Neurobiology of periventricular leukomalacia in the premature infant

The Beneficial Effects of Melatonin Administration Following Hypoxia-Ischemia in Preterm Fetal Sheep

Melatonin (MLT) is an endogenous hormone that controls circadian cycle. MLT has additional important properties that make it appealing as a neuroprotective agent—it is a potent anti-oxidant, with anti-apoptotic and anti-inflammatory properties. MLT is safe for administration during pregnancy or to the newborn after birth, and can reduce white matter brain injury under conditions of chronic fetal hypoxia. Accordingly, in the current study, we examined whether an intermediate dose of MLT could restore white matter brain development when administered after an acute hypoxic ischemic (HI) insult in preterm fetal sheep. Fifteen fetal sheep at 95–98 days gestation were instrumented with femoral artery and vein catheters, and a silastic cuff placed around the umbilical cord. At 102 days gestation, the cuff was inflated, causing complete umbilical cord occlusion for 25 min in 10 fetuses, to induce acute severe HI. Five HI fetuses received intravenous MLT for 24 h beginning at 2 h after HI. The remaining five fetuses were administered saline alone. Ten days after HI, the fetal brain was collected from each animal and white and gray matter neuropathology assessed. HI caused a significant increase in apoptotic cell death (TUNEL+), activated microglia (Iba-1+), and oxidative stress (8-OHdG+) within the subventricular and subcortical white matter. HI reduced the total number of oligodendrocytes and CNPase+ myelin density. MLT administration following HI decreased apoptosis, inflammation and oxidative stress within the white matter. MLT had intermediate benefits for the developing white matter: it increased oligodendrocyte cell number within the periventricular white matter only, and improved CNPase+ myelin density within the subcortical but not the striatal white matter. MLT administration following HI was also associated with improved neuronal survival within the cortex. Neuropathology in preterm infants is complex and mediated by multiple mechanisms, including inflammation, oxidative stress and apoptotic pathways. Treatment with MLT presents a safe approach to neuroprotective therapy in preterm infants but appears to have brain region-specific benefits within the white matter.

The extent of intrauterine growth restriction determines the severity of cerebral injury and neurobehavioural deficits in rodents

Background

Cerebral Palsy (CP) is the most common physical pediatric neurodevelopmental disorder and spastic diplegic injury is its most frequent subtype. CP results in substantial neuromotor and cognitive impairments that have significant socioeconomic impact. Despite this, its underlying pathophysiological mechanisms and etiology remain incompletely understood. Furthermore, there is a need for clinically relevant injury models, which a) reflect the heterogeneity of the condition and b) can be used to evaluate new translational therapies. To address these key knowledge gaps, we characterized a chronic placental insufficiency (PI) model, using bilateral uterine artery ligation (BUAL) of dams. This injury model results in intrauterine growth restriction (IUGR) in pups, and animals recapitulate the human phenotype both in terms of neurobehavioural and anatomical deficits.

Methods

Effects of BUAL were studied using luxol fast blue (LFB)/hematoxylin & eosin (H&E) staining, immunohistochemistry, quantitative Magnetic Resonance Imaging (MRI), and Catwalk neurobehavioural tests.

Results

Neuroanatomical analysis revealed regional ventricular enlargement and corpus callosum thinning in IUGR animals, which was correlated with the extent of growth restriction. Olig2 staining revealed reductions in oligodendrocyte density in white and grey matter structures, including the corpus callosum, optic chiasm, and nucleus accumbens. The caudate nucleus, along with other brain structures such as the optic chiasm, internal capsule, septofimbrial and lateral septal nuclei, exhibited reduced size in animals with IUGR. The size of the pretectal nucleus was reduced only in moderately injured animals. MAG/NF200 staining demonstrated reduced myelination and axonal counts in the corpus callosum of IUGR animals. NeuN staining revealed changes in neuronal density in the hippocampus and in the thickness of hippocampal CA2 and CA3 regions. Diffusion weighted imaging (DWI) revealed regional white and grey matter changes at 3 weeks of age. Furthermore, neurobehavioural testing demonstrated neuromotor impairments in animals with IUGR in paw intensities, swing speed, relative print positions, and phase dispersions.

Conclusions

We have characterized a rodent model of IUGR and have demonstrated that the neuroanatomical and neurobehavioural deficits mirror the severity of the IUGR injury. This model has the potential to be applied to examine the pathobiology of and potential therapeutic strategies for IUGR-related brain injury. Thus, this work has potential translational relevance for the study of CP.

Association between perinatal hypoxic-ischemia and periventricular leukomalacia in preterm infants: A systematic review and meta-analysis

Background

Although investigators have implicated hypoxic-ischemia (HI) as a potential cause of periventricular leukomalacia (PVL), the role of clinical risk factors or markers for HI in the development of PVL remains controversial. The aim of this study was to identify perinatal HI-related factors associated with PVL.

Method

The PubMed, EMBASE, and Cochrane Library databases were searched. The last search was performed on January 2017. Summary effect estimates (pooled odds ratios [ORs]) were calculated for each risk factor using fixed or random effects models with tests for heterogeneity and publication bias.

Results

Fifteen studies with a total of 12,851 participants were included in this meta-analysis, and 14 potential risk factors were analyzed. The pooled results showed that mothers with oligohydramnios (OR, 1.55; 95% confidence interval [CI], 1.05 to 2.30), preterm infants with acidemia (OR, 1.87; 95% CI, 1.18 to 2.97), 1-minute Apgar score <7 (OR 2.69; 95% CI, 1.13 to 6.41), 5-minute Apgar score <7 (OR, 1.89; 95% CI, 1.39 to 2.56), apnea (OR, 1.76; 95% CI, 1.07 to 2.90), respiratory distress syndrome (OR, 1.46; 95% CI, 1.04 to 2.03), and seizures (OR, 4.60; 95% CI, 2.84 to 7.46) were associated with increased risk of PVL.

Conclusion

This study identified perinatal HI-related risk factors for the development of PVL in preterm infants. Future large-scale prospective clinical studies are required to validate and extend these findings.

Oligodendrocytes: Functioning in a Delicate Balance Between High Metabolic Requirements and Oxidative Damage

The study of the metabolic interactions between myelinating glia and the axons they ensheath has blossomed into an area of research much akin to the elucidation of the role of astrocytes in tripartite synapses (Tsacopoulos and Magistretti in J Neurosci 16:877-885, 1996). Still, unlike astrocytes, rich in cytochrome-P450 and other anti-oxidative defense mechanisms (Minn et al. in Brain Res Brain Res Rev 16:65-82, 1991; Wilson in Can J Physiol Pharmacol. 75:1149-1163, 1997), oligodendrocytes can be easily damaged and are particularly sensitive to both hypoxia and oxidative stress, especially during their terminal differentiation phase and while generating myelin sheaths. In the present review, we will focus in the metabolic complexity of oligodendrocytes, particularly during the processes of differentiation and myelin deposition, and with a specific emphasis in the context of oxidative stress and the intricacies of the iron metabolism of the most iron-loaded cells of the central nervous system (CNS).

Delivery room resuscitation and adverse outcomes among very low birth weight preterm infants

OBJECTIVE

To evaluate risk factors and impact of delivery room cardiopulmonary resuscitation (DR-CPR) on very low birth weight (VLBW) preterm infants.

STUDY DESIGN

A national, population-based, observational study evaluating risk factors and short-term neonatal outcomes associated with DR-CPR among VLBW, extremely preterm infants (EPIs, 24 to 27 weeks' gestation) and very preterm infants (VPI, 28 to 31 weeks' gestation) born in 1995 to 2010.

