Necrotizing enterocolitis induces T lymphocyte-mediated injury in the developing mammalian brain.

Necrotizing enterocolitis (NEC) causes acute intestinal necrosis in premature infants and is associated with severe neurological impairment. In NEC, Toll-like receptor 4 is activated in the intestinal epithelium, and NEC-associated brain injury is characterized by microglial activation and white matter loss through mechanisms that remain unclear. We now show that the brains of mice and humans with NEC contained CD4+ T lymphocytes that were required for the development of brain injury. Inhibition of T lymphocyte influx into the brains of neonatal mice with NEC reduced inflammation and prevented myelin loss. Adoptive intracerebroventricular delivery of gut T lymphocytes from mice with NEC into Rag1 -/- recipient mice lacking CD4+ T cells resulted in brain injury. Brain organoids derived from mice with or without NEC and from human neuronal progenitor cells revealed that IFN-γ release by CD4+ T lymphocytes induced microglial activation and myelin loss in the organoids. IFN-γ knockdown in CD4+ T cells derived from mice with NEC abrogated the induction of NEC-associated brain injury after adoptive transfer to naïve Rag1 -/- recipient mice. T cell receptor sequencing revealed that NEC mouse brain-derived T lymphocytes shared homology with gut T lymphocytes from NEC mice. Intraperitoneal injection of NEC gut-derived CD4+ T lymphocytes into naïve Rag1 -/- recipient mice induced brain injury, suggesting that gut-derived T lymphocytes could mediate neuroinflammation in NEC. These findings indicate that NEC-associated brain injury may be induced by gut-derived IFN-γ-releasing CD4+ T cells, suggesting that early management of intestinal inflammation in children with NEC could improve neurological outcomes.

Clinically Silent Brain Injury and Perioperative Neurological Events in Patients With Left Ventricular Assist Device: A Brain Autopsy Study.

Current studies underestimate the prevalence of brain injury in patients with left ventricular assist devices (LVADs), as CT scans are not sensitive in detecting cerebral ischemia. Using postmortem neuropathological evaluation, we sought to characterize the types and risk factors of brain injury in LVAD patients. We reviewed 24 LVAD patients who underwent brain autopsy with gross and microscopic examinations from 1993 through 2019 at a single tertiary center. Patients who expired less than 7 days after implantation or who underwent explantation more than 7 days before death were excluded. Our study demonstrated that all LVAD nonsurvivors developed brain injury. The most common brain injury was hemorrhage (71%), followed by infarct (42%) and hypoxic ischemic brain injury (HIBI) (33%), and 10 patients (42%) presented with more than 1 brain injury. Cerebral microbleeds (CMBs) and intracranial hemorrhage were present in 33% and 42%, respectively. In those with intracranial hemorrhage, subarachnoid hemorrhage (25%) and intracerebral hemorrhage (25%) were more common than subdural hematoma (4%). Intracranial hemorrhage was associated with driveline infection (P = 0.047), and HIBI was associated with prior history of chronic obstructive pulmonary disease (P = 0.037). Fourteen (60%) had clinically silent brain injury with 65% of hemorrhages and 70% of infarcts being silent. However, the impact of silent brain injury on neurologic outcome and mortality remains unclear. Standardized neurologic monitoring and surveillance are recommended to better detect these clinically silent brain injury.

Acute Brain Injury in Infant Venoarterial Extracorporeal Membrane Oxygenation: An Autopsy Study.

OBJECTIVES: Characterization of the types and timing of acute brain injury in infant autopsy patients after extracorporeal membrane oxygenation. DESIGN: Retrospective cohort study. SETTING: Single tertiary-care center. PATIENTS: Infants supported on extracorporeal membrane oxygenation. MEASUREMENTS AND MAIN RESULTS: Clinical and pathologic records were reviewed for infant extracorporeal membrane oxygenation patients who had undergone brain autopsy in a single center between January 2009 and December 2018. Twenty-four patients supported on venoarterial extracorporeal membrane oxygenation had postmortem examination with brain autopsy. Median age at extracorporeal membrane oxygenation initiation was 82 days (interquartile range, 11-263 d), median age at time of death was 20 weeks (interquartile range, 5-44 wk), and median extracorporeal membrane oxygenation support duration was 108 hours (interquartile range, 35-366 hr). The most common acute brain injury found at autopsy was hypoxic-ischemic brain injury (58%) followed by intracranial hemorrhage (29%). The most common types of intracranial hemorrhage were intracerebral (17%), subarachnoid (17%), and subdural (8%). Only five infants (21%) did not have acute brain injury. Correlates of acute brain injury included low preextracorporeal membrane oxygenation oxygen saturation as well as elevated liver enzymes, total bilirubin, and lactate on days 1 and 3 of extracorporeal membrane oxygenation. Gestational age, Apgar scores, birth weight, extracorporeal membrane oxygenation duration, anticoagulation therapy, and renal and hepatic impairments were not associated with acute brain injury. CONCLUSIONS: Acute brain injury was observed in 79% of autopsies conducted in infants supported on extracorporeal membrane oxygenation. Hypoxic-ischemic brain injury was the most common type of brain injury (58%), and further associations with preextracorporeal membrane oxygenation acute brain injury require additional exploration.

