Imaging selective vulnerability in the developing nervous system

Brain Damage in Preterm and Full-Term Neonates: Serum Biomarkers for the Early Diagnosis and Intervention

The Brain is vulnerable to numerous insults that can act in the pre-, peri-, and post-natal period. There is growing evidence that demonstrate how oxidative stress (OS) could represent the final common pathway of all these insults. Fetuses and newborns are particularly vulnerable to OS due to their inability to active the antioxidant defenses. Specific molecules involved in OS could be measured in biologic fluids as early biomarkers of neonatal brain injury with an essential role in neuroprotection. Although S-100B seems to be the most studied biomarker, its use in clinical practice is limited by the complexity of brain damage etiopathogenesis and the time of blood sampling in relation to the brain injury. Reliable early specific serum markers are currently lacking in clinical practice. It is essential to determine if there are specific biomarkers that can help caregivers to monitor the progression of the disease in order to active an early neuroprotective strategy. We aimed to describe, in an educational review, the actual evidence on serum biomarkers for the early identification of newborns at a high risk of neurological diseases. To move the biomarkers from the bench to the bedside, the assays must be not only be of a high sensitivity but suitable for the very rapid processing and return of the results for the clinical practice to act on. For the best prognosis, more studies should focus on the association of these biomarkers to the type and severity of perinatal brain damage.

Role of Vitamin E in Neonatal Neuroprotection: A Comprehensive Narrative Review

Vitamin E (Vit E) is an essential lipophilic antioxidant and anti-inflammatory agent that has potential as a neuroprotectant in newborn infants with brain injury. Vit E has shown promise in many in vitro studies, but success in translation to in vivo animal studies and the clinical setting has been mixed, with concern of adverse effects at high intravenous doses in preterm infants. However, a recent rise in knowledge of the beneficial effects of fat emulsions containing higher levels of Vit E, along with associated improved outcomes in some neonatal co-morbidities, has led many to reconsider Vit E administration as a potential therapeutic modality to improve neurological outcomes in the setting of neonatal brain injury. This narrative review discusses Vit E's structure, mechanism(s) of action, evidence in animal models, and association with health outcomes in neonates, including both dietary and supplemental Vit E and their bioavailability and pharmacokinetics as it relates to the brain. Lastly, long-term neurodevelopmental outcomes along with gaps in current knowledge are critiqued, which to date suggests that additional translational studies in larger animal models and assessment of safety profiles of different routes and doses of administration should be explored prior to large clinical trials. Importantly, a greater understanding of the brain region(s) and cell type(s) affected by Vit E may help to target the use of Vit E as a beneficial neuroprotective agent to specific populations or types of injury seen in newborns.

Time Course of Changes in the Neurovascular Unit after Hypoxic-Ischemic Injury in Neonatal Rats

Exposure to hypoxic-ischemic (HI) insults in newborns can predispose them to severe neurological sequela. The mechanisms underlying HI-related brain injury have not been completely elucidated. The neurovascular unit (NVU) is a composite of structures that protect the brain from the influx of detrimental molecules. Changes in the NVU after HI are important because they could reveal endogenous neuroprotective pathways in the cerebral microvasculature. Furthermore, the time course of changes in the NVU after exposure to HI in the newborn remains to be determined. In this study, we examined the effects of severe HI on the time course of changes in the NVU in neonatal rats. Brains were collected from rats exposed to right carotid artery ligation and 2 h of hypoxia on postnatal day 7 with recovery for 6 or 48 h after exposure to sham treatment (Sham) or HI. The right HI and left hypoxic alone sides of the brains were examined by quantitative immunohistochemistry for vascular density (laminin), pericyte vascular coverage (PDGFRβ), astrocyte vascular coverage (GFAP), and claudin-5 expression in the microvasculature of the cerebral cortex, white matter, and hippocampus. HI-related brain injury in neonatal rats was associated with increases in vascular density in the cortex and hippocampus 48 h after HI as well as neurovascular remodeling, including loss of pericyte coverage in the cortex and increases in claudin-5 in the hippocampus 6 h after HI. Astrocyte coverage was not affected by HI injury. The time course of the responses in the different components of the NVU varied after exposure to HI. There were also differential regional responses in the elements of the NVU in response to HI and hypoxia alone.

White matter alterations and cognitive outcomes in children born very low birth weight

BACKGROUND

Very low birth weight (VLBW) infants are at risk for disrupted white matter maturation, yet little is known about the contributing factors, particularly at preschool-age when cognitive difficulties begin to emerge. We examined white matter microstructure in five-year-old VLBW and full-term (FT) children, and its association with cognitive outcomes and birth weight.

METHODS

Multi-shell diffusion and MR images were obtained for 41 VLBW (mean birth weight: 1028.6 ± 256.8 g) and 26 FT (3295.4 ± 493.9 g) children. Fractional anisotropy (FA), radial diffusivity (RD), neurite orientation dispersion index (ODI) and density index (NDI) were estimated using diffusion tensor and neurite orientation dispersion and density imaging models. Between-group analyses used a general linear model with group and sex as explanatory variables. Within-group associations between white matter microstructure, cognitive outcomes and birth weight were also investigated.

RESULTS

VLBW compared to FT children showed lower FA and NDI across widespread white matter regions. Smaller clusters of atypical ODI were also found in VLBW children. Within-group analyses in FT children revealed that lower RD and higher NDI were associated with vocabulary acquisition and working memory. In VLBW children, higher FA and NDI, and lower RD and ODI, were associated with improved processing speed. In both groups, FA was positively associated with birth weight.

CONCLUSIONS

Our findings demonstrate white matter alterations in young VLBW children, including widespread reductions in axon density that may reflect sustained myelination disruptions. The associations with cognitive outcomes may also highlight which of the VLBW children are at higher risk for later cognitive difficulties.

Comparison of fractional anisotropy and apparent diffusion coefficient among hypoxic ischemic encephalopathy stages 1, 2, and 3 and with nonasphyxiated newborns in 18 areas of brain

Purpose

To determine the area and extent of injury in hypoxic encephalopathy stages by diffusion tensor imaging (DTI) using parameters apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values and their comparison with controls without any evidence of asphyxia. To correlate the outcome of hypoxia severity clinically and significant changes on DTI parameter.

Materials and Methods

DTI was done in 50 cases at median age of 12 and 20 controls at median age of 7 days. FA and apparent diffusion coefficient (ADC) were measured in several regions of interest (ROI). Continuous variables were analyzed using Student's t-test. Categorical variables were compared by Fisher's exact test. Comparison among multiple groups was done using analysis of variance (ANOVA) and post hoc Bonferroni test.

Results

Abnormalities were more easily and accurately determined in ROI with the help of FA and ADC values. When compared with controls FA values were significantly decreased and ADC values were significantly increased in cases, in ROI including both right and left side of thalamus, basal ganglia, posterior limb of internal capsule, cerebral peduncle, corticospinal tracts, frontal, parietal, temporal, occipital with P value < 0.05. The extent of injury was maximum in stage-III. There was no significant difference among males and females.

Conclusion

Compared to conventional magnetic resonance imaging (MRI), the evaluation of FA and ADC values using DTI can determine the extent and severity of injury in hypoxic encephalopathy. It can be used for early determination of brain injury in these patients.

