia model mice, and a large volume of human data from pregnant women taking statins supports the safety of these drugs. Moreover, small clinical trials have reported that pravastatin has strong preventative or therapeutic effects on preeclampsia and it has the potential to improve the prognosis of pregnant women, fetuses and neonates affected by this condition.

Vascular Endothelial Growth Factor-121 Administration Mitigates Halogen Inhalation-Induced Pulmonary Injury and Fetal Growth Restriction in Pregnant Mice

Background Circulating levels of sFLT-1 (soluble fms-like tyrosine kinase 1), the extracellular domain of vascular endothelial growth factor (VEGF) receptor 1, and its ratio to levels of placental growth factor are markers of the occurrence and severity of preeclampsia. Methods and Results C57BL/6 pregnant mice on embryonic day 14.5 (E14.5), male, and non-pregnant female mice were exposed to air or to Br2 at 600 ppm for 30 minutes and were treated with vehicle or with VEGF-121 (100 μg/kg, subcutaneously) daily, starting 48 hours post-exposure. Plasma, bronchoalveolar lavage fluid, lungs, fetuses, and placentas were collected 120 hours post-exposure. In Br2-exposed pregnant mice, there was a time-dependent and significant increase in plasma levels of sFLT-1 which correlated with increases in mouse lung wet/dry weights and bronchoalveolar lavage fluid protein content. Supplementation of exogenous VEGF-121 improved survival and weight gain, reduced lung wet/dry weights, decreased bronchoalveolar lavage fluid protein levels, enhanced placental development, and improved fetal growth in pregnant mice exposed to Br2. Exogenous VEGF-121 administration had no effect in non-pregnant mice. Conclusions These results implicate inhibition of VEGF signaling driven by sFLT-1 overexpression as a mechanism of pregnancy-specific injury leading to lung edema, maternal mortality, and fetal growth restriction after bromine gas exposure.

Vascular Endothelial Growth Factor Delivery to Placental Basal Plate Promotes Uterine Artery Remodeling in the Primate

Extravillous trophoblast (EVT) uterine artery remodeling (UAR) promotes placental blood flow, but UAR regulation is unproven. Elevating estradiol (E2) in early baboon pregnancy suppressed UAR and EVT vascular endothelial growth factor (VEGF) expression, but this did not prove that VEGF mediated this process. Therefore, our primate model of prematurely elevating E2 and contrast-enhanced ultrasound cavitation of microbubble (MB) carriers was used to deliver VEGF DNA to the placental basal plate (PBP) to establish the role of VEGF in UAR. Baboons were treated on days 25 to 59 of gestation (term, 184 days) with E2 alone or with E2 plus VEGF DNA-conjugated MBs briefly infused via a maternal peripheral vein on days 25, 35, 45, and 55. At each of these times an ultrasound beam was directed to the PBP to collapse the MBs and release VEGF DNA. VEGF DNA-labeled MBs per contrast agent was localized in the PBP but not the fetus. Remodeling of uterine arteries >25 µm in diameter on day 60 was 75% lower (P < 0.001) in E2-treated (7% ± 2%) than in untreated baboons (30% ± 4%) and was restored to normal by E2/VEGF. VEGF protein levels (signals/nuclear area) within the PBP were twofold lower (P < 0.01) in E2-treated (4.2 ± 0.9) than in untreated (9.8 ± 2.8) baboons and restored to normal by E2/VEGF (11.9 ± 1.6), substantiating VEGF transfection. Thus, VEGF gene delivery selectively to the PBP prevented the decrease in UAR elicited by prematurely elevating E2 levels, establishing the role of VEGF in regulating UAR in vivo during primate pregnancy.

