Early oxygen levels contribute to brain injury in extremely preterm infants

Oxygen in the newborn pneriod: Could the oxygen reserve index offer a new perspective?

Oxygen therapy has been one of the main challenges in neonatal intensive care units (NICU). The guidelines currently in use try to balance the burden of hypoxia and hyperoxia such as retinopathy of prematurity, bronchopulmonary dysplasia, and death. The goal of this paper is to review neonatal oxygenation and the impact of hyperoxia and hypoxia in neonatal outcomes as well as review the available literature concerning the use of Oxygen Reserve Index (ORiTM) in clinical practice and its potential in Neonatology, particularly in NICU. Pulse oximetry has been used to monitor oxygenation in newborns with the advantage of being a noninvasive and continuous parameter, however it has limitations in detecting hyperoxemic states due to the flattening of the hemoglobin dissociation curve. The ORiTM is a new parameter that has been used to detect moderate hyperoxia and, when used in addiction to spO2, could be helpful in both hypoxia and hyperoxia. Studies using this tool are mainly in the adult population, during anesthetic procedures with only a small number of studies being performed in pediatric context. Oxygen targets remain a major problem for neonatal population and regardless of the efforts made to establish a safe oxygenation range, a more individualized approach seems to be the more appropriate pathway. ORiTM monitoring could help defining how much oxygen is too much for each newborn. Despite its promising potential, ORiTM is still a recent technology that requires more studies to determine its true potential in clinical practice.

The developmental phenotype of motor delay in extremely preterm infants following early-life respiratory adversity is influenced by brain dysmaturation in the parietal lobe

BACKGROUND

Research indicates that preterm infants requiring prolonged mechanical ventilation often exhibit suboptimal neurodevelopment at follow-up, coupled with altered brain development as detected by magnetic resonance imaging (MRI) at term-equivalent age (TEA). However, specific regions of brain dysmaturation and the subsequent neurodevelopmental phenotype following early-life adverse respiratory exposures remain unclear. Additionally, it is uncertain whether brain dysmaturation mediates neurodevelopmental outcomes after respiratory adversity. This study aims to investigate the relationship between early-life adverse respiratory exposures, brain dysmaturation at TEA, and the developmental phenotype observed during follow-up in extremely preterm infants.

METHODS

89 infants born < 29 weeks' gestation from 2019 to 2021 received MRI examinations at TEA for structural and lobe brain volumes, which were adjusted with sex-and-postmenstrual-age expected volumes for volume residuals. Assisted ventilation patterns in the first 8 postnatal weeks were analyzed using kmlShape analyses. Patterns for motor, cognition, and language development were evaluated from corrected age 6 to 12 months using Bayley Scales of Infant Development, third edition. Mediation effects of brain volumes between early-life respiratory exposures and neurodevelopmental phenotypes were adjusted for sex, gestational age, maternal education, and severe brain injury.

RESULTS

Two distinct respiratory trajectories with varying severity were identified: improving (n = 35, 39%) and delayed improvement (n = 54, 61%). Compared with the improving group, the delayed improvement group exhibited selectively reduced brain volume residuals in the parietal lobe (mean - 4.9 cm3, 95% confidence interval - 9.4 to - 0.3) at TEA and lower motor composite scores (- 8.7, - 14.2 to - 3.1) at corrected age 12 months. The association between delayed respiratory improvement and inferior motor performance (total effect - 8.7, - 14.8 to - 3.3) was partially mediated through reduced parietal lobe volume (natural indirect effect - 1.8, - 4.9 to - 0.01), suggesting a mediating effect of 20%.

CONCLUSIONS

Early-life adverse respiratory exposure is specifically linked to the parietal lobe dysmaturation and neurodevelopmental phenotype of motor delay at follow-up. Dysmaturation of the parietal lobe serves as a mediator in the connection between respiratory adversity and compromised motor development. Optimizing respiratory critical care may emerge as a potential avenue to mitigate the consequences of altered brain growth and motor developmental delay in this extremely preterm population.

