Brain Injury in the Preterm Infant: New Horizons for Pathogenesis and Prevention

Nutrition and the gut-brain axis in neonatal brain injury and development

Early nutritional exposures, including during embryogenesis and the immediate postnatal period, affect offspring outcomes in both the short- and long-term. Alterations of these modifiable exposures shape the developing gut microbiome, intestinal development, and even neurodevelopmental outcomes. A gut-brain axis exists, and it is intricately connected to early life feeding and nutritional exposures. Here, we seek to discuss the (1) origins of the gut-brain access and relationship with neurodevelopment, (2) components of human milk (HM) beyond nutrition and their role in the developing newborn, and (3) clinical application of nutritional practices, including fluid management and feeding on the development of the gut-brain axis, and long-term neurodevelopmental outcomes. We conclude with a discussion on future directions and unanswered questions that are critical to provide further understanding and insight into how clinicians and healthcare providers can optimize early nutritional practices to ensure children not only survive, but thrive, free of neurodevelopmental impairment.

Role of the Gut Microbiota-Brain Axis in Brain Damage in Preterm Infants

The greatest repository of microbes in the human body, the intestinal microbiome, is involved in neurological development, aging, and brain illnesses such as white matter injury (WMI) in preterm newborns. Intestinal microorganisms constitute a microbial gut-brain axis that serves as a crucial conduit for communication between the gut and the nervous system. This axis controls inflammatory cytokines, which in turn influence the differentiation of premyelinating oligodendrocytes (pre-OLs) and influence the incidence of WMI in premature newborns through the metabolites generated by gut microbes. Here, we describe the effects of white matter injury (WMI) on intestinal dysbiosis and gut dysfunction and explain the most recent research findings on the gut-brain axis in both humans and animals. We also emphasize the delicate relationship that exists between the microbiota and the brain following acute brain injury. The role that the intestinal microflora plays in influencing host metabolism, the immune system, brain health, and the course of disease is becoming increasingly clear, but there are still gaps in the field of WMI treatment. Thus, this review demonstrates the function of the gut microflora-brain axis in WMI and elucidates the possible mechanisms underlying the communication between gut bacteria and the developing brain via the gut-brain axis, potentially opening up new avenues for microbial-based intervention and treatment for preterm WMI.

Early, low-dose hydrocortisone and near-term brain connectivity in extremely preterm infants

BACKGROUND

Postnatal steroids are used to prevent bronchopulmonary dysplasia in extremely preterm infants but may have adverse effects on brain development. We assessed connectivity metrics of major cerebral and cerebellar white matter pathways at near-term gestational age among infants who did or did not receive a standardized regimen of hydrocortisone during the first 10 days of life.

METHODS

Retrospective cohort study.

PARTICIPANTS

Infants born <28 weeks: Protocol group (n = 33) received at least 50% and not more than 150% of an intended standard dose of 0.5 mg/kg hydrocortisone twice daily for 7 days, then 0.5 mg/kg per day for 3 days; Non-Protocol group (n = 22), did not receive protocol hydrocortisone or completed <50% of the protocol dose. We assessed group differences in near-term diffusion MRI mean fractional anisotropy (FA) and mean diffusivity (MD) across the corticospinal tract, inferior longitudinal fasciculus, corpus callosum and superior cerebellar peduncle.

RESULTS

Groups were comparable in gestational age, post-menstrual age at scan, medical complications, bronchopulmonary dysplasia, and necrotizing enterocolitis. No significant large effect group differences were identified in mean FA or MD in any cerebral or cerebellar tract.

CONCLUSION(S)

Low dose, early, postnatal hydrocortisone was not associated with significant differences in white matter tract microstructure at near-term gestational age.

IMPACT

This study compared brain microstructural connectivity as a primary outcome among extremely preterm infants who did or did not receive early postnatal hydrocortisone. Low dose hydrocortisone in the first 10 days of life was not associated with significant differences in white matter microstructure in major cerebral and cerebellar pathways. Hydrocortisone did not have a significant effect on early brain white matter circuits.

[Effects of α1-antitrypsin on motor function in mice with immature brain white matter injury]

OBJECTIVES

To investigate the effects of α1-antitrypsin (AAT) on motor function in adult mice with immature brain white matter injury.

METHODS

Five-day-old C57BL/6J mice were randomly assigned to the sham surgery group (n=27), hypoxia-ischemia (HI) + saline group (n=27), and HI+AAT group (n=27). The HI white matter injury mouse model was established using HI methods. The HI+AAT group received intraperitoneal injections of AAT (50 mg/kg) 24 hours before HI, immediately after HI, and 72 hours after HI; the HI+saline group received intraperitoneal injections of the same volume of saline at the corresponding time points. Brain T2-weighted magnetic resonance imaging scans were performed at 7 and 55 days after modeling. At 2 months of age, adult mice were evaluated for static, dynamic, and coordination parameters using the Catwalk gait analysis system.

RESULTS

Compared to the sham surgery group, mice with HI injury showed high signal intensity on brain T2-weighted magnetic resonance imaging at 7 days after modeling, indicating significant white matter injury. The white matter injury persisted at 55 days after modeling. In comparison to the sham surgery group, the HI+saline group exhibited decreased paw print area, maximum contact area, average pressure, maximum pressure, paw print width, average velocity, body velocity, stride length, swing speed, percentage of gait pattern AA, and percentage of inter-limb coordination (left hind paw → left front paw) (P<0.05). The HI+saline group showed increased inter-paw distance, percentage of gait pattern AB, and percentage of phase lag (left front paw → left hind paw) compared to the sham surgery group (P<0.05). In comparison to the HI+saline group, the HI+AAT group showed increased average velocity, body velocity, stride length, and swing speed (right front paw) (P<0.05).

CONCLUSIONS

The mice with immature brain white matter injury may exhibit significant motor dysfunction in adulthood, while the use of AAT can improve some aspects of their motor function.

Effect of tactile and/or kinesthetic stimulation therapy of preterm infants on their parents' anxiety and depressive symptoms: A systematic review

BACKGROUND

In the case of preterm birth, the idealized postnatal period is replaced by an anxious and even traumatic experience for parents. Higher prevalence of parental anxiety, postnatal depression, and posttraumatic stress disorder has been observed in mothers of preterm infants up to 18 months after childbirth. There is increasing evidence that proprioceptive stimulation has a beneficial effect on preterms' short-term outcomes. Could this care also have an impact on parental anxiety and depressive symptoms? We reviewed recent publications on the impact on parents' anxiety and depressive symptoms of delivering tactile and/or kinesthetic stimulation to their premature newborn.

METHODS

We conducted a systematic review by searching the PubMed, PsycInfo, Scopus, ScienceDirect and Google Scholar databases for English-language publications from the past 10 years. We focused on the mothers or fathers of infants born preterm (before 37 weeks of gestation) who provided tactile and/or kinesthetic stimulation to their premature newborn in the neonatal intensive care unit. Relevant outcomes were the parents' anxiety, stress, depressive symptoms, and symptoms of posttraumatic stress disorder, assessed with reliable standardized inventories.

RESULTS

Eleven articles were included in the systematic review. Results suggested a beneficial effect of parents' early tactile and kinesthetic stimulation of their preterm infants.

CONCLUSIONS

These interventions may act as protective factors against the occurrence of anxiety and depressive symptoms in parents and deserve to be studied further in this population.

Oligodendrocyte Progenitor Cell Transplantation Ameliorates Preterm Infant Cerebral White Matter Injury in Rats Model

Background

Cerebral white matter injury (WMI) is the most common brain injury in preterm infants, leading to motor and developmental deficits often accompanied by cognitive impairment. However, there is no effective treatment. One promising approach for treating preterm WMI is cell replacement therapy, in which lost cells can be replaced by exogenous oligodendrocyte progenitor cells (OPCs).

Methods

This study developed a method to differentiate human neural stem cells (hNSCs) into human OPCs (hOPCs). The preterm WMI animal model was established in rats on postnatal day 3, and OLIG2+/NG2+/PDGFRα+/O4+ hOPCs were enriched and transplanted into the corpus callosum on postnatal day 10. Then, histological analysis and electron microscopy were used to detect lesion structure; behavioral assays were performed to detect cognitive function.

