Maternal surgery during pregnancy has a transient adverse effect on the developing fetal rabbit brain

Prenatal treprostinil improves pulmonary arteriolar hypermuscularization in the rabbit model of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a congenital malformation characterized by pulmonary hypoplasia, pulmonary hypertension, and cardiac dysfunction. Pulmonary hypertension represents the major cause of neonatal mortality and morbidity. Prenatal diagnosis allows assessment of severity and selection of foetal surgery candidates. We have shown that treprostinil, a prostacyclin analogue with an anti-remodelling effect, attenuates the relative hypermuscularization of the pulmonary vasculature in rats with nitrofen-induced CDH. Here we confirm these observations in a large animal model of surgically-created CDH. In the rabbit model, subcutaneous maternal administration of treprostinil at 150 ng/kg/min consistently reached target foetal concentrations without demonstrable detrimental foetal or maternal adverse effects. In pups with CDH, prenatal treprostinil reduced pulmonary arteriolar proportional medial wall thickness and downregulated inflammation and myogenesis pathways. No effect on alveolar morphometry or lung mechanics was observed. These findings provide further support towards clinical translation of prenatal treprostinil for CDH.

Long-term pulmonary and neurodevelopmental impairment in a fetal growth restriction rabbit model

Fetal growth restriction (FGR) remains one of the main obstetrical problems worldwide, with consequences beyond perinatal life. Animal models with developmental and structural similarities to the human are essential to understand FGR long-term consequences and design novel therapeutic strategies aimed at preventing or ameliorating them. Herein, we described the long-term consequences of FGR in pulmonary function, structure, and gene expression, and characterized neurodevelopmental sequelae up to preadolescence in a rabbit model. FGR was induced at gestational day 25 by surgically reducing placental blood supply in one uterine horn, leaving the contralateral horn as internal control. Neonatal rabbits born near term were assigned to foster care in mixed groups until postnatal day (PND) 21. At that time, one group underwent pulmonary biomechanical testing followed by lung morphometry and gene expression analysis. A second group underwent longitudinal neurobehavioral assessment until PND 60 followed by brain harvesting for multiregional oligodendrocyte and microglia quantification. FGR was associated with impaired pulmonary function and lung development at PND 21. FGR rabbits had higher respiratory resistance and altered parenchymal biomechanical properties in the lungs. FGR lungs presented thicker alveolar septal walls and reduced alveolar space. Furthermore, the airway smooth muscle content was increased, and the tunica media of the intra-acinar pulmonary arteries was thicker. In addition, FGR was associated with anxiety-like behavior, impaired memory and attention, and lower oligodendrocyte proportion in the frontal cortex and white matter. In conclusion, we documented and characterized the detrimental pulmonary function and structural changes after FGR, independent of prematurity, and beyond the neonatal period for the first time in the rabbit model, and describe the oligodendrocyte alteration in pre-adolescent rabbit brains. This characterization will allow researchers to develop and test therapies to treat FGR and prevent its sequelae.

Duration of fetoscopic spina bifida repair does not affect the central nervous system in fetal lambs

BACKGROUND

Prenatal spina bifida aperta repair improves neurologic outcomes yet comes with a significant risk of prematurity and uterine scar-related complications. To reduce such complications, different fetoscopic techniques, for example, with varying numbers of ports, are being explored. This has an effect on the duration of the procedure, potentially affecting central nervous system development. Both the condition and anesthesia can affect the central nervous system, particularly the hippocampus, a region crucial for prospective and episodic memory. Previous animal studies have shown the potential influence of anesthesia, premature delivery, and maternal surgery during pregnancy on this area.

OBJECTIVE

This study aimed to compare the effects of 2- vs 3-port fetoscopic spina bifida aperta repair in the fetal lamb model using neuron count of the hippocampus as the primary outcome.

STUDY DESIGN

Based on the hippocampal neuron count from previous lamb experiments, we calculated that we required 5 animals per group to achieve a statistical power of ≥ 80%. A spina bifida aperta defect was developed in fetal lambs at 75 days of gestation (term: 145 days). At 100 days, fetuses underwent either a 2-port or 3-port fetoscopic repair. At 143 days, all surviving fetuses were delivered by cesarean delivery, anesthetized, and transcardially perfused with a mixture of formaldehyde and gadolinium. Next, they underwent neonatal brain and spine magnetic resonance imaging after which these organs were harvested for histology. Hippocampus, frontal cortex, caudate nucleus, and cerebellum samples were immunostained to identify neurons, astrocytes, microglia, and markers associated with cell proliferation, myelination, and synapses. The degree of hindbrain herniation and the ventricular diameter were measured on magnetic resonance images and volumes of relevant brain and medulla areas were segmented.