Neuromonitoring in neonatal intensive care units-an important need towards individualized neuroprotective care

Neuromonitoring has been widely accepted as an important part in neonatal care. Amplitude-integrated EEG (aEEG) and near-infrared spectroscopy (NIRS) are often mentioned in this context, though being only a part of the fully array of methods and examinations that could be considered neuromonitoring. Within the broad array of medical conditions that could be encountered in a neonatal patient, it is important to be aware of the indications for neuromonitoring and especially which neuromonitoring technique to use best for the individual condition. aEEG is now a widely accepted neuromonitor in neonatology with its value in hypoxic events and seizures only rarely questioned. Other methods like NIRS still have to prove themselves in the future. The SafeBoosC-III trial showed that it still remains difficult for some of these methods to prove their value for the improvement of outcome. Bute future developments such as multimodal neuromonitoring with data integration and artificial intelligence analysis could improve the value of these methods.

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 administration of umbilical cord blood cells following brief high tidal volume ventilation in preterm sheep: a cautionary tale

BACKGROUND

Umbilical cord blood (UCB) cells are a promising treatment for preterm brain injury. Access to allogeneic sources of UCB cells offer the potential for early administration to optimise their therapeutic capacities. As preterm infants often require ventilatory support, which can contribute to preterm brain injury, we investigated the efficacy of early UCB cell administration following ventilation to reduce white matter inflammation and injury.

METHODS

Preterm fetal sheep (0.85 gestation) were randomly allocated to no ventilation (SHAM; n = 5) or 15 min ex utero high tidal volume ventilation. One hour following ventilation, fetuses were randomly allocated to i.v. administration of saline (VENT; n = 7) or allogeneic term-derived UCB cells (24.5 ± 5.0 million cells/kg; VENT + UCB; n = 7). Twenty-four hours after ventilation, lambs were delivered for magnetic resonance imaging and post-mortem brain tissue collected. Arterial plasma was collected throughout the experiment for cytokine analyses. To further investigate the results from the in vivo study, mononuclear cells (MNCs) isolated from human UCB were subjected to in vitro cytokine-spiked culture medium (TNFα and/or IFNγ; 10 ng/mL; n = 3/group) for 16 h then supernatant and cells collected for protein and mRNA assessments respectively.

RESULTS

In VENT + UCB lambs, systemic IFNγ levels increased and by 24 h, there was white matter neuroglial activation, vascular damage, reduced oligodendrocytes, and increased average, radial and mean diffusivity compared to VENT and SHAM. No evidence of white matter inflammation or injury was present in VENT lambs, except for mRNA downregulation of OCLN and CLDN1 compared to SHAM. In vitro, MNCs subjected to TNFα and/or IFNγ displayed both pro- and anti-inflammatory characteristics indicated by changes in cytokine (IL-18 & IL-10) and growth factor (BDNF & VEGF) gene and protein expression compared to controls.

CONCLUSIONS

UCB cells administered early after brief high tidal volume ventilation in preterm fetal sheep causes white matter injury, and the mechanisms underlying these changes are likely dysregulated responses of the UCB cells to the degree of injury/inflammation already present. If immunomodulatory therapies such as UCB cells are to become a therapeutic strategy for preterm brain injury, especially after ventilation, our study suggests that the inflammatory state of the preterm infant should be considered when timing UCB cells administration.

Early versus late caffeine and/or non-steroidal anti-inflammatory drugs (NSAIDS) for prevention of intermittent hypoxia-induced neuroinflammation in the neonatal rat

