New concepts in perinatal hypoxia ischemia encephalopathy

Examining the relationship between autism spectrum disorder in children whose mother had labour epidural analgesia for their birth: A retrospective cohort study

BACKGROUND

Controversy exists regarding the association between autism spectrum disorder (ASD) in children whose mother had labour epidural analgesia for their birth, as the few existing investigations have reported mixed findings.

OBJECTIVE

This study aims to evaluate the possibility of an association in our heterogeneous population.

DESIGN

A retrospective population-based cohort study.

SETTING

Vaginal deliveries that took place between the years 2005 and 2017 at Soroka University Medical Center, a tertiary referral hospital in Israel, and a follow-up on the incidence of ASD in the children.

PATIENTS

A hundred and thirty-nine thousand, nine hundred and eighty-one labouring patients and their offspring.

MAIN OUTCOME MEASURES

The incidence of children diagnosed with ASD (both hospital and community-based diagnoses) was compared based on whether their mothers had received labour epidural analgesia during their labour. A Kaplan-Meier survival curve compared cumulative incidence of ASD. A Cox proportional hazards model was used to control for relevant confounders.

RESULTS

Labour epidural analgesia was administered to 33 315 women. Epidural analgesia was more common among high-risk pregnancy groups (including pregnancies complicated with diabetes mellitus, hypertensive disorders, intrauterine growth restriction, and oligohydramnios; P  < 0.001). In a Cox proportional hazards model, the association between epidural analgesia during labour and ASD in the children lost statistical significance following adjustment for confounders such as maternal age, gestational age, hypertensive disorders, diabetes mellitus, and ethnicity [adjusted hazard ratio = 1.13, 95% confidence interval (CI), 0.96 to 1.34, P  = 0.152].

CONCLUSION

In our population, after adjusting for confounders, epidural analgesia is not independently associated with autism spectrum disorder in the children. These findings enhance our knowledge regarding the safety of epidural analgesia and enable patients to make informed decisions about their pain relief techniques during labour.

Aqueous extract of Dendrobium officinale confers neuroprotection against hypoxic-ischemic brain damage in neonatal rats

Accumulating evidences have proved the protective role of traditional Chinese medicine in improving neurological damage induced by cerebral hypoxia-ischemia. Herein, we hypothesized that Dendrobium officinale aqueous extract exerted neuroprotection against brain damage. Initially, a model of hypoxic-ischemic brain damage (HIBD) was induced in neonatal rats, which were subsequently intragastrically administered with different doses of Dendrobium officinale aqueous extract. Next, the antioxidant capacity was examined by enzyme-linked immunosorbent assay. 2,3,5-Triphenyltetrazolium chloride and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining assays were adopted to determine neuronal apoptosis in brain tissues. Furthermore, neurotrophic factors and hypoxia-inducible factor-1α (HIF-1α) expression was identified by Western blot analysis. The neonatal rat models of HIBD presented impaired neurobehaviors and antioxidant capacity, increased neuronal apoptosis and expression of HIF-1α and histone deacetylase 1 (HDAC1), as well as diminished expression of neurotrophic factors and K⁺ -Cl^- -cotransporter 2 (KCC2). Notably, in response to different doses of Dendrobium officinale aqueous extract, the impairment on neurobehaviors and antioxidant capacity was alleviated, accompanied by reduced levels of nitric oxide synthase, nitric oxide, and malondialdehyde, and increased superoxide dismutase activity. Besides, the neuronal apoptosis was inhibited as reflected by down-regulated cleaved caspase-3 and Bax and up-regulated Bcl-2. Moreover, we also found accelerated expression of neurotrophic factors and KCC2 and diminished expression of HIF-1α and HDAC1. Altogether, this present study highlights that the aqueous extract of Dendrobium officinale can suppress the neuronal apoptosis and enhance the expression of neurotrophic factors to protect neonatal rats against HIBD.

