Hypertension produced by placental ischemia in pregnant rats is associated with increased soluble endoglin expression

Reduced uterine perfusion pressure as a model for preeclampsia and fetal growth restriction in murine: a systematic review and meta-analysis

The reduced uterine perfusion pressure (RUPP) model is frequently used to study preeclampsia and fetal growth restriction. An improved understanding of influential factors might improve reproducibility and reduce animal use considering the variability in RUPP phenotype. We performed a systematic review and meta-analysis by searching Medline and Embase (until 28 March, 2023) for RUPP studies in murine. Primary outcomes included maternal blood pressure (BP) or proteinuria, fetal weight or crown-rump length, fetal reabsorptions, or antiangiogenic factors. We aimed to identify influential factors by meta-regression analysis. We included 155 studies. Our meta-analysis showed that the RUPP procedure results in significantly higher BP (MD = 24.1 mmHg; [22.6; 25.7]; n = 148), proteinuria (SMD = 2.3; [0.9; 3.8]; n = 28), fetal reabsorptions (MD = 50.4%; [45.5; 55.2]; n = 42), circulating soluble FMS-like tyrosine kinase-1 (sFlt-1) (SMD = 2.6; [1.7; 3.4]; n = 34), and lower fetal weight (MD = -0.4 g; [-0.47; -0.34]; n = 113. The heterogeneity (variability between studies) in primary outcomes appeared ≥90%. Our meta-regression identified influential factors in the method and time point of BP measurement, randomization in fetal weight, and type of control group in sFlt-1. The RUPP is a robust model considering the evident differences in maternal and fetal outcomes. The high heterogeneity reflects the observed variability in phenotype. Because of underreporting, we observed reporting bias and a high risk of bias. We recommend standardizing study design by optimal time point and method chosen for readout measures to limit the variability. This contributes to improved reproducibility and thereby eventually improves the translational value of the RUPP model.

Preeclampsia epidemiology(ies) and pathophysiology(ies)

Preeclampsia/eclampsia was first described 2000 years ago. Concepts guiding diagnosis have changed over time making longitudinal studies challenging. Similarly, concepts of pathophysiology have evolved from eclampsia as a pregnancy seizure disorder to preeclampsia as a hypertensive and renal disorder to our current concept of a preeclampsia as a pregnancy specific, multisystemic inflammatory disorder. Although preeclampsia is pregnancy specific and many pathophysiologic findings begin to resolve with delivery, its impact extends beyond pregnancy. The risk of cardiovascular and neurological disease is increased after pregnancy in women who have had preeclampsia. The disorder is not a disease, but a syndrome and emerging data indicate multiple pathways to the syndrome. It is likely that our failure to have a major impact on prediction and prevention despite a large increase in understanding is due to the existence of multiple subtypes of preeclampsia. This concept should guide future research.

Assessment of feto-placental oxygenation and perfusion in a rat model of placental insufficiency using T2* mapping and 3D dynamic contrast-enhanced MRI

INTRODUCTION

Placental insufficiency may lead to preeclampsia and fetal growth restriction. There is no cure for placental insufficiency, emphasizing the need for monitoring fetal and placenta health. Current monitoring methods are limited, underscoring the necessity for imaging techniques to evaluate fetal-placental perfusion and oxygenation. This study aims to use MRI to evaluate placental oxygenation and perfusion in the reduced uterine perfusion pressure (RUPP) model of placental insufficiency.

METHODS

Pregnant rats were randomized to RUPP (n = 11) or sham surgery (n = 8) on gestational day 14. On gestational day 19, rats imaged using a 7T MRI scanner to assess oxygenation and perfusion using T2* mapping and 3D-DCE MRI sequences, respectively. The effect of the RUPP on the feto-placental units were analyzed from the MRI images.

RESULTS

RUPP surgery led to reduced oxygenation in the labyrinth (24.7 ± 1.8 ms vs. 28.0 ± 2.1 ms, P = 0.002) and junctional zone (7.0 ± 0.9 ms vs. 8.1 ± 1.1 ms, P = 0.04) of the placenta, as indicated by decreased T2* values. However, here were no significant differences in fetal organ oxygenation or placental perfusion between RUPP and sham animals.

DISCUSSION

The reduced placental oxygenation without a corresponding decrease in perfusion suggests an adaptive response to placental ischemia. While acute reduction in placental perfusion may cause placental hypoxia, persistence of this condition could indicate chronic placental insufficiency after ischemic reperfusion injury. Thus, placental oxygenation may be a more reliable biomarker for assessing fetal condition than perfusion in hypertensive disorders of pregnancies including preeclampsia and FGR.

Urinary phenol and paraben concentrations in association with markers of inflammation during pregnancy in Puerto Rico

Exposure to phenols and parabens may contribute to increased maternal inflammation and adverse birth outcomes, but these effects are not well-studied in humans. This study aimed to investigate relationships between concentrations of 8 phenols and 4 parabens with 6 inflammatory biomarkers (C-reactive protein (CRP); matrix metalloproteinases (MMP) 1, 2, and 9; intercellular adhesion molecule-1 (ICAM-1); and vascular cell adhesion molecule-1 (VCAM-1)) measured at two time points in pregnancy in the PROTECT birth cohort in Puerto Rico. Linear mixed models were used, adjusting for covariates of interest. Results are expressed as the percent change in outcome per interquartile range (IQR) increase in exposure. Particularly among phenols, numerous significant negative associations were found, for example, between benzophenone-3 and CRP (-11.21 %, 95 % CI: -17.82, -4.07) and triclocarban and MMP2 (-9.87 %, 95 % CI: -14.05, -5.5). However, significant positive associations were also detected, for instance, between bisphenol-A (BPA) and CRP (9.77 %, 95 % CI: 0.67, 19.68) and methyl-paraben and MMP1 (10.78 %, 95 % CI: 2.17, 20.11). Significant interactions with female fetal sex and the later study visit (at 24-28 weeks gestation) showed more positive associations compared to male fetal sex and the earlier study visit (16-20 weeks gestation). Our results suggest that phenols and parabens may disrupt inflammatory processes pertaining to uterine remodeling and endothelial function, with important implications for pregnancy outcomes. More research is needed to further understand maternal inflammatory status in an effort to improve reproductive and developmental outcomes.

Dual-modal Photoacoustic and Ultrasound Imaging: from preclinical to clinical applications

Photoacoustic imaging is a novel biomedical imaging modality that has emerged over the recent decades. Due to the conversion of optical energy into the acoustic wave, photoacoustic imaging offers high-resolution imaging in depth beyond the optical diffusion limit. Photoacoustic imaging is frequently used in conjunction with ultrasound as a hybrid modality. The combination enables the acquisition of both optical and acoustic contrasts of tissue, providing functional, structural, molecular, and vascular information within the same field of view. In this review, we first described the principles of various photoacoustic and ultrasound imaging techniques and then classified the dual-modal imaging systems based on their preclinical and clinical imaging applications. The advantages of dual-modal imaging were thoroughly analyzed. Finally, the review ends with a critical discussion of existing developments and a look toward the future.

Short stature in small-for-gestational-age offspring born to mothers with hypertensive disorders of pregnancy

OBJECTIVE

To investigate the incidence and risk factors of small-for-gestational age (SGA) short stature at 2 and 3 years of age in SGA offspring born to women with hypertensive disorders of pregnancy (HDP).

METHODS

We examined 226 women with HDP whose respective SGA offspring were delivered.

RESULTS

Eighty offspring (41.2%) were diagnosed with SGA short stature. The prematurity before 32 weeks of gestation was the most significant factor for catch-up growth failure.

CONCLUSION

In SGA offspring born to women with HDP, SGA short stature incidence was high, and the risk factor was prematurity before 32 weeks of gestation.

The association of a panel of circulating markers with hypertensive disorders of pregnancy: the jury is still out

Comparison between using either sFlt-1/PlGF ratio or proposed panel of biomarkers. The latter is proposed by using statistical and machine learning methods. The levels of both sFlt-1 and PlGF are measured in pg/mL. sFlt-1 soluble fms-like tyrosine kinase-1, PlGF placental growth factor, PPV positive predictive value, NPV negative predictive value.

In vivo noninvasive systemic myography of acute systemic vasoactivity in female pregnant mice

Altered vasoactivity is a major characteristic of cardiovascular and oncological diseases, and many therapies are therefore targeted to the vasculature. Therapeutics which are selective for the diseased vasculature are ideal, but whole-body selectivity of a therapeutic is challenging to assess in practice. Vessel myography is used to determine the functional mechanisms and evaluate pharmacological responses of vascularly-targeted therapeutics. However, myography can only be performed on ex vivo sections of individual arteries. We have developed methods for implementation of spherical-view photoacoustic tomography for non-invasive and in vivo myography. Using photoacoustic tomography, we demonstrate the measurement of acute vascular reactivity in the systemic vasculature and the placenta of female pregnant mice in response to two vasodilators. Photoacoustic tomography simultaneously captures the significant acute vasodilation of major arteries and detects selective vasoactivity of the maternal-fetal vasculature. Photoacoustic tomography has the potential to provide invaluable preclinical information on vascular response that cannot be obtained by other established methods.