Preterm infants often experience frequent intermittent hypoxia (IH) episodes which are associated with neuroinflammation. We tested the hypotheses that early caffeine and/or non-steroidal inflammatory drugs (NSAIDs) confer superior therapeutic benefits for protection against IH-induced neuroinflammation than late treatment. Newborn rats were exposed to IH or hyperoxia (50% O2) from birth (P0) to P14. For early treatment, the pups were administered: 1) daily caffeine (Caff) citrate (Cafcit, 20 mg/kg IP loading on P0, followed by 5 mg/kg from P1-P14); 2) ketorolac (Keto) topical ocular solution in both eyes from P0 to P14; 3) ibuprofen (Ibu, Neoprofen, 10 mg/kg loading dose on P0 followed by 5 mg/kg/day on P1 and P2); 4) Caff+Keto co-treatment; 5) Caff+Ibu co-treatment; or 6) equivalent volume saline (Sal). On P14, animals were placed in room air (RA) with no further treatment until P21. For late treatment, pups were exposed from P0 to P14, then placed in RA during which they received similar treatments from P15-P21 (Sal, Caff, and/or Keto), or P15-P17 (Ibu). RA controls were similarly treated. At P21, whole brains were assessed for histopathology, apoptosis, myelination, and biomarkers of inflammation. IH caused significant brain injury and hemorrhage, inflammation, reduced myelination, and apoptosis. Early treatment with Caff alone or in combination with NSAIDs conferred better neuroprotection against IH-induced damage than late treatment. Early postnatal treatment during a critical time of brain development, may be preferable for the prevention of IH-induced brain injury in preterm infants.

[Repair effect of different doses of human umbilical cord mesenchymal stem cells on white matter injury in neonatal rats]

OBJECTIVES

To compare the repair effects of different doses of human umbilical cord mesenchymal stem cells (hUC-MSCs) on white matter injury (WMI) in neonatal rats.

METHODS

Two-day-old Sprague-Dawley neonatal rats were randomly divided into five groups: sham operation group, WMI group, and hUC-MSCs groups (low dose, medium dose, and high dose), with 24 rats in each group. Twenty-four hours after successful establishment of the neonatal rat white matter injury model, the WMI group was injected with sterile PBS via the lateral ventricle, while the hUC-MSCs groups received injections of hUC-MSCs at different doses. At 14 and 21 days post-modeling, hematoxylin and eosin staining was used to observe pathological changes in the tissues around the lateral ventricles. Real-time quantitative polymerase chain reaction was used to detect the quantitative expression of myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) mRNA in the brain tissue. Immunohistochemistry was employed to observe the expression levels of GFAP and neuron-specific nuclear protein (NeuN) in the tissues around the lateral ventricles. TUNEL staining was used to observe cell apoptosis in the tissues around the lateral ventricles. At 21 days post-modeling, the Morris water maze test was used to observe the spatial learning and memory capabilities of the neonatal rats.

RESULTS

At 14 and 21 days post-modeling, numerous cells with nuclear shrinkage and rupture, as well as disordered arrangement of nerve fibers, were observed in the tissues around the lateral ventricles of the WMI group and the low dose group. Compared with the WMI group, the medium and high dose groups showed alleviated pathological changes; the arrangement of nerve fibers in the medium dose group was relatively more orderly compared with the high dose group. Compared with the WMI group, there was no significant difference in the expression levels of MBP and GFAP mRNA in the low dose group (P>0.05), while the expression levels of MBP mRNA increased and GFAP mRNA decreased in the medium and high dose groups. The expression level of MBP mRNA in the medium dose group was higher than that in the high dose group, and the expression level of GFAP mRNA in the medium dose group was lower than that in the high dose group (P<0.05). Compared with the WMI group, there was no significant difference in the protein expression of GFAP and NeuN in the low dose group (P>0.05), while the expression of NeuN protein increased and GFAP protein decreased in the medium and high dose groups. The expression of NeuN protein in the medium dose group was higher than that in the high dose group, and the expression of GFAP protein in the medium dose group was lower than that in the high dose group (P<0.05). Compared with the WMI group, there was no significant difference in the number of apoptotic cells in the low dose group (P>0.05), while the number of apoptotic cells in the medium and high dose groups was less than that in the WMI group, and the number of apoptotic cells in the medium dose group was less than that in the high dose group (P<0.05). Compared with the WMI group, there was no significant difference in the escape latency time in the low dose group (P>0.05); starting from the third day of the latency period, the escape latency time in the medium dose group was less than that in the WMI group (P<0.05). The medium and high dose groups crossed the platform more times than the WMI group (P<0.05).