Hypoxic-ischemic injury causes functional and structural neurovascular degeneration in the juvenile mouse retina

Ischemic stroke is a major cause of long-term disabilities, including vision loss. Neuronal and blood vessel maturation can affect the susceptibility of and outcome after ischemic stroke. Although we recently reported that exposure of neonatal mice to hypoxia–ischemia (HI) severely compromises the integrity of the retinal neurovasculature, it is not known whether juvenile mice are similarly impacted. Here we examined the effect of HI injury in juvenile mice on retinal structure and function, in particular the susceptibility of retinal neurons and blood vessels to HI damage. Our studies demonstrated that the retina suffered from functional and structural injuries, including reduced b-wave, thinning of the inner retinal layers, macroglial remodeling, and deterioration of the vasculature. The degeneration of the retinal vasculature associated with HI resulted in a significant decrease in the numbers of pericytes and endothelial cells as well as an increase in capillary loss. Taken together, these findings suggest a need for juveniles suffering from ischemic stroke to be monitored for changes in retinal functional and structural integrity. Thus, there is an emergent need for developing therapeutic approaches to prevent and reverse retinal neurovascular dysfunction with exposure to ischemic stroke.

Early nutrition and white matter microstructure in children born very low birth weight

Infants born at very low birth weight (<1500 g) are vulnerable to nutritional deficits during their first postnatal month, which are associated with poor neurodevelopmental outcomes. Despite this knowledge, the impact of early postnatal nutrition on white matter microstructure in children born with very low birth weight has not been investigated. In this prospective cohort study, we employed a whole-brain approach to investigate associations between precise estimates of nutrient intake within the first postnatal month with white matter microstructure at 5 years of age. Detailed information about breastmilk, macronutrient and energy intakes during this period were prospectively recorded for all participants. Multi-shell diffusion and T₁-weighted MRIs were acquired in 41 children (21 males; mean scan age: 5.75 ± 0.22 years; mean birth weight: 1028.6 ± 256.8 g). The diffusion tensor imaging and neurite orientation dispersion and density imaging models were used to obtain maps of fractional anisotropy, radial diffusivity, orientation dispersion and neurite density indices. Tract-based spatial statistics was used to test associations between metrics of white matter microstructure with breastmilk, macronutrient (protein, lipids and carbohydrate) and energy intake. Associations between white matter microstructure and cognitive outcomes were also examined. Compared to children who did not meet enteral feeding recommendations, those who achieved enteral protein, lipid and energy recommendations during the first postnatal month showed improved white matter maturation at 5 years. Among the macronutrients, greater protein intake contributed most to the beneficial effect of nutrition, showing widespread increases in fractional anisotropy and reductions in radial diffusivity. No significant associations were found between white matter metrics with breastmilk or carbohydrate intake. Voxel-wise analyses with cognitive outcomes revealed significant associations between higher fractional anisotropy and neurite density index with higher processing speed scores. Lower radial diffusivity and orientation dispersion index were also associated with improved processing speed. Our findings support the long-term impacts of early nutrition on white matter microstructure, which in turn is related to cognitive outcomes. These results provide strong support for early postnatal nutritional intervention as a promising strategy to improve long-term cognitive outcomes of infants born at very low birth weight.

Isoprostanes as Biomarker for White Matter Injury in Extremely Preterm Infants

Background and Aim: Preterm white matter is vulnerable to lipid peroxidation-mediated injury. F2-isoprostanes (IPs), are a useful biomarker for lipid peroxidation. Aim was to assess the association between early peri-postnatal IPs, white matter injury (WMI) at term equivalent age (TEA), and neurodevelopmental outcome in preterm infants. Methods: Infants with a gestational age (GA) below 28 weeks who had an MRI at TEA were included. IPs were measured in cord blood (cb) at birth and on plasma (pl) between 24 and 48 h after birth. WMI was assessed using Woodward MRI scoring system. Multiple regression analyses were performed to assess the association between IPs with WMI and then with BSITD-III scores at 24 months corrected age (CA). Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive value of pl-IPs for the development of WMI. Results: Forty-four patients were included. cb-IPs were not correlated with WMI score at TEA, whereas higher pl-IPs and lower GA predicted higher WMI score (p = 0.037 and 0.006, respectively) after controlling for GA, FiO2 at sampling and severity of IVH. The area under the curve was 0.72 (CI 95% = 0.51-0.92). The pl-IPs levels plotted curve indicated that 31.8 pg/ml had the best predictive threshold with a sensitivity of 86% and a specificity of 60%, to discriminate newborns with any WMI from newborns without WMI. IPs were not associated with outcome at 24 months. Conclusion: Early measurement of pl-IPs may help discriminate patients showing abnormal WMI score at TEA, thus representing an early biomarker to identify newborns at risk for brain injury.

Neuroprotective effects of a dendrimer-based glutamate carboxypeptidase inhibitor on superoxide dismutase transgenic mice after neonatal hypoxic-ischemic brain injury

The result of a deprivation of oxygen and glucose to the brain, hypoxic-ischemic encephalopathy (HIE), remains the most common cause of death and disability in human neonates globally and is mediated by glutamate toxicity and inflammation. We have previously shown that the enzyme glutamate carboxypeptidase (GCPII) is overexpressed in activated microglia in the presence of inflammation in fetal/newborn rabbit brain. We assessed the therapeutic utility of a GCPII enzyme inhibitor called 2-(3-Mercaptopropyl) pentanedioic acid (2MPPA) attached to a dendrimer (D-2MPPA), in order to target activated microglia in an experimental neonatal hypoxia-ischemia (HI) model using superoxide dismutase transgenic (SOD) mice that are often more injured after hypoxia-ischemia than wildtype animals. SOD overexpressing and wild type (WT) mice underwent permanent ligation of the left common carotid artery followed by 50 min of asphyxiation (10% O₂) to induce HI injury on postnatal day 9 (P9). Cy5-labeled dendrimers were administered to the mice at 6 h, 24 h or 72 h after HI and brains were evaluated by immunofluorescence analysis 24 h after the injection to visualize microglial localization and uptake over time. Expression of GCPII enzyme was analyzed in microglia 24 h after the HI injury. The expression of pro- and anti-inflammatory cytokines were analyzed 24 h and 72 h post-HI. Brain damage was analyzed histologically 7 days post-HI in the three randomly assigned groups: control (C); hypoxic-ischemic (HI); and HI mice who received a single dose of D-2MPPA 6 h post-HI (HI+D-2MPPA). First, we found that GCPII was overexpressed in activated microglia 24 h after HI in the SOD overexpressing mice. Also, there was an increase in microglial activation 24 h after HI in the ipsilateral hippocampus which was most visible in the SOD+HI group. Dendrimers were mostly taken up by microglia by 24 h post-HI; uptake was more prominent in the SOD+HI mice than in the WT+HI. The inflammatory profile showed significant increase in expression of KC/GRO following injury in SOD mice compared to WT at 24 and 72 h. A greater and significant decrease in KC/GRO was seen in the SOD mice following treatment with D-2MPPA. Seven days after HI, D-2MPPA treatment decreased brain injury in the SOD+HI group, but not in WT+HI. This reduced damage was mainly seen in hippocampus and cortex. Our data indicate that the best time point to administer D-2MPPA is 6 h post-HI in order to suppress the expression of GCPII by 24 h after the damage since dendrimer localization in microglia is seen as early as 6 h with the peak of GCPII upregulation in activated microglia seen at 24 h post-HI. Ultimately, treatment with D-2MPPA at 6 h post-HI leads to a decrease in inflammatory profiles by 24 h and reduction in brain injury in the SOD overexpressing mice.