Reversal of maternal obesity attenuates hypoxia and improves placental development in the preeclamptic-like BPH/5 mouse model

Background

Women with obesity have higher risk of adverse pregnancy outcomes, including preeclampsia (PE). Late-gestational hypertension, aberrant fetoplacental development, and fetal growth restriction (FGR), hallmarks of PE, are observed spontaneously in BPH/5 mice. Similar to obese preeclamptic women, BPH/5 mice have higher visceral white adipose tissue (WAT) and circulating leptin. We hypothesized that attenuation of maternal obesity and serum leptin in pregnant BPH/5 mice will improve fetoplacental development by decreasing hypoxia markers and leptin expression at the maternal-fetal interface.

Methods

To test this hypothesis, BPH/5 mice were fed ad libitum (lib) and pair-fed (PF) to C57 ad lib controls beginning at embryonic day (e) 0.5. Hypoxia-related genes, hypoxia inducible factor (Hif) 1α, stem cell factor (Scf), heme oxygenase-1 (Ho-1), leptin (Lep), and leptin receptor (LepR) were assessed in e7.5 implantation sites.

Results

BPH/5 ad lib had 1.5 to 2-fold increase in Hif1α, Scf, and Ho-1 mRNA and a greater than 3-fold increase in leptin mRNA vs. C57 that was attenuated with PF. Exogenous leptin promoted Hif1α and Ho-1 mRNA expression in e7.5 decidua in vitro. While hypoxic conditions in vitro did not change decidual leptin mRNA. Furthermore, BPH/5 PF mice demonstrated improved fetal and placental outcomes later in gestation, with greater placental vascular area by e18.5 and attenuation of FGR.

Conclusion

In conclusion, pair-feeding BPH/5 mice beginning at conception may improve placental vasculature formation via decreased leptin and hypoxia-associated markers in this model. Future investigations are needed to better determine the effect of hypoxia and leptin on pregnancy outcomes in obese pregnant women.

From Molecules to Imaging: Assessment of Placental Hypoxia Biomarkers in Placental Insufficiency Syndromes

Placental hypoxia poses significant risks to both the developing fetus and the mother during pregnancy, underscoring the importance of early detection and monitoring. Effectively identifying placental hypoxia and evaluating the deterioration in placental function requires reliable biomarkers. Molecular biomarkers in placental tissue can only be determined post-delivery and while maternal blood biomarkers can be measured over time, they can merely serve as proxies for placental function. Therefore, there is an increasing demand for non-invasive imaging techniques capable of directly assessing the placental condition over time. Recent advancements in imaging technologies, including photoacoustic and magnetic resonance imaging, offer promising tools for detecting and monitoring placental hypoxia. Integrating molecular and imaging biomarkers may revolutionize the detection and monitoring of placental hypoxia, improving pregnancy outcomes and reducing long-term health complications. This review describes current research on molecular and imaging biomarkers of placental hypoxia both in human and animal studies and aims to explore the benefits of an integrated approach throughout gestation.

Ambulatory Blood Pressure Monitoring for Diagnosis and Management of Hypertension in Pregnant Women

Hypertension disorders during pregnancy has a wide range of severities, from a mild clinical condition to a life-threatening one. Currently, office BP is still the main method for the diagnosis of hypertension during pregnancy. Despite of the limitation these measurements, in clinical practice office BP of 140/90 mmHg cut point is used to simplify diagnosis and treatment decisions. The out-of-office BP evaluations are it comes to discarding white-coat hypertension with little utility in practice to rule out masked hypertension and nocturnal hypertension. In this revision, we analyzed the current evidence of the role of ABPM in diagnosing and managing pregnant women. ABPM has a defined role in the evaluation of BP levels in pregnant women, being appropriate performing an ABPM to classification of HDP before 20 weeks of gestation and second ABMP performed between 20-30 weeks of gestation to detected of women with a high risk of development of PE. Furthermore, we propose to, discarding white-coat hypertension and detecting masked chronic hypertension in pregnant women with office BP > 125/75 mmHg. Finally, in women who had PE, a third ABPM in the post-partum period could identify those with higher long-term cardiovascular risk related with masked hypertension.

Cardiovascular Dysfunction in Intrauterine Growth Restriction

PURPOSE OF REVIEW

We highlight important new findings on cardiovascular dysfunction in intrauterine growth restriction.

RECENT FINDINGS

Intrauterine growth restriction (IUGR) is a multifactorial condition which negatively impacts neonatal growth during pregnancy and is associated with health problems during the lifespan. It affects 5-15% of all pregnancies in the USA and Europe with varying percentages in developing countries. Epidemiological studies have reported that IUGR is associated with the pathogenesis of hypertension, activation of the renin-angiotensin system (RAS), disruption in placental-mTORC and TGFβ signaling cascades, and endothelial dysfunction in IUGR fetuses, children, adolescents, and adults resulting in the development of cardiovascular diseases (CVD). Experimental studies are needed to investigate therapeutic measures to treat increased blood pressure (BP) and long-term CVD problems in people affected by IUGR. We outline the mechanisms mediating fetal programming of hypertension in developing CVD. We have reviewed findings from different experimental models focusing on recent studies that demonstrate CVD in IUGR.

Photoacoustic imaging provides an in vivo assessment of the preeclamptic placenta remodeling and function in response to therapy

INTRODUCTION

There is a lack of effective therapeutic interventions for preeclampsia. A central factor in the etiology of the disease is the development of placental hypoxia due to abnormal vascular remodeling. However, methods to assess the impact of potential therapies on placental growth and remodeling are currently lacking. Here, we develop and validate ultrasound-guided photoacoustic imaging methods to monitor the placental response to therapeutic intervention. Establishing non-invasive tools to image placental function opens up previously unachievable understandings of placental therapeutic response.

METHODS

Studies were performed in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. Preclinical research has identified tempol, a superoxide dismutase mimetic, and the phosphodiesterase inhibitor sildenafil as potential therapeutics for preeclampsia, as both improve in vivo maternal outcomes. PA images of the placental environment were acquired in RUPP rats receiving tempol (n = 8) or sildenafil (n = 8) to assess the longitudinal effects of treatment on placental oxygenation and vascular remodeling. Imaging measurements were validated with ex vivo histological analysis.

RESULTS

Spectral photoacoustic imaging non-invasively measured placental hypoxia and impaired vascular growth two days after the RUPP procedure was implemented. Sildenafil significantly improved (p < 0.05) placental oxygenation and promoted vascular remodeling in RUPP animals, while RUPP animals treated with tempol had a diminished placental therapeutic response.

DISCUSSION

We demonstrate that photoacoustic imaging provides in vivo measures of placental oxygenation and vascular remodeling, a previously unobtainable assessment of preeclamptic therapeutic response. These imaging tools have tremendous potential to accelerate the search for effective therapies for preeclampsia.

Hypertensive disorders of pregnancy: definition, management, and out-of-office blood pressure measurement

Hypertensive disorders of pregnancy increase the risk of adverse maternal and fetal outcomes. In 2018, the Japanese classification of hypertensive disorders of pregnancy was standardized with those of other countries, and a hypertensive disorder of pregnancy was considered to be present if hypertension existed during pregnancy and up to 12 weeks after delivery. Strategies for the prevention of hypertensive disorders of pregnancy have become much clearer, but further research is needed on appropriate subjects and methods of administration, and these have not been clarified in Japan. Although guidelines for the use of antihypertensive drugs are also being studied and standardized with those of other countries, the use of calcium antagonists before 20 weeks of gestation is still contraindicated in Japan because of the safety concerns that were raised regarding possible fetal anomalies associated with their use at the time of their market launch. Chronic hypertension is now included in the definition of hypertensive disorders of pregnancy, and blood pressure measurement is a fundamental component of the diagnosis of hypertensive disorders of pregnancy. Out-of-office blood pressure measurements, including ambulatory and home blood pressure measurements, are important for pregnant and nonpregnant women. Although conditions such as white-coat hypertension and masked hypertension have been reported, determining their occurrence in pregnancy is complicated by the gestational week. This narrative review focused on recent reports on hypertensive disorders of pregnancy, including those related to blood pressure measurement and classification.

How Soluble Fms-Like Tyrosine Kinase 1 Could Contribute to Blood-Brain Barrier Dysfunction in Preeclampsia?

Preeclampsia is a pregnancy-related syndrome that courses with severe cerebrovascular complications if not properly managed. Findings from pre-clinical and clinical studies have proposed that the imbalance between pro- and anti-angiogenic factors exhibited in preeclampsia is a major component of its pathophysiology. In this regard, measurement of circulating levels of soluble tyrosine kinase-1 similar to fms (sFlt-1), a decoy receptor for vascular endothelial growth factor (VEGF), is a moderately reliable biomarker for the diagnosis of preeclampsia. However, few studies have established a mechanistic approach to determine how the high levels of sFlt-1 are responsible for the endothelial dysfunction, and even less is known about its effects at the blood-brain barrier (BBB). Since the expression pattern of VEGF receptors type 1 and 2 in brain endothelial cells differs from the observed in peripheral endothelial cells, and components of the neurovascular unit of the BBB provide paracrine secretion of VEGF, this compartmentalization of VEGF signaling could help to see in a different viewpoint the role of sFlt-1 in the development of endothelial dysfunction. In this article, we provide a hypothesis of how sFlt-1 could eventually be a protective factor for brain endothelial cells of the BBB under preeclampsia.

