Trends of neonatal hypoxic-ischemic encephalopathy prevalence and associated risk factors in the United States, 2010 to 2018

Echinatin alleviates inflammation and pyroptosis in hypoxic-ischemic brain damage by inhibiting TLR4/ NF-κB pathway

Hypoxic ischemic encephalopathy (HIE) is a primary cause of neonatal death and disabilities. The pathogenetic process of HIE is closely associated with neuroinflammation. Therefore, targeting and suppressing inflammatory pathways presents a promising therapeutic strategy for the treatment of HIE. Echinatin is an active component of glycyrrhiza, with anti-inflammatory and anti-oxidative properties. It is commonly combined with other traditional Chinese herbs to exert heat-clearing and detoxifying effects. This study aimed to investigate the anti-inflammatory and neuroprotective effects of Echinatin in neonatal rats with hypoxic-ischemic brain damage, as well as in PC12 cells exposed to oxygen-glucose deprivation (OGD). In vivo, Echinatin effectively reduced cerebral edema and infarct volume, protected brain tissue morphology, improved long-term behavioral functions, and inhibited microglia activation. These effects were accompanied by the downregulation of inflammatory factors and pyroptosis markers. The RNA sequencing analysis revealed an enrichment of inflammatory genes in rats with hypoxic-ischemic brain damage, and Protein-protein interaction (PPI) network analysis identified TLR4, MyD88, and NF-κB as the key regulators. In vitro, Echinatin reduced the levels of TLR4 relevant proteins, inhibited nuclear translocation of NF-κB, reduced the expression of downstreams inflammatory cytokines and pyroptosis proteins, and prevented cell membrane destructions. These findings demonstrated that Echinatin could inhibit the TLR4/NF-κB pathway, thereby alleviating neuroinflammation and pyroptosis. This suggests that Echinatin could be a potential candidate for the treatment of HIE.

[Investigation of a French cohort of neonatal anoxo-ischemic encephalopathy in the era of therapeutic hypothermia: Questions and answers]

OBJECTIVE

To improve knowledge of neonatal hypoxic-ischemic encephalopathy, a prospective, nationwide, population-based cohort of affected children is being set up between September 2015 and March 2017.

METHODS

During this period, 794 cases are collected, with information on pregnancy, delivery, neonatal stay and outcome at the end of hospitalization. Clinical and parental questionnaire follow-up is planned until the child is 4 years old.

RESULTS

This article presents the clinical presentation of the newborns included, the analysis of factors associated with short-term outcome at hospital discharge and the organizational factors associated with treatment with therapeutic hypothermia.

CONCLUSION

These data illustrate the value of a prospective cohort to analyze the management of anoxo-ischemic encephalopathy in France.

Relationship between EEG spectral power and dysglycemia with neurodevelopmental outcomes after neonatal encephalopathy

OBJECTIVE

We investigated how electroencephalography (EEG) quantitative measures and dysglycemia relate to neurodevelopmental outcomes following neonatal encephalopathy (NE).

METHODS

This retrospective study included 90 neonates with encephalopathy who received therapeutic hypothermia. EEG absolute spectral power was calculated during post-rewarming and 2-month follow-up. Measures of dysglycemia (hypoglycemia, hyperglycemia, and glycemic lability) and glucose variability were computed for the first 48 h of life. We evaluated the ability of EEG and glucose measures to predict neurodevelopmental outcomes at ≥ 18 months, using logistic regressions (with area under the receiver operating characteristic [AUROC] curves).

RESULTS

The post-rewarming global delta power (average all electrodes), hyperglycemia and glycemic lability predicted moderate/severe neurodevelopmental outcome separately (AUROC = 0.8, 95%CI [0.7,0.9], p < .001) and even more so when combined (AUROC = 0.9, 95%CI [0.8,0.9], p < .001). After adjusting for NE severity and magnetic resonance imaging (MRI) brain injury, only global delta power remained significantly associated with moderate/severe neurodevelopmental outcome (odds ratio [OR] = 0.9, 95%CI [0.8,1.0], p = .04), gross motor delay (OR = 0.9, 95%CI [0.8,1.0], p = .04), global developmental delay (OR = 0.9, 95%CI [0.8,1.0], p = .04), and auditory deficits (OR = 0.9, 95%CI [0.8,1.0], p = .03).

