Upregulation of hepatic nuclear receptors in extremely preterm ovine fetuses undergoing artificial placenta therapy

OBJECTIVE

Extremely preterm infants have low Nuclear Receptor (NR) expression in their developing hepatobiliary systems, as they rely on the placenta and maternal liver for compensation. NRs play a crucial role in detoxification and the elimination of both endogenous and xenobiotic substances by regulating key genes encoding specific proteins. In this study, we utilized an Artificial Placenta Therapy (APT) platform to examine the liver tissue expression of NRs of extremely preterm ovine fetuses. This fetal model, resembling a "knockout placenta," lacks placental and maternal support, while maintaining a healthy extrauterine survival.

METHODS

Six ovine fetuses at 95 ± 1 d gestational age (GA; term = ∼150 d)/∼600 g delivery weight were maintained on an APT platform for a period of 120 h (APT Group). Six age-matched, in utero control fetuses were delivered at 99-100 d GA (Control Group). Fetal liver tissue samples and blood samples were collected at delivery from both groups and assessed mRNA expression of NRs and target transporters involved in the hepatobiliary transport system using quantitative PCR. Data were tested for group differences with ANOVA (p < .05 deemed significant).

RESULTS

mRNA expression of NRs was identified in both the placenta and the extremely preterm ovine fetal liver. The expression of HNF4α, LRH1, LXR, ESR1, PXR, CAR, and PPARα/γ were significantly elevated in the liver of the APT Group compared to the Control Group. Moreover, target transporters NTCP, OATP1B3, BSEP, and MRP4 were upregulated, whereas MRP2 and MRP3 were unchanged. Although there was no evidence of liver necrosis or apoptotic changes histologically, there was an impact in the fetal liver of the ATP group at the tissue level with a significant increase in TNFα mRNA, a cytokine involved in liver inflammation, and blood elevation of transaminases.

CONCLUSION

A number of NRs in the fetal liver were significantly upregulated after loss of placental-maternal support. However, the expression of target transporter genes appeared to be insufficient to compensate role of the placenta and maternal liver and avoid fetal liver damage, potentially due to insufficient excretion of organic anions.

Simulated lunar microgravity transiently arrests growth and induces osteocyte-chondrocyte lineage differentiation in human Wharton's jelly stem cells

Human Wharton's jelly stem cells (hWJSCs) are multipotent stem cells that are extensively employed in biotechnology applications. However, the impact of simulated lunar microgravity (sμG) on the growth, differentiation, and viability of this cell population is incompletely characterized. We aimed to determine whether acute (72 h) exposure to sμG elicited changes in growth and lineage differentiation in hWJSCs and if putative changes were maintained once exposure to terrestrial gravity (1.0 G) was restored. hWJSCs were cultured under standard 1.0 G conditions prior to being passaged and cultured under sμG (0.16 G) using a random positioning machine. Relative to control, hWJSCs cultured under sμG exhibited marked reductions in growth but not viability. Cell population expression of characteristic stemness markers (CD 73, 90, 105) was significantly reduced under sμG conditions. hWJSCs had 308 significantly upregulated and 328 significantly downregulated genes when compared to 1.0 G culture conditions. Key markers of cell replication, including MKI67, were inhibited. Significant upregulation of osteocyte-chondrocyte lineage markers, including SERPINI1, MSX2, TFPI2, BMP6, COMP, TMEM119, LUM, HGF, CHI3L1 and SPP1, and downregulation of cell fate regulators, including DNMT1 and EZH2, were detected in sμG-exposed hWJSCs. When returned to 1.0 G for 3 days, sμG-exposed hWJSCs had accelerated growth, and expression of stemness markers increased, approaching normal (i.e. 95%) levels. Our data support earlier findings that acute sμG significantly reduces the cell division potential of hWJSCs and suggest that acute sμG-exposure induces reversible changes in cell growth accompanied by osteocyte-chondrocyte changes in lineage differentiation.

Respiratory benefit in preterm lambs is progressively lost when the concentration of fetal plasma betamethasone is titrated below two nanograms per milliliter