Results

Transplanted hOPCs survived and migrated throughout the major white matter tracts. Morphological differentiation of transplanted hOPCs was observed. Histological analysis revealed structural repair of lesioned areas. Re-myelination of the axons in the corpus callosum was confirmed by electron microscopy. The Morris water maze test revealed cognitive function recovery.

Conclusion

Our study showed that exogenous hOPCs could differentiate into CC1+ OLS in the brain of WMI rats, improving their cognitive functions.

A comparison of altered white matter microstructure in youth born with congenital heart disease or born preterm

Introduction

Alterations to white matter microstructure as detected by diffusion tensor imaging have been documented in both individuals born with congenital heart disease (CHD) and individuals born preterm. However, it remains unclear if these disturbances are the consequence of similar underlying microstructural disruptions. This study used multicomponent driven equilibrium single pulse observation of T₁ and T₂ (mcDESPOT) and neurite orientation dispersion and density imaging (NODDI) to characterize and compare alterations to three specific microstructural elements of white matter - myelination, axon density, and axon orientation - in youth born with CHD or born preterm.

Methods

Participants aged 16 to 26 years with operated CHD or born ≤33 weeks gestational age and a group of healthy peers of the same age underwent a brain MRI including mcDESPOT and high angular resolution diffusion imaging acquisitions. Using tractometry, average values of myelin water fraction (MWF), neurite density index (NDI), and orientation dispersion index (ODI) were first calculated and compared between groups for 30 white matter bundles. Afterwards, bundle profiling was performed to further characterize the topology of the detected microstructural alterations.

Results

The CHD and preterm groups both presented with widespread bundles and bundle segments with lower MWF, accompanied by some occurrences of lower NDI, relative to controls. While there were no differences in ODI between the CHD and control groups, the preterm group presented with both higher and lower ODI compared to the control group and lower ODI compared to the CHD group.

Discussion

While youth born with CHD or born preterm both presented with apparent deficits in white matter myelination and axon density, youth born preterm presented with a unique profile of altered axonal organization. Future longitudinal studies should aim to better understand the emergence of these common and distinct microstructural alterations, which could orient the development of novel therapeutic approaches.

Immuno-epigenetic signature derived in saliva associates with the encephalopathy of prematurity and perinatal inflammatory disorders

BACKGROUND

Preterm birth is closely associated with a phenotype that includes brain dysmaturation and neurocognitive impairment, commonly termed Encephalopathy of Prematurity (EoP), of which systemic inflammation is considered a key driver. DNA methylation (DNAm) signatures of inflammation from peripheral blood associate with poor brain imaging outcomes in adult cohorts. However, the robustness of DNAm inflammatory scores in infancy, their relation to comorbidities of preterm birth characterised by inflammation, neonatal neuroimaging metrics of EoP, and saliva cross-tissue applicability are unknown.

METHODS

Using salivary DNAm from 258 neonates (n = 155 preterm, gestational age at birth 23.28 - 34.84 weeks, n = 103 term, gestational age at birth 37.00 - 42.14 weeks), we investigated the impact of a DNAm surrogate for C-reactive protein (DNAm CRP) on brain structure and other clinically defined inflammatory exposures. We assessed i) if DNAm CRP estimates varied between preterm infants at term equivalent age and term infants, ii) how DNAm CRP related to different types of inflammatory exposure (maternal, fetal and postnatal) and iii) whether elevated DNAm CRP associated with poorer measures of neonatal brain volume and white matter connectivity.

RESULTS

Higher DNAm CRP was linked to preterm status (-0.0107 ± 0.0008, compared with -0.0118 ± 0.0006 among term infants; p < 0.001), as well as perinatal inflammatory diseases, including histologic chorioamnionitis, sepsis, bronchopulmonary dysplasia, and necrotising enterocolitis (OR range |2.00 | to |4.71|, p < 0.01). Preterm infants with higher DNAm CRP scores had lower brain volume in deep grey matter, white matter, and hippocampi and amygdalae (β range |0.185| to |0.218|). No such associations were observed for term infants. Association magnitudes were largest for measures of white matter microstructure among preterms, where elevated epigenetic inflammation associated with poorer global measures of white matter integrity (β range |0.206| to |0.371|), independent of other confounding exposures.

CONCLUSIONS

Inflammatory-related DNAm captures the allostatic load of inflammatory burden in preterm infants. Such DNAm measures complement biological and clinical metrics when investigating the determinants of neurodevelopmental differences.

Pathogenesis from the microbial-gut-brain axis in white matter injury in preterm infants: A review

White matter injury (WMI) in premature infants is a unique form of brain injury and a common cause of chronic nervous system conditions such as cerebral palsy and neurobehavioral disorders. Very preterm infants who survive are at high risk of WMI. With developing research regarding the pathogenesis of premature WMI, the role of gut microbiota has attracted increasing attention in this field. As premature infants are a special group, early microbial colonization of the microbiome can affect brain development, and microbiome optimization can improve outcomes regarding nervous system development. As an important communication medium between the gut and the nervous system, intestinal microbes form a microbial-gut-brain axis. This axis affects the occurrence of WMI in premature infants via the metabolites produced by intestinal microorganisms, while also regulating cytokines and mediating oxidative stress. At the same time, deficiencies in the microbiota and their metabolites may exacerbate WMI in premature infants. This confers promise for probiotics and prebiotics as treatments for improving neurodevelopmental outcomes. Therefore, this review attempted to elucidate the potential mechanisms behind the communication of gut bacteria and the immature brain through the gut-brain axis, so as to provide a reference for further prevention and treatment of premature WMI.

Protocol for a prospective multicenter longitudinal randomized controlled trial (CALIN) of sensory-tonic stimulation to foster parent child interactions and social cognition in very premature infants

Introduction

Premature birth is associated with long-term somatic and neurological disorders, including cognitive, social and behavioral impairments. Moreover, the mothers of infants born preterm exhibit a higher prevalence of anxiety and depressive symptoms after birth. Early rehabilitation, developmental care, and parenting support have already been shown to have a positive impact on neurological outcome. However, no randomized controlled study has so far assessed the effects on parenting and long-term neurological outcomes of proprioceptive stimulation to trigger positive brain plasticity in very preterm babies. The CALIN project will therefore investigate the impact of sensory-tonic stimulation (STS) of extremely preterm infants by their parents on child parent interactions, infants' morphological and functional brain development and subsequent cognition (including social cognition), and parents' anxiety and depressive symptoms in the postpartum period.

Methods and analysis

Infants born between 25 and 32 weeks of gestation will be randomly assigned to the "STS + Kangaroo care" or "Kangaroo care" group. The primary endpoint, child and parent interactions, will be rated at 12 months corrected age using the Coding Interactive Behavior system. Secondary endpoints include: 1/functional and anatomical brain maturation sequentially assessed during neonatal hospitalization using electroencephalogram (EEG), amplitude-integrated EEG (aEEG), cranial ultrasound and MRI performed at term-corrected age, 2/social and cognitive outcomes assessed at 15 months, 2, 4 and 6 years, and 3/parents' anxiety and depressive symptoms assessed at 7 ± 1 weeks after birth, using dedicated questionnaires.

Ethics and dissemination

This study was approved by the French Ethics Committee for the Protection of Persons on 18 October 2021. It is registered with the French National Agency for the Safety of Medicines and Health Products (ANSM; no. 2020-A00382-37). The registry number on ClinicalTrials.gov is NCT04380051.

Extremely preterm children and relationships of minor neurodevelopmental impairments at 6 years

Aim

This study investigated minor impairments in neurological, sensorimotor, and neuropsychological functioning in extremely preterm-born (EPT) children compared to term-born children. The aim was to explore the most affected domains and to visualize their co-occurrences in relationship maps.

Methods

A prospective cohort of 56 EPT children (35 boys) and 37 term-born controls (19 boys) were assessed at a median age of 6 years 7 months with Touwen Neurological Examination, Movement Assessment Battery for Children, 2nd edition (MABC-2), Sensory Integration and Praxis Test (SIPT), and a Developmental Neuropsychological Assessment, 2nd edition (NEPSY-II). Altogether 20 test domains were used to illustrate the frequency of impaired test performances with a bar chart profile and to construct relationship maps of co-occurring impairments.