Treatment With Tetrahydrobiopterin Improves White Matter Maturation in a Mouse Model for Prenatal Hypoxia in Congenital Heart Disease

Background Reduced oxygen delivery in congenital heart disease causes delayed brain maturation and white matter abnormalities in utero. No treatment currently exists. Tetrahydrobiopterin (BH4) is a cofactor for neuronal nitric oxide synthase. BH4 availability is reduced upon NOS activation, such as during hypoxic conditions, and leads to toxin production. We hypothesize that BH4 levels are depleted in the hypoxic brain and that BH4 replacement therapy mitigates the toxic effects of hypoxia on white matter. Methods and Results Transgenic mice were used to visualize oligodendrocytes. Hypoxia was introduced during a period of white matter development equivalent to the human third trimester. BH4 was administered during hypoxia. BH4 levels were depleted in the hypoxic brain by direct quantification (n=7-12). The proliferation (n=3-6), apoptosis (n=3-6), and developmental stage (n=5-8) of oligodendrocytes were determined immunohistologically. Total oligodendrocytes increased after hypoxia, consistent with hypoxia-induced proliferation seen previously; however, mature oligodendrocytes were less prevalent in hypoxia, and there was accumulation of immature oligodendrocytes. BH4 treatment improved the mature oligodendrocyte number such that it did not differ from normoxia, and accumulation of immature oligodendrocytes was not observed. These results persisted beyond the initial period of hypoxia (n=3-4). Apoptosis increased with hypoxia but decreased with BH4 treatment to normoxic levels. White matter myelin levels decreased following hypoxia by western blot. BH4 treatment normalized myelination (n=6-10). Hypoxia worsened sensory-motor coordination on balance beam tasks, and BH4 therapy normalized performance (n=5-9). Conclusions Suboptimal BH4 levels influence hypoxic white matter abnormalities. Repurposing BH4 for use during fetal brain development may limit white matter dysmaturation in congenital heart disease.

Missing in Action: Dysfunctional RNA Metabolism in Oligodendroglial Cells as a Contributor to Neurodegenerative Diseases?

The formation of myelin around axons by oligodendrocytes (OL) poses an enormous synthetic and energy challenge for the glial cell. Local translation of transcripts, including the mRNA for the essential myelin protein Myelin Basic Protein (MBP) at the site of myelin deposition has been recognised as an efficient mechanism to assure proper myelin sheath assembly. Oligodendroglial precursor cells (OPCs) form synapses with neurons and may localise many additional mRNAs in a similar fashion to synapses between neurons. In some diseases in which demyelination occurs, an abundance of OPCs is present but there is a failure to efficiently remyelinate and to synthesise MBP. This compromises axonal survival and function. OPCs are especially sensitive to cellular stress as occurring in neurodegenerative diseases, which can impinge on their ability to translate mRNAs into protein. Stress causes the build up of cytoplasmic stress granules (SG) in which many RNAs are sequestered and translationally stalled until the stress ceases. Chronic stress in particular could convert this initially protective reaction of the cell into damage, as persistence of SG may lead to pathological aggregate formation or long-term translation block of SG-associated RNAs. The recent recognition that many neurodegenerative diseases often exhibit an early white matter pathology with a proliferation of surviving OPCs, renders a study of the stress-associated processes in oligodendrocytes and OPCs especially relevant. Here, we discuss a potential dysfunction of RNA regulation in myelin diseases such as Multiple Sclerosis (MS) and Vanishing white matter disease (VWM) and potential contributions of OL dysfunction to neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD) and Fragile X syndrome (FXS).

Wharton's Jelly-Derived Mesenchymal Stem Cell Transplantation in a Patient with Hypoxic-Ischemic Encephalopathy: A Pilot Study

Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) have been introduced as a possible therapy in hypoxic-ischemic encephalopathy (HIE). We report a 16-year-old boy who was treated with WJ-MSCs in the course of HIE due to post-cardiopulmonary resuscitation. He received a long period of mechanical ventilation and tracheostomy with spastic quadriparesis. He underwent the intrathecal (1×10⁶/kg in 3 mL), intramuscular (1×10⁶/kg in 20 mL) and intravenous (1×10⁶/kg in 30 mL) administrations of WJ-MSCs for each application route (twice a month for 2 months). After stem cell infusions, progressive improvements were shown in his neurological examination, neuroradiological, and neurophysiological findings. To our best knowledge, this is a pioneer project to clinically study the neural repair effect of WJ-MSCs in a patient with HIE.

Environmental risk factors for autism: an evidence-based review of systematic reviews and meta-analyses

BACKGROUND

According to recent evidence, up to 40-50% of variance in autism spectrum disorder (ASD) liability might be determined by environmental factors. In the present paper, we conducted a review of systematic reviews and meta-analyses of environmental risk factors for ASD. We assessed each review for quality of evidence and provided a brief overview of putative mechanisms of environmental risk factors for ASD.