Antenatal steroid therapy is the standard of care for women at imminent risk of preterm delivery. Current dosing regimens use suprapharmacological doses to achieve extended fetal steroid exposures. We aimed to determine the lowest fetal plasma betamethasone concentration sufficient to achieve functional preterm lung maturation. Ewes with single fetuses underwent surgery to install a fetal jugular catheter. Adopting a stepwise design, ewes were randomized to either a saline-only group (negative control group; n = 9) or one of four betamethasone treatment groups. Each betamethasone group fetus received a fetal intravenous infusion to target a constant plasma betamethasone level of either 1) 2 ng/mL (2 ng/mL positive control group, n = 9); 2) 1 ng/mL, (1 ng/mL group, n = 10); 3) 0.5 ng/mL (0.5 ng/mL group, n = 10); or 4) 0.25 ng/mL (0.25 ng/mL group, n = 10). Fetuses were infused for 48 h, delivered, and ventilated. The positive control group, negative control group, and mid-point 0.5 ng/mL group animals were tested first. An interim analysis informed the final betamethasone group tested. Positive control group animals had large, statistically significant improvements in respiratory function. Based on an interim analysis, the 1.0 ng/mL group was studied in favor of the 0.25 ng/mL group. Treatment efficacy was progressively lost at plasma betamethasone concentrations lower than 2 ng/mL. We demonstrated that the acute respiratory benefit conveyed by antenatal steroid exposure in the fetal sheep is progressively lost when constant fetal plasma betamethasone concentrations are reduced below a targeted value of 2 ng/mL.NEW & NOTEWORTHY Lung maturation benefits in preterm lambs were progressively lost when fetal plasma betamethasone concentrations fell below 2 ng/mL. The effective floor threshold for a robust, lung-maturing exposure likely lies between 1 and 2 ng betamethasone per milliliter of plasma. Hypothalamic pituitary adrenal axis signaling and immunocyte populations remained materially disrupted at subtherapeutic steroid concentrations. These data demonstrate the potential to improve antenatal steroid therapy using reduced dose regimens informed by glucocorticoid pharmacokinetics and pharmacodynamics.

Pharmacological blockade of the interleukin-1 receptor suppressed Escherichia coli lipopolysaccharide-induced neuroinflammation in preterm fetal sheep

BACKGROUND

Intraamniotic inflammation is associated with preterm birth, especially in cases occurring before 32 weeks' gestation, and is causally linked with an increased risk for neonatal mortality and morbidity. Targeted anti-inflammatory interventions may assist in improving the outcomes for pregnancies impacted by intrauterine inflammation. Interleukin-1 is a central upstream mediator of inflammation. Accordingly, interleukin-1 is a promising candidate target for intervention therapies and has been targeted previously using the interleukin-1 receptor antagonist, anakinra. Recent studies have shown that the novel, noncompetitive, allosteric interleukin-1 receptor inhibitor, rytvela, partially resolved inflammation associated with preterm birth and fetal injury. In this study, we used a preterm sheep model of chorioamnionitis to investigate the anti-inflammatory efficacy of rytvela and anakinra, administered in the amniotic fluid in the setting of intraamniotic Escherichia coli lipopolysaccharide exposure.

OBJECTIVE

We hypothesized that both rytvela and anakinra would reduce lipopolysaccharide-induced intrauterine inflammation and protect the fetal brain.

STUDY DESIGN

Ewes with a singleton fetus at 105 days of gestation (term is ∼150 days) were randomized to one of the following groups: (1) intraamniotic injections of 2 mL saline at time=0 and time=24 hours as a negative control group (saline group, n=12); (2) intraamniotic injection of 10 mg Escherichia coli lipopolysaccharide in 2 mL saline and intraamniotic injections of 2 mL saline at time=0 hours and time=24 hours as an inflammation positive control group (lipopolysaccharide group, n=11); (3) intraamniotic injection of Escherichia coli lipopolysaccharide in 2 mL saline and intraamniotic injections of 2.5 mg rytvela at time=0 hours and time=24 hours to test the anti-inflammatory efficacy of rytvela (lipopolysaccharide + rytvela group, n=10); or (4) intraamniotic injection of Escherichia coli lipopolysaccharide in 2 mL saline and intraamniotic injections of 100 mg anakinra at time=0 hours and time=24 hours to test the anti-inflammatory efficacy of anakinra (lipopolysaccharide + anakinra group, n=12). Amniotic fluid was sampled at time 0, 24, and 48 hours (ie, at each intervention and at delivery). Fetal umbilical cord blood was collected at delivery for differential blood counts and chemical studies. Inflammation was characterized by the analysis of fetal tissue cytokine and chemokine levels using quantitative polymerase chain reaction, enzyme-linked inmmunosorbent assay, and histology. The primary study outcome of interest was the assessment of anakinra and rytvela brain-protective effects in the setting of Escherichia coli lipopolysaccharide-induced intrauterine inflammation. Secondary outcomes of interest were to assess protection from fetal and intrauterine (ie, amniotic fluid, chorioamnion) inflammation.

RESULTS

Intraamniotic administration of lipopolysaccharide caused inflammation of the fetal lung, brain, and chorioamnionitis in preterm fetal sheep. Relative to treatment with saline only in the setting of lipopolysaccharide exposure, intraamniotic administration of both rytvela and anakinra both significantly prevented periventricular white matter injury, microglial activation, and histologic chorioamnionitis. Anakinra showed additional efficacy in inhibiting fetal lung myeloperoxidase activity, but its use was associated with metabolic acidaemia and reduced fetal plasma insulin-like growth factor-1 levels at delivery.

CONCLUSION

Intraamniotic administration of rytvela or anakinra significantly inhibited fetal brain inflammation and chorioamnionitis in preterm fetal sheep exposed to intraamniotic lipopolysaccharide. In addition, anakinra treatment was associated with potential negative impacts on the developing fetus.