More than meets the eye: Longitudinal visual system neurodevelopment in very preterm children and anophthalmia

Anophthalmia, characterized by the absence of an eye(s), is a rare major birth defect with a relatively unexplored neuroanatomy. Longitudinal comparison of white matter development in an anophthalmic (AC) very preterm (VPT) child with both binocular VPT and full-term (FT) children provides unique insights into early neurodevelopment of the visual system. VPT-born neonates (<32wks gestational age), including the infant with unilateral anophthalmia, underwent neuroimaging every two years from birth until 8 years. DTI images (N = 168) of the optic radiation (OR) and a control track, the posterior limb of the internal capsule (PLIC), were analysed. The diameter of the optic nerves (ON) were analysed using T1-weighted images. Significant group differences in FA and AD were found bilaterally in the OR and PLIC. This extends the literature on altered white matter development in VPT children, being the first longitudinal study showing stable group differences across the 4, 6 and 8 year timepoints. AC showed greater deficits in FA and AD bilaterally, but recovered towards VPT group means from 4 to 8 years-of-age. Complete lack of binocular input would be responsible for these early deficits; compensatory mechanisms may facilitate structural improvement over time. AC's ON exhibited significant atrophy ipsilateral to the anophthalmic eye. Functionally, AC displayed normal visual acuity and form perception, but naso-temporal bias in motion perception. Following these groups and AC longitudinally enabled novel understanding of the joint influence of monocular vision and VPT birth on neurodevelopment.

Clinical characteristics of children and adults with anti-N-methyl-D-aspartate receptor encephalitis

OBJECTIVES

To investigate the clinical characteristics of children and adults with anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis.

METHODS

Patients who tested positive for the anti-NMDAR antibody (by a cell-based assay) in the cerebrospinal fluid were enrolled. They were divided into two groups based on age (<16 years or older).

RESULTS

Three children (two males and one female) and four adults (one male and three females) were examined. The age at onset was 3.0 ± 1.41 years (range: 2-5 years) for the children and 31.8 ± 6.80 years (range: 20-36 years) for the adults. The follow-up duration was 82.7 ± 23.80 months (range: 52-110 months) for the children and 61.5 ± 12.54 months (range: 43-78 months) for the adults. Prodromal symptoms such as fever and headache were observed in three adults. Two children received influenza vaccination before the onset of encephalitis. Brain magnetic resonance imaging abnormalities were observed in three children and one adult. Basal ganglia lesions were observed in two children and one adult, and the two children showed dystonia. Two children and one adult without neoplasms experienced recurrences. The modified Rankin Scale scores at the final follow-up tended to be worse in children than in adults.

CONCLUSION

Three patients had basal ganglia lesions, and two of them showed dystonia. Dystonia with basal ganglia lesions has been rarely reported in anti-NMDAR encephalitis but should be noted as a significant symptom, which severely affects the activities of daily life.

cGAS/STING Pathway Activation Contributes to Delayed Neurodegeneration in Neonatal Hypoxia-Ischemia Rat Model: Possible Involvement of LINE-1

cGAS is a sensor of cytosolic DNA and responds equally to exogenous and endogenous DNA. After recognition of cytosolic dsDNA or ssDNA, cGAS synthesizes the second messenger 2'3'-cGAMP, which then binds to and activates stimulator of interferon genes (STING). STING plays an essential role in responding to pathogenic DNA and self-DNA in the context of autoimmunity. In pathologic conditions, such as stroke or hypoxia-ischemia (HI), DNA can gain access into the cytoplasm of the cell and leak from the dying cells into the extracellular environment, which potentially activates cGAS/STING. Recent in vivo studies of myocardial ischemia, traumatic brain injury, and liver damage models suggest that activation of cGAS/STING is not only a side-effect of the injury, but it can also actively contribute to cell death and apoptosis. We found, for the first time, that cGAS/STING pathway becomes activated between 24 and 48 h after HI in a 10-day-old rat model. Silencing STING with siRNA resulted in decreased infarction area, reduced cortical neurodegeneration, and improved neurobehavior at 48 h, suggesting that STING can contribute to injury progression after HI. STING colocalized with lysosomal marker LAMP-1 and blocking STING reduced the expression of cathepsin B and decreased the expression of Bax and caspase 3 cleavage. We observed similar protective effects after intranasal treatment with cGAS inhibitor RU.521, which were reversed by administration of STING agonist 2'3'-cGAMP. Additionally, we showed that long interspersed element 1 (LINE-1) retrotransposon, a potential upstream activator of cGAS/STING pathway was induced at 48 h after HI, which was evidenced by increased expression of ORF1p and ORF2p proteins and increased LINE-1 DNA content in the cytosol. Blocking LINE-1 with the nucleoside analog reverse-transcriptase inhibitor (NRTI) stavudine reduced infarction area, neuronal degeneration in the cerebral cortex, and reduced the expression of Bax and cleaved caspase 3. Thus, our results identify the cGAS/STING pathway as a potential therapeutic target to inhibit delayed neuronal death after HI.

Individual differences of maladaptive brain changes in migraine and their relationship with differential effectiveness of treatments

Migraine is a difficult disorder to identify with regard to its pathophysiological mechanisms, and its treatment has been primarily difficult owing to interindividual differences. Substantial rates of nonresponsiveness to medications are common, making migraine treatment complicated. In this review, we systematically analyzed recent studies concerning neuroimaging findings regarding the neurophysiology of migraine. We linked the current imaging research with anecdotal evidence from interindividual factors such as duration and pain intensity of migraine, age, gender, hormonal interplay, and genetics. These factors suggested the use of nonpharmacological therapies such as transcranial magnetic stimulation, transcranial direct current stimulation, and placebo therapy for the treatment of migraine. Finally, we discussed how interindividual differences are related to such nondrug treatments.

Advanced nanotherapies to promote neuroregeneration in the injured newborn brain

Neonatal brain injury affects thousands of babies each year and may lead to long-term and permanent physical and neurological problems. Currently, therapeutic hypothermia is standard clinical care for term newborns with moderate to severe neonatal encephalopathy. Nevertheless, it is not completely protective, and additional strategies to restore and promote regeneration are urgently needed. One way to ensure recovery following injury to the immature brain is to augment endogenous regenerative pathways. However, novel strategies such as stem cell therapy, gene therapies and nanotechnology have not been adequately explored in this unique age group. In this perspective review, we describe current efforts that promote neuroprotection and potential targets that are unique to the developing brain, which can be leveraged to facilitate neuroregeneration.

Assessing Cerebral Metabolism in the Immature Rodent: From Extracts to Real-Time Assessments

Brain development is an energy-expensive process. Although glucose is irreplaceable, the developing brain utilizes a variety of substrates such as lactate and the ketone bodies, β-hydroxybutyrate and acetoacetate, to produce energy and synthesize the structural components necessary for cerebral maturation. When oxygen and nutrient supplies to the brain are restricted, as in neonatal hypoxia-ischemia (HI), cerebral energy metabolism undergoes alterations in substrate use to preserve the production of adenosine triphosphate. These changes have been studied by in situ biochemical methods that yielded valuable quantitative information about high-energy and glycolytic metabolites and established a temporal profile of the cerebral metabolic response to hypoxia and HI. However, these analyses relied on terminal experiments and averaging values from several animals at each time point as well as challenging requirements for accurate tissue processing.More recent methodologies have focused on in vivo longitudinal analyses in individual animals. The emerging field of metabolomics provides a new investigative tool for studying cerebral metabolism. Magnetic resonance spectroscopy (MRS) has enabled the acquisition of a snapshot of the metabolic status of the brain as quantifiable spectra of various intracellular metabolites. Proton (1H) MRS has been used extensively as an experimental and diagnostic tool of HI in the pursuit of markers of long-term neurodevelopmental outcomes. Still, the interpretation of the metabolite spectra acquired with 1H MRS has proven challenging, due to discrepancies among studies, regarding calculations and timing of measurements. As a result, the predictive utility of such studies is not clear. 13C MRS is methodologically more challenging, but it provides a unique window on living tissue metabolism via measurements of the incorporation of 13C label from substrates into brain metabolites and the localized determination of various metabolic fluxes. The newly developed hyperpolarized 13C MRS is an exciting method for assessing cerebral metabolism in vivo, that bears the advantages of conventional 13C MRS but with a huge gain in signal intensity and much shorter acquisition times. The first part of this review article provides a brief description of the findings of biochemical and imaging methods over the years as well as a discussion of their associated strengths and pitfalls. The second part summarizes the current knowledge on cerebral metabolism during development and HI brain injury.

