Hypoxic treatment of human dual placental perfusion induces a preeclampsia-like inflammatory response

The effects of inflammation and acidosis on placental blood vessels reactivity

INTRODUCTION

Inflammation and acidosis are two stress stimuli that correspond to pathophysiological processes occurring in placental-mediated vascular disorders. We aimed to investigate the effects of these stimuli on placental chorionic blood vessels reactivity using the ex-vivo placental perfusion model.

METHODS

Term placentas were obtained immediately after cesarean deliveries, and selected cotyledons were cannulated and dually perfused ex-vivo. Placentas were perfused with three different protocols: culture medium (M199-controls, n = 5), culture medium with lipopolysaccharide (inflammatory stimuli) (LPS,1 μg/ml, n = 7), and acidotic culture medium (M - 199, pH: 6.9-7, n = 6). Each perfusion experiment was maintained for 180 min. Fetal perfusion pressure was continuously measured. Measurements in response to angiotensin II (AT II) at the end of the perfusion were compared between the treatment groups, including amplitude of the contraction response, relaxation factor, time to maximal constriction and the area under the pressure curve (AUC).

RESULTS

In response to ATII there was a significant difference in the amplitude of the contraction and the AUC between the treatment groups, (p = 0.049, p = 0.015, respectively). As compared with control perfused cotyledon, the inflammatory stimuli significantly increased the vasoconstriction response to ATII in fetal placental blood vessels, as expressed by increased AUC - median (IQR): 555 (235-1184) vs. 133 (118-207), respectively, p = 0.017. The time to maximal constriction and the relaxation factor did not differ between the groups.

DISCUSSION

Inflammatory stimuli but not acidosis impact fetal-placental vasculature in response to ATII, suggesting that inflammation can compromise vascular function.

Exploring maternal-fetal interface with in vitro placental and trophoblastic models

The placenta, being a temporary organ, plays a crucial role in facilitating the exchange of nutrients and gases between the mother and the fetus during pregnancy. Any abnormalities in the development of this vital organ not only lead to various pregnancy-related disorders that can result in fetal injury or death, but also have long-term effects on maternal health. In vitro models have been employed to study the physiological features and molecular regulatory mechanisms of placental development, aiming to gain a detailed understanding of the pathogenesis of pregnancy-related diseases. Among these models, trophoblast stem cell culture and organoids show great promise. In this review, we provide a comprehensive overview of the current mature trophoblast stem cell models and emerging organoid models, while also discussing other models in a systematic manner. We believe that this knowledge will be valuable in guiding further exploration of the complex maternal-fetal interface.

Pre-eclampsia

Pre-eclampsia is a life-threatening disease of pregnancy unique to humans and a leading cause of maternal and neonatal morbidity and mortality. Women who survive pre-eclampsia have reduced life expectancy, with increased risks of stroke, cardiovascular disease and diabetes, while babies from a pre-eclamptic pregnancy have increased risks of preterm birth, perinatal death and neurodevelopmental disability and cardiovascular and metabolic disease later in life. Pre-eclampsia is a complex multisystem disease, diagnosed by sudden-onset hypertension (>20 weeks of gestation) and at least one other associated complication, including proteinuria, maternal organ dysfunction or uteroplacental dysfunction. Pre-eclampsia is found only when a placenta is or was recently present and is classified as preterm (delivery <37 weeks of gestation), term (delivery ≥37 weeks of gestation) and postpartum pre-eclampsia. The maternal syndrome of pre-eclampsia is driven by a dysfunctional placenta, which releases factors into maternal blood causing systemic inflammation and widespread maternal endothelial dysfunction. Available treatments target maternal hypertension and seizures, but the only 'cure' for pre-eclampsia is delivery of the dysfunctional placenta and baby, often prematurely. Despite decades of research, the aetiology of pre-eclampsia, particularly of term and postpartum pre-eclampsia, remains poorly defined. Significant advances have been made in the prediction and prevention of preterm pre-eclampsia, which is predicted in early pregnancy through combined screening and is prevented with daily low-dose aspirin, starting before 16 weeks of gestation. By contrast, the prediction of term and postpartum pre-eclampsia is limited and there are no preventive treatments. Future research must investigate the pathogenesis of pre-eclampsia, in particular of term and postpartum pre-eclampsia, and evaluate new prognostic tests and treatments in adequately powered clinical trials.