A Reduction in Antenatal Steroid Dose Was Associated with Reduced Cardiac Dysfunction in a Sheep Model of Pregnancy

Despite widespread use, dosing regimens for antenatal corticosteroid (ACS) therapy are poorly unoptimized. ACS therapy exerts a programming effect on fetal development, which may be associated with an increased risk of cardiovascular disease. Having demonstrated that low-dose steroid therapy is an efficacious means of maturing the preterm lung, we hypothesized that a low-dose steroid exposure would exert fewer adverse functional and transcriptional changes on the fetal heart. We tested this hypothesis using low-dose steroid therapy (10 mg delivered to the ewe over 36 h via constant infusion) and compared cardiac effects with those of a higher dose treatment (30 mg delivered to the ewe over 24 h by intramuscular injection; simulating currently employed clinical ACS regimens). Fetal cardiac function was assessed by ultrasound on the day of ACS treatment initiation. Transcriptomic analyses were performed on fetal myocardial tissue. Relative to saline control, fetuses in the higher-dose clinical treatment group had significantly lower ratios between early diastolic ventricular filling and ventricular filling during atrial systole, and showed the differential expression of myocardial hypertrophy-associated transcripts including βMHC, GADD45γ, and PPARγ. The long-term implications of these changes remain unstudied. Irrespective, optimizing ACS dosing regimens to maximize respiratory benefit while minimizing adverse effects on key organ systems, such as the heart, offers a means of improving the acute and long-term outcomes associated with this important obstetric therapy.

Artificial placenta support of extremely preterm ovine fetuses at the border of viability for up to 336 hours with maintenance of systemic circulation but reduced somatic and organ growth

Introduction: Artificial placenta therapy (APT) is an experimental life support system to improve outcomes for extremely preterm infants (EPI) less than 1,000 g by obviating the need for pulmonary gas exchange. There are presently no long-term survival data for EPI supported with APT. To address this, we aimed to maintain 95d-GA (GA; term-150d) sheep fetuses for up to 2 weeks using our APT system. Methods: Pregnant ewes (n = 6) carrying singleton fetuses underwent surgical delivery at 95d GA. Fetuses were adapted to APT and maintained for up to 2 weeks with constant monitoring of key physiological parameters and extensive time-course blood and urine sampling, and ultrasound assessments. Six age-matched in-utero fetuses served as controls. Data were tested for group differences with ANOVA. Results: Six APT Group fetuses (100%) were adapted to APT successfully. The mean BW at the initiation of APT was 656 ± 42 g. Mean survival was 250 ± 72 h (Max 336 h) with systemic circulation and key physiological parameters maintained mostly within normal ranges. APT fetuses had active movements and urine output constantly exceeded infusion volume over the experiment. At delivery, there were no differences in BW (with edema in three APT group animals), brain weight, or femur length between APT and in-utero Control animals. Organ weights and humerus lengths were significantly reduced in the APT group (p < 0.05). Albumin, IGF-1, and phosphorus were significantly decreased in the APT group (p < 0.05). No cases of positive blood culture were detected. Conclusion: We report the longest use of APT to maintain extremely preterm fetuses to date. Fetal systemic circulation was maintained without infection, but growth was abnormal. This achievement suggests a need to focus not only on cardiovascular stability and health but also on the optimization of fetal growth and organ development. This new challenge will need to be overcome prior to the clinical translation of this technology.

Antenatal steroids: benefits, risks, and new insights

Being born before 37 weeks' gestation, or preterm birth, is a leading cause of early childhood death and life-long disability. Antenatal steroids (ANS) are recommended for women judged at risk of imminent preterm delivery. The primary intent of ANS treatment is to rapidly mature the fetal lungs to reduce the risk of mortality and lasting morbidity. Despite being used clinically for some 50 years, a large number of uncertainties remain surrounding the use of ANS. In particular, the choice of agent, dose/regimen, and appropriate gestational age range for ANS therapy all remain unclear. Unresolved concerns regarding the potential risk of harms from ANS treatment, especially in light of the modest benefits seen with expanding latepreterm administration, make it increasingly important to optimize the dosing and application of this important and widely used treatment. This review will serve to summarize past data, provide an update on recent developments, and chart a way forward to maximize the overall benefit of this important therapy.

ChatGPT Outscored Human Candidates in a Virtual Objective Structured Clinical Examination (OSCE) in Obstetrics and Gynecology

BACKGROUND

Natural language processing is a form of artificial intelligence that allows human users to interface with a machine without using complex code. The ability of natural language processing systems such as ChatGPT to successfully engage with healthcare systems requiring fluid reasoning, specialist data interpretation, and empathetic communication in an unfamiliar and evolving environment is poorly studied. We tested whether the ChatGPT interface could engage with and complete a mock Objective Structured Clinical Examination simulating assessment for Membership of the Royal College of Obstetricians and Gynaecologists.

