Postnatal infection is associated with widespread abnormalities of brain development in premature newborns

Infection-induced inflammation and cerebral injury in preterm infants

Preterm birth and infectious diseases are the most common causes of neonatal and early childhood deaths worldwide. The rates of preterm birth have increased over recent decades and account for 11% of all births worldwide. Preterm infants are at significant risk of severe infection in early life and throughout childhood. Bacteraemia, inflammation, or both during the neonatal period in preterm infants is associated with adverse outcomes, including death, chronic lung disease, and neurodevelopmental impairment. Recent studies suggest that bacteraemia could trigger cerebral injury even without penetration of viable bacteria into the CNS. Here we review available evidence that supports the concept of a strong association between bacteraemia, inflammation, and cerebral injury in preterm infants, with an emphasis on the underlying biological mechanisms, clinical correlates, and translational opportunities.

Neonatal systemic inflammation in rats alters retinal vessel development and simulates pathologic features of retinopathy of prematurity

Background

Alteration of retinal angiogenesis during development leads to retinopathy of prematurity (ROP) in preterm infants, which is a leading cause of visual impairment in children. A number of clinical studies have reported higher rates of ROP in infants who had perinatal infections or inflammation, suggesting that exposure of the developing retina to inflammation may disturb retinal vessel development. Thus, we investigated the effects of systemic inflammation on retinal vessel development and retinal inflammation in neonatal rats.

Methods

To induce systemic inflammation, we intraperitoneally injected 100 μl lipopolysaccharide (LPS, 0.25 mg/ml) or the same volume of normal saline in rat pups on postnatal days 1, 3, and 5. The retinas were extracted on postnatal days 7 and 14, and subjected to assays for retinal vessels, inflammatory cells and molecules, and apoptosis.

Results

We found that intraperitoneal injection of LPS impaired retinal vessel development by decreasing vessel extension, reducing capillary density, and inducing localized overgrowth of abnormal retinal vessels and dilated peripheral vascular ridge, all of which are characteristic findings of ROP. Also, a large number of CD11c⁺ inflammatory cells and astrocytes were localized in the lesion of abnormal vessels. Further analysis revealed that the number of major histocompatibility complex (MHC) class II^loCD68^loCD11b^loCD11c^hi cells in the retina was higher in LPS-treated rats compared to controls. Similarly, the levels of TNF-α, IL-1β, and IL-12a were increased in LPS-treated retina. Also, apoptosis was increased in the inner retinal layer where retinal vessels are located.

Conclusions

Our data demonstrate that systemic LPS-induced inflammation elicits retinal inflammation and impairs retinal angiogenesis in neonatal rats, implicating perinatal inflammation in the pathogenesis of ROP.

PDA ligation and health outcomes: a meta-analysis

BACKGROUND AND OBJECTIVE

Patent ductus arteriosus (PDA) ligation has been variably associated with neonatal morbidities and neurodevelopmental impairment (NDI). The objective was to systematically review and meta-analyze the impact of PDA ligation in preterm infants at <32 weeks' gestation on the risk of mortality, severe neonatal morbidities, and NDI in early childhood.

METHODS

Medline, Embase, Cochrane Central Register of Controlled Trials, Education Resources Information Centre (ERIC), Cumulative Index to Nursing and Allied Health (CINAHL), PsycINFO, and the Dissertation database were searched (1947 through August 2013). Risk of bias was assessed by using the Newcastle-Ottawa Scale and the Cochrane Risk of Bias tool. Meta-analyses were performed by using a random-effects model. Unadjusted and adjusted odds ratios (aORs) with 95% confidence intervals (CIs) were pooled when appropriate.