RESULTS

Among 17 564 VLBW infants, 636 (3.6%) required DR-CPR. In the group of 6478 EPI, 412 (6.4%) received DR-CPR compared with 224 of 11 086 infants (2.0%) in the VPI group. EPI who underwent DR-CPR had higher odds ratios (ORs (95% confidence interval)) for mortality compared to EPI not requiring DR-CPR (OR 3.32 (2.58, 4.29)), grades 3 to 4 intraventricular hemorrhage (IVH) (OR 1.59 (1.20, 2.10)) and periventricular leukomalacia (OR 1.81 (1.17, 2.82)). DR-CPR among VPI was associated with higher ORs for mortality (OR 4.99 (3.59, 6.94)), early sepsis (OR 2.07 (1.05, 4.09)), grades 3 to 4 IVH (OR 3.74 (2.55, 5.50)) and grades 3 to 4 retinopathy of prematurity (ROP) (OR 2.53 (1.18, 5.41)) compared to VPI not requiring DR-CPR. Only 11% of infants in the EPI DR-CPR group had favorable outcomes compared with 44% in the VPI DR-CPR group. Significantly higher ORs for mortality, IVH and ROP were found in the VPI compared to the EPI group.

CONCLUSION

Preterm VLBW infants requiring DR-CPR were at increased risk of adverse outcomes compared to those not requiring CPR. This effect was more pronounced in the VPI group.

The Paradoxical Effects of Chronic Intra-Amniotic Ureaplasma parvum Exposure on Ovine Fetal Brain Development

Chorioamnionitis is associated with adverse neurodevelopmental outcomes in preterm infants. Ureaplasma spp. are the microorganisms most frequently isolated from the amniotic fluid of women diagnosed with chorioamnionitis. However, controversy remains concerning the role of Ureaplasma spp. in the pathogenesis of neonatal brain injury. We hypothesize that reexposure to an inflammatory trigger during the perinatal period might be responsible for the variation in brain outcomes of preterms following Ureaplasma-driven chorioamnionitis. To investigate these clinical scenarios, we performed a detailed multimodal study in which ovine neurodevelopmental outcomes were assessed following chronic intra-amniotic Ureaplasma parvum (UP) infection either alone or combined with subsequent lipopolysaccharide (LPS) exposure. We show that chronic intra-amniotic UP exposure during the second trimester provoked a decrease in astrocytes, increased oligodendrocyte numbers, and elevated 5-methylcytosine levels. In contrast, short-term LPS exposure before preterm birth induced increased microglial activation, myelin loss, elevation of 5-hydroxymethylcytosine levels, and lipid profile changes. These LPS-induced changes were prevented by chronic preexposure to UP (preconditioning). These data indicate that chronic UP exposure has dual effects on preterm brain development in utero. On the one hand, prolonged UP exposure causes detrimental cerebral changes that may predispose to adverse postnatal clinical outcomes. On the other, chronic intra-amniotic UP exposure preconditions the brain against a second inflammatory hit. This study demonstrates that microbial interactions and the timing and duration of the inflammatory insults determine the effects on the fetal brain. Therefore, this study helps to understand the complex and diverse postnatal neurological outcomes following UP driven chorioamnionitis.

Ultrasonographic Characteristics of Cortical Sulcus Development in the Human Fetus between 18 and 41 Weeks of Gestation

Background:

Fetal brain development is a complicated process that continues throughout pregnancy. Fetal sulcus development has typical morphological features. Assessment of fetal sulcus development to understand the cortical maturation and development by prenatal ultrasound has become widespread. This study aimed to explore a reliable method to assess cortical sulcus and to describe the normal sonographic features of cortical sulcus development in the human fetus between 18 and 41 weeks of gestation.

Methods:

A cross-sectional study was designed to examine the fetal cortical sulcus development at 18–41 weeks of gestation. Ultrasound was used to examine the insula, sylvian fissure (SF), parieto-occipital fissure (POF), and calcarine fissure (CF). Bland-Altman plots were used for assessing the concordance, and the intraclass correlation coefficient was used for assessing the reliability.

Results:

SF images were successfully obtained in 100% of participants at 22 weeks of gestation, while the POF images and CF images could be obtained in 100% at 23 weeks of gestation and 24 weeks of gestation, respectively. The SF width, temporal lobe depth, POF depth, and the CF depth increased with the developed gestation. The width of uncovered insula and the POF angle decreased with the developed gestation. By 23 weeks of gestation, the insula was beginning to be covered. Moreover, it completed at 35 weeks of gestation. The intra- and inter-observer agreements showed consistent reproducibility.

Conclusions:

This study defined standard views of the fetal sulcus as well as the normal reference ranges of these sulcus measurements between 18 and 41 weeks of gestation. Such ultrasonographic measurements could be used to identify fetuses at risk of fetal neurological structural disorders.

Does growth restriction increase the vulnerability to acute ventilation-induced brain injury in newborn lambs? Implications for future health and disease

Fetal growth restriction (FGR) and preterm birth are frequent co-morbidities, both are independent risks for brain injury. However, few studies have examined the mechanisms by which preterm FGR increases the risk of adverse neurological outcomes. We aimed to determine the effects of prematurity and mechanical ventilation (VENT) on the brain of FGR and appropriately grown (AG, control) lambs. We hypothesized that FGR preterm lambs are more vulnerable to ventilation-induced acute brain injury. FGR was surgically induced in fetal sheep (0.7 gestation) by ligation of a single umbilical artery. After 4 weeks, preterm lambs were euthanized at delivery or delivered and ventilated for 2 h before euthanasia. Brains and cerebrospinal fluid (CSF) were collected for analysis of molecular and structural indices of early brain injury. FGRVENT lambs had increased oxidative cell damage and brain injury marker S100B levels compared with all other groups. Mechanical ventilation increased inflammatory marker IL-8 within the brain of FGRVENT and AGVENT lambs. Abnormalities in the neurovascular unit and increased blood-brain barrier permeability were observed in FGRVENT lambs, as well as an altered density of vascular tight junctions markers. FGR and AG preterm lambs have different responses to acute injurious mechanical ventilation, changes which appear to have been developmentally programmed in utero.

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.

Erythropoietin Protects Against Lipopolysaccharide-Induced Microgliosis and Abnormal Granule Cell Development in the Ovine Fetal Cerebellum

Erythropoietin (EPO) ameliorates inflammation-induced injury in cerebral white matter (WM). However, effects of inflammation on the cerebellum and neuroprotective effects of EPO are unknown. Our aims were to determine: (i) whether lipopolysaccharide (LPS)-induced intrauterine inflammation causes injury to, and/or impairs development of the cerebellum; and (ii) whether recombinant human EPO (rhEPO) mitigates these changes. At 107 ± 1 days gestational age (DGA; ~0.7 of term), fetal sheep received LPS (~0.9 μg/kg; i.v.) or an equivalent volume of saline, followed 1 h later with 5000 IU/kg rhEPO (i.v.) or an equivalent volume of saline (i.v.). This generated the following experimental groups: control (saline + saline; n = 6), LPS (LPS + saline, n = 8) and LPS + rhEPO (n = 8). At necropsy (116 ± 1 DGA; ~0.8 of term) the brain was perfusion-fixed and stained histologically (H&E) and immunostained to identify granule cells (Neuronal Nuclei, NeuN), granule cell proliferation (Ki67), Bergmann glia (glial fibrillary acidic protein, GFAP), astrogliosis (GFAP) and microgliosis (Iba-1). In comparison to controls, LPS fetuses had an increased density of Iba-1-positive microglia (p < 0.005) in the lobular WM; rhEPO prevented this increase (p < 0.05). The thickness of both the proliferative (Ki67-positive) and post-mitotic zones (Ki67-negative) of the EGL were increased in LPS-exposed fetuses compared to controls (p < 0.05), but were not different between controls and LPS + rhEPO fetuses. LPS also increased (p < 0.001) the density of granule cells (NeuN-positive) in the internal granule layer (IGL); rhEPO prevented the increase (p < 0.01). There was no difference between groups in the areas of the vermis (total cross-section), molecular layer (ML), IGL or WM, the density of NeuN-positive granule cells in the ML, the linear density of Bergmann glial fibers, the areal density or somal area of the Purkinje cells, the areal coverage of GFAP-positive astrocytes in the lobular and deep WM, the density of Iba-1-positive microglia in the deep WM or the density of apopotic cells in the cerebellum. LPS-induced intrauterine inflammation caused microgliosis and abnormal development of granule cells. rhEPO ameliorated these changes, suggesting that it is neuroprotective against LPS-induced inflammatory effects in the cerebellum.

