Neurobiology of injury to the developing brain

Atorvastatin Promotes Pro/anti-inflammatory Phenotypic Transformation of Microglia via Wnt/β-catenin Pathway in Hypoxic-Ischemic Neonatal Rats

Inflammatory reaction plays a key role in the pathogenesis of hypoxic-ischemic encephalopathy (HIE) in neonates. Microglia are resident innate immune cells in the central nervous system and are profoundly involved in neuroinflammation. Studies have revealed that atorvastatin exerts a neuroprotective effect by regulating neuroinflammation in adult animal models of brain stroke and traumatic brain injury, but its role regarding damage to the developing brain remains unclear. This study aimed to clarify the effect and mechanism of atorvastatin on the regulation of microglia function in neonatal hypoxic-ischemic brain damage (HIBD). The oxygen glucose deprivation (OGD) of microglia and neonatal rat HIBD model was established. Atorvastatin, recombinant sclerostin protein (SOST), and XAV939 (degradation of β-catenin) were administered to OGD microglia and HIBD rats. The pathological changes of brain tissue, cerebral infarction volume, learning and memory ability of rats, pro-inflammatory (CD16+/Iba1+) and anti-inflammatory (CD206+/Iba1+) microglia markers, inflammation-related indicators (Inos, Tnfα, Il6, Arg1, Tgfb, and Mrc1), and Wnt/β-catenin signaling molecules were examined. Atorvastatin reduced OGD-induced pro-inflammatory microglia and pro-inflammatory factors, while increasing anti-inflammatory microglia and anti-inflammatory factors. In vivo, atorvastatin attenuated hypoxia-ischemia (HI)-induced neuroinflammation and brain damage. Mechanistically, atorvastatin decreased SOST expression and activated the Wnt/β-catenin signaling pathway, and the administration of recombinant SOST protein or XAV939 inhibited Wnt/β-catenin signaling and attenuated the anti-inflammatory effect of atorvastatin. Atorvastatin promotes the pro/anti-inflammatory phenotypic transformation of microglia via the Wnt/β-catenin pathway in HI neonatal rats. Atorvastatin may be developed as a potent agent for the treatment of HIE in neonates.

Clinical characteristics of cystic encephalomalacia in children

Purpose

To investigate the primary causes and clinical characteristics of cystic encephalomalacia (CE) in children.

Methods

The clinical data of 50 children who were admitted to our hospital due to CE between January 2008 and December 2020 were retrospectively reviewed. Their primary causes, clinical manifestations and cranial magnetic resonance imaging features were analyzed.

Results

Among all patients, 5 had prematurity, 19 had hypoxic-ischemic encephalopathy (HIE), 13 had intracranial infection, 14 had traumatic brain injury and hemorrhage, 4 had cerebral infarction, 2 had congenital genetic diseases, and 1 had hypoglycemia. The average time from primary disease onset to CE diagnosis was 70.1 ± 61.0 days. The clinical manifestations included speech or motor developmental delay (n = 33), epilepsy (n = 31), dystonia (n = 27), limb paralysis (n = 16), and visual or auditory impairment (n = 5). Patients with HIE as the primary cause of CE had a significantly higher occurrence of dystonia, while a significantly higher incidence of paralysis was observed in those with cerebral infarction as the primary cause.

Conclusion

CE in children is mainly caused by HIE, intracranial infection, and cerebral hemorrhage. The major clinical manifestations included speech or motor developmental delay, epilepsy, and dystonia. Magnetic resonance imaging is an important tool for the diagnosis of CE.

Investigating the structural network underlying brain-immune interactions using combined histopathology and neuroimaging: a critical review for its relevance in acute and long COVID-19

Current views on immunity support the idea that immunity extends beyond defense functions and is tightly intertwined with several other fields of biology such as virology, microbiology, physiology and ecology. It is also critical for our understanding of autoimmunity and cancer, two topics of great biological relevance and for critical public health considerations such as disease prevention and treatment. Central to this review, the immune system is known to interact intimately with the nervous system and has been recently hypothesized to be involved not only in autonomic and limbic bio-behaviors but also in cognitive function. Herein we review the structural architecture of the brain network involved in immune response. Furthermore, we elaborate upon the implications of inflammatory processes affecting brain-immune interactions as reported recently in pathological conditions due to SARS-Cov-2 virus infection, namely in acute and post-acute COVID-19. Moreover, we discuss how current neuroimaging techniques combined with ad hoc clinical autopsies and histopathological analyses could critically affect the validity of clinical translation in studies of human brain-immune interactions using neuroimaging. Advances in our understanding of brain-immune interactions are expected to translate into novel therapeutic avenues in a vast array of domains including cancer, autoimmune diseases or viral infections such as in acute and post-acute or Long COVID-19.

Akt/mTOR Pathway Agonist SC79 Inhibits Autophagy and Apoptosis of Oligodendrocyte Precursor Cells Associated with Neonatal White Matter Dysplasia

White matter dysplasia (WMD) in preterm infants due to intrauterine inflammation is caused by excessive apoptosis of oligodendrocyte precursor cells (OPCs). In recent years, studies have found that excessive autophagy and apoptosis are highly interconnected and important in infection and inflammatory diseases in general. Therefore, in this study, we aimed to confirm whether regulation of autophagy by using the Akt phosphorylation agonist SC79 can inhibit abnormal apoptosis of OPCs and promote myelin maturation and white matter development in neonatal rats with WMD. We investigated the effect of inflammation on oligodendrocyte development in P0 neonatal rats by intracerebellar injection of LPS, and collected brain tissue at P2 and P5. Immunohistochemical and immunofluorescence staining were used to evaluate white matter damage, while immunofluorescence staining, terminal deoxynucleotidyl transferase dUTP nick end labeling analysis (TUNEL), and western blotting were used to evaluate autophagy and apoptosis. First, we observed that white matter development was arrested and white matter fiber maturation was impaired in LPS-inflicted pups compared with those in the sham-operated group. Second, treatment with SC79 reduced the levels of LC3II, caspase 3, caspase 9, and Bax/Bcl-2 and increased the levels of p62, p-Akt, and p-mTOR in the brain tissue of neonatal rats. Finally, SC79 treatment inhibited OPC apoptosis by increasing the binding of Beclin 1 to Bcl-2, which promoted OPC differentiation and maturation. However, the opposite results were observed after rapamycin administration. Taken together, our results suggest that SC79 can inhibit the abnormal apoptosis of OPCs caused by excessive autophagy through the Akt/mTOR pathway and that SC79 is a potential therapeutic agent for WMD in preterm infants.

Progress in the treatment of neonatal hypoxic-ischemic encephalopathy with umbilical cord blood mononuclear cells

Neonatal hypoxic-ischemic encephalopathy (HIE) is a common disease among newborns, which is a leading cause of neonatal death and permanent neurological sequelae. Therapeutic hypothermia (TH) is the only method for the treatment of HIE that has been recognized effective clinically at home and abroad, but the efficacy is limited. Recent research suggests that the cord blood-derived mononuclear cells (CB-MNCs), which the refer to blood cells containing one nucleus in the cord blood, exert anti-oxidative, anti-inflammatory, anti-apoptotic effects and play a neuroprotective role in HIE. This review focuses on safety and efficacy, the route of administration, dose, timing and combination treatment of CB-MNCs in HIE.

Indirect evidence for altered dopaminergic neurotransmission in very premature-born adults

While animal models indicate altered brain dopaminergic neurotransmission after premature birth, corresponding evidence in humans is scarce due to missing molecular imaging studies. To overcome this limitation, we studied dopaminergic neurotransmission changes in human prematurity indirectly by evaluating the spatial co-localization of regional alterations in blood oxygenation fluctuations with the distribution of adult dopaminergic neurotransmission. The study cohort comprised 99 very premature-born (<32 weeks of gestation and/or birth weight below 1500 g) and 107 full-term born young adults, being assessed by resting-state functional MRI (rs-fMRI) and IQ testing. Normative molecular imaging dopamine neurotransmission maps were derived from independent healthy control groups. We computed the co-localization of local (rs-fMRI) activity alterations in premature-born adults with respect to term-born individuals to different measures of dopaminergic neurotransmission. We performed selectivity analyses regarding other neuromodulatory systems and MRI measures. In addition, we tested if the strength of the co-localization is related to perinatal measures and IQ. We found selectively altered co-localization of rs-fMRI activity in the premature-born cohort with dopamine-2/3-receptor availability in premature-born adults. Alterations were specific for the dopaminergic system but not for the used MRI measure. The strength of the co-localization was negatively correlated with IQ. In line with animal studies, our findings support the notion of altered dopaminergic neurotransmission in prematurity which is associated with cognitive performance.