Understanding Characteristics of Acute Brain Injury in Adult Extracorporeal Membrane Oxygenation: An Autopsy Study.

OBJECTIVES: Current studies lack information on characteristics of acute brain injury in patients with extracorporeal membrane oxygenation. We sought to characterize the types, timing, and risk factors of acute brain injury in extracorporeal membrane oxygenation. DESIGN: Retrospective analysis. SETTING: We reviewed the extracorporeal membrane oxygenation patients who had undergone brain autopsy with gross and microscopic examinations from January 2009 to December 2018 from a single tertiary center. PATIENTS: Twenty-five patients (median age 53 yr) had postmortem brain autopsy. INTERVENTIONS: Description and analysis of neuropathologic findings. MEASUREMENT AND MAIN RESULTS: Of 25, 22 had venoarterial extracorporeal membrane oxygenation (88%) (nine cardiac arrest; 13 cardiogenic shock) and three had venovenous extracorporeal membrane oxygenation cannulation (12%). The median extracorporeal membrane oxygenation support time was 96 hours (interquartile range, 26-181 hr). The most common acute brain injury was hypoxic-ischemic brain injury (44%), followed by intracranial hemorrhage (24%), and ischemic infarct (16%). Subarachnoid hemorrhage (20%) was the most common type of intracranial hemorrhage, followed by intracerebral hemorrhage (8%), and subdural hemorrhage (4%). Only eight patients (32%) were without acute brain injury after extracorporeal membrane oxygenation. The most common involved location for hypoxic-ischemic brain injury was cerebral cortices (82%) and cerebellum (55%). The pattern of ischemic infarct was territorial in cerebral cortices. The risk factors for acute brain injury included hypertension history (11 vs 1; p = 0.01), preextracorporeal membrane oxygenation antiplatelet use (7 vs 0; p = 0.03), and a higher day 1 lactate level (10.0 vs 5.1; p = 0.02). Patients with hypoxic-ischemic brain injury had more hypertension (8 vs 4; p = 0.047), a higher day 1 lactate level (12.6 vs 5.8; p = 0.02), and a lower pH level (7.09 vs 7.24; p = 0.027). Extracorporeal membrane oxygenation duration, cannulation methods, hemoglobin level, coma, renal impairment, and hepatic impairment were not associated with acute brain injury. CONCLUSIONS: In the population who underwent postmortem neuropathologic evaluation, 68% of extracorporeal membrane oxygenation nonsurvivors developed acute brain injury. Hypoxic-ischemic brain injury was the most common type of injury suggesting that patients sustained acute brain injury as a consequence of cardiogenic shock and cardiac arrest. Further research with a systematic neurologic monitoring is necessary to define the timing of acute brain injury in patients with extracorporeal membrane oxygenation.

Neuropathological findings in comatose patients with venoarterial extracorporeal membrane oxygenation.

We sought to describe the relation between neuropathology and clinical information including neurological examination and electroencephalogram findings in extracorporeal membrane oxygenation. We reviewed the patients who had undergone brain autopsy from November 2017 through December 2018. Four patients with neuromonitoring had post mortem examination with brain autopsy. The median age was 56, and all had venoarterial extracorporeal membrane oxygenation cannulation. There was no known acute neurologic injury prior to extracorporeal membrane oxygenation. While on extracorporeal membrane oxygenation, all were persistently comatose off sedation. Continuous encephalogram was done on all four, all of which showed delta frequency with absent reactivity. In Case 1, the pathological evaluation demonstrated small infarcts in cerebral cortices. In Case 2, it showed cortical microhemorrhages and chronic microinfarcts in basal ganglia. In Cases 3 and 4, the neuropathological assessment demonstrated diffuse hypoxic-ischemic brain injury. The clinical presentation was consistent with the widespread neuropathologic injury in two cases (Cases 3 and 4) but not in the other two (Cases 1 and 2). While "poor neurological status" was provided in the end-of-life discussion in all four, only two had significant brain injuries. There is limited understanding about brain injury in extracorporeal membrane oxygenation. Extrapolations related to prognostication from experience in other brain injury needs to be approached cautiously.

Cognitive impairments induced by necrotizing enterocolitis can be prevented by inhibiting microglial activation in mouse brain.