OBJECTIVES

We hypothesized that, without additional training, ChatGPT would achieve a score at least equivalent to that achieved by human candidates who sat for a virtual Objective Structured Clinical Examinations in Singapore.

STUDY DESIGN

The study was conducted in two phases. In the first, a total of seven structured discussion questions were selected from two historical cohorts (Cohorts A and B) of objective structured clinical examination questions. ChatGPT was examined using these questions and responses recorded in a script. Two human candidates (acting as anonymizers) were then examined on the same questions using videoconferencing, and their responses were transcribed verbatim into written scripts. The three sets of response scripts were then mixed, and each set allocated to one of three human actors. In the second stage, actors were used to present these scripts to examiners in response to the same examination questions. These responses were blind-scored by fourteen qualified examiners. ChatGPT scores were then unblinded and compared to historical human candidate performances.

RESULTS

The average ChatGPT score given to ChatGPT by 14 examiners was 77.2 %. The average historical human score (n=26 candidates) was 73.7 %. ChatGPT demonstrated sizable performance improvements over the average human candidate in several subject domains. The median time taken for ChatGPT to complete each station was 2.54 minutes, well before the ten-minutes allowed.

CONCLUSIONS

ChatGPT generated factually accsturate and contextually relevant structured discussion answers to complex and evolving clinical questions based on unfamiliar settings within a very short period. ChatGPT outperformed human candidates in several knowledge areas. Not all examiners were able to discern between human and ChatGPT responses. Our data highlight the emergent ability of natural language processing models to demonstrate fluid reasoning in unfamiliar environments and successfully compete with human candidates that have undergone extensive specialist training.

LPCAT1 levels in the placenta, the maternal plasma and the fetal plasma do not predict fetal lung responses to glucocorticoids in a sheep model of pregnancy

INTRODUCTION

Lysophosphatidylcholine acyltransferase 1 (LPCAT1) is important for saturated phosphatidylcholine (Sat-PC) production in the lung. Sat-PC is a critical component of pulmonary surfactant, which maintains low alveolar surface tension, facilitating respiration. Previous studies have reported an association between maternal and fetal LPCAT1 levels and neonatal lung function. Using a sheep model of pregnancy, we investigated a potential correlation between glucocorticoid-induced lung maturation and LPCAT1 mRNA and/or protein levels in the fetal lung, the placenta, the fetal plasma, and the maternal plasma.

METHODS

Eighty seven single pregnant ewes received maternal intramuscular injections of betamethasone. A sub-group of five animals had both maternal and fetal catheters installed to allow for sequential sampling from both plasma compartments. Lambs were surgically delivered under terminal anaesthesia between 2 and 8 days after initial ANS treatment, at a gestational age of 121-123 days. Lambs were ventilated for 30 min to determine functional lung maturation before being euthanized for necropsy and sample collection. Fetal lung, placenta, and fetal and maternal plasma samples were used to analyse LPCAT1 gene expression and protein levels.

RESULTS

The expression of LPCAT1 mRNA in the fetal lung was significantly corelated to Sat-PC levels at 8 days (R² = 0.23, p < 0.001) and lung maturation status overall (gas exchange efficiency as determined by measurements of lamb PaCO₂ during ventilation, R² = 0.20, p < 0.001). Similarly, fetal lung LPCAT1 mRNA was also significantly correlated with the individual durability of ANS effects on fetal lung maturation (R² = 0.20, p < 0.001). Although ANS therapy altered LPCAT1 mRNA expression in the placenta, observed changes were independent of fetal lung maturation outcomes. Neither maternal nor fetal plasma LPCAT1 levels were changed by ANS therapy over the period, including in analysis of serial maternal and fetal samples from chronically catheterised animals.

DISCUSSION

LPCAT1 expression in the fetal lung was associated with the durability of glucocorticoid effects on fetal lung maturation. However, LPCAT1 expression in the placenta, the fetal plasma, and the maternal plasma was neither associated with, nor predictive of fetal lung maturation after glucocorticoid treatment in a sheep model of pregnancy.

Low-dose antenatal betamethasone treatment achieves preterm lung maturation equivalent to that of the World Health Organization dexamethasone regimen but with reduced endocrine disruption in a sheep model of pregnancy

BACKGROUND

The intramuscular administration of antenatal steroids to women at risk of preterm delivery achieves high maternal and fetal plasma steroid concentrations, which are associated with adverse effects and may reduce treatment efficacy. We have demonstrated that antenatal steroid efficacy is independent of peak maternofetal steroid levels once exposure is maintained above a low threshold.

OBJECTIVE

This study aimed to test, using a sheep model of pregnancy, whether the low-dose antenatal steroid regimen proposed as part of the Antenatal Corticosteroids for Improving Outcomes in Preterm Newborns trial would achieve preterm lung maturation equivalent to that of the existing World Health Organization dexamethasone treatment regimen, but with reduced risk of adverse outcomes.

