Patrick McQuillen, M.D. - US grants

DESCRIPTION: (Adapted from the candidate's description) The overall goal of this application is to elucidate mechanisms making the developing brain uniquely vulnerable to hypoxic ischemic injury. The application is based on the premise that a detailed understanding of normal cortical development may help to determine why different patterns of injury occur at each stage of development. Development of the visual system is used as a model of cortical development. The proposed studies examine the identity of cells injured during development. Then, focusing on a specific population of cells - subplate neurons, the molecular mechanisms mediating early hypoxic ischemic brain injury will be investigated. The primary hypothesis is that subplate neurons are particularly vulnerable to early hypoxic ischemic brain injury. The secondary hypothesis is that mechanisms governing normal subplate neuron cell death contribute to its sensitivity to hypoxic ischemic and excitotoxic cell death. Three specific aims are proposed: 1) To characterize the identity, topography, and time course of dying cells following early hypoxic ischemic brain injury, and to correlate these observations with alterations in normal cortical development; 2) To determine the relationship of subplate neuron cell death to the expression and regulation of receptors for glutamate and neurotrophins; and 3) To identify genes differentially expressed by subplate neurons normally and following hypoxia ischemia brain injury.

[unreadable] DESCRIPTION (provided by applicant): Hypoxia-ischemia damages the brain in a developmental stage-specific and region selective manner. Evidence suggests that selective cellular vulnerability contributes to differing patterns of age-related hypoxicic schemic injury. In a rodent model of human periventricular white matter injury, we determined that early hypoxia-ischemia leads to the selective cell death of sub-plate neurons, a cell population unique to the developing brain. Sub-plate neurons are required for activity-dependent formation, refinement and maturation of patterned thalamocortical connections, and may play a role in the unique capacity of the neonatal brain for plasticity during defined critical periods. We have developed a method for purifying sub-plate neurons, representing the first lamina-specific cortical neuronal cultures and have reported the factors that promote sub-plate neuron survival including a novel p75NTR dependent ceramide signaling pathway. Consistent with their selective vulnerability in vivo, cultured sub-plate neurons are more sensitive to oxygen-glucose deprivation than age matched mixed cortical neuronal cultures. Our objectives in this proposal are 1) to determine the significance of selective sub-plate neuron death for subsequent cortical plasticity and 2) utilize purified sub-plate neurons to determine the mechanism of selective sub-plate neuron vulnerability. We hypothesize that selective sub-plate neuron death following early hypoxia-ischemia impairs activity-dependent cortical plasticity. We will quantify activity dependent cortical plasticity following early hypoxia-ischemia and interventions that prevent sub-plate neuron cell death. We hypothesize further that sub-plate neuron selective vulnerability results from altered neurotrophin-mediated p75NTR-dependent signaling and we will investigate this with immunopurified cultures of sub-plate neurons exposed to oxygen glucose deprivation. Finally, we hypothesize that treatments that protect sub-plate neurons in vitro will also prevent sub-plate neuron cell death following early hypoxia ischemia. [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): The overall goal of this project is to understand the impact of early brain injury on subsequent brain plasticity. A common perception is that recovery from neonatal brain injury is augmented by plasticity of the immature brain. Yet often injury results in permanent neurologic deficits, highlighting the need for more detailed understanding of plasticity following injury. This proposal focuses on the most well studied model of cortical plasticity -- ocular dominance in the visual system of binocular mammals. Ocular dominance plasticity (ODP) refers to the change in strength of eye-specific inputs following monocular deprivation. A closely related condition in humans is known as amblyopia. An advantage of the model is recent progress identifying the factors controlling critical period timing, including maturation of cortical inhibitory circuits and myelination. The project uses a translational small animal (rat and mouse) model of very early hypoxic-ischemic brain injury. Using this model, we find that ODP is impaired. Visual cortical development is grossly normal in all but the most severely injured animals. Yet, impaired ODP is not an isolated finding, as plasticity in somatosensory cortex is also diminished. In this model, we have reported the selective vulnerability of subplate neurons, a transient population of neocortical neurons important for visual thalamocortical development. It is unclear why early subplate neuron death would restrict subsequent plasticity. However, early activity is transmitted into neocortex through transient circuits involving subplate neurons. Our hypothesis is that diminished cortical excitation, resulting from loss of subplate neurons, disrupts activity-dependent maturation and refinement of cortical circuits. Consistent with this idea, we find diminished and altered expression of cortical inhibitory neuronal markers following injury. With the development of this model, we are now positioned to investigate the role of specific plasticity mechanisms in recovery from neonatal brain injury. To accomplish this, our specific aims are: (1) determine the mechanism of altered inhibition following early HI and its relationship to impaired ODP and (2) measure the effect of disrupted myelination on ODP following early HI. ODP is quantified with intrinsic signal optical imaging. Inhibitory circuits and myelination are studied with histology, immunofluorescence and protein biochemistry. We will attempt to restore plasticity by specifically overcoming identified defects in cortical inhibition and myelination by pharmacologic or growth factor treatment, grafting of precursor cells, function blocking antibodies or the use of existing genetically modified mouse models. These experiments will offer fundamental insight into the normal role of subplate neurons in the maturation of cortical circuits and ODP. Understanding impaired plasticity will provide both a novel functional outcome measure and a model to guide strategies for regenerating functional cortical connections following brain injury. PUBLIC HEALTH RELEVANCE: Brain injury in the newborn is a common problem following difficult or premature birth and in babies with congenital heart disease. The overall goal of this project is to understand the impact of newborn brain injury on subsequent brain plasticity, the ability of the brain to change by forming and modifying connections between neurons. Understanding plasticity following injury will provide both a new outcome measure and a model to guide therapy for recovering brain function. [unreadable] [unreadable] [unreadable] [unreadable]