Therapeutic use of transferrin to modulate anemia and conditions of iron toxicity

As the main iron transporter, transferrin delivers iron to target tissues like the bone marrow for erythropoiesis. Also, by binding free iron, transferrin prevents formation of reactive oxygen species. Transferrin deficiency due to congenital hypotransferrinemia is characterized by anemia as well as oxidative stress related to toxic free iron. Transferrin supplementation may be beneficial in two ways. First, transferrin can correct anemia by modulating the amount of iron that is available for erythropoiesis. This is obvious for patients that suffer from hypotransferrinemia, but may also have beneficial effects for β-thalassemia patients. Second, under conditions of iron overload, transferrin reduces oxidative stress by binding free iron in the circulation and in tissues. Hereby, transferrin protects the host against the reactive oxygen species that can be formed as a consequence of free iron. This beneficial effect is shown in hematological patients undergoing chemotherapy and stem cell transplantation. Transferrin may also be beneficial in lung injury, ischemia-reperfusion injury and hypomyelination. This review summarizes the preclinical and clinical data on the efficacy of exogenous transferrin administration to modulate certain forms of anemia and to prevent the toxic effects of free iron. Thereby, we show that transferrin has promising therapeutic potential in a wide variety of conditions.

Functional variation of SHP-2 promoter is associated with preterm birth and delayed myelination and motor development in preterm infants

Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP-2) is a cytoplasmic tyrosine phosphatase that is highly expressed in hematopoietic cells and in the CNS and exerts opposite effects on signal transduction by exerting a neuroprotective or proapoptotic effect. Several mutations of SHP-2 have been found in children with myeloproliferative disorders or malignant leukemia, and some of these can affect brain development. In the present study, we aimed to identify and functionally characterize genetic variations in SHP-2 in 72 preterm and 58 full-term infants and to evaluate the effect of the variations on neurodevelopment in preterm infants. Twelve genetic variations were identified. Among them, two variations in the SHP-2 promoter, g.-317C > T and g.-273G > A, were found to significantly increase promoter activity, and the frequency of g.-273G > A was higher in preterm infants than in full-term infants. Two transcription factors, NF-κB and GABPα, were found to be involved in the transcriptional regulation of SHP-2 by the two above-mentioned variations. In particular, we found that g.-273G > A was significantly associated with delayed myelination and poor motor development in preterm infants. Our results suggest that a functional promoter variation in SHP-2 is associated with spontaneous preterm birth itself as well as white matter myelination and neurodevelopment.

The Diastolic Closing Margin Is Associated with Intraventricular Hemorrhage in Premature Infants

Premature infants are at an increased risk of intraventricular hemorrhage (IVH). The roles of hypotension and hyperemia are still debated. Critical closing pressure (CrCP) is the arterial blood pressure (ABP) at which cerebral blood flow (CBF) ceases. When diastolic ABP is equal to CrCP, CBF occurs only during systole. The difference between diastolic ABP and CrCP is the diastolic closing margin (DCM). We hypothesized that a low DCM was associated with IVH. One hundred eighty-six premature infants, with a gestational age (GA) range of 23-33 weeks, were monitored with umbilical artery catheters and transcranial Doppler insonation of middle cerebral artery flow velocity for 1-h sessions over the first week of life. CrCP was calculated linearly and using an impedance model. A multivariate generalized linear regression model was used to determine associations with severe IVH (grades 3-4). An elevated DCM by either method was associated with IVH (p < 0.0001 for the linear method; p < 0.001 for the impedance model). Lower 5-min Apgar scores, elevated mean CBF velocity, and lower mean ABP were also associated with IVH (p < 0.0001). Elevated DCM, not low DCM, was associated with severe IVH in this cohort.

Differing intrinsic biological properties between forebrain and spinal oligodendroglial lineage cells

Differentiation of oligodendroglial progenitor cells (OPCs) into myelinating oligodendrocytes is known to be regulated by the microenvironment where they differentiate. However, current research has not verified whether or not oligodendroglial lineage cells (OLCs) derived from different anatomical regions of the central nervous system (CNS) respond to microenvironmental cues in the same manner. Here, we isolated pure OPCs from rat neonatal forebrain (FB) and spinal cord (SC) and compared their phenotypes in the same in vitro conditions. We found that although FB and SC OLCs responded differently to the same external factors; they were distinct in proliferation response to mitogens, oligodendrocyte phenotype after differentiation, and cytotoxic responses to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-type glutamate receptor-mediated excitotoxicity at immature stages of differentiation in a cell-intrinsic manner. Moreover, transcriptome analysis identified genes differentially expressed between these OPC populations, including those encoding transcription factors (TFs), cell surface molecules, and signaling molecules. Particularly, FB and SC OPCs retained the expression of FB- or SC-specific TFs, such as Foxg1 and Hoxc8, respectively, even after serial passaging in vitro. Given the essential role of these TFs in the regional identities of CNS cells along the rostrocaudal axis, our results suggest that CNS region-specific gene regulation by these TFs may cause cell-intrinsic differences in cellular responses between FB and SC OLCs to extracellular molecules. Further understanding of the regional differences among OPC populations will help to improve treatments for demyelination in different CNS regions and to facilitate the development of stem cell-derived OPCs for cell transplantation therapies for demyelination. Cover Image for this issue: doi. 10.1111/jnc.13809.

Chronic hypoxia alters fetal cerebrovascular responses to endothelin-1

In utero hypoxia influences the structure and function of most fetal arteries, including those of the developing cerebral circulation. Whereas the signals that initiate this hypoxic remodeling remain uncertain, these appear to be distinct from the mechanisms that maintain the remodeled vascular state. The present study explores the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to endothelin-1 (ET-1), a potent vascular contractant and mitogen. In fetal lambs, chronic hypoxia (3,820-m altitude for the last 110 days of gestation) had no significant effect on plasma ET-1 levels or ETA receptor density in cerebral arteries but enhanced contractile responses to ET-1 in an ETA-dependent manner. In organ culture (24 h), 10 nM ET-1 increased medial thicknesses less in hypoxic than in normoxic arteries, and these increases were ablated by inhibition of PKC (chelerythrine) in both normoxic and hypoxic arteries but were attenuated by inhibition of CaMKII (KN93) and p38 (SB203580) in normoxic but not hypoxic arteries. As indicated by Ki-67 immunostaining, ET-1 increased medial thicknesses via hypertrophy. Measurements of colocalization between MLCK and SMαA revealed that organ culture with ET-1 also promoted contractile dedifferentiation in normoxic, but not hypoxic, arteries through mechanisms attenuated by inhibitors of PKC, CaMKII, and p38. These results support the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to ET-1 through pathways dependent upon PKC, CaMKII, and p38 that cause increased ET-1-mediated contractility, decreased ET-1-mediated smooth muscle hypertrophy, and a depressed ability of ET-1 to promote contractile dedifferentiation.