RESULTS

Thirty-nine cohort studies and 1 randomized controlled trial were included. Nearly all cohort studies had at least moderate risk of bias mainly due to failure to adjust for survival bias and important postnatal preligation confounders such as ventilator dependence, intraventricular hemorrhage, and sepsis. Compared with medical treatment, surgical ligation was associated with increases in NDI (aOR: 1.54; 95% CI: 1.01-2.33), chronic lung disease (aOR: 2.51; 95% CI: 1.98-3.18), and severe retinopathy of prematurity (aOR: 2.23; 95% CI: 1.62-3.08) but with a reduction in mortality (aOR: 0.54; 95% CI: 0.38-0.77). There was no difference in the composite outcome of death or NDI in early childhood (aOR: 0.95; 95% CI: 0.58-1.57).

CONCLUSIONS

Surgical ligation of PDA is associated with reduced mortality, but surviving infants are at increased risk of NDI. However, there is a lack of studies addressing survival bias and confounding by indication.

Brain injury in premature neonates: A primary cerebral dysmaturation disorder?

With advances in neonatal care, preterm neonates are surviving with an evolving constellation of motor and cognitive disabilities that appear to be related to widespread cellular maturational disturbances that target cerebral gray and white matter. Whereas preterm infants were previously at high risk for destructive brain lesions that resulted in cystic white matter injury and secondary cortical and subcortical gray matter degeneration, contemporary cohorts of preterm survivors commonly display less severe injury that does not appear to involve pronounced glial or neuronal loss. Nevertheless, these milder forms of injury are also associated with reduced cerebral growth. Recent human and experimental studies support that impaired cerebral growth is related to disparate responses in gray and white matter. Myelination disturbances in cerebral white matter are related to aberrant regeneration and repair responses to acute death of premyelinating late oligodendrocyte progenitors (preOLs). In response to preOL death, early oligodendrocyte progenitors rapidly proliferate and differentiate, but the regenerated preOLs fail to normally mature to myelinating cells required for white matter growth. Although immature neurons appear to be more resistant to cell death from hypoxia-ischemia than glia, they display widespread disturbances in maturation of their dendritic arbors, which further contribute to impaired cerebral growth. These complex and disparate responses of neurons and preOLs thus result in large numbers of cells that fail to fully mature during a critical window in development of neural circuitry. These recently recognized forms of cerebral gray and white matter dysmaturation raise new diagnostic challenges and suggest new therapeutic directions centered on reversal of the processes that promote dysmaturation.

Invasive procedures in preterm children: brain and cognitive development at school age

BACKGROUND

Very preterm infants (born 24-32 weeks' gestation) undergo numerous invasive procedures during neonatal care. Repeated skin-breaking procedures in rodents cause neuronal cell death, and in human preterm neonates higher numbers of invasive procedures from birth to term-equivalent age are associated with abnormal brain development, even after controlling for other clinical risk factors. It is unknown whether higher numbers of invasive procedures are associated with long-term alterations in brain microstructure and cognitive outcome at school age in children born very preterm.

METHODS

Fifty children born very preterm underwent MRI and cognitive testing at median age 7.6 years (interquartile range, 7.5-7.7). T1- and T2-weighted images were assessed for the severity of brain injury. Magnetic resonance diffusion tensor sequences were used to measure fractional anisotropy (FA), an index of white matter (WM) maturation, from 7 anatomically defined WM regions. Child cognition was assessed using the Wechsler Intelligence Scale for Children-IV. Multivariate modeling was used to examine relationships between invasive procedures, brain microstructure, and cognition, adjusting for clinical confounders (eg, infection, ventilation, brain injury).

RESULTS

Greater numbers of invasive procedures were associated with lower FA values of the WM at age 7 years (P = .01). The interaction between the number of procedures and FA was associated with IQ (P = .02), such that greater numbers of invasive procedures and lower FA of the superior WM were related to lower IQ.

CONCLUSIONS

Invasive procedures during neonatal care contribute to long-term abnormalities in WM microstructure and lower IQ.