The role of endoglin and its soluble form in pathogenesis of preeclampsia

Preeclampsia remains till today a leading cause of maternal and fetal morbidity and mortality. Pathophysiology of the disease is not yet fully elucidated, though it is evident that it revolves around placenta. Cellular ischemia in the preeclamptic placenta creates an imbalance between angiogenic and anti-angiogenic factors in maternal circulation. Endoglin, a transmembrane co-receptor of transforming growth factor β (TGF-β) demonstrating angiogenic effects, is involved in a variety of angiogenesis-dependent diseases with endothelial dysfunction, including preeclampsia. Endoglin expression is up-regulated in preeclamptic placentas, through mechanisms mainly induced by hypoxia, oxidative stress and oxysterol-mediated activation of liver X receptors. Overexpression of endoglin results in an increase of its soluble form in maternal circulation. Soluble endoglin represents the extracellular domain of membrane endoglin, cleaved by the action of metalloproteinases, predominantly matrix metalloproteinase-14. Released in circulation, soluble endoglin interferes in TGF-β1 and activin receptor-like kinase 1 signaling pathways and inhibits endothelial nitric oxide synthase activation, consequently deranging angiogenesis and promoting vasoconstriction. Due to these properties, soluble endoglin actively contributes to the impaired placentation observed in preeclampsia, as well as to the pathogenesis and manifestation of its clinical signs and symptoms, especially hypertension and proteinuria. The significant role of endoglin and soluble endoglin in pathophysiology of preeclampsia could have prognostic, diagnostic and therapeutic perspectives. Further research is essential to extensively explore the potential use of these molecules in the management of preeclampsia in clinical settings.

Animal models of preeclampsia: investigating pathophysiology and therapeutic targets

Animal models have been critical in investigating the pathogenesis, mediators, and even therapeutic options for a number of diseases, including preeclampsia. Preeclampsia is the leading cause of maternal and fetal morbidity and mortality worldwide. The placenta is thought to play a central role in the pathogenesis of this disease because it releases antiangiogenic and proinflammatory factors into the maternal circulation, resulting in the maternal syndrome. Despite the deleterious effects preeclampsia has been shown to have on the mother and baby during pregnancy and postpartum, there is still no effective treatment for this disease. Although clinical studies in patients are crucial to identify the involvement of pathogenic factors in preeclampsia, there are obvious limitations that prevent detailed investigation of the quantitative importance of time-dependent mechanisms involved in this syndrome. Animal models allow investigators to perform proof-of-concept studies and examine whether certain factors found in women with preeclampsia mediate hypertension and other manifestations of this disease. In this brief review, we summarize some of the more widely studied models used to investigate pathophysiological mechanisms that are thought to be involved in preeclampsia. These include models of placental ischemia, angiogenic imbalance, and maternal immune activation. Infusion of preeclampsia-related factors into animals has been widely studied to understand the specific mediators of this disease. These models have been included, in addition to a number of genetic models involved in overexpression of the renin-angiotensin system, complement activation, and trophoblast differentiation. Together, these models cover multiple mechanisms of preeclampsia from trophoblast dysfunction and impaired placental vascularization to the excess circulating placental factors and clinical manifestation of this disease. Most animal studies have been performed in rats and mice; however, we have also incorporated nonhuman primate models in this review. Preclinical animal models not only have been instrumental in understanding the pathophysiology of preeclampsia but also continue to be important tools in the search for novel therapeutic options for the treatment of this disease.

Maternal circulating concentrations of soluble Fas and Elabela in early- and late-onset preeclampsia

OBJECTIVE

The Fas/Fas ligand (FASL) system and Elabela-apelin receptor signaling pathways are implicated in the pathophysiology of preeclampsia. The aim of the current study was to investigate whether a model combining the measurement of sFas and Elabela in the maternal circulation may serve as a clinical biomarker for early- and/or late-onset preeclampsia more effectively than measures of each biomarker individually.

METHODS

Blood samples were collected from 214 women in the following groups: (1) normal pregnancy sampled <34 weeks of gestation (n = 56); (2) patients who developed early-onset preeclampsia (n = 54); (3) normal pregnancy sampled ≥34 weeks of gestation (n = 52); (4) patients who developed late-onset preeclampsia (n = 52). Maternal circulating soluble Fas and Elabela concentrations were determined using sensitive and validated immunoassays. Two sample t-tests, multivariate logistic regression, and receiver operating characteristic curves were used for analyses.

RESULTS

(1) Women with early-onset preeclampsia, and those with late-onset preeclampsia with placental lesions of maternal vascular malperfusion, had increased concentrations of sFas compared to their gestational age-matched normal controls; (2) women with late-onset preeclampsia, but not those with early-onset preeclampsia, had increased concentrations of Elabela compared to their gestational age-matched counterparts; and (3) an increase in both Elabela and sFas concentrations was more strongly associated with late-onset preeclampsia than early-onset preeclampsia relative to models including either of the markers alone.

CONCLUSIONS

A combined model of maternal sFas and Elabela concentrations provides a stronger association with late-onset preeclampsia than either protein alone. This finding demonstrates the possibility to improve the classification of late-onset preeclampsia by combining the results of both molecular biomarkers.

Neurovascular dysfunctions in hypertensive disorders of pregnancy

Hypertensive disorders in pregnancy pose a huge challenge to the socioeconomic stability of a community; being a major cause of maternal and neonatal morbidity and mortality during delivery. Although there have been recent improvements in management strategies, still, the diversified nature of the underlying pathogenesis undermines their effectiveness. Generally, these disorders are categorized into two; hypertensive disorders of pregnancy with proteinuria (pre-eclampsia and eclampsia) and hypertensive disorders of pregnancy without proteinuria (gestational and chronic hypertension). Each of these conditions may present with unique characteristics that have interwoven symptoms. However, the tendency of occurrence heightens in the presence of any pre-existing life-threatening condition(s), environmental, and/or other genetic factors. Investigations into the cerebrovascular system demonstrate changes in the histoarchitectural organization of neurons, the proliferation of glial cells with an associated increase in inflammatory cytokines. These are oxidative stress indicators which impose a deteriorating impact on the structures that form the neurovascular unit and the blood-brain barrier (BBB). Such a pathologic state distorts the homeostatic supply of blood into the brain, and enhances the permeability of toxins/pathogens through a process called hyperperfusion at the BBB. Furthermore, a notable aspect of the pathogenesis of hypertensive disorders of pregnancy is endothelial dysfunction aggravated when signaling of the vasoprotective molecule, nitric oxide, amongst other neurotransmitter regulatory activities are impaired. This review aims to discuss the alterations in cerebrovascular regulation that determine the incidence of hypertension in pregnancy.

Towards Transabdominal Functional Photoacoustic Imaging of the Placenta: Improvement in Imaging Depth Through Optimization of Light Delivery

Functional photoacoustic imaging of the placenta could provide an innovative tool to diagnose preeclampsia, monitor fetal growth restriction, and determine the developmental impacts of gestational diabetes. However, transabdominal photoacoustic imaging is limited in imaging depth due to the tissue's scattering and absorption of light. The aim of this paper was to investigate the impact of geometry and wavelength on transabdominal light delivery. Our methods included the development of a multilayer model of the abdominal tissue and simulation of the light propagation using Monte Carlo methods. A bifurcated light source with varying incident angle of light, distance between light beams, and beam area was simulated to analyze the effect of light delivery geometry on the fluence distribution at depth. The impact of wavelength and the effects of variable thicknesses of adipose tissue and muscle were also studied. Our results showed that the beam area plays a major role in improving the delivery of light to deep tissue, in comparison to light incidence angle or distance between the bifurcated fibers. Longer wavelengths, with incident fluence at the maximum permissible exposure limit, also increases fluence within deeper tissue. We validated our simulations using a commercially available light delivery system and ex vivo human placental tissue. Additionally, we compared our optimized light delivery to a commercially available light delivery system, and conclude that our optimized geometry could improve imaging depth more than 1.6×, bringing the imaging depth to within the needed range for transabdominal imaging of the human placenta.

Placental hypoxia: What have we learnt from small animal models?

Intrauterine hypoxia is a feature of pregnancy complications, both at high altitude and sea level. To understand the placental response to reduced oxygen availability, small animal models of maternal inhalation hypoxia (MIH) or reduced uterine perfusion pressure (RUPP) may be utilised. The aim of this review was to compare the findings of those studies to identify the role of oxygen availability in adapting placental structural and functional phenotypes in relation to fetal outcome. It also sought to explore the evidence for the involvement of particular genes and protein signalling pathways in the placenta in mediating hypoxia driven alterations. The data available demonstrate that both MIH and RUPP can induce placental hypoxia, which affects placental structure and vascularity, as well as glucose, amino acid, calcium and possibly lipid transport capacity. In addition, changes have been observed in HIF, VEGF, insulin/IGF2, AMPK, mTOR, PI3K and PPARγ signalling, which may be key in linking together observed phenotypes under conditions of placental hypoxia. Many different manipulations have been examined, with varied outcomes depending on the intensity, timing and duration of the insult. Some manipulations have detrimental effects on placental phenotype, viability and fetal growth, whereas in others, the placenta appears to adapt to uphold fetal growth despite the challenge of low oxygen. Together these data suggest a complex response of the placenta to reduced oxygen availability, which links to changes in fetal outcomes. However, further work is required to explore the role of fetal sex, altered maternal physiology and placental molecular mechanisms to fully understand placental responses to hypoxia and their relevance for pregnancy outcome.