Ultrasound Imaging of Mouse Fetal Intracranial Hemorrhage Due to Ischemia/Reperfusion

Despite vast improvement in perinatal care during the 30 years, the incidence rate of neonatal encephalopathy remains unchanged without any further Progress towards preventive strategies for the clinical impasse. Antenatal brain injury including fetal intracranial hemorrhage caused by ischemia/reperfusion is known as one of the primary triggers of neonatal injury. However, the mechanisms of antenatal brain injury are poorly understood unless better predictive models of the disease are developed. Here we show a mouse model for fetal intracranial hemorrhage in vivo developed to investigate the actual timing of hypoxia-ischemic events and their related mechanisms of injury. Intrauterine growth restriction mouse fetuses were exposed to ischemia/reperfusion cycles by occluding and opening the uterine and ovarian arteries in the mother. The presence and timing of fetal intracranial hemorrhage caused by the ischemia/reperfusion were measured with histological observation and ultrasound imaging. Protein-restricted diet increased the risk of fetal intracranial hemorrhage. The monitoring of fetal brains by ultrasound B-mode imaging clarified that cerebral hemorrhage in the fetal brain occurred after the second ischemic period. Three-dimensional ultrasound power Doppler imaging visualized the disappearance of main blood flows in the fetal brain. These indicate a breakdown of cerebrovascular autoregulation which causes the fetal intracranial hemorrhage. This study supports the fact that the ischemia/reperfusion triggers cerebral hemorrhage in the fetal brain. The present method enables us to noninvasively create the cerebral hemorrhage in a fetus without directly touching the body but with repeated occlusion and opening of the uterine and ovarian arteries in the mother.

Protective Effects of Fetal Zone Steroids Are Comparable to Estradiol in Hyperoxia-Induced Cell Death of Immature Glia

Impaired neurodevelopment in preterm infants is caused by prematurity itself; however, hypoxia/ischemia, inflammation, and hyperoxia contribute to the extent of impairment. Because preterm birth is accompanied by a dramatic decrease in 17β-estradiol (E2) and progesterone, preliminary clinical studies have been carried out to substitute these steroids in preterm infants; however, they failed to confirm significantly improved neurologic outcomes. We therefore hypothesized that the persistently high postnatal production of fetal zone steroids [mainly dehydroepiandrosterone (DHEA)] until term could interfere with E2-mediated protection. We investigated whether E2 could reduce hyperoxia-mediated apoptosis in three immature glial cell types and detected the involved receptors. Thereafter, we investigated protection by the fetal zone steroids DHEA, 16α-hydroxy-DHEA, and androstenediol. For DHEA, the involved receptors were evaluated. We examined aromatases, which convert fetal zone steroids into more estrogenic compounds. Finally, cotreatment was compared against single hormone treatment to investigate synergism. In all cell types, E2 and fetal zone steroids resulted in significant dose-dependent protection, whereas the mediating receptors differed. The neuroprotection by fetal zone steroids highly depended on the cell type-specific expression of aromatases, the receptor repertoire, and the potency of the fetal zone steroids toward these receptors. No synergism in fetal zone steroid and E2 cotreatment was detected in two of three cell types. Therefore, E2 supplementation may not be beneficial with respect to neuroprotection because fetal zone steroids circulate in persistently high concentrations until term in preterm infants. Hence, a refined experimental model for preterm infants is required to investigate potential treatments.

A model of Periventricular Leukomalacia (PVL) in neonate mice with histopathological and neurodevelopmental outcomes mimicking human PVL in neonates

Periventricular leukomalacia (PVL), a brain injury affecting premature infants is commonly associated with cerebral palsy. PVL results from hypoxia-ischemia (HI) with or without infection and is characterized by white matter necrotic lesions, hypomyelination, microglial activation, astrogliosis, and neuronal death. It is important to study a PVL mouse model that mimics human PVL in symptomatology, anatomic and molecular basis. In our neonate mice model, bilateral carotid arteries were temporary ligated at P5 followed by hypoxic exposure (FiO₂ of 8% for 20 min.). At P5 in mice, the white matter is more vulnerable to HI injury than the grey matter. In our PVL model, mice suffer from significant hind limb paresis, incoordination and feeding difficulties. Histologically they present with ventriculomegally, white matter loss, microglial activation and neuronal apoptosis. HI injury increases proinflammtory cytokines, activates NF-kB, activates microglia and causes nitrative stress. All these inflammatory mediators lead to oligodendroglial injury and white matter loss. Neurobehavioral analysis in the PVL mice model at P60 showed that the HI group had a significant decrease in hind limb strength, worsening rotarod testing and worsening performance in the open field test. This new PVL model has great advantages far beyond just mimicking human PVL in clinical features and histopathology. Long term survival, the development of cerebral palsy and the ability of using this model in transgenic animals will increase our understanding of the mechanistic pathways underlying PVL and defining specific targets for the development of suitable therapeutics.

Perinatal Brain Injury As a Consequence of Preterm Birth and Intrauterine Inflammation: Designing Targeted Stem Cell Therapies

Chorioamnionitis is a major cause of preterm birth and brain injury. Bacterial invasion of the chorion and amnion, and/or the placenta, can lead to a fetal inflammatory response, which in turn has significant adverse consequences for the developing fetal brain. Accordingly, there is a strong causal link between chorioamnionitis, preterm brain injury and the pathogenesis of severe postnatal neurological deficits and cerebral palsy. Currently there are no treatments to protect or repair against brain injury in preterm infants born after pregnancy compromised by intrauterine infection. This review describes the injurious cascade of events in the preterm brain in response to a severe fetal inflammatory event. We will highlight specific periods of increased vulnerability, and the potential effects of therapeutic intervention with cell-based therapies. Many clinical trials are underway to investigate the efficacy of stem cells to treat patients with cerebral palsy. Stem cells, obtained from umbilical cord tissue and cord blood, normally discarded after birth, are emerging as a safe and potentially effective therapy. It is not yet known, however, which stem cell type(s) are the most efficacious for administration to preterm infants to treat brain injury-mediated inflammation. Individual stem cell populations found in cord blood and tissue, such as mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs), have a number of potential benefits that may specifically target preterm inflammatory-induced brain injury. MSCs have strong immunomodulatory potential, protecting against global and local neuroinflammatory cascades triggered during infection to the fetus. EPCs have angiogenic and vascular reparative qualities that make them ideal for neurovascular repair. A combined therapy using both MSCs and EPCs to target inflammation and promote angiogenesis for re-establishment of vital vessel networks is a treatment concept that warrants further investigation.

Blocked, delayed, or obstructed: What causes poor white matter development in intrauterine growth restricted infants?

