Placental physiology monitored by hyperpolarized dynamic 13C magnetic resonance

Magnetic resonance imaging of placental intralobule structure and function in a preclinical nonhuman primate model†

Although the central role of adequate blood flow and oxygen delivery is known, the lack of optimized imaging modalities to study placental structure has impeded our understanding of its vascular function. Magnetic resonance imaging is increasingly being applied in this field, but gaps in knowledge remain, and further methodological developments are needed. In particular, the ability to distinguish maternal from fetal placental perfusion and the understanding of how individual placental lobules are functioning are lacking. The potential clinical benefits of developing noninvasive tools for the in vivo assessment of blood flow and oxygenation, two key determinants of placental function, are tremendous. Here, we summarize a number of structural and functional magnetic resonance imaging techniques that have been developed and applied in animal models and studies of human pregnancy over the past decade. We discuss the potential applications and limitations of these approaches. Their combination provides a novel source of contrast to allow analysis of placental structure and function at the level of the lobule. We outline the physiological mechanisms of placental T2 and T2* decay and devise a model of how tissue composition affects the observed relaxation properties. We apply this modeling to longitudinal magnetic resonance imaging data obtained from a preclinical pregnant nonhuman primate model to provide initial proof-of-concept data for this methodology, which quantifies oxygen transfer and placental structure across and between lobules. This method has the potential to improve our understanding and clinical management of placental insufficiency once validation in a larger nonhuman primate cohort is complete.

Glycolysis: A fork in the path of normal and pathological pregnancy

Glucose metabolism is vital to the survival of living organisms. Since the discovery of the Warburg effect in the 1920s, glycolysis has become a major research area in the field of metabolism. Glycolysis has been extensively studied in the field of cancer and is considered as a promising therapeutic target. However, research on the role of glycolysis in pregnancy is limited. Recent evidence suggests that blastocysts, trophoblasts, decidua, and tumors all acquire metabolic energy at specific stages in a highly similar manner. Glycolysis, carefully controlled throughout pregnancy, maintains a dynamic and coordinated state, so as to maintain the homeostasis of the maternal-fetal interface and ensure normal gestation. In the present review, we investigate metabolic remodeling and the selective propensity of the embryo and placenta for glycolysis. We then address dysregulated glycolysis that occurs in the cellular interactive network at the maternal-fetal interface in miscarriage, preeclampsia, fetal growth restriction, and gestational diabetes mellitus. We provide new insights into the field of maternal-fetal medicine from a metabolic perspective, thus revealing the mystery of human pregnancy.

The human placenta project: Funded studies, imaging technologies, and future directions

The placenta plays a critical role in fetal development. It serves as a multi-functional organ that protects and nurtures the fetus during pregnancy. However, despite its importance, the intricacies of placental structure and function in normal and diseased states have remained largely unexplored. Thus, in 2014, the National Institute of Child Health and Human Development launched the Human Placenta Project (HPP). As of May 2023, the HPP has awarded over $101 million in research funds, resulting in 41 funded studies and 459 publications. We conducted a comprehensive review of these studies and publications to identify areas of funded research, advances in those areas, limitations of current research, and continued areas of need. This paper will specifically review the funded studies by the HPP, followed by an in-depth discussion on advances and gaps within placental-focused imaging. We highlight the progress within magnetic reasonance imaging and ultrasound, including development of tools for the assessment of placental function and structure.

MR-Nucleomics: The study of pathological cellular processes with multinuclear magnetic resonance spectroscopy and imaging in vivo

Clinical medicine has experienced a rapid development in recent decades, during which therapies targeting specific cellular signaling pathways, or specific cell surface receptors, have been increasingly adopted. While these developments in clinical medicine call for improved precision in diagnosis and treatment monitoring, modern medical imaging methods are restricted mainly to anatomical imaging, lagging behind the requirements of precision medicine. Although positron emission tomography and single photon emission computed tomography have been used clinically for studies of metabolism, their applications have been limited by the exposure risk to ionizing radiation, the subsequent limitation in repeated and longitudinal studies, and the incapability in assessing downstream metabolism. Magnetic resonance spectroscopy (MRS) or spectroscopic imaging (MRSI) are, in theory, capable of assessing molecular activities in vivo, although they are often limited by sensitivity. Here, we review some recent developments in MRS and MRSI of multiple nuclei that have potential as molecular imaging tools in the clinic.