Chemogenetic activation of astrocytes promotes remyelination and restores cognitive deficits in visceral hypersensitive rats

Using a well-established chronic visceral hypersensitivity (VH) rat model, we characterized the decrease of myelin basic protein, reduced number of mature oligodendrocytes (OLs), and hypomyelination in the anterior cingulate cortex (ACC). The results of rat gambling test showed impaired decision-making, and the results of electrophysiological studies showed desynchronization in the ACC to basolateral amygdala (BLA) neural circuitry. Astrocytes release various factors that modulate oligodendrocyte progenitor cell proliferation and myelination. Astrocytic Gq-modulation through expression of hM3Dq facilitated oligodendrocyte progenitor cell proliferation and OL differentiation, and enhanced ACC myelination in VH rats. Activating astrocytic Gq rescued impaired decision-making and desynchronization in ACC-BLA. These data indicate that ACC hypomyelination is an important component of impaired decision-making and network desynchronization in VH. Astrocytic Gq activity plays a significant role in oligodendrocyte myelination and decision-making behavior in VH. Insights from these studies have potential for interventions in myelin-related diseases such as chronic pain-associated cognitive disorders.

A2A Adenosine Receptor: A Possible Therapeutic Target for Alzheimer's Disease by Regulating NLRP3 Inflammasome Activity?

The A2A adenosine receptor, a member of the P1 purinergic receptor family, plays a crucial role in the pathophysiology of different neurodegenerative illnesses, including Alzheimer’s disease (AD). It regulates both neurons and glial cells, thus modulating synaptic transmission and neuroinflammation. AD is a complex, progressive neurological condition that is the leading cause of dementia in the world’s old population (>65 years of age). Amyloid peptide-β extracellular accumulation and neurofibrillary tangles constitute the principal etiologic tracts, resulting in apoptosis, brain shrinkage, and neuroinflammation. Interestingly, a growing body of evidence suggests a role of NLRP3 inflammasome as a target to treat neurodegenerative diseases. It represents a tripartite multiprotein complex including NLRP3, ASC, and procaspase-1. Its activation requires two steps that lead with IL-1β and IL-18 release through caspase-1 activation. NLRP3 inhibition provides neuroprotection, and in recent years adenosine, through the A2A receptor, has been reported to modulate NLRP3 functions to reduce organ damage. In this review, we describe the role of NLRP3 in AD pathogenesis, both alone and in connection to A2A receptor regulation, in order to highlight a novel approach to address treatment of AD.

Caffeine treatment started before injury reduces hypoxic-ischemic white-matter damage in neonatal rats by regulating phenotypic microglia polarization

BACKGROUND

Reducing neuroinflammatory damage is an effective strategy for treating white-matter damage (WMD) in premature infants. Caffeine can ameliorate hypoxia-ischemia-induced brain WMD; however, its neuroprotective effect and mechanism against hypoxic-ischemic WMD remain unclear.

METHODS

We used 3-day-old Sprague-Dawley rats to establish a model of cerebral hypoxia-ischemia-induced brain WMD after unilateral common carotid artery ligation and hypoxia exposure (8% O₂ + 92% N₂) for 2.5 h. Mechanism experiments were conducted to detect M1/M2 polarization and activation of microglia and NLRP3 inflammasome.

RESULTS

Caffeine inhibited NLRP3 inflammasome activation, reduced microglial Iba-1 activation, inhibited microglia M1 polarization, and promoted microglia M2 polarization by downregulating CD86 and iNOS protein expression, inhibiting the transcription of the proinflammatory TNF-α and IL-1β, upregulating CD206 and Arg-1 expression, and promoting the transcription of the anti-inflammatory factors IL-10 and TGF-β. Importantly, we found that these caffeine-mediated effects could be reversed after inhibiting A2aR activity.

CONCLUSIONS

Caffeine improved long-term cognitive function in neonatal rats with hypoxic-ischemic WMD via A2aR-mediated inhibition of NLRP3 inflammasome activation, reduction of microglial activation, regulation of the phenotypic polarization of microglia and the release of inflammatory factors, and improvement of myelination development.

IMPACT

The direct protective effect of caffeine on hypoxic-ischemic white-matter damage (WMD) and its mechanism remains unclear. This study elucidated this mechanism using neonatal rats as an animal model of hypoxia-ischemia-induced cerebral WMD. The findings demonstrated caffeine as a promising therapeutic tool against immature WMD to protect neonatal cognitive function. We found that caffeine pretreatment reduced WMD in immature brains via regulation of microglial activation and polarization by adenosine A2a receptor, thereby, providing a scientific basis for future clinical application of caffeine.

Sustained Energy Deficit Following Perinatal Asphyxia: A Shift towards the Fructose-2,6-bisphosphatase (TIGAR)-Dependent Pentose Phosphate Pathway and Postnatal Development

Labor and delivery entail a complex and sequential metabolic and physiologic cascade, culminating in most circumstances in successful childbirth, although delivery can be a risky episode if oxygen supply is interrupted, resulting in perinatal asphyxia (PA). PA causes an energy failure, leading to cell dysfunction and death if re-oxygenation is not promptly restored. PA is associated with long-term effects, challenging the ability of the brain to cope with stressors occurring along with life. We review here relevant targets responsible for metabolic cascades linked to neurodevelopmental impairments, that we have identified with a model of global PA in rats. Severe PA induces a sustained effect on redox homeostasis, increasing oxidative stress, decreasing metabolic and tissue antioxidant capacity in vulnerable brain regions, which remains weeks after the insult. Catalase activity is decreased in mesencephalon and hippocampus from PA-exposed (AS), compared to control neonates (CS), in parallel with increased cleaved caspase-3 levels, associated with decreased glutathione reductase and glutathione peroxidase activity, a shift towards the TIGAR-dependent pentose phosphate pathway, and delayed calpain-dependent cell death. The brain damage continues long after the re-oxygenation period, extending for weeks after PA, affecting neurons and glial cells, including myelination in grey and white matter. The resulting vulnerability was investigated with organotypic cultures built from AS and CS rat newborns, showing that substantia nigra TH-dopamine-positive cells from AS were more vulnerable to 1 mM of H2O2 than those from CS animals. Several therapeutic strategies are discussed, including hypothermia; N-acetylcysteine; memantine; nicotinamide, and intranasally administered mesenchymal stem cell secretomes, promising clinical translation.

HDAC2/3 inhibitor MI192 mitigates oligodendrocyte loss and reduces microglial activation upon injury: A potential role of epigenetics

Background:

During development, oligodendrocyte (OL) lineage cells are susceptible to injury, leading to life-long clinical neurodevelopmental deficits, which lack effective treatments. Drugs targeting epigenetic modifications that inhibit histone deacetylases (HDACs) protect from many clinical neurodegenerative disorders.

Aim:

This study aimed to investigate the therapeutic potential of histone deacetylase 2/3 (HDAC2/3) inhibitor MI192 on white matter (WM) pathology in a model of neonatal rat brain injury.

Methods:

Wistar rats (8.5-day-old, n = 32) were used to generate brain tissues. The tissues were cultured and then randomly divided into four groups and treated as following: group I (sham); the tissues were cultured under normoxia, group II (vehicle); DMSO only, group III (injury, INJ); the tissues were exposed to 20 minutes oxygen-glucose deprivation (OGD) insult, and group IV (INJ + MI192); the tissues were subjected to the OGD insult and then treated with the MI192 inhibitor. On culture day 10, the tissues were fixed for biochemical and histological examinations.

Results:

The results showed that inhibition of HDAC2/3 activity alleviated WM pathology. Specifically, MI192 treatment significantly reduced cell death, minimized apoptosis, and mitigates the loss of the MBP⁺ OLs and their precursors (NG₂⁺ OPCs). Additionally, MI192 decreased the density of reactive microglia (OX−42⁺). These findings demonstrate that the inhibition of HDAC2/3 activity post-insult alleviates WM pathology through mechanism(s) including preserving OL lineage cells and suppressing microglial activation.

Conclusion:

The findings of this study suggest that HDAC2/3 inhibition is a rational strategy to preserve WM or reverse its pathology upon newborn brain injury.

6-Gingerol Alleviates Neonatal Hypoxic-Ischemic Cerebral and White Matter Injury and Contributes to Functional Recovery

Hypoxic-ischemic encephalopathy (HIE) is one main cause of neonatal death and disability, causing substantial injury to white and gray matter, which can lead to severe neurobehavioral dysfunction, including intellectual disability and dyskinesia. Inflammation, nerve cell death, and white matter injury are important factors in the pathological process of HIE. 6-Gingerol is a ginger extract, which reduces inflammatory response and cell death. However, the role of 6-Gingerol in neonatal hypoxic-ischemic brain injury (HIBI) remains unknown. In this study, we constructed a mouse HIBI model and analyzed the protective effect of 6-Gingerol on HIBI by using behavioral tests, histological staining, qPCR and western blot. Here, we found that 6-Gingerol treatment could alleviate HIBI and improve short-term reflex performance, which is closely related to cell death and neuroinflammation. Additionally, 6-Gingerol reduced neuronal apoptosis, pro-inflammatory factor release, as well as microglial activation. Furthermore, 6-Gingerol significantly improved motor disability, which is associated with white matter damage. Thus, our results showed that 6-Gingerol could reduce the loss of myelin sheaths, alleviate cell death of oligodendrocytes, and stimulate the maturation of oligodendrocytes. In terms of mechanism, we found that 6-Gingerol decreased histone H3K27me3 levels, activated AKT pathway and inhibited the activation of ERK and NF-κB pathway at 3 days post-HIBI. Taken together, our data clearly indicate that 6-Gingerol plays a neuroprotective role against HIBI by epigenetic modification and regulation of AKT, ERK, and NF-κB pathways, inhibiting inflammatory responses and reducing cell death.