Pro-angiogenic therapeutics for preeclampsia

Preeclampsia is a pregnancy-induced hypertensive disorder resulting from abnormal placentation, which causes factors such as sFlt-1 to be released into the maternal circulation. Though anti-hypertensive drugs and magnesium sulfate can be given in an effort to moderate symptoms, the syndrome is not well controlled. A hallmark characteristic of preeclampsia, especially early-onset preeclampsia, is angiogenic imbalance resulting from an inappropriately upregulated sFlt-1 acting as a decoy receptor binding vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), reducing their bioavailability. Administration of sFlt-1 leads to a preeclamptic phenotype, and several models of preeclampsia also have elevated levels of plasma sFlt-1, demonstrating its role in driving the progression of this disease. Treatment with either VEGF or PlGF has been effective in attenuating hypertension and proteinuria in multiple models of preeclampsia. VEGF, however, may have overdose toxicity risks that have not been observed in PlGF treatment, suggesting that PlGF is a potentially safer therapeutic option. This review discusses angiogenic balance as it relates to preeclampsia and the studies which have been performed in order to alleviate the imbalance driving the maternal syndrome.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

The Citrulline Recycling Pathway Sustains Cardiovascular Function in Arginine-Depleted Healthy Mice, but Cannot Sustain Nitric Oxide Production during Endotoxin Challenge

Background

The recycling of citrulline by argininosuccinate synthase 1 (ASS1) and argininosuccinate lyase (ASL) is crucial to maintain arginine availability and nitric oxide (NO) production. Pegylated arginine deiminase (ADI-PEG20) is a bacterial enzyme used to deplete circulating arginine.

Objective

The goal of this research was to test the hypothesis that citrulline is able to sustain intracellular arginine availability for NO production in ADI-PEG20 arginine-depleted mice.

Methods

Six- to 8-wk-old male C57BL/6J mice injected with ADI-PEG20 (5 IU) or saline (control) were used in 4 different studies. Arginine, citrulline, and NO kinetics were determined by using stable isotopes in unchallenged (study 1) and endotoxin-challenged (study 2) mice. Blood pressure was determined by telemetry for 6 d after ADI-PEG20 administration (study 3), and vasomotor activity and ASS1 and ASL gene expression were determined in mesenteric arteries collected from additional mice (study 4).

Results

ADI-PEG20 administration resulted in arginine depletion (<1 compared with 111 ± 37 µmol/L) but in greater plasma citrulline concentrations (900 ± 123 compared with 76 ± 8 µmol/L; P < 0.001) and fluxes (402 ± 17 compared with 126 ± 4 µmol ⋅ kg-1 ⋅ h-1; P < 0.001) compared with controls. Endotoxin-challenged ADI-PEG20-treated mice produced less NO than controls (13 ± 1 compared with 27 ± 2 µmol ⋅ kg-1 ⋅ h-1; P < 0.001). No differences (P > 0.50) were observed for cardiovascular variables (heart rate, blood pressure) between ADI-PEG20-treated and control mice. Furthermore, no ex vivo vasomotor differences were observed between the 2 treatments. ADI-PEG20 administration resulted in greater gene expression of ASS1 (∼3-fold) but lower expression of ASL (-30%).

Conclusion

ADI-PEG20 successfully depleted circulating arginine without any effect on cardiovascular endpoints in healthy mice but limited NO production after endotoxin challenge. Therefore, the citrulline recycling pathway can sustain local arginine availability independently from circulating arginine, satisfying the demand of arginine for endothelial NO production; however, it is unable to do so when a high demand for arginine is elicited by endotoxin.

A Maternally Sequestered, Biopolymer-Stabilized Vascular Endothelial Growth Factor (VEGF) Chimera for Treatment of Preeclampsia

BACKGROUND

Preeclampsia is a hypertensive syndrome that complicates 3% to 5% of pregnancies in the United States. Preeclampsia originates from an improperly vascularized and ischemic placenta that releases factors that drive systemic pathophysiology. One of these factors, soluble fms-like tyrosine kinase-1, is believed to sequester vascular endothelial growth factor (VEGF), leading to systemic endothelial dysfunction and hypertension. With the goal of targeting soluble fms-like tyrosine kinase-1 while simultaneously preventing fetal exposure to VEGF, we fused VEGF to elastin-like polypeptide, a biopolymer carrier that does not cross the placental barrier (ELP-VEGF).

METHODS AND RESULTS

ELP-VEGF restored in vitro endothelial cell tube formation in the presence of plasma from placental ischemic rats. Long-term administered ELP-VEGF in pregnant rats accumulated in maternal kidneys, aorta, liver, and placenta, but the protein was undetectable in the pups when administered at therapeutic doses in dams. Long-term administration of ELP-VEGF in a placental ischemia rat model achieved dose-dependent attenuation of hypertension, with blood pressure equal to sham controls at a dose of 5 mg/kg per day. ELP-VEGF infusion increased total plasma soluble fms-like tyrosine kinase-1 levels but dramatically reduced free plasma soluble fms-like tyrosine kinase-1 and induced urinary excretion of nitrate/nitrite, indicating enhanced renal nitric oxide signaling. ELP-VEGF at up to 5 mg/kg per day had no deleterious effect on maternal or fetal body weight. However, dose-dependent adverse events were observed, including ascites production and neovascular tissue encapsulation around the minipump.