Hyperpolarized water as universal sensitivity booster in biomolecular NMR

NMR spectroscopy is the only method to access the structural dynamics of biomolecules at high (atomistic) resolution in their native solution state. However, this method's low sensitivity has two important consequences: (i) typically experiments have to be performed at high concentrations that increase sensitivity but are not physiological, and (ii) signals have to be accumulated over long periods, complicating the determination of interaction kinetics on the order of seconds and impeding studies of unstable systems. Both limitations are of equal, fundamental relevance: non-native conditions are of limited pharmacological relevance, and the function of proteins, enzymes and nucleic acids often relies on their interaction kinetics. To overcome these limitations, we have developed applications that involve 'hyperpolarized water' to boost signal intensities in NMR of proteins and nucleic acids. The technique includes four stages: (i) preparation of the biomolecule in partially deuterated buffers, (ii) preparation of 'hyperpolarized' water featuring enhanced ¹H NMR signals via cryogenic dynamic nuclear polarization, (iii) sudden melting of the cryogenic pellet and dissolution of the protein or nucleic acid in the hyperpolarized water (enabling spontaneous exchanges of protons between water and target) and (iv) recording signal-amplified NMR spectra targeting either labile ¹H or neighboring ¹⁵N/¹³C nuclei in the biomolecule. Water in the ensuing experiments is used as a universal 'hyperpolarization' agent, rendering the approach versatile and applicable to any biomolecule possessing labile hydrogens. Thus, questions can be addressed, ranging from protein and RNA folding problems to resolving structure-function relationships of intrinsically disordered proteins to investigating membrane interactions.

Emerging placental biomarkers of health and disease through advanced magnetic resonance imaging (MRI)

Placental dysfunction is a major cause of fetal demise, fetal growth restriction, and preterm birth, as well as significant maternal morbidity and mortality. Infant survivors of placental dysfunction are at elevatedrisk for lifelong neuropsychiatric morbidity. However, despite the significant consequences of placental disease, there are no clinical tools to directly and non-invasively assess and measure placental function in pregnancy. In this work, we will review advanced MRI techniques applied to the study of the in vivo human placenta in order to better detail placental structure, architecture, and function. We will discuss the potential of these measures to serve as optimal biomarkers of placental dysfunction and review the evidence of these tools in the discrimination of health and disease in pregnancy. Efforts to advance our understanding of in vivo placental development are necessary if we are to optimize healthy pregnancy outcomes and prevent brain injury in successive generations. Current management of many high-risk pregnancies cannot address placental maldevelopment or injury, given the standard tools available to clinicians. Once accurate biomarkers of placental development and function are constructed, the subsequent steps will be to introduce maternal and fetal therapeutics targeting at optimizing placental function. Applying these biomarkers in future studies will allow for real-time assessments of safety and efficacy of novel interventions aimed at improving maternal-fetal well-being.

THz-enhanced dynamic nuclear polarized liquid spectrometer

Dynamic nuclear polarization (DNP) technology can be utilized to dramatically enhance NMR signal. In this paper, we report on the development of a self-constructed 5 T DNP spectrometer for liquid samples and the ¹³C DNP enhancement achieved with this spectrometer. The DNP spectrometer is comprised of a wide-bore superconducting magnet, a home-made console, a dual resonance probe and a self-built 140 GHz microwave source for the spectrometer. Specifically, a microwave source of traveling wave tube (TWT) amplifier has been developed, which can provide a maximum power output of 4.4 W and a wide frequency tuning range of 1 GHz. The excellent performance of our built liquid-state DNP spectrometer is verified by the observation of more than 100-fold DNP enhancement of the ¹³C NMR signal for liquid ¹³CCl₄ sample. Our result shows the superiority of DNP technology in the liquid-state high-field NMR spectrometer.