RESULTS

Both treatment groups included 5 fetuses and 9 unoperated littermates served as normal controls. The durations for both skin-to-skin (341±31 vs 287±40 minutes; P=.04) and fetal surgery (183±30 vs 128±22; P=.01) were longer for the 2-port approach than for the 3-port approach. There was no significant difference in neuron density in the hippocampus, frontal cortex, and cerebellum. In the caudate nucleus, the neuron count was higher in the 2-port group (965±156 vs 767±92 neurons/mm2; P=.04). There were neither differences in proliferation, astrogliosis, synaptophysin, or myelin. The tip of the cerebellar vermis was closer to the foramen magnum in animals undergoing the 2-port approach than in animals undergoing the 3-port approach (-0.72±0.67 vs -2.47±0.91 mm; P=.009). There was no significant difference in the ratio of the hippocampus, caudate nucleus, or cerebellar volume to body weight. For the spine, no difference was noted in spine volume-to-body weight ratio for the lower (L1-L2), middle (L3-L4), and higher (L5-L6) levels. Compared with controls, in repaired animals, the cerebellar vermis tip laid closer to the foramen magnum, parietal ventricles were enlarged, and medulla volumes were reduced.

CONCLUSION

In the experimental spina bifida fetal lamb model, a 2-port repair took 40% longer than a 3-port repair. However, there was no indication of any relevant morphologic differences in the fetal brain.

Pregnancy hypertension-associated endothelial dysfunction is attenuated by isoflurane anesthesia: Evidence of protective effect related to increases in nitric oxide

AIMS

Pregnancy hypertension-induced endothelial dysfunction associated with impairment of nitric oxide (NO) bioavailability and hemodynamic derangements is a challenging for urgent procedures requiring maternal anesthesia. The volatile anesthetic isoflurane has demonstrated NO-associated protective effects. However, this isoflurane-induced effect is still unclear in pregnancy hypertension. Therefore, the present study examined the potential protective effects of isoflurane anesthesia on endothelial dysfunction and hemodynamic changes induced by hypertensive pregnancy associated with fetal and placental growth restrictions.

MATERIALS AND METHODS

Animals were distributed into four groups: normotensive pregnant rats (Preg), anesthetized pregnant rats (Preg+Iso), hypertensive pregnant rats (HTN-Preg), and anesthetized hypertensive pregnant rats (HTN-Preg+Iso). Systolic and diastolic pressures, mean arterial pressure (MAP), heart rate, fetal and placental weights, vascular contraction, endothelium-derived NO-dependent vasodilation, and NO levels were assessed. The vascular endothelial growth factor (VEGF) levels and endothelial NO synthase (eNOS) Serine (1177) phosphorylation (p-eNOS) expression were also examined.

KEY FINDINGS

Isoflurane produced more expressive hypotensive effects in the HTN-Preg+Iso versus Preg+Iso group, with respective reductions in MAP by 50 ± 13 versus 25 ± 4 mmHg (P < 0.05). Also, HTN-Preg+Iso compared to the HTN-Preg group showed (respectively) preventions against the weight loss of the fetuses (4.0 ± 0.6 versus 2.8 ± 0.6 g, P < 0.05) and placentas (0.37 ± 0.06 versus 0.30 ± 0.06 mg, P < 0.05), hyper-reactive vasocontraction response (1.8 ± 0.4 versus 2.8 ± 0.6 g, P < 0.05), impaired endothelium-derived NO-dependent vasodilation (84 ± 8 versus 50 ± 17 %, P < 0.05), reduced VEGF levels (147 ± 46 versus 25 ± 13 pg/mL, P < 0.05), and decreased p-eNOS expression (0.24 ± 0.07 versus 0.09 ± 0.05 arbitrary units, P < 0.05).

SIGNIFICANCE

Isoflurane anesthesia protects maternal endothelial function in pregnancy hypertension, and possibly endothelium-derived NO is involved.