That chorioamnionitis is a risk factor for bronchopulmonary dysplasia--the case against

Bronchopulmonary dysplasia (BPD) is the most frequent long term sequelae in infants born at less than 29 weeks of gestational age (GA) and histological chorioamnionitis (CA) is the most frequent condition associated with very preterm birth. Numerous studies have explored the association between BPD and CA with conflicting results. This inconsistency may be attributable to differences in populations, definitions, methods, and whether potential confounding factors such as GA, antenatal steroids, and post natal events were considered. A recent systematic review and meta-analysis shows some evidence of an association between BPD and CA; however, results adjusting for important confounders show more conservative measures of association. In addition, there was evidence of publication bias: when controlling for publication bias the results were more conservative and adjusted results were no longer significant. Recent large cohort studies not included in the systematic review do not support the belief that CA is associated with an increased risk of BPD. Despite a large body of evidence, CA cannot be definitively considered a risk factor for BPD.

Brain development in preterm infants assessed using advanced MRI techniques

Infants who are born preterm have a high incidence of neurocognitive and neurobehavioral abnormalities, which may be associated with impaired brain development. Advanced magnetic resonance imaging (MRI) approaches, such as diffusion MRI (d-MRI) and functional MRI (fMRI), provide objective and reproducible measures of brain development. Indices derived from d-MRI can be used to provide quantitative measures of preterm brain injury. Although fMRI of the neonatal brain is currently a research tool, future studies combining d-MRI and fMRI have the potential to assess the structural and functional properties of the developing brain and its response to injury.

Chorioamnionitis in the pathogenesis of brain injury in preterm infants

Chorioamnionitis (or placental infection) is suspected to be a risk factor for brain injury in premature infants. The suggested association between chorioamnionitis and cystic periventricular leukomalacia and cerebral palsy is uncertain because of the variability of study designs and definitions of chorioamnionitis. Improvements in neonatal intensive care may have attenuated the impact of chorioamnionitis on brain health outcomes. Large multicenter studies using rigorous definitions of chorioamnionitis on placental pathologies and quantitative magnetic resonance techniques may offer the optimal way to clarify the complex role of chorioamnionitis in modifying brain health and long-term outcomes.

Neonatal E. coli infection causes neuro-behavioral deficits associated with hypomyelination and neuronal sequestration of iron

Recent evidence indicates that inflammatory insults in neonates significantly influenced white matter development and caused behavioral deficits that manifest in young adulthood. The mechanisms underlying these developmental and behavioral complications, however, are not well understood. We hypothesize that acute brain inflammation caused by neonatal infection reduces the bioavailability of iron required for oligodendrocyte maturation and white matter development. Here, we confirm that peripheral Escherichia coli infection in neonates at postnatal day 3 (P3) caused acute brain inflammation that was resolved within 72 h. Nonetheless, transient early life infection (ELI) profoundly influenced behavior, white matter development, and iron homeostasis in the brain. For instance, mice exposed to E. coli as neonates had increased locomotor activity and impaired motor coordination as juveniles (P35) and young adults (P60). In addition, these behavioral deficits were associated with marked hypomyelination and a reduction of oligodendrocytes in subcortical white matter and motor cortex. Moreover, ELI altered transcripts related to cellular sequestration of iron in the brain including hepcidin, ferroportin, and L-ferritin. For example, ELI increased hepcidin mRNA and decreased ferroportin mRNA and protein in the brain at P4, which preceded increased L-ferritin mRNA at P12. Consistent with the mRNA results, L-ferritin protein was robustly increased at P12 specifically in neurons of E. coli infected mice. We interpret these data to indicate that neonatal infection causes significant neuronal sequestration of iron at a time point before myelination. Together, these data indicate a possible role for aberrant neuronal iron storage in neonatal infection-induced disturbances in myelination and behavior.

Abnormal brain maturation in preterm neonates associated with adverse developmental outcomes

OBJECTIVE

Our objective was to determine the association of early brain maturation with neurodevelopmental outcome in premature neonates.