CONCLUSIONS

ELP-VEGF has the potential to treat the preeclampsia maternal syndrome, but careful dosing and optimization of the delivery route are necessary.

Recombinant vascular endothelial growth factor 121 injection for the prevention of fetal growth restriction in a preeclampsia mouse model

AIM

To discover the potential role of recombinant VEGF121 (rVEGF121) injection for the prevention of fetal growth restriction in a preeclampsia (PE) mouse model (Mus musculus).

SUBJECTS AND METHODS

This is an experimental study of 30 pregnant mice that were randomly divided into three groups: normal, PE, and PE with rVEGF121 injection. The PE mouse model was created by injecting anti Qa-2 10 ng iv, which is deleterious to Qa-2 expression (homologous to HLA-G), from the first to the fourth day of gestation. PE was validated by measuring serum levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor(PIGF) and also by kidney histopathology. Recombinant VEGF121 was given on the ninth day until the 11th day of pregnancy; mice were terminated on the 16th day. Fetal weights were acquired with a Denver analytical balance. Serum levels of sFlt-1 and PlGF were measured using enzyme-linked immunosorbent assay (ELISA). The data were statistically analyzed via analysis of variance (ANOVA).

RESULTS

On average, fetal birth weight was 0.7150 g in the normal group, 0.4936 g in the PE group, and 0.6768 g in the PE with rVEGF121 injection group. ANOVA showed significant growth restriction in the PE group (P=0.006), confirming the use of anti Qa-2 as a suitable PE model. Kidney histopathology results, sFlt-1 levels, and PlGF levels also demonstrated that anti Qa-2 consistently conferred hallmarks of PE in mice. Vascular endothelial growth factor (VEGF) injection prevented fetal growth restriction; comparable fetal weights were observed between the PE model with VEGF treatment and the normal group (P=0.610) but differed from the untreated PE group (P=0.021).

CONCLUSIONS

Injection of rVEGF121 has the potential to prevent fetal growth restriction in a newly proposed PE mouse model.

Classical Complement Pathway Activation in the Kidneys of Women With Preeclampsia

A growing body of evidence suggests that complement dysregulation plays a role in the pathogenesis of preeclampsia. The kidney is one of the major organs affected in preeclampsia. Because the kidney is highly susceptible to complement activation, we hypothesized that preeclampsia is associated with renal complement activation. We performed a nationwide search for renal autopsy material in the Netherlands using a computerized database (PALGA). Renal tissue was obtained from 11 women with preeclampsia, 25 pregnant controls, and 14 nonpregnant controls with hypertension. The samples were immunostained for C4d, C1q, mannose-binding lectin, properdin, C3d, C5b-9, IgA, IgG, and IgM. Preeclampsia was significantly associated with renal C4d-a stable marker of complement activation-and the classical pathway marker C1q. In addition, the prevalence of IgM was significantly higher in the kidneys of the preeclamptic women. No other complement markers studied differed between the groups. Our findings in human samples were validated using a soluble fms-like tyrosine kinase 1 mouse model of preeclampsia. The kidneys in the soluble fms-like tyrosine kinase 1-injected mice had significantly more C4 deposits than the control mice. The association between preeclampsia and renal C4d, C1q, and IgM levels suggests that the classical complement pathway is involved in the renal injury in preeclampsia. Moreover, our finding that soluble fms-like tyrosine kinase 1-injected mice develop excess C4 deposits indicates that angiogenic dysregulation may play a role in complement activation within the kidney. We suggest that inhibiting complement activation may be beneficial for preventing the renal manifestations of preeclampsia.