White Matter Alterations Associated with Pro-inflammatory Cytokines in Patients with Major Depressive Disorder

Objective

Regarding the neuroinflammatory theory of major depressive disorder (MDD), little is known about the effect of pro-inflammatory cytokines on white matter (WM) changes in MDD. We aimed to investigate the relationship between pro-inflammatory cytokines and WM alterations in patients with MDD.

Methods

Twenty-two patients with MDD and 22 healthy controls (HC) were evaluated for brain imaging and pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, IL-8, interferon-γ and tumor necrosis factor (TNF)-α. Tract-based spatial statistics and FreeSurfer were used for brain image analysis.

Results

The levels of TNF-α and IL-8 were significantly higher in the MDD group than in HC. Compared to HC, lower fractional anisotropy (FA), and higher median diffusivity (MD) and radial diffusivity (RD) values were found in the MDD group for several WM regions. Voxel-wise correlation analysis showed that the level of TNF-α was negatively correlated with FA, and positively correlated with MD and RD in the left body and genu of the corpus callosum, left anterior corona radiata, and left superior corona radiata.

Conclusion

Our findings suggest that TNF-α may play an important role in the WM alterations in depression, possibly through demyelination.

Histamine H2 receptor negatively regulates oligodendrocyte differentiation in neonatal hypoxic-ischemic white matter injury

Neonatal hypoxic-ischemic encephalopathy (HIE) with the pathological characteristic of white matter injury often leads to lifelong cognitive and neurobehavioral dysfunction, but relevant therapies to promote remyelination are still unavailable. We found that histamine H₂ receptor (H₂R) negatively regulated the oligodendrocyte differentiation rate without affecting the oligodendrocytes at the oligodendrocyte precursor cell stage or mature stage following oxygen-glucose deprivation in vitro. Notably, selective deletion of the H₂R gene (Hrh2) in differentiating oligodendrocytes (Hrh2^fl/fl;CNPase-Cre) improved their differentiation, remyelination, and functional recovery following neonatal hypoxia-ischemia in mice. The regulation of oligodendrocyte differentiation by H₂R is mediated by binding with Axin2, which leads to up-regulation of the Wnt/β-catenin signaling pathway. Furthermore, H₂R antagonists also promoted oligodendrocyte differentiation and remyelination and the recovery of cognition and motor functions following neonatal hypoxia-ischemia. Thus, histamine H₂R in oligodendrocytes could serve as a novel and effective therapeutic target for the retard of oligodendrocyte differentiation and remyelination following neonatal hypoxia-ischemia. The H₂R antagonists may have potential therapeutic value for neonatal HIE.

Trigeminal neuropathy causes hypomyelination in the anterior cingulate cortex, disrupts the synchrony of neural circuitry, and impairs decision-making in male rats

Infraorbital nerve‐chronic constriction injury (ION‐CCI) has become the most popular chronic trigeminal neuropathic pain (TNP) injury animal model which causes prolonged mechanical allodynia. Accumulative evidence suggests that TNP interferes with cognitive functions, however the underlying mechanisms are not known. The aim of this study was to investigate decision‐making performance as well as synaptic and large‐scale neural synchronized alterations in the spinal trigeminal nucleus (SpV) circuitry and anterior cingulate cortex (ACC) neural circuitry in male rats with TNP. Rat gambling task showed that ION‐CCI led to decrease the proportion of good decision makers and increase the proportion of poor decision makers. Electrophysiological recordings showed long‐lasting synaptic potentiation of local field potential in the trigeminal ganglia‐SpV caudalis (SpVc) synapses in TNP rats. In this study, TNP led to disruption of ACC spike timing and basolateral amygdala (BLA) theta oscillation associated with suppressed synchronization of theta oscillation between the BLA and ACC, indicating reduced neuronal communications. Myelination is critical for information flow between brain regions, and myelin plasticity is an important feature for learning. Neural activity in the cortical regions impacts myelination by regulating oligodendrocyte (OL) proliferation, differentiation, and myelin formation. We characterized newly formed oligodendrocyte progenitor cells, and mature OLs are reduced in TNP and are associated with reduced myelin strength in the ACC region. The functional disturbances in the BLA‐ACC neural circuitry is pathologically associated with the myelin defects in the ACC region which may be relevant causes for the deficits in decision‐making in chronic TNP state.

Brain-Computer Interfaces for Children With Complex Communication Needs and Limited Mobility: A Systematic Review

Brain-computer interfaces (BCIs) represent a new frontier in the effort to maximize the ability of individuals with profound motor impairments to interact and communicate. While much literature points to BCIs' promise as an alternative access pathway, there have historically been few applications involving children and young adults with severe physical disabilities. As research is emerging in this sphere, this article aims to evaluate the current state of translating BCIs to the pediatric population. A systematic review was conducted using the Scopus, PubMed, and Ovid Medline databases. Studies of children and adolescents that reported BCI performance published in English in peer-reviewed journals between 2008 and May 2020 were included. Twelve publications were identified, providing strong evidence for continued research in pediatric BCIs. Research evidence was generally at multiple case study or exploratory study level, with modest sample sizes. Seven studies focused on BCIs for communication and five on mobility. Articles were categorized and grouped based on type of measurement (i.e., non-invasive and invasive), and the type of brain signal (i.e., sensory evoked potentials or movement-related potentials). Strengths and limitations of studies were identified and used to provide requirements for clinical translation of pediatric BCIs. This systematic review presents the state-of-the-art of pediatric BCIs focused on developing advanced technology to support children and youth with communication disabilities or limited manual ability. Despite a few research studies addressing the application of BCIs for communication and mobility in children, results are encouraging and future works should focus on customizable pediatric access technologies based on brain activity.

Neferine Protects against Hypoxic-Ischemic Brain Damage in Neonatal Rats by Suppressing NLRP3-Mediated Inflammasome Activation

Hypoxic-ischemic encephalopathy (HIE) is recognized as the main cause of neonatal death, and efficient treatment strategies remain limited. Given the prevalence of HIE and the associated fatality, further studies on its pathogenesis are warranted. Oxidative stress and neuroinflammatory injury are two important factors leading to brain tissue injury and nerve cell loss in HIE. Neferine, an alkaloid extracted from lotus seed embryo, exerts considerable effects against several diseases such as cancers and myocardial injury. In this study, we demonstrated the neuroprotective effect of neferine on HIE and hypothesized that it involves the inhibition of neuronal pyroptosis, thereby ameliorating neurological inflammation and oxidative stress. We demonstrated that the mRNA levels of proteins associated with pyroptosis including caspase-1, the caspase adaptor ASC, gasdermin D, interleukin- (IL-) 18, IL-1β, and some inflammatory factors were significantly increased in neonatal HIBD model rats compared to those in the control group. The increase in these factors was significantly suppressed by treatment with neferine. We stimulated PC12 cells with CoCl2 to induce neuronal HIBD in vitro and investigated the relationship between neferine and pyroptosis by altering the expression of the NLRP3 inflammasome. The overexpression of NLRP3 partially reversed the neuroprotective effect of neferine on HIBD, whereas NLRP3 knockdown further inhibited caspase-1 activation and IL-1β and IL18 expression. In addition, simultaneous alteration of NLRP3 expression induced changes in intracellular oxidative stress levels after HIBD. These findings indicate that neferine ameliorates neuroinflammation and oxidative stress injury by inhibiting pyroptosis after HIBD. Our study provides valuable information for future studies on neferine with respect to neuroinflammation and pyroptosis.

Brain MRI after therapeutic hypothermia in asphyxiated newborns: Predictive value at one year of imaging features

PURPOSE

To compare early brain MRI using a composite imaging score and outcome at one year in asphyxiated newborns treated by hypothermia.

METHODS

This retrospective study included for two years consecutive asphyxiated term newborns treated by hypothermia for hypoxic-ischemic encephalopathy, and who had brain MRI before day 8. Therapeutic hypothermia was initiated within the first 6 h of life and continued for 72 h. Imaging protocol included T1 and T2 sequences, diffusion-weighted imaging (DWI), evaluated with a specific composite score, and spectroscopy. Clinical evaluation was performed at one year of age, outcome was classified as favorable/unfavorable. The primary endpoint was the correlation between our MRI score and outcome with the definition of a threshold. The secondary endpoints were to find the most relevant criteria within the score and to evaluate objective signal measurements to support subjective criteria.

RESULTS

Among the 33 included patients, 9 died during the first days of life, 20 had a favorable outcome, 4 an unfavorable one. MRI score was correlated to a poor clinical outcome (p < 0.001). Most of the criteria within the score and spectroscopy results were relevant (p < 0.05). Cerebral edema was objectively assessed by the signal intensity ratio of white matter compared to cerebrospinal fluid (CSF) on T2-weighted images (p < 0.001).