CONCLUSIONS

In NE, global delta power post-rewarming was predictive of outcomes at ≥ 18 months.

SIGNIFICANCE

EEG markers post-rewarming can aid prediction of neurodevelopmental outcomes following NE.

Clinical exome sequencing uncovers genetic disorders in neonates with suspected hypoxic-ischemic encephalopathy: A retrospective analysis

Hypoxic-ischemic encephalopathy (HIE) occurs in up to 7 out of 1000 births and accounts for almost a quarter of neonatal deaths worldwide. Despite the name, many newborns with HIE have little evidence of perinatal hypoxia. We hypothesized that some infants with HIE have genetic disorders that resemble encephalopathy. We reviewed genetic results for newborns with HIE undergoing exome or genome sequencing at a clinical laboratory (2014-2022). Neonates were included if they had a diagnosis of HIE and were delivered ≥35 weeks. Neonates were excluded for cardiopulmonary pathology resulting in hypoxemia or if neuroimaging suggested postnatal hypoxic-ischemic injury. Of 24 patients meeting inclusion criteria, six (25%) were diagnosed with a genetic condition. Four neonates had variants at loci linked to conditions with phenotypic features resembling HIE, including KIF1A, GBE1, ACTA1, and a 15q13.3 deletion. Two additional neonates had variants in genes not previously associated with encephalopathy, including DUOX2 and PTPN11. Of the six neonates with a molecular diagnosis, two had isolated HIE without apparent comorbidities to suggest a genetic disorder. Genetic diagnoses were identified among neonates with and without sentinel labor events, abnormal umbilical cord gasses, and low Apgar scores. These results suggest that genetic evaluation is clinically relevant for patients with perinatal HIE.

Racial and geographic disparities in neonatal brain care

In this review, we explore race-based disparities in neonatology and their impact on brain injury and neurodevelopmental outcomes. We discuss the historical context of healthcare discrimination, focusing on the post-Civil War era and the segregation of healthcare facilities. We highlight the increasing disparity in infant mortality rates between Black and White infants, with premature birth being a major contributing factor, and emphasize the role of prenatal factors such as metabolic syndrome and toxic stress in affecting neonatal health. Furthermore, we examine the geographic and historical aspects of racial disparities, including the consequences of redlining and limited access to healthcare facilities or nutritious food options in Black communities. Finally, we delve into the higher incidence of brain injuries in Black neonates, as well as disparities in adverse neurodevelopmental outcome. This evidence underscores the need for comprehensive efforts to address systemic racism and provide equitable access to healthcare resources.

Maternal levels of care during pregnancy influence labor and delivery outcomes - present practices and future priorities

Neonatal encephalopathy (NE) is a diagnosis that is usually unexpected. Though there are many risk factors for the condition and multiple theories as to its genesis, the majority of cases cannot be predicted prior to the occurrence of the clinical syndrome. Indeed, it is common for a pregnant person to have multiple risk factors and a completely healthy child. Conversely, people with seemingly no risk factors may go on to have a profoundly affected child. In this synopsis we review risk factors, potential mechanisms for encephalopathy, the complicated issue of choosing which morbidity to take on and how the maternal level of care may influence outcomes. The reader should be able to better understand the limitations of current testing and the profound levels of maternal intervention that have been undertaken to prevent or mitigate the rare, but devastating occurrence of NE. Further, we suggest candidate future approaches to prevent the occurrence, and decrease the severity of NE. Any future improvements in the NE syndrome cannot be achieved via obstetric intervention and management alone or conversely, by improvements in treatments offered post-birth. Multidisciplinary approaches that encompass prepregnancy health, pregnancy care, intrapartum management and postpartum care will be necessary.