Full-length human placental sFlt-1-e15a isoform induces distinct maternal phenotypes of preeclampsia in mice

OBJECTIVE

Most anti-angiogenic preeclampsia models in rodents utilized the overexpression of a truncated soluble fms-like tyrosine kinase-1 (sFlt-1) not expressed in any species. Other limitations of mouse preeclampsia models included stressful blood pressure measurements and the lack of postpartum monitoring. We aimed to 1) develop a mouse model of preeclampsia by administering the most abundant human placental sFlt-1 isoform (hsFlt-1-e15a) in preeclampsia; 2) determine blood pressures in non-stressed conditions; and 3) develop a survival surgery that enables the collection of fetuses and placentas and postpartum (PP) monitoring.

METHODS

Pregnancy status of CD-1 mice was evaluated with high-frequency ultrasound on gestational days (GD) 6 and 7. Telemetry catheters were implanted in the carotid artery on GD7, and their positions were verified by ultrasound on GD13. Mice were injected through tail-vein with adenoviruses expressing hsFlt-1-e15a (n = 11) or green fluorescent protein (GFP; n = 9) on GD8/GD11. Placentas and pups were delivered by cesarean section on GD18 allowing PP monitoring. Urine samples were collected with cystocentesis on GD6/GD7, GD13, GD18, and PPD8, and albumin/creatinine ratios were determined. GFP and hsFlt-1-e15a expression profiles were determined by qRT-PCR. Aortic ring assays were performed to assess the effect of hsFlt-1-e15a on endothelia.

RESULTS

Ultrasound predicted pregnancy on GD7 in 97% of cases. Cesarean section survival rate was 100%. Mean arterial blood pressure was higher in hsFlt-1-e15a-treated than in GFP-treated mice (∆MAP = 13.2 mmHg, p = 0.00107; GD18). Focal glomerular changes were found in hsFlt-1-e15a -treated mice, which had higher urine albumin/creatinine ratios than controls (109.3 ± 51.7 μg/mg vs. 19.3 ± 5.6 μg/mg, p = 4.4 x 10(-2); GD18). Aortic ring assays showed a 46% lesser microvessel outgrowth in hsFlt-1-e15a-treated than in GFP-treated mice (p = 1.2 x 10(-2)). Placental and fetal weights did not differ between the groups. One mouse with liver disease developed early-onset preeclampsia-like symptoms with intrauterine growth restriction (IUGR).

CONCLUSIONS

A mouse model of late-onset preeclampsia was developed with the overexpression of hsFlt-1-e15a, verifying the in vivo pathologic effects of this primate-specific, predominant placental sFlt-1 isoform. HsFlt-1-e15a induced early-onset preeclampsia-like symptoms associated with IUGR in a mouse with a liver disease. Our findings support that hsFlt-1-e15a is central to the terminal pathway of preeclampsia, and it can induce the full spectrum of symptoms in this obstetrical syndrome.

In vivo experiments reveal the good, the bad and the ugly faces of sFlt-1 in pregnancy

Objective

Soluble fms-like tyrosine kinase (sFlt)-1-e15a, a primate-specific sFlt-1-isoform most abundant in the human placenta in preeclampsia, can induce preeclampsia in mice. This study compared the effects of full-length human (h)sFlt-1-e15a with those of truncated mouse (m)sFlt-1(1-3) used in previous preeclampsia studies on pregnancy outcome and clinical symptoms in preeclampsia.

Methods

Mice were injected with adenoviruses or fiber-mutant adenoviruses overexpressing hsFlt-1-e15a, msFlt-1(1-3) or control GFP under the CMV or CYP19A1 promoters on gestational day 8 (GD8) and GD11. Placentas and pups were delivered by cesarean section, and dams were monitored postpartum. Blood pressure was telemetrically recorded. Urine samples were collected with cystocentesis and examined for albumin/creatinine ratios. Tissue specimens were evaluated for transgene as well as endogenous mFlt-1 and msFlt-1-i13 expression. H&E-, Jones- and PAS-stained kidney sections were histopathologically examined. Placental GFP expression and aortic ring assays were investigated with confocal microscopy.