Poor white matter development in intrauterine growth restricted (IUGR) babies remains a major, untreated problem in neonatology. New therapies, guided by an understanding of the mechanisms that underlie normal and abnormal oligodendrocyte development and myelin formation, are required. Much of our knowledge of the mechanisms that underlie impaired myelination come from studies in adult demyelinating disease, preterm brain injury, or experimental models of hypoxia-ischemia. However, relatively less is known for IUGR which is surprising because IUGR is a leading cause of perinatal mortality and morbidity, second only to premature birth. IUGR is also a significant risk factor for the later development of cerebral palsy, and is a greater risk compared to some of the more traditionally researched antecedents - asphyxia and inflammation. Recent evidence suggests that the white matter injury and reduced myelination in the brains of some preterm babies is due to impaired maturation of oligodendrocytes thereby resulting in the reduced capacity to synthesize myelin. Therefore, it is not surprising that the hypomyelination observable in the central nervous system of IUGR infants has similarly lead to investigations identifying a delay or blockade in the progress of maturation of oligodendrocytes in these infants. This review will discuss current ideas thought to account for the poor myelination often present in the neonate's brain following IUGR, and discuss novel interventions that are promising as treatments that promote oligodendrocyte maturation, and thereby repair the myelination deficits that otherwise persist into infancy and childhood and lead to neurodevelopmental abnormalities.

Brain oxygen saturation assessment in neonates using T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy

Although near-infrared spectroscopy is increasingly being used to monitor cerebral oxygenation in neonates, it has a limited penetration depth. The T₂-prepared Blood Imaging of Oxygen Saturation (T₂-BIOS) magnetic resonance sequence provides an oxygen saturation estimate on a voxel-by-voxel basis, without needing a respiratory calibration experiment. In 15 neonates, oxygen saturation measured by T₂-prepared blood imaging of oxygen saturation and near-infrared spectroscopy were compared. In addition, these measures were compared to cerebral blood flow and venous oxygen saturation in the sagittal sinus. A strong linear relation was found between the oxygen saturation measured by magnetic resonance imaging and the oxygen saturation measured by near-infrared spectroscopy ( R²= 0.64, p < 0.001). Strong linear correlations were found between near-infrared spectroscopy oxygen saturation, and magnetic resonance imaging measures of frontal cerebral blood flow, whole brain cerebral blood flow and venous oxygen saturation in the sagittal sinus ( R²= 0.71, 0.50, 0.65; p < 0.01). The oxygen saturation obtained by T₂-prepared blood imaging of oxygen saturation correlated with venous oxygen saturation in the sagittal sinus ( R²= 0.49, p = 0.023), but no significant correlations could be demonstrated with frontal and whole brain cerebral blood flow. These results suggest that measuring oxygen saturation by T₂-prepared blood imaging of oxygen saturation is feasible, even in neonates. Strong correlations between the various methods work as a cross validation for near-infrared spectroscopy and T₂-prepared blood imaging of oxygen saturation, confirming the validity of using of these techniques for determining cerebral oxygenation.

Clinical Risk Factors for Punctate White Matter Lesions on Early Magnetic Resonance Imaging in Preterm Newborns

OBJECTIVE

To identify clinical risk factors for punctate white matter lesions (PWML) on early magnetic resonance imaging (MRI) in 2 cohorts of newborns born extremely preterm in different neonatal centers.

STUDY DESIGN

A total of 250 newborns born preterm at less than 28 weeks of gestation (mean 26.4 ± 1.1 weeks) with an early MRI were identified from 2 neonatal centers, in Vancouver, Canada (cohort A, n = 100) and Utrecht, the Netherlands (cohort B, n = 150). Cohort A was imaged as part of a prospective research study and cohort B was imaged as part of routine clinical care. PWML were defined as cluster type foci of hyperintensity on T1-weighted imaging and were identified at a mean postmenstrual age of 31.1 (±1.9) weeks. Multivariable analysis was used to identify clinical factors predictive of PWML.

RESULTS

Cluster type PWML were found in 47 newborns born extremely preterm (18.8%) and were more common in cohort A (32%) than in cohort B (10%). Newborns in cohort A generally were sicker than those in cohort B. Multivariable analyses revealed that greater birth weight (B = 0.002; P < .02), grade II-III intraventricular hemorrhage (B = 0.83; P < .02), and cohort A (B = 1.34; P < .0001) were independent predictors of PWML.

CONCLUSION

Several risk factors for PWML on early MRI were identified. The interaction among birth weight, intraventricular hemorrhage, and other aspects of postnatal illness as risk factors for PWML warrants further investigation in newborns born extremely preterm and may help to identify modifiable risk factors for PWML.

The Subventricular Zone: A Key Player in Human Neocortical Development

One of the main characteristics of the developing brain is that all neurons and the majority of macroglia originate first in the ventricular zone (VZ), next to the lumen of the cerebral ventricles, and later on in a secondary germinal area above the VZ, the subventricular zone (SVZ). The SVZ is a transient compartment mitotically active in humans for several gestational months. It serves as a major source of cortical projection neurons as well as an additional source of glial cells and potentially some interneuron subpopulations. The SVZ is subdivided into the smaller inner (iSVZ) and the expanded outer SVZ (oSVZ). The enlargement of the SVZ and, in particular, the emergence of the oSVZ are evolutionary adaptations that were critical to the expansion and unique cellular composition of the primate cerebral cortex. In this review, we discuss the cell types and organization of the human SVZ during the first half of the 40 weeks of gestation that comprise intrauterine development. We focus on this period as it is when the bulk of neurogenesis in the human cerebral cortex takes place. We consider how the survival and fate of SVZ cells depend on environmental influences, by analyzing the results from in vitro experiments with human cortical progenitor cells. This in vitro model is a powerful tool to better understand human neocortex formation and the etiology of neurodevelopmental disorders, which in turn will facilitate the design of targeted preventive and/or therapeutic strategies.

Microbes and the Developing Gastrointestinal Tract

During the course of mammalian evolution, there has been a close relationship between microbes residing in the gastrointestinal (GI) tract and the mammalian host. Although the host provides the microbes with a warm environment and nutrients, they, in turn, undergo various metabolic processes that aid the host. The host has developed weapons against microbes that are considered foreign, as well as mechanisms to tolerate and live synergistically with most of the microbes in the GI tract. This relationship is proving to be important not only in the neonatal period and during infancy, but it is becoming increasingly evident that microbial colonization in early life may affect the individual's health throughout life. Here we will review this relationship in terms of health and disease, with a focus on the aspects of this relationship during maturation of the host.

Sirt1 regulates glial progenitor proliferation and regeneration in white matter after neonatal brain injury

Regenerative processes in brain pathologies require the production of distinct neural cell populations from endogenous progenitor cells. We have previously demonstrated that oligodendrocyte progenitor cell (OPC) proliferation is crucial for oligodendrocyte (OL) regeneration in a mouse model of neonatal hypoxia (HX) that reproduces diffuse white matter injury (DWMI) of premature infants. Here we identify the histone deacetylase Sirt1 as a Cdk2 regulator in OPC proliferation and response to HX. HX enhances Sirt1 and Sirt1/Cdk2 complex formation through HIF1α activation. Sirt1 deacetylates retinoblastoma (Rb) in the Rb/E2F1 complex, leading to dissociation of E2F1 and enhanced OPC proliferation. Sirt1 knockdown in culture and its targeted ablation in vivo suppresses basal and HX-induced OPC proliferation. Inhibition of Sirt1 also promotes OPC differentiation after HX. Our results indicate that Sirt1 is an essential regulator of OPC proliferation and OL regeneration after neonatal brain injury. Therefore, enhancing Sirt1 activity may promote OL recovery after DWMI.

Oligodendrocyte progenitor cell (OPC) proliferation is crucial for regeneration after hypoxic lesions in mice, a model of diffuse white matter injury of premature infants. Here, the authors show that the histone deacetylase Sirt1 is a Cdk2-dependent mediator of OPC proliferation and OPC response to hypoxia.