Impact of sex, race, and social determinants of health on neonatal outcomes

Despite the global improvements in neonatal outcomes, mortality and morbidity rates among preterm infants are still unacceptably high. Therefore, it is crucial to thoroughly analyze the factors that affect these outcomes, including sex, race, and social determinants of health. By comprehending the influence of these factors, we can work towards reducing their impact and enhancing the quality of neonatal care. This review will summarize the available evidence on sex differences, racial differences, and social determinants of health related to neonates. This review will discuss sex differences in neonatal outcomes in part I and racial differences with social determinants of health in part II. Research has shown that sex differences begin to manifest in the early part of the pregnancy. Hence, we will explore this topic under two main categories: (1) Antenatal and (2) Postnatal sex differences. We will also discuss long-term outcome differences wherever the evidence is available. Multiple factors determine health outcomes during pregnancy and the newborn period. Apart from the genetic, biological, and sex-based differences that influence fetal and neonatal outcomes, racial and social factors influence the health and well-being of developing humans. Race categorizes humans based on shared physical or social qualities into groups generally considered distinct within a given society. Social determinants of health (SDOH) are the non-medical factors that influence health outcomes. These factors can include a person's living conditions, access to healthy food, education, employment status, income level, and social support. Understanding these factors is essential in developing strategies to improve overall health outcomes in communities.

Magnesium sulfate and risk of hypoxic-ischemic encephalopathy in a high-risk cohort

BACKGROUND

Hypoxic-ischemic encephalopathy contributes to morbidity and mortality among neonates ≥36 weeks of gestation. Evidence of preventative antenatal treatment is limited. Magnesium sulfate has neuroprotective properties among preterm fetuses. Hypertensive disorders of pregnancy are a risk factor for hypoxic-ischemic encephalopathy, and magnesium sulfate is recommended for maternal seizure prophylaxis among patients with preeclampsia with severe features.

OBJECTIVE

(1) Determine trends in the incidence of hypertensive disorders of pregnancy, antenatal magnesium sulfate, and hypoxic-ischemic encephalopathy; (2) evaluate the association between hypertensive disorders of pregnancy and hypoxic-ischemic encephalopathy; and (3) evaluate if, among patients with hypertensive disorders of pregnancy, the odds of hypoxic-ischemic encephalopathy is mitigated by receipt of antenatal magnesium sulfate.

STUDY DESIGN

We analyzed a prospective cohort of live births ≥36 weeks of gestation between 2012 and 2018 within the California Perinatal Quality Care Collaborative registry, linked with the California Department of Health Care Access and Information files. We used Cochran-Armitage tests to assess trends in hypertensive disorders, encephalopathy diagnoses, and magnesium sulfate utilization and compared demographic factors between patients with or without hypertensive disorders of pregnancy or treatment with magnesium sulfate. Hierarchical logistic regression models were built to explore if hypertensive disorders of pregnancy were associated with any severity and moderate/severe hypoxic-ischemic encephalopathy. Separate hierarchical logistic regression models were built among those with hypertensive disorders of pregnancy to evaluate the association of magnesium sulfate with hypoxic-ischemic encephalopathy.

RESULTS

Among 44,314 unique infants, the diagnosis of hypoxic-ischemic encephalopathy, maternal hypertensive disorders of pregnancy, and the use of magnesium sulfate increased over time. Compared with patients with hypertensive disorders of pregnancy alone, patients with hypertensive disorders treated with magnesium sulfate represented a high-risk population. They were more likely to be publicly insured, born between 36 and 38 weeks of gestation, be small for gestational age, have lower Apgar scores, require a higher level of resuscitation at delivery, have prolonged rupture of membranes, experience preterm labor and fetal distress, and undergo operative delivery (all P<.002). Hypertensive disorders of pregnancy were associated with hypoxic-ischemic encephalopathy (adjusted odds ratio, 1.26 [95% confidence interval, 1.13-1.40]; P<.001) and specifically moderate/severe hypoxic-ischemic encephalopathy (adjusted odds ratio, 1.26 [95% confidence interval, 1.11-1.42]; P<.001). Among patients with hypertensive disorders of pregnancy, treatment with magnesium sulfate was associated with 29% reduction in the odds of neonatal hypoxic-ischemic encephalopathy (adjusted odds ratio, 0.71 [95% confidence interval, 0.52-0.97]; P=.03) and a 37% reduction in the odds of moderate/severe neonatal hypoxic-ischemic encephalopathy (adjusted odds ratio, 0.63 [95% confidence interval, 0.42-0.94]; P=.03).