Results

Mean arterial blood pressure (MAP) was elevated before delivery in hsFlt-1-e15a-treated mice compared to controls (GD18: ΔMAP = 7.8 mmHg, p = 0.009), while ΔMAP was 12.8 mmHg (GD18, p = 0.005) in msFlt-1(1-3)-treated mice. Urine albumin/creatinine ratio was higher in hsFlt-1-e15a-treated mice than in controls (GD18, p = 0.04; PPD8, p = 0.03), and msFlt-1(1-3)-treated mice had marked proteinuria postpartum (PPD8, p = 4×10⁻⁵). Focal glomerular changes were detected in hsFlt-1-e15a and msFlt-1(1-3)-treated mice. Aortic ring microvessel outgrowth was decreased in hsFlt-1-e15a (p = 0.007) and msFlt-1(1-3)-treated (p = 0.02) mice. Full-length msFlt-1-i13 expression was unique for the placenta. In hsFlt-1-e15a-treated mice, the number of pups (p = 0.046), total weight of living pups (p = 0.04) and maternal weights (p = 0.04) were higher than in controls. These differences were not observed in truncated msFlt-1(1-3)-treated mice.

Conclusions

Truncated msFlt-1(1-3) simulated the preeclampsia-promoting effects of full-length hsFlt-1. MsFlt-1(1-3) had strong effect on maternal endothelium but not on placentas and embryos. In contrast, hsFlt-1-e15a induced preeclampsia-like symptoms; however, it also increased litter size. In accord with the predominant placental expression of hsFlt-1-e15a and msFlt-1-i13, full-length sFlt-1 may have a role in the regulation of embryonic development. These observations point to the difference in the biological effects of full-length and truncated sFlt-1 and the changes in the effect of full-length sFlt-1 during pregnancy, and may have important implications in the management of preeclampsia.

Placental Nkx2-5 and target gene expression in early-onset and severe preeclampsia

OBJECTIVE

Preeclampsia (PE) affects 2-8% of pregnancies worldwide and is a significant source of maternal and neonatal morbidity and mortality. However, the mechanisms underlying PE are poorly understood and major questions regarding etiology and risk factors remain to be addressed. Our objective was to examine whether abnormal expression of the cardiovascular developmental transcription factor, Nkx2-5, was associated with early onset and severe preeclampsia (EOSPE).

METHODS

Using qPCR and immunohistochemical assay, we examined expression of Nkx2-5 and target gene expression in EOSPE and control placental tissue. We tested resulting mechanistic hypotheses in cultured cells using shRNA knockdown, qPCR, and western blot.

RESULTS

Nkx2-5 is highly expressed in racially disparate fashion (Caucasians > African Americans) in a subset of early EOSPE placentae. Nkx2-5 mRNA expression is highly correlated (Caucasians > African Americans) to mRNA expression of the preeclampsia marker sFlt-1, and of the Nkx2-5 target and RNA splicing factor, Sam68. Knockdown of Sam68 expression in cultured cells significantly impacts sFlt-1 mRNA isoform generation in vitro, supporting a mechanistic hypothesis that Nkx2-5 impacts EOSPE severity in a subset of patients via upregulation of Sam68 to increase sFlt-1 expression. Expression of additional Nkx2-5 targets potentially regulating metabolic stress response is also elevated in a racially disparate fashion in EOSPE.

CONCLUSIONS

Expression of Nkx2-5 and its target genes may directly influence the genesis and racially disparate severity, and define a mechanistically distinct subclass of EOSPE.

Involvement of the Heme Oxygenase System in the Development of Preeclampsia and as a Possible Therapeutic Target

The enzyme heme oxygenase (HO) is an important regulatory molecule present in most nucleated mammalian cells which functions to break down the pro-oxidant molecule heme into three products, carbon monoxide (CO), biliverdin and free iron. The HO system has been associated with many physiologic functions, including vascular tone, regulation of inflammation and apoptosis, angiogenesis and antioxidant capabilities. Deficiencies in HO are associated with several pregnancy disorders, including preeclampsia. With no present cure, this disorder continues to affect 5–7% of all pregnancies worldwide, leading to maternal and fetal morbidity and mortality. Researchers continue to strive for therapeutic potentials and this review will outline the possible use of the HO/CO system as a target treatment/prevention of preeclampsia in the future.

