Maria L.V. Dizon

Doublecortin is necessary for the migration of adult subventricular zone cells from neurospheres

Mutations in human doublecortin (DCX) and knockdown of Dcx in rodents cause radial migration defects in the embryonic cerebral cortex. However, the brain phenotype of Dcx knockout mice is largely normal suggesting that Dcx is not necessary for most migration events. Adult subventricular zone (SVZ) cells migrate tangentially in the rostral migratory stream to the olfactory bulbs. Dcx is expressed in the SVZ but it is unknown if it is necessary for migration. We show that Dcx RNAi reduced SVZ cell migration in vitro, both cell autonomously and non-cell autonomously. Overexpression of Dcx rescued migration after knockdown, but did not increase migration by itself. Thus, Dcx is necessary not only for embryonic radial migration but also migration of adult SVZ cells.

Short-term outcomes after perinatal hypoxic ischemic encephalopathy: a report from the Children’s Hospitals Neonatal Consortium HIE focus group

Objective:To characterize infants affected with perinatal hypoxic ischemic encephalopathy (HIE) who were referred to regional neonatal intensive care units (NICUs) and their related short-term outcomes.Study Design:This is a descriptive study evaluating the data collected prospectively in the Children’s Hospital Neonatal Database, comprised of 27 regional NICUs within their associated children’s hospitals. A consecutive sample of 945 referred infants born ⩾36 weeks’ gestation with perinatal HIE in the first 3 days of life over approximately 3 years (2010–July 2013) were included. Maternal and infant characteristics are described. Short-term outcomes were evaluated including medical comorbidities, mortality and status of survivors at discharge.Result:High relative frequencies of maternal predisposing conditions, cesarean and operative vaginal deliveries were observed. Low Apgar scores, profound metabolic acidosis, extensive resuscitation in the delivery room, clinical and electroencephalographic (EEG) seizures, abnormal EEG background and brain imaging directly correlated with the severity of HIE. Therapeutic hypothermia was provided to 85% of infants, 15% of whom were classified as having mild HIE. Electrographic seizures were observed in 26% of the infants. Rates of complications and morbidities were similar to those reported in prior clinical trials and overall mortality was 15%.Conclusion:Within this large contemporary cohort of newborns with perinatal HIE, the application of therapeutic hypothermia and associated neurodiagnostic studies appear to have expanded relative to reported clinical trials. Although seizure incidence and mortality were lower compared with those reported in the trials, it is unclear whether this represented improved outcomes or therapeutic drift with the treatment of milder disease.

The bone morphogenetic protein antagonist noggin protects white matter after perinatal hypoxia-ischemia.

Hypoxia-ischemia (HI) in the neonate leads to white matter injury and subsequently cerebral palsy. We find that expression of bone morphogenetic protein 4 (BMP4) increases in the neonatal mouse brain after unilateral common carotid artery ligation followed by hypoxia. Since signaling by the BMP family of factors is a potent inhibitor of oligodendroglial differentiation, we tested the hypothesis that antagonism of BMP signaling would prevent loss of oligodendroglia (OL) and white matter in a mouse model of perinatal HI. Perinatal HI was induced in transgenic mice in which the BMP antagonist noggin is overexpressed during oligodendrogenesis (pNSE-Noggin). Following perinatal HI, pNSE-Noggin mice had more oligodendroglial progenitor cells (OPCs) and more mature OL compared to wild type (WT) animals. The increase in OPC numbers did not result from proliferation but rather from increased differentiation from precursor cells. Immunofluorescence studies showed preservation of white matter in lesioned pNSE-Noggin mice compared to lesioned WT animals. Further, following perinatal HI, the pNSE-Noggin mice were protected from gait deficits. Together these findings indicate that the BMP-inhibitor noggin protects from HI-induced loss of oligodendroglial lineage cells and white matter as well as loss of motor function.

Hypoxia-Ischemia Induces an Endogenous Reparative Response by Local Neural Progenitors in the Postnatal Mouse Telencephalon

Perinatal hypoxia-ischemia in the preterm neonate commonly results in white matter injury for which there is no specific therapy. The subventricular zone (SVZ) of the brain harbors neural stem cells and more committed progenitors including oligodendroglial progenitor cells that might serve as replacement cells for treating white matter injury. Data from rodent models suggest limited replacement of mature oligodendroglia by endogenous cells. Rare newly born mature oligodendrocytes have been reported within the striatum, corpus callosum and infarcted cortex 1 month following hypoxia-ischemia. Whether these oligodendrocytes arise in situ or emigrate from the SVZ is unknown. We used a postnatal day 9 mouse model of hypoxia-ischemia, BrdU labeling of mitotic cells, immunofluorescence and time-lapse multiphoton microscopy to determine whether hypoxia-ischemia increases production of oligodendroglial progenitors within the SVZ with emigration toward injured areas. Although cells of the oligodendroglial lineage increased in the brain ipsilateral to hypoxic-ischemic injury, they did not originate from the SVZ but rather arose within the striatum and cortex. Furthermore, they resulted from proliferation within the striatum but not within the cortex. Thus, an endogenous regenerative oligodendroglial response to postnatal hypoxia-ischemia occurs locally, with minimal long-distance contribution by cells of the SVZ.

Subventricular zone cells remain stable in vitro after brain injury.