Modelling preeclampsia: a comparative analysis of the common human trophoblast cell lines

Preeclampsia remains a challenge without an effective therapy. Evidence supports targetability of soluble fms‐like tyrosine kinase‐1 (sFlt‐1) and soluble endoglin (sEng), which are released excessively from the placenta under ischemic and hypoxic stresses. We compared four trophoblast cell lines, BeWo, Jar, Jeg‐3, and HTR‐8/SVneo, in order to identify a suitable model for drug screening. Cultured trophoblasts were exposed to 1% oxygen vs. normoxia for 24‐48 hr; human umbilical vein and aortic endothelial cells were included for comparison. Supernatant sFlt‐1 and sEng concentrations were measured by ELISA, and sFlt‐1 mRNA expression determined by RT‐PCR. Cellular responses to experimental therapeutics were explored. All four trophoblast lines secreted sEng, which did not increase by hypoxia. BeWo, Jar, and Jeg‐3 exhibited significantly enhanced expression of sFlt‐1 i13 and e15a mRNA in response to hypoxia; however, only BeWo released a detectable level of sFlt‐1 protein, which was doubled by hypoxia. In contrast, hypoxia decreased sFlt‐1 mRNA expression and protein release in HTR‐8/SVneo, similarly to endothelial cells. The cellular mechanism involved HIFα. BeWo responded to representative agents similarly to human primary placental tissues in the literature. These data support that the BeWo‐hypoxia model mimics a key pathogenic mechanism of preeclampsia and has potential value for translational drug discovery.

Pregnancy-Induced High Plasma Levels of Soluble Endoglin in Mice Lead to Preeclampsia Symptoms and Placental Abnormalities

Preeclampsia is a pregnancy-specific disease of high prevalence characterized by the onset of hypertension, among other maternal or fetal signs. Its etiopathogenesis remains elusive, but it is widely accepted that abnormal placentation results in the release of soluble factors that cause the clinical manifestations of the disease. An increased level of soluble endoglin (sEng) in plasma has been proposed to be an early diagnostic and prognostic biomarker of this disease. A pathogenic function of sEng involving hypertension has also been reported in several animal models with high levels of plasma sEng not directly dependent on pregnancy. The aim of this work was to study the functional effect of high plasma levels of sEng in the pathophysiology of preeclampsia in a model of pregnant mice, in which the levels of sEng in the maternal blood during pregnancy replicate the conditions of human preeclampsia. Our results show that wild type pregnant mice carrying human sEng-expressing transgenic fetuses (fWT(hsEng⁺)) present high plasma levels of sEng with a timing profile similar to that of human preeclampsia. High plasma levels of human sEng (hsEng) are associated with hypertension, proteinuria, fetal growth restriction, and the release of soluble factors to maternal plasma. In addition, fWT(hsEng⁺) mice also present placental alterations comparable to those caused by the poor remodeling of the spiral arteries characteristic of preeclampsia. In vitro and ex vivo experiments, performed in a human trophoblast cell line and human placental explants, show that sEng interferes with trophoblast invasion and the associated pseudovasculogenesis, a process by which cytotrophoblasts switch from an epithelial to an endothelial phenotype, both events being related to remodeling of the spiral arteries. Our findings provide a novel and useful animal model for future research in preeclampsia and reveal a much more relevant role of sEng in preeclampsia than initially proposed.

Spherical-view photoacoustic tomography for monitoring in vivo placental function

Photoacoustic tomography has great potential to image dynamic functional changes in vivo. Many tomographic systems are built with a circular view geometry, necessitating a linear translation along one axis of the subject to obtain a three-dimensional volume. In this work, we evaluated a prototype spherical view photoacoustic tomographic system which acquires a 3D volume in a single scan, without linear translation. We simultaneously measured relative hemoglobin oxygen saturation in multiple placentas of pregnant mice under oxygen challenge. We also synthesized a folate-conjugated indocyanine green (ICG) contrast agent to image folate kinetics in the placenta. Photoacoustic tomography performed at the wavelength of peak optical absorption of our contrast agent revealed increased ICG signal over time. Through these phantom and in vivo studies, we have demonstrated that the spherical view 3D photoacoustic tomographic system achieves high sensitivity and fast image acquisition, enabling in vivo experiments to assess physiological and molecular dynamics.

Vascular mechanisms and molecular targets in hypertensive pregnancy and preeclampsia

Preeclampsia is a major complication of pregnancy manifested as hypertension and often intrauterine growth restriction, but the underlying pathophysiological mechanisms are unclear. Predisposing genetic and environmental factors cause placental maladaptations leading to defective placentation, apoptosis of invasive cytotrophoblasts, inadequate expansive remodeling of the spiral arteries, reduced uteroplacental perfusion pressure, and placental ischemia. Placental ischemia promotes the release of bioactive factors into the maternal circulation, causing an imbalance between antiangiogenic soluble fms-like tyrosine kinase-1 and soluble endoglin and proangiogenic vascular endothelial growth factor, placental growth factor, and transforming growth factor-β. Placental ischemia also stimulates the release of proinflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin type 1 receptor agonistic autoantibodies. These circulating factors target the vascular endothelium, causing generalized endotheliosis in systemic, renal, cerebral, and hepatic vessels, leading to decreases in endothelium-derived vasodilators such as nitric oxide, prostacyclin, and hyperpolarization factor and increases in vasoconstrictors such as endothelin-1 and thromboxane A₂. The bioactive factors also target vascular smooth muscle and enhance the mechanisms of vascular contraction, including cytosolic Ca²⁺, protein kinase C, and Rho-kinase. The bioactive factors could also target matrix metalloproteinases and the extracellular matrix, causing inadequate vascular remodeling, increased arterial stiffening, and further increases in vascular resistance and hypertension. As therapeutic options are limited, understanding the underlying vascular mechanisms and molecular targets should help design new tools for the detection and management of hypertension in pregnancy and preeclampsia.

Serum levels of vasoactive factors in HIV-infected pre-eclamptic women on HAART

In South Africa, pre-eclampsia (PE) and human immunodeficiency virus (HIV) infection are major causes of pregnancy-related deaths. This study aimed to measure serum levels of endothelin-1 (ET-1), endothelial nitric oxide synthase (eNOS), soluble fms-like tyrosine kinase 1 (sFlt-1), soluble endoglin (sEng) and placental growth factor (PlGF) in HIV-infected highly active antiretroviral therapy (HAART)-treated and HIV-uninfected PE and normotensive women to ascertain if HIV/HAART alters their concentrations. Mean sFlt-1 levels were significantly up-regulated in the PE (HIV-uninfected 4.39 ± 1.29; HIV-infected 5.10 ± 1.10 ng/ml) compared to normotensive women (HIV-uninfected 2.59 ± 0.83; HIV-infected 2.20 ± 0.85 ng/ml). Mean PlGF levels were significantly lower in HIV-uninfected PE vs. HIV-infected normotensive women (29.69 ± 4.47 pg/ml vs. 32.86 ± 6.46 pg/ml; p = .002). In conclusion, PE women with HIV exhibited significantly low serum PlGF, ET-1 and eNOS levels. Infection with HIV may have further increased the sFlt-1 levels.IMPACT STATEMENTWhat is already known on this subject? In PE, the numerous identified local and circulating bioactive factors differed in concentrations when compared to normal pregnancy.What do the results of this study add? PE women with HIV exhibited significantly low serum PlGF, ET-1 and eNOS levels as well as increased levels of sFlt-1.What are the implications of these findings for clinical practice and/or further research? Understanding the link between PE, HIV and HAART during pregnancy will improve prognosis, management and treatment strategies for women clinically.

Interleukin-17 signaling mediates cytolytic natural killer cell activation in response to placental ischemia

T-helper (T_H)17s, IL-17, and cytolytic natural killer cells (cNKs) are increased in preeclampsia and contribute to the hypertension, inflammation, and fetal growth restriction that occurs in response to placental ischemia in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. As IL-17 stimulates NK cytotoxicity in vitro, we tested the hypothesis that IL-17 inhibition in RUPP rats would decrease cNK activation as a mechanism to improve maternal and fetal outcomes. On gestation day (GD) 14, rats undergoing RUPP received a miniosmotic pump infusing IL-17RC (100 pg/day), a soluble IL-17 receptor (RUPP + IL-17RC). On GD19, mean arterial pressure (MAP) was measured in normal pregnant (NP), RUPP, and RUPP + IL-17RC rats (n = 10-12/group), animals were euthanized, and blood and tissues were collected for analysis. MAP was 30% higher in RUPP compared with NP (P < 0.0001) and was 12% lower in RUPP + IL-17RC (P = 0.0007 vs. RUPP). Placental cytolytic NK cells were 132% higher in RUPP than in NP (P = 0.04 vs. NP) and were normalized in RUPP + IL-17RC (P = 0.03 vs. RUPP). Placental levels of TNF-α, a cNK-secreted cytokine, and macrophage inflammatory protein-3α (MIP-3α), a cNK chemokine, were higher in RUPP vs. NP and lower after IL-17 blockade. Placental VEGF was lower in RUPP vs. NP and was normalized in RUPP + IL-17RC. In vitro cytolytic activity of RUPP placental NKs was higher compared with NP and was blunted in RUPP + IL-17RC NKs. Finally, both fetal weight and placental weight were lower in RUPP compared with NP, and were improved in RUPP + IL-17RC. These data identify IL-17 as a mediator of cNK activation in response to placental ischemia during pregnancy.