STUDY DESIGN

Following ethical review and approval, date-mated ewes with single fetuses received intramuscular injections of either (1) four 6-mg maternal intramuscular injections of dexamethasone phosphate every 12 hours (n=22), (2) 4 2-mg maternal intramuscular injections of betamethasone phosphate every 12 hours (n=21), or (3) 4 2-mL maternal intramuscular injections of saline every 12 hours (n=16). Of note, 48 hours after first injection, (124±1 day), lambs were delivered, ventilated for 30 minutes, and euthanized for sampling. Arterial blood gas, respiratory, hematological, and biochemical data were analyzed for between-group differences with analysis of variance according to distribution and variance, with P<.05 taken as significant.

RESULTS

After 30 minutes of ventilation, lambs from both steroid-treated groups had significant and equivalent improvements in lung function relative to saline control (P<.05). There was no significant difference in arterial blood pH, pO₂, pCO₂, lung compliance, ventilator efficiency index, or lung volume at necropsy with a static pressure of 40 cmH₂O. The messenger RNA expression of surfactant protein (Sp)a, Spb, Spc, Spd, aquaporin (Aqp)1, Aqp5, and sodium channel epithelial 1 subunit beta (Scnn1b) was equivalent between both steroid groups. Maternal and fetal plasma neutrophil, glucose, and fetal plasma C-peptide levels were significantly elevated in the dexamethasone group, relative to the betamethasone group. Fetal plasma insulin-like growth factor 1 was significantly reduced in the dexamethasone group compared with the betamethasone group (P<0.05). Fetal adrenocorticotropic hormone (r=0.53), maternal glucose value (r=-0.52), and fetal glucose values (r=-0.42) were correlated with maternal weight in the betamethasone group (P<.05), whereas fetal pCO₂ and pO₂ were not correlated. There was no significant difference between male and female lamb outcomes in any groups for any of the items evaluated.

CONCLUSION

This study reported that in preterm lambs, a low-dose treatment regimen of 8 mg betamethasone achieves lung maturation equivalent to that of a 24-mg dexamethasone-based regimen, but with smaller perturbations to the maternofetal hypothalamic-pituitary-adrenal axis. These data suggested that given steroid pharmacokinetic differences between sheep and humans, a betamethasone dose of 2 mg may remain above the minimum dose necessary for robust maturation of the preterm lung. Maternal weight-adjusted betamethasone doses might also be a key to reducing perturbations to the maternofetal hypothalamic-pituitary-adrenal axis.

The complex challenge of antenatal steroid therapy nonresponsiveness

Antenatal steroid therapy is standard care for women at imminent risk of preterm delivery. When deliveries occur within 7 days of treatment, antenatal steroid therapy reduces the risk of neonatal death and improves preterm outcomes by exerting diverse developmental effects on the fetal organs, in particular the preterm lung and cardiovascular system. There is, however, sizable variability in antenatal steroid treatment efficacy, and an important percentage of fetuses exposed to antenatal steroid therapy do not respond sufficiently to derive benefit. Respiratory distress syndrome, for example, is a central metric of clinical trials to assess antenatal steroid outcomes. In the present analysis, we addressed the concept of antenatal steroid nonresponsiveness, and defined a failed or suboptimal response to antenatal steroids as death or a diagnosis of respiratory distress syndrome following treatment. For deliveries at 24 to 35 weeks' gestation, the number needed to treat to prevent 1 case of respiratory distress syndrome was 19 (95% confidence interval, 14-28). Reflecting gestation-dependent risk, for deliveries at >34 weeks' gestation the number needed to treat was 55 (95% confidence interval, 30-304), whereas for elective surgical deliveries at term this number was 106 (95% confidence interval, 61-421). We reviewed data from clinical and animal studies investigating antenatal steroid therapy to highlight the significant incidence of antenatal steroid therapy nonresponsiveness (ie, residual mortality or respiratory distress syndrome after treatment), and the potential mechanisms underpinning this outcome variability. The origins of this variability may be related to both the manner in which the therapy is applied (ie, the treatment regimen itself) and factors specific to the individual (ie, genetic variation, stress, infection). The primary aims of this review were: (1) to emphasize to the obstetrical and neonatal communities the extent of antenatal steroid response variability and its potential impact; (2) to propose approaches by which antenatal steroid therapy may be better applied to improve overall benefit; and (3) to stimulate further research toward the empirical optimization of this important antenatal therapy.