Role of PPAR-β/δ/miR-17/TXNIP pathway in neuronal apoptosis after neonatal hypoxic-ischemic injury in rats

Activation of peroxisome proliferator-activated receptor beta/delta (PPAR-β/δ), a nuclear receptor acting as a transcription factor, was shown to be protective in various models of neurological diseases. However, there is no information about the role of PPAR-β/δ as well as its molecular mechanisms in neonatal hypoxia-ischemia (HI). In the present study, we hypothesized that PPAR-β/δ agonist GW0742 can activate miR-17-5p, consequently inhibiting TXNIP and ASK1/p38 pathway leading to attenuation of apoptosis. Ten-day-old rat pups were subjected to right common carotid artery ligation followed by 2.5 h hypoxia. GW0742 was administered intranasally 1 and 24 h post HI. PPAR-β/δ receptor antagonist GSK3787 was administered intranasally 1 h before and 24 h after HI, antimir-17-5p and TXNIP CRISPR activation plasmid were administered intracerebroventricularly 24 and 48 h before HI, respectively. Brain infarct area measurement, neurological function tests, western blot, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), Fluoro-Jade C and immunofluorescence staining were conducted. GW0742 reduced brain infarct area, brain atrophy, apoptosis, and improved neurological function at 72 h and 4 weeks post HI. Furthermore, GW0742 treatment increased PPAR-β/δ nuclear expression and miR-17-5p level and reduced TXNIP in ipsilateral hemisphere after HI, resulting in inhibition of ASK1/p38 pathway and attenuation of apoptosis. Inhibition of PPAR-β/δ receptor and miR-17-5p and activation of TXNIP reversed the protective effects. For the first time, we provide evidence that intranasal administration of PPAR-β/δ agonist GW0742 attenuated neuronal apoptosis at least in part via PPAR-β/δ/miR-17/TXNIP pathway. GW0742 could represent a therapeutic target for treatment of neonatal hypoxic ischemic encephalopathy (HIE).

Paraquat and Maneb Exposure Alters Rat Neural Stem Cell Proliferation by Inducing Oxidative Stress: New Insights on Pesticide-Induced Neurodevelopmental Toxicity

Pesticide exposure has been linked to the pathogenesis of neurodevelopmental and neurodegenerative disorders including autism spectrum disorders, attention deficit/hyperactivity, and Parkinson's disease (PD). Developmental exposure to pesticides, even at low concentrations not harmful for the adult brain, can lead to neuronal loss and functional deficits. It has been shown that prenatal or early postnatal exposure to the herbicide paraquat (PQ) and the fungicide maneb (MB), alone or in combination, causes permanent toxicity in the nigrostriatal dopamine system, supporting the idea that early exposure to these pesticides may contribute to the pathophysiology of PD. However, the mechanisms mediating PQ and MB developmental neurotoxicity are not yet understood. Therefore, we investigated the neurotoxic effect of low concentrations of PQ and MB in primary cultures of rat embryonic neural stem cells (NSCs), with particular focus on cell proliferation and oxidative stress. Exposure to PQ alone or in combination with MB (PQ + MB) led to a significant decrease in cell proliferation, while the cell death rate was not affected. Consistently, PQ + MB exposure altered the expression of major genes regulating the cell cycle, namely cyclin D1, cyclin D2, Rb1, and p19. Moreover, PQ and PQ + MB exposures increased the reactive oxygen species (ROS) production that could be neutralized upon N-acetylcysteine (NAC) treatment. Notably, in the presence of NAC, Rb1 expression was normalized and a normal cell proliferation pattern could be restored. These findings suggest that exposure to PQ + MB impairs NSCs proliferation by mechanisms involving alterations in the redox state.

Longitudinal Study of White Matter Development and Outcomes in Children Born Very Preterm

Identifying trajectories of early white matter development is important for understanding atypical brain development and impaired functional outcomes in children born very preterm (<32 weeks gestational age [GA]). In this study, 161 diffusion images were acquired in children born very preterm (median GA: 29 weeks) shortly following birth (75), term-equivalent (39), 2 years (18), and 4 years of age (29). Diffusion tensors were computed to obtain measures of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), which were aligned and averaged. A paediatric atlas was applied to obtain diffusion metrics within 12 white matter tracts. Developmental trajectories across time points demonstrated age-related changes which plateaued between term-equivalent and 2 years of age in the majority of posterior tracts and between 2 and 4 years of age in anterior tracts. Between preterm and term-equivalent scans, FA rates of change were slower in anterior than posterior tracts. Partial least squares analyses revealed associations between slower MD and RD rates of change within the external and internal capsule with lower intelligence quotients and language scores at 4 years of age. These results uniquely demonstrate early white matter development and its linkage to cognitive functions.

Memory deficits following neonatal critical illness: a common neurodevelopmental pathway

Over the past decade, evidence has emerged that children growing up after neonatal critical illness, irrespective of underlying diagnosis, are at risk of memory impairment and academic problems. These difficulties are manifest even when intelligence is within the normal range. In this Review, we propose a common neurodevelopmental pathway following neonatal critical illness by showing that survivors of preterm birth, congenital heart disease, and severe respiratory failure share an increased risk of long-term memory deficits and associated hippocampal alterations. Rather than a consequence of underlying diagnosis, we suggest that this shared vulnerability is probably related to common conditions associated with neonatal critical illness, including hypoxia, neuroinflammation, stress, exposure to anaesthetics, or a complex interplay of these factors at different postconceptional ages. Future work should be aimed at improvement of early identification of patients at risk and evaluation of intervention modalities, such as exercise or cognitive training.

Hypoxia-ischemia modifies postsynaptic GluN2B-containing NMDA receptor complexes in the neonatal mouse brain

The N-methyl-d-aspartate-type glutamate receptor (NMDAR)-associated multiprotein complexes are indispensable for synaptic plasticity and cognitive functions. While purification and proteomic analyses of these signaling complexes have been performed in adult rodent and human brain, much less is known about the protein composition of NMDAR complexes in the developing brain and their modifications by neonatal hypoxic-ischemic (HI) brain injury. In this study, the postsynaptic density proteins were prepared from postnatal day 9 naïve, sham-operated and HI-injured mouse cortex. The GluN2B-containing NMDAR complexes were purified by immunoprecipitation with a mouse GluN2B antibody and subjected to mass spectrometry analysis for determination of the GluN2B binding partners. A total of 71 proteins of different functional categories were identified from the naïve animals as native GluN2B-interacting partners in the developing mouse brain. Neonatal HI reshaped the postsynaptic GluN2B interactome by recruiting new proteins, including multiple kinases, into the complexes; and modifying the existing associations within 1h of reperfusion. The early responses of postsynaptic NMDAR complexes and their related signaling networks may contribute to molecular processes leading to cell survival or death, brain damage and/or neurological disorders in term infants with neonatal encephalopathy.

Embracing oligodendrocyte diversity in the context of perinatal injury

Emerging evidence is fueling a new appreciation of oligodendrocyte diversity that is overturning the traditional view that oligodendrocytes are a homogenous cell population. Oligodendrocytes of distinct origins, maturational stages, and regional locations may differ in their functional capacity or susceptibility to injury. One of the most unique qualities of the oligodendrocyte is its ability to produce myelin. Myelin abnormalities have been ascribed to a remarkable array of perinatal brain injuries, with concomitant oligodendrocyte dysregulation. Within this review, we discuss new insights into the diversity of the oligodendrocyte lineage and highlight their relevance in paradigms of perinatal brain injury. Future therapeutic development will be informed by comprehensive knowledge of oligodendrocyte pathophysiology that considers the particular facets of heterogeneity that this lineage exhibits.