Hydroxychloroquine Mitigates the Production of 8-Isoprostane and Improves Vascular Dysfunction: Implications for Treating Preeclampsia

In preeclampsia, widespread maternal endothelial dysfunction is often secondary to excessive generation of placental-derived anti-angiogenic factors, including soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), along with proinflammatory cytokines such as tumour necrosis factor-α (TNF-α) and activin A, understanding of which offers potential opportunities for the development of novel therapies. The antimalarial hydroxychloroquine is an anti-inflammatory drug improving endothelial homeostasis in lupus. It has not been explored as to whether it can improve placental and endothelial function in preeclampsia. In this in vitro study, term placental explants were used to assess the effects of hydroxychloroquine on placental production of sFlt-1, sEng, TNF-α, activin A, and 8-isoprostane after exposure to hypoxic injury or oxidative stress. Similarly, human umbilical vein endothelial cells (HUVECs) were used to assess the effects of hydroxychloroquine on in vitro markers of endothelial dysfunction. Hydroxychloroquine had no effect on the release of sFlt-1, sEng, TNF-α, activin A, or 8-isoprostane from placental explants exposed to hypoxic injury or oxidative stress. However, hydroxychloroquine mitigated TNF-α-induced HUVEC production of 8-isoprostane and Nicotinanamide adenine dinucleotide phosphate (NADPH) oxidase expression. Hydroxychloroquine also mitigated TNF-α and preeclamptic serum-induced HUVEC monolayer permeability and rescued the loss of zona occludens protein zona occludens 1 (ZO-1). Although hydroxychloroquine had no apparent effects on trophoblast function, it may be a useful endothelial protectant in women presenting with preeclampsia.

Decreased uterine vascularization and uterine arterial expansive remodeling with reduced matrix metalloproteinase-2 and -9 in hypertensive pregnancy

Normal pregnancy involves extensive remodeling of uterine and spiral arteries and matrix metalloproteinases (MMPs)-mediated proteolysis of extracellular matrix (ECM). Preeclampsia is characterized by hypertension in pregnancy (HTN-Preg) and intrauterine growth restriction (IUGR) with unclear mechanisms. Initial faulty placentation and reduced uterine perfusion pressure (RUPP) could release cytoactive factors and trigger an incessant cycle of suppressed trophoblast invasion of spiral arteries, further RUPP, and progressive placental ischemia leading to HTN-Preg and IUGR; however, the extent and depth of uterine vascularization and the proteolytic enzymes and ECM proteins involved are unclear. We hypothesized that HTN-Preg involves decreased uterine vascularization and arterial remodeling by MMPs and accumulation of ECM collagen. Blood pressure (BP) and fetal parameters were measured in normal Preg rats and RUPP rat model, and the uteri were assessed for vascularity, MMP levels, and collagen deposition. On gestational day 19, BP was higher, and the uterus weight, litter size, and pup weight were reduced in RUPP vs. Preg rats. Histology of uterine tissue sections showed reduced number (5.75 ± 0.95 vs. 11.50 ± 0.87) and size (0.05 ± 0.01 vs. 0.12 ± 0.02 mm2) of uterine spiral arterioles in RUPP vs. Preg rats. Immunohistochemistry showed localization of endothelial cell marker cluster of differentiation 31 (CD31) and smooth muscle marker α-actin in uterine arteriolar wall and confirmed decreased number/size of uterine arterioles in RUPP rats. The cytotrophoblast marker cytokeratin-7 showed less staining and invasion of spiral arteries in the deep decidua of RUPP vs. Preg rats. Uterine arteries showed less expansion in response to increases in intraluminal pressure in RUPP vs. Preg rats. Western blot analysis, gelatin zymography, and immunohistochemistry showed decreases in MMP-2 and MMP-9 and increases in the MMP substrate collagen-IV in uterus and uterine arteries of RUPP vs. those in Preg rats. The results suggest decreased number, size and expansiveness of spiral and uterine arteries with decreased MMP-2 and MMP-9 and increased collagen-IV in HTN-Preg. Decreased uterine vascularization and uterine arterial expansive remodeling by MMPs could be contributing mechanisms to uteroplacental ischemia in HTN-Preg and preeclampsia.NEW & NOTEWORTHY Preeclampsia is a pregnancy-related disorder in which initial inadequate placentation and RUPP cause the release of cytoactive factors and trigger a ceaseless cycle of suppressed trophoblast invasion of spiral arteries, further RUPP, and progressive placental ischemia leading to HTN-Preg and IUGR; however, the extent/depth of uterine vascularization and the driving proteolytic enzymes and ECM proteins are unclear. This study shows decreased number, size, and expansiveness of uterine spiral arteries, with decreased MMP-2 and MMP-9 and increased collagen-IV in HTN-Preg rats. The decreased uterine vascularization and uterine arterial expansive remodeling by MMPs could contribute to progressive uteroplacental ischemia in HTN-Preg and preeclampsia.

Perinatal Micro-Bleeds and Neuroinflammation in E19 Rat Fetuses Exposed to Utero-Placental Ischemia

Offspring of preeclampsia patients have an increased risk of developing neurological deficits and cognitive impairment. While low placental perfusion, common in preeclampsia and growth restriction, has been linked to neurological deficits, a causative link is not fully established. The goal of this study was to test the hypothesis that placental ischemia induces neuroinflammation and micro-hemorrhages in utero. Timed-pregnant Sprague Dawley rats were weight-matched for sham surgery (abdominal incision only) or induced placental ischemia (surgical reduction of utero-placental perfusion (RUPP)); n = 5/group on gestational day 14. Fetal brains (n = 1–2/dam/endpoint) were collected at embryonic day (E19). Placental ischemia resulted in fewer live fetuses, increased fetal demise, increased hematocrit, and no difference in brain water content in exposed fetuses. Additionally, increased cerebral micro-bleeds (identified with H&E staining), pro-inflammatory cytokines: IL-1β, IL-6, and IL-18, eotaxin (CCL11), LIX (CXCL5), and MIP-2 (CXCL2) were observed in RUPP-exposed fetuses. Microglial density in the sub-ventricular zone decreased in RUPP-exposed fetuses, with no change in cortical thickness. Our findings support the hypothesis that exposure to placental ischemia contributes to microvascular dysfunction (increased micro-bleeds), fetal brain inflammation, and reduced microglial density in proliferative brain areas. Future studies will determine whether in utero abnormalities contribute to long-term behavioral deficits in preeclampsia offspring through impaired neurogenesis regulation.

[Potential value of placental angiogenic factors as biomarkers in preeclampsia for clinical physicians]

The role of angiogenic factors in the onset of clinical manifestations of preeclampsia was demonstrated in 2003 by the implication of sFlt-1, PlGF and VEGF, and in 2006 by the implication of soluble endoglin. Placental ischemia and inflammation observed in preeclampsia alter both the production and progression of angiogenic factors during pregnancy. During the first trimester, the combination of PlGF with clinical, biophysical and biological factors results in a better test than the conventional one. However, the clinical value of this method remains to be confirmed. During the second and third trimesters, the sFlt-1/PlGF ratio may be used, with or without pre-existing renal disease, for short-term prediction, diagnosis, and prognosis, and to evaluate the effectiveness of preeclampsia treatment. While a sFlt-1/PlGF ratio<38 and≤33, respectively, rules out the short-term onset and diagnosis of preeclampsia, a sFlt-1/PlGF ratio≥85 between 20 and 34 weeks of pregnancy and≥110 beyond 34 weeks of pregnancy confirms a diagnosis of preeclampsia. Angiogenic and non-angiogenic preeclampsia are identified by a sFlt-1PlGF≥85 and<85, respectively, with the risk of maternal and fetal complications at two weeks differing between the two. Similarly, a sFlt-1/PlGF ratio>665 and>205, respectively, is a good short-term predictor of adverse outcomes of early and late-onset preeclampsia. These values could be incorporated into future guidelines for better clinical management of preeclampsia.

Spectral photoacoustic imaging to estimate in vivo placental oxygenation during preeclampsia

Preeclampsia is a pregnancy-related hypertensive disorder accounting for 14% of global maternal deaths annually. Preeclampsia - maternal hypertension and proteinuria - is promoted by placental ischemia resulting from reduced uteroplacental perfusion. Here, we assess longitudinal changes in placental oxygenation during preeclampsia using spectral photoacoustic imaging. Spectral photoacoustic images were acquired of the placenta of normal pregnant (NP) and preeclamptic reduced uterine perfusion pressure (RUPP) Sprague Dawley rats on gestational days (GD) 14, 16, and 18, corresponding to mid- to late gestation (n = 10 per cohort). Two days after implementation of the RUPP surgical model, placental oxygen saturation decreased 12% in comparison with NP. Proteinuria was determined from a 24-hour urine collection prior to imaging on GD18. Blood pressure measurements were obtained on GD18 after imaging. Placental hypoxia in the RUPP was confirmed with histological staining for hypoxia-inducible factor (HIF)-1α, a cellular transcription regulator which responds to local oxygen levels. Using in vivo, longitudinal imaging methods we determined that the placenta in the reduced uterine perfusion pressure rat model of preeclampsia is hypoxic, and that this hypoxia is maintained through late gestation. Future work will utilize these methods to assess the impact of novel therapeutics on placental ischemia and the progression of preeclampsia.