METHODS

Neonates born between 24 and 32 weeks' gestation (April 2006 to August 2010) were prospectively studied with MRI early in life and again at term-equivalent age. Using diffusion tensor imaging and magnetic resonance spectroscopic imaging, fractional anisotropy (FA) (microstructure) and N-acetylaspartate (NAA)/choline (metabolism) were measured from the basal nuclei, white matter tracts, and superior white matter. Brain maturation is characterized by increasing FA and NAA/choline from early in life to term-equivalent age. In premature neonates, systemic illness and critical care therapies have been linked to abnormalities of these measures. Of the 177 neonates in this cohort, 5 died and 157 (91% of survivors) were assessed at 18 months' corrected age (adjusted for prematurity) using the Bayley Scales of Infant and Toddler Development III motor, cognitive, and language composite scores (mean = 100, SD = 15).

RESULTS

Among these 157 infants, white matter injury was seen in 48 (30%). Severe white matter injury, in 10 neonates (6%), was associated with a decrease in motor (-18 points; p < 0.001) and cognitive (-8 points; p = 0.085) scores. With greater severity of adverse neurodevelopmental outcomes, slower increases in FA and NAA/choline were observed in the basal nuclei and brain white matter regions as neonates matured to term-equivalent age, independent of the presence of white matter injury.

CONCLUSIONS

In the preterm neonate, abnormal brain maturation evolves through the period of neonatal intensive care and is associated with adverse neurodevelopmental outcomes.

Slower postnatal growth is associated with delayed cerebral cortical maturation in preterm newborns

Slower postnatal growth is an important predictor of adverse neurodevelopmental outcomes in infants born preterm. However, the relationship between postnatal growth and cortical development remains largely unknown. Therefore, we examined the association between neonatal growth and diffusion tensor imaging measures of microstructural cortical development in infants born very preterm. Participants were 95 neonates born between 24 and 32 weeks gestational age studied twice with diffusion tensor imaging: scan 1 at a median of 32.1 weeks (interquartile range, 30.4 to 33.6) and scan 2 at a median of 40.3 weeks (interquartile range, 38.7 to 42.7). Fractional anisotropy and eigenvalues were recorded from 15 anatomically defined cortical regions. Weight, head circumference, and length were recorded at birth and at the time of each scan. Growth between scans was examined in relation to diffusion tensor imaging measures at scans 1 and 2, accounting for gestational age, birth weight, sex, postmenstrual age, known brain injury (white matter injury, intraventricular hemorrhage, and cerebellar hemorrhage), and neonatal illness (patent ductus arteriosus, days intubated, infection, and necrotizing enterocolitis). Impaired weight, length, and head growth were associated with delayed microstructural development of the cortical gray matter (fractional anisotropy: P < 0.001), but not white matter (fractional anisotropy: P = 0.529), after accounting for prenatal growth, neonatal illness, and brain injury. Avoiding growth impairment during neonatal care may allow cortical development to proceed optimally and, ultimately, may provide an opportunity to reduce neurological disabilities related to preterm birth.

Diffusion magnetic resonance imaging in preterm brain injury

INTRODUCTION

White matter injury and abnormal maturation are thought to be major contributors to the neurodevelopmental disabilities observed in children and adolescents who were born preterm. Early detection of abnormal white matter maturation is important in the design of preventive, protective, and rehabilitative strategies for the management of the preterm infant. Diffusion-weighted magnetic resonance imaging (d-MRI) has become a valuable tool in assessing white matter maturation and injury in survivors of preterm birth. In this review, we aim to (1) describe the basic concepts of d-MRI; (2) evaluate the methods that are currently used to analyse d-MRI; (3) discuss neuroimaging correlates of preterm brain injury observed at term corrected age; during infancy, adolescence and in early adulthood; and (4) explore the relationship between d-MRI measures and subsequent neurodevelopmental performance.

METHODS

References for this review were identified through searches of PubMed and Google Scholar before March 2013.

RESULTS

The impact of premature birth on cerebral white matter can be observed from term-equivalent age through to adulthood. Disruptions to white matter development, identified by d-MRI, are related to diminished performance in functional domains including motor performance, cognition and behaviour in early childhood and in later life.

CONCLUSION

d-MRI is an effective tool for investigating preterm white matter injury. With advances in image acquisition and analysis approaches, d-MRI has the potential to be a biomarker of subsequent outcome and to evaluate efficacy of clinical interventions in this population.