Single nucleotide polymorphisms in surfactant protein A1 are not associated with a lack of responsiveness to antenatal steroid therapy in a pregnant sheep model

Treatment with antenatal steroids (ANS) is standard practice for reducing the risk of respiratory distress in the preterm infant. Despite clear overall benefits when appropriately administered, many fetuses fail to derive benefit from ANS therapies. In standardized experiments using a pregnant sheep model, we have demonstrated that around 40% of ANS-exposed lambs did not have functional lung maturation significantly different from that of saline-treated controls. Surfactant protein A is known to play an important role in lung function. In this genotyping study, we investigated the potential correlation between polymorphisms in SFTPA1, messenger RNA and protein levels, and ventilation outcomes in animals treated with ANS. 45 preterm lambs were delivered 48 h after initial ANS therapy and 44 lambs were delivered 8 days after initial ANS therapy. The lambs were ventilated for 30 min after delivery. SFTPA1 mRNA expression in lung tissue was not correlated with arterial blood PaCO2 values at 30 min of ventilation in lambs delivered 48 h after treatment. SFTPA1 protein in lung tissue was significantly correlated with PaCO2 at 30 min of ventilation in lambs ventilated both 48 h and 8 days after ANS treatment. Six different single nucleotide polymorphisms (SNPs) in the Ovis aries SFTPA1 sequence were detected by Sanger Sequencing. No individual SNPs or SNP haplotypes correlated with alterations in PaCO2 at 30 min of ventilation or SFTPA1 protein levels in the lung. For the subset of animals analyzed in the present study, variable lung maturation responses to ANS therapy were not associated with mutations in SFTPA1.

1% of the clinical dose used for antenatal steroid therapy is sufficient to induce lung maturation when administered directly to the preterm ovine fetus

INTRODUCTION

Antenatal steroids (ANS) are standard of care for women at imminent risk of preterm delivery. ANS accelerate functional maturation of the preterm fetal lung. Current dosing regimens expose the mother and fetus to high steroid levels with increased risk of adverse outcomes. Using a sheep model of pregnancy, we aimed to demonstrate that direct fetal administration would be sufficient to elicit functional maturation of the fetal lung.

STUDY DESIGN

Ewes and fetuses at 122d gestation underwent recovery surgery to install a fetal jugular catheter. Animals were then immediately randomised to either: i) fetal intravenous betamethasone phosphate infusion of 2ng/ml for 26 hours (fetal low-dose group; n=16); ii) fetal intravenous saline infusion for 26 hours and two maternal intramuscular injections of 0.25mg/kg betamethasone-phosphate + betamethasone-acetate (maternal clinical treatment group; n=12); or iii) fetal intravenous saline infusion for 26 hours (negative control group; n=10). Fetuses were delivered 48 hours after surgery, ventilated for 30 min to allow collection of physiological data, and euthanised.

RESULTS

The average betamethasone dose for the fetal low-dose group was 1% (0.3mg) of that used in the maternal clinical treatment group (30mg). At 30 minutes of ventilation, arterial paCO2, pH, heart rate and VEI were significantly (p<0.05) and equivalently improved in both the fetal low-dose and maternal clinical treatment group relative to negative control.

CONCLUSION

Maternal steroid administration was not required to elicit fetal lung maturation. Targeted fetal ANS treatments may allow the use of materially reduced antenatal steroid exposures, significantly reducing the risk of adverse outcomes.

Continuous but not pulsed low-dose fetal betamethasone exposures extend the durability of antenatal steroid therapy

Antenatal steroid (ANS) therapy is standard care for women at imminent risk of preterm labor. Despite extensive and long-standing use, 40-50% of babies exposed antenatally to steroids do not derive benefit; remaining undelivered 7d or more after ANS treatment is associated with a lack of treatment benefit, and increased risk of harms. We used a pregnant sheep model to evaluate the impact of continuous vs. pulsed ANS treatments on fetal lung maturation at an extended, eight-day treatment to delivery interval. Continuous low-dose ANS treatments for more than 72 hours in duration improved fetal lung maturation at eight days after treatment initiation. If fetal ANS exposure was interrupted, the beneficial ANS effect was lost. Truncated treatments, including that simulating the current clinical treatment regimen, did not improve lung function. Variable fetal lung maturation was correlated to the amount of saturated phosphatidylcholine present in the lung fluid. These data demonstrate that: i) the durability of ANS therapy may be enhanced by employing an extended, low-dose treatment regimen with reducing total dose; and ii) interrupting the continuity of fetal exposure by allowing it to fall below a minimal threshold was associated with comparably poor functional maturation of the preterm ovine lung.

Perinatal care for the extremely preterm infant

Being born preterm (prior to 37 weeks of completed gestation) is a leading cause of childhood death up to five years of age, and is responsible for the demise of around one million preterm infants each year. Rates of prematurity, which range from approximately 5 to 18% of births, are increasing in most countries. Babies born extremely preterm (less than 28 weeks' gestation) and in particular, in the periviable (20^0/7-25^6/7 weeks) period, are at the highest risk of death, or the development of long-term disabilities. The perinatal care of extremely preterm infants and their mothers raises a number of clinical, technical, and ethical challenges. Focusing on 'micropremmies', or those born in the periviable period, this paper provides an update regarding the aetiology and impacts of periviable preterm birth, advances in the antenatal, intrapartum, and acute post-natal management of these infants, and a review of counselling/support approaches for engaging with the infant's family. It concludes with an overview of emerging technology that may assist in improving outcomes for this at-risk population.