Results

The EPT children were more likely to perform inferiorly compared to the term-born controls across all assessments, with a wider variance and more co-occurring impairments. When aggregating all impaired test domains, 45% of the EPT children had more impaired domains than any term-born child (more than five domains, p &lt; 0.001). Relationship maps showed that minor neurological dysfunction (MND), NEPSY-II design copying, and SIPT finger identification constituted the most prominent relationship of co-occurring impairments in both groups. However, it was ten times more likely in the EPT group. Another relationship of co-occurring MND, impairment in NEPSY-II design copying, and NEPSY-II imitation of hand positions was present in the EPT group only.

Interpretation

Multiple minor impairments accumulate among EPT children at six years, suggesting that EPT children and their families may need support and timely multi-professional interventions throughout infancy and childhood.

Early structural connectivity within the sensorimotor network: Deviations related to prematurity and association to neurodevelopmental outcome

Consisting of distributed and interconnected structures that interact through cortico-cortical connections and cortico-subcortical loops, the sensorimotor (SM) network undergoes rapid maturation during the perinatal period and is thus particularly vulnerable to preterm birth. However, the impact of prematurity on the development and integrity of the emerging SM connections and their relationship to later motor and global impairments are still poorly understood. In this study we aimed to explore to which extent the early microstructural maturation of SM white matter (WM) connections at term-equivalent age (TEA) is modulated by prematurity and related with neurodevelopmental outcome at 18 months corrected age. We analyzed 118 diffusion MRI datasets from the developing Human Connectome Project (dHCP) database: 59 preterm (PT) low-risk infants scanned near TEA and a control group of full-term (FT) neonates paired for age at MRI and sex. We delineated WM connections between the primary SM cortices (S1, M1 and paracentral region) and subcortical structures using probabilistic tractography, and evaluated their microstructure with diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) models. To go beyond tract-specific univariate analyses, we computed a maturational distance related to prematurity based on the multi-parametric Mahalanobis distance of each PT infant relative to the FT group. Our results confirmed the presence of microstructural differences in SM tracts between PT and FT infants, with effects increasing with lower gestational age at birth. Maturational distance analyses highlighted that prematurity has a differential effect on SM tracts with higher distances and thus impact on (i) cortico-cortical than cortico-subcortical connections; (ii) projections involving S1 than M1 and paracentral region; and (iii) the most rostral cortico-subcortical tracts, involving the lenticular nucleus. These different alterations at TEA suggested that vulnerability follows a specific pattern coherent with the established WM caudo-rostral progression of maturation. Finally, we highlighted some relationships between NODDI-derived maturational distances of specific tracts and fine motor and cognitive outcomes at 18 months. As a whole, our results expand understanding of the significant impact of premature birth and early alterations on the emerging SM network even in low-risk infants, with possible relationship with neurodevelopmental outcomes. This encourages further exploration of these potential neuroimaging markers for prediction of neurodevelopmental disorders, with special interest for subtle neuromotor impairments frequently observed in preterm-born children.

The Joint Observation in Neonatology and Neurodevelopmental Outcome of Preterm Infants at Six Months Corrected Age: Secondary Outcome Data from a Randomised Controlled Trial

This study aimed to evaluate the impact of a standardised joint observation (JOIN) performed in the neonatal intensive care unit (NICU) on the neurodevelopment of preterm infants at six months corrected age (CA) compared with a preterm control group. In this monocentric interventional randomised controlled trial, we allocated 76 mothers and their preterm neonates to either JOIN, an early one-session intervention, or standard care during the NICU hospitalisation. The neurodevelopment of the preterm infants was assessed by standardised developmental tests at six months CA and compared between the intervention and the control groups. This randomised controlled trial was registered on clinicaltrials.gov (NCT02736136) in April 2016. Sixty-five infants underwent neurodevelopmental assessment at six months CA. There were no significant differences between the two groups in neurodevelopmental outcome measures. The JOIN intervention was not associated with significant improvement in neurodevelopment at six months CA in preterm infants.

MRI-based brain volumes of preterm infants at term: a systematic review and meta-analysis

BACKGROUND

MRI allows a detailed assessment of brain structures in preterm infants, outperforming cranial ultrasound. Neonatal MR-based brain volumes of preterm infants could serve as objective, quantitative and reproducible surrogate parameters of early brain development. To date, there are no reference values for preterm infants' brain volumes at term-equivalent age.

OBJECTIVE

Systematic review of the literature to determine reference ranges for MRI-based brain volumes of very preterm infants at term-equivalent age.

METHODS

PubMed Database was searched on 6 April 2020 for studies reporting MR-based brain volumes on representative unselected populations of very preterm and/or very low birthweight infants examined at term equivalent age (defined as 37-42 weeks mean postmenstrual age at MRI). Analyses were limited to volumetric parameters reported in >3 studies. Weighted mean volumes and SD were both calculated and simulated for each parameter.

RESULTS

An initial 367 publications were identified. Following application of exclusion criteria, 13 studies from eight countries were included for analysis, yielding four parameters. Weighted mean total brain volume was 379 mL (SD 72 mL; based on n=756). Cerebellar volume was 21 mL (6 mL; n=791), cortical grey matter volume 140 mL (47 mL; n=572) and weighted mean volume of unmyelinated white matter was 195 mL (38 mL; n=499).

CONCLUSION

This meta-analysis reports pooled data on several brain and cerebellar volumes which can serve as reference for future studies assessing MR-based volumetric parameters as a surrogate outcome for neurodevelopment and for the interpretation of individual or cohort MRI-based volumetric findings.

Adult outcome of preterm birth: Implications for neurodevelopmental theories of psychosis

Preterm birth is associated with an elevated risk of developmental and adult psychiatric disorders, including psychosis. In this review, we evaluate the implications of neurodevelopmental, cognitive, motor, and social sequelae of preterm birth for developing psychosis, with an emphasis on outcomes observed in adulthood. Abnormal brain development precipitated by early exposure to the extra-uterine environment, and exacerbated by neuroinflammation, neonatal brain injury, and genetic vulnerability, can result in alterations of brain structure and function persisting into adulthood. These alterations, including abnormal regional brain volumes and white matter macro- and micro-structure, can critically impair functional (e.g. frontoparietal and thalamocortical) network connectivity in a manner characteristic of psychotic illness. The resulting executive, social, and motor dysfunctions may constitute the basis for behavioural vulnerability ultimately giving rise to psychotic symptomatology. There are many pathways to psychosis, but elucidating more precisely the mechanisms whereby preterm birth increases risk may shed light on that route consequent upon early neurodevelopmental insult.

Proteomic analysis of the effects of caffeine in a neonatal rat model of hypoxic-ischemic white matter damage

Aim

White matter damage (WMD) is the main cause of cerebral palsy and cognitive impairment in premature infants. Although caffeine has been shown to possess neuroprotective effects in neonatal rats with hypoxic‐ischemic WMD, the mechanisms underlying these protective effects are unclear. Herein, proteins modulated by caffeine in neonatal rats with hypoxic‐ischemic WMD were evaluated.

Methods

We identified differential proteins and performed functional enrichment analyses between the Sham, hypoxic‐ischemic WMD (HI), and HI+caffeine‐treated WMD (Caffeine) groups. Confirmed the changes and effect of proteins in animal models and determined cognitive impairment via water maze experiments.

Results

In paraventricular tissue, 47 differential proteins were identified between the Sham, HI, and Caffeine groups. Functional enrichment analyses showed that these proteins were related to myelination and axon formation. In particular, the myelin basic protein (MBP), proteolipid protein, myelin‐associated glycoprotein precursor, and sirtiun 2 (SIRT2) levels were reduced in the hypoxic‐ischemic WMD group, and this effect could be prevented by caffeine. Caffeine alleviated the hypoxic‐ischemic WMD‐induced cognitive impairment and improved MBP, synaptophysin, and postsynaptic density protein 95 protein levels after hypoxic‐ischemic WMD by preventing the HI‐induced downregulation of SIRT2; these effects were subsequently attenuated by the SIRT2 inhibitor AK‐7.

Conclusion

Caffeine may have clinical applications in the management of prophylactic hypoxic‐ischemic WMD; its effects may be mediated by proteins related to myelin development and synapse formation through SIRT2.