Structure and function: how to connect?

INTRODUCTION

The majority, but not all, of very preterm-born infants have difficulties with a variety of cognitive functions as children. It is critical to be able to predict as early as possible those who will have difficulties, to be able to direct appropriate interventions.

METHODS

We are conducting multimodal structural and functional MRI studies in very preterm-born infants and following them with behavioural and neuroimaging assessments until 4 years of age. We are also completing structural and more complex functional imaging in school-aged very preterm-born children.

RESULTS

A number of MRI measures between preterm and term age correlate with outcome at 2 years of age. Functional and structural differences are also seen at school age; examples from these various studies are presented.

CONCLUSION

Structural and functional studies in preterm-born versus term-born infants and children, particularly if completed longitudinally, provide important information on the evolution of brain-behaviour correlates and can help predict outcome in this high-risk population.

Resuscitation intensity at birth is associated with changes in brain metabolic development in preterm neonates

INTRODUCTION

Intensive resuscitation at birth has been linked to intraventricular haemorrhage (IVH) in the preterm neonate. However, the impact of less intensive resuscitation on more subtle alterations in brain metabolic development is largely unknown. Our objective was to determine the relationship between the intensity of neonatal resuscitation following preterm birth on brain metabolic development.

METHODS

One hundred thirty-three very preterm-born neonates (median gestational age [GA] 27 ± 2 weeks) underwent MR spectroscopic imaging early in life (median postmenstrual age 32 weeks) and again at term-equivalent age (median 40 weeks). Severity of white matter injury, IVH and cerebellar haemorrhage on magnetic resonance imaging were scored. Ratios of N-acetylaspartate (NAA) and lactate to choline (Cho) were calculated in eight regions of interest and were assessed in relation to intensiveness of resuscitation strategy (bag and mask, continuous positive airway pressure [CPAP], intubation, cardiopulmonary resuscitation [CPR]).

RESULTS

Within the first hour of life, 14 newborns had no intervention, 3 received bag and mask, 30 had CPAP, 79 were intubated and 7 had CPR. Resuscitated infants were more likely to have IVH (p = 0.02). More intensive resuscitation was associated with decreased NAA/Cho maturation (p < 0.001, adjusting for birth GA). Metabolic development was similar in neonates requiring CPAP in comparison to those receiving no intervention. The change in lactate/Cho did not differ across resuscitation categories (p = 0.8).

CONCLUSIONS

Intensity of resuscitation at birth is related to changes in metabolic brain development from early in life to term-equivalent age. Results suggest that preventing the need for intensive neonatal resuscitation may provide an opportunity to improve brain development in preterm neonates.

Neonatal infection and 5-year neurodevelopmental outcome of very preterm infants

OBJECTIVE

To determine whether neonatal infections are associated with a higher risk of adverse neurodevelopment at 5 years of age in a population-based cohort of very preterm children.

METHODS

We included all live births between 22 and 32 weeks of gestation, from 9 regions in France, in 1997 (EPIPAGE study). Of the 2665 live births, 2277 were eligible for a follow-up evaluation at 5 years of age: 1769 had a medical examination and 1495 underwent cognitive assessment. Cerebral palsy and cognitive impairment were studied as a function of early-onset sepsis (EOS) and late-onset sepsis (LOS), after adjustment for potential confounding factors, in multivariate logistic regression models.

RESULTS

A total of 139 (5%) of the 2665 live births included in the study presented with EOS alone (without associated LOS), 752 (28%) had LOS alone (without associated EOS), and 64 (2%) displayed both EOS and LOS. At 5 years of age, the frequency of cerebral palsy was 9% (157 of 1769) and that of cognitive impairment was 12% (177 of 1495). The frequency of cerebral palsy was higher in infants with isolated EOS (odds ratio [OR]: 1.70 [95% confidence interval (CI): 0.84-3.45]) or isolated LOS (OR: 1.71 [95% CI: 1.14-2.56]) than in uninfected infants, and this risk was even higher in cases of combined EOS and LOS (OR: 2.33 [95% CI: 1.02-5.33]). There was no association between neonatal infection and cognitive impairment.