Betamethasone phosphate reduces the efficacy of antenatal steroid therapy and is associated with lower birthweights when administered to pregnant sheep in combination with betamethasone acetate

BACKGROUND

Antenatal corticosteroid therapy is a standard of care for women at imminent risk of preterm labor. However, the optimal (maximum benefit and minimal risk of side effects) antenatal corticosteroid dosing strategy remains unclear. Although conveying overall benefit when given to the right patient at the right time, antenatal corticosteroid treatment efficacy is highly variable and is not risk-free. Building on earlier findings, we hypothesized that when administered in combination with slow-release betamethasone acetate, betamethasone phosphate and the high maternal-fetal betamethasone concentrations it generates are redundant for fetal lung maturation.

OBJECTIVE

Using an established sheep model of prematurity and postnatal ventilation of the preterm lamb, we aimed to compare the pharmacodynamic effects of low-dosage treatment with betamethasone acetate only against a standard dosage of betamethasone phosphate and betamethasone acetate as recommended by the American College of Obstetricians and Gynecologists for women at risk of imminent preterm delivery between 24 0/7 and 35 6/7 weeks' gestation.

STUDY DESIGN

Ewes carrying a single fetus at 122±1 days' gestation (term=150 days) were randomized to receive either (1) maternal intramuscular injections of sterile saline (the saline negative control group, n=12), (2) 2 maternal intramuscular injections of 0.25 mg/kg betamethasone phosphate+betamethasone acetate administered at 24-hour dosing intervals (the betamethasone phosphate+betamethasone acetate group, n=12); or (3) 2 maternal intramuscular injections of 0.125 mg/kg betamethasone acetate administered at 24-hour dosing intervals (the betamethasone acetate group, n=11). The fetuses were surgically delivered 48 hours after treatment initiation and ventilated for 30 minutes to determine functional lung maturation. The fetuses were euthanized after ventilation, and the lungs were collected for analysis using quantitative polymerase chain reaction and Western blot assays. Fetal plasma adrenocorticotropic hormone levels were measured in the cord blood samples taken at delivery.

RESULTS

Preterm lambs were defined as either antenatal corticosteroid treatment responders or nonresponders using an arbitrary cutoff, being a PaCO₂ level at 30 minutes of ventilation being more extreme than 2 standard deviations from the mean value of the normally distributed saline control group values. Compared with the animals in the saline control group, the animals in the antenatal corticosteroid treatment groups showed significantly improved lung physiological responses (blood gas and ventilation data) and had a biochemical signature (messenger RNA and surfactant protein assays) consistent with functional maturation. However, the betamethasone acetate group had a significantly higher treatment response rate than the betamethasone phosphate+betamethasone acetate group. These physiological results were strongly correlated to the amount of surfactant protein A. Birthweight was lower in the betamethasone phosphate+betamethasone acetate group and the fetal hypothalamic-pituitary-adrenal axis was suppressed to a greater extent in the betamethasone phosphate+betamethasone acetate group.

CONCLUSION

Low-dosage antenatal corticosteroid therapy solely employing betamethasone acetate was sufficient for fetal lung maturation. The elevated maternal-fetal betamethasone concentrations associated with the coadministration of betamethasone phosphate did not in addition improve lung maturation but were associated with greater fetal hypothalamic-pituitary-adrenal axis suppression, a lower antenatal corticosteroid treatment response rate, and lower birthweight-outcomes not desirable in a clinical setting. These data warranted a clinical investigation of sustained low-dosage antenatal corticosteroid treatments that avoid high maternal-fetal betamethasone exposures.

Direct administration of the non-competitive interleukin-1 receptor antagonist rytvela transiently reduced intrauterine inflammation in an extremely preterm sheep model of chorioamnionitis

Background

Intraamniotic inflammation is associated with up to 40% of preterm births, most notably in deliveries occurring prior to 32 weeks’ gestation. Despite this, there are few treatment options allowing the prevention of preterm birth and associated fetal injury. Recent studies have shown that the small, non-competitive allosteric interleukin (IL)-1 receptor inhibitor, rytvela, may be of use in resolving inflammation associated with preterm birth (PTB) and fetal injury. We aimed to use an extremely preterm sheep model of chorioamnionitis to investigate the anti-inflammatory efficacy of rytvela in response to established intra-amniotic (IA) lipopolysaccharide (LPS) exposure. We hypothesized that rytvela would reduce LPS-induced IA inflammation in amniotic fluid (AF) and fetal tissues.

Methods

Sheep with a single fetus at 95 days gestation (estimated fetal weight 1.0 kg) had surgery to place fetal jugular and IA catheters. Animals were recovered for 48 hours before being randomized to either: i) IA administration of 2 ml saline 24 hours before 2 ml IA and 2 ml fetal intravenous (IV) administration of saline (Saline Group, n = 7); ii) IA administration of 10 mg LPS in 2 ml saline 24 hours before 2 ml IA and 2 ml fetal IV saline (LPS Group, n = 10); 3) IA administration of 10 mg LPS in 2 ml saline 24 hours before 0.3 mg/fetal kg IA and 1 mg/fetal kg fetal IV rytvela in 2 ml saline, respectively (LPS + rytvela Group, n = 7). Serial AF samples were collected for 120 h. Inflammatory responses were characterized by quantitative polymerase chain reaction (qPCR), histology, fluorescent immunohistochemistry, enzyme-linked inmmunosorbent assay (ELISA), fluorescent western blotting and blood chemistry analysis.