White Matter Injury in Preterm Infants: Pathogenesis and Potential Therapy From the Aspect of the Gut–Brain Axis

Very preterm infants who survive are at high risk of white matter injury (WMI). With a greater understanding of the pathogenesis of WMI, the gut microbiota has recently drawn increasing attention in this field. This review tries to clarify the possible mechanisms behind the communication of the gut bacteria and the immature brain via the gut–brain axis. The gut microbiota releases signals, such as microbial metabolites. These metabolites regulate inflammatory and immune responses characterized by microglial activation, which ultimately impact the differentiation of pre-myelinating oligodendrocytes (pre-OLs) and lead to WMI. Moreover, probiotics and prebiotics emerge as a promising therapy to improve the neurodevelopmental outcome. However, future studies are required to clarify the function of these above products and the optimal time for their administration within a larger population. Based on the existing evidence, it is still too early to recommend probiotics and prebiotics as effective treatments for WMI.

Advanced Brain Imaging in Preterm Infants: A Narrative Review of Microstructural and Connectomic Disruption

Preterm birth disrupts the in utero environment, preventing the brain from fully developing, thereby causing later cognitive and behavioral disorders. Such cerebral alteration occurs beneath an anatomical scale, and is therefore undetectable by conventional imagery. Prematurity impairs the microstructure and thus the histological process responsible for the maturation, including the myelination. Cerebral MRI diffusion tensor imaging sequences, based on water’s motion into the brain, allows a representation of this maturation process. Similarly, the brain’s connections become disorganized. The connectome gathers structural and anatomical white matter fibers, as well as functional networks referring to remote brain regions connected one over another. Structural and functional connectivity is illustrated by tractography and functional MRI, respectively. Their organizations consist of core nodes connected by edges. This basic distribution is already established in the fetal brain. It evolves greatly over time but is compromised by prematurity. Finally, cerebral plasticity is nurtured by a lifetime experience at microstructural and macrostructural scales. A preterm birth causes a negative and early disruption, though it can be partly mitigated by positive stimuli based on developmental neonatal care.

Choline Kinetics in Neonatal Liver, Brain and Lung-Lessons from a Rodent Model for Neonatal Care

Choline requirements are high in the rapidly growing fetus and preterm infant, mainly serving phosphatidylcholine (PC) synthesis for parenchymal growth and one-carbon metabolism via betaine. However, choline metabolism in critical organs during rapid growth is poorly understood. Therefore, we investigated the kinetics of D9-choline and its metabolites in the liver, plasma, brain and lung in 14 d old rats. Animals were intraperitoneally injected with 50 mg/kg D9-choline chloride and sacrificed after 1.5 h, 6 h and 24 h. Liver, plasma, lungs, cerebrum and cerebellum were analyzed for D9-choline metabolites, using tandem mass spectrometry. In target organs, D9-PC and D9-betaine comprised 15.1 ± 1.3% and 9.9 ± 1.2% of applied D9-choline at 1.5 h. D9-PC peaked at 1.5 h in all organs, and decreased from 1.5-6 h in the liver and lung, but not in the brain. Whereas D9-labeled PC precursors were virtually absent beyond 6 h, D9-PC increased in the brain and lung from 6 h to 24 h (9- and 2.5-fold, respectively) at the expense of the liver, suggesting PC uptake from the liver via plasma rather than local synthesis. Kinetics of D9-PC sub-groups suggested preferential hepatic secretion of linoleoyl-PC and acyl remodeling in target organs. D9-betaine showed rapid turnover and served low-level endogenous (D3-)choline synthesis. In conclusion, in neonatal rats, exogenous choline is rapidly metabolized to PC by all organs. The liver supplies the brain and lung directly with PC, followed by organotypic acyl remodeling. A major fraction of choline is converted to betaine, feeding the one-carbon pool and this must be taken into account when calculating choline requirements.

Neurodevelopmental Outcomes following Intrauterine Growth Restriction and Very Preterm Birth

OBJECTIVES

To evaluate whether intrauterine growth restriction (IUGR) adds further neurodevelopmental risk to that posed by very preterm birth alone in terms of alterations in brain growth and poorer toddlerhood outcomes.

STUDY DESIGN

Participants were 314 infants of very preterm birth enrolled in the Evaluation of Preterm Imaging Study (e-Prime) who were subsequently followed up in toddlerhood. IUGR was identified postnatally from discharge records (n = 49) and defined according to prenatal evaluation of growth restriction confirmed by birth weight <10th percentile for gestational age and/or alterations in fetal Doppler. Appropriate for gestational age (AGA; n = 265) was defined as birth weight >10th percentile for gestational age at delivery. Infants underwent magnetic resonance imaging at term-equivalent age (median = 42 weeks); T2-weighted images were obtained for voxelwise gray matter volumes. Follow-up assessments were conducted at corrected median age of 22 months using the Bayley Scales of Infant and Toddler Development III and the Modified-Checklist for Autism in Toddlers.

RESULTS

Infants of very preterm birth with IUGR displayed a relative volumetric decrease in gray matter in limbic regions and a relative increase in frontoinsular, temporal-parietal, and frontal areas compared with peers of very preterm birth who were AGA. At follow-up, toddlers born very preterm with IUGR had significantly lower cognitive (effect size = 0.42) and motor (effect size = 0.41) scores and were more likely to have a positive Modified-Checklist for Autism in Toddlers screening for autism (OR = 2.12) compared with peers of very preterm birth who were AGA.

CONCLUSIONS

IUGR might confer a neurodevelopmental risk that is greater than that posed by very preterm alone, in terms of both alterations in brain growth and poorer toddlerhood outcomes.

Preimplantation factor modulates oligodendrocytes by H19-induced demethylation of NCOR2

Failed or altered gliogenesis is a major characteristic of diffuse white matter injury in survivors of premature birth. The developmentally regulated long noncoding RNA (lncRNA) H19 inhibits S-adenosylhomocysteine hydrolase (SAHH) and contributes to methylation of diverse cellular components, such as DNA, RNA, proteins, lipids, and neurotransmitters. We showed that the pregnancy-derived synthetic PreImplantation Factor (sPIF) induces expression of the nuclear receptor corepressor 2 (NCOR2) via H19/SAHH-mediated DNA demethylation. In turn, NCOR2 affects oligodendrocyte differentiation markers. Accordingly, after hypoxic-ischemic brain injury in rodents, myelin protection and oligodendrocytes' fate are in part modulated by sPIF and H19. Our results revealed an unexpected mechanism of the H19/SAHH axis underlying myelin preservation during brain recovery and its use in treating neurodegenerative diseases can be envisioned.

Chronic Exposure to Hypoxia Inhibits Myelinogenesis and Causes Motor Coordination Deficits in Adult Mice

Exposure to chronic hypoxia is considered to be a risk factor for deficits in brain function in adults, but the underlying mechanisms remain largely unknown. Since active myelinogenesis persists in the adult central nervous system, here we aimed to investigate the impact of chronic hypoxia on myelination and the related functional consequences in adult mice. Using a transgenic approach to label newly-generated myelin sheaths (NG2-CreERTM; Tau-mGFP), we found that myelinogenesis was highly active in most brain regions, such as the motor cortex and corpus callosum. After exposure to hypoxia (10% oxygen) 12 h per day for 4 weeks, myelinogenesis was largely inhibited in the 4-month old brain and the mice displayed motor coordination deficits revealed by the beam-walking test. To determine the relationship between the inhibited myelination and functional impairment, we induced oligodendroglia-specific deletion of the transcription factor Olig2 by tamoxifen (NG2-CreERTM; Tau-mGFP; Olig2 fl/fl) in adult mice to mimic the decreased myelinogenesis caused by hypoxia. The deletion of Olig2 inhibited myelinogenesis and consequently impaired motor coordination, suggesting that myelinogenesis is required for motor function in adult mice. To understand whether enhancing myelination could protect brain functions against hypoxia, we treated hypoxic mice with the myelination-enhancing drug-clemastine, which resulted in enhanced myelogenesis and improved motor coordination. Taken together, our data indicate that chronic hypoxia inhibits myelinogenesis and causes functional deficits in the brain and that enhancing myelinogenesis protects brain functions against hypoxia-related deficits.