CONCLUSIONS

Neonatal infections in these very preterm infants were associated with a higher risk of cerebral palsy at the age of 5 years, particularly in infants presenting with both EOS and LOS.

Functional brain maturation assessed during early life correlates with anatomical brain maturation at term-equivalent age in preterm infants

BACKGROUND

Amplitude-integrated electroencephalogram (aEEG) is a reliable monitoring tool for electrocortical activity with good predictive value in preterm infants. Magnetic resonance imaging (MRI) is a good neuroimaging tool to detect brain lesions and to evaluate brain maturation. We hypothesized that early aEEG measures, recorded over the first 3 d of life in very preterm infants, correlate with brain maturation and injury score assessed by conventional MRI at term-equivalent age.

METHODS

Thirty-nine infants born at a mean (range) gestational age (GA) of 29.5 (27.0-31.9) wk and birth weight 1,230 (680-2,020) g had continuous aEEG during the first postnatal 72-84 h. aEEG maturity scores and average maximum and minimum amplitudes were evaluated. Conventional brain MRI was performed at 41.2 (37.1-44.1) wk postmenstrual age (PMA) on a 3T GE system and scored qualitatively for injury and maturation.

RESULTS

The average aEEG total maturity score and its cycling subscore were positively and significantly associated with the total MRI maturation score after adjustment for GA, morphine sedation, and PMA at MRI examination. No association was found between the aEEG measures and the MRI injury scores.

CONCLUSION

Early aEEG maturity seems to relate to structural MRI brain maturation at term-equivalent age in preterm infants.

Brain metabolite concentrations are associated with illness severity scores and white matter abnormalities in very preterm infants

BACKGROUND

Magnetic resonance spectroscopy allows for the noninvasive study of brain metabolism and therefore may provide useful information about brain injuries. We examined the associations of brain metabolite ratios in very preterm infants with white matter lesions and overall health status at birth.

METHODS

Spectroscopy data were obtained from 99 very preterm infants (born ≤32 wk gestation) imaged shortly after birth and from 67 of these infants at term-equivalent age. These data were processed using LCModel. Multiple regression was used to examine the association of metabolite ratios with focal noncystic white matter lesions visible on conventional magnetic resonance imaging (MRI) and with at-birth illness severity scores.

RESULTS

Within 2 wk of birth, the ratio of N-acetylaspartate + N-acetylaspartylglutamate to creatine + phosphocreatine was significantly lower in those infants showing white matter abnormalities on conventional MRI. Increased lactate to creatine + phosphocreatine and lactate to glycerophosphocholine + phosphocholine ratios were significantly associated with increasing severity of Clinical Risk Index for Babies II and Apgar scores taken at 1 and 5 min after birth.

CONCLUSION

Both overall health status at birth and white matter injury in preterm neonates are reflected in metabolite ratios measured shortly after birth. Long-term follow-up will provide additional insight into the prognostic value of these measures.

Visual function in preterm infants: visualizing the brain to improve prognosis

Considerable development of the visual system occurs in the third trimester of life, a time when very preterm-born infants are in a neonatal intensive care unit (NICU). Their very early birth during a period of rapid and marked neurodevelopment and their clinical course makes them a very high-risk population. A range of different events impacts brain development and the visual system, leading to significant long-term visual dysfunction. Improved neuroimaging techniques provide an important window on the early brain and visual system development of these vulnerable infants. Greater understanding of the etiology of visual impairment subsequent to preterm birth and the timing of critical processes will allow early recognition and the earlier implementations of interventions. In the longer term, this will help clinicians optimize NICU practice to reduce the incidence of visual dysfunction in these children.