Results

LPS-treated animals had endotoxin and AF monocyte chemoattractant protein (MCP)-1 concentrations that were significantly higher at 24 hours (immediately prior to rytvela administration) relative to values from Saline Group animals. Following rytvela administration, the average MCP-1 concentrations in the AF were significantly lower in the LPS + rytvela Group relative to in the LPS Group. In delivery samples, the expression of IL-1β in fetal skin was significantly lower in the LPS + rytvela Group compared to the LPS Group.

Conclusion

A single dose of rytvela was associated with partial, modest inhibition in the expression of a panel of cytokines/chemokines in fetal tissues undergoing an active inflammatory response.

The duration of fetal antenatal steroid exposure determines the durability of preterm ovine lung maturation

BACKGROUND

Antenatal corticosteroids (ACS) are the standard of care for maturing the fetal lung and improving outcomes for preterm infants. Antenatal corticosteroid dosing remains nonoptimized, and there is little understanding of how different treatment-to-delivery intervals may affect treatment efficacy. The durability of a lung maturational response is important because the majority of women treated with antenatal corticosteroids do not deliver within the widely accepted 1- to 7-day window of treatment efficacy.

OBJECTIVE

We used a sheep model to test the duration of fetal exposures for efficacy at delivery intervals from 1 to 10 days.

MATERIALS AND METHODS

For infusion studies, ewes with single fetuses were randomized to receive an intravenous bolus and maintenance infusion of betamethasone phosphate to target 1-4 ng/mL fetal plasma betamethasone for 36 hours, with delivery at 2, 4 ,or 7 days posttreatment or sterile saline solution as control. Animals receiving the clinical treatment were randomised to receive either a single injection of 0.25 mg/kg with a 1:1 mixture of betamethasone phosphate + betamethasone acetate with delivery at either 1 or 7 days posttreatment, or 2 treatments of 0.25 mg/kg betamethasone phosphate + betamethasone acetate spaced at 24 hours (giving ∼48 hours of fetal steroid exposure) with delivery at 2, 5, 7, or 10 days posttreatment. Negative control animals were treated with saline solution. All lambs were delivered at 121 ± 3 days gestational age and ventilated for 30 minutes to assess lung function.

RESULTS

Preterm lambs delivered at 1 or 2 days post-antenatal corticosteroid treatment had significant improvements in lung maturation for both intravenous and single-dose intramuscular treatments. After 2 days, the efficacy of 36-hour betamethasone phosphate infusions was lost. The single dose of 1:1 betamethasone phosphate + betamethasone acetate also was ineffective at 7 days. In contrast, animals treated with 2 doses had significant improvements in lung maturation at 2, 5, and 7 days, with treatment efficacy reduced by 10 days.

CONCLUSION

In preterm lambs, the durability of antenatal corticosteroids treatment depends on the duration of fetal exposure and is independent of the intravenous or intramuscular maternal route of administration. For acute 24- to 48-hour posttreatment deliveries, a 24-hour fetal antenatal corticosteroids exposure was sufficient for lung maturation. A fetal exposure duration of at least 48 hours was necessary to maintain long-term treatment durability. A single-dose ACS treatment should be sufficient for women delivering within <48 hours of antenatal corticosteroids treatment.

Oral antenatal corticosteroids evaluated in fetal sheep

BACKGROUND

The use of antenatal corticosteroids (ACS) in low-resource environments is sporadic. Further, drug choice, dose, and route of ACS are not optimized. We report the pharmacokinetics and pharmacodynamics of oral dosing of ACS using a preterm sheep model.

METHODS

We measured pharmacokinetics of oral betamethasone-phosphate (Beta-P) and dexamethasone-phosphate (Dex-P) using catheterized pregnant sheep. We compared fetal lung maturation responses of oral Beta-P and Dex-P to the standard treatment with 2 doses of the i.m. mixture of Beta-P and betamethasone-acetate at 2, 5, and 7 days after initiation of ACS.

RESULTS

Oral Dex-P had lower bioavailability than Beta-P, giving a lower maximum maternal and fetal concentration. A single oral dose of 0.33 mg/kg of Beta-P was equivalent to the standard clinical treatment assessed at 2 days; 2 doses of 0.16 mg/kg of oral Beta-P were equivalent to the standard clinical treatment at 7 days as assessed by lung mechanics and gas exchange after preterm delivery and ventilation. In contrast, oral Dex-P was ineffective because of its decreased bioavailability.

CONCLUSION

Using a sheep model, we demonstrate the use of pharmacokinetics to develop oral dosing strategies for ACS. Oral dosing is feasible and may facilitate access to ACS in low-resource environments.