CONCLUSION

Hypertensive disorders of pregnancy are associated with hypoxic-ischemic encephalopathy and, specifically, moderate/severe disease. Among people with hypertensive disorders, receipt of antenatal magnesium sulfate is associated with a significant reduction in the odds of hypoxic-ischemic encephalopathy and moderate/severe disease in a neonatal cohort admitted to neonatal intensive care unit at ≥36 weeks of gestation. The findings of this observational study cannot prove causality and are intended to generate hypotheses for future clinical trials on magnesium sulfate in term infants.

Gross and Histologic Placental Abnormalities Associated With Neonatal Hypoxic-Ischemic Encephalopathy

OBJECTIVE

To elucidate particular placental pathology findings that are associated with hypoxic ischemic encephalopathy (HIE) and determine which patterns are associated with adverse fetal/neonatal outcomes.

STUDY DESIGN

Multi-institutional retrospective case-control study of newborns with HIE (2002-2022) and controls. Four perinatal pathologists performed gross and histologic evaluation of placentas of cases and controls.

RESULTS

A total of 265 placentas of neonates with HIE and 122 controls were examined. Infants with HIE were more likely to have anatomic umbilical cord abnormalities (19.7% vs 7.4%, P = .003), fetal inflammatory response in the setting of amniotic fluid infection (27.7% vs 13.9%, P = .004), and fetal vascular malperfusion (30.6% vs 9.0%, P = <.001) versus controls. Fetal vascular malperfusion with maternal vascular malperfusion was more common in those who died of disease (P = .01).

CONCLUSION

Placental pathology examination of neonates with HIE may improve our understanding of this disorder and its adverse outcomes.

Effect of gestational age on cerebral lesions in neonatal encephalopathy

OBJECTIVE

To determine the risk on brain lesions according to gestational age (GA) in neonates with neonatal encephalopathy.

DESIGN

Secondary analysis of the prospective national French population-based cohort, Long-Term Outcome of NeonataL EncePhALopathy.

SETTING

French neonatal intensive care units.

PATIENTS

Neonates with moderate or severe neonatal encephalopathy (NE) born at ≥34 weeks' GA (wGA) between September 2015 and March 2017.

MAIN OUTCOME MEASURES

The results of MRI performed within the first 12 days were classified in seven injured brain regions: basal ganglia and thalami, white matter (WM), cortex, posterior limb internal capsule, corpus callosum, brainstem and cerebellum. A given infant could have several brain structures affected. Risk of brain lesion according to GA was estimated by crude and adjusted ORs (aOR).

RESULTS

MRI was available for 626 (78.8%) of the 794 included infants with NE. WM lesions predominated in preterm compared with term infants. Compared with 39-40 wGA neonates, those born at 34-35 wGA and 37-38 wGA had greater risk of WM lesions after adjusting for perinatal factors (aOR 4.0, 95% CI (1.5 to 10.7) and ORa 2.0, 95% CI (1.1 to 3.5), respectively).

CONCLUSION

WM is the main brain structure affected in late-preterm and early-term infants with NE, with fewer WM lesions as GA increases. This finding could help clinicians to estimate prognosis and improve the understanding of the pathophysiology of NE.

TRIAL REGISTRATION NUMBER

NCT02676063, ClinicalTrials.gov.

Growth and developmental outcomes of infants with hypoxic ischemic encephalopathy

Despite advances in obstetric care, hypoxic ischemic encephalopathy (HIE) remains a significant disease burden. We determined the national trends of HIE prevalence, therapeutic hypothermia (TH) use, mortality, and outcomes from 2012 to 2019. This study included term infants diagnosed with HIE between 2012 and 2019 from the National Health Insurance Service database. The prevalence of HIE was 2.4 per 1000 births without significant change during the period. TH was performed in approximately 6.7% of infants with HIE, and the annual variation ranged from 2.4 to 12.5%. The mortality among all term infants with HIE was 4.6%. The mortality rate among infants with HIE and TH significantly declined from 40 to 16.9% during the eight years. Infants with TH had higher mortality, increased use of inhaled nitric oxide, and more invasive ventilator use, indicating greater disease severity in the TH group. Infants with TH also showed significantly poorer outcomes, including delayed development, cerebral palsy, sensorineural hearing loss, and seizure, compared to infants without TH (p < 0.0001). With the increasing application of TH, mortality and developmental outcomes among infants with HIE have been improving in the past eight years in Korea. Further efforts to improve outcomes should be needed.