CONCLUSION

MRI score was predictive of neurodevelopmental outcome at one year. The most relevant criteria within the score were DWI abnormalities in basal ganglia and thalami and loss of white-cortical grey matter differentiation. Signal intensity ratio between white matter and CSF higher than 0.75 supports the presence of edema.

Increased Brain Age Gap Estimate (BrainAGE) in Young Adults After Premature Birth

Recent evidence suggests increased metabolic and physiologic aging rates in premature-born adults. While the lasting consequences of premature birth on human brain development are known, its impact on brain aging remains unclear. We addressed the question of whether premature birth impacts brain age gap estimates (BrainAGE) using an accurate and robust machine-learning framework based on structural MRI in a large cohort of young premature-born adults (n = 101) and full-term (FT) controls (n = 111). Study participants are part of a geographically defined population study of premature-born individuals, which have been followed longitudinally from birth until young adulthood. We investigated the association between BrainAGE scores and perinatal variables as well as with outcomes of physical (total intracranial volume, TIV) and cognitive development (full-scale IQ, FS-IQ). We found increased BrainAGE in premature-born adults [median (interquartile range) = 1.4 (-1.3-4.7 years)] compared to full-term controls (p = 0.002, Cohen's d = 0.443), which was associated with low Gestational age (GA), low birth weight (BW), and increased neonatal treatment intensity but not with TIV or FS-IQ. In conclusion, results demonstrate elevated BrainAGE in premature-born adults, suggesting an increased risk for accelerated brain aging in human prematurity.

Human Wharton's Jelly Mesenchymal Stromal Cell-Derived Small Extracellular Vesicles Drive Oligodendroglial Maturation by Restraining MAPK/ERK and Notch Signaling Pathways

Peripartum cerebral hypoxia and ischemia, and intrauterine infection and inflammation, are detrimental for the precursor cells of the myelin-forming oligodendrocytes in the prematurely newborn, potentially leading to white matter injury (WMI) with long-term neurodevelopmental sequelae. Previous data show that hypomyelination observed in WMI is caused by arrested oligodendroglial maturation rather than oligodendrocyte-specific cell death. In a rat model of premature WMI, we have recently shown that small extracellular vesicles (sEV) derived from Wharton's jelly mesenchymal stromal cells (WJ-MSC) protect from myelination deficits. Thus, we hypothesized that sEV derived from WJ-MSC directly promote oligodendroglial maturation in oligodendrocyte precursor cells. To test this assumption, sEV were isolated from culture supernatants of human WJ-MSC by ultracentrifugation and co-cultured with the human immortalized oligodendrocyte precursor cell line MO3.13. As many regulatory functions in WMI have been ascribed to microRNA (miR) and as sEV are carriers of functional miR which can be delivered to target cells, we characterized and quantified the miR content of WJ-MSC-derived sEV by next-generation sequencing. We found that WJ-MSC-derived sEV co-localized with MO3.13 cells within 4 h. After 5 days of co-culture, the expression of myelin basic protein (MBP), a marker for mature oligodendrocytes, was significantly increased, while the oligodendrocyte precursor marker platelet-derived growth factor alpha (PDGFRα) was decreased. Notch and MAPK/ERK pathways known to inhibit oligodendrocyte maturation and differentiation were significantly reduced. The pathway enrichment analysis showed that the miR present in WJ-MSC-derived sEV target genes having key roles in the MAPK pathway. Our data strongly suggest that sEV from WJ-MSC directly drive the maturation of oligodendrocyte precursor cells by repressing Notch and MAPK/ERK signaling.

Oligodendrocyte lineage cells and depression

Depression is a common mental illness, affecting more than 300 million people worldwide. Decades of investigation have yielded symptomatic therapies for this disabling condition but have not led to a consensus about its pathogenesis. There are data to support several different theories of causation, including the monoamine hypothesis, hypothalamic-pituitary-adrenal axis changes, inflammation and immune system alterations, abnormalities of neurogenesis and a conducive environmental milieu. Research in these areas and others has greatly advanced the current understanding of depression; however, there are other, less widely known theories of pathogenesis. Oligodendrocyte lineage cells, including oligodendrocyte progenitor cells and mature oligodendrocytes, have numerous important functions, which include forming myelin sheaths that enwrap central nervous system axons, supporting axons metabolically, and mediating certain forms of neuroplasticity. These specialized glial cells have been implicated in psychiatric disorders such as depression. In this review, we summarize recent findings that shed light on how oligodendrocyte lineage cells might participate in the pathogenesis of depression, and we discuss new approaches for targeting these cells as a novel strategy to treat depression.

Regenerative Therapies to Restore Interneuron Disturbances in Experimental Models of Encephalopathy of Prematurity

Encephalopathy of Prematurity (EoP) is a major cause of morbidity in (extreme) preterm neonates. Though the majority of EoP research has focused on failure of oligodendrocyte maturation as an underlying pathophysiological mechanism, recent pioneer work has identified developmental disturbances in inhibitory interneurons to contribute to EoP. Here we investigated interneuron abnormalities in two experimental models of EoP and explored the potential of two promising treatment strategies, namely intranasal mesenchymal stem cells (MSCs) or insulin-like growth factor I (IGF1), to restore interneuron development. In rats, fetal inflammation and postnatal hypoxia led to a transient increase in total cortical interneuron numbers, with a layer-specific deficit in parvalbumin (PV)+ interneurons. Additionally, a transient excess of total cortical cell density was observed, including excitatory neuron numbers. In the hippocampal cornu ammonis (CA) 1 region, long-term deficits in total interneuron numbers and PV+ subtype were observed. In mice subjected to postnatal hypoxia/ischemia and systemic inflammation, total numbers of cortical interneurons remained unaffected; however, subtype analysis revealed a global, transient reduction in PV+ cells and a long-lasting layer-specific increase in vasoactive intestinal polypeptide (VIP)+ cells. In the dentate gyrus, a long-lasting deficit of somatostatin (SST)+ cells was observed. Both intranasal MSC and IGF1 therapy restored the majority of interneuron abnormalities in EoP mice. In line with the histological findings, EoP mice displayed impaired social behavior, which was partly restored by the therapies. In conclusion, induction of experimental EoP is associated with model-specific disturbances in interneuron development. In addition, intranasal MSCs and IGF1 are promising therapeutic strategies to aid interneuron development after EoP.

The impact of trophic and immunomodulatory factors on oligodendrocyte maturation: Potential treatments for encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a major cause of morbidity in preterm neonates, causing neurodevelopmental adversities that can lead to lifelong impairments. Preterm birth-related insults, such as cerebral oxygen fluctuations and perinatal inflammation, are believed to negatively impact brain development, leading to a range of brain abnormalities. Diffuse white matter injury is a major hallmark of EoP and characterized by widespread hypomyelination, the result of disturbances in oligodendrocyte lineage development. At present, there are no treatment options available, despite the enormous burden of EoP on patients, their families, and society. Over the years, research in the field of neonatal brain injury and other white matter pathologies has led to the identification of several promising trophic factors and cytokines that contribute to the survival and maturation of oligodendrocytes, and/or dampening neuroinflammation. In this review, we discuss the current literature on selected factors and their therapeutic potential to combat EoP, covering a wide range of in vitro, preclinical and clinical studies. Furthermore, we offer a future perspective on the translatability of these factors into clinical practice.

HIFα Regulates Developmental Myelination Independent of Autocrine Wnt Signaling

The developing CNS is exposed to physiological hypoxia, under which hypoxia-inducible factor α (HIFα) is stabilized and plays a crucial role in regulating neural development. The cellular and molecular mechanisms of HIFα in developmental myelination remain incompletely understood. A previous concept proposes that HIFα regulates CNS developmental myelination by activating the autocrine Wnt/β-catenin signaling in oligodendrocyte progenitor cells (OPCs). Here, by analyzing a battery of genetic mice of both sexes, we presented in vivo evidence supporting an alternative understanding of oligodendroglial HIFα-regulated developmental myelination. At the cellular level, we found that HIFα was required for developmental myelination by transiently controlling upstream OPC differentiation but not downstream oligodendrocyte maturation and that HIFα dysregulation in OPCs but not oligodendrocytes disturbed normal developmental myelination. We demonstrated that HIFα played a minor, if any, role in regulating canonical Wnt signaling in the oligodendroglial lineage or in the CNS. At the molecular level, blocking autocrine Wnt signaling did not affect HIFα-regulated OPC differentiation and myelination. We further identified HIFα-Sox9 regulatory axis as an underlying molecular mechanism in HIFα-regulated OPC differentiation. Our findings support a concept shift in our mechanistic understanding of HIFα-regulated CNS myelination from the previous Wnt-dependent view to a Wnt-independent one and unveil a previously unappreciated HIFα-Sox9 pathway in regulating OPC differentiation.SIGNIFICANCE STATEMENT Promoting disturbed developmental myelination is a promising option in treating diffuse white matter injury, previously called periventricular leukomalacia, a major form of brain injury affecting premature infants. In the developing CNS, hypoxia-inducible factor α (HIFα) is a key regulator that adapts neural cells to physiological and pathologic hypoxic cues. The role and mechanism of HIFα in oligodendroglial myelination, which is severely disturbed in preterm infants affected with diffuse white matter injury, is incompletely understood. Our findings presented here represent a concept shift in our mechanistic understanding of HIFα-regulated developmental myelination and suggest the potential of intervening with an oligodendroglial HIFα-mediated signaling pathway to mitigate disturbed myelination in premature white matter injury.

