The effects of betamethasone on allopregnanolone concentrations and brain development in preterm fetal sheep

Cellular origins and translational approaches to congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a complex developmental abnormality characterized by abnormal lung development, a diaphragmatic defect and cardiac dysfunction. Despite significant advances in management of CDH, mortality and morbidity continue to be driven by pulmonary hypoplasia, pulmonary hypertension, and cardiac dysfunction. The etiology of CDH remains unknown, but CDH is presumed to be caused by a combination of genetic susceptibility and external/environmental factors. Current research employs multi-omics technologies to investigate the molecular profile and pathways inherent to CDH. The aim is to discover the underlying pathogenesis, new biomarkers and ultimately novel therapeutic targets. Stem cells and their cargo, non-coding RNAs and agents targeting inflammation and vascular remodeling have produced promising results in preclinical studies using animal models of CDH. Shortcomings in current therapies combined with an improved understanding of the pathogenesis in CDH have given rise to novel promising experimental treatments that are currently being evaluated in clinical trials. This review provides insight into current developments in translational research, ranging from the cellular origins of abnormal cardiopulmonary development in CDH and the identification of novel treatment targets in preclinical CDH models at the bench and their translation to clinical trials at the bedside.

Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in 'developed' countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.

Association of Fetal Growth Restriction With Neurocognitive Function After Repeated Antenatal Betamethasone Treatment vs Placebo: Secondary Analysis of the ACTORDS Randomized Clinical Trial

Importance

Repeated doses of antenatal betamethasone are recommended for women at less than 32 weeks' gestation with ongoing risk of preterm birth. However, concern that this therapy may be associated with adverse neurocognitive effects in children with fetal growth restriction (FGR) remains.

Objective

To determine the influence of FGR on the effects of repeated doses of antenatal betamethasone on neurocognitive function in midchildhood.

Design, Setting, and Participants

This preplanned secondary analysis of data from the multicenter Australasian Collaborative Trial of Repeat Doses of Corticosteroids (ACTORDS) included women at less than 32 weeks' gestation with ongoing risk of preterm birth (<32 weeks) at least 7 days after an initial course of antenatal corticosteroids who were treated at 23 hospitals across Australia and New Zealand from April 1, 1998, through July 20, 2004. Participants were randomized to intramuscular betamethasone or saline placebo; treatment could be repeated weekly if the woman was judged to be at continued risk of preterm birth. All surviving children were invited to a midchildhood outcome study. Data for this study were collected from October 27, 2006, through March 18, 2011, and analyzed from June 1 through 30, 2018.

Interventions

At 6 to 8 years of corrected age, children were assessed by a pediatrician and psychologist for neurosensory and cognitive function, and parents completed standardized questionnaires.

Main Outcomes and Measures

The prespecified primary outcomes were survival free of any disability and death or survival with moderate to severe disability.

Results

Of 1059 eligible children, 988 (55.0% male; mean [SD] age at follow-up, 7.5 [1.1] years) were assessed at midchildhood. The FGR rate was 139 of 493 children (28.2%) in the repeated betamethasone treatment group and 122 of 495 (24.6%) in the placebo group (P = .20). Primary outcome rates were similar between treatment groups for the FGR and non-FGR subgroups, with no evidence of an interaction effect for survival free of any disability (FGR group, 108 of 144 [75.0%] for repeated betamethasone treatment vs 91 of 126 [72.2%] for placebo groups [odds ratio [OR], 1.1; 95% CI, 0.6-1.9]; non-FGR group, 267 of 335 [79.7%] for repeated betamethasone vs 283 of 358 [79.0%] for placebo groups [OR, 1.0; 95% CI, 0.7-1.5]; P = .77) and death or moderate to severe disability (FGR group, 21 of 144 [14.6%] for repeated betamethasone treatment vs 20 of 126 [15.9%] for placebo groups [OR, 0.9; 95% CI, 0.4-1.9]; non-FGR group, 29 of 335 [8.6%] for repeated betamethasone vs 36 of 358 [10.0%] for placebo [OR, 0.8; 95% CI, 0.4-1.3]; P = .84).

Conclusions and Relevance

In this study, repeated antenatal betamethasone treatment compared with placebo was not associated with adverse effects on neurocognitive function at 6 to 8 years of age, even in the presence of FGR. Physicians should use repeated doses of antenatal corticosteroids when indicated before preterm birth, regardless of FGR, in view of the associated neonatal benefits and absence of later adverse effects.

Trial Registration

anzctr.org.au Identifier: ACTRN12606000318583.

Prenatal Stress, Glucocorticoids, and Developmental Programming of the Stress Response

The early environment has a major impact on the developing embryo, fetus, and infant. Parental adversity (maternal and paternal) and glucocorticoid exposure before conception and during pregnancy have profound effects on the development and subsequent function of the hypothalamic-pituitary-adrenal axis and related behaviors. These effects are species-, sex-, and age-specific and depend on the timing and duration of exposure. The impact of these early exposures can extend across multiple generations, via both the maternal and paternal lineage, and recent studies have begun to determine the mechanisms by which this occurs. Improved knowledge of the mechanisms by which adversity and glucocorticoids program stress systems will allow development of strategies to ameliorate and/or reverse these long-term effects.