Reduced Uteroplacental Perfusion Pressure (RUPP) causes altered trophoblast differentiation and pericyte reduction in the mouse placenta labyrinth

This study characterized the effect of the reduced utero-placental perfusion pressure (RUPP) model of placental insufficiency on placental morphology and trophoblast differentiation at mid-late gestation (E14.5). Altered trophoblast proliferation, reduced syncytiotrophoblast gene expression, increased numbers of sinusoidal trophoblast giant cells, decreased Vegfa and decreased pericyte presence in the labyrinth were observed in addition to changes in maternal blood spaces, the fetal capillary network and reduced fetal weight. Further, the junctional zone was characterized by reduced spongiotrophoblast and glycogen trophoblast with increased trophoblast giant cells. Increased Hif-1α and TGF-β-3 in vivo with supporting hypoxia studies in trophoblast stem (TS) cells in vitro, support hypoxia as a contributing factor to the RUPP placenta phenotype. Together, this study identifies altered cell populations within the placenta that may contribute to the phenotype, and thus support the use of RUPP in the mouse as a model of placenta insufficiency. As such, this model in the mouse provides a valuable tool for understanding the phenotypes resulting from genetic manipulation of isolated cell populations to further understand the etiology of placenta insufficiency and fetal growth restriction. Further this study identifies a novel relationship between placental insufficiency and pericyte depletion in the labyrinth layer.

Preeclampsia: Disease biology and burden, its management strategies with reference to India

Preeclampsia is the cause of significant maternal and fetal mortality and morbidity. It is characterized by new-onset hypertension and proteinuria after 20 weeks of gestation. Preeclamptic women and children born from preeclamptic pregnancies are at greater risk to develop severe cardiovascular complications and metabolic syndromes later in life. The incidence of preeclampsia is estimated to be seven times higher in developing countries as compared to the developed countries. This review summarizes the pathophysiology of preeclampsia, emerging new hypothesis of its origin, risk factors that make women susceptible to developing preeclampsia and the potential of various biomarkers being studied to predict preeclampsia. The health care of developing countries is continuously challenged by substantial burden of maternal and fetal mortality. India despite being a fast developing country, is still far behind in achieving the required maternal mortality rates as per Millennium Development Goals set by the World Health Organization. Further, this review discusses the prevalence of preeclampsia in India, health facilities to manage preeclampsia, current guidelines and protocols followed and government policies to combat this complication in Indian condition.

Molecular determinants of microvascular dysfunction in hypertensive pregnancy and preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and often fetal intrauterine growth restriction, but the underlying mechanisms are unclear. Defective placentation and apoptosis of invasive cytotrophoblasts cause inadequate remodeling of spiral arteries, placental ischemia, and reduced uterine perfusion pressure (RUPP). RUPP causes imbalance between the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the pro-angiogenic vascular endothelial growth factor and placental growth factor, and stimulates the release of proinflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors target the vascular endothelium, smooth muscle and various components of the extracellular matrix. Generalized endotheliosis in systemic, renal, cerebral, and hepatic vessels causes decreases in endothelium-derived vasodilators such as nitric oxide, prostacyclin and hyperpolarization factor, and increases in vasoconstrictors such as endothelin-1 and thromboxane A2. Enhanced mechanisms of vascular smooth muscle contraction, such as intracellular Ca2+ , protein kinase C, and Rho-kinase cause further increases in vasoconstriction. Changes in matrix metalloproteinases and extracellular matrix cause inadequate vascular remodeling and increased arterial stiffening, leading to further increases in vascular resistance and hypertension. Therapeutic options are currently limited, but understanding the molecular determinants of microvascular dysfunction could help in the design of new approaches for the prediction and management of preeclampsia.

ELABELA plasma concentrations are increased in women with late-onset preeclampsia

Objective: ELABELA is a newly discovered peptide hormone that appears to be implicated in the mechanisms leading to preeclampsia, independently of angiogenic factors. The aim of the current study was to investigate whether women with early- or late-onset preeclampsia have altered ELABELA plasma concentrations compared to gestational-age-matched normal pregnant women.Methods: This retrospective cross-sectional study focused on the maternal plasma samples collected from 232 women with a singleton pregnancy who were allocated into the following groups: (1) early-onset preeclampsia (<34 weeks of gestation, N = 56); (2) late-onset preeclampsia (≥34 weeks of gestation, N = 57); and (3) gestational-age-matched controls with a normal pregnancy [(<34 weeks of gestation, N = 59); (≥34 weeks of gestation, N = 60)]. ELABELA plasma concentrations were determined using a validated enzyme immunoassay.Results: (1) ELABELA plasma concentrations are higher in patients with late-onset preeclampsia compared with those from gestational-age-matched controls with a normal pregnancy [median: 7.99 ng/mL (IQR, 5.3-13.95 ng/mL) versus median: 4.17 ng/mL (IQR, 3-11.19 ng/mL), p =.001]; (2) ELABELA plasma concentrations in patients with early-onset preeclampsia do not differ from those of normal pregnant women [median: 6.09 ng/mL (IQR, 2.8-10.66 ng/mL) versus median: 4.02 ng/mL (IQR, 3.26-7.49), p = .32]; and (3) ELABELA plasma concentrations are higher in patients with late-onset preeclampsia compared to those with early-onset preeclampsia [median: 7.99 ng/mL (IQR, 5.3-13.95 ng/mL) versus median: 6.09 ng/mL (IQR, 2.8-10.66 ng/mL), p = .01].Conclusion: ELABELA plasma concentrations are higher in patients with late-onset preeclampsia than in those with a normal pregnancy. However, women with early-onset preeclampsia have similar ELABELA plasma concentrations to those with a normal pregnancy. These findings provide insight into the ELABELA axis during the human syndrome of preeclampsia. In addition, these data support the concept that different pathophysiologic mechanisms are implicated in early- and late-onset preeclampsia.

Hypoxia and Placental Development

Hemochorial placentation is orchestrated through highly regulated temporal and spatial decisions governing the fate of trophoblast stem/progenitor cells. Trophoblast cell acquisition of specializations facilitating invasion and uterine spiral artery remodeling is a labile process, sensitive to the environment, and represents a process that is vulnerable to dysmorphogenesis in pathologic states. Hypoxia is a signal guiding placental development, and molecular mechanisms directing cellular adaptations to low oxygen tension are integral to trophoblast cell differentiation and placentation. Hypoxia can also be used as an experimental tool to investigate regulatory processes controlling hemochorial placentation. These developmental processes are conserved in mouse, rat, and human placentation. Consequently, elements of these developmental events can be modeled and hypotheses tested in trophoblast stem cells and in genetically manipulated rodents. Hypoxia is also a consequence of a failed placenta, yielding pathologies that can adversely affect maternal adjustments to pregnancy, fetal health, and susceptibility to adult disease. The capacity of the placenta for adaptation to environmental challenges highlights the importance of its plasticity in safeguarding a healthy pregnancy. Birth Defects Research 109:1309-1329, 2017.© 2017 Wiley Periodicals, Inc.

Postpartum increases in cerebral edema and inflammation in response to placental ischemia during pregnancy

Reduced placental blood flow results in placental ischemia, an initiating event in the pathophysiology of preeclampsia, a hypertensive pregnancy disorder. While studies show increased mortality risk from Alzheimer's disease, stroke, and cerebrovascular complications in women with a history of preeclampsia, the underlying mechanisms are unknown. During pregnancy, placental ischemia, induced by reducing uterine perfusion pressure (RUPP), leads to cerebral edema and increased blood-brain barrier (BBB) permeability; however whether these complications persist after delivery is not known. Therefore, we tested the hypothesis that placental ischemia contributes to postpartum cerebral edema and neuroinflammation. On gestational day 14, time-pregnant Sprague Dawley rats underwent Sham (n = 10) or RUPP (n = 9) surgery and brain tissue collected 2 months post-delivery. Water content increased in posterior cortex but not hippocampus, striatum, or anterior cerebrum following RUPP. Using a rat cytokine multi-plex kit, posterior cortical IL-17, IL-1α, IL-1β, Leptin, and MIP2 increased while hippocampal IL-4, IL-12(p70) and RANTES increased and IL-18 decreased following RUPP. Western blot analysis showed no changes in astrocyte marker, Glial Fibrillary Acidic Protein (GFAP); however, the microglia marker, ionized calcium binding adaptor molecule (Iba1) tended to increase in hippocampus of RUPP-exposed rats. Immunofluorescence staining revealed reduced number of posterior cortical microglia but increased activated (Type 4) microglia in RUPP. Astrocyte number increased in both regions but area covered by astrocytes increased only in posterior cortex following RUPP. BBB-associated proteins, Claudin-1, Aquaporin-4, and zonular occludens-1 expression were unaltered; however, posterior cortical occludin decreased. These results suggest that 2 months postpartum, neuroinflammation, along with decreased occludin expression, may partly explain posterior cortical edema in rats with history of placental ischemia.

Matrix Metalloproteinases, Vascular Remodeling, and Vascular Disease

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that degrade various proteins in the extracellular matrix (ECM). Typically, MMPs have a propeptide sequence, a catalytic metalloproteinase domain with catalytic zinc, a hinge region or linker peptide, and a hemopexin domain. MMPs are commonly classified on the basis of their substrates and the organization of their structural domains into collagenases, gelatinases, stromelysins, matrilysins, membrane-type (MT)-MMPs, and other MMPs. MMPs are secreted by many cells including fibroblasts, vascular smooth muscle (VSM), and leukocytes. MMPs are regulated at the level of mRNA expression and by activation through removal of the propeptide domain from their latent zymogen form. MMPs are often secreted in an inactive proMMP form, which is cleaved to the active form by various proteinases including other MMPs. MMPs degrade various protein substrates in ECM including collagen and elastin. MMPs could also influence endothelial cell function as well as VSM cell migration, proliferation, Ca²⁺ signaling, and contraction. MMPs play a role in vascular tissue remodeling during various biological processes such as angiogenesis, embryogenesis, morphogenesis, and wound repair. Alterations in specific MMPs could influence arterial remodeling and lead to various pathological disorders such as hypertension, preeclampsia, atherosclerosis, aneurysm formation, as well as excessive venous dilation and lower extremity venous disease. MMPs are often regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP ratio often determines the extent of ECM protein degradation and tissue remodeling. MMPs may serve as biomarkers and potential therapeutic targets for certain vascular disorders.