Effects of cumulative duration of repeated anaesthesia exposure on foetal brain development in the ovine model

OBJECTIVE

Anaesthesia is required in 0.4-1% of pregnant women, and prolonged and repeated exposures to anaesthesia may be required. It is unknown whether these exposures may result in foetal neurotoxicity in humans. As sheep have a gestation comparable to that of humans, the objective of this study was to analyse the neurodevelopmental outcome of ovine foetuses that had been exposed in utero to repeated and prolonged anaesthesia.

DESIGN

Randomized controlled preclinical study.

SETTING

Anaesthesia for non-obstetric surgery during pregnancy.

ANIMALS

Twenty-four healthy pregnant Swifter ewes.

INTERVENTIONS

The ewes were randomized to no anaesthesia exposure (control-group), single exposure (at gestational age 68-70 days), or repeated exposure (at gestational age 68-70 days and 96-98 days) to 2.5 h of sevoflurane anaesthesia and maternal laparotomy. All lambs were delivered at approximately term gestation (gestational age: 140-143 days).

MEASUREMENTS

The primary outcome was neuron density in the frontal cortex 24 h after birth for the control-group versus the repeated-exposure-group. Key secondary outcome was the time needed to achieve the milestone of standing. Secondary outcomes included other neurobehavioural assessments (e.g., motoric milestones) and histological parameters quantified in multiple brain regions (neuron density, total cell density, proliferation, inflammation, synaptogenesis, astrocytes and myelination).

MAIN RESULTS

Neuron density in the frontal cortex did not differ between groups (mean ± standard deviation: control-group: 403 ± 39, single-exposure group: 436 ± 23 and repeated-exposure-group: 403 ± 40 neurons/mm2, control-group versus repeated-exposure-group: p = 0.986, control-group versus single-exposure-group: p = 0.097). No significant difference was observed for the time needed to achieve the milestone of standing. Only very limited differences were observed for other histological outcome parameters and neurobehavioural assessments.

CONCLUSIONS

There is no evidence for foetal neuronal injury or neurobehavioural impairments after a cumulative duration of 5 h repetitive prenatal anaesthesia in sheep.

Prenatal Exposure to General Anesthesia Drug Esketamine Impaired Neurobehavior in Offspring

Prenatal exposure to anesthetics has raised increasing attention about the neuronal development in offspring. Animal models are usually used for investigation. As a new drug, esketamine is the s-isoform of ketamine and is twice as potent as the racemic ketamine with less reported adverse effects. Esketamine is currently being used and become more favorable in clinical anesthesia work, including surgeries during pregnancy, yet the effect on the offspring is unknown. The present study aimed to elucidate the effects of gestational administration of esketamine on neuronal development in offspring, using a rat model. Gestational day 14.5 pregnant rats received intravenous injections of esketamine. The postnatal day 0 (P0) hippocampus was digested and cultured in vitro to display the neuronal growth morphology. On Day 4 the in vitro experiments revealed a shorter axon length and fewer dendrite branches in the esketamine group. The results from the EdU- imaging kit showed decreased proliferative capacity in the subventricular zone (SVZ) and dentate gyrus (DG) in both P0 and P30 offspring brains in the esketamine group. Moreover, neurogenesis, neuron maturity and spine density were impaired, resulting in attenuated long-term potentiation (LTP). Compromised hippocampal function accounted for the deficits in neuronal cognition, memory and emotion. The evidence obtained suggests that the neurobehavioral deficit due to prenatal exposure to esketamine may be related to the decrease phosphorylation of CREB and abnormalities in N-methyl-D-aspartic acid receptor subunits. Taken together, these results demonstrate the negative effect of prenatal esketamine exposure on neuronal development in offspring rats. G14.5 esketamine administration influenced the neurobehavior of the offspring in adolescence. Poorer neuronal growth and reduced brain proliferative capacity in late gestation and juvenile pups resulted in impaired P30 neuronal plasticity and synaptic spines as well as abnormalities in NMDAR subunits. Attenuated LTP reflected compromised hippocampal function, as confirmed by behavioral tests of cognition, memory and emotions. This figure was completed on the website of Figdraw.

Brain development is altered in rabbit fetuses with congenital diaphragmatic hernia

INTRODUCTION

Children with congenital diaphragmatic hernia (CDH) are at risk for neurodevelopmental delay. Some changes are already present prenatally. Herein, we further examined how the brain develops in fetal rabbits with surgically created DH.