A review of ex vivo placental perfusion models: an underutilized but promising method to study maternal-fetal interactions

Studying the placenta can provide information about the mechanistic pathways of pregnancy disease. However, analyzing placental tissues and manipulating placental function in real-time during pregnancy is not feasible. The ex vivo placental perfusion model allows observing important aspects of the physiology and pathology of the placenta, while maintaining its viability and functional integrity, and without causing harm to mother or fetus. In this review, we describe and compare setups for this technically complex model and summarize outcomes from various published studies. We hope that our review will encourage wider use of ex vivo placental perfusion, which in turn would generate more knowledge to improve pregnancy outcomes.

The effects of Interleukin-6 on viability, redox homeostasis and migration capacity of human placental cells JEG-3 in chemically induced hypoxia

Interleukin-6 (IL-6) is a pleiotropic cytokine involved in the regulation of cell growth and differentiation exerting an important role in the immune and inflammatory response. This study aimed to evaluate the effects of three increasing concentrations of IL-6 (1 pg/mL, 5 pg/mL, and 10 pg/mL) on cell viability, redox homeostasis parameters (O2∙, NO2-, glutathione) and migratory potential in human trophoblast cell line JEG-3 under chemically induced hypoxia in short-term (24 h) and long-term (72 h) exposure. The obtained results show a dose-dependent reduction of cell viability and NO levels, while the concentration of O2 ∙increased. Levels of total glutathione increased in a dose-dependent manner compared to control cells, suggesting its significant antioxidative contribution in hypoxic conditions. The migratory potential of cells was significantly elevated in the two highest applied doses implying the disturbance of cell invasive homeostasis at its pathological concentrations, which could represent a risk factor in some pregnancy disorders.

Maternal obesity increases DNA methylation and decreases RNA methylation in the human placenta

Maternal obesity is associated with increased risk of adverse pregnancy and birth outcomes. While increasing body of evidence supports that the etiology is related to fetal and placental hypoxia, molecular signaling changes in response to this pathophysiological condition in human placenta have remained elusive. Here by using varied approaches including immunocytochemistry staining, Western blot, RT-qPCR, and ELISA, we aimed to investigate the changes in epigenetic markers in placentas from obese pregnant women following delivery by Caesarean-section at term. Our results revealed that the levels of 5-methylcytosine (5mC), a methylated form commonly occurring in CpG dinucleotides and an important repressor of gene transcription in the genome, were significantly increased coupled with decreased activity of Ten-Eleven Translocation (TETs) enzymes that principally function by oxidizing 5mC in the obese placenta, consistent with hypoxia-induced genome-wide DNA hypermethylation observed in varied types of cells and tissues. N6-methyladenosine (m6A) represents the most abundant and conserved modification of gene transcripts, especially within mRNAs, which is stalled by m6A methyltransferases or "writers" including METTL-3/-14, WTAP, RBM15B, and KIAA1429. We further showed that obese placentas demonstrated significantly down-regulated levels of m6A along with reduced gene expression of WTAP, RBM15B, and KIAA1429. Our data support that maternal obesity-induced hypoxia may play an important role in triggering genome-wide DNA hypermethylation in the human placenta, and in turn leading to transcriptome-wide inhibition of RNA modifications. Our results further suggest that selectively modulating these pathways may facilitate development of novel therapeutic approaches for controlling and managing maternal obesity-associated adverse clinical outcomes.

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.

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.

Nanoparticle mediated increased insulin-like growth factor 1 expression enhances human placenta syncytium function

INTRODUCTION

Placental dysfunction is an underlying cause of many major obstetric diseases and treatment options for complications like fetal growth restriction (FGR) are limited .We previously demonstrated nanoparticle delivery of the human insulin-like growth factor 1 (hIGF1) transgene under control of the trophoblast-specific PLAC1 promoter maintains normal fetal growth in a surgically-induced FGR mouse model. However, uptake by human placental syncytiotrophoblast has yet to be determined.