Intranasal mesenchymal stem cell therapy to boost myelination after encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a common cause of long-term neurodevelopmental morbidity in extreme preterm infants. Diffuse white matter injury (dWMI) is currently the most commonly observed form of EoP. Impaired maturation of oligodendrocytes (OLs) is the main underlying pathophysiological mechanism. No therapies are currently available to combat dWMI. Intranasal application of mesenchymal stem cells (MSCs) is a promising therapeutic option to boost neuroregeneration after injury. Here, we developed a double-hit dWMI mouse model and investigated the therapeutic potential of intranasal MSC therapy. Postnatal systemic inflammation and hypoxia-ischemia led to transient deficits in cortical myelination and OL maturation, functional deficits and neuroinflammation. Intranasal MSCs migrated dispersedly into the injured brain and potently improved myelination and functional outcome, dampened cerebral inflammationand rescued OL maturation after dWMI. Cocultures of MSCs with primary microglia or OLs show that MSCs secrete factors that directly promote OL maturation and dampen neuroinflammation. We show that MSCs adapt their secretome after ex vivo exposure to dWMI milieu and identified several factors including IGF1, EGF, LIF, and IL11 that potently boost OL maturation. Additionally, we showed that MSC-treated dWMI brains express different levels of these beneficial secreted factors. In conclusion, the combination of postnatal systemic inflammation and hypoxia-ischemia leads to a pattern of developmental brain abnormalities that mimics the clinical situation. Intranasal delivery of MSCs, that secrete several beneficial factors in situ, is a promising strategy to restore myelination after dWMI and subsequently improve the neurodevelopmental outcome of extreme preterm infants in the future.

The vulnerability of the immature brain

The concept of vulnerability of the immature brain is multifactorial by definition. Newer scientific work in this area has shifted and enlarged the concept from theoretical frameworks to the multiple levels (molecular, cellular, anatomic, network, behavioral) of the organization of the growing brain. The concept of vulnerability was first introduced by Donald O. Hebb in the 1950s and referred to the inability of the immature brain to completely recover normal development after a brain insult. The concept of vulnerability was further extended to the limitations of the brain in the development of specific skills in neuronal substrates originally used for other functions. We present an overview of some neurodevelopmental processes that characterize the immature brain and that can predict vulnerability in the case of disturbances: Hebb's principle, synaptic homeostasis, selective vulnerability of immature cells in mammals, and inherited constraint networks. A better understanding of the vulnerability mechanisms may help in early detection and prevention and further proposed individualized therapeutic approaches to enhance children's developmental outcomes.

Hippocampal subfield volumes are nonspecifically reduced in premature-born adults

Reduced global hippocampus volumes have been demonstrated in premature‐born individuals, from newborns to adults; however, it is unknown whether hippocampus subfield (HCSF) volumes are differentially affected by premature birth and how relevant they are for cognitive performance. To address these questions, we investigated magnetic resonance imaging (MRI)‐derived HCSF volumes in very premature‐born adults, and related them with general cognitive performance in adulthood. We assessed 103 very premature‐born (gestational age [GA] <32 weeks and/or birth weight <1,500 g) and 109 term‐born individuals with cognitive testing and structural MRI at 26 years of age. HCSFs were automatically segmented based on three‐dimensional T1‐ and T2‐weighted sequences and studied both individually and grouped into three functional units, namely hippocampus proper (HP), subicular complex (SC), and dentate gyrus (DG). Cognitive performance was measured using the Wechsler‐Adult‐Intelligence‐Scale (full‐scale intelligence quotient [FS‐IQ]) at 26 years. We observed bilateral volume reductions for almost all HCSF volumes in premature‐born adults and associations with GA and neonatal treatment intensity but not birth weight. Left‐sided HP, SC, and DG volumes were associated with adult FS‐IQ. Furthermore, left DG volume was a mediator of the association between GA and adult FS‐IQ in premature‐born individuals. Results demonstrate nonspecifically reduced HCSF volumes in premature‐born adults; but specific associations with cognitive outcome highlight the importance of the left DG. Data suggest that specific interventions toward hippocampus function might be promising to lower adverse cognitive effects of prematurity.

MicroRNA-374a-5p inhibits neuroinflammation in neonatal hypoxic-ischemic encephalopathy via regulating NLRP3 inflammasome targeted Smad6

AIMS

Neonatal hypoxic-ischemic encephalopathy (HIE) is still an important cause of neurological dysfunction. At present, there is no reliable biochemical index in clinical examination. Increasing evidence demonstrates that microRNAs (miRNAs) are involved in the process of HIE, and miR-374a-5p is down-regulated in HIE infants. In this study, the aim is to investigate the role and mechanism of miR-374a-5p in HIE.

MAIN METHODS

Sprague-Dawley (SD) rats were used to establish model of neonatal HIE, pathologic changes and inflammatory response of brain tissues were measured. Subsequently, primary microglia were induced by LPS (1 μg/ml) in vitro, the miR-374a-5p mimic, Ad-Smad6 adenovirus vector and NLRP3 siRNA oligo were applied for microglial transfection. Furthermore, the target relationship between miR-374a-5p and Smad6 was analyzed, while microglia activity and inflammatory factor (IL-1β, TNF-α and IL-6) levels were detected.

KEY FINDINGS

Herein, we found that over-expression of miR-374a-5p significantly attenuated brain injury and strongly inhibited the release of pro-inflammatory cytokines in neonatal rat HIE model. In vitro, miR-374a-5p inhibited LPS-induced microglial pro-inflammatory cytokines production by regulating NLRP3 inflammasome. In addition, Smad6 was identified as a direct target of miR-374a-5p, and miR-374a-5p had a negative regulatory effect on Smad6 expression. By targeting Smad6, miR-374a-5p inhibited the activation of NLRP3 inflammatory signals in microglia and the subsequent release of pro-inflammatory factors.

SIGNIFICANCE

Our study recognized that miR-374a-5p as a novel regulator of microglial activation in neonatal HIE highlighted potential therapeutic target for the treatment of neonatal hypoxic-ischemic brain injury.

Trophic factors are essential for the survival of grafted oligodendrocyte progenitors and for neuroprotection after perinatal excitotoxicity

The consequences of neonatal white matter injury are devastating and represent a major societal problem as currently there is no cure. Prematurity, low weight birth and maternal pre-natal infection are the most frequent causes of acquired myelin deficiency in the human neonate leading to cerebral palsy and cognitive impairment. In the developing brain, oligodendrocyte (OL) maturation occurs perinatally, and immature OLs are particularly vulnerable. Cell replacement therapy is often considered a viable option to replace progenitors that die due to glutamate excitotoxicity. We previously reported directed specification and mobilization of endogenous committed and uncommitted neural progenitors by the combination of transferrin and insulin growth factor 1 (TSC1). Here, considering cell replacement and integration as therapeutic goals, we examined if OL progenitors (OLPs) grafted into the brain parenchyma of mice that were subjected to an excitotoxic insult could rescue white matter injury. For that purpose, we used a well-established model of glutamate excitotoxic injury. Four-day-old mice received a single intraparenchymal injection of the glutamate receptor agonist N-methyl-D-aspartate alone or in conjunction with TSC1 in the presence or absence of OLPs grafted into the brain parenchyma. Energetics and expression of stress proteins and OL developmental specific markers were examined. A comparison of the proteomic profile per treatment was also ascertained. We found that OLPs did not survive in the excitotoxic environment when grafted alone. In contrast, when combined with TSC1, survival and integration of grafted OLPs was observed. Further, energy metabolism in OLPs was significantly increased by N-methyl-D-aspartate and modulated by TSC1. The proteomic profile after the various treatments showed elevated ubiquitination and stress/heat shock protein 90 in response to N-methyl-D-aspartate. These changes were reversed in the presence of TSC1 and ubiquitination was decreased. The results obtained in this pre-clinical study indicate that the use of a combinatorial intervention including both trophic support and healthy OLPs constitutes a promising approach for long-term survival and successful graft integration. We established optimal conditioning of the host brain environment to promote long-term survival and integration of grafted OLPs into an inflamed neonate host brain. Experimental procedures were performed under the United States Public Health Service Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care Committee at (UCLA) (ARC #1992-034-61) on July 1, 2010.