The overall goal of this project is to use a multidisciplinary approach and advanced magnetic resonance imaging (MRI) to understand mechanisms that result in neurodevelopmental impairment in critically ill newborns with congenital heart disease (CHD). Data from our group and others have shown that injury to the developing brain white matter is common in newborns with CHD. The appearance of this white matter injury is identical to that seen in premature infants, with injuries identified before and after neonatal surgery. We are focusing this study on two of the most common forms of congenital heart disease: transposition of the great arteries (TGA) and single ventricle physiology (SVP), because both conditions are associated with abnormal fetal cerebral blood flow and postnatal ductal dependent circulation. We have recently determined that maturation of cerebral microstructure and metabolism are delayed in these newborns, prior to surgery, possibly as a result of impaired in utero brain development. In this proposal we will test that hypothesis that delayed in utero brain development predisposes newborns with CHD to white matter injury in response to perioperative insults. We have developed essential methods to safely measure brain development, injury and perioperative oxygen delivery in fetuses and newborns with CHD. Using these tools, we are positioned to address our overall objective of determining if delayed in utero brain development underlies the specific vulnerability of term newborns with CHD to white matter injury. To do this, we propose two specific aims: (1) To characterize brain development and injury in utero and postnatally, before and after cardiac surgery, in term newborns with TGA and SVP. (2) To determine if the risk of white matter injury is related to impaired brain oxygen delivery (proximate cause), in the setting of delayed brain microstructural and metabolic development. This multidisciplinary project combines the expertise of pediatric critical care, neurology, neuroradiology, cardiology and cardiothoracic surgery to identify specific pathophysiologic mechanisms of brain injury and develop novel prognostic measures of neurodevelopmental outcome that can be translated into future neuroprotective trials. Page McQuillen, Patrick S.

Project Summary (Core C) The overall objective of the core is to facilitate efficient preparation, distribution and analysis of ferret brain tissue among Projects 1-3 for studies of normal development and development following early hypoxic brain injury. The Ferret model has distinct advantages over existing rodent models for studies central to this program project focused on novel late migratory streams (Project 1), oligodendrocyte precursor cell development (Project 2) and hypoxia/HIF pathway signaling (Project 3). These advantages include: (1) a gyrencephalic brain with a protracted period of postnatal brain development and (2) the existence of a distinct outer subventricular zone and late migrating neuronal streams similar to human MMS and DMS. Core C will promote synergy and interaction among the three projects by facilitating integrated Ferret tissue utilization. We propose the following two specific objectives: Objective 1: Optimal preparation and utilization of brain tissue from a unique small animal, gyrencephalic model of normal cortical development in the ferret (Mustela putorius) Objective 2: Further develop a small animal model of human preterm white matter injury in the gyrencephalic ferret suitable for translational studies of pathogenesis and therapy. Unlike rodents, Ferrets are an FDA regulated species. The core will be responsible for developing and maintaining appropriate protocols for the compassionate care and use of Ferrets. All protocols will be developed in consultation with University of California, San Francisco Laboratory Animal Resource Center (LARC) veterinarians. The Core will maintain annual regulatory approval through the UCSF Institutional Animal Care and Use Committee (IUCUC). The Core will carry out all animal surgeries and postsurgical care along with LARC veterinarians. A major function of the core will be to organize efficient use of animal tissue by optimizing sharing of tissue among compatible projects. The Program Project Administrative Committee will determine allocation and prioritization of animals and tissue. The core will be responsible for developing and testing reagents and techniques for tissue analysis. Finally the core will develop conditions for the chronic hypoxia translational model of newborn brain injury. This will include Ferret brain MR imaging, an application with potential for increasing translational relevance by comparison with complementary human data.