METHODS

Two fetuses underwent surgical DH creation on day 23 (term = d31). DH pups and littermate controls were harvested at term. Ten DH pups and 11 controls underwent transcardial perfusion for brain fixation and measurement of brain volume, brain folding, neuron and synaptic density, pre-oligodendrocyte count, proliferation, and vascularization. Twelve other DH and 11 controls had echocardiographic assessment of cardiac output and aortic and cerebral blood flow, magnetic resonance imaging (9.4 T) for cerebral volumetry, and molecular assessment of vascularization markers.

RESULTS

DH pups had lower lung-to-body weight ratio (1.3 ± 0.3 vs. 2.4 ± 0.3%; p < 0.0001) and lower heart-to-body weight ratio (0.007 ± 0.001 vs. 0.009 ± 0.001; p = 0.0006) but comparable body weight and brain-to-body weight ratio. DH pups had a lower left ventricular ejection fraction, aortic and cerebral blood flow (39 ± 8 vs. 54 ± 15 mm/beat; p = 0.03) as compared to controls but similar left cardiac ventricular morphology. Fetal DH-brains were similar in volume but the cerebellum was less folded (perimeter/surface area: 25.5 ± 1.5 vs. 26.8 ± 1.2; p = 0.049). Furthermore, DH brains had a thinner cortex (143 ± 9 vs. 156 ± 13 μm; p = 0.02). Neuron densities in the white matter were higher in DH fetuses (124 ± 18 vs. 104 ± 14; p = 0.01) with comparable proliferation rates. Pre-oligodendrocyte count was lower, coinciding with the lower endothelial cell count.

CONCLUSION

Rabbits with DH had altered brain development compared to controls prenatally, indicating that brain development is already altered prenatally in CDH.

Protocols for the Evaluation of Neurodevelopmental Alterations in Rabbit Models In Vitro and In Vivo

The rabbit model is gaining importance in the field of neurodevelopmental evaluation due to its higher similarity to humans in terms of brain development and maturation than rodents. In this publication, we detailed 14 protocols covering toxicological relevant endpoints for the assessment of neurodevelopmental adverse effects in the rabbit species. These protocols include both in vitro and in vivo techniques, which also cover different evaluation time-points, the neonatal period, and long-term examinations at postnatal days (PNDs) 50–70. Specifically, the protocols (P) included are as follows: neurosphere preparation (GD30/PND0; P2) and neurosphere assay (P3), behavioral ontogeny (PND1; P4), brain obtaining and brain weight measurement at two different ages: PND1 (P5) and PND70 (P12), neurohistopathological evaluations after immersion fixation for neurons, astrocytes, oligodendrocytes and microglia (PND1; P6-9) or perfusion fixation (PND70; P12), motor activity (P11, open field), memory and sensory function (P11, object recognition test), learning (P10, Skinner box), and histological evaluation of plasticity (P13 and P14) through dendritic spines and perineuronal nets. The expected control values and their variabilities are presented together with the information on how to troubleshoot the most common issues related to each protocol. To sum up, this publication offers a comprehensive compilation of reliable protocols adapted to the rabbit model for neurodevelopmental assessment in toxicology.

Neurocognitive sequelae of antenatal corticosteroids in a late preterm rabbit model

BACKGROUND

Late preterm birth is associated with short-term respiratory and adaptive problems. Although antenatal corticosteroids seem to reduce the respiratory burden, this may come at the cost of adverse neuropsychological outcomes later in life. This impact has not been investigated.

OBJECTIVE

Herein, we investigate what the short- and long-term neurodevelopmental effects of a single course of betamethasone in simulated late preterm birth.

STUDY DESIGN

Time-mated pregnant does received 0.1 mg/kg betamethasone (n=8) or 1 mL saline intramuscular (n=6) at the postconceptional ages of 28 and 29 days. The antenatal corticosteroid dose and scheme were based on previous studies and were comparable with routine clinical use. Cesarean delivery was done on postconceptional age 30 days (term=31 days), and new-born rabbits were foster-cared for 28 days and were thereafter cared for in group housing. Neonatal lung function testing and short-term neurobehavioral testing was done. Open field, spontaneous alternation, and novel object recognition tests were subsequently performed at 4 and 8 weeks of age. On postnatal day 1 and at 8 weeks, a subgroup was euthanized and transcardially perfuse fixated. Ex vivo high-resolution Magnetic Resonance Imaging was used to calculate the Diffusion Tensor Imaging-derived fractional anisotropy and mean diffusivity. Fixated brains underwent processing and were serial sectioned, and a set of 3 coronal sections underwent anti-NeuN, Ki67, and terminal deoxynucleotidyl transferase dUTP nick end labeling staining.