Unfolded protein response in myelin disorders

Activation of the unfolded protein response in response to endoplasmic reticulum stress preserves cell viability and function under stressful conditions. Nevertheless, persistent, unresolvable activation of the unfolded protein response can trigger apoptosis to eliminate stressed cells. Recent studies show that the unfolded protein response plays an important role in the pathogenesis of various disorders of myelin, including multiples sclerosis, Charcot-Marie-Tooth disease, Pelizaeus-Merzbacher disease, vanishing white matter disease, spinal cord injury, tuberous sclerosis complex, and hypoxia-induced perinatal white matter injury. In this review we summarize the current literature on the unfolded protein response and the evidence for its role in the pathogenesis of myelin disorders.

Corpus callosum microstructural and macrostructural abnormalities in schizophrenia according to the stage of disease

Corpus callosum (CC) volume and surface (macrostructural) studies remain controversial and have not considered the illness duration (ID) systematically. Regardless of ID, some CC macrostructural studies have shown no difference between SZ patients and healthy controls (HC), whereas others have reported macrostructural abnormalities in SZ. Conversely, CC microstructural studies are more in agreement with alterations in CC integrity regardless of the patients' ID, but the direction and degree of these abnormalities over time remain unknown. Moreover, no study has explored both the micro- and macrostructure of the CC in SZ by considering the stage of disease. Both CC micro- and macrostructural data were investigated in 43 SZ patients and compared between two patient groups (21 patients with a short ID and 22 with a long ID) and HC (23 participants) using diffusion tensor and structural imaging. CC microstructural alterations were detected in both SZ groups compared to the HC group, without differences between the SZ groups. In contrast, CC macrostructural alterations were only found in the long ID group. CC microstructural alterations might be detected in schizophrenia at an early stage, without an increase of magnitude thereafter, while CC macrostructural alterations might become apparent at later stages of the illness.

MiRNA-210 induces microglial activation and regulates microglia-mediated neuroinflammation in neonatal hypoxic-ischemic encephalopathy

Neuroinflammation is a major contributor to secondary neuronal injury that accounts for a significant proportion of final brain cell loss in neonatal hypoxic-ischemic encephalopathy (HIE). However, the immunological mechanisms that underlie HIE remain unclear. MicroRNA-210 (miR-210) is the master "hypoxamir" and plays a key role in hypoxic-ischemic tissue damage. Herein, we report in an animal model of neonatal rats that HIE significantly upregulated miR-210 expression in microglia in the neonatal brain and strongly induced activated microglia. Intracerebroventricular administration of miR-210 antagomir effectively suppressed microglia-mediated neuroinflammation and significantly reduced brain injury caused by HIE. We demonstrated that miR-210 induced microglial M1 activation partly by targeting SIRT1, thereby reducing the deacetylation of the NF-κB subunit p65 and increasing NF-κB signaling activity. Thus, our study identified miR-210 as a novel regulator of microglial activation in neonatal HIE, highlighting a potential therapeutic target in the treatment of infants with hypoxic-ischemic brain injury.

A machine learning investigation of volumetric and functional MRI abnormalities in adults born preterm

Imaging studies have characterized functional and structural brain abnormalities in adults after premature birth, but these investigations have mostly used univariate methods that do not account for hypothesized interdependencies between brain regions or quantify accuracy in identifying individuals. To overcome these limitations, we used multivariate machine learning to identify gray matter volume (GMV) and amplitude of low frequency fluctuations (ALFF) brain patterns that best classify young adults born very preterm/very low birth weight (VP/VLBW; n = 94) from those born full-term (FT; n = 92). We then compared the spatial maps of the structural and functional brain signatures and validated them by assessing associations with clinical birth history and basic cognitive variables. Premature birth could be predicted with a balanced accuracy of 80.7% using GMV and 77.4% using ALFF. GMV predictions were mediated by a pattern of subcortical and middle temporal reductions and volumetric increases of the lateral prefrontal, medial prefrontal, and superior temporal gyrus regions. ALFF predictions were characterized by a pattern including increases in the thalamus, pre- and post-central gyri, and parietal lobes, in addition to decreases in the superior temporal gyri bilaterally. Decision scores from each classification, assessing the degree to which an individual was classified as a VP/VLBW case, were predicted by the number of days in neonatal hospitalization and birth weight. ALFF decision scores also contributed to the prediction of general IQ, which highlighted their potential clinical significance. Combined, the results clarified previous research and suggested that primary subcortical and temporal damage may be accompanied by disrupted neurodevelopment of the cortex.

Impaired structural connectivity between dorsal attention network and pulvinar mediates the impact of premature birth on adult visual-spatial abilities

The dorsal attention network (DAN), including frontal eye fields and posterior parietal cortices, and its link with the posterior thalamus, contribute to visual-spatial abilities. Very premature birth impairs both visual-spatial abilities and cortico-thalamic structural connectivity. We hypothesized that impaired structural DAN-pulvinar connectivity mediates the effect of very premature birth on adult visual-spatial abilities. Seventy very premature (median age 26.6 years) and 57 mature born adults (median age 26.6 years) were assessed with cognitive tests and diffusion tensor imaging. Perceptual organization (PO) index of the Wechsler Adult Intelligence Scale-III was used as a proxy for visual-spatial abilities, and connection probability maps in the thalamus, derived from probabilistic tractography from the DAN, were used as a proxy for DAN-thalamic connectivity. Premature born adults showed decreases in both PO-index and connection probability from DAN into the pulvinar, with both changes being positively correlated. Moreover, path analysis revealed that DAN-pulvinar connectivity mediates the relationship between very premature birth and PO-index. Results provide evidence for long-term effects of very premature birth on structural DAN-pulvinar connectivity, mediating the effect of prematurity on adult visual-spatial impairments. Data suggest DAN-pulvinar connectivity as a specific target of prognostic and diagnostic procedures for visual-spatial abilities after premature birth.

The Potential of Stem Cell Therapy to Repair White Matter Injury in Preterm Infants: Lessons Learned From Experimental Models

Diffuse white matter injury (dWMI) is a major cause of morbidity in the extremely preterm born infant leading to life-long neurological impairments, including deficits in cognitive, motor, sensory, psychological, and behavioral functioning. At present, no treatment options are clinically available to combat dWMI and therefore exploration of novel strategies is urgently needed. In recent years, the pathophysiology underlying dWMI has slowly started to be unraveled, pointing towards the disturbed maturation of oligodendrocytes (OLs) as a key mechanism. Immature OL precursor cells in the developing brain are believed to be highly sensitive to perinatal inflammation and cerebral oxygen fluctuations, leading to impaired OL differentiation and eventually myelination failure. OL lineage development under normal and pathological circumstances and the process of (re)myelination have been studied extensively over the years, often in the context of other adult and pediatric white matter pathologies such as stroke and multiple sclerosis (MS). Various studies have proposed stem cell-based therapeutic strategies to boost white matter regeneration as a potential strategy against a wide range of neurological diseases. In this review we will discuss experimental studies focusing on mesenchymal stem cell (MSC) therapy to reduce white matter injury (WMI) in multiple adult and neonatal neurological diseases. What lessons have been learned from these previous studies and how can we translate this knowledge to application of MSCs for the injured white matter in the preterm infant? A perspective on the current state of stem cell therapy will be given and we will discuss different important considerations of MSCs including cellular sources, timing of treatment and administration routes. Furthermore, we reflect on optimization strategies that could potentially reinforce stem cell therapy, including preconditioning and genetic engineering of stem cells or using cell-free stem cell products, to optimize cell-based strategy for vulnerable preterm infants in the near future.

Glutamate Transport and Preterm Brain Injury

Preterm birth complications are the leading cause of child death worldwide and a top global health priority. Among the survivors, the risk of life-long disabilities is high, including cerebral palsy and impairment of movement, cognition, and behavior. Understanding the molecular mechanisms of preterm brain injuries is at the core of future healthcare improvements. Glutamate excitotoxicity is a key mechanism in preterm brain injury, whereby the accumulation of extracellular glutamate damages the delicate immature oligodendrocytes and neurons, leading to the typical patterns of injury seen in the periventricular white matter. Glutamate excitotoxicity is thought to be induced by an interaction between environmental triggers of injury in the perinatal period, particularly cerebral hypoxia-ischemia and infection/inflammation, and developmental and genetic vulnerabilities. To avoid extracellular build-up of glutamate, the brain relies on rapid uptake by sodium-dependent glutamate transporters. Astrocytic excitatory amino acid transporter 2 (EAAT2) is responsible for up to 95% of glutamate clearance, and several lines of evidence suggest that it is essential for brain functioning. While in the adult EAAT2 is predominantly expressed by astrocytes, EAAT2 is transiently upregulated in the immature oligodendrocytes and selected neuronal populations during mid-late gestation, at the peak time for preterm brain injury. This developmental upregulation may interact with perinatal hypoxia-ischemia and infection/inflammation and contribute to the selective vulnerability of the immature oligodendrocytes and neurons in the preterm brain. Disruption of EAAT2 may involve not only altered expression but also impaired function with reversal of transport direction. Importantly, elevated EAAT2 levels have been found in the reactive astrocytes and macrophages of human infant post-mortem brains with severe white matter injury (cystic periventricular leukomalacia), potentially suggesting an adaptive mechanism against excitotoxicity. Interestingly, EAAT2 is suppressed in animal models of acute hypoxic-ischemic brain injury at term, pointing to an important and complex role in newborn brain injuries. Enhancement of EAAT2 expression and transport function is gathering attention as a potential therapeutic approach for a variety of adult disorders and awaits exploration in the context of the preterm brain injuries.