The Role of Extracellular Vesicles in the Developing Brain: Current Perspective and Promising Source of Biomarkers and Therapy for Perinatal Brain Injury

This comprehensive review focuses on our current understanding of the proposed physiological and pathological functions of extracellular vesicles (EVs) in the developing brain. Furthermore, since EVs have attracted great interest as potential novel cell-free therapeutics, we discuss advances in the knowledge of stem cell- and astrocyte-derived EVs in relation to their potential for protection and repair following perinatal brain injury. This review identified 13 peer-reviewed studies evaluating the efficacy of EVs in animal models of perinatal brain injury; 12/13 utilized mesenchymal stem cell-derived EVs (MSC-EVs) and 1/13 utilized astrocyte-derived EVs. Animal model, method of EV isolation and size, route, timing, and dose administered varied between studies. Notwithstanding, EV treatment either improved and/or preserved perinatal brain structures both macroscopically and microscopically. Additionally, EV treatment modulated inflammatory responses and improved brain function. Collectively this suggests EVs can ameliorate, or repair damage associated with perinatal brain injury. These findings warrant further investigation to identify the optimal cell numbers, source, and dosage regimens of EVs, including long-term effects on functional outcomes.

GSK-3β inhibitor TWS119 alleviates hypoxic-ischemic brain damage via a crosstalk with Wnt and Notch signaling pathways in neonatal rats

Preterm infant brain injury is a leading cause of morbidity and disability in survivors of preterm infants. Unfortunately, the effective treatment remains absent. Recent evidence suggests that GSK-3β inhibitor TWS119 has a neuroprotectiverole in adult brain injury by activation of Wnt/β-catenin signaling pathway. However, the role on neonatal brain injury is not yet explored. The study aims to evaluate the effect of TWS119 at 7 d after hypoxic-ischemic brain damage and investigate the mechanism that it regulates Wnt and Notch signaling pathways at 24 h after hypoxic-ischemic brain damage in neonatal rats. Three-day-old rats were randomly divided into 3 groups: sham group, HI group and TWS119 group. The neonatal rats were subjected to left carotid artery ligation followed by 2 h of hypoxia (8.0% O₂). A single dose of TWS119 (30 mg/kg) was intraperitoneally injected 20 min prior to hypoxia-ischemia (HI). At 7 d after HI, TWS119 improved the tissue structure, reduced cell apoptosis, up-regulated bcl-2 expression, up-regulated the expression of PSD-95 and Synapsin-1. At 24 h after HI, it activated Wnt/β-catenin signaling pathway by up-regulation of β-catenin protein expression and wnt3a/wnt5a/wnt7a mRNA expression. Simultaneously, it suppressed Notch signaling pathway by down-regulation of Notch1 and HES-1 proteins expression. Our study suggested that TWS119 performed a neuroprotective function at 7 d after hypoxic-ischemic brain damage via a crosstalk with Wnt/β-catenin and Notch signaling pathways at 24 h after hypoxic-ischemic brain damage in neonatal rats.

Induction of Tertiary Phase Epileptiform Discharges after Postasphyxial Infusion of a Toll-Like Receptor 7 Agonist in Preterm Fetal Sheep

Background: Toll-like receptor (TLR) agonists are key immunomodulatory factors that can markedly ameliorate or exacerbate hypoxic–ischemic brain injury. We recently demonstrated that central infusion of the TLR7 agonist Gardiquimod (GDQ) following asphyxia was highly neuroprotective after 3 days but not 7 days of recovery. We hypothesize that this apparent transient neuroprotection is associated with modulation of seizure-genic processes and hemodynamic control. Methods: Fetuses received sham asphyxia or asphyxia induced by umbilical cord occlusion (20.9 ± 0.5 min) and were monitored continuously for 7 days. GDQ 3.34 mg or vehicle were infused intracerebroventricularly from 1 to 4 h after asphyxia. Results: GDQ infusion was associated with sustained moderate hypertension that resolved after 72 h recovery. Electrophysiologically, GDQ infusion was associated with reduced number and burden of postasphyxial seizures in the first 18 h of recovery (p < 0.05). Subsequently, GDQ was associated with induction of slow rhythmic epileptiform discharges (EDs) from 72 to 96 h of recovery (p < 0.05 vs asphyxia + vehicle). The total burden of EDs was associated with reduced numbers of neurons in the caudate nucleus (r² = 0.61, p < 0.05) and CA1/2 hippocampal region (r² = 0.66, p < 0.05). Conclusion: These data demonstrate that TLR7 activation by GDQ modulated blood pressure and suppressed seizures in the early phase of postasphyxial recovery, with subsequent prolonged induction of epileptiform activity. Speculatively, this may reflect delayed loss of early protection or contribute to differential neuronal survival in subcortical regions.

Intrauterine growth restriction followed by oxygen support uniquely interferes with genetic regulators of myelination

Intrauterine growth restriction (IUGR) and oxygen exposure in isolation and combination adversely affect the developing brain, putting infants at risk for neurodevelopmental disability including cerebral palsy. Rodent models of IUGR and postnatal hyperoxia have demonstrated oligodendroglial injury with subsequent white matter injury (WMI) and motor dysfunction. Here we investigate transcriptomic dysregulation in IUGR with and without hyperoxia exposure to account for the abnormal brain structure and function previously documented. We performed RNA sequencing and analysis using a mouse model of IUGR and found that IUGR, hyperoxia, and the combination of IUGR with hyperoxia (IUGR/hyperoxia) produced distinct changes in gene expression. IUGR in isolation demonstrated the fewest differentially expressed genes compared to control. In contrast, we detected several gene alterations in IUGR/hyperoxia; genes involved in myelination were strikingly downregulated. We also identified changes to specific regulators including TCF7L2, BDNF, SOX2, and DGCR8, through Ingenuity Pathway Analysis, that may contribute to impaired myelination in IUGR/hyperoxia. Our findings show that IUGR with hyperoxia induces unique transcriptional changes in the developing brain. These indicate mechanisms for increased risk for WMI in IUGR infants exposed to oxygen and suggest potential therapeutic targets to improve motor outcomes.Significance StatementThis study demonstrates that perinatal exposures of IUGR and/or postnatal hyperoxia result in distinct transcriptomic changes in the developing brain. In particular, we found that genes involved in normal developmental myelination, myelin maintenance, and remyelination were most dysregulated when IUGR was combined with hyperoxia. Understanding how multiple risk factors lead to WMI is the first step in developing future therapeutic interventions. Additionally, because oxygen exposure is often unavoidable after birth, an understanding of gene perturbations in this setting will increase our awareness of the need for tight control of oxygen use to minimize future motor disability.

Influence of Quiet Time on the Auditory Environment of Infants in the NICU

OBJECTIVE

To determine the influence of quiet time on the auditory environment of infants in the NICU and to compare the effect of quiet time by room type, bed type, and infant clinical acuity.

DESIGN

Cross-sectional, descriptive comparison study.

PARTICIPANTS

Sixty-six infants born at less than 38 weeks gestation who were between 32 and 40 weeks postmenstrual age.

SETTING

The auditory environments of infants in two level 3 NICUs within a pediatric hospital system in the Southeastern United States. Each NICU implemented quiet time for 4 hours per day.

METHODS

We assessed the auditory environment of the participants using Language Environmental Analysis technology. We used paired t tests to assess differences in the auditory environment during quiet versus nonquiet time and to compare the effect of quiet time by room type, bed type, and clinical acuity.

RESULTS

During quiet time, the auditory environment of participants had 13% more silence, 17% fewer electronic sounds, 25% less speech, and 30% fewer words than during nonquiet time. We observed greater differences in quiet time versus nonquiet time for infants in open bays and incubators and infants who had greater acuity.

CONCLUSION

Our results support the implementation of quiet time to increase silence and reduce exposure to electronic sounds for infants in the NICU. Additional research is necessary to further examine the effect of quiet time on the auditory environment of infants in the NICU with consideration of environmental and clinical variables.

Window of opportunity for human amnion epithelial stem cells to attenuate astrogliosis after umbilical cord occlusion in preterm fetal sheep

There is increasing evidence that administration of many types of stem cells, including human amnion epithelial cells (hAECs), can reduce hypoxic-ischemic injury, including in the perinatal brain. However, the therapeutic window for single dose treatment is not known. We compared the effects of early and delayed intracerebroventricular administration of hAECs in fetal sheep at 0.7 gestation on brain injury induced by 25 minutes of complete umbilical cord occlusion (UCO) or sham occlusion. Fetuses received either 1 × 10⁶ hAECs or vehicle alone, as an infusion over 1 hour, either 2 or 24 hours after UCO. Fetuses were killed for brain histology at 7 days post-UCO. hAEC infusion at both 2 and 24 hours had dramatic anti-inflammatory and anti-gliotic effects, including significantly attenuating the increase in microglia after UCO in the white and gray matter and the number of astrocytes in the white matter. Both protocols partially improved myelination, but had no effect on total or immature/mature numbers of oligodendrocytes. Neuronal survival in the hippocampus was increased by hAEC infusion at either 2 or 24 hours, whereas only hAECs at 24 hours were associated with improved neuronal survival in the striatum and thalamus. Neither protocol improved recovery of electroencephalographic (EEG) power. These data suggest that a single infusion of hAECs is anti-inflammatory, anti-gliotic, and neuroprotective in preterm fetal sheep when given up to 24 hours after hypoxia-ischemia, but was associated with limited white matter protection after 7 days recovery and no improvement in the recovery of EEG power.