Angiogenic imbalance and diminished matrix metalloproteinase-2 and -9 underlie regional decreases in uteroplacental vascularization and feto-placental growth in hypertensive pregnancy

Preeclampsia is a form of hypertension-in-pregnancy (HTN-Preg) with unclear mechanism. Generalized reduction of uterine perfusion pressure (RUPP) could be an initiating event leading to uteroplacental ischemia, angiogenic imbalance, and HTN-Preg. Additional regional differences in uteroplacental blood flow could further affect the pregnancy outcome and increase the risk of preeclampsia in twin or multiple pregnancy, but the mechanisms involved are unclear. To test the hypothesis that regional differences in angiogenic balance and matrix metalloproteinases (MMPs) underlie regional uteroplacental vascularization and feto-placental development, we compared fetal and placental growth, and placental and myoendometrial vascularization in the proximal, middle and distal regions of the uterus (in relation to the iliac bifurcation) in normal pregnant (Preg) and RUPP rats. Maternal blood pressure and plasma anti-angiogenic soluble fms-like tyrosine kinase-1 (sFlt-1)/placenta growth factor (PIGF) ratio were higher, and average placentae number, placenta weight, litter size, and pup weight were less in RUPP than Preg rats. The placenta and pup number and weight were reduced, while the number and diameter of placental and adjacent myoendometrial arteries, and MMP-2 and MMP-9 levels/activity were increased, and sFlt-1/PlGF ratio was decreased in distal vs proximal uterus of Preg rats. In RUPP rats, the placenta and pup number and weight, the number and diameter of placental and myoendometrial arteries, and MMP-2 and -9 levels/activity were decreased, and sFlt-1/PlGF ratio was increased in distal vs proximal uterus. Treatment with sFlt-1 or RUPP placenta extract decreased MMP-2 and MMP-9 in distal segments of Preg uterus, and treatment with PIGF or Preg placenta extract restored MMP levels in distal segments of RUPP uterus. Thus, in addition to the general reduction in placental and fetal growth during uteroplacental ischemia, localized angiogenic imbalance and diminished MMP-2 and MMP-9 could cause further decrease in placental and myoendometrial vascularization and placental and fetal growth in distal vs proximal uterus of HTN-Preg rats. Regional differences in uteroplacental perfusion, angiogenic balance and MMPs could be a factor in the incidence of preeclampsia in multiple pregnancy.

The prediction of late-onset preeclampsia: Results from a longitudinal proteomics study

BACKGROUND

Late-onset preeclampsia is the most prevalent phenotype of this syndrome; nevertheless, only a few biomarkers for its early diagnosis have been reported. We sought to correct this deficiency using a high through-put proteomic platform.

METHODS

A case-control longitudinal study was conducted, including 90 patients with normal pregnancies and 76 patients with late-onset preeclampsia (diagnosed at ≥34 weeks of gestation). Maternal plasma samples were collected throughout gestation (normal pregnancy: 2-6 samples per patient, median of 2; late-onset preeclampsia: 2-6, median of 5). The abundance of 1,125 proteins was measured using an aptamers-based proteomics technique. Protein abundance in normal pregnancies was modeled using linear mixed-effects models to estimate mean abundance as a function of gestational age. Data was then expressed as multiples of-the-mean (MoM) values in normal pregnancies. Multi-marker prediction models were built using data from one of five gestational age intervals (8-16, 16.1-22, 22.1-28, 28.1-32, 32.1-36 weeks of gestation). The predictive performance of the best combination of proteins was compared to placental growth factor (PIGF) using bootstrap.

RESULTS

1) At 8-16 weeks of gestation, the best prediction model included only one protein, matrix metalloproteinase 7 (MMP-7), that had a sensitivity of 69% at a false positive rate (FPR) of 20% (AUC = 0.76); 2) at 16.1-22 weeks of gestation, MMP-7 was the single best predictor of late-onset preeclampsia with a sensitivity of 70% at a FPR of 20% (AUC = 0.82); 3) after 22 weeks of gestation, PlGF was the best predictor of late-onset preeclampsia, identifying 1/3 to 1/2 of the patients destined to develop this syndrome (FPR = 20%); 4) 36 proteins were associated with late-onset preeclampsia in at least one interval of gestation (after adjustment for covariates); 5) several biological processes, such as positive regulation of vascular endothelial growth factor receptor signaling pathway, were perturbed; and 6) from 22.1 weeks of gestation onward, the set of proteins most predictive of severe preeclampsia was different from the set most predictive of the mild form of this syndrome.

CONCLUSIONS

Elevated MMP-7 early in gestation (8-22 weeks) and low PlGF later in gestation (after 22 weeks) are the strongest predictors for the subsequent development of late-onset preeclampsia, suggesting that the optimal identification of patients at risk may involve a two-step diagnostic process.

Increased vascular and uteroplacental matrix metalloproteinase-1 and -7 levels and collagen type I deposition in hypertension in pregnancy: role of TNF-α

Preeclampsia is a pregnancy-related disorder manifested as maternal hypertension in pregnancy (HTN-Preg) and fetal growth restriction. Placental ischemia could be an initiating event that leads to abnormal vascular and uteroplacental remodeling in HTN-Preg; however, the molecular targets and intermediary mechanisms involved are unclear. We tested the hypothesis that placental ischemia could target vascular and uteroplacental matrix metalloproteinases (MMPs) through an inflammatory cytokine-mediated mechanism. MMP levels and distribution were measured in the aorta, uterus, and placenta of normal pregnant (Preg) rats and pregnant rats with reduced uterine perfusion pressure (RUPP). Maternal blood pressure was higher and the litter size and pup weight were lower in RUPP compared with Preg rats. Gelatin zymography showed prominent uterine MMP-2 and MMP-9 activity that was dependent on the amount of loaded protein. At saturating protein loading, both gelatin and casein zymography revealed two additional bands corresponding to MMP-1 and MMP-7 that were greater in the aorta, uterus, and placenta of RUPP compared with Preg rats. Western blots and immunohistochemistry confirmed increased MMP-1 and MMP-7 in the aorta, uterus, and placenta of RUPP versus Preg rats. The levels of MMP-1 and MMP-7 substrate collagen type I were greater in tissues of RUPP compared with Preg rats. In organ culture, TNF-α increased MMP-1 and MMP-7 in the aorta, uterus, and placenta of Preg rats, and a TNF-α antagonist prevented the increases in MMPs in tissues of RUPP rats. Thus, placental ischemia, possibly through TNF-α, increases vascular and uteroplacental MMP-1 and MMP-7, which, in turn, alter collagen deposition and cause inadequate tissue remodeling in HTN-Preg. Cytokine antagonists may reverse the increase in MMP-1 and MMP-7 expression/activity and, in turn, restore proper vascular and uteroplacental remodeling in HTN-Preg and preeclampsia.NEW & NOTEWORTHY The molecular mechanisms of preeclampsia are unclear, making it difficult to predict, prevent, or manage the pregnancy-associated disorder. This study showed that placental ischemia, possibly through the release of TNF-α, causes increases in the levels of matrix metalloproteinase (MMP)-1 and MMP-7, which could alter collagen deposition and cause inadequate uteroplacental and vascular remodeling in hypertension in pregnancy. The data suggest that targeting MMP-1 and MMP-7 and their upstream modulators, such as TNF-α, could provide a new approach in the management of hypertension in pregnancy and preeclampsia.

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

Decreased homodimerization and increased TIMP-1 complexation of uteroplacental and uterine arterial matrix metalloproteinase-9 during hypertension-in-pregnancy

Preeclampsia is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg) and often intrauterine growth restriction (IUGR). Placental ischemia could be an initiating event, but the molecular mechanisms are unclear. To test the hypothesis that dimerization of matrix metalloproteinases (MMPs) plays a role in HTN-Preg and IUGR, the levels/activity of MMP-9, tissue inhibitor of metalloproteinase (TIMP-1), and their dimerization forms were measured in the placenta, uterus, and uterine artery of normal pregnant (Preg) rats and a rat model of reduced uteroplacental perfusion pressure (RUPP). Consistent with our previous report, blood pressure (BP) was higher, pup weight was lower, and gelatin zymography showed different gelatinolytic activity for pro-MMP-9, MMP-9, pro-MMP-2 and MMP-2 in RUPP vs Preg rats. Careful examination of the zymograms showed additional bands at 200 and 135kDa. Western blots with MMP-9 antibody suggested that the 200kDa band was a MMP-9 homodimer. Western blots with TIMP-1 antibody as well as reverse zymography suggested that the 135kDa band was a MMP-9/TIMP-1 complex. The protein levels and gelatinase activity of MMP-9 homodimer were decreased while MMP-9/TIMP-1 complex was increased in placenta, uterus and uterine artery of RUPP vs Preg rats. The epidermal growth factor (EGF) receptor blocker erlotinib and protein kinase C (PKC) inhibitor bisindolylmaleimide decreased MMP-9 homodimer and increased MMP-9/TIMP-1 complex in placenta, uterus and uterine artery of Preg rats. EGF and the PKC activator phorbol-12,13-dibutyrate (PDBu) reversed the decreases in MMP-9 homodimer and the increases in MMP-9/TIMP-1 complex in tissues of RUPP rats. Thus, the increased BP and decreased pup weight in placental ischemia model of HTN-Preg are associated with a decrease in MMP-9 homodimer and an increase in MMP-9/TIMP-1 complex in placenta, uterus, and uterine artery, which together would cause a net decrease in MMP-9 activity and reduce uteroplacental and vascular remodeling in the setting of HTN-Preg and IUGR. Enhancing EGFR/PKC signaling may reverse the MMP-9 unfavorable dimerization patterns and thereby promote uteroplacental and vascular remodeling in preeclampsia.