Developmental differences in microglia morphology and gene expression during normal brain development and in response to hypoxia-ischemia

BACKGROUND

Neuroinflammation plays an important role in ischemic brain injury and recovery, however the interplay between brain development and the neuroinflammatory response is poorly understood. We previously described age-dependent differences in the microglial response and the effect of microglial inhibition. Here we investigate whether age-dependent microglial responses may be related to pre-injury developmental differences in microglial phenotype.

METHODS

Measures of microglia morphology were quantified using semi-automated software analysis of immunostained sections from postnatal day 2 (P2), P9, P30 and P60 mice using IMARIS. Microglia were isolated from P2, P9, P30 and P60 mice, and expression of markers of classical and alternative microglial activation was assessed, as well as transforming growth factor beta (TGF-β) receptor, Serpine1, Mer Tyrosine Kinase (MerTK), and the suppressor of cytokine signaling (SOCS3). Hypoxia-ischemia (HI) was induced in P9 and P30 mice using unilateral carotid artery ligation and exposure to 10% oxygen for 50 min. Microglia morphology and microglial expression of genes in the TGF-β and MerTK pathways were determined in ipsilateral and contralateral hippocampus.

RESULTS

A progressive and significant increase in microglia branching morphology was seen in all brain regions from P2 to P30. No consistent classical or alternative activation profile was seen in isolated microglia. A clear transition to increased expression of TGF-β and its downstream effector serpine1 was seen between P9 and P30. A similar increase in expression was seen in MerTK and its downstream effector SOCS3. HI resulted in a significant decrease in branching morphology only in the P9 mice, and expression of TGF-β receptor, Serpine1, MerTK, and SOCS3 were elevated in P30 mice compared to P9 post-HI.

CONCLUSION

Microglia maturation is associated with changes in morphology and gene expression, and microglial responses to ischemia in the developing brain differ based on the age at which injury occurs.

Decreased BOLD fluctuations in lateral temporal cortices of premature born adults

Lasting volume reductions in subcortical and temporal-insular cortices after premature birth suggest altered ongoing activity in these areas. We hypothesized altered fluctuations in ongoing neural excitability and activity, as measured by slowly fluctuating blood oxygenation of resting-state functional MRI (rs-fMRI), in premature born adults, with altered fluctuations being linked with underlying brain volume reductions. To investigate this hypothesis, 94 very preterm/very low birth weight (VP/VLBW) and 92 full-term born young adults underwent structural and rs-fMRI data acquisition with voxel-based morphometry and amplitude of low-frequency fluctuations (ALFF) as main outcome measure. In VP/VLBW adults, ALFF was reduced in lateral temporal cortices, and this reduction was positively associated with lower birth weight. Regions of reduced ALFF overlapped with reduced brain volume. On the one hand, ALFF reduction remained after controlling for volume loss, supporting the functional nature of ALFF reductions. On the other hand, ALFF decreases were positively associated with underlying brain volume loss, indicating a relation between structural and functional changes. Furthermore, within the VP/VLBW group, reduced ALFF was associated with reduced IQ, indicating the behavioral relevance of ALFF decreases in temporal cortices. These results demonstrate long-term impact of premature birth on ongoing BOLD fluctuations in lateral temporal cortices, which are linked with brain volume reductions. Data suggest permanently reduced fluctuations in ongoing neural excitability and activity in structurally altered lateral temporal cortices after premature birth.

Enhanced autophagy contributes to excitotoxic lesions in a rat model of preterm brain injury

Cystic periventricular leukomalacia is commonly diagnosed in premature infants, resulting from severe hypoxic-ischemic white matter injury, and also involving some grey matter damage. Very few is known concerning the cell death pathways involved in these types of premature cerebral lesions. Excitotoxicity is a predominant mechanism of hypoxic-ischemic injury in the developing brain. Concomitantly, it has been recently shown that autophagy could be enhanced in excitotoxic conditions switching this physiological intracellular degradation system to a deleterious process. We here investigated the role of autophagy in a validated rodent model of preterm excitotoxic brain damage mimicking in some aspects cystic periventricular leukomalacia. An excitotoxic lesion affecting periventricular white and grey matter was induced by injecting ibotenate, a glutamate analogue, in the subcortical white matter (subcingulum area) of five-day old rat pups. Ibotenate enhanced autophagy in rat brain dying neurons at 24 h as shown by increased presence of autophagosomes (increased LC3-II and LC3-positive dots) and enhanced autophagic degradation (SQSTM1 reduction and increased number and size of lysosomes (LAMP1- and CATHEPSIN B-positive vesicles)). Co-injection of the pharmacological autophagy inhibitor 3-methyladenine prevented not only autophagy induction but also CASPASE-3 activation and calpain-dependent cleavage of SPECTRIN 24 h after the insult, thus providing a strong reduction of the long term brain injury (16 days after ibotenate injection) including lateral ventricle dilatation, decreases in cerebral tissue volume and in subcortical white matter thickness. The autophagy-dependent neuroprotective effect of 3-methyladenine was confirmed in primary cortical neuronal cultures using not only pharmacological but also genetic autophagy inhibition of the ibotenate-induced autophagy. Strategies inhibiting autophagy could then represent a promising neuroprotective approach in the context of severe preterm brain injuries.

The p38α MAPK Deletion in Oligodendroglia does not Attenuate Myelination Defects in a Mouse Model of Periventricular Leukomalacia

Periventricular leukomalacia (PVL) is a severe type of white matter damage in premature infants and the most common cause of cerebral palsy. It is generally known to be caused by hypoxia and inflammation. Currently there is no effective treatment available, in part due to that the pathogenesis of the disease has not been well understood. The p38α mitogen-activated protein kinase (MAPK) is the serine/threonine kinase and several in vitro studies demonstrated that p38 MAPK is essential for oligodendroglial differentiation and myelination. Indeed, our nerve/glial antigen 2 (NG2)-specific oligodendroglial p38α MAPK conditional knockout (CKO) mice revealed its complex roles in myelination and remyelination. To identify the specific in vivo roles of oligodendroglial p38α MAPK in PVL, we generated a mouse PVL model by combination of LPS-mediated inflammation and hypoxia-ischemia in NG2-p38α MAPK CKO mice. Our results demonstrate that a selective deletion of p38α MAPK in oligodendrocyte did not attenuate myelination defects in the mouse model of PVL. Myelination phenotype revealed by MBP immunostaining was not significantly affected in the p38α MAPK CKO mice compared to the wildtype after PVL induction. The electron microscopic images demonstrated that the microstructure of myelin structures was not significantly different between the wild-type and p38α MAPK CKO mice. In addition, oligodendrocyte degeneration in the corpus callosum white matter area was unaffected in the p38α MAPK CKO during and after the PVL induction. These data indicate that p38α MAPK in oligodendrocyte has minimal effect on myelination and oligodendrocyte survival in the mouse PVL model.

Targeting Sentinel Proteins and Extrasynaptic Glutamate Receptors: a Therapeutic Strategy for Preventing the Effects Elicited by Perinatal Asphyxia?

Perinatal asphyxia (PA) is a relevant cause of death at the time of labour, and when survival is stabilised, associated with short- and long-term developmental disabilities, requiring inordinate care by health systems and families. Its prevalence is high (1 to 10/1000 live births) worldwide. At present, there are few therapeutic options, apart from hypothermia, that regrettably provides only limited protection if applied shortly after the insult.PA implies a primary and a secondary insult. The primary insult relates to the lack of oxygen, and the secondary one to the oxidative stress triggered by re-oxygenation, formation of reactive oxygen (ROS) and reactive nitrogen (RNS) species, and overactivation of glutamate receptors and mitochondrial deficiencies. PA induces overactivation of a number of sentinel proteins, including hypoxia-induced factor-1α (HIF-1α) and the genome-protecting poly(ADP-ribose) polymerase-1 (PARP-1). Upon activation, PARP-1 consumes high amounts of ATP at a time when this metabolite is scarce, worsening in turn the energy crisis elicited by asphyxia. The energy crisis also impairs ATP-dependent transport, including glutamate re-uptake by astroglia. Nicotinamide, a PARP-1 inhibitor, protects against the metabolic cascade elicited by the primary stage, avoiding NAD+ exhaustion and the energetic crisis. Upon re-oxygenation, however, oxidative stress leads to nuclear translocation of the NF-κB subunit p65, overexpression of the pro-inflammatory cytokines IL-1β and TNF-α, and glutamate-excitotoxicity, due to impairment of glial-glutamate transport, extracellular glutamate overflow, and overactivation of NMDA receptors, mainly of the extrasynaptic type. This leads to calcium influx, mitochondrial impairment, and inactivation of antioxidant enzymes, increasing further the activity of pro-oxidant enzymes, thereby making the surviving neonate vulnerable to recurrent metabolic insults whenever oxidative stress is involved. Here, we discuss evidence showing that (i) inhibition of PARP-1 overactivation by nicotinamide and (ii) inhibition of extrasynaptic NMDA receptor overactivation by memantine can prevent the short- and long-term consequences of PA. These hypotheses have been evaluated in a rat preclinical model of PA, aiming to identify the metabolic cascades responsible for the long-term consequences induced by the insult, also assessing postnatal vulnerability to recurrent oxidative insults. Thus, we present and discuss evidence demonstrating that PA induces long-term changes in metabolic pathways related to energy and oxidative stress, priming vulnerability of cells with both the neuronal and the glial phenotype. The effects induced by PA are region dependent, the substantia nigra being particularly prone to cell death. The issue of short- and long-term consequences of PA provides a framework for addressing a fundamental issue referred to plasticity of the CNS, since the perinatal insult triggers a domino-like sequence of events making the developing individual vulnerable to recurrent adverse conditions, decreasing his/her coping repertoire because of a relevant insult occurring at birth.