FINDINGS

Current evidence suggests that several environmental factors including vaccination, maternal smoking, thimerosal exposure, and most likely assisted reproductive technologies are unrelated to risk of ASD. On the contrary, advanced parental age is associated with higher risk of ASD. Birth complications that are associated with trauma or ischemia and hypoxia have also shown strong links to ASD, whereas other pregnancy-related factors such as maternal obesity, maternal diabetes, and caesarian section have shown a less strong (but significant) association with risk of ASD. The reviews on nutritional elements have been inconclusive about the detrimental effects of deficiency in folic acid and omega 3, but vitamin D seems to be deficient in patients with ASD. The studies on toxic elements have been largely limited by their design, but there is enough evidence for the association between some heavy metals (most important inorganic mercury and lead) and ASD that warrants further investigation. Mechanisms of the association between environmental factors and ASD are debated but might include non-causative association (including confounding), gene-related effect, oxidative stress, inflammation, hypoxia/ischemia, endocrine disruption, neurotransmitter alterations, and interference with signaling pathways.

CONCLUSIONS

Compared to genetic studies of ASD, studies of environmental risk factors are in their infancy and have significant methodological limitations. Future studies of ASD risk factors would benefit from a developmental psychopathology approach, prospective design, precise exposure measurement, reliable timing of exposure in relation to critical developmental periods and should take into account the dynamic interplay between gene and environment by using genetically informed designs.

Impaired Gas Exchange at Birth and Risk of Intellectual Disability and Autism: A Meta-analysis

We conducted meta-analyses of 67 studies on the association between neonatal proxies of impaired gas exchange and intellectual disability (ID) or autism spectrum disorders (ASD). Neonatal acidosis was associated with an odds ratio (OR) of 3.55 [95 % confidence interval (95 % CI) 2.23-5.49] for ID and an OR of 1.10 (95 % CI 0.91-1.31) for ASD. Children with a 5-min Apgar score of <7 had an OR of 5.39 (95 % CI 3.84-7.55) for ID and an OR of 1.67 (95 % CI 1.34-2.09) for ASD. O2 treatment was associated with an OR of 4.32 (95 % CI 3.23-5.78) for ID and an OR of 2.02 (95 % CI 1.45 to 2.83) for ASD. Our meta-analysis demonstrates an increased risk of ID and (to a lesser extent) ASD in children with neonatal hypoxia. Moreover, our findings raise the possibility that concomitant ID might account for the observed association between the gas exchange proxies and ASD.

Diffusion Tensor Imaging Abnormalities in the Cerebral White Matter Correlate with Sex-Dependent Neurobehavioral Deficits in Adult Mice with Neonatal Ischemia

BACKGROUND

Neonatal white matter injury (NWMI) is the leading cause of cerebral palsy in prematurely born children. In order to develop a test bed for therapeutics, we recently reported a mouse model of NWMI by using a modified Rice-Vannucci model of neonatal ischemia on postnatal day 5 (P5) in CD-1 mice. We have previously shown that these mice illustrate initial neuroinflammation and oligodendroglial differentiation arrest followed by long-term dysmyelination, periventricular astrogliosis and axonal injury, resembling human NWMI. The objective of this study was to determine the sex-dependent long-term effects of neonatal brain injury on neurobehavioral and advanced in vivo neuroimaging indices in this mouse model, and to correlate these variables with histopathology.

METHODS

After right common artery ligation on P5, in vivo T2-weighted imaging and diffusion tensor imaging (DTI) were performed on ligated and control animals at 4 and 8 weeks. Common sets of regions of interest were used to compare fractional anisotropy (FA) values between ischemic and control mice. Behavioral testing (open field, startle response and grip strength) was performed at adult age. Finally, the animals were sacrificed for immunohistochemical (IHC) assessment of major white matter tracts.

RESULTS

DTI revealed significant sex-dependent changes in FA values ipsi- and contralateral to the ligation. Behavioral testing showed decreased reaction to acoustic stimuli in males but not females. Similarly, increased number of rearings and lack of novelty-induced habituation in the open field were encountered only in the male subgroup. Several regional correlations were found between FA values and these behavioral alterations. IHC studies revealed degeneration of mature oligodendrocytes and damage of white matter tracts in ligated animals, as previously reported in this model, and showed regional correlation with in vivo FA values and behavioral alterations.

CONCLUSIONS

Our findings suggest structural sex-dependent long-term abnormalities after neonatal ischemia. These changes lead to behavioral deficits resembling common problems of patients with cerebral palsy.