RESULTS

Antenatal corticosteroid exposure was associated with improved neonatal lung function, yet resulted in a long-term growth deficit that coincided with a persistent neurobehavioral deficit. We demonstrated lower neonatal motor scores; a persistent anxious behavior in the open field test with more displacements, running, and self-grooming episodes; persistent lower alternation scores in the T-Maze test; and lower discriminatory indexes in the novel object recognition. On neuropathological assessment, antenatal corticosteroid exposure was observed to result in a persistent lower neuron density and fewer Ki67+ cells, particularly in the hippocampus and the corpus callosum. This coincided with lower diffusion tensor imaging-derived fractional anisotropy scores in the same key regions.

CONCLUSION

Clinical equivalent antenatal corticosteroid exposure in this late preterm rabbit model resulted in improved neonatal lung function. However, it compromised neonatal and long-term neurocognition.

Neurodevelopmental effects of maternal blood pressure management with noradrenaline during general anaesthesia for nonobstetric surgery in the pregnant rabbit model

BACKGROUND

In pregnant women, anaesthesia-induced hypotension is commonly treated using phenylephrine or noradrenaline, the rationale being to maintain uterine perfusion pressure and thereby uterine blood flow. Evidence for this strategy during general anaesthesia for nonobstetric surgery is absent.

OBJECTIVE

To analyse the effects of treating anaesthesia-induced hypotension with noradrenaline on brain development of rabbit foetuses of mothers subjected to general anaesthesia for nonobstetric surgery. We hypothesised that treatment of maternal hypotension would improve foetal outcomes.

DESIGN

Randomised controlled laboratory study using 21 pregnant rabbits (does) at 28 days of gestation.

INTERVENTION

Two hours of sevoflurane anaesthesia for a laparotomy without treatment of anaesthesia-induced hypotension (hypotension group) or with maintaining maternal mean arterial pressure above 80% of the awake value using noradrenaline (noradrenaline group). In the control group, does remained untouched. At term, all pups were delivered by caesarean section. One day later, the neurobehaviour of the pups was assessed and brains were harvested.

MAIN OUTCOMES

Neuron density in the frontal cortex for the comparison of noradrenaline groups versus hypotension groups was the primary outcome; the neurobehavioural scores and other histological outcomes were secondary outcomes.

RESULTS

In the noradrenaline groups and hypotension groups, neuron density in the frontal cortex was similar (1181 ± 162 versus 1189 ± 200 neurons mm-2, P = 0.870). However, significantly less foetal survival, lower sensory scores in neurobehavioural assessment and less proliferation were observed in the noradrenaline group when compared with the hypotension group. Neuron densities in other regions, total cell densities, biometrics and synaptogenesis were not affected. There were no differences between the control group and hypotension group.

CONCLUSION

During general anaesthesia for nonobstetric surgery in rabbits, treatment of anaesthesia-induced hypotension using noradrenaline did not affect neuron densities but was associated with impaired foetal outcomes according to several secondary outcome parameters. Further studies are needed to investigate any clinical relevance and to determine the target blood pressure in pregnant women during general anaesthesia.

Fetoscopic insufflation of heated-humidified carbon dioxide during simulated spina bifida repair is safe under controlled anesthesia in the fetal lamb

OBJECTIVE

To assess the safety of Partial-Amniotic-Insufflation-of-heated-humidified-CO₂ (hPACI) during fetoscopic spina bifida repair (fSB-repair).

METHOD

A simulated fSB-repair through an exteriorized uterus under hPACI was performed in 100-day fetal lambs (term = 145 days) under a laboratory anesthesia protocol (n = 5; group 1) which is known to induce maternal-fetal acidosis and hypercapnia. Since these may not occur clinically, we applied a clinical anesthesia protocol (n = 5; group 2), keeping maternal parameters within physiological conditions, that is, controlled maternal arterial carbon dioxide (CO2) pressure (pCO₂  = 30 mmHg), blood pressure (≥67 mmHg), and temperature (37.1-39.8°C). Our superiority study used fetal pH as the primary outcome.