Project II - Repair in High Risk Newborns with Congenital Heart Disease Congenital heart disease (CHD) is the most common birth defect, and neonatal surgery is often necessary for survival. Despite the complexity of these surgeries, most infants with CHD survive. Although severe neurologic disability is rare, school age children with CHD frequently exhibit behavioral, emotional, cognitive and motor impairments. The pervasive nature of these disabilities suggests fundamental problems with brain development. Using advanced magnetic resonance imaging techniques, we have discovered that newborns with CHD have delayed brain development compared with normal babies and are at high risk of acquiring new brain injuries before and after surgery. The overall goal of this proposal is to understand neurodevelopmental impairment following neonatal CHD surgery at a structural brain network level and to determine the capacity for repair following neonatal brain injury. To achieve this goal, this study will use new techniques for analyzing the complete set of brain connections - the so-called 'connectome'. Newborns with two types of CHD will be studied before and after surgery and again at six months of age. The groups differ in the number of surgeries needed to restore heart function and blood oxygen levels to near normal levels. By performing MRIs at three time points, we will learn how development of brain networks are affected in CHD and how repair and recovery from brain injury proceeds following neonatal surgery. This information will be useful for developing new treatments to optimize brain development and recovery from brain injury in any condition where newborn brain injury occurs because of low brain oxygen and/or blood flow.

? DESCRIPTION (provided by applicant): The NICHD Collaborative Pediatric Critical Care Research Network (CPCCRN, UG1) was established in 2004 to address the following: (1) increased utilization of costly and complex pediatric critical care services and (2) lack of prospective clinical trials in pediatric critical care compared with adult and neonatal populations The primary Aim of this application is to join the CPCCRN as a clinical site, in order to expand our single center prospective observational cohort of pediatric patients with Acute Respiratory Distress Syndrome (ARDS) through enrollment at multiple CPCCRN Sites. ARDS is a common cause of pediatric critical illness (30% of PICU mortalities). We propose to enroll 800 pediatric patients with ARDS and collect clinical data with plasma and genetic biomarkers of coagulation and inflammation. The data obtained will be essential for stratifying prospective clinical research trials and will provide insight into basic molecular and cellular disease mechanisms necessary for designing new treatments. UCSF Medical Center and Benioff Children's Hospital, the Department of Pediatrics and Division of Pediatric Critical Care Medicine have a long history of participation in ground breaking multicenter clinical research, as well as cutting edge individual investigator driven basic, translational and clinical research. This tradition, coupled with deep institutional resources for biomedical research, makes our center ideally positioned to contribute novel proposals to the consortium and participate fully in network-sponsored studies

DESCRIPTION (provided by applicant): This grant proposes to study both structural and functional correlates of brain developmental maturation and network organization using advanced imaging techniques in our human populations and similar correlates in newborn rodents with a focus on defining basic mechanisms of repair. The grant will encompass three projects and two cores: Project I) repair after ischemic injury in the term newborn - using both structural and metabolic serial imaging to evaluate how the injuries have altered the brain, its response to injury in the perinatal period, and how structural connectivity relates to neurodevelopmental outcome. This cohort will include babies treated with hypothermia. Project II) repair in high risk newborns with congenital heart disease- there is delayed brain development in this high risk population. Using structural and metabolic imaging, we will determine whether this disorder of development is associated with abnormalities in brain connectivity and functional outcome. Project III) repair after early preterm birth - our data show many preterm infants to have abnormalities of cerebellar maturation, abnormalities of white matter development or progressive white matter disease with infection. Using structural and metabolic imaging, we will determine whether altered patterns of connectivity are consistent or variable, whether recovery from these insults is possible and whether connectivity is permanently or transiently disrupted by these early ex-utero life events. There is an administrative Core for data management including biostatistical support, budgetary oversight, training and seminars. The Imaging and Neurobehavior Core (Services Core) will support the three human imaging projects by ensuring standardization of methods and tracking of imaging acquisition at the various testing time points. In addition, this Core will provide Neurobehavioral testing at all of the follow-up visits, and will be responsible for tracking patients for all projets.