Carbon monoxide prevents hypertension and proteinuria in an adenovirus sFlt-1 preeclampsia-like mouse model

Preeclampsia (PE) remains a leading cause of maternal and neonatal morbidity and mortality worldwide. Smoking cigarettes is associated with a decreased incidence of PE. Based on this observation and previous work, we hypothesize that women who smoke have a lower risk of developing PE because of elevated levels of carbon monoxide (CO) in their blood. The objective of this study was to determine if low-dose CO in ambient air could attenuate the late pregnancy hypertension (HTN) and proteinuria in the Adenovirus (Ad) sFlt-1 PE-like mouse model. Continuous low-dose CO treatment (250 ppm) was started on E10.5 and maintained until E17.5. Compared to control and Ad empty vector, AdsFlt-1 mice displayed late- gestation HTN (E14.5–17.5) (P<0.05), proteinuria (P<0.05) and reduced Bowman's space which were all prevented with CO treatment. Use of the Ad (with/without sFlt-1) or CO had no effect (p>0.05) on litter size, fetal resorption numbers and fetal or placental weights. This study shows that treatment with CO can prevent HTN and proteinuria in a mouse model of PE. It provides a possible mechanism for the reduced incidence of PE in smoking women, and supports the possibility of using CO as a future treatment for PE.

Growth factors in preeclampsia: a vascular disease model. A failed vasodilation and angiogenic challenge from pregnancy onwards?

Preeclampsia is the major cause of maternofetal and neonatal morbi-mortality including intrauterine growth retardation, miscarriages and stillbirths. Inadequate vascular dilation and angiogenesis represent the crucial underlying defect of gravidic hypertension, denoting a failed response to the vasodilatory and pro-angiogenic challenge imposed by pregnancy, especially if multifetal. A similar pathogenesis appears involved in gestational diabetes. In this review we aimed to provide a hint on understanding the deeply involved angiogenic disorders which eventually culminate in utero-placental failure. The key players in these complex processes may be found in an intricate network of growth factors (GFs) and GF inhibitors, controlled by several vascular risk factors modulated by environment and genes, which eventually impact on early and late cardiovascular outcomes of mother and fetus.

GPCRs as potential therapeutic targets in preeclampsia

Preeclampsia is an important obstetric complication that arises in 5% of women after the 20(th) week of gestation, for which there is no specific therapy and no cure. Although much of the recent investigation in this field has focused on soluble forms of the angiogenic membrane receptor tyrosine kinase Flt1 and the transforming growth factor β co-receptor Endoglin, there is significant clinical potential for several GPCR targets and their agonists or antagonists in preeclampsia. In this review, we discuss several of the most promising candidates in this category, including calcitonin receptor-like receptor / receptor activity modifying protein 1 complexes, the angiotensin AT1, 2 and Mas receptors, and the relaxin receptor RXFP1. We also address some of the controversies surrounding the roles and therapeutic potential of these GPCRs and their (ant)agonists in preeclampsia.

The vascular endothelial growth factor family in adverse pregnancy outcomes

BACKGROUND

Pre-eclampsia, small-for-gestational-age infants, preterm birth and recurrent miscarriage complicate a significant number of pregnancies. The vascular endothelial growth factor (VEGF) family of angiogenic growth factors is implicated in the pathophysiology of these complications. We aimed to elucidate the role of these angiogenic factors in placentation and to evaluate the predictive value of their protein concentrations and genetic variations in pregnancy complications.

METHODS

We performed a systematic search of PubMed, and retrieved original articles. The search included a combination of terms such as VEGF-A, placental growth factor (PlGF), kinase insert domain receptor, fms-like-tyrosine-kinase receptor 1, soluble fms-like-tyrosine-kinase receptor 1, pre-eclampsia, small-for-gestational-age infants, preterm birth, recurrent miscarriage, placenta, prediction and polymorphisms.

RESULTS

This review summarizes the current knowledge of the roles of the VEGF family in early placentation and of the abnormalities in maternal plasma and placental expression of angiogenic proteins in adverse pregnancy outcomes compared with normal pregnancy. PlGF and sFLT-1 in combination with other clinical and biochemical markers in late first or second trimester appear to predict early-onset pre-eclampsia with a high sensitivity and specificity. However, VEGF family proteins do not have sufficient power to accurately predict late-onset pre-eclampsia, small-for-gestational age pregnancies or preterm birth. Functional polymorphisms in these angiogenic genes are implicated in pregnancy complications, but their contribution appears to be minor.

CONCLUSIONS

Although the VEGF family has important roles in normal and complicated pregnancy, the current predictive value of the VEGF family as biomarkers appears to be limited to early-onset pre-eclampsia.