Mortality and Morbidity of Extremely Low Birth Weight Infants in the Mainland of China: A Multi-center Study

BACKGROUND

With the progress of perinatal medicine and neonatal technology, more and more extremely low birth weight (ELBW) survived all over the world. This study was designed to investigate the short-term outcomes of ELBW infants during their Neonatal Intensive Care Unit (NICU) stay in the mainland of China.

METHODS

All infants admitted to 26 NICUs with a birth weight (BW) < l000 g were included between January l, 2011 and December 31, 2011. All the data were collected retrospectively from clinical records by a prospectively designed questionnaire. The data collected from each NICU transmitted to the main institution where the results were aggregated and analyzed. Categorical variables were performed with Pearson Chi-square test. Binary Logistic regression analysis was used to detect risk factors.

RESULTS

A total of 258 ELBW infants were admitted to 26 NICUs, of whom the mean gestational age (GA) was 28.1 ± 2.2 weeks, and the mean BW was 868 ± 97 g. The overall survival rate at discharge was 50.0%. Despite aggressive treatment 60 infants (23.3%) died and another 69 infants (26.7%) died after medical care withdrawal. Furthermore, the survival rate was significantly higher in coastal areas than inland areas (53.6% vs. 35.3%, P = 0.019). BW < 750 g and GA < 28 weeks were the largest risk factors, and being small for gestational age was a protective factor related to mortality. Respiratory distress syndrome was the most common complication. The incidence of patent ductus arteriosus, intraventricular hemorrhage, periventricular leukomalacia, bronchopulmonary dysplasia, retinopathy of prematurity was 26.2%, 33.7%, 6.7%, 48.1%, and 41.4%, respectively. Ventilator associated pneumonia was the most common hospital acquired infection during hospitalization.

CONCLUSIONS

Our study was the first survey that revealed the present status of ELBW infants in the mainland of China. The mortality and morbidity of ELBW infants remained high as compared to other developed countries.

Human Amnion Epithelial Cells Protect Against White Matter Brain Injury After Repeated Endotoxin Exposure in the Preterm Ovine Fetus

Intrauterine inflammation is a significant cause of injury to the developing fetal brain. Using a preterm fetal sheep model of in utero infection, we asked whether human amnion epithelial cells (hAECs) were able to reduce inflammation-induced fetal brain injury. Surgery was undertaken on pregnant sheep at ∼105 days gestation (term is 147 days) for implantation of vascular catheters. Lipopolysaccharide (LPS; 150 ng/kg bolus) or saline was administered IV at 109, 110, and 111 days. Sixty million fluorescent-labeled hAECs were administered at 110, 111, and 112 days gestation via the brachial artery catheter. Brains were collected at 114 days for histological assessment. hAECs were observed within the cortex, white matter, and hippocampus. Compared to control lambs, LPS administration was associated with significant and widespread fetal brain inflammation and injury as evidenced by increased number of activated microglia in the periventricular white matter (p = 0.02), increased pyknosis, cell degeneration (p = 0.01), and a nonsignificant trend of fewer oligodendrocytes in the subcortical and periventricular white matter. Administration of hAECs to LPS-treated animals was associated with a significant mitigation in both inflammation and injury as evidenced by fewer activated microglia (p = 0.03) and pyknotic cells (p = 0.03), significantly more oligodendrocytes in the subcortical and periventricular white matter (p = 0.01 and 0.02, respectively), and more myelin basic protein-positive cells within the periventricular white matter (p = 0.02). hAEC administration to fetal sheep exposed to multiple doses of LPS dampens the resultant fetal inflammatory response and mitigates associated brain injury.

Neonatal Dexamethasone Treatment Exacerbates Hypoxia/Ischemia-Induced White Matter Injury

Dexamethasone, a synthetic glucocorticoid, has been widely used to prevent or ameliorate morbidity of chronic lung disease in preterm infants with respiratory distress syndrome. Despite its beneficial effect on neonatal lung function, growing concern has arisen about adverse effects of this clinical practice on fetal brain development. We demonstrated previously that neonatal dexamethasone (DEX) treatment may render the newborn brain to be more vulnerable to hypoxia/ischemia (HI)-induced gray matter injury. Here, we examined whether neonatal DEX treatment may also affect the extent of HI-induced subcortical white matter (WM) injury in the developing rat brain. Using a HI model of premature brain injury, we demonstrated that a 3-day tapering course (0.5, 0.3, and 0.1 mg/kg) of DEX treatment in rat pups on postnatal days 1-3 (P1-3) significantly reduced the number of all stages of the oligodendroglial lineage cells on P7 and exacerbated HI-induced WM injury. Neonatal DEX treatment also enhanced HI-induced oligodendroglial apoptosis and astrocyte activation in the developing WM on P14. Likewise, HI-induced reductions in myelin thickness, axon caliber, and function during WM development were exacerbated by neonatal DEX treatment. Furthermore, neonatal DEX treatment further aggravated HI-induced motor deficits as assessed in the rotarod test. We also found that the administration of β-lactam antibiotic ceftriaxone increased glutamate transporter-1 protein expression and significantly reduced HI-induced WM injury in neonatal DEX-treated rats. These results suggest that neonatal DEX treatment may lead the developing brain to be more vulnerable to subsequent HI-induced WM injury, which can be ameliorated by ceftriaxone administration.

The Effect of Mild Hypothermia on Insulin-like Growth Factors After Severe Asphyxia in the Preterm Fetal Sheep

OBJECTIVES

Persistent reductions in insulin-like growth factor I (IGF-I) levels in the preterm infant are strongly associated with increased risk of retinopathy and other complications, and may result from exposure to severe hypoxia. The effects of a potential new treatment for hypoxic-ischemic encephalopathy, cerebral hypothermia, on the responses of the IGF axis to hypoxia are unknown. The aim of this study was to examine the effects of prenatal asphyxia and cerebral hypothermia on changes in IGF-I and -II, IGF-binding protein 1 (IGFBP-1), and insulin levels.

METHODS

Fetal sheep at 0.7 of gestation underwent either sham asphyxia and sham cooling (n = 7), asphyxia induced by 25 minutes of complete umbilical cord occlusion alone (n = 8), or asphyxia and head cooling (n = 8, extradural temperature 29.5 +/- 2.6C [vs 39.4 +/- 0.3C; P < .05]). Fetuses were studied for 3 days post-insult, during which time fetal blood samples were taken for endocrine measurements.

RESULTS

There were no IGF axis changes during occlusion. Plasma IGF-I levels significantly decreased between 6 hours and 48 hours after asphyxia and IGF-II levels by 10 hours, in both asphyxia groups. IGFBP-1 rose from 4 hours, reaching a peak at 10 hours and returning to control values by 48 hours in the normothermia group, and by 24 hours in the hypothermia group. Insulin levels decreased between 2 hours and 10 hours after asphyxia in both asphyxia groups, and subsequently normalized.

CONCLUSIONS

This study demonstrates for the first time that transient asphyxia in the preterm sheep fetus is associated with a significant decrease in IGF-II as well as IGF-I during recovery, and that these responses are not altered by mild systemic hypothermia.