Clinical translation of hyperpolarized 13 C pyruvate and urea MRI for simultaneous metabolic and perfusion imaging

Purpose

The combined hyperpolarized (HP) ¹³C pyruvate and urea MRI has provided a simultaneous assessment of glycolytic metabolism and tissue perfusion for improved cancer diagnosis and therapeutic evaluation in preclinical studies. This work aims to translate this dual‐probe HP imaging technique to clinical research.

Methods

A co‐polarization system was developed where [1‐¹³C]pyruvic acid (PA) and [¹³C, ¹⁵N₂]urea in water solution were homogeneously mixed and polarized on a 5T SPINlab system. Physical and chemical characterizations and toxicology studies of the combined probe were performed. Simultaneous metabolic and perfusion imaging was performed on a 3T clinical MR scanner by alternatively applying a multi‐slice 2D spiral sequence for [1‐¹³C]pyruvate and its downstream metabolites and a 3D balanced steady‐state free precession (bSSFP) sequence for [¹³C, ¹⁵N₂]urea.

Results

The combined PA/urea probe has a glass‐formation ability similar to neat PA and can generate nearly 40% liquid‐state ¹³C polarization for both pyruvate and urea in 3‐4 h. A standard operating procedure for routine on‐site production was developed and validated to produce 40 mL injection product of approximately 150 mM pyruvate and 35 mM urea. The toxicology study demonstrated the safety profile of the combined probe. Dynamic metabolite‐specific imaging of [1‐¹³C]pyruvate, [1‐¹³C]lactate, [1‐¹³C]alanine, and [¹³C, ¹⁵N₂]urea was achieved with adequate spatial (2.6 mm × 2.6 mm) and temporal resolution (4.2 s), and urea images showed reduced off‐resonance artifacts due to the J_CN coupling.

Conclusion

The reported technical development and translational studies will lead to the first‐in‐human dual‐agent HP MRI study and mark the clinical translation of the first HP ¹³C MRI probe after pyruvate.

Improving deuterium metabolic imaging (DMI) signal-to-noise ratio by spectroscopic multi-echo bSSFP: A pancreatic cancer investigation

PURPOSE

Deuterium metabolic imaging (DMI) maps the uptake of deuterated precursors and their conversion into lactate and other markers of tumor metabolism. Even after leveraging ² H's short T₁ s, DMI's signal-to-noise ratio (SNR) is limited. We hypothesize that a multi-echo balanced steady-state free precession (ME-bSSFP) approach would increase SNR compared to chemical shift imaging (CSI), while achieving spectral isolation of the metabolic precursors and products.

METHODS

Suitably tuned ² H ME-bSSFP (five echo times [TEs], ΔTE = 2.2 ms, repetition time [TR]/flip-angle = 12 ms/60°) was implemented at 15.2T and compared to CSI (TR/flip-angle = 95 ms/90°) regarding SNR and spectral isolation, in simulations, in deuterated phantoms and for the in vivo diagnosis of a mouse tumor model of pancreatic adenocarcinoma (N = 10).

RESULTS

Simulations predicted an SNR increase vs. CSI of 3-5, and that the peaks of ² H-water, ² H_6,6' -glucose, and ² H_3,3' -lactate can be well isolated by ME-bSSFP; phantoms confirmed this. In vivo, at equal spatial resolution (1.25 × 1.25 mm² ) and scan time (10 min), ² H_6,6' -glucose's and ² H_3,3' -lactate's SNR were indeed higher for bSSFP than for CSI, three-fold for glucose (57 ± 30 vs. 19 ± 11, P < .001), doubled for water (13 ± 5 vs. 7 ± 3, P = .005). The time courses and overall localization of all metabolites agreed well, comparing CSI against ME-bSSFP. However, a clearer localization of glucose in kidneys and bladder, the detection of glucose-avid rims in certain tumors, and a heterogeneous pattern of intra-tumor lactate production could only be observed using ME-bSSFP's higher resolution.