RESULTS

Compared to group 1, controlled anesthesia normalized fetal pH (7.23 ± 0.02 vs. 7.36 ± 0.02, p < 0.001), pCO₂ (70.0 ± 9.1 vs. 43.0 ± 1.0 mmHg, p = 0.011) and bicarbonate (27.8 ± 1.1 vs. 24.0 ± 0.9 mmol/L, p = 0.071) at baseline. It kept them within clinically acceptable limits (pH ≥ 7.23, pCO₂  ≤ 70 mmHg, bicarbonate ≤ 30 mm/L) for ≥120 min of hPACI as opposed to ≤30 min in group one. Fetal pO₂ and lactate were comparable between groups and generally within normal range. Fetal brain histology demonstrated fewer apoptotic cells and higher neuronal density in the prefrontal cortex in group two. There was no difference in fetal membrane inflammation, which was mild.

CONCLUSION

Fetoscopic insufflation of heated-humidified CO₂ during simulated fSB-repair through an exteriorized uterus can be done safely under controlled anesthesia.

Fetal surgery has no additional effect to general anesthesia on brain development in neonatal rabbits

BACKGROUND

Fetal surgery is part of modern fetal medicine, and some procedures, such as fetal spina bifida repair, are performed under general anesthesia. Fetuses are operated on in a time window when the developing brain is extremely vulnerable to external, potentially harmful factors. To date, little is known about the effect of fetal surgery on fetal brain development.

OBJECTIVE

This study aimed to assess the effect of fetal surgery on the developing fetal brain in the rabbit model.

STUDY DESIGN

This was a randomized, sham-controlled study in time-mated pregnant does at 28 days' gestation (term, 31 days), which corresponds to the start of the peak of brain development and end of the second trimester of pregnancy in humans. We included 4 different groups in this experiment: no-surgery, general anesthesia, general anesthesia+hysterotomy, and general anesthesia+fetal surgery. In 11 does, anesthesia was induced using propofol and maintained for 75 minutes with 3.6 vol% (4% is the equivalent of 1 minimum alveolar concentration) sevoflurane. Maternal blood pressure, heart rate, oxygen saturation, temperature, end-tidal CO2 were continuously monitored. For each operated doe, 6 fetuses were part of the experiment. Randomization determined which cornual sac and what opposing third sac were assigned to fetal surgery: hysterotomy, fetal injection (atropine, fentanyl, and cisatracurium), fetal skin incision, and suturing. Only hysterotomy was performed on the opposing cornual and third amniotic sacs of the does. The fetus in these experimental sacs was used as internal unmanipulated control (general anesthesia). All fetuses (n=38) from unmanipulated does (n=4) served as external controls (no-surgery). At term, the does were delivered by cesarean delivery under ketamine-medetomidine sedation and local anesthesia. The pups underwent standardized motoric and sensory neurologic testing on day 1 followed by euthanasia and brain harvesting for histologic assessment of neurons, synapses, proliferation, and glial cells.

RESULTS

Maternal vital signs were stable during surgery. Survival was similar in the 4 groups (75%-94%), and brain-to-body weight ratio was comparable; only the no-surgery pups had a higher brain weight. On postnatal day 1, the pups in the 4 groups had a comparable neurobehavioral outcome on both motoric and sensory testing. In the prefrontal cortex, no-surgery pups had significantly higher neuron density than pups who underwent maternal surgery, but there was no difference among pups that underwent general anesthesia, hysterotomy, or fetal surgery. The measurements of proliferation had a similar outcome: a higher proliferation rate in the prefrontal cortex of no-surgery pups. Moreover, synaptic density values were higher in the no-surgery pups, but there was no difference observed among pups who underwent general anesthesia, hysterotomy, and fetal surgery. Lastly, there was no difference in gliosis among the 4 groups.

CONCLUSION

In rabbits, fetal surgery through hysterotomy under maternal general anesthesia did not affect brain development, in addition to the effects of general anesthesia per se.

Neurocognitive Effects of Fetal Exposure to Anesthesia

Surgery during pregnancy occurs when maternal or fetal needs outweigh the status quo, yet much uncertainty remains regarding the effects of anesthesia and surgery on fetal neurodevelopment. This article will review common maternal and fetal indications for invasive procedures, along with contemporary research on fetal neurodevelopment following anesthesia and surgery, focusing on future areas of investigation.