Effects of antenatal dexamethasone and hyperglycemia on cardiovascular adaptation to asphyxia in preterm fetal sheep

Antenatal glucocorticoids improve outcomes among premature infants but are associated with hyperglycemia, which can exacerbate hypoxic-ischemic injury. It is still unclear how antenatal glucocorticoids or hyperglycemia modulate fetal cardiovascular adaptations to severe asphyxia. In this study, preterm fetal sheep received either saline or 12 mg im maternal dexamethasone, followed 4 h later by complete umbilical cord occlusion (UCO) for 25 min. An additional cohort of fetuses received titrated glucose infusions followed 4 h later by UCO to control for the possibility that hyperglycemia contributed to the cardiovascular effects of dexamethasone. Fetuses were studied for 7 days after UCO. Maternal dexamethasone was associated with fetal hyperglycemia (P < 0.001), increased arterial pressure (P < 0.001), and reduced femoral (P < 0.005) and carotid (P < 0.05) vascular conductance before UCO. UCO was associated with bradycardia, femoral vasoconstriction, and transient hypertension. For the first 5 min of UCO, fetal blood pressure in the dexamethasone-asphyxia group was greater than saline-asphyxia (P < 0.001). However, the relative increase in arterial pressure was not different from saline-asphyxia. Fetal heart rate and femoral vascular conductance fell to similar nadirs in both saline and dexamethasone-asphyxia groups. Dexamethasone did not affect the progressive decline in femoral vascular tone or arterial pressure during continuing UCO. By contrast, there were no effects of glucose infusions on the response to UCO. In summary, maternal dexamethasone but not fetal hyperglycemia increased fetal arterial pressure before and for the first 5 min of prolonged UCO but did not augment the cardiovascular adaptations to acute asphyxia.

Neonatal white matter tract microstructure and 2-year language outcomes after preterm birth

•

Preterm infant white matter tracts uniquely predict later toddler language.

•

Neonatal medical history moderates posterior corpus callosum–language relations.

•

Different associations by tract may relate to brain maturation and medical history.

Aim

To determine whether variability in diffusion MRI (dMRI) white matter tract metrics, obtained in a cohort of preterm infants prior to neonatal hospital discharge, would be associated with language outcomes at age 2 years, after consideration of age at scan and number of major neonatal complications.

Method

30 children, gestational age 28.9 (2.4) weeks, underwent dMRI at mean post menstrual age 36.4 (1.4) weeks and language assessment with the Bayley Scales of Infant Development–III at mean age 22.2 (1.7) months chronological age. Mean fractional anisotropy (FA) and mean diffusivity (MD) were calculated for 5 white matter tracts. Hierarchical linear regression assessed associations between tract FA, moderating variables, and language outcomes.

Results

FA of the left inferior longitudinal fasciculus accounted for 17% (p = 0.03) of the variance in composite language and FA of the posterior corpus callosum accounted for 19% (p = 0.02) of the variance in composite language, beyond that accounted for by post-menstrual age at scan and neonatal medical complications. The number of neonatal medical complications moderated the relationship between language and posterior corpus callosum FA but did not moderate the association in the other tract.

Conclusion

Language at age 2 is associated with white matter metrics in early infancy in preterm children. The different pattern of associations by fiber group may relate to the stage of brain maturation and/or the nature and timing of medical complications related to preterm birth. Future studies should replicate these findings with a larger sample size to assure reliability of the findings.

[Psychoacoustic methods in diagnosis of central auditory processing disorders in prematurely born children]

INTRODUCTION

The presence of numerous perinatal risk factors and comorbid pathology in prematurely born children, even in the absence of peripheral auditory deficit, can lead to disruptions in the processes of higher nervous sound information processing with the formation of central auditory disorders.

OBJECTIVE

Audiological assessment of the functional state of auditory system central parts in prematurely born children.

MATERIAL AND METHODS

The study involved 54 deeply premature born infants, which were divided into 3 groups depending on age (6-7, 8-9, and 10-11 years), 18 subjects in each group, and 70 healthy, term-born children of the corresponding age. In addition to the traditional audiological examination, all children underwent an assessment of functional state of the central parts of auditory system through a pause detection test (Random Gap Detection Test, RGDT); the perception of fast rhythmic sequences of stimuli, monaural low excess speech testing, binaural interaction test in alternating binaural speech format (ABS ), dichotic presentation of pairs of single digits, single digits and monosyllables, two-digit numerals, Russian matrix phrasal test in noise (RUMatrix) were studied.

RESULTS

Prematurely born infants of all age groups were significantly worse compared to control group (p<0.01) while having RGDT, a test for assessing the perception of fast rhythmic sequences of stimuli and dichotic binaural integration tests. Monaural intelligibility of monosyllabic words in silence in children of all three groups did not differ from normal values, but it suffered from contralateral use of noise interference in children aged 6-7. According to the RUMatrix test, legibility of phrases in noise was impaired in 65% of subjects. Test results in the ABS format revealed a significant violation of speech intelligibility (p<0.01) only in children of the younger age group.

CONCLUSION

In prematurely born children, there is a dysfunction of the central parts of the auditory system, which is multilevel in nature, partially leveling as children grow older. Moreover, the processes of temporary processing of acoustic information suffer to the greatest extent, not being compensated up to adolescence.

Hypoxic-ischemic-related cerebrovascular changes and potential therapeutic strategies in the neonatal brain

Perinatal hypoxic-ischemic (HI)-related brain injury is an important cause of morbidity and long-standing disability in newborns. The only currently approved therapeutic strategy available to reduce brain injury in the newborn is hypothermia. Therapeutic hypothermia can only be used to treat HI encephalopathy in full-term infants and survivors remain at high risk for a wide spectrum of neurodevelopmental abnormalities as a result of residual brain injury. Therefore, there is an urgent need for adjunctive therapeutic strategies. Inflammation and neurovascular damage are important factors that contribute to the pathophysiology of HI-related brain injury and represent exciting potential targets for therapeutic intervention. In this review, we address the role of each component of the neurovascular unit (NVU) in the pathophysiology of HI-related injury in the neonatal brain. Disruption of the blood-brain barrier (BBB) observed in the early hours after an HI-related event is associated with a response at the basal lamina level, which comprises astrocytes, pericytes, and immune cells, all of which could affect BBB function to further exacerbate parenchymal injury. Future research is required to determine potential drugs that could prevent or attenuate neurovascular damage and/or augment repair. However, some studies have reported beneficial effects of hypothermia, erythropoietin, stem cell therapy, anti-cytokine therapy and metformin in ameliorating several different facets of damage to the NVU after HI-related brain injury in the perinatal period.

Applications of advanced signal processing and machine learning in the neonatal hypoxic-ischemic electroencephalogram

Perinatal hypoxic-ischemic-encephalopathy significantly contributes to neonatal death and life-long disability such as cerebral palsy. Advances in signal processing and machine learning have provided the research community with an opportunity to develop automated real-time identification techniques to detect the signs of hypoxic-ischemic-encephalopathy in larger electroencephalography/amplitude-integrated electroencephalography data sets more easily. This review details the recent achievements, performed by a number of prominent research groups across the world, in the automatic identification and classification of hypoxic-ischemic epileptiform neonatal seizures using advanced signal processing and machine learning techniques. This review also addresses the clinical challenges that current automated techniques face in order to be fully utilized by clinicians, and highlights the importance of upgrading the current clinical bedside sampling frequencies to higher sampling rates in order to provide better hypoxic-ischemic biomarker detection frameworks. Additionally, the article highlights that current clinical automated epileptiform detection strategies for human neonates have been only concerned with seizure detection after the therapeutic latent phase of injury. Whereas recent animal studies have demonstrated that the latent phase of opportunity is critically important for early diagnosis of hypoxic-ischemic-encephalopathy electroencephalography biomarkers and although difficult, detection strategies could utilize biomarkers in the latent phase to also predict the onset of future seizures.