The Placenta and Neonatal Encephalopathy with a Focus on Hypoxic-Ischemic Encephalopathy

Background: Placental examination is important for its diagnostic immediacy to correlate with maternal and/or fetal complications and parturitional difficulties. In a broader context, clinicopathologic studies of the placenta have addressed a range of pathogenetic questions that have led to conclusive and inconclusive results and interpretations. Methods: Recent standardized morphologic criteria and terminology of placental lesions have facilitated the ability to compare findings from studies that have focused on complications and outcomes of pregnancy. This review is an evaluation of recent studies on placental lesions associated with hypoxic-ischemic encephalopathy (HIE). Conclusion: No apparent consensus exists on whether it is fetal inflammation with the release of cytokines or chronic maternal and/or fetal vascular malperfusion is responsible for HIE with a lowering of the threshold for hypoxic ischemia. The counter argument is that HIE occurs solely as an intrapartum event. Additional investigation is necessary.

Evolution of swallowing and feeding abilities of neonates with hypoxic-ischaemic encephalopathy during hospitalisation: A case series

PURPOSE

To describe the evolution of swallowing and feeding abilities of neonates with hypoxic-ischaemic encephalopathy (HIE) during hospitalisation.

METHOD

A longitudinal cohort study was used. Twenty-nine participants (median age 39.0 weeks [IQR = 2.0 weeks]) with mild (n = 7), moderate (n = 19) and severe (n = 3) HIE were included. Clinical swallowing and feeding assessments were conducted at introduction of oral feeds and at discharge using the Neonatal Feeding Assessment Scale (NFAS). Videofluoroscopic swallow studies (VFSS) supplemented the NFAS before discharge.

RESULT

Approximately two thirds of participants showed symptoms of oropharyngeal dysphagia (OPD) during initial NFAS and VFSS. Significantly fewer OPD symptoms occurred at discharge NFAS (p = 0.004). Endurance during non-nutritive sucking (p < 0.001) and nutritive sucking (p < 0.001) significantly improved. Nine participants (31.0%) demonstrated penetration or aspiration. Most aspiration events were silent (60%). Instrumental assessment identified pharyngeal phase dysphagia more effectively than bedside evaluation. High proportions of participants displayed OPD symptoms regardless of HIE severity. The correlation between OPD severity and the length of hospitalisation (p = 0.052) was not significant.

CONCLUSION

All grades of HIE should be considered for early intervention by speech-language pathologists before discharge. Findings may be valuable to neonatal feeding teams.

Perinatal Hypoxic-Ischemic Encephalopathy: Incidence Over Time Within a Modern US Birth Cohort

BACKGROUND

Recent studies suggest that the incidence of perinatal hypoxic-ischemic encephalopathy (HIE) may be increasing in developed countries. However, this observed increase may be due to increased ascertainment and increased treatment with therapeutic hypothermia rather than an increase in disease burden. In a US population-based cross-sectional study, we determined the incidence of perinatal HIE over time.

METHODS

The study population included all 289,793 live-born infants ≥35 weeks gestational age born at 15 Kaiser Permanente Northern California hospitals between 2012 and 2019. Perinatal HIE was defined as the presence of both neonatal acidosis (i.e., cord blood pH < 7 or base deficit ≥10, or base deficit ≥10 on first infant gas) and neonatal encephalopathy confirmed by medical record review. Hospital discharge diagnoses of HIE were determined by extracting International Classification of Disease diagnostic codes for HIE assigned upon hospital discharge.

RESULTS

The population incidence of perinatal HIE was 1.7 per 1000. Although the incidence of perinatal HIE did not change significantly, both hospital discharge diagnoses of HIE and treatment with therapeutic hypothermia increased significantly during the study period. The sensitivity and positive predictive value of a hospital discharge diagnosis of HIE for identifying perinatal HIE confirmed by chart review were 72% and 79%, respectively.