CONCLUSIONS

Low dose hUC-MSCs may yield unsatisfactory repair effects on WMI in neonatal rats, while medium and high doses of hUC-MSCs have significant repair effects, with the medium dose demonstrating superior efficacy.

Pediatric Neurocritical Care: Maximizing Neurodevelopmental Outcomes Through Specialty Care

The field of pediatric neurocritical care (PNCC) has expanded and evolved over the last three decades. As mortality from pediatric critical care illness has declined, morbidity from neurodevelopmental disorders has expanded. PNCC clinicians have adopted a multidisciplinary approach to rapidly identify neurological injury, implement neuroprotective therapies, minimize secondary neurological insults, and establish transitions of care, all with the goal of improving neurocognitive outcomes for their patients. Although there are many aspects of PNCC and adult neurocritical care (NCC) medicine that are similar, elemental difference between adult and pediatric medicine has contributed to a divergent evolution of the respective fields. The low incidence of pediatric critical care illness, the heterogeneity of neurological insults, and the limited availability of resources all shape the need for a PNCC clinical care model that is distinct from the established paradigm adopted by the adult neurocritical care community at large. Considerations of neurodevelopment are fundamental in pediatrics. When neurological injury occurs in a child, the neurodevelopmental stage at the time of insult alters the impact of the neurological disease. Developmental variables contribute to a range of outcomes for seemingly similar injuries. Despite the relative infancy of the field of PNCC, early reports have shown that implementation of a specialized PNCC service elevates the quality and safety of care, promotes education and communication, and improves outcomes for children with acute neurological injuries. The multidisciplinary approach of PNCC clinicians and researchers also promotes a culture that emphasizes the importance of quality improvement and education initiatives, as well as development of and adherence to evidence-based guidelines and family-focused care models.

The differential associative relationship between early risk factors, neonatal morbidities and early neurodevelopmental outcome in preterm infants <29 weeks' gestation

BACKGROUND

Very preterm infants of <29 weeks' gestation are at high risk for adverse neurodevelopment due to multiple risk factors in the early stages of life. There is little information regarding the associative effects of risk factors in early life, neonatal morbidities and subsequent neurodevelopmental outcomes.

AIMS

Investigate the association of early neurodevelopmental outcomes, neonatal complications and the risk factors in the early hours of life in a cohort of preterm infants <29 weeks' gestational age.

METHODS

We enrolled all surviving preterm neonates born at gestation <29 weeks between January 2015 and June 2021 in the University of Hong Kong-Shenzhen Hospital. Demographic and clinical characteristics were collected from a database of the neonatal intensive care unit. Neurodevelopmental outcomes of the survivors were evaluated using the Ages and Stages Questionnaire (ASQ-3) which were measured at the adjusted age of 12 to 18 months. The multivariate linear regression model was used to determine correlation presented as β coefficient (β) with 95 % confidence intervals (CI).

RESULTS

In this cohort of 56 survivors <29 weeks' gestation, urine output within the first 12 h of life and Apgar score at 5 min were positively associated with different domains of ASQ-3 score, however male sex and highest fraction of inspired oxygen (FiO2) in the first 12 h of life were negatively related with at least one of neurocognitive domains of ASQ-3 at adjusted age of 12 to 18 months. During hospitalization, in addition to the frequency of packed red cell transfusions, the development of severe necrotizing enterocolitis was inversely associated with both neuromotor and neurocognitive skills (gross motor domain: β = -16.93, CI: -32.04, -1.82; fine motor domain: β = -16.42, CI: -28.82, -4.02; problem solving domain: β = -13.14, CI: -24.45, -1.83; all P < 0.05), whereas severe intraventricular hemorrhage had adverse effects on gross motor only (β = -13.04, CI: -24.42, -1.65; P = 0.03). Bronchopulmonary dysplasia and retinopathy of prematurity were not related with ASQ-3.

CONCLUSIONS

In this small cohort study of very preterm neonates born at <29 weeks' gestation, risk factors in the early hours of life and neonatal morbidities during hospitalization had differential associative relationships with ASQ-3 at 12-18 months adjusted age. This information may be important for parental counseling and management including early diagnosis and intervention.