Reactive astrocyte COX2-PGE2 production inhibits oligodendrocyte maturation in neonatal white matter injury

Inflammation is a major risk factor for neonatal white matter injury (NWMI), which is associated with later development of cerebral palsy. Although recent studies have demonstrated maturation arrest of oligodendrocyte progenitor cells (OPCs) in NWMI, the identity of inflammatory mediators with direct effects on OPCs has been unclear. Here, we investigated downstream effects of pro-inflammatory IL-1β to induce cyclooxygenase-2 (COX2) and prostaglandin E2 (PGE2) production in white matter. First, we assessed COX2 expression in human fetal brain and term neonatal brain affected by hypoxic-ischemic encephalopathy (HIE). In the developing human brain, COX2 was expressed in radial glia, microglia, and endothelial cells. In human term neonatal HIE cases with subcortical WMI, COX2 was strongly induced in reactive astrocytes with "A2" reactivity. Next, we show that OPCs express the EP1 receptor for PGE2, and PGE2 acts directly on OPCs to block maturation in vitro. Pharmacologic blockade with EP1-specific inhibitors (ONO-8711, SC-51089), or genetic deficiency of EP1 attenuated effects of PGE2. In an IL-1β-induced model of NWMI, astrocytes also exhibit "A2" reactivity and induce COX2. Furthermore, in vivo inhibition of COX2 with Nimesulide rescues hypomyelination and behavioral impairment. These findings suggest that neonatal white matter astrocytes can develop "A2" reactivity that contributes to OPC maturation arrest in NWMI through induction of COX2-PGE2 signaling, a pathway that can be targeted for neonatal neuroprotection.

White Matter Injury of Prematurity: Its Mechanisms and Clinical Features

A developing central nervous system is vulnerable to various insults such as infection and ischemia. While increased understanding of the dynamic nature of brain development allows a deeper insight into the pathophysiology of perinatal brain injury, the precise nature of specific fetal and neonatal brain injuries and their short- and long-term clinical consequences need special attention and further elucidation. The current review will describe the pathophysiological aspects and clinical significance of white matter injury of prematurity, a main form of perinatal brain injury in premature newborns, with a particular emphasis on its potential antenatal components.

The Integrated Stress Response in Hypoxia-Induced Diffuse White Matter Injury

Currently no treatments exist for preterm infants with diffuse white matter injury (DWMI) caused by hypoxia. Due to the improved care of preterm neonates and increased recognition by advanced imaging techniques, the prevalence of DWMI is increasing. A better understanding of the pathophysiology of DWMI is therefore of critical importance. The integrated stress response (ISR), a conserved eukaryotic response to myriad stressors including hypoxia, may play a role in hypoxia-induced DWMI and may represent a novel target for much needed therapies. In this study, we use in vitro and in vivo hypoxic models of DWMI to investigate whether the ISR is involved in DWMI. We demonstrate that hypoxia activates the ISR in primary mouse oligodendrocyte precursor cells (OPCs) in vitro and that genetically inhibiting the ISR in differentiating OPCs increases their susceptibility to in vitro hypoxia. We also show that a well established in vivo mild chronic hypoxia (MCH) mouse model and a new severe acute hypoxia (SAH) mouse model of DWMI activates the initial step of the ISR. Nonetheless, genetic inhibition of the ISR has no detectable effect on either MCH- or SAH-induced DWMI. In addition, we demonstrate that genetic enhancement of the ISR does not ameliorate MCH- or SAH-induced DWMI. These studies suggest that, while the ISR protects OPCs from hypoxia in vitro, it does not appear to play a major role in either MCH- or SAH-induced DWMI and is therefore not a likely target for therapies aimed at improving neurological outcome in preterm neonates with hypoxia-induced DWMI.SIGNIFICANCE STATEMENT Diffuse white matter injury (DWMI) caused by hypoxia is a leading cause of neurological deficits following premature birth. An increased understanding of the pathogenesis of this disease is critical. The integrated stress response (ISR) is activated by hypoxia and protects oligodendrocyte lineage cells in other disease models. This has led to an interest in the potential role of the ISR in DWMI. Here we examine the ISR in hypoxia-induced DWMI and show that while the ISR protects oligodendrocyte lineage cells from hypoxia in vitro, genetic inhibition or enhancement of the ISR has no effect on hypoxia-induced DWMI in vivo, suggesting that the ISR does not play a major role in and is not a likely therapeutic target for DWMI.

Reduced Cholinergic Basal Forebrain Integrity Links Neonatal Complications and Adult Cognitive Deficits After Premature Birth

BACKGROUND

Prematurely born individuals have an increased risk for long-term neurocognitive impairments. In animal models, development of the cholinergic basal forebrain (cBF) is selectively vulnerable to adverse effects of perinatal stressors, and impaired cBF integrity results in lasting cognitive deficits. We hypothesized that cBF integrity is impaired in prematurely born individuals and mediates adult cognitive impairments associated with prematurity.

METHODS

We used magnetic resonance imaging-based volumetric assessments of a cytoarchitectonically defined cBF region of interest to determine differences in cBF integrity between 99 adults who were born very preterm and/or with very low birth weight and 106 term-born control subjects from the same birth cohort. Magnetic resonance imaging-derived cBF volumes were studied in relation to neonatal clinical complications after delivery and intelligence measures (IQ) in adulthood.

RESULTS

In adults who were born very preterm and/or with very low birth weight, cBF volumes were significantly reduced compared with term-born adults (-4.5% [F_1,202 = 11.82, p = .001]). Lower cBF volume in adults who were born very preterm and/or with very low birth weight was specifically associated with both neonatal complications (r_part,92 = -.35, p < .001) and adult IQ (r_part,88 = .33, p = .001) even after controlling for global gray matter and white matter volume. In a path analytic model, cBF volume significantly mediated the association between neonatal complications and adult cognitive deficits.

CONCLUSIONS

We provide first-time evidence in humans that cBF integrity is impaired after premature birth and links neonatal complications with long-term cognitive outcome. Data suggest that cholinergic system abnormalities may play a relevant role for long-term neurocognitive impairments associated with premature delivery.

Alterations in white matter microstructure are associated with goal-directed upper-limb movement segmentation in children born extremely preterm

Altered white matter microstructure is commonly found in children born preterm (PT), especially those born at an extremely low gestational age (GA). These children also commonly show disturbed motor function. This study explores the relation between white matter alterations and upper-limb movement segmentation in 41 children born PT (19 girls), and 41 children born at term (18 girls) at 8 years. The PT group was subdivided into extremely PT (E-PT; GA = 25-27 weeks, N = 10), very PT (V-PT; GA = 28-32 weeks, N = 13), and moderately PT (M-PT; GA = 33-35 weeks, N = 18). Arm/hand preference (preferred/non-preferred) was determined through object interactions and the brain hemispheres were designated accordingly. White matter alterations were assessed using diffusion tensor imaging in nine areas, and movement segmentation of the body-parts head, shoulder, elbow, and wrist were registered during a unimanual goal-directed task. Increased movement segmentation was demonstrated consistently on the preferred side in the E-PT group compared with the term born group. Also compared with the term born peers, the E-PT group demonstrated reduced fractional anisotropy (FA) in the cerebral peduncle (targeting the corticospinal tract) in the hemisphere on the non-preferred side and in the splenium of corpus callosum. In contrast, in the anterior internal capsule on the preferred side, the E-PT group had increased FA. Lower FA in the cerebral peduncle, but higher FA in the anterior internal capsule, was associated with increased movement segmentation across body-parts in a contralateral manner. The results suggest that impaired development of sensorimotor tracts in E-PT children could explain a sub-optimal spatiotemporal organization of upper-limb movements. Hum Brain Mapp 38:5051-5068, 2017. © 2017 Wiley Periodicals, Inc.