Evidence for therapeutic intervention in the prevention of cerebral palsy: hope from animal model research

Knowledge translation, as defined by the Canadian Institute of Health Research, is defined as the exchange, synthesis, and ethically sound application of knowledge--within a complex system of interactions among researchers and users--to accelerate the capture of the benefits of research through improved health, more effective services and products, and a strengthened healthcare system. The requirement for this to occur lies in the ability to continue to determine mechanistic actions at the molecular level, to understand how they fit at the in vitro and in vivo levels, and for disease states, to determine their safety, efficacy, and long-term potential at the preclinical animal model level. In this regard, particularly as it relates to long-term disabilities such as cerebral palsy that begin in utero, but only express their full effect in adulthood, animal models must be used to understand and rapidly evaluate mechanisms of injury and therapeutic interventions. In this review, we hope to provide the reader with a background of animal data upon which therapeutic interventions for the prevention and treatment of cerebral palsy, benefit this community, and increasingly do so in the future.

Brain development in infants born preterm: looking beyond injury

Infants born very preterm are high risk for acquired brain injury and disturbances in brain maturation. Although survival rates for preterm infants have increased in the last decades owing to improved neonatal intensive care, motor disabilities including cerebral palsy persist, and impairments in cognitive, language, social, and executive functions have not decreased. Evidence from neuroimaging studies exploring brain structure, function, and metabolism has indicated abnormalities in the brain development trajectory of very preterm-born infants that persist through to adulthood. In this chapter, we review neuroimaging approaches for the identification of brain injury in the preterm neonate. Advances in medical imaging and availability of specialized equipment necessary to scan infants have facilitated the feasibility of conducting longitudinal studies to provide greater understanding of early brain injury and atypical brain development and their effects on neurodevelopmental outcome. Improved understanding of the risk factors for acquired brain injury and associated factors that affect brain development in this population is setting the stage for improving the brain health of children born preterm.

Score for neonatal acute physiology-II and neonatal pain predict corticospinal tract development in premature newborns

Premature infants are at risk for adverse motor outcomes, including cerebral palsy and developmental coordination disorder. The purpose of this study was to examine the relationship of antenatal, perinatal, and postnatal risk factors for abnormal development of the corticospinal tract, the major voluntary motor pathway, during the neonatal period. In a prospective cohort study, 126 premature neonates (24-32 weeks' gestational age) underwent serial brain imaging near birth and at term-equivalent age. With diffusion tensor tractography, mean diffusivity and fractional anisotropy of the corticospinal tract were measured to reflect microstructural development. Generalized estimating equation models examined associations of risk factors on corticospinal tract development. The perinatal risk factor of greater early illness severity (as measured by the Score for Neonatal Acute Physiology-II [SNAP-II]) was associated with a slower rise in fractional anisotropy of the corticospinal tract (P = 0.02), even after correcting for gestational age at birth and postnatal risk factors (P = 0.009). Consistent with previous findings, neonatal pain adjusted for morphine and postnatal infection were also associated with a slower rise in fractional anisotropy of the corticospinal tract (P = 0.03 and 0.02, respectively). Lessening illness severity in the first hours of life might offer potential to improve motor pathway development in premature newborns.

An epigenetic framework for neurodevelopmental disorders: from pathogenesis to potential therapy