Impact of In Utero Exposure to Antiepileptic Drugs on Neonatal Brain Function

In utero brain development underpins brain health across the lifespan but is vulnerable to physiological and pharmacological perturbation. Here, we show that antiepileptic medication during pregnancy impacts on cortical activity during neonatal sleep, a potent indicator of newborn brain health. These effects are evident in frequency-specific functional brain networks and carry prognostic information for later neurodevelopment. Notably, such effects differ between different antiepileptic drugs that suggest neurodevelopmental adversity from exposure to antiepileptic drugs and not maternal epilepsy per se. This work provides translatable bedside metrics of brain health that are sensitive to the effects of antiepileptic drugs on postnatal neurodevelopment and carry direct prognostic value.

Maternal sevoflurane exposure induces temporary defects in interkinetic nuclear migration of radial glial progenitors in the fetal cerebral cortex through the Notch signalling pathway

OBJECTIVES

The effects of general anaesthetics on fetal brain development remain elusive. Radial glial progenitors (RGPs) generate the majority of neurons in developing brains. Here, we evaluated the acute alterations in RGPs after maternal sevoflurane exposure.

METHODS

Pregnant mice were exposed to 2.5% sevoflurane for 6 hours on gestational day 14.5. Interkinetic nuclear migration (INM) of RGPs in the ventricular zone (VZ) of the fetal brain was evaluated by thymidine analogues labelling. Cell fate of RGP progeny was determined by immunostaining using various neural markers. The Morris water maze (MWM) was used to assess the neurocognitive behaviours of the offspring. RNA sequencing (RNA-Seq) was performed for the potential mechanism, and the potential mechanism validated by quantitative real-time PCR (qPCR), Western blot and rescue experiments. Furthermore, INM was examined in human embryonic stem cell (hESC)-derived 3D cerebral organoids.

RESULTS

Maternal sevoflurane exposure induced temporary abnormities in INM, and disturbed the cell cycle progression of RGPs in both rodents and cerebral organoids without cell fate alternation. RNA-Seq analysis, qPCR and Western blot showed that the Notch signalling pathway was a potential downstream target. Reactivation of Notch by Jag1 and NICD overexpression rescued the defects in INM. Young adult offspring showed no obvious cognitive impairments in MWM.

CONCLUSIONS

Maternal sevoflurane exposure during neurogenic period temporarily induced abnormal INM of RGPs by targeting the Notch signalling pathway without inducing long-term effects on RGP progeny cell fate or offspring cognitive behaviours. More importantly, the defects of INM in hESC-derived cerebral organoids provide a novel insight into the effects of general anaesthesia on human brain development.

Effects of general anaesthesia during pregnancy on neurocognitive development of the fetus: a systematic review and meta-analysis

BACKGROUND

The US Food and Drug Administration warned that exposure of pregnant women to general anaesthetics may impair fetal brain development. This review systematically evaluates the evidence underlying this warning.

METHODS

PubMed, EMBASE, and Web of Science were searched from inception until April 3, 2020. Preclinical and clinical studies were eligible. Exclusion criteria included case reports, in vitro models, chronic exposures, and exposure only during delivery. Meta-analyses were performed on standardised mean differences. The primary outcome was overall effect on learning/memory. Secondary outcomes included markers of neuronal injury (apoptosis, synapse formation, neurone density, and proliferation) and subgroup analyses.

RESULTS

There were 65 preclinical studies included, whereas no clinical studies could be identified. Anaesthesia during pregnancy impaired learning and memory (standardised mean difference -1.16, 95% confidence interval -1.46 to -0.85) and resulted in neuronal injury in all experimental models, irrespective of the anaesthetic drugs and timing in pregnancy. Risk of bias was high in most studies. Rodents were the most frequently used animal species, although their brain development differs significantly from that in humans. In a minority of studies, anaesthesia was combined with surgery. Monitoring and strict control of physiological homeostasis were below preclinical and clinical standards in many studies. The duration and frequency of exposure and anaesthetic doses were often much higher than in clinical routine.

CONCLUSION

Anaesthesia-induced neurotoxicity during pregnancy is a consistent finding in preclinical studies, but translation of these results to the clinical situation is limited by several factors. Clinical observational studies are needed.

PROSPERO REGISTRATION NUMBER

CRD42018115194.

Fetally-injected drugs for immobilization and analgesia do not modify fetal brain development in a rabbit model

OBJECTIVE

During fetal surgery, fetuses receive medication (atropine-fentanyl-curare) to prevent fetal pain, movement and bradycardia. Although essential there has been no detailed review of potential side effects. Herein we aimed to assess the effects of this medication cocktail on fetal brain development in a rabbit model.