Transplantation of placenta-derived mesenchymal stem cells reduces hypoxic-ischemic brain damage in rats by ameliorating the inflammatory response

Hypoxic-ischemic brain damage (HIBD) is a common cause of infant death. The purpose of our research was to explore the immunoregulatory mechanism of placenta-derived mesenchymal stem cells (PD-MSCs) in HIBD treatment. Seven-day-old rat pups were randomly divided into HIBD, PD-MSC, fibroblast, and control groups. Forty-eight hours after HIBD induction, cells at a density of 5 × 104 cells/10 µl were injected into the cerebral tissue in the PD-MSC and fibroblast groups. The TNF-α, interleukin- 17 (IL-17), interferon-γ (IFN-γ), and IL-10 levels were detected through quantitative real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Regulatory T cell (Tregs) populations were detected through flow cytometry, and forkhead box P3 (Foxp3) was measured through western blot analysis. Behavioral tests and gross and pathological examinations showed that PD-MSC treatment exerted significantly stronger neuroprotective effects than the other treatments. The expression levels of pro-inflammatory cytokines were substantially upregulated after HI injury. Compared with fibroblast treatment, PD-MSC treatment inhibited the production of pro-inflammatory cytokines and increased the production of IL-10 in the ischemic hemispheres and peripheral blood serum (all P < 0.01). Flow cytometry results showed a notable increase in the number of Tregs within the spleen of the HIBD group. Moreover, the number of Tregs and the Foxp3 expression levels were higher in the PD-MSC treatment group than in the HIBD and fibroblast groups (all P < 0.01). Our research suggests that the mechanism of PD-MSC treatment for HIBD partially involves inflammatory response suppression.

Sex differences in cell genesis, hippocampal volume and behavioral outcomes in a rat model of neonatal HI

Hypoxia-ischemia (HI) of the brain in near-term and term infants is a leading cause of infant mortality and lifelong disability but current therapeutic approaches remain limited. Males consistently display greater vulnerability to the deleterious consequences of HI in both humans and animal models. Neurogenesis increases after neonatal HI and offers a potential therapeutic target for recovery. The steroid hormone estradiol has been extensively explored as a neuroprotectant in adult models of stroke but with mixed results. Less consideration has been afforded to this naturally occurring agent in the developing brain, which has unique challenges from the adult. Using a model of term HI in the rat we have explored the impact of this insult on cell genesis in the hippocampus of males and females and the ability of estradiol treatment immediately after insult to restore function. Both short-term (3 days) and long-term (7 days) post-injury were assessed and revealed that only females had markedly increased cell genesis on the short-term but both sexes were increased long-term. A battery of behavioral tests revealed motor impairment in males and compromised episodic memory while both sexes were modestly impaired in spatial memory. Juvenile social play was also depressed in both sexes after HI. Estradiol therapy improved behavioral performance in both sexes but did not reverse a deficit in hippocampal volume ipsilateral to the insult. Thus the effects of estradiol do not appear to be via cell death or proliferation but rather involve other components of neural functioning.

Mechanisms underlying presynaptic Ca2+ transient and vesicular glutamate release at a CNS nerve terminal during in vitro ischaemia

KEY POINTS

Here we demonstrate presynaptic responses and mechanisms of increased vesicular glutamate release during in vitro ischaemia in the calyx of Held terminal, an experimentally accessible presynaptic terminal in the CNS. The ischaemia-induced increase in presynaptic Ca(2+) was mediated by both Ca(2+) influx and Ca(2+) -induced Ca(2+) release from intracellular stores. The reverse operation of the plasma membrane Na(+) /Ca(2+) exchanger (NCX) plays a key role in Ca(2+) influx for triggering Ca(2+) release from intracellular stores at presynaptic terminals during in vitro ischaemia. Ca(2+) uptake via NCX underlies the ischaemia-induced Ca(2+) rise and the consequent increase in vesicular glutamate release from presynaptic terminals in the early phase of brain ischaemia.