METHODS

An ex vivo human placenta perfusion model, term placenta villous fragments, and other in vitro syncytiotrophoblast models were used to determine nanoparticle uptake, transgene expression, and functional responses under oxidative stress conditions.

RESULTS

In the ex vivo perfusion, fluorescence from a Texas-Red conjugated nanoparticle increased in maternal perfusate upon nanoparticle addition and declined by the conclusion of the experiment (P < 0.001. Fluorescent histology confirmed localization in the syncytiotrophoblasts. No Texas-Red fluorescence was detected in the fetal perfusate. Transgene expression of hIGF1 in differentiated BeWo cells, isolated primary trophoblasts and fragments was increased compared to untreated (55,000-fold, P = 0.0003; 95-fold, P = 0.003; 400-fold, P < 0.001, respectively). Functionally, increased hIGF1 expression in villous fragments resulted in translocation of glucose transporter 1 to the syncytiotrophoblast cell membrane and under conditions of oxidative stress in BeWo cells, protected against increased cell death (P < 0.01) and decreased mitochondrial activity (P < 0.01).

CONCLUSION

The current study confirms that our nanoparticle is capable of uptake in human placental syncytium which results in enhanced transgene expression, functional changes to cellular activity and protection against increased oxidative stress.

Aspirin for the prevention and treatment of pre-eclampsia: A matter of COX-1 and/or COX-2 inhibition?

Since the 1970s, we have known that aspirin can reduce the risk of pre‐eclampsia. However, the underlying mechanisms explaining this risk reduction are poorly understood. Both cyclooxygenase (COX)‐1‐ and COX‐2‐dependent effects might be involved. As a consequence of this knowledge hiatus, the optimal dose and timing of initiation of aspirin therapy are not clear. Here, we review how (COX‐1 versus COX‐2 inhibition) and when (prevention versus treatment) aspirin therapy may interfere with the mechanisms implicated in the pathogenesis of pre‐eclampsia. The available evidence suggests that both COX‐1‐ and COX‐2‐dependent effects play important roles in the early stage of aberrant placental development and in the next phase leading to the clinical syndrome of pre‐eclampsia. Collectively, these data suggest that high‐dose (dual COX inhibition) aspirin may be superior to standard low‐dose (selective COX‐1 inhibition) aspirin for the prevention and also treatment of pre‐eclampsia. Therefore, we conclude that more functional and biochemical tests are needed to unravel the contribution of prostanoids in the mechanisms implicated in the pathogenesis of pre‐eclampsia and the potential of dual COX and/or selective COX‐2 inhibition for the prevention and treatment of pre‐eclampsia. This information is vital if we are to deduce the suitability, optimal timing and dose of aspirin and/or a specific COX‐2 inhibitor (most likely using modified forms that do not cross the placenta) that can then be tested in a randomized, controlled trial instead of the current practice of empirical dosing regimens.

Endothelin-1 traps as a potential therapeutic tool: from diabetes to beyond?

There is substantial research on the vasoactive peptide endothelin (ET)-1 in physiology, as well as in pathology. In fact, pathologically elevated levels of ET-1 have been found in several disease states, such as various cardiovascular diseases, different cancers, some neurodegenerative disorders, as well as in diabetes. Here, we describe and discuss ET-1, its importance in different diseases, and the potential therapeutic effects of ET-traps in the treatment of these diseases. Previous in vitro and in vivo research (in the diabetes disease space) demonstrated that ET-traps potently and significantly prevent the induction of different markers of diabetes-related pathology. This included induction of extracellular matrix (ECM) proteins (collagen 4α1 and fibronectin), which are pathologically elevated in diabetes. The ET-traps prevented induction of these and brought a significant return to non-diabetic levels. We also discuss the merits of using ET-traps over the currently used endothelin receptor antagonists (ERAs) and previously used therapeutic antibodies.