CONCLUSIONS

ME-bSSFP provides greater SNR per unit time than CSI, providing for higher spatial resolution mapping of glucose uptake and lactate production in tumors.

Deuterium Magnetic Resonance Imaging and the Discrimination of Fetoplacental Metabolism in Normal and L-NAME-Induced Preeclamptic Mice

Recent magnetic resonance studies in healthy and cancerous organs have concluded that deuterated metabolites possess highly desirable properties for mapping non-invasively and, as they happen, characterizing glycolysis and other biochemical processes in animals and humans. A promising avenue of this deuterium metabolic imaging (DMI) approach involves looking at the fate of externally administered ²H_6,6′-glucose, as it is taken up and metabolized into different products as a function of time. This study employs deuterium magnetic resonance to follow the metabolism of wildtype and preeclamptic pregnant mice models, focusing on maternal and fetoplacental organs over ≈2 h post-injection. ²H_6,6′-glucose uptake was observed in the placenta and in specific downstream organs such as the fetal heart and liver. Main metabolic products included ²H_3,3′-lactate and ²H-water, which were produced in individual fetoplacental organs with distinct time traces. Glucose uptake in the organs of most preeclamptic animals appeared more elevated than in the control mice (p = 0.02); also higher was the production of ²H-water arising from this glucose. However, the most notable differences arose in the ²H_3,3′-lactate concentration, which was ca. two-fold more abundant in the placenta (p = 0.005) and in the fetal (p = 0.01) organs of preeclamptic-like animals, than in control mice. This is consistent with literature reports about hypoxic conditions arising in preeclamptic and growth-restricted pregnancies, which could lead to an enhancement in anaerobic glycolysis. Overall, the present measurements suggest that DMI, a minimally invasive approach, may offer new ways of studying and characterizing health and disease in mammalian pregnancies, including humans.

Schulte R, Laustsen C. Comprehensive Literature Review of Hyperpolarized Carbon-13 MRI: The Road to Clinical Application

This review provides a comprehensive assessment of the development of hyperpolarized (HP) carbon-13 metabolic MRI from the early days to the present with a focus on clinical applications. The status and upcoming challenges of translating HP carbon-13 into clinical application are reviewed, along with the complexity, technical advancements, and future directions. The road to clinical application is discussed regarding clinical needs and technological advancements, highlighting the most recent successes of metabolic imaging with hyperpolarized carbon-13 MRI. Given the current state of hyperpolarized carbon-13 MRI, the conclusion of this review is that the workflow for hyperpolarized carbon-13 MRI is the limiting factor.

Effect of pre-operative bicarbonate infusion on maternal and perinatal outcomes among women with obstructed labour in Mbale hospital: A double blind randomized controlled trial

INTRODUCTION

Oral bicarbonate solution is known to improve both maternal and perinatal outcomes among women with abnormal labour (dystocia). Its effectiveness and safety among women with obstructed labour is not known.

OBJECTIVE

To determine the effect and safety of a single-dose preoperative infusion of sodium bicarbonate on maternal and fetal blood lactate and clinical outcomes among women with obstructed labour (OL) in Mbale hospital.

METHODS

We conducted a double blind, randomised controlled trial from July 2018 to September 2019. The participants were women with OL at term (≥37 weeks gestation), carrying a singleton pregnancy with no other obstetric emergency, medical comorbidity or laboratory derangements.

INTERVENTION

A total of 477 women with OL were randomized to receive 50ml of 8.4% sodium bicarbonate (238 women) or 50 mL of 0.9% sodium chloride (239 women). In both the intervention and controls arms, each participant was preoperatively given a single dose intravenous bolus. Every participant received 1.5 L of normal saline in one hour as part of standard preoperative care.

OUTCOME MEASURES

Our primary outcome was the mean difference in maternal venous blood lactate at one hour between the two arms. The secondary outcomes were umbilical cord blood lactate levels at birth, neonatal sepsis and early neonatal death upto 7 days postnatal, as well as the side effects of sodium bicarbonate, primary postpartum hemorrhage, maternal sepsis and mortality at 14 days postpartum.