ABSTRACT

An early consequence of brain ischaemia is an increase in vesicular glutamate release from presynaptic terminals. However, the mechanisms of this increased glutamate release are not fully understood. Here we studied presynaptic responses and mechanisms of increased glutamate release during in vitro ischaemia, using pre- and postsynaptic whole-cell recordings and presynaptic Ca(2+) imaging at the calyx of Held synapse in rat brainstem slices. Consistent with results from other brain regions, in vitro ischaemia significantly increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) without affecting their amplitude, suggesting that ischaemia enhances vesicular glutamate release from presynaptic terminals. We found that ischaemia-induced vesicular glutamate release was dependent on a rise in basal Ca(2+) at presynaptic terminals, which resulted from extracellular Ca(2+) influx and Ca(2+) release from intracellular stores. During early ischaemia, increased Ca(2+) influx into presynaptic terminals was due to reverse operation of the plasma membrane Na(+) /Ca(2+) exchanger (NCX) rather than presynaptic depolarization or voltage-activated Ca(2+) currents. KB-R7943, an inhibitor of NCX, prevented the ischaemia-induced increases in presynaptic Ca(2+) and vesicular glutamate release. In addition, the removal of extracellular Na(+) completely inhibited the ischaemia-induced Ca(2+) rise. It therefore appears that a link between Na(+) accumulation and Ca(2+) uptake via NCX underlies the ischaemia-induced Ca(2+) rise and the consequent increase in vesicular glutamate release from presynaptic terminals in the early phase of brain ischaemia.

Neuroprotective effect of human placental extract on hypoxic-ischemic brain injury in neonatal rats

We investigated the neuroprotective effects of human placental extracts (HPE) and the effects of HPE on recovery of cognitive and behavioral function on hypoxic-ischemic brain injury in the newborn rat. The right common carotid arteries of 7-day-old rats were coagulated, and rats were then exposed to 8% oxygen. Immediately before and again at three times after the hypoxia-ischemia (pre-treatment group), and immediately after and three times again after hypoxia-ischemia (post-treatment group), the rats were intraperitoneally injected with HPE (0.1, 0.25, or 0.5 mL/10 g/dose). No-treatment rats received saline only. On postnatal day 12, brains were removed and gross morphological damage was evaluated. To quantify the severity of brain injury, bilateral cross-sectional areas of the anterior commissural and posterior hippocampal levels were analyzed with NIH Image. Assessments of the open field activity levels at 2, 4, 6 and 8 week and, the Morris water maze test at 8 weeks after hypoxia-ischemia were carried out according to standard methods. HPE pre-treatment decreased the incidence of liquefactive cerebral infarction, at an optimally neuroprotective dose of 0.5 mL/10 g/dose (P<0.05). In the Morris water maze test, the group injected with HPE at 0.5 mL/10 g/dose concentration showed shorter escape latencies than the no-treatment group (P<0.05). These findings support a protective effect of the HPE treatment on neuronal integrity and cognitive function following hypoxic-ischemic brain injury. Injected at an appropriate dose prior to exposure, HPE may significantly reduce or prevent hypoxic-ischemic injury in the immature brain.

Pharmacological neuroprotection after perinatal hypoxic-ischemic brain injury

Perinatal hypoxia-ischemia (HI) is an important cause of neonatal brain injury. Recent progress in the search for neuroprotective compounds has provided us with several promising drugs to reduce perinatal HI-induced brain injury. In the early stage (first 6 hours after birth) therapies are concentrated on prevention of the production of reactive oxygen species or free radicals (xanthine-oxidase-, nitric oxide synthase-, and prostaglandin inhibition), anti-inflammatory effects (erythropoietin, melatonin, Xenon) and anti-apoptotic interventions (nuclear factor kappa B- and c-jun N-terminal kinase inhibition); in a later stage stimulation of neurotrophic properties in the neonatal brain (erythropoietin, growth factors) can be targeted to promote neuronal and oligodendrocyte regeneration. Combination of pharmacological means of treatment with moderate hypothermia, which is accepted now as a meaningful therapy, is probably the next step in clinical treatment to fight post-asphyxial brain damage. Further studies should be directed at a more rational use of therapies by determining the optimal time and dose to inhibit the different potentially destructive molecular pathways or to enhance endogenous repair while at the same time avoiding adverse effects of the drugs used.

Actualities on molecular pathogenesis and repairing processes of cerebral damage in perinatal hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is the most important cause of cerebral damage and long-term neurological sequelae in the perinatal period both in term and preterm infant.

Hypoxic-ischemic (H-I) injuries develop in two phases: the ischemic phase, dominated by necrotic processes, and the reperfusion phase, dominated by apoptotic processes extending beyond ischemic areas. Due to selective ischemic vulnerability, cerebral damage affects gray matter in term newborns and white matter in preterm newborns with the typical neuropathological aspects of laminar cortical necrosis in the former and periventricular leukomalacia in the latter.

This article summarises the principal physiopathological and biochemical processes leading to necrosis and/or apoptosis of neuronal and glial cells and reports recent insights into some endogenous and exogenous cellular and molecular mechanisms aimed at repairing H-I cerebral damage.