White matter injury in the preterm infant: pathology and mechanisms

The human preterm brain is particularly susceptible to cerebral white matter injury (WMI) that disrupts the normal progression of developmental myelination. Advances in the care of preterm infants have resulted in a sustained reduction in the severity of WMI that has shifted from more severe focal necrotic lesions to milder diffuse WMI. Nevertheless, WMI remains a global health problem and the most common cause of chronic neurological morbidity from cerebral palsy and diverse neurobehavioral disabilities. Diffuse WMI involves maturation-dependent vulnerability of the oligodendrocyte (OL) lineage with selective degeneration of late oligodendrocyte progenitors (preOLs) triggered by oxidative stress and other insults. The magnitude and distribution of diffuse WMI are related to both the timing of appearance and regional distribution of susceptible preOLs. Diffuse WMI disrupts the normal progression of OL lineage maturation and myelination through aberrant mechanisms of regeneration and repair. PreOL degeneration is accompanied by early robust proliferation of OL progenitors that regenerate and augment the preOL pool available to generate myelinating OLs. However, newly generated preOLs fail to differentiate and initiate myelination along their normal developmental trajectory despite the presence of numerous intact-appearing axons. Disrupted preOL maturation is accompanied by diffuse gliosis and disturbances in the composition of the extracellular matrix and is mediated in part by inhibitory factors derived from reactive astrocytes. Signaling pathways implicated in disrupted myelination include those mediated by Notch, WNT-beta catenin, and hyaluronan. Hence, there exists a potentially broad but still poorly defined developmental window for interventions to promote white matter repair and myelination and potentially reverses the widespread disturbances in cerebral gray matter growth that accompanies WMI.

Prospective clinical biomarkers of caspase-mediated apoptosis associated with neuronal and neurovascular damage following stroke and other severe brain injuries: Implications for chronic neurodegeneration

Acute brain injuries, including ischemic and hemorrhagic stroke, as well as traumatic brain injury (TBI), are major worldwide health concerns with very limited options for effective diagnosis and treatment. Stroke and TBI pose an increased risk for the development of chronic neurodegenerative diseases, notably chronic traumatic encephalopathy, Alzheimer's disease, and Parkinson's disease. The existence of premorbid neurodegenerative diseases can exacerbate the severity and prognosis of acute brain injuries. Apoptosis involving caspase-3 is one of the most common mechanisms involved in the etiopathology of both acute and chronic neurological and neurodegenerative diseases, suggesting a relationship between these disorders. Over the past two decades, several clinical biomarkers of apoptosis have been identified in cerebrospinal fluid and peripheral blood following ischemic stroke, intracerebral and subarachnoid hemorrhage, and TBI. These biomarkers include selected caspases, notably caspase-3 and its specific cleavage products such as caspase-cleaved cytokeratin-18, caspase-cleaved tau, and a caspase-specific 120 kDa αII-spectrin breakdown product. The levels of these biomarkers might be a valuable tool for the identification of pathological pathways such as apoptosis and inflammation involved in injury progression, assessment of injury severity, and prediction of clinical outcomes. This review focuses on clinical studies involving biomarkers of caspase-3-mediated pathways, following stroke and TBI. The review further examines their prospective diagnostic utility, as well as clinical utility for improved personalized treatment of stroke and TBI patients and the development of prophylactic treatment chronic neurodegenerative disease.

High-Dose Erythropoietin and Hypothermia for Hypoxic-Ischemic Encephalopathy: A Phase II Trial

OBJECTIVE

To determine if multiple doses of erythropoietin (Epo) administered with hypothermia improve neuroradiographic and short-term outcomes of newborns with hypoxic-ischemic encephalopathy.

METHODS

In a phase II double-blinded, placebo-controlled trial, we randomized newborns to receive Epo (1000 U/kg intravenously; n = 24) or placebo (n = 26) at 1, 2, 3, 5, and 7 days of age. All infants had moderate/severe encephalopathy; perinatal depression (10 minute Apgar <5, pH <7.00 or base deficit ≥15, or resuscitation at 10 minutes); and received hypothermia. Primary outcome was neurodevelopment at 12 months assessed by the Alberta Infant Motor Scale and Warner Initial Developmental Evaluation. Two independent observers rated MRI brain injury severity by using an established scoring system.

RESULTS

The mean age at first study drug was 16.5 hours (SD, 5.9). Neonatal deaths did not significantly differ between Epo and placebo groups (8% vs 19%, P = .42). Brain MRI at mean 5.1 days (SD, 2.3) showed a lower global brain injury score in Epo-treated infants (median, 2 vs 11, P = .01). Moderate/severe brain injury (4% vs 44%, P = .002), subcortical (30% vs 68%, P = .02), and cerebellar injury (0% vs 20%, P = .05) were less frequent in the Epo than placebo group. At mean age 12.7 months (SD, 0.9), motor performance in Epo-treated (n = 21) versus placebo-treated (n = 20) infants were as follows: Alberta Infant Motor Scale (53.2 vs 42.8, P = .03); Warner Initial Developmental Evaluation (28.6 vs 23.8, P = .05).

CONCLUSIONS

High doses of Epo given with hypothermia for hypoxic-ischemic encephalopathy may result in less MRI brain injury and improved 1-year motor function.

Intracerebral Glycine Administration Impairs Energy and Redox Homeostasis and Induces Glial Reactivity in Cerebral Cortex of Newborn Rats

Accumulation of glycine (GLY) is the biochemical hallmark of glycine encephalopathy (GE), an aminoacidopathy characterized by severe neurological dysfunction that may lead to early death. In the present study, we evaluated the effect of a single intracerebroventricular administration of GLY on bioenergetics, redox homeostasis, and histopathology in brain of neonatal rats. Our results demonstrated that GLY decreased the activities of the respiratory chain complex IV and creatine kinase, induced reactive species generation, and diminished glutathione (GSH) levels 1, 5, and 10 days after GLY injection in cerebral cortex of 1-day-old rats. GLY also increased malondialdehyde (MDA) levels 5 days after GLY infusion in this brain region. Furthermore, GLY differentially modulated the activities of superoxide dismutase, catalase, and glutathione peroxidase depending on the period tested after GLY administration. In contrast, bioenergetics and redox parameters were not altered in brain of 5-day-old rats. Regarding the histopathological analysis, GLY increased S100β staining in cerebral cortex and striatum, and GFAP in corpus callosum of 1-day-old rats 5 days after injection. Finally, we verified that melatonin prevented the decrease of complex IV and CK activities and GSH concentrations, and the increase of MDA levels and S100β staining caused by GLY. Based on our findings, it may be presumed that impairment of redox and energy homeostasis and glial reactivity induced by GLY may contribute to the neurological dysfunction observed in GE.

Antenatal Magnesium and Cerebral Palsy in Preterm Infants

OBJECTIVE

To evaluate the relationship of maternal antenatal magnesium sulfate (MgSO4) with neonatal cranial ultrasound abnormalities and cerebral palsy (CP).

STUDY DESIGN

In a randomized trial of MgSO4 or placebo in women at high risk of preterm delivery, up to 3 cranial ultrasounds were obtained in the neonatal period. Images were reviewed by at least 2 pediatric radiologists masked to treatment and other clinical conditions. Diagnoses were predefined for intraventricular hemorrhage, periventricular leukomalacia, intracerebral echolucency or echodensity, and ventriculomegaly. CP was diagnosed at 2 years of age by standardized neurologic examination.

RESULTS

Intraventricular hemorrhage, periventricular leukomalacia, intracerebral echolucency or echodensity, and ventriculomegaly were all strongly associated with an increased risk of CP. MgSO4 administration did not affect the risk of cranial ultrasound abnormality observed at 35 weeks postmenstrual age or later. However, for the 82% of infants born at <32 weeks gestation, MgSO4 was associated with a reduction in risk of echolucency or echodensity. The reduction in risk for echolucency explained 21% of the effect of MgSO4 on CP (P = .04), and for echodensity explained 20% of the effect (P = .02).