Cerebral oximetry monitoring versus usual care for extremely preterm infants: a study protocol for the 2-year follow-up of the SafeBoosC-III randomised clinical trial

BACKGROUND

In the SafeBoosC-III trial, treatment guided by cerebral oximetry monitoring for the first 72 hours after birth did not reduce the incidence of death or severe brain injury in extremely preterm infants at 36 weeks' postmenstrual age, as compared with usual care. Despite an association between severe brain injury diagnosed in the neonatal period and later neurodevelopmental disability, this relationship is not always strong. The objective of the SafeBoosC-III follow-up study is to assess mortality, neurodevelopmental disability, or any harm in trial participants at 2 years of corrected age. One important challenge is the lack of funding for local costs for a trial-specific assessment.

METHODS

Of the 1601 infants randomised in the SafeBoosC-III trial, 1276 infants were alive at 36 weeks' postmenstrual age and will potentially be available for the 2-year follow-up. Inclusion criteria will be enrollment in a neonatal intensive care unit taking part in the follow-up study and parental consent if required by local regulations. We aim to collect data from routine follow-up programmes between the ages of 18 and 30 months of corrected age. If no routine follow-up has been conducted, we will collect informal assessments from other health care records from the age of at least 12 months. A local co-investigator blinded to group allocation will classify outcomes based on these records. We will supplement this with parental questionnaires including the Parent Report of Children's Abilities-Revised. There will be two co-primary outcomes: the composite of death or moderate or severe neurodevelopmental disability and mean Bayley-III/IV cognitive score. We will use a 3-tier model for prioritisation, based on the quality of data. This approach has been chosen to minimise loss to follow-up assuming that little data is better than no data at all.

DISCUSSION

Follow-up at the age of 2 years is important for intervention trials in the newborn period as only time can show real benefits and harms later in childhood. To decrease the risk of generalisation and data-driven biased conclusions, we present a detailed description of the methodology for the SafeBoosC-III follow-up study. As funding is limited, a pragmatic approach is necessary.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05134116 . Registered on 24 November 2021.

Improvised bubble continuous positive airway pressure ventilation use in neonates in resource-limited settings: a systematic review and meta-analysis

OBJECTIVES

In the face of limited fiscal and technical resources, improvised methods have been used to provide effective and sustainable ventilatory support in low-resource settings to reduce neonatal mortality associated with respiratory complications. This study assessed the use of improvised bubble continuous positive airway pressure (ibCPAP) ventilation among neonates with respiratory complications and determined its effect on neonatal outcomes in low- and middle-income countries (LMICs).

CONTENT

Hospital-based studies conducted between 2010 and 2020 in LMICs were reviewed. Rayyan® software for systematic review was used for screening and article selection. We used Stata® Statacorp Texas USA software to estimate pooled prevalence, proportion estimates, weighted mean differences and 95% Confidence Interval (CI), using the random effects model.

SUMMARY

A total of 193 articles were generated and 125 were reviewed. Thirteen articles with 806 neonates on ibCPAP ventilation were included. The pooled prevalence of ibCPAP use was 7.0% (95% CI: 3.0%-13.0%). There was a significant difference in mean oxygen saturation before and after ibCPAP use (-1.34% [95% CI: -1.65% to -1.02%, p<0.01). The duration of oxygen requirement among neonates on ibCPAP was 6.5 hours less than controls (0.27 days [95%CI: -0.49 to -0.05, p<0.01).

OUTLOOK

IbCPAP had no effect on the respiratory rate, duration of admission, mortality and survival. IbCPAP use in LMIC hospitals is low and its use improved oxygen saturation and duration on oxygen among the neonates, but had no impact on length of stay, respiratory rate, mortality or survival.

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.