CONCLUSIONS

During the study years, the incidence of perinatal HIE remained stable despite increases in hospital discharge diagnoses of HIE and in the use of therapeutic hypothermia. Our findings underscore the importance of applying stringent diagnostic criteria when diagnosing this complex condition.

Acquired Brain Injuries Across the Perinatal Spectrum: Pathophysiology and Emerging Therapies

The development of the central nervous system can be directly disrupted by a variety of acquired factors, including infectious, inflammatory, hypoxic-ischemic, and toxic insults. Influences external to the fetus also impact neurodevelopment, including placental health, maternal comorbidities, adverse experiences, environmental exposures, and social determinants of health. Acquired perinatal brain insults tend to affect the developing brain in a stage-specific manner that reflects the susceptible cell types, developmental processes, and risk factors present at the time of the insult. In this review, we discuss the pathophysiology, neurodevelopmental outcomes, and management of common acquired perinatal brain conditions. In the fetal brain, we divide insults based on trimester, and in the postnatal brain, we focus on common pathologies that have a presentation dependent on gestational age at birth: white matter injury and germinal matrix hemorrhage/intraventricular hemorrhage in preterm infants and hypoxic-ischemic encephalopathy in term infants. Although specific treatments for fetal and newborn brain disorders are currently limited, we emphasize therapies in preclinical or early clinical phases of the development pipeline. The growing number of novel cell type- and stage-specific emerging therapies suggests that in the near future we may have a dramatically improved ability to treat acquired perinatal brain disorders and to mitigate the associated neurodevelopmental consequences.

Outcomes of Neonates with Hypoxic-Ischemic Encephalopathy Treated with Magnesium Sulfate: A Systematic Review with Meta-analysis

OBJECTIVE

To assess magnesium sulfate (MgSO4) as a neuroprotective agent in hypoxic-ischemic encephalopathy.

STUDY DESIGN

For this systematic review, PubMed, EMBASE, the Cochrane Library, EMCARE, and MedNar were searched in November 2022 for randomized controlled trials (RCTs). Meta-analysis was conducted using Stata 16.0 and RevMan 5.3.

RESULTS

Twenty RCTs with a total sample size of 1485 were included, of which 16 were from settings where therapeutic hypothermia (TH) was not offered. Regarding MgSO4 in settings where TH was not offered, only 1 study evaluated composite outcome of death or disability at ≥18 months and reported such poor outcome in 8 of 14 control infants and 4 of 8 in the MgSO4 group. MgSO4 was not associated with mortality (RR, 0.86; 95% CI, 0.72-1.03; 13 RCTs) or hypotension (RR, 1.02; 95% CI, 0.88-1.18; 5 RCTs). Thirteen studies reported that MgSO4 improved in-hospital outcomes, such as reduced seizure burden and improved neurological status at discharge. MgSO4 reduced the risk of poor suck feeds (RR, 0.52; 95% CI, 0.40-0.68; 6RCTs) and abnormal electroencephalogram (RR, 0.64; 95% CI, 0.45-0.93; 5 RCTs). Certainty of evidence was moderate for mortality and low or very low for other outcomes. For studies with MgSO4 as an adjunct to TH, none reported on death or neurodevelopmental disability at ≥18 months. MgSO4 was not associated with mortality (RR, 0.65; 95% CI, 0.34-1.27; 3 RCTs) or hypotension (RR, 1.0; 95% CI, 0.71-1.40; 3 RCTs).

CONCLUSIONS

Evidence around long-term outcomes of MgSO4 when used with or without TH was scant. MgSO4 therapy may improve in-hospital neurological outcomes without affecting mortality in settings where TH is not offered. Well-designed RCTs for neuroprotection are needed, especially in low-resource settings.

TRIAL REGISTRATION

"Open Science Forum" (https://doi.org/10.17605/OSF.IO/FRM4D).