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease of the premature infant. One of the most important long-term complications observed in children who survive NEC early in life is the development of profound neurological impairments. However, the pathways leading to NEC-associated neurological impairments remain unknown, thus limiting the development of prevention strategies. We have recently shown that NEC development is dependent on the expression of the lipopolysaccharide receptor Toll-like receptor 4 (TLR4) on the intestinal epithelium, whose activation by bacteria in the newborn gut leads to mucosal inflammation. Here, we hypothesized that damage-induced production of TLR4 endogenous ligands in the intestine might lead to activation of microglial cells in the brain and promote cognitive impairments. We identified a gut-brain signaling axis in an NEC mouse model in which activation of intestinal TLR4 signaling led to release of high-mobility group box 1 in the intestine that, in turn, promoted microglial activation in the brain and neurological dysfunction. We further demonstrated that an orally administered dendrimer-based nanotherapeutic approach to targeting activated microglia could prevent NEC-associated neurological dysfunction in neonatal mice. These findings shed light on the molecular pathways leading to the development of NEC-associated brain injury, provide a rationale for early removal of diseased intestine in NEC, and indicate the potential of targeted therapies that protect the developing brain in the treatment of NEC in early childhood.

Challenges and Advances in Gene Therapy Approaches for Neurodegenerative Disorders.

INTRODUCTION: The recent approval of Spinraza (nusinersen), an antisense oligonucleotide, by U.S. Food and Drug Administration to treat patients with spinal muscular atrophy, has reignited interests of researchers in designing and testing new gene therapy approaches to treat neurological disorders, in particular, to curb neurodegenerative diseases of the central nervous system which represent an ever-increasing public health burden to today's society. CONCLUSION: This review highlights several key factors to be taken into consideration to design successful preclinical and clinical gene therapy experiments with respect to the vehicle of delivery and the route of administration to CNS-specific targets, with an additional focus on antisense oligonucleotide therapy and recent clinical trial developments.

A Novel Method to Model Chronic Traumatic Encephalopathy in Drosophila.

Chronic Traumatic Encephalopathy (CTE) is an established neurodegenerative disease that is closely associated with exposure to repetitive mild Traumatic Brain Injury (mTBI). The mechanisms responsible for its complex pathological changes remain largely elusive, despite a recent consensus to define the neuropathological criteria. Here, we describe a novel method to develop a model of CTE in Drosophila melanogaster (Drosophila ) in an attempt to identify the key genes and pathways that lead to the characteristic hyperphosphorylated tau accumulation and neuronal death in the brain. Adjustable-strength impacts to inflict mild closed injury are delivered directly to the fly head, subjecting the head to rapid acceleration and deceleration. Our method eliminates the potential problems inherent with other Drosophila mTBI models (e.g.,animal death might be induced by damage to other parts of the body or to internal organs). The less labor- and cost-intensive animal care, short life span, and extensive genetic tools make the fruit fly ideal to study CTE pathogenesis and make it possible to perform large-scale, genome-wide forward genetic and pharmacological screens. We anticipate that the ongoing characterization of the model will generate important mechanistic insights on disease prevention and therapeutic approaches.

Cryptic exon incorporation occurs in Alzheimer's brain lacking TDP-43 inclusion but exhibiting nuclear clearance of TDP-43.

Abnormal accumulation of TDP-43 into cytoplasmic or nuclear inclusions with accompanying nuclear clearance, a common pathology initially identified in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), has also been found in Alzheimer' disease (AD). TDP-43 serves as a splicing repressor of nonconserved cryptic exons and that such function is compromised in brains of ALS and FTD patients, suggesting that nuclear clearance of TDP-43 underlies its inability to repress cryptic exons. However, whether TDP-43 cytoplasmic aggregates are a prerequisite for the incorporation of cryptic exons is not known. Here, we assessed hippocampal tissues from 34 human postmortem brains including cases with confirmed diagnosis of AD neuropathologic changes along with age-matched controls. We found that cryptic exon incorporation occurred in all AD cases exhibiting TDP-43 pathology. Furthermore, incorporation of cryptic exons was observed in the hippocampus when TDP-43 inclusions was restricted only to the amygdala, the earliest stage of TDP-43 progression. Importantly, cryptic exon incorporation could be detected in AD brains lacking TDP-43 inclusion but exhibiting nuclear clearance of TDP-43. These data supports the notion that the functional consequence of nuclear depletion of TDP-43 as determined by cryptic exon incorporation likely occurs as an early event of TDP-43 proteinopathy and may have greater contribution to the pathogenesis of AD than currently appreciated. Early detection and effective repression of cryptic exons in AD patients may offer important diagnostic and therapeutic implications for this devastating illness of the elderly.