Peroxidation of polyunsaturated fatty acids by lipoxygenases drives ferroptosis

Ferroptosis is form of regulated nonapoptotic cell death that is involved in diverse disease contexts. Small molecules that inhibit glutathione peroxidase 4 (GPX4), a phospholipid peroxidase, cause lethal accumulation of lipid peroxides and induce ferroptotic cell death. Although ferroptosis has been suggested to involve accumulation of reactive oxygen species (ROS) in lipid environments, the mediators and substrates of ROS generation and the pharmacological mechanism of GPX4 inhibition that generates ROS in lipid environments are unknown. We report here the mechanism of lipid peroxidation during ferroptosis, which involves phosphorylase kinase G2 (PHKG2) regulation of iron availability to lipoxygenase enzymes, which in turn drive ferroptosis through peroxidation of polyunsaturated fatty acids (PUFAs) at the bis-allylic position; indeed, pretreating cells with PUFAs containing the heavy hydrogen isotope deuterium at the site of peroxidation (D-PUFA) prevented PUFA oxidation and blocked ferroptosis. We further found that ferroptosis inducers inhibit GPX4 by covalently targeting the active site selenocysteine, leading to accumulation of PUFA hydroperoxides. In summary, we found that PUFA oxidation by lipoxygenases via a PHKG2-dependent iron pool is necessary for ferroptosis and that the covalent inhibition of the catalytic selenocysteine in Gpx4 prevents elimination of PUFA hydroperoxides; these findings suggest new strategies for controlling ferroptosis in diverse contexts.

Oxidative Stress Related Diseases in Newborns

We review oxidative stress-related newborn disease and the mechanism of oxidative damage. In addition, we outline diagnostic and therapeutic strategies and future directions. Many reports have defined oxidative stress as an imbalance between an enhanced reactive oxygen/nitrogen species and the lack of protective ability of antioxidants. From that point of view, free radical-induced damage caused by oxidative stress seems to be a probable contributing factor to the pathogenesis of many newborn diseases, such as respiratory distress syndrome, bronchopulmonary dysplasia, periventricular leukomalacia, necrotizing enterocolitis, patent ductus arteriosus, and retinopathy of prematurity. We share the hope that the new understanding of the concept of oxidative stress and its relation to newborn diseases that has been made possible by new diagnostic techniques will throw light on the treatment of those diseases.

Intranasal surfactant protein D as neuroprotective rescue in a neonatal rat model of periventricular leukomalacia

BACKGROUND

Periventricular leukomalacia (PVL) is the leading cause of neurocognitive deficits in children with prematurity. We previously hypothesized that surfactant protein D (SPD) with its ability to bind toll-like receptors may have a possible ameliorating effect in PVL.

METHODS

Three groups were defined as: LPS-administered and postnatal intranasal saline administered group, LPS-administered and postnatal intranasal SPD-treated group, and control group. Twenty-eight offspring rats were reared with their dams until their sacrifice for histological evaluation on day 7.

RESULTS

A significant loss of brain weight occurred in the LPS group compared with controls. The postnatal intranasal SPD treatment significantly reduced the number of TUNEL-positive cells in the periventricular white matter as compared with the LPS-treated group. Compared with the control group, LPS injection in the rat brain significantly reduced the MBP-positive staining. Postnatal SPD treatment greatly prevented LPS-stimulated loss of MBP staining.

CONCLUSIONS

Present study demonstrated a neuroprotective effect of SPD in a rat model of PVL. Our results offer future implications towards increasing our understanding about multifactorial mechanisms underlying periventricular leukomalacia and developing plausible therapeutic strategies in order to prevent neurocognitive deficits in preterm infants.

The Role of Prematurity in Patients With Hemiplegic Cerebral Palsy

A multicenter retrospective study was conducted to investigate the perinatal factors, imaging findings and clinical characteristics of hemiplegic cerebral palsy with a particular focus on children born prematurely. Our cohort included 135 patients of whom 42% were born prematurely; 16% were extreme premature infants who were born at 30 weeks or earlier. Nineteen (14%) were twins. Right hemiplegia was slightly more common and accounted for 59% of the patients. Imaging findings of intraventricular hemorrhage and periventricular leukomalacia were more prevalent in premature children whereas stroke, porencephaly, cerebral hemorrhage and cerebral atrophy were more evenly distributed in both term-born and prematurely-born children (p< 0.01). The overall prevalence of epilepsy in the cohort was 26% with no differences in full-term compared to prematurely-born children. Regardless of the gestational birth age, intellectual deficits were more common in the presence of comorbidity of both hemiplegia and epilepsy (p< 0.05).

Rodent Hypoxia-Ischemia Models for Cerebral Palsy Research: A Systematic Review

Cerebral palsy (CP) is a complex multifactorial disorder, affecting approximately 2.5-3/1000 live term births, and up to 22/1000 prematurely born babies. CP results from injury to the developing brain incurred before, during, or after birth. The most common form of this condition, spastic CP, is primarily associated with injury to the cerebral cortex and subcortical white matter as well as the deep gray matter. The major etiological factors of spastic CP are hypoxia/ischemia (HI), occurring during the last third of pregnancy and around birth age. In addition, inflammation has been found to be an important factor contributing to brain injury, especially in term infants. Other factors, including genetics, are gaining importance. The classic Rice-Vannucci HI model (in which 7-day-old rat pups undergo unilateral ligation of the common carotid artery followed by exposure to 8% oxygen hypoxic air) is a model of neonatal stroke that has greatly contributed to CP research. In this model, brain damage resembles that observed in severe CP cases. This model, and its numerous adaptations, allows one to finely tune the injury parameters to mimic, and therefore study, many of the pathophysiological processes and conditions observed in human patients. Investigators can recreate the HI and inflammation, which cause brain damage and subsequent motor and cognitive deficits. This model further enables the examination of potential approaches to achieve neural repair and regeneration. In the present review, we compare and discuss the advantages, limitations, and the translational value for CP research of HI models of perinatal brain injury.

Consumption of broccoli sprouts during late gestation and lactation confers protection against developmental delay induced by maternal inflammation

BACKGROUND

The presence of a fetal inflammatory response is linked to cerebral palsy. Unfortunately no preventive therapies are available. In this study, we determined whether dietary supplementation with broccoli sprouts (BrSp), a phase-II enzyme inducer, would be effective in preventing the behavioural and pathologic manifestations in a rodent model of inflammation during late pregnancy.

METHODS

Pregnant Long-Evans rats were administered i.p. Injections of saline (100μl) or lipopolysaccharide (LPS, 200μg/kg), every 12h on embryonic day (E) 19 and 20. In the treatment groups, dams were supplemented with 200mg/day of dried BrSp from E14 until postnatal day 21. Pups underwent a series of neurodevelopmental reflex tests from postnatal day 3-21 followed by neuropathological analyses.

RESULTS

Pups born from the LPS group were significantly growth restricted (p<0.001) and delayed in hindlimb placing (p<0.05), cliff avoidance (p<0.05), and gait (p<0.001) compared to controls. In the open field behaviour analyses, LPS pups had an increase in grooming behaviour (p<0.05) and a decreased amount of time spent in the center of the box compared to controls. Dietary supplementation with BrSp to offspring exposed to LPS had increased birth weights (p<0.001), were no longer delayed in acquiring hindlimb placing, cliff avoidance, gait, and posture, and groomed less compared to LPS alone pups (p<0.01). Histological analyses revealed that LPS pups had reduced myelin basic protein compared to controls.

CONCLUSIONS

Our data suggest that BrSp dietary supplementation during pregnancy may be effective in preventing growth restriction and neurodevelopmental delays.