CONCLUSIONS

MgSO4 given prior to preterm delivery was associated with decreased risk of developing echodensities and echolucencies at <32 weeks gestation. However, this effect can only partially explain the effect of MgSO4 on CP at 2 years of age.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00014989.

Increased Brain Perfusion Persists over the First Month of Life in Term Asphyxiated Newborns Treated with Hypothermia: Does it Reflect Activated Angiogenesis?

Many asphyxiated newborns still develop brain injury despite hypothermia therapy. The development of brain injury in these newborns has been related partly to brain perfusion abnormalities. The purposes of this study were to assess brain hyperperfusion over the first month of life in term asphyxiated newborns and to search for some histopathological clues indicating whether this hyperperfusion may be related to activated angiogenesis following asphyxia. In this prospective cohort study, regional cerebral blood flow was measured in term asphyxiated newborns treated with hypothermia around day 10 of life and around 1 month of life using magnetic resonance imaging (MRI) and arterial spin labeling. A total of 32 MRI scans were obtained from 24 term newborns. Asphyxiated newborns treated with hypothermia displayed an increased cerebral blood flow in the injured brain areas around day 10 of life and up to 1 month of life. In addition, we looked at the histopathological clues in a human asphyxiated newborn and in a rat model of neonatal encephalopathy. Vascular endothelial growth factor (VEGF) was expressed in the injured brain of an asphyxiated newborn treated with hypothermia in the first days of life and of rat pups 24-48 h after the hypoxic-ischemic event, and the endothelial cell count increased in the injured cortex of the pups 7 and 11 days after hypoxia-ischemia. Our data showed that the hyperperfusion measured by imaging persisted in the injured areas up to 1 month of life and that angiogenesis was activated in the injured brain of asphyxiated newborns.

What are the Best Animal Models for Testing Early Intervention in Cerebral Palsy?

Interventions to treat cerebral palsy should be initiated as soon as possible in order to restore the nervous system to the correct developmental trajectory. One drawback to this approach is that interventions have to undergo exceptionally rigorous assessment for both safety and efficacy prior to use in infants. Part of this process should involve research using animals but how good are our animal models? Part of the problem is that cerebral palsy is an umbrella term that covers a number of conditions. There are also many causal pathways to cerebral palsy, such as periventricular white matter injury in premature babies, perinatal infarcts of the middle cerebral artery, or generalized anoxia at the time of birth, indeed multiple causes, including intra-uterine infection or a genetic predisposition to infarction, may need to interact to produce a clinically significant injury. In this review, we consider which animal models best reproduce certain aspects of the condition, and the extent to which the multifactorial nature of cerebral palsy has been modeled. The degree to which the corticospinal system of various animal models human corticospinal system function and development is also explored. Where attempts have already been made to test early intervention in animal models, the outcomes are evaluated in light of the suitability of the model.

Noninvasive brain stimulation: the potential for use in the rehabilitation of pediatric acquired brain injury

Noninvasive brain stimulation (NIBS) offers the potential to modulate neural activity and recovery after acquired brain injury. There are few studies of NIBS in children, but a survey of those studies might provide insight into the potential for NIBS to modulate motor rehabilitation, seizures, and behavior in children. We surveyed the published literature prior to July 2014 for articles pertaining to children and NIBS with a focus on case series or trials. We also reviewed selected articles involving adults to illustrate specific points where the literature in children is lacking. A limited number of articles suggest that NIBS can transiently improve motor function. The evidence for an effect on seizures is mixed. Two open-label studies reported improvement of mood in adolescents with depression. NIBS may serve as a tool for pediatric neurorehabilitation, but many gaps in our knowledge must be filled before NIBS can be adopted as a clinical intervention. To move forward, the field needs adequately powered trials that can answer these questions. Such trials will be challenging to perform, will likely require multicenter collaboration, and may need to adopt novel trial designs that have been used with rare disorders.

Hypoxic preconditioning differentially affects GABAergic and glutamatergic neuronal cells in the injured cerebellum of the neonatal rat

In this study we examined cerebellar alterations in a neonatal rat model of hypoxic-ischemic brain injury with or without hypoxic preconditioning (Pc). Between postnatal days 7 and 15, the cerebellum is still undergoing intense cellular proliferation, differentiation and migration, dendritogenesis and synaptogenesis. The expression of glutamate decarboxylase 1 (GAD67) and the differentiation factor NeuroD1 were examined as markers of Purkinje and granule cells, respectively. We applied quantitative immunohistochemistry to sagittal cerebellar slices, and Western blot analysis of whole cerebella obtained from control (C) rats and rats submitted to Pc, hypoxia-ischemia (L) and a combination of both treatments (PcL). We found that either hypoxia-ischemia or Pc perturbed the granule cells in the posterior lobes, affecting their migration and final placement in the internal granular layer. These effects were partially attenuated when the Pc was delivered prior to the hypoxia-ischemia. Interestingly, whole nuclear NeuroD1 levels in Pc animals were comparable to those in the C rats. However, a subset of Purkinje cells that were severely affected by the hypoxic-ischemic insult—showing signs of neuronal distress at the levels of the nucleus, cytoplasm and dendritic arborization—were not protected by Pc. A monoclonal antibody specific for GAD67 revealed a three-band pattern in cytoplasmic extracts from whole P15 cerebella. A ∼110 kDa band, interpreted as a potential homodimer of a truncated form of GAD67, was reduced in Pc and L groups while its levels were close to the control animals in PcL rats. Additionally we demonstrated differential glial responses depending on the treatment, including astrogliosis in hypoxiated cerebella and a selective effect of hypoxia-ischemia on the vimentin-immunolabeled intermediate filaments of the Bergmann glia. Thus, while both glutamatergic and GABAergic cerebellar neurons are compromised by the hypoxic-ischemic insult, the former are protected by a preconditioning hypoxia while the latter are not.

Ischemia/Reperfusion-induced neovascularization in the cerebral cortex of the ovine fetus

Information on the effects of injury on neovascularization in the immature brain is limited. We investigated the effects of ischemia on cerebral cortex neovascularization after the exposure of fetuses to 30 minutes of cerebral ischemia followed by 48 hours of reperfusion (I/R-48), 30 minutes of cerebral ischemia followed by 72 hours of reperfusion (I/R-72), or sham control treatment (Non-I/R). Immunohistochemical and morphometric analyses of cerebral cortex sections included immunostaining for glial fibrillary acidic protein and collagen type IV (a molecular component of the vascular basal lamina) to determine the glial vascular network in fetal brains and Ki67 as a proliferation marker. Cerebral cortices from I/R-48 and I/R-72 fetuses exhibited general responses to ischemia, including reactive astrocyte morphology, which was not observed in Non-I/R fetuses. Cell bodies of reactive proliferating astrocytes, along with large end-feet, surrounded the walls of cerebral cortex microvessels in addition to the thick collagen type IV-enriched basal lamina. Morphometric analysis of the Non-I/R group with the I/R-48 and I/R-72 groups revealed increased collagen type IV density in I/R-72 cerebral cortex microvessels (p < 0.01), which also frequently displayed a sprouting appearance characterized by growing tip cells and activated pericytes. Increases in cerebral cortex basic fibroblast growth factor were associated with neovascularization. We conclude that increased neovascularization in fetal cerebral cortices occurs within 72 hours of ischemia.