Cadmium exposure induces interleukin-6 production via ROS-dependent activation of the ERK1/2 but independent of JNK signaling pathway in human placental JEG-3 trophoblast cells

Maternal exposure to cadmium (Cd) has been associated with preeclampsia (PE), which is a multisystemic disorder characterized by endothelial dysfunction. Elevated interleukin (IL)-6 expression is linked to PE and has been suggested to contribute to maternal endothelial dysfunction. Cd induces IL-6 production in various cell types through different signaling pathways. Thus, this study was designed to investigate the effect of Cd on IL-6 production and the underlying mechanisms in a trophoblast-derived cell line. Cultured JEG-3 trophoblast cells were exposed to non-toxic concentrations of CdCl₂ in the presence or absence of various MAPK inhibitors or N-Acetyl-L-cysteine (NAC). IL-6 was measured by ELISA. Phosphorylation of ERK1/2, JNK, and c-Jun was assessed by Western blotting. Cd exposure induced IL-6 production and increased ERK1/2, JNK, and c-Jun phosphorylation. NAC and the inhibition of ERK1/2 significantly reduced Cd-induced IL-6 production. These data indicate that Cd induces IL-6 production in trophoblast cells through a ROS-dependent activation of ERK1/2.

Placental secretion of apolipoprotein A1 and E: the anti-atherogenic impact of the placenta

High levels of atherogenic lipids in pregnancy are associated with health complications for the mother, the fetus and the newborn. As endocrine secretory tissue, the human placenta releases apolipoproteins (apos), particularly apoA1 and apoE. However, the magnitude and the directionality of the apo secretions remain unknown. We aimed to 1) determine the amount and orientation (apical-maternal versus basal-fetal) of placentally secreted apoA1 and apoE using human perfused placenta and primary trophoblast cell (PTC) culture, 2) compare apoA1 and apoE secretions of PTC with that of hepatocytes and 3) associate the obtained results with human blood levels by determining apoA1 and apoE concentrations in maternal and fetal serum samples. In perfused placenta and serum samples, apoA1 and apoE concentrations were significantly higher at the maternal compared to the fetal side. For apoE a similar trend was found in PTC. For apoA1, the secretion to the apical side declined over time while release to the basal side was stable resulting in significantly different apoA1 concentrations between both sides. Unexpectedly, PTC secreted significantly higher amounts of apoA1 and apoE compared to hepatocytes. Our data indicate that the placenta may play an important role in maternal and fetal cholesterol homeostasis via secretion of anti-atherogenic apos.

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.

Ex Vivo Dual Perfusion of the Human Placenta: Disease Simulation, Therapeutic Pharmacokinetics and Analysis of Off-Target Effects

In recent years ex vivo dual perfusion of the human placental lobule is seeing an international renaissance in its application to understanding fetal health and development. Here, we discuss the methods and uses of this technique in the evaluation of (1) vascular function, (2) transplacental clearance, (3) hemodynamic and oxygenation changes associated with pregnancy complications on placental structure and function, and (4) placental toxicology and post-perfusion evaluation of tissue architecture.

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.

An international network (PlaNet) to evaluate a human placental testing platform for chemicals safety testing in pregnancy

The human placenta is a critical life-support system that nourishes and protects a rapidly growing fetus; a unique organ, species specific in structure and function. We consider the pressing challenge of providing additional advice on the safety of prescription medicines and environmental exposures in pregnancy and how ex vivo and in vitro human placental models might be advanced to reproducible human placental test systems (HPTSs), refining a weight of evidence to the guidance given around compound risk assessment during pregnancy. The placental pharmacokinetics of xenobiotic transfer, dysregulated placental function in pregnancy-related pathologies and influx/efflux transporter polymorphisms are a few caveats that could be addressed by HPTSs, not the specific focus of current mammalian reproductive toxicology systems. An international consortium, "PlaNet", will bridge academia, industry and regulators to consider screen ability and standardisation issues surrounding these models, with proven reproducibility for introduction into industrial and clinical practice.

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.