Ketamine decreases inflammatory and immune pathways after transient hypoxia in late gestation fetal cerebral cortex

Transient hypoxia in pregnancy stimulates a physiological reflex response that redistributes blood flow and defends oxygen delivery to the fetal brain. We designed the present experiment to test the hypotheses that transient hypoxia produces damage of the cerebral cortex and that ketamine, an antagonist of NMDA receptors and a known anti‐inflammatory agent, reduces the damage. Late gestation, chronically catheterized fetal sheep were subjected to a 30‐min period of ventilatory hypoxia that decreased fetal PaO₂ from 17 ± 1 to 10 ± 1 mmHg, or normoxia (PaO₂ 17 ± 1 mmHg), with or without pretreatment (10 min before hypoxia/normoxia) with ketamine (3 mg/kg, i.v.). One day (24 h) after hypoxia/normoxia, fetal cerebral cortex was removed and mRNA extracted for transcriptomics and systems biology analysis (n = 3–5 per group). Hypoxia stimulated a transcriptomic response consistent with a reduction in cellular metabolism and an increase in inflammation. Ketamine pretreatment reduced both of these responses. The inflammation response modeled with transcriptomic systems biology was validated by immunohistochemistry and showed increased abundance of microglia/macrophages after hypoxia in the cerebral cortical tissue that ketamine significantly reduced. We conclude that transient hypoxia produces inflammation of the fetal cerebral cortex and that ketamine, in a standard clinical dose, reduces the inflammation response.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of Sex and Mild Intrainsult Hypothermia on Neuropathology and Neural Reorganization following Neonatal Hypoxic Ischemic Brain Injury in Rats

Hypoxia ischemia (HI) is a recognized risk factor among late-preterm infants, with HI events leading to varied neuropathology and cognitive/behavioral deficits. Studies suggest a sex difference in the incidence of HI and in the severity of subsequent behavioral deficits (with better outcomes in females). Mechanisms of a female advantage remain unknown but could involve sex-specific patterns of compensation to injury. Neuroprotective hypothermia is also used to ameliorate HI damage and attenuate behavioral deficits. Though currently prescribed only for HI in term infants, cooling has potential intrainsult applications to high-risk late-preterm infants as well. To address this important clinical issue, we conducted a study using male and female rats with a postnatal (P) day 7 HI injury induced under normothermic and hypothermic conditions. The current study reports patterns of neuropathology evident in postmortem tissue. Results showed a potent benefit of intrainsult hypothermia that was comparable for both sexes. Findings also show surprisingly different patterns of compensation in the contralateral hemisphere, with increases in hippocampal thickness in HI females contrasting reduced thickness in HI males. Findings provide a framework for future research to compare and contrast mechanisms of neuroprotection and postinjury plasticity in both sexes following a late-preterm HI insult.

Apoptosis of Oligodendrocytes during Early Development Delays Myelination and Impairs Subsequent Responses to Demyelination

During mammalian development, myelin-forming oligodendrocytes are generated and axons ensheathed according to a tightly regulated sequence of events. Excess premyelinating oligodendrocytes are eliminated by apoptosis and the timing of the onset of myelination in any specific CNS region is highly reproducible. Although the developing CNS recovers more effectively than the adult CNS from similar insults, it is unknown whether early loss of oligodendrocyte lineage cells leads to long-term functional deficits. To directly assess whether the loss of oligodendrocytes during early postnatal spinal cord development impacted oligodendrogenesis, myelination, and remyelination, transgenic mouse lines were generated in which a modified caspase-9 molecule allowed spatial and temporal control of the apoptotic pathway specifically in mature, myelin basic protein expressing oligodendrocytes (MBP-iCP9). Activating apoptosis in MBP(+) cells of the developing spinal cord during the first postnatal week inhibited myelination. This inhibition was transient, and the levels of myelination largely returned to normal after 2 weeks. Despite robust developmental plasticity, MBP-iCP9-induced oligodendrocyte apoptosis compromised the rate and extent of adult remyelination. Remyelination failure correlated with a truncated proliferative response of oligodendrocyte progenitor cells, suggesting that depleting the oligodendrocyte pool during critical developmental periods compromises the regenerative response to subsequent demyelinating lesions.

SIGNIFICANCE STATEMENT

This manuscript demonstrates that early insults leading to oligodendrocyte apoptosis result in the impairment of recovery from demyelinating diseases in the adult. These studies begin to provide an initial understanding of the potential failure of recovery in insults, such as periventricular leukomalacia and multiple sclerosis.

COX-1 and COX-2 polymorphisms in susceptibility to cerebral palsy in very preterm infants

Cerebral palsy (CP) is a nonprogressive motor disorder caused by white matter damage in the developing brain. Recent epidemiological and clinical data suggest intrauterine infection/inflammation as the most common cause of preterm delivery and neonatal complications, including CP. Cyclooxygenases are key enzymes in the conversion of arachidonic acid to prostaglandins. The COX family consists of two isoforms, COX-1 and COX-2. In the brain, COX-2 is constitutively expressed at high levels on pyramidal neurons, while COX-1 is predominantly expressed by microglia and can be upregulated in pathological conditions, such as infection, ischemia and traumatic brain injury. Single nucleotide polymorphisms in the COX-1 and COX-2 gene could have profound effects on COX-1 and COX-2 expression and, directly or indirectly, influence the pathogenesis, development and severity of CP. In this study we investigated the association between single nucleotide polymorphisms of the COX-1 and COX-2 gene and susceptibility to cerebral palsy in very preterm infants. The results of our study showed the association between COX-1 high expression genotype (-842 AA) and COX-1 high expression allele -842A and risk of CP in infants with cystic periventricular leucomalacia (cPVL). Our results support an important role of COX-1 enzyme on microglial activation during neuroinflammation resulting in huge neuroinflammatory response and the proinflammatory mediator overproduction, with the serious white matter damage and CP development as a consequence.

Prenatal Systemic Hypoxia-Ischemia and Oligodendroglia Loss in Cerebellum

Hypoxic-ischemic (HI) injury is an important cause of death and disabilities. Despite all improvements in neonatal care, the number of children who suffer some kind of injury during birth has remained stable in the last decade. A great number of studies have shown alterations in neural cells and many animal models have been proposed in the last 5 decades. Robinson et al. (2005) proposed an HI model in which the uterine arteries are temporarily clamped on the 18th gestation day. The findings were quite similar to the ones observed in postmortem studies. The white matter is clearly damaged, and a great amount of astrogliosis takes place both in the gray and white matters. Motor changes were also found but no data regarding the cerebellum, an important structure related to motor performance, was presented. Using this model, we have shown an increased level of iNOS at P0 and microgliosis and astrogliosis at P9, and astrogliosis at P23 (up to 4 weeks from the insult). NO is important in migration, maturation, and synaptic plasticity, but in exacerbated levels it may also contribute to cellular and tissue damage. We have also evaluated oligodendroglia development in the cerebellum. At P9 in HI animals, we found a decrease in the number of PDGFRα+ cells and an apparent delay in myelination, suggesting a failure in oligodendroglial progenitors migration/maturation and/or in the myelination process. These results point to an injury in cerebellar development that might help to explain the motor problems in HI.

Can the Assessment of Spontaneous Oscillations by Near Infrared Spectrophotometry Predict Neurological Outcome of Preterm Infants?

The aim was to assess the correlation between cerebral autoregulation and outcome. Included were 31 preterm infants, gestational age 26 1/7 to 32 2/7 and <24 h life. Coherence between cerebral total haemoglobin (tHb) or oxygenation index (OI) measured by near-infrared spectrophotometry (NIRS) and systemic heart rate (HR) or arterial blood pressure (MAP) was calculated as a measure of autoregulation. In contrast to previous studies, low coherences in the first 24 h were significantly associated with intraventricular haemorrhage, death or abnormal neurodevelopmental outcome at 18 months or later. We suggest that our results can be explained by the concept of a multi-oscillatory-functions-order.