Protective effect of resveratrol on mitochondrial biogenesis during hyperoxia-induced brain injury in neonatal pups

BACKGROUND

Neonatal hyperoxic brain injury is caused by exposure to hyperphysiological oxygen content during the period of incomplete development of the oxidative stress defence system, resulting in a large number of reactive oxygen species (ROS) and causing damage to brain tissue. Mitochondrial biogenesis refers to the synthesis of new mitochondria from existing mitochondria, mostly through the PGC-1α/Nrfs/TFAM signalling pathway. Resveratrol (Res), a silencing information regulator 2-related enzyme 1 (Sirt1) agonist, has been shown to upregulate the level of Sirt1 and the expression of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α). We speculate that Res has a protective effect on hyperoxia-induced brain injury through mitochondrial biogenesis.

METHODS

Sprague-Dawley (SD) pups were randomly divided into the nonhyperoxia (NN) group, the nonhyperoxia with dimethyl sulfoxide (ND) group, the nonhyperoxia with Res (NR) group, the hyperoxia (HN) group, the hyperoxia with dimethyl sulfoxide (HD) group, and the hyperoxia with Res (HR) group within 12 h after birth. The HN, HD, and HR groups were placed in a high-oxygen environment (80‒85%), and the other three groups were placed in the standard atmosphere. The NR and HR groups were given 60 mg/kg Res every day, the ND and HD groups were given the same dose of dimethyl sulfoxide (DMSO) every day, and the NN and HN groups were given the same dose of normal saline every day. On postnatal day (PN) 1, PN7, and PN14, brain samples were acquired for HE staining to assess pathology, TUNEL to detect apoptosis, and real-time quantitative polymerase chain reaction and immunoblotting to detect the expression levels of Sirt1, PGC-1α, nuclear respiratory factor 1 (Nrf1), nuclear respiratory factor 2 (Nrf2) and mitochondrial transcription factor A (TFAM) in brain tissue.

RESULTS

Hyperoxia induced brain tissue injury; increased brain tissue apoptosis; inhibited Sirt1, PGC-1α, Nrf1, Nrf2, TFAM mRNA expression in mitochondria; diminished the ND1 copy number and ND4/ND1 ratio; and decreased Sirt1, PGC-1α, Nrf1, Nrf2, and TFAM protein levels in the brain. In contrast, Res reduced brain injury and attenuated brain tissue apoptosis in neonatal pups and increased the levels of the corresponding indices.

CONCLUSION

Res has a protective effect on hyperoxia-induced brain injury in neonatal SD pups by upregulating Sirt1 and stimulating the PGC-1α/Nrfs/TFAM signalling pathway for mitochondrial biogenesis.

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.

Early-life factors associated with neurobehavioral outcomes in preterm infants during NICU hospitalization

BACKGROUND

The aim of this study was to investigate the influence of early-life pain/stress and medical characteristics on neurobehavioral outcomes in preterm infants.

METHODS

A prospective cohort study was conducted with 92 preterm infants (28-32 weeks gestational age [GA]). Early-life pain/stress was measured via the Neonatal Infant Stressor Scale (NISS) during the first 28 days of NICU hospitalization. Neurobehavioral outcomes were evaluated using the NICU Network Neurobehavioral Scale at 36-38 weeks post-menstrual age. Functional regression and machine learning models were performed to investigate the predictors of neurobehavioral outcomes.

RESULTS

Infants experienced daily acute pain/stress (24.99 ± 7.13 frequencies) and chronic events (41.13 ± 17.81 h). Up to 12 days after birth, both higher acute and chronic NISS scores were associated with higher stress scores; and higher chronic NISS scores were also related to lower self-regulation and quality of movement. Younger GA predicted worse neurobehavioral outcomes; GA < 31.57 weeks predicted worse stress/abstinence, self-regulation, and excitability; GA < 30.57 weeks predicted poor quality of movement. A higher proportion of maternal breastmilk intake predicted better self-regulation, excitability, and quality of movement in older GA infants.

CONCLUSIONS

Preterm infants are vulnerable to the impact of early-life pain/stress. Neurobehavioral outcomes are positively associated with increased GA and higher maternal breastmilk intake.