RESULTS

The median maternal venous lactate was 6.4 (IQR 3.3-12.3) in the intervention and 7.5 (IQR 4.0-15.8) in the control group, with a statistically non-significant median difference of 1.2 mmol/L; p-value = 0.087. Vargha and Delaney effect size was 0.46 (95% CI 0.40-0.51) implying very little if any effect at all.

CONCLUSION

The 4.2g of preoperative intravenous sodium bicarbonate was safe but made little or no difference on blood lactate levels.

TRIAL REGISTRATION

PACTR201805003364421.

The application of in utero magnetic resonance imaging in the study of the metabolic and cardiovascular consequences of the developmental origins of health and disease

Observing fetal development in utero is vital to further the understanding of later-life diseases. Magnetic resonance imaging (MRI) offers a tool for obtaining a wealth of information about fetal growth, development, and programming not previously available using other methods. This review provides an overview of MRI techniques used to investigate the metabolic and cardiovascular consequences of the developmental origins of health and disease (DOHaD) hypothesis. These methods add to the understanding of the developing fetus by examining fetal growth and organ development, adipose tissue and body composition, fetal oximetry, placental microstructure, diffusion, perfusion, flow, and metabolism. MRI assessment of fetal growth, organ development, metabolism, and the amount of fetal adipose tissue could give early indicators of abnormal fetal development. Noninvasive fetal oximetry can accurately measure placental and fetal oxygenation, which improves current knowledge on placental function. Additionally, measuring deficiencies in the placenta’s transport of nutrients and oxygen is critical for optimizing treatment. Overall, the detailed structural and functional information provided by MRI is valuable in guiding future investigations of DOHaD.

Lactate Limits T Cell Proliferation via the NAD(H) Redox State

Immune cell function is influenced by metabolic conditions. Low-glucose, high-lactate environments, such as the placenta, gastrointestinal tract, and the tumor microenvironment, are immunosuppressive, especially for glycolysis-dependent effector T cells. We report that nicotinamide adenine dinucleotide (NAD⁺), which is reduced to NADH by lactate dehydrogenase in lactate-rich conditions, is a key point of metabolic control in T cells. Reduced NADH is not available for NAD⁺-dependent enzymatic reactions involving glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and 3-phosphoglycerate dehydrogenase (PGDH). We show that increased lactate leads to a block at GAPDH and PGDH, leading to the depletion of post-GAPDH glycolytic intermediates, as well as the 3-phosphoglycerate derivative serine that is known to be important for T cell proliferation. Supplementing serine rescues the ability of T cells to proliferate in the presence of lactate-induced reductive stress. Directly targeting the redox state may be a useful approach for developing novel immunotherapies in cancer and therapeutic immunosuppression.

Quinn et al. report that lactate has an acidity-independent suppressive effect on effector T cell proliferation mediated through a shift from NAD⁺ to NADH (lactate-induced reductive stress). This impairs glycolysis and glucose-derived serine production, which is required for effector T cell proliferation.

Magnetic resonance imaging for early pregnancy diagnosis in the laboratory rat

Pregnancy diagnosis and embryo counting are important end points in reproductive, developmental biology and toxicology studies. The purpose of the present study was to assess the feasibility and efficacy of magnetic resonance imaging (MRI) for early pregnancy diagnosis and embryo counting in the laboratory rat. Female Wistar rats were subjected to whole-body MRI scanning using a 1.5T MRI scanner, employing a isotropic T2-weighted 3D short-tau inversion recovery sequence from day 8 to day 12 post coitum (pc) or without prior mating, under general anaesthesia for pregnancy diagnosis and embryo counting. MRI examination was followed by laparotomy and visual inspection of the uterus to verify MRI findings. By day 8 pc, uterine bulges, characteristic of pregnancy, were depicted as oval-shaped structures of high intensity signal. By day 10 pc, embryonic vesicles were detected at the medial side of the uterine bulges. Pregnancy was diagnosed with 0% false-negative diagnosis and 100% accuracy by day 11 pc, while embryos were counted with 100% accuracy by day 12 pc. In conclusion, MRI proved to be a feasible and reliable non-invasive imaging method of early pregnancy diagnosis and embryo counting in the laboratory rat.