Relationship between hypoxia and downstream pathogenic pathways in preeclampsia

Defects in angiogenesis and mitochondrial function in the placenta contribute to the pathogenesis of preeclampsia; however upstream regulators of these pathways are not known. It has been argued that placental hypoxia secondary to abnormal spiral artery remodeling may play a causal role in the angiogenic and mitochondrial abnormalities noted in preeclampsia. The aim of this study was to evaluate the relationship between hypoxia-inducible factor-1α (HIF-1α) ¸ a surrogate of hypoxia, and soluble fms-tyrosine kinase 1 (sFlt1), a circulating anti-angiogenic factor, and microRNA 210 (miR-210), a microRNA that regulates mitochondrial function, in human placentas from preeclamptic and non-hypertensive pregnancies. We first confirmed a 2.5-fold upregulation of HIF-1α protein in placentas from preeclampsia when compared to non-hypertensive controls. Consistent with prior studies, we also observed a 10-fold upregulated sFlt1 mRNA and 2-fold upregulated miR-210 in preeclamptic tissue. Interestingly, while sFlt1 mRNA correlated with miR-210 in preeclampsia (R² = 0.77, p = 0.0004), there were no significant correlations between these molecules and HIF1α expression. We conclude that non-hypoxia pathways may be involved in the abnormal angiogenic and metabolic alterations noted in preeclampsia.

Sex differences in early growth during the first three years of life in offspring from mothers with pregnancy-induced hypertension

OBJECTIVES

Newborns born to mothers with pregnancy-induced hypertension (PIH) are thought to be at high risk for lifestyle-related diseases, such as obesity and hypertension, in adulthood.

STUDY DESIGN

A longitudinal study of 78 pregnant women with PIH and their newborns, who visited Okayama University Hospital from 2009 to 2013.

MAIN OUTCOME MEASURES

We investigated the change in growth of offspring born to mothers with PIH and compared it with the standard growth curve in Japanese to examine whether there was rapid catch-up growth during the first 3years of life.

RESULTS

Subjects were 78 pregnant women with PIH and their offspring, who visited Okayama University Hospital from 2009 to 2013. Valid responses were obtained from 29 of 78 (37.1%) women. Body weight and length at birth were at the third percentile or less in females, and at the 10th percentile or less, in males. When body weight and length were compared at 6months, 18months, and 3years old between male and female toddlers, male toddlers slowly caught up until 3years old, but female toddlers rapidly caught up in the first 6months. Furthermore, in newborns with fetal growth restriction caused by the intrauterine environment of PIH, differences in physical development between male and female toddlers were more remarkable.

CONCLUSIONS

There is a significant sex difference in catch-up growth during the first 3years, which might be involved in lifestyle-related diseases in adulthood, suggesting continuous follow-up is necessary, especially for female offspring.

Magnesium Sulfate Prevents Placental Ischemia-Induced Increases in Brain Water Content and Cerebrospinal Fluid Cytokines in Pregnant Rats

Magnesium sulfate (MgSO₄) is the most widely used therapy in the clinic to prevent the progression of preeclampsia, a hypertensive disorder of pregnancy, to eclampsia. Eclampsia, manifested as unexplained seizures and/or coma during pregnancy or postpartum, accounts for ~13% of maternal deaths worldwide. While MgSO₄ continues to be used in the clinic, the mechanisms by which it exerts its protective actions are not well understood. In this study, we tested the hypothesis that MgSO₄ protects against placental ischemia-induced increases in brain water content and cerebrospinal fluid cytokines. To test this hypothesis, MgSO₄ was administered via mini-osmotic pump (60 mg/day, i.p.) to pregnant and placental ischemic rats, induced by mechanical reduction of uterine perfusion pressure, from gestational day 14–19. This treatment regimen of MgSO₄ led to therapeutic level of 2.8 ± 0.6 mmol/L Mg in plasma. MgSO₄ had no effect on improving placental ischemia-induced changes in mean arterial pressure, number of live fetuses, or fetal and placental weight. Placental ischemia increased, while MgSO₄ prevented the increase in water content in the anterior cerebrum. Cytokine and chemokine levels were measured in the cerebrospinal fluid using a multi-plex assay. Results demonstrate that cerebrospinal fluid, obtained via the cisterna magna, had reduced protein, albumin, interleukin (IL)-17A, IL-18, IL-2, eotaxin, fractalkine, interferon gamma, vascular endothelial growth factor (VEGF), and macrophage inflammatory protein (MIP)-2 following MgSO₄ treatment. These data support the hypothesis that MgSO₄ offers neuroprotection by preventing placental ischemia-induced cerebral edema and reducing levels of cytokines/chemokines in the cerebrospinal fluid.

Restoring placental growth factor-soluble fms-like tyrosine kinase-1 balance reverses vascular hyper-reactivity and hypertension in pregnancy

Preeclampsia (PE) is a pregnancy-related hypertensive disorder (HTN-Preg) with unclear mechanism. An imbalance between antiangiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) and angiogenic placental growth factor (PlGF) has been observed in PE, but the vascular targets and signaling pathways involved are unclear. We assessed the extent of sFlt-1/PlGF imbalance and vascular dysfunction in a rat model of HTN-Preg produced by reduction of uteroplacental perfusion pressure (RUPP), and tested whether inducing a comparable sFlt-1/PlGF imbalance by infusing sFlt-1 (10 μg·kg(-1)·day(-1)) in day 14 pregnant (Preg) rats cause similar increases in blood pressure (BP) and vascular reactivity. Using these guiding measurements, we then tested whether restoring sFlt-1/PlGF balance by infusing PIGF (20 μg·kg(-1)·day(-1)) in RUPP rats would improve BP and vascular function. On gestational day 19, BP was in Preg+sFlt-1 and RUPP > Preg, and in RUPP+PlGF < RUPP rats. Plasma sFlt-1/PlGF ratio was increased in Preg+sFlt-1, and RUPP and was reduced in RUPP+PlGF rats. In isolated endothelium-intact aorta, carotid, mesenteric, and renal artery, phenylephrine (Phe)- and high KCl-induced contraction was in Preg+sFlt-1 and RUPP > Preg, and in RUPP+PlGF < RUPP. The differences in vascular reactivity to Phe and KCl between groups were less apparent in vessels treated with the nitric oxide synthase (NOS) inhibitor l-NAME or guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or endothelium-denuded, suggesting changes in endothelial NO-cGMP pathway. In Phe precontracted vessels, ACh-induced relaxation was in Preg+sFlt-1 and RUPP < Preg, and in RUPP+PlGF > RUPP, and was blocked by N(ω)-nitro-l-arginine methyl ester (l-NAME) or ODQ treatment or endothelium removal. Western blots revealed that aortic total endothelial NOS (eNOS) and activated phosphorylated-eNOS were in Preg+sFlt-1 and RUPP < Preg and in RUPP+PlGF > RUPP. ACh-induced vascular nitrate/nitrite production was in Preg+sFlt-1 and RUPP < Preg, and in RUPP+PlGF > RUPP. Vascular relaxation to the exogenous NO donor sodium nitroprusside was not different among groups. Thus, a tilt in the angiogenic balance toward anti-angiogenic sFlt-1 is associated with decreased vascular relaxation and increased vasoconstriction and BP. Restoring the angiogenic/antiangiogenic balance using PlGF enhances endothelial NO-cGMP vascular relaxation and decreases vasoconstriction and BP in HTN-Preg rats and could offer a new approach in the management of PE.

Mechanisms of Endothelial Dysfunction in Hypertensive Pregnancy and Preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and could lead to maternal and fetal morbidity and mortality. Although the causative factors and pathophysiological mechanisms are unclear, endothelial dysfunction is a major hallmark of preeclampsia. Clinical tests and experimental research have suggested that generalized endotheliosis in the systemic, renal, cerebral, and hepatic circulation could decrease endothelium-derived vasodilators such as nitric oxide, prostacyclin, and hyperpolarization factor and increase vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction, hypertension, and other manifestation of preeclampsia. In search for the upstream mechanisms that could cause endothelial dysfunction, certain genetic, demographic, and environmental risk factors have been suggested to cause abnormal expression of uteroplacental integrins, cytokines, and matrix metalloproteinases, leading to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate spiral arteries remodeling, reduced uterine perfusion pressure (RUPP), and placental ischemia/hypoxia. RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic factors vascular endothelial growth factor and placental growth factor, or stimulate the release of other circulating bioactive factors such as inflammatory cytokines, hypoxia-inducible factor-1, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could then target endothelial cells and cause generalized endothelial dysfunction. Therapeutic options are currently limited, but understanding the factors involved in endothelial dysfunction could help design new approaches for prediction and management of preeclampsia.