FGF21 modulates hippocampal cold-shock proteins and CA2-subregion proteins in neonatal mice with hypoxia-ischemia

BACKGROUND

Fibroblast growth factor 21 (FGF21) is a neuroprotectant with cognitive enhancing effects but with poorly characterized mechanism(s) of action, particularly in females. Prior studies suggest that FGF21 may regulate cold-shock proteins (CSPs) and CA2-marker proteins in the hippocampus but empirical evidence is lacking.

METHODS

We assessed in normothermic postnatal day (PND) 10 female mice, if hypoxic-ischemic (HI) brain injury (25 min 8% O2/92% N2) altered endogenous levels of FGF21 in serum or in the hippocampus, or its receptor β-klotho. We also tested if systemic administration of FGF21 (1.5 mg/kg) modulated hippocampal CSPs or CA2 proteins. Finally, we measured if FGF21 therapy altered markers of acute hippocampal injury.

RESULTS

HI increased endogenous serum FGF21 (24 h), hippocampal tissue FGF21 (4d), and decreased hippocampal β-klotho levels (4d). Exogenous FGF21 therapy modulated hippocampal CSP levels, and dynamically altered hippocampal CA2 marker expression (24 h and 4d). Finally, FGF21 ameliorated neuronal damage markers at 24 h but did not affect GFAP (astrogliosis) or Iba1 (microgliosis) levels at 4d.

CONCLUSIONS

FGF21 therapy modulates CSP and CA2 protein levels in the injured hippocampus. These proteins serve different biological functions, but our findings suggest that FGF21 administration modulates them in a homeostatic manner after HI.

IMPACT

Hypoxic-ischemic (HI) injury in female post-natal day (PND) 10 mice decreases hippocampal RNA binding motif 3 (RBM3) levels in the normothermic newborn brain. HI injury in normothermic newborn female mice alters serum and hippocampal fibroblast growth factor 21 (FGF21) levels 24 h post-injury. HI injury in normothermic newborn female mice alters hippocampal levels of N-terminal EF-hand calcium binding protein 2 (NECAB2) in a time-dependent manner. Exogenous FGF21 therapy ameliorates the HI-mediated loss of hippocampal cold-induced RNA-binding protein (CIRBP). Exogenous FGF21 therapy modulates hippocampal levels of CA2-marker proteins after HI.

Functional neuropathology of neonatal hypoxia-ischemia by single-mouse longitudinal electroencephalography

OBJECTIVE

Neonatal cerebral hypoxia-ischemia (HI) results in symptomatic seizures and long-term neurodevelopmental disability. The Rice-Vannucci model of rodent neonatal HI has been used extensively to examine and translate the functional consequences of acute and chronic HI-induced encephalopathy. Yet, longitudinal electrophysiological characterization of this brain injury model has been limited by the size of the neonatal mouse's head and postnatal maternal dependency. We overcome this challenge by employing a novel method of longitudinal single-mouse electroencephalography (EEG) using chronically implanted subcranial electrodes in the term-equivalent mouse pup. We characterize the neurophysiological disturbances occurring during awake and sleep states in the acute and chronic phases following newborn brain injury.

METHODS

C57BL/6 mice underwent long-term bilateral subcranial EEG and electromyographic electrode placement at postnatal day 9 followed by unilateral carotid cauterization and exposure to 40 minutes of hypoxia the following day. EEG recordings were obtained prior, during, and intermittently after the HI procedure from postnatal day 10 to weaning age. Quantitative EEG and fast Fourier transform analysis were used to evaluate seizures, cortical cerebral dysfunction, and disturbances in vigilance states.

RESULTS

We observed neonatal HI-provoked electrographic focal and bilateral seizures during or immediately following global hypoxia and most commonly contralateral to the ischemic injury. Spontaneous chronic seizures were not seen. Injured mice developed long-term asymmetric EEG background attenuation in all frequencies and most prominently during non-rapid eye movement (NREM) sleep. HI mice also showed transient impairments in vigilance state duration and transitions during the first 2 days following injury.

SIGNIFICANCE

The functional burden of mouse neonatal HI recorded by EEG resembles closely that of the injured human newborn. The use of single-mouse longitudinal EEG in this immature model can advance our understanding of the developmental and pathophysiological mechanisms of neonatal cerebral injury and help translate novel therapeutic strategies against this devastating condition.