Structural neuroimaging

Characterizing the neuroanatomical correlates of brain development is essential in understanding brain-behavior relationships and neurodevelopmental disorders. Advances in brain MRI acquisition protocols and image processing techniques have made it possible to detect and track with great precision anatomical brain development and pediatric neurologic disorders. In this chapter, we provide a brief overview of the modern neuroimaging techniques for pediatric brain development and review key normal brain development studies. Characteristic disorders affecting neurodevelopment in childhood, such as prematurity, attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), epilepsy, and brain cancer, and key neuroanatomical findings are described and then reviewed. Large datasets of typically developing children and children with various neurodevelopmental conditions are now being acquired to help provide the biomarkers of such impairments. While there are still several challenges in imaging brain structures specific to the pediatric populations, such as subject cooperation and tissues contrast variability, considerable imaging research is now being devoted to solving these problems and improving pediatric data analysis.

Basal ganglia and thalamic tract connectivity in very preterm and full-term children; associations with 7-year neurodevelopment

BACKGROUND

Altered basal ganglia and thalamic connectivity may be critical for cognitive, motor and behavioural impairments common to very preterm (<32 weeks' gestational age) children. This study aims to (1) compare corticostriatal and thalamocortical tract connectivity between very preterm and term-born children at 7 years of age; (2) explore tract connectivity associations with 7-year neurodevelopmental outcomes, and whether these relationships differed between groups.

METHODS

Eighty-three very preterm and 19 term-born (≥37 weeks' gestational age) children underwent structural and diffusion magnetic resonance imaging and had a neuropsychological assessment at 7 years. Corticostriatal and thalamocortical tracts were reconstructed and white matter connectivity was estimated with apparent fibre density.

RESULTS

Compared with term-born controls, very preterm children had decreased connectivity in tracts linking the caudate to right motor areas (-10%, p = 0.03) and the thalamus with left motor areas (-5.7%, p = 0.03). Reduced connectivity in corticostriatal and thalamocortical tracts was associated with adverse motor functioning in both groups (p = 0.06). Decreased connectivity of the left caudate and putamen with the lateral prefrontal cortex was associated with lower reading performance for controls (p = 0.06).

CONCLUSION

Corticostriatal and thalamocortical tracts are vulnerable to very preterm birth. Poorer connectivity in these tracts may underlie the motor impairments observed in very preterm children.

Unfolded protein response in myelin disorders

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

Neuroprotection Strategies in Preterm Encephalopathy

Advances in neonatology have led to unprecedented improvements in neonatal survival such that those born as early as 22 weeks of gestation now have some chance of survival, and over 70% of those born at 24 weeks of gestation survive. Up to 50% of infants born extremely preterm develop poor outcomes involving long-term neurodevelopmental impairments affecting cognition and learning, or motor problems such as cerebral palsy. Poor outcomes arise because the preterm brain is vulnerable both to direct injury (by events such as intracerebral hemorrhage, infection, and/or hypoxia), or indirect injury due to disruption of normal development. This neonatal brain injury and/or dysmaturation is called "encephalopathy of prematurity". Current and future strategies to improve outcomes in this population include prevention of preterm birth, and pre-, peri-, and postnatal approaches to protect the developing brain. This review will describe mechanisms of preterm brain injury, and current and upcoming therapies in the antepartum and postnatal period to improve preterm encephalopathy.

Synaptic Injury in the Thalamus Accompanies White Matter Injury in Hypoxia/Ischemia-Mediated Brain Injury in Neonatal Rats

The broad spectrum of disabilities caused by white matter injury (WMI) cannot be explained simply by hypomyelination. Synaptic injury in the thalamus may be related to disabilities in WMI survivors. Neuronal injury in the thalamus has been found most commonly in autopsy cases of preterm WMI. We hypothesized that hypoxia/ischemia (HI) in neonatal rats results in synaptic abnormalities in the thalamus that contribute to disabilities in WMI survivors. We examined changes in synapses in a neonatal rat model of HI-induced WMI. Right common carotid artery ligation and hypoxia (8% oxygen for 2.5 hours (h)) were performed in three-day-old Sprague-Dawley rats. We found HI rats performed worse in the Morris water maze test than sham rats, suggesting long-term cognition impairment after HI injury. A loss of synapses in the thalamus accompanied by hypomyelination and oligodendrocytes (OLs) reduction was observed. At the ultrastructural level, reductions in active zone (AZ) length and postsynaptic density (PSD) thickness were detected at 2 weeks after HI exposure. Furthermore, increased expression of synaptophysin and PSD-95 in both groups was observed from 3 days (d) to 21 d after hypoxic/ischemic (HI) injury. PSD-95 expression was significantly lower in HI rats than in sham rats from 14 d to 21 d after HI injury, and synaptophysin expression was significantly lower in HI rats from 7 d to 14 d after HI injury. However, no significant difference in synaptophysin expression was observed between HI rats and sham rats at 21 d after HI injury. The results demonstrated synaptic abnormalities in the thalamus accompanied by hypomyelination in WMI in response to HI exposure, which may contribute to the diverse neurological defects observed in WMI patients. Although synaptic reorganization occurred as a compensatory response to HI injury, the impairments in synaptic transmission were not reversed.

Motor and Postural Patterns Concomitant with General Movements Are Associated with Cerebral Palsy at Term and Fidgety Age in Preterm Infants

General movements (GMs) in combination with neurological examination and magnetic resonance imaging at term age can accurately determine the risk of cerebral palsy. The present study aimed to assess whether 11 motor and postural patterns concomitant with GMs were associated with cerebral palsy. Video recordings performed after birth in 79 preterm infants were reviewed retrospectively. Thirty-seven infants developed cerebral palsy at 2 years corrected age and the remaining 42 showed typical development. GMs were assessed from preterm to fidgety age and GM trajectories were defined. The 11 motor and postural patterns were evaluated at each age and longitudinally, alone and in combination with GM trajectories. A logistic regression model was used to assess the association between GMs, concomitant motor and postural patterns, and cerebral palsy. We confirmed that high-risk GM trajectories were associated with cerebral palsy (odds ratio = 44.40, 95% confidence interval = 11.74-167.85). An association between concomitant motor and postural patterns and cerebral palsy was found for some of the patterns at term age and for all of them at fidgety age. Therefore, at term age, concomitant motor and postural patterns can support GMs for the early diagnosis of cerebral palsy.

Dysmaturation of Premature Brain: Importance, Cellular Mechanisms, and Potential Interventions

Prematurity, especially preterm birth (less than 32 weeks' gestation), is common and associated with high rates of both survival and neurodevelopmental disability, especially apparent in cognitive spheres. The neuropathological substrate of this disability is now recognized to be related to a variety of dysmaturational disturbances of the brain. These disturbances follow initial brain injury, particularly cerebral white matter injury, and involve many of the extraordinary array of developmental events active in cerebral white and gray matter structures during the premature period. This review delineates these developmental events and the dysmaturational disturbances that occur in premature infants. The cellular mechanisms involved in the genesis of the dysmaturation are emphasized, with particular focus on the preoligodendrocyte. A central role for the diffusely distributed activated microglia and reactive astrocytes in the dysmaturation is now apparent. As these dysmaturational cellular mechanisms appear to occur over a relatively long time window, interventions to prevent or ameliorate the dysmaturation, that is, neurorestorative interventions, seem possible. Such interventions include pharmacologic agents, especially erythropoietin, and particular attention has also been paid to such nutritional factors as quality and source of milk, breastfeeding, polyunsaturated fatty acids, iron, and zinc. Recent studies also suggest a potent role for interventions directed at various experiential factors in the neonatal period and infancy, i.e., provision of optimal auditory and visual exposures, minimization of pain and stress, and a variety of other means of environmental behavioral enrichment, in enhancing brain development.

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

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

A Critical Evaluation of Current Concepts in Cerebral Palsy

Spastic cerebral palsy (CP), despite the name, is not consistently identifiable by specific brain lesions. CP animal models focus on risk factors for development of CP, yet few reproduce the diagnostic symptoms. Animal models of CP must advance beyond risk factors to etiologies, including both the brain and spinal cord.