Cytokines, angiogenic, and antiangiogenic factors and bioactive lipids in preeclampsia

Preeclampsia is a low-grade systemic inflammatory condition in which oxidative stress and endothelial dysfunction occurs. Plasma levels of soluble receptor for vascular endothelial growth factor (VEGFR)-1, also known as sFlt1 (soluble fms-like tyrosine kinase 1), an antiangiogenic factor have been reported to be elevated in preeclampsia. It was reported that pregnant mice deficient in catechol-O-methyltransferase (COMT) activity show a preeclampsia-like phenotype due to a deficiency or absence of 2-methoxyoestradiol (2-ME), a natural metabolite of estradiol that is elevated during the third trimester of normal human pregnancy. Additionally, autoantibodies (AT1-AAs) that bind and activate the angiotensin II receptor type 1 a (AT1 receptor) also have a role in preeclampsia. None of these abnormalities are consistently seen in all the patients with preeclampsia and some of them are not specific to pregnancy. Preeclampsia could occur due to an imbalance between pro- and antiangiogenic factors. VEGF, an angiogenic factor, is necessary for the transport of polyunsaturated fatty acids (PUFAs) to endothelial cells. Hence reduced VEGF levels decrease the availability of PUFAs to endothelial cells. This leads to a decrease in the formation of anti-inflammatory and angiogenic factors: lipoxins, resolvins, protectins, and maresins from PUFAs. Lipoxins, resolvins, protectins, maresins, and PUFAs suppress insulin resistance; activation of leukocytes, platelets, and macrophages; production of interleukin-6 and tumor necrosis factor-α; and oxidative stress and endothelial dysfunction; and enhance production of prostacyclin and nitric oxide (NO). Estrogen enhances the formation of lipoxin A4 and NO. PUFAs also augment the production of NO and inhibit the activity of angiotensin-converting enzyme and antagonize the actions of angiotensin II. Thus, PUFAs can prevent activation of angiotensin II receptor type 1 a (AT1 receptor). Patients with preeclampsia have decreased plasma phospholipid concentrations of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), the precursors of lipoxins (from AA), resolvins (from EPA and DHA), and protectins (from DHA) and prostaglandin E1 (PGE1 from DGLA: dihomo-γ-linolenic acid) and prostacyclin (PGI2 derived from AA). Based on these evidences, it is proposed that preeclampsia may occur due to deficiency of PUFAs and their anti-inflammatory products: lipoxins, resolvins, protectins, and maresins.

IFPA senior award lecture: Energy metabolism of human placental tissue studied by ex vivo perfusion of an isolated cotyledon

BACKGROUND

This is a historical review of the method of "Ex vivo dual perfusion of a human placental cotyledon", which was first described by M. Panigel in 1967. The subsequent evolution of this method is described with particular emphasis on energy metabolism of human placental tissue under ex vivo conditions.

METHOD

For perfusion of the foetal compartment a pair of a chorionic arterial and venous vessel is cannulated. In the original method a remnant of the spiral artery of that cotyledon was catheterized to provide access to the maternal compartment. To simplify the procedure access to the intervillous space later was achieved by penetration of the decidual plate with 3 to 5 cannulae.

RESULTS

Due to a remarkable tolerance of ischaemia energy dependent transport of amino acids and de novo synthesis of proteins remain functional in spite of a delay of 20 to 30 min. until start of the two ex vivo circuits. With medium containing only physically dissolved oxygen the high demand of oxygen of the tissue can only partially be met. Chronic hypoxia leads to metabolic reprogramming with reduction in mitochondrial oxygen consumption and an increase in anaerobic glycolysis. Addition of erythrocytes to the medium is highly effective in increasing oxygen supply at physiological partial pressure with stimulation of aerobic glycolysis and de novo synthesis of proteins. Increasing the number of maternal cannulae leads to a better distribution of haemoglobin free medium with physiological partial pressure of oxygen giving median values of oxygen content inside the intervillous space close to target values.

CONCLUSION

Ex vivo dual perfusion of a human placental cotyledon allows to study functional aspects of this organ under close to in vivo conditions. A remarkable tolerance of ischaemia permits a start of dual perfusion ex vivo with a delay of 20 to 30 min. after delivery without significant tissue damage.