Pathophysiology of glia in perinatal white matter injury

Injury to the preterm brain has a particular predilection for cerebral white matter. White matter injury (WMI) is the most common cause of brain injury in preterm infants and a major cause of chronic neurological morbidity including cerebral palsy. Factors that predispose to WMI include cerebral oxygenation disturbances and maternal-fetal infection. During the acute phase of WMI, pronounced oxidative damage occurs that targets late oligodendrocyte progenitors (pre-OLs). The developmental predilection for WMI to occur during prematurity appears to be related to both the timing of appearance and regional distribution of susceptible pre-OLs that are vulnerable to a variety of chemical mediators including reactive oxygen species, glutamate, cytokines, and adenosine. During the chronic phase of WMI, the white matter displays abberant regeneration and repair responses. Early OL progenitors respond to WMI with a rapid robust proliferative response that results in a several fold regeneration of pre-OLs that fail to terminally differentiate along their normal developmental time course. Pre-OL maturation arrest appears to be related in part to inhibitory factors that derive from reactive astrocytes in chronic lesions. Recent high field magnetic resonance imaging (MRI) data support that three distinct forms of chronic WMI exist, each of which displays unique MRI and histopathological features. These findings suggest the possibility that therapies directed at myelin regeneration and repair could be initiated early after WMI and monitored over time. These new mechanisms of acute and chronic WMI provide access to a variety of new strategies to prevent or promote repair of WMI in premature infants.

Age, plasticity, and homeostasis in childhood brain disorders

It has been widely accepted that the younger the age and/or immaturity of the organism, the greater the brain plasticity, the young age plasticity privilege. This paper examines the relation of a young age to plasticity, reviewing human pediatric brain disorders, as well as selected animal models, human developmental and adult brain disorder studies. As well, we review developmental and childhood acquired disorders that involve a failure of regulatory homeostasis. Our core arguments are as follows:

GABA(A) receptor chloride channels are involved in the neuroprotective role of GABA following oxygen and glucose deprivation in the rat cerebral cortex but not in the hippocampus

Assays on "ex vivo" sections of rat hippocampus and rat cerebral cortex, subjected to oxygen and glucose deprivation (OGD) and a three-hour reperfusion-like (RL) recovery, were performed in the presence of either GABA or the GABA(A) receptor binding site antagonist, bicuculline. Lactate dehydrogenase (LDH) and propidium iodide were used to quantify cell mortality. We also measured, using real-time quantitative polymerase chain reaction (qPCR), the early transcriptional response of a number of genes of the glutamatergic and GABAergic systems. Specifically, glial pre- and post-synaptic glutamatergic transporters (namely GLAST1a, EAAC-1, GLT-1 and VGLUT1), three GABAA receptor subunits (α1, β2 and γ2), and the GABAergic presynaptic marker, glutamic acid decarboxylase (GAD65), were studied. Mortality assays revealed that GABAA receptor chloride channels play an important role in the neuroprotective effect of GABA in the cerebral cortex, but have a much smaller effect in the hippocampus. We also found that GABA reverses the OGD-dependent decrease in GABA(A) receptor transcript levels, as well as mRNA levels of the membrane and vesicular glutamate transporter genes. Based on the markers used, we conclude that OGD results in differential responses in the GABAergic presynaptic and postsynaptic systems.

Magnetization transfer and diffusion imaging of acute axonal damage in the cerebral peduncle following hypoxia-ischemia in neonatal rats

BACKGROUND

Magnetic resonance imaging (MRI) of axonal degenerative changes in the cerebral peduncle of the corticospinal tract following cerebral hypoxic-ischemic damage might distinguish infants most appropriate for receiving prompt treatment. The optimal MRI sequence for very early diagnosis of axonal degenerative changes is unknown. We hypothesized that magnetization transfer ratio (MTR) imaging would be more sensitive than traditional MRI, e.g., T(2) or diffusion weighted imaging.

METHODS

Transient unilateral cerebral hypoxia-ischemia was produced in the neonatal rat followed by MRI of changes in T(2), the apparent diffusion coefficient (ADC) of water, and MTR, with a focus on the parietal cortex (an ischemic damaged region) and the cerebral peduncle (remote within the corticospinal tract). Rats were imaged at 2 h, 1 d, or 1 wk postinsult.

RESULTS

In the cerebral peduncle, MTR and T(2) responded similarly, with alterations occurring ipsilaterally at 1 d postinsult. ADC was most sensitive for detecting changes as early as 2 h postinsult, and this corresponded to a reduced staining of axonal filaments ipsilaterally.

CONCLUSION

MTR and T(2) imaging have comparable sensitivity for distinguishing early axonal damage in the cerebral peduncle. ADC imaging is highly sensitive for detecting early disruption of corticospinal axons, supporting its potential hyperacute diagnostic use clinically.

[Acquired CNS lesions in fetal MRI]

Acquired central nervous system (CNS) lesions are often subtle; therefore, the prenatal diagnosis of these lesions is extremely important. The fetal ultrasound examination and magnetic resonance imaging (MRI) are two important imaging methods that give an insight into these types lesions. The method of choice during pregnancy is still fetal ultrasound; however, fetal MRI is important when there are certain pathologies, e.g. periventricular leukomalacia (PVL) or malformations of the vein of Galen. In this manner clinicians can plan further therapy after childbirth in advance (e.g. cerebral angiography or embolization).

Deficits in social behavior emerge during development after pediatric traumatic brain injury in mice

The pediatric brain may be particularly vulnerable to social deficits after traumatic brain injury (TBI) due to the protracted nature of psychosocial development through adolescence. However, the majority of pre-clinical studies fail to assess social outcomes in experimental pediatric TBI. The current study evaluated social behavior in mice subjected to TBI at post-natal day (p)21. Social behaviors were assessed by a partition test, resident-intruder, three-chamber, and tube dominance tasks during adolescence (p35-42) and again during early adulthood (p60-70), during encounters with unfamiliar, naïve stimulus mice. Despite normal olfactory function and normal social behaviors during adolescence, brain-injured mice showed impaired social investigation by adulthood, evidenced by reduced ano-genital sniffing and reduced following of stimulus mice in the resident-intruder task, as well as a loss of preference for sociability in the three-chamber task. TBI mice also lacked a preference for social novelty, suggestive of a deficit in social recognition or memory. By adulthood, brain-injured mice exerted more frequent dominance in the tube task compared to sham-operated controls, a finding suggestive of aggressive tendencies. Together these findings reveal reduced social interaction and a tendency towards increased aggression, which evolves across development to adulthood. This emergence of aberrant social behavior, which parallels the development of other cognitive deficits in this model and behaviors seen in brain-injured children, is consistent with the hypothesis that the full extent of deficits is not realized until the associated skills reach maturity. Thus, efficacy of therapeutics for pediatric TBI should take into account the time-dependent emergence of abnormal behavioral patterns.

STAT3-mediated astrogliosis protects myelin development in neonatal brain injury

OBJECTIVE

Pathological findings in neonatal brain injury associated with preterm birth include focal and/or diffuse white matter injury (WMI). Despite the heterogeneous nature of this condition, reactive astrogliosis and microgliosis are frequently observed. Thus, molecular mechanisms by which glia activation contribute to WMI were investigated.

METHODS

Postmortem brains of neonatal brain injury were investigated to identify molecular features of reactive astrocytes. The contribution of astrogliosis to WMI was further tested in a mouse model in genetically engineered mice.

RESULTS

Activated STAT3 signaling in reactive astrocytes was found to be a common feature in postmortem brains of neonatal brain injury. In a mouse model of neonatal WMI, conditional deletion of STAT3 in astrocytes resulted in exacerbated WMI, which was associated with delayed maturation of oligodendrocytes. Mechanistically, the delay occurred in association with overexpression of transforming growth factor (TGF)β-1 in microglia, which in healthy controls decreased with myelin maturation in an age-dependent manner. TGFβ-1 directly and dose-dependently inhibited the maturation of purified oligodendrocyte progenitors, and pharmacological inhibition of TGFβ-1 signaling in vivo reversed the delay in myelin development. Factors secreted from STAT3-deficient astrocytes promoted elevated TGFβ-1 production in cultured microglia compared to wild-type astrocytes.