Subventricular zone (SVZ) cells emigrate toward brain injury but relatively few survive. Thus, if they are to be used for repair, ex vivo expansion and autologous transplantation of SVZ cells may be necessary. Since it is unclear how brain injury alters SVZ cell culture, we studied neurosphere formation, differentiation, and migration, after cortical lesions. The number of neurosphere forming cells from lesioned mice was comparable to controls. Also, the proportion of astrocytes and neurons generated in vitro remained unchanged after cortical lesions. Cell emigration from neurospheres was characterized by increased cell-cell contact after injury in adults and neonates. However, neither molecules implicated in SVZ migration nor the extent of migration changed after injury. Thus, neurospheres can be successfully cultured after extensive brain damage, and they are remarkably stable in vitro, suggesting suitability for ex vivo expansion and autologous transplantation.

Traumatic brain injury activation of the adult subventricular zone neurogenic niche

Traumatic brain injury (TBI) is common in both civilian and military life, placing a large burden on survivors and society. However, with the recognition of neural stem cells in adult mammals, including humans, came the possibility to harness these cells for repair of damaged brain, whereas previously this was thought to be impossible. In this review, we focus on the rodent adult subventricular zone (SVZ), an important neurogenic niche within the mature brain in which neural stem cells continue to reside. We review how the SVZ is perturbed following various animal TBI models with regards to cell proliferation, emigration, survival, and differentiation, and we review specific molecules involved in these processes. Together, this information suggests next steps in attempting to translate knowledge from TBI animal models into human therapies for TBI.

MicroRNAs participate in the murine oligodendroglial response to perinatal hypoxia-ischemia

Background:Hypoxic–ischemic injury (HI) to preterm brain results in white matter loss. The endogenous oligodendroglial response to perinatal HI is characterized by increased oligodendroglial progenitor cells (OPCs). MicroRNAs (miRs) are important post-transcriptional regulators of gene expression, and a few miRs have been shown to regulate differentiation of OPCs into mature oligodendroglia. We tested the hypothesis that miRs play a role in the increase in OPCs in response to perinatal HI.Methods:We inducibly deleted the miR-processing enzyme Dicer in OPCs using a tamoxifen-inducible NG2CreERT2 transgene in Dicerfl/fl mice. After HI, mice were analyzed for OPC differentiation using immunofluorescence and for white matter formation by Luxol fast blue (LFB) staining. Functional recovery from injury was investigated using digital gait analysis. We also tested whether HI changed miRs known to regulate OPC differentiation using quantitative RT-PCR.Results:Perinatal HI induced significant increases in miR-138 and miR-338, two miRs known to regulate OPC differentiation. Knockdown of Dicer increased myelin basic protein and LFB staining within the corpus callosum after HI. In addition, there was significant improvement in motor function 14 and 24 d post lesion.Conclusion:Changes in specific mature miRs expressed in OPCs following HI may contribute to white matter injury.

The Subventricular Zone Responds Dynamically to Mechanical Brain Injuries

Brain injury is a common yet relatively untreatable problem (Thurman, 1999). Of the 500,000 cases of traumatic brain injury annually in the United States, greater than 90,000 result in disability (Valadka, 2000). Mechanical injuries often occur to external regions of the brain: the cerebral cortex and other parts of the telencephalon. They can produce a wide variety of longterm and devastating symptoms and pathologies due to neuronal death. The underlying biological predicament in recovery from brain injury is that the adult central nervous system is generally incapable of replacing dead neurons. This concept has been challenged by the discovery of neurogenic adult stem cells in the subventricular zone (SVZ) (Alvarez-Buylla et al., 2000). It has been estimated that the SVZ replaces tens of thousands of olfactory bulb (OB) interneurons per day in rodents. Behavioral studies suggest that the constant turnover of OB neurons allows olfactory discrimination (Gheusi et al., 2000). Adult humans and other primates have also been shown to possess neurogenic SVZ cells with many of the features delineated in rodents (Eriksson et al., 1998; Bernier et al., 2000; Weickert et al., 2000; Kornack and Rakic, 2001; Pencea et al., 2001b). Granted, the sense of smell is not of vital importance for humans, unless one is a sommelier. Yet, since the SVZ is in close proximity to the cerebral cortex and other functionally important forebrain nuclei, hope has risen that the great neurogenic and migratory potential of adult stem cells may be co-opted for repair. This optimism is bolstered by the fact that adult SVZ cells are descendants of the proliferative neuroepithelia which, during development, give rise to the myriad neural cells in the telencephalon.

Intercenter Cost Variation for Perinatal Hypoxic-Ischemic Encephalopathy in the Era of Therapeutic Hypothermia.

OBJECTIVE To quantify intercenter cost variation for perinatal hypoxic ischemic encephalopathy (HIE) treated with therapeutic hypothermia across childrens hospitals. STUDY DESIGN Prospectively collected data from the Childrens Hospitals Neonatal Database and Pediatric Health Information Systems were linked to evaluate intercenter cost variation in total hospitalization costs after adjusting for HIE severity, mortality, length of stay, use of extracorporeal support or nitric oxide, and ventilator days. Secondarily, costs for intensive care unit bed, electroencephalography (EEG), and laboratory and neuroimaging testing were also evaluated. Costs were contextualized by frequency of favorable (survival with normal magnetic resonance imaging) and adverse (death or need for gastric tube feedings at discharge) outcomes to identify centers with relative low costs and favorable outcomes. RESULTS Of the 822 infants with HIE treated with therapeutic hypothermia at 19 regional neonatal intensive care units, 704 (86%) survived to discharge. The median cost/case for survivors was

Sustaining careers of physician-scientists in neonatology and pediatric critical care medicine: formulating supportive departmental policies

58 552 (IQR