Regulation of maternal-fetal metabolic communication

Pregnancy may be the most nutritionally sensitive stage in the life cycle, and improved metabolic health during gestation and early postnatal life can reduce the risk of chronic disease in adulthood. Successful pregnancy requires coordinated metabolic, hormonal, and immunological communication. In this review, maternal-fetal metabolic communication is defined as the bidirectional communication of nutritional status and metabolic demand by various modes including circulating metabolites, endocrine molecules, and other secreted factors. Emphasis is placed on metabolites as a means of maternal-fetal communication by synthesizing findings from studies in humans, non-human primates, domestic animals, rabbits, and rodents. In this review, fetal, placental, and maternal metabolic adaptations are discussed in turn. (1) Fetal macronutrient needs are summarized in terms of the physiological adaptations in place to ensure their proper allocation. (2) Placental metabolite transport and maternal physiological adaptations during gestation, including changes in energy budget, are also discussed. (3) Maternal nutrient limitation and metabolic disorders of pregnancy serve as case studies of the dynamic nature of maternal-fetal metabolic communication. The review concludes with a summary of recent research efforts to identify metabolites, endocrine molecules, and other secreted factors that mediate this communication, with particular emphasis on serum/plasma metabolomics in humans, non-human primates, and rodents. A better understanding of maternal-fetal metabolic communication in health and disease may reveal novel biomarkers and therapeutic targets for metabolic disorders of pregnancy.

Diffusion and perfusion MRI of normal, preeclamptic and growth-restricted mice models reveal clear fetoplacental differences

Diffusion-weighted MRI on rodents could be valuable to evaluate pregnancy-related dysfunctions, particularly in knockout models whose biological nature is well understood. Echo Planar Imaging’s sensitivity to motions and to air/water/fat heterogeneities, complicates these studies in the challenging environs of mice abdomens. Recently developed MRI methodologies based on SPatiotemporal ENcoding (SPEN) can overcome these obstacles, and deliver diffusivity maps at ≈150 µm in-plane resolutions. The present study exploits these capabilities to compare the development in wildtype vs vascularly-altered mice. Attention focused on the various placental layers—deciduae, labyrinth, trophoblast, fetal vessels—that the diffusivity maps could resolve. Notable differences were then observed between the placental developments of wildtype vs diseased mice; these differences remained throughout the pregnancies, and were echoed by perfusion studies relying on gadolinium-based dynamic contrast-enhanced MRI. Longitudinal monitoring of diffusivity in the animals throughout the pregnancies also showed differences between the development of the fetal brains in the wildtype and vascularly-altered mice, even if these disparities became progressively smaller as the pregnancies progressed. These results are analyzed on the basis of the known physiology of normal and preeclamptic pregnancies, as well as in terms of the potential that they might open for the early detection of disorders in human pregnancies.

Ex Vivo Human Placenta Perfusion, Metabolic and Functional Imaging for Obstetric Research-A Feasibility Study

Placenta metabolism is closely linked to pregnancy outcome, and few modalities are currently available for studying the human placenta. Here, we aimed to investigate a novel ex vivo human placenta perfusion system for metabolic imaging using hyperpolarized [1-¹³C]pyruvate. The metabolic effects of 3 different human placentas were investigated using functional and metabolic magnetic resonance imaging. The placenta glucose metabolism and hemodynamics were characterized with hyperpolarized [1-¹³C]pyruvate magnetic resonance imaging and by dynamic contrast-enhanced (DCE) imaging. Hyperpolarized [1-¹³C]pyruvate showed a decrease in the ¹³C-lactate/¹³C-pyruvate ratio from the highest to the lowest metabolic active placenta. The metabolic profile was complemented by a more homogenous distributed hemodynamic response, with a longer mean transit time and higher blood volume. This study shows different placenta metabolic and hemodynamic features associated with the placenta functional status using hyperpolarized magnetic resonance ex vivo. This study supports further studies using ex vivo metabolic imaging of the placenta alterations associated with pregnancy complications.