METHODS

Pregnant does underwent laparotomy at 28 days of gestation. Two pups of each horn were randomized to an ultrasound guided injection with medication (atropine-cisatracurium-fentanyl, as clinically used) or saline (sham). The third pup was used as control. At term, does were delivered by cesarean. Outcome measures were neonatal biometry, neuromotoric functioning and neuro-histology (neuron density, synaptic density and proliferation).

RESULTS

Maternal vital parameters remained stable during surgery. Fetal heart rates did not differ before and after injection, and were comparable for the three groups. At birth, neonatal body weights and brain-to-body weight ratios were also comparable. Both motor and sensory neurobehavioral scores were comparable. There were no differences in neuron density or proliferation. Sham pups, had a lower synaptic density in the hippocampus as compared to the medication group, however there was no difference in the other brain areas.

CONCLUSION

In the rabbit model, fetal medication does not appear to lead to short-term neurocognitive effects.

Fetoscopic myelomeningocoele closure: Is the scientific evidence enough to challenge the gold standard for prenatal surgery?

Since the completion of the Management of Myelomeningocoele Study, maternal-fetal surgery for spina bifida has become a valid option for expecting parents. More recently, multiple groups are exploring a minimally invasive approach and recent outcomes have addressed many of the initial concerns with this approach. Based on a previously published framework, we attempt to delineate the developmental stage of the surgical techniques. Furthermore, we discuss the barriers of performing randomized controlled trials comparing two surgical interventions and suggest that data collection through registries is an alternative method to gather high-grade evidence.

Effects of Maternal Abdominal Surgery on Fetal Brain Development in the Rabbit Model

INTRODUCTION

Anesthesia during pregnancy can impair fetal neurodevelopment, but effects of surgery remain unknown. The aim is to investigate effects of abdominal surgery on fetal brain development. Hypothesis is that surgery impairs outcome.

METHODS

Pregnant rabbits were randomized at 28 days of gestation to 2 h of general anesthesia (sevoflurane group, n = 6) or to anesthesia plus laparoscopic appendectomy (surgery group, n = 13). On postnatal day 1, neurobehavior of pups was assessed and brains harvested. Primary outcome was neuron density in the frontal cortex, and secondary outcomes included neurobehavioral assessment and other histological parameters.

RESULTS

Fetal survival was lower in the surgery group: 54 versus 100% litters alive at birth (p = 0.0442). In alive litters, pup survival until harvesting was 50 versus 69% (p = 0.0352). No differences were observed for primary outcome (p = 0.5114) for surviving pups. Neuron densities were significantly lower in the surgery group in the caudate nucleus (p = 0.0180), but not different in other regions. No differences were observed for secondary outcomes. Conclusions did not change after adjustment for mortality.

CONCLUSION

Abdominal surgery in pregnant rabbits at a gestational age corresponding to the end of human second trimester results in limited neurohistological changes but not in neurobehavioral impairments. High intrauterine mortality limits translation to clinical scenario, where fetal mortality is close to zero.

Long-term neurological effects of neonatal caffeine treatment in a rabbit model of preterm birth

BACKGROUND

Neonatal caffeine treatment might affect brain development. Long-term studies show conflicting results on brain-related outcomes. Herein we aimed to investigate the long-term effects of neonatal caffeine administration in a rabbit model of preterm birth.

METHODS

Preterm (born day 29) and term (day 32) pups were raised by wet nurses and allocated to treatment with saline or caffeine for 7 or 17 days. At pre-puberty, neurobehavioral tests were performed and brains were harvested for immunostaining of neurons, synapses, myelin, and astrocytes.

RESULTS

Survival was lower in preterm saline pups than in controls, whereas caffeine-treated preterm pups did not differ from term control pups. Preterm saline pups covered less distance compared to controls and were more likely to stay in the peripheral zone of the open field. Corresponding differences were not seen in preterm caffeine pups. Preterm animals had lower neuron density compared to controls, which was not influenced by caffeine treatment. Synaptic density, astrocytes, and myelin were not different between groups.

CONCLUSION

Caffeine appeared to be safe. All preterm rabbits had lower neuron density but anxious behavior seen in preterm saline rabbits was not seen in caffeine-treated preterm pups.