Neuroactive steroids and stress axis regulation: Pregnancy and beyond

The hypothalamo-pituitary-adrenal (HPA) axis plays a critical role in regulating responses to stress and long term dysregulation of the HPA axis is associated with higher rates of mood disorders. There are circumstances where the HPA axis is more or less responsive to stress. For example, during late pregnancy ACTH and corticosterone responses to stress are markedly suppressed, whereas in offspring born to mothers that experienced repeated stress during pregnancy, the HPA axis is hyper-responsive to stress. Neuroactive steroids such as allopregnanolone, tetrahydrodeoxycorticosterone (THDOC) and androstanediol can modulate HPA axis activity and concentrations of some neuroactive steroids in the brain are altered during pregnancy and following stress. Thus, here altered neurosteroidogenesis is proposed as a mechanism that could underpin the dynamic changes in HPA axis regulation typically observed in late pregnant and in prenatally stressed individuals. In support of this hypothesis, evidence in rats demonstrates that elevated levels of allopregnanolone in pregnancy induce a central inhibitory opioid mechanism that serves to minimize stress-induced HPA axis activity. Conversely, in prenatally stressed rodents, where HPA axis stress responses are enhanced, evidence indicates the capacity of the brain for neurosteroidogenesis is reduced. Understanding the mechanisms involved in adaptations in HPA axis regulation may provide insights for manipulating stress sensitivity and for developing therapies for stress-related disorders in humans.

Percutaneous Fetal Cardiac Catheterization Technique for Stenting the Foramen Ovale in a Midgestation Lamb Model

Background—

Intact or highly restricted intra-atrial septum can be reliably diagnosed in the human fetus as early as 22 to 24 weeks of gestation. Fetal interventions targeting the atrial septum have used a direct approach through the atrial wall. Here, we report stenting of the foramen ovale with a large, open-cell stent via percutaneous access through the fetal hepatic vein in a sheep model.

Methods and Results—

In 5 fetal sheep of 109 to 111 days of gestation (term, 147 days), the fetal hepatic vein was punctured percutaneously under ultrasound guidance and a 13.3-cm 14-gauge intravenous catheter was inserted. After catheterization of the inferior vena cava, right atrium, foramen ovale, and left atrium with a guidewire and 1.8F to 2.6F tapered catheter, a self-expandable, 8×12-mm flexible open-cell stent was positioned in an unrestricted foramen ovale. Flow and fetal well-being were documented for 45 minutes after the procedure. Access to the left atrium was achieved in all 5 animals and all survived. In 4 animals, the stent was successfully positioned in the foramen ovale. One fetus was born at term and euthanized on day 3: postmortem examination confirmed the patency of the stent. The other 3 fetuses were well after being monitored by ultrasound for 45 minutes. In 1 animal, the stent dislodged immediately after release obstructing the mitral valve. This fetus developed ascites and was euthanized after 4 days.

Conclusions—

It is feasible to safely advance a large diameter, self-expandable, open-cell design stent into the fetal atrial septum via a percutaneous access route through the fetal hepatic vein.

Genomics of preterm birth

The molecular mechanisms controlling human birth timing at term, or resulting in preterm birth, have been the focus of considerable investigation, but limited insights have been gained over the past 50 years. In part, these processes have remained elusive because of divergence in reproductive strategies and physiology shown by model organisms, making extrapolation to humans uncertain. Here, we summarize the evolution of progesterone signaling and variation in pregnancy maintenance and termination. We use this comparative physiology to support the hypothesis that selective pressure on genomic loci involved in the timing of parturition have shaped human birth timing, and that these loci can be identified with comparative genomic strategies. Previous limitations imposed by divergence of mechanisms provide an important new opportunity to elucidate fundamental pathways of parturition control through increasing availability of sequenced genomes and associated reproductive physiology characteristics across diverse organisms.

The effects of dexamethasone on post-asphyxial cerebral oxygenation in the preterm fetal sheep

Exposure to clinical doses of the glucocorticoid dexamethasone increases brain activity and causes seizures in normoxic preterm fetal sheep without causing brain injury. In contrast, the same treatment after asphyxia increased brain injury. We hypothesised that increased injury was in part mediated by a mismatch between oxygen demand and oxygen supply. In preterm fetal sheep at 0.7 gestation we measured cerebral oxygenation using near-infrared spectroscopy, electroencephalographic (EEG) activity, and carotid blood flow (CaBF) from 24 h before until 72 h after asphyxia induced by 25 min of umbilical cord occlusion. Ewes received dexamethasone intramuscularly (12 mg 3 ml(-1)) or saline 15 min after the end of asphyxia. Fetuses were studied for 3 days after occlusion. During the first 6 h of recovery after asphyxia, dexamethasone treatment was associated with a significantly greater fall in CaBF (P < 0.05), increased carotid vascular resistance (P < 0.001) and a greater fall in cerebral oxygenation as measured by the difference between oxygenated and deoxygenated haemoglobin (delta haemoglobin; P < 0.05). EEG activity was similarly suppressed in both groups. From 6 to 10 h onward, dexamethasone treatment was associated with a return of CaBF to saline control levels, increased EEG power (P < 0.005), greater epileptiform transient activity (P < 0.001), increased oxidised cytochrome oxidase (P < 0.05) and an attenuated increase in [delta haemoglobin] (P < 0.05). In conclusion, dexamethasone treatment after asphyxia is associated with greater hypoperfusion in the critical latent phase, leading to impaired intracerebral oxygenation that may exacerbate neural injury after asphyxia.