Acquisition strategies for spatially resolved magnetic resonance detection of hyperpolarized nuclei

Hyperpolarization is an emerging method in magnetic resonance imaging that allows nuclear spin polarization of gases or liquids to be temporarily enhanced by up to five or six orders of magnitude at clinically relevant field strengths and administered at high concentration to a subject at the time of measurement. This transient gain in signal has enabled the non-invasive detection and imaging of gas ventilation and diffusion in the lungs, perfusion in blood vessels and tissues, and metabolic conversion in cells, animals, and patients. The rapid development of this method is based on advances in polarizer technology, the availability of suitable probe isotopes and molecules, improved MRI hardware and pulse sequence development. Acquisition strategies for hyperpolarized nuclei are not yet standardized and are set up individually at most sites depending on the specific requirements of the probe, the object of interest, and the MRI hardware. This review provides a detailed introduction to spatially resolved detection of hyperpolarized nuclei and summarizes novel and previously established acquisition strategies for different key areas of application.

Unique microRNA Signals in Plasma Exosomes from Pregnancies Complicated by Preeclampsia

Although preeclampsia is a common and serious complication of pregnancy, insight into its pathobiology and diagnosis is lacking. Circulating plasma exosomes, which contain RNA and other molecules and have recently become accessible for diagnostics, may be informative in this regard. We tested the hypothesis that preeclampsia may affect the miRNA cargo within circulating maternal blood exosomes. We collected plasma from 60 pregnant women at term, including 20 women with pregnancy complicated by preeclampsia, and 20 women with fetal growth restriction and 20 with healthy pregnancy, serving as controls. We isolated exosomes from the maternal plasma by continuous density gradient ultracentrifugation. Our main outcome variable was exosomal miRNA cargo, analyzed by quantitative polymerase chain reaction-based TaqMan advanced miRNA assay in a card format and the expression of differentially expressed exosomal miRNA in whole plasma from the same participants. We found that 7 miRNA species were differentially expressed in exosomes from women with preeclampsia and those from controls. In contrast, there was no significant difference in exosomal miRNA expression between women with fetal growth restriction and controls. The results were not affected by fetal sex. Only one of the preeclampsia-related, differentially expressed exosomal miRNAs was significantly different in whole plasma miRNA analysis. We concluded that unlike whole plasma miRNA, exosomes extracted from the plasma of women with preeclampsia exhibit a unique miRNA profile, suggesting that plasma exosomal miRNA could provide insight into the pathophysiology of preeclampsia, and may play a role in disease diagnostics.

Placental MRI and its application to fetal intervention

OBJECTIVE

Magnetic resonance imaging (MRI) of placental invasion has been part of clinical practice for many years. The possibility of being better able to assess placental vascularization and function using MRI has multiple potential applications. This review summarises up-to-date research on placental function using different MRI modalities.

METHOD

We discuss how combinations of these MRI techniques have much to contribute to fetal conditions amenable for therapy such as singletons at high risk for fetal growth restriction (FGR) and monochorionic twin pregnancies for planning surgery and counselling for selective growth restriction and transfusion conditions.

RESULTS

The whole placenta can easily be visualized on MRI, with a clear boundary against the amniotic fluid, and a less clear placental-uterine boundary. Contrasts such as diffusion weighted imaging, relaxometry, blood oxygenation level dependent MRI and flow and metabolite measurement by dynamic contrast enhanced MRI, arterial spin labeling, or spectroscopic techniques are contributing to our wider understanding of placental function.

CONCLUSION

The future of placental MRI is exciting, with the increasing availability of multiple contrasts and new models that will boost the capability of MRI to measure oxygen saturation and placental exchange, enabling examination of placental function in complicated pregnancies.