Neurodevelopmental disorders (NDDs) are characterized by aberrant and delayed early-life development of the brain, leading to deficits in language, cognition, motor behaviour and other functional domains, often accompanied by somatic symptoms. Environmental factors like perinatal infection, malnutrition and trauma can increase the risk of the heterogeneous, multifactorial and polygenic disorders, autism and schizophrenia. Conversely, discrete genetic anomalies are involved in Down, Rett and Fragile X syndromes, tuberous sclerosis and neurofibromatosis, the less familiar Phelan-McDermid, Sotos, Kleefstra, Coffin-Lowry and "ATRX" syndromes, and the disorders of imprinting, Angelman and Prader-Willi syndromes. NDDs have been termed "synaptopathies" in reference to structural and functional disturbance of synaptic plasticity, several involve abnormal Ras-Kinase signalling ("rasopathies"), and many are characterized by disrupted cerebral connectivity and an imbalance between excitatory and inhibitory transmission. However, at a different level of integration, NDDs are accompanied by aberrant "epigenetic" regulation of processes critical for normal and orderly development of the brain. Epigenetics refers to potentially-heritable (by mitosis and/or meiosis) mechanisms controlling gene expression without changes in DNA sequence. In certain NDDs, prototypical epigenetic processes of DNA methylation and covalent histone marking are impacted. Conversely, others involve anomalies in chromatin-modelling, mRNA splicing/editing, mRNA translation, ribosome biogenesis and/or the regulatory actions of small nucleolar RNAs and micro-RNAs. Since epigenetic mechanisms are modifiable, this raises the hope of novel therapy, though questions remain concerning efficacy and safety. The above issues are critically surveyed in this review, which advocates a broad-based epigenetic framework for understanding and ultimately treating a diverse assemblage of NDDs ("epigenopathies") lying at the interface of genetic, developmental and environmental processes. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Devastating coagulase-negative staphylococcal septicaemia in an extremely low birth weight infant

In developed countries, coagulase-negative staphylococci (CoNS) are responsible for the majority of late-onset infections in very low birth weight infants undergoing neonatal intensive care. As a common skin commensal, they are often considered as mere contaminants of peripheral blood cultures or as relatively benign bacteria clinically. We present a case of invasive CoNS septicaemia in an extremely low birth weight infant which had devastating effects.

Innate immune regulation by toll-like receptors in the brain

The innate immune system plays an important role in cerebral health and disease. In recent years the role of innate immune regulation by toll-like receptors in the brain has been highlighted. In this paper the expression of toll-like receptors and endogenous toll-like receptor ligands in the brain and their role in cerebral ischemia will be discussed. Further, the ability of systemic toll-like receptor ligands to induce cerebral inflammation will be reviewed. Finally, the capacity of toll-like receptors to both increase (sensitization) and decrease (preconditioning/tolerance) the vulnerability of the brain to damage will be disclosed. Studies investigating the role of toll-like receptors in the developing brain will be emphasized.

A neonatal model of intravenous Staphylococcus epidermidis infection in mice <24 h old enables characterization of early innate immune responses

Staphylococcus epidermidis (SE) causes late onset sepsis and significant morbidity in catheterized preterm newborns. Animal models of SE infection are useful in characterizing disease mechanisms and are an important approach to developing improved diagnostics and therapeutics. Current murine models of neonatal bacterial infection employ intraperitoneal or subcutaneous routes at several days of age, and may, therefore, not accurately reflect distinct features of innate immune responses to bacteremia. In this study we developed, validated, and characterized a murine model of intravenous (IV) infection in neonatal mice <24 hours (h) old to describe the early innate immune response to SE. C57BL/6 mice <24 h old were injected IV with 10⁶, 10⁷, 10⁸ colony-forming units (CFU) of SE 1457, a clinical isolate from a central catheter infection. A prospective injection scoring system was developed and validated, with only high quality injections analyzed. Newborn mice were euthanized between 2 and 48 h post-injection and spleen, liver, and blood collected to assess bacterial viability, gene expression, and cytokine production. High quality IV injections demonstrated inoculum-dependent infection of spleen, liver and blood. Within 2 h of injection, SE induced selective transcription of TLR2 and MyD88 in the liver, and increased systemic production of plasma IL-6 and TNF-α. Despite clearance of bacteremia and solid organ infection within 48 h, inoculum-dependent impairment in weight gain was noted. We conclude that a model of IV SE infection in neonatal mice <24 h old is feasible, demonstrating inoculum-dependent infection of solid organs and a pattern of bacteremia, rapid and selective innate immune activation, and impairment of weight gain typical of infected human neonates. This novel model can now be used to characterize immune ontogeny, evaluate infection biomarkers, and assess preventative and therapeutic modalities.

STAT3-mediated astrogliosis protects myelin development in neonatal brain injury

OBJECTIVE

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

METHODS

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

RESULTS

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

INTERPRETATION

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