White matter microstructure and cognitive outcomes in relation to neonatal inflammation in 6-year-old children born preterm

BACKGROUND

Cognitive outcomes in preterm (PT) children have been associated with microstructural properties of white matter. PT children who experienced neonatal inflammatory conditions have poorer cognitive outcomes than those who did not. The goal of this study was to contrast white matter microstructure and cognitive outcomes after preterm birth in relation to the presence or absence of severe inflammatory conditions in the neonatal period.

METHODS

PT children (n = 35), born at gestational age 22-32 weeks, were classified as either PT+ (n = 12) based on a neonatal history of inflammatory conditions, including bronchopulmonary dysplasia, necrotizing enterocolitis or culture positive sepsis, or PT- (n = 23) based on the absence of the three inflammatory conditions. Full term (FT) children (n = 43) served as controls. Participants underwent diffusion MRI and cognitive testing (intelligence, reading, and executive function) at age 6 years. The corpus callosum was segmented into 7 regions using deterministic tractography and based on the cortical projection zones of the callosal fibers. Mean fractional anisotropy (FA) and mean diffusivity (MD) were calculated for each segment. General linear models with planned contrasts assessed group differences in FA, MD and cognitive outcomes. Pearson correlations assessed associations of white matter metrics and cognitive outcome measures.

RESULTS

FA was significantly lower and MD was significantly higher in PT+ compared to PT- or FT groups in multiple callosal segments, even after adjusting for gestational age. Executive function scores, but not intelligence or reading scores, were less favorable in PT+ than in PT- groups. Among the entire sample, occipital FA was significantly correlated with IQ (r = 0.25, p < 0.05), reading (r = 0.32, p < 0.01), and executive function (r = -0.28, p < 0.05) measures. Anterior frontal FA and superior parietal FA were significantly correlated with executive function (r = -0.25, r = 0.23, respectively, p < 0.05).

CONCLUSIONS

We observed differences in the white matter microstructure of the corpus callosum and in the cognitive skills of 6-year-old PT children based on their history of neonatal inflammation. Neonatal inflammation is one medical factor that may contribute to variation in long-term neurobiological and neuropsychological outcomes in PT samples.

Joint observation in NICU (JOIN): study protocol of a clinical randomised controlled trial examining an early intervention during preterm care

INTRODUCTION

Preterm birth may generate significant distress among the parents, who often present with difficulties in appropriating their parental role. Parental stress and low perceived parental self-efficacy may interfere with the infant's socioemotional and cognitive development, particularly through disrupted parent-infant interactions. Perceived parental self-efficacy represents the belief of efficacy in caring for one's own infant and successful incarnation of the parental role, as well as the perception of one's own abilities to complete a specified task. Interventions to support parental role, as well as infant development, are needed, and parental self-efficacy represents a useful indicator to measure the effects of such early interventions.

METHODS AND ANALYSIS

This study protocol describes a randomised controlled trial that will test an early intervention in the neonatal intensive care unit (NICU) (JOIN: Joint Observation In Neonatology) carried out by an interdisciplinary staff team. Mothers of preterm neonates born between 28 and 32 6/7 weeks of gestational age are eligible for the study. The intervention consists of a videotaped observation by a clinical child psychologist or child psychiatrist and a study nurse of a period of care delivered to the neonate by the mother and a NICU nurse. The care procedure is followed by an interactive video guidance intended to demonstrate the neonate's abilities and resources to his parents. The primary outcome will be the difference in the perceived maternal self-efficacy between the intervention and control groups assessed by self-report questionnaires. Secondary outcomes will be maternal mental health, the perception of the parent- infant relationship, maternal responsiveness and the neurodevelopment of the infant at 6 months corrected age.

ETHICS AND DISSEMINATION

Ethical approval was granted by the Human Research Ethics Committee of the Canton de Vaud (study number 496/12). Results from this study will be disseminated at national and international conferences, and in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02736136, Pre-results.

More than myelin: Probing white matter differences in prematurity with quantitative T1 and diffusion MRI

OBJECTIVE

We combined diffusion MRI (dMRI) with quantitative T1 (qT1) relaxometry in a sample of school-aged children born preterm and full term to determine whether reduced fractional anisotropy (FA) within the corpus callosum of the preterm group could be explained by a reduction in myelin content, as indexed by R1 (1/T1) from qT1 scans.

METHODS

8-year-old children born preterm (n = 29; GA 22-32 weeks) and full term (n = 24) underwent dMRI and qT1 scans. Four subdivisions of the corpus callosum were segmented in individual native space according to cortical projection zones (occipital, temporal, motor and anterior-frontal). Fractional anisotropy (FA) and R1 were quantified along the tract trajectory of each subdivision and compared across two birth groups.

RESULTS

Compared to controls, preterm children demonstrated significantly decreased FA in 3 of 4 analyzed corpus callosum subdivisions (temporal, motor, and anterior frontal segments) and decreased R1 in only 2 of 4 corpus callosum subdivisions (temporal and motor segments). FA and RD were significantly associated with R1 within temporal but not anterior frontal subdivisions of the corpus callosum in the term group; RD correlated with R1 in the anterior subdivision in the preterm group only.

CONCLUSIONS

Myelin content, as indexed by R1, drives some but not all of the differences in white matter between preterm and term born children. Other factors, such as axonal diameter and directional coherence, likely contributed to FA differences in the anterior frontal segment of the corpus callosum that were not well explained by R1.

Neuroinflammation in preterm babies and autism spectrum disorders

Genetic anomalies have a role in autism spectrum disorders (ASD). Each genetic factor is responsible for a small fraction of cases. Environment factors, like preterm delivery, have an important role in ASD. Preterm infants have a 10-fold higher risk of developing ASD. Preterm birth is often associated with maternal/fetal inflammation, leading to a fetal/neonatal inflammatory syndrome. There are demonstrated experimental links between fetal inflammation and the later development of behavioral symptoms consistent with ASD. Preterm infants have deficits in connectivity. Most ASD genes encode synaptic proteins, suggesting that ASD are connectivity pathologies. Microglia are essential for normal synaptogenesis. Microglia are diverted from homeostatic functions towards inflammatory phenotypes during perinatal inflammation, impairing synaptogenesis. Preterm infants with ASD have a different phenotype from term born peers. Our original hypothesis is that exposure to inflammation in preterm infants, combined with at risk genetic background, deregulates brain development leading to ASD.

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

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

Enhancing Oligodendrocyte Myelination Rescues Synaptic Loss and Improves Functional Recovery after Chronic Hypoxia

To address the significance of enhancing myelination for functional recovery after white matter injury (WMI) in preterm infants, we characterized hypomyelination associated with chronic hypoxia and identified structural and functional deficits of excitatory cortical synapses with a prolonged motor deficit. We demonstrate that genetically delaying myelination phenocopies the synaptic and functional deficits observed in mice after hypoxia, suggesting that myelination may possibly facilitate excitatory presynaptic innervation. As a gain-of-function experiment, we specifically ablated the muscarinic receptor 1 (M1R), a negative regulator of oligodendrocyte differentiation in oligodendrocyte precursor cells. Genetically enhancing oligodendrocyte differentiation and myelination rescued the synaptic loss after chronic hypoxia and promoted functional recovery. As a proof of concept, drug-based myelination therapies also resulted in accelerated differentiation and myelination with functional recovery after chronic hypoxia. Together, our data indicate that myelination-enhancing strategies in preterm infants may represent a promising therapeutic approach for structural/functional recovery after hypoxic WMI.

The fetus at the tipping point: modifying the outcome of fetal asphyxia

Brain injury around birth is associated with nearly half of all cases of cerebral palsy. Although brain injury is multifactorial, particularly after preterm birth, acute hypoxia-ischaemia is a major contributor to injury. It is now well established that the severity of injury after hypoxia-ischaemia is determined by a dynamic balance between injurious and protective processes. In addition, mothers who are at risk of premature delivery have high rates of diabetes and antepartum infection/inflammation and are almost universally given treatments such as antenatal glucocorticoids and magnesium sulphate to reduce the risk of death and complications after preterm birth. We review evidence that these common factors affect responses to fetal asphyxia, often in unexpected ways. For example, glucocorticoid exposure dramatically increases delayed cell loss after acute hypoxia-ischaemia, largely through secondary hyperglycaemia. This critical new information is important to understand the effects of clinical treatments of women whose fetuses are at risk of perinatal asphyxia.