High-Resolution Probing of Heterogeneous Samples by Spatially Selective Pure Shift NMR Spectroscopy

Liquid NMR spectroscopy generally encounters two major challenges for high-resolution measurements of heterogeneous samples, namely, magnetic field inhomogeneity caused by spatial variations in magnetic susceptibility and spectral congestion induced by crowded NMR resonances. In this study, we demonstrate a spatially selective pure shift NMR approach for high-resolution probing of heterogeneous samples by suppressing effects of field inhomogeneity and J coupling simultaneously. A Fourier phase encoding strategy is proposed and implemented for spatially selective pure shift experiments to enhance signal intensity and further boost the applicability. The spatially selective pure shift method can serve as an effective tool for high-resolution probing of heterogeneous samples, thus presenting interesting prospects for extensive applications in the fields of chemistry, physics, biology, and food science.

Effect of preoperative bicarbonate infusion on maternal and perinatal outcomes of obstructed labour in Mbale Regional Referral Hospital: a study protocol for a randomised controlled trial

INTRODUCTION

To improve maternal and fetal outcomes among patients with obstructed labour (OL) in low-resource settings, the associated electrolyte and metabolic derangements must be adequately corrected. Oral fluid intake during labour and preoperative intravenous fluid replacement following OL corrects the associated dehydration and electrolyte changes, but it does not completely reverse the metabolic acidosis, that is, a cause of intrapartum birth asphyxia and a risk factor for primary postpartum haemorrhage due to uterine atony. Sodium bicarbonate is a safe, effective, cheap and readily available acid buffer, that is widely used by sportspeople to improve performance. It also appears to improve fetal and maternal outcomes in abnormally progressing labour. However, its effects on maternal and fetal outcomes among patients with OL is unknown. We aim at establishing the effect of a single-dose preoperative infusion of sodium bicarbonate on maternal and fetal lactate levels and clinical outcomes among patients with OL.

METHODS AND ANALYSIS

This will be a double blind, randomised controlled clinical phase IIb trial. We will randomise 478 patients with OL to receive either 50 mL of placebo with standard preoperative infusion of normal saline (1.5 L) or 4.2 g of sodium bicarbonate solution (50 mL of 50 mmol/L) with the preoperative infusion of normal saline (1.5 L). The primary outcome will be mean lactate levels in maternal capillary blood at 1 hour after study drug administration and in the arterial cord blood at birth. We will use the intention-to-treat analysis approach. Secondary outcomes will include safety, maternal and fetal morbidity and mortality up to 14 days postpartum.

ETHICS AND DISSEMINATION

Makerere University School of Medicine Research and Ethics Committee and Uganda National Council for Science and Technology have approved the protocol. Each participant will give informed consent at enrollment.

TRIAL REGISTRATION NUMBER

PACTR201805003364421.

Enhanced hyperpolarized chemical shift imaging based on a priori segmented information

PURPOSE

The purpose of the study was to develop an approach for improving the resolution and sensitivity of hyperpolarized ¹³ C MRSI based on a priori anatomical information derived from featured, water-based ¹ H images.

METHODS

A reconstruction algorithm exploiting ¹ H MRI for the redefinition of the ¹³ C MRSI anatomies was developed, based on a modification of the spectroscopy with linear algebraic modeling (SLAM) principle. To enhance ¹³ C spatial resolution and reduce spillover effects without compromising SNR, this model was extended by endowing it with a search allowing smooth variations in the ¹³ C MR intensity within the targeted regions of interest.

RESULTS

Experiments were performed in vitro on enzymatic solutions and in vivo on rodents, based on the administration of ¹³ C-enriched hyperpolarized pyruvate and urea. The spectral images reconstructed for these substrates and from metabolic products based on predefined ¹ H anatomical compartments using the new algorithm, compared favorably with those arising from conventional Fourier-based analyses of the same data. The new approach also delivered reliable kinetic ¹³ C results, for the kind of processes and timescales usually targeted by hyperpolarized MRSI.

CONCLUSION

A simple, flexible strategy is introduced to boost the sensitivity and resolution provided by hyperpolarized ¹³ C MRSI, based on readily available ¹ H MR information.