IMPACT

During the first 12 days of life, preterm infant neurobehavioral outcomes were vulnerable to the negative impact of acute and chronic pain/stress. Future research is warranted to investigate the long-term effects of early-life pain/stress on neurobehavioral outcomes. Gestational age remains one of the critical factors to predict neurobehavioral outcomes in preterm infants; older gestational age significantly predicted better neurobehavioral outcomes. Feeding with a higher proportion of maternal breastmilk predicted better neurobehavioral outcomes. Future research is warranted to investigate how maternal breastmilk may buffer the negative effects of early-life pain/stress on neurobehavioral outcomes.

Regional oxygenation, perfusion and body and/or head position: Are preterm infants adversely impacted? A systematic review

This review addresses regional oxygenation and perfusion changes for preterm infants and changes with body position, with or without head rotation. Future directions for improving neurodevelopmental and clinical outcomes are suggested. The MEDLINE, Embase and Scopus databases were searched up to July 2021. Fifteen out of 470 studies met the inclusion criteria. All were prospective, observational studies with a moderate risk of bias. Significant variation was found for the baseline characteristics of the cohort, postnatal ages, and respiratory support status at the time of monitoring. When placed in a non-supine position, preterm infants showed a transient reduction in cardiac output and stroke volume without changes to heart rate or blood pressure. No studies reported on long-term neurodevelopmental outcomes. Overall, side lying or prone position does not appear to adversely affect regional, and specifically cerebral, oxygenation or cerebral perfusion. The effect of head rotation on regional oxygenation and perfusion remains unclear.

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.

Oligodendrocyte Development and Implication in Perinatal White Matter Injury

Perinatal white matter injury (WMI) is the most common brain injury in premature infants and can lead to life-long neurological deficits such as cerebral palsy. Preterm birth is typically accompanied by inflammation and hypoxic-ischemic events. Such perinatal insults negatively impact maturation of oligodendrocytes (OLs) and cause myelination failure. At present, no treatment options are clinically available to prevent or cure WMI. Given that arrested OL maturation plays a central role in the etiology of perinatal WMI, an increased interest has emerged regarding the functional restoration of these cells as potential therapeutic strategy. Cell transplantation and promoting endogenous oligodendrocyte function are two potential options to address this major unmet need. In this review, we highlight the underlying pathophysiology of WMI with a specific focus on OL biology and their implication for the development of new therapeutic targets.

A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows

The autonomic nervous system (ANS) is one of the main biological systems that regulates the body's physiology. Autonomic nervous system regulatory capacity begins before birth as the sympathetic and parasympathetic activity contributes significantly to the fetus' development. In particular, several studies have shown how vagus nerve is involved in many vital processes during fetal, perinatal, and postnatal life: from the regulation of inflammation through the anti-inflammatory cholinergic pathway, which may affect the functioning of each organ, to the production of hormones involved in bioenergetic metabolism. In addition, the vagus nerve has been recognized as the primary afferent pathway capable of transmitting information to the brain from every organ of the body. Therefore, this hypothesis paper aims to review the development of ANS during fetal and perinatal life, focusing particularly on the vagus nerve, to identify possible "critical windows" that could impact its maturation. These "critical windows" could help clinicians know when to monitor fetuses to effectively assess the developmental status of both ANS and specifically the vagus nerve. In addition, this paper will focus on which factors-i.e., fetal characteristics and behaviors, maternal lifestyle and pathologies, placental health and dysfunction, labor, incubator conditions, and drug exposure-may have an impact on the development of the vagus during the above-mentioned "critical window" and how. This analysis could help clinicians and stakeholders define precise guidelines for improving the management of fetuses and newborns, particularly to reduce the potential adverse environmental impacts on ANS development that may lead to persistent long-term consequences. Since the development of ANS and the vagus influence have been shown to be reflected in cardiac variability, this paper will rely in particular on studies using fetal heart rate variability (fHRV) to monitor the continued growth and health of both animal and human fetuses. In fact, fHRV is a non-invasive marker whose changes have been associated with ANS development, vagal modulation, systemic and neurological inflammatory reactions, and even fetal distress during labor.