INTERPRETATION

These results suggest that myelin development is regulated by a mechanism involving crosstalk between microglia and oligodendrocyte progenitors. Reactive astrocytes may modify this signaling in a STAT3-dependent manner, preventing the pathological expression of TGFβ-1 in microglia and the impairment of oligodendrocyte maturation.

Understanding migraine through the lens of maladaptive stress responses: a model disease of allostatic load

The brain and body respond to potential and actual stressful events by activating hormonal and neural mediators and modifying behaviors to adapt. Such responses help maintain physiological stability ("allostasis"). When behavioral or physiological stressors are frequent and/or severe, allostatic responses can become dysregulated and maladaptive ("allostatic load"). Allostatic load may alter brain networks both functionally and structurally. As a result, the brain's responses to continued/subsequent stressors are abnormal, and behavior and systemic physiology are altered in ways that can, in a vicious cycle, lead to further allostatic load. Migraine patients are continually exposed to such stressors, resulting in changes to central and peripheral physiology and function. Here we review how changes in brain states that occur as a result of repeated migraines may be explained by a maladaptive feedforward allostatic cascade model and how understanding migraine within the context of allostatic load model suggests alternative treatments for this often-debilitating disease.

Regional differences in susceptibility to hypoxic-ischemic injury in the preterm brain: exploring the spectrum from white matter loss to selective grey matter injury in a rat model

Models of premature brain injury have largely focused on the white matter injury thought to underlie periventricular leukomalacia (PVL). However, with increased survival of very low birth weight infants, injury patterns involving grey matter are now recognized. We aimed to determine how grey matter lesions relate to hypoxic-ischemic- (HI) mediated white matter injury by modifying our rat model of PVL. Following HI, microglial infiltration, astrocytosis, and neuronal and axonal degeneration increased in a region-specific manner dependent on the severity of myelin loss in pericallosal white matter. The spectrum of injury ranged from mild, where diffuse white matter abnormalities were dominant and were associated with mild axonal injury and local microglial activation, to severe HI injury characterized by focal MBP loss, widespread neuronal degeneration, axonal damage, and gliosis throughout the neocortex, caudate putamen, and thalamus. In sum, selective regional white matter loss occurs in the preterm rat concomitantly with a clinically relevant spectrum of grey matter injury. These data demonstrate an interspecies similarity of brain injury patterns and further substantiates the reliable use of this model for the study of preterm brain injury.

Developmental profiles of infant EEG: overlap with transient cortical circuits

OBJECTIVE

To quantify spectral power in frequency specific bands and commonly observed types of bursting activities in the EEG during early human development.

METHODS

An extensive archive of EEG data from human infants from 35 to 52 weeks postmenstrual age obtained in a prior multi-center study was analyzed using power spectrum analyses and a high frequency burst detection algorithm.

RESULTS

Low frequency power increased with age; however, high frequency power decreased from 35 to 45 weeks. This unexpected decrease was largely attributable to a rapid decline in the number of high frequency bursts.

CONCLUSIONS

The decline in high frequency bursting activity overlaps with a developmental shift in GABA's actions on neurons from depolarizing to hyperpolarizing and the dissolution of the gap junction circuitry of the cortical subplate.

SIGNIFICANCE

We postulate that quantitative characterization of features of the EEG unique to early development provide indices for tracking changes in specific neurophysiologic mechanisms that are critical for normal development of brain function.

Cerebral cortical development in rodents and primates

Rodents and primates both show considerable variation in the overall size, the radial and tangential dimensions, folding and subdivisions into distinct areas of their cerebral cortex. Our current understanding of brain development is based on a handful of model systems. A detailed comparative analysis of the cellular and molecular mechanisms that regulate neural progenitor production, cell migration, and circuit assembly can provide much needed insights into the working of neocortical evolution. From the limited comparative data currently available, it is apparent that the emergence and variation of the neuronal progenitor cells have led to the production of increased neuronal populations and the evolution of the cortex. Further diversification and compartmentalization of the germinal zone together with changing proportions of radial glia in the ventricular zone and various intermediate progenitors in the subventricular zone may have been the driving force behind increased cell numbers in larger brains both in rodents and primates. Radial and tangential migratory patterns are both present in rodents and primates, but in different proportions. There are apparent differences between mouse and human in the generation and elaboration of the interneuronal subtypes and also in gene expression patterns associated with the appearance of distinct cortical areas. The increased cortical dimensions and the formation of a more elaborate cortical architecture in primates require a larger and more compartmentalized transient subplate zone during development. More comparative analysis in rodent and primate species with large, small, and smooth and folded brains is needed to reveal the biological significance of the alterations in these cortical developmental programs.

The effect of whole-body cooling on brain metabolism following perinatal hypoxic-ischemic injury

INTRODUCTION

Magnetic resonance imaging (MRI) and spectroscopy (MRS) have proven valuable in evaluating neonatal hypoxic-ischemic injury (HII).

RESULTS

MRI scores in the basal ganglia of HII/HT(+) neonates were significantly lower than HII/HT(-) neonates, indicating less severe injury and were associated with lower discharge encephalopathy severity scores in the HII/HT(+) group (P = 0.01). Lactate (Lac) was detected in the occipital gray matter (OGM) and thalamus (TH) of significantly more HII/HT(-) neonates (31.6 and 35.3%) as compared to the HII/HT(+) group (10.5 and 15.8%). In contrast, the -N-acetylaspartate (NAA)-based ratios in the OGM and TH did not differ between the HII groups.

DISCUSSION

Our data show that the HT was associated with a decrease in the number of HII neonates with detectable cortical and subcortical Lac as well as a decrease in the number of MRI-detectable subcortical lesions.

METHODS

We retrospectively compared the medical and neuroimaging data of 19 HII neonates who received 72 h of whole-body cooling (HII/HT(+)) with those of 19 noncooled HII neonates (HII/HT(-)) to determine whether hypothermia was associated with improved recovery from the injury as measured by MRI and MRS within the first 14 days of life. MRI scores and metabolite ratios of HII/HT(+) and HII/HT(-) neonates were also compared with nine healthy, nonasphyxiated "control" neonates.

Differential susceptibility to axonopathy in necrotic and non-necrotic perinatal white matter injury

BACKGROUND AND PURPOSE

White matter injury (WMI) is the leading cause of brain injury in preterm survivors and results in myelination failure. Although axonal degeneration occurs in necrotic lesions, the role of axonopathy in myelination failure remains controversial for diffuse non-necrotic WMI, which is currently the major form of WMI. We determined the burden of axonopathy in diffuse lesions.

METHODS

We analyzed WMI in a preterm fetal sheep model of global cerebral ischemia that replicates the relative burden of necrotic and non-necrotic human WMI. WMI was analyzed at 1 or 2 weeks after ischemia and identified by ex vivo high-field (11.7 Tesla) magnetic resonance imaging of fixed brain tissue. Axonal integrity was analyzed by immunohistochemical detection of axon injury markers and by transmission electron microscopy to quantify axon loss and degeneration in magnetic resonance imaging-defined lesions.

RESULTS

Axonal degeneration, defined by staining for neurofilament protein and β-amyloid precursor protein, was restricted to discrete necrotic foci with robust microglial activation. Unexpectedly, axonal degeneration was not visualized in the major form of WMI, which comprised large non-necrotic lesions with diffuse reactive astrogliosis. In these major lesions, quantitative electron microscopy studies confirmed no significant differences in the density of intact and degenerating axons or in the distribution of axon diameters relative to controls.

CONCLUSIONS

The mechanism of myelination failure differs significantly in perinatal WMI dependent on the burden of necrosis. Axonopathy is associated with focal necrotic injury but not with primary diffuse non-necrotic lesions, which supports that intact axons in the primary lesions are potential targets for myelination.