Quick Project Snapshot

Exploring the therapeutic potential of progranulin for the treatment of stroke

Background: Progranulin is a secreted protein that was recently shown to be important in protecting the brain from atrophy associated with frontotemporal dementia. Our previous research focussed on progranulin in stroke.  We demonstrated that progranulin-deficient mice have a worse outcome after stroke, revealing an important and previously unrecognised role of progranulin in the ischaemic brain (Jackman et al., J Neurosci (2013) 33:19579).  We demonstrated that the structure of the blood brain barrier (BBB) was altered in progranulin-deficient mice.  Specifically, the overlap of endothelial cells - which forms the primary site of the BBB - was shorter and less complex (Figure 1). 

Figure 1. Images of endothelial tight junctions in wild-type (WT) and progranulin deficient (PGRN-KO) mice obtained using transmission electron microscopy.  

This caused the BBB to become ‘leaky’ in progranulin-deficient mice and thereby increase injury after stroke.  These findings, combined with evidence that progranulin is down-regulated in the brain after stroke and our preliminary data that progranulin can rapidly decrease BBB permeability in vitro (see accompanying project), suggests that increasing levels of progranulin could represent an effective treatment for stroke.  As we are yet to define the mechanism by which progranulin promotes barrier integrity, the second component of this study will be to explore the mechanism of these BBB stabilising effects, with particular focus on select proteins such as VE-cadherin, β-catenin and their association with the actin cytoskeleton.  

Aims: The aim of this study is to establish if progranulin treatment at clinically relevant time points after stroke can attenuate BBB permeability and improve post-stroke outcome.  In addition, the contribution of VE-cadherin, β-catenin and their association with the cytoskeleton will be evaluated.  

Method & Plan:  Mice will be subjected to transient cerebral ischemia using the intraluminal filament model of middle cerebral artery occlusion (MCAO) (Jackman et al., Meth Mol Biol (2011) 793:195).  Mice will be treated with progranulin (100 ng, intravenous) from between 0 – 24 hrs post stroke.  Three days (72hrs) after stroke motor impairment will be evaluated in mice using behavioural testing, including the Bederson score, wire-hanging and corner test.  

The degree of brain injury will then be assessed by quantifying swelling in the brain, using the wet-dry technique and infarct volume, with cresyl violet staining.  In order to explore the mechanism of these effects, additional mice will be subjected to stroke and sacrificed within 1 hr of progranulin treatment (allowing us to establish a causative role) to evaluate BBB integrity by quantifying leakage of fluorescent dyes (Evans blue, FITC-dextran) into the brain using confocal microscopy.  In addition, the expression of key BBB proteins, in particular VE-cadherin and β-catenin, will be assessed using Western blot, confocal microscopy & immune-electron microscopy. 

Expected outcomes: We hypothesise that treatment with progranulin will rapidly attenuate ischaemic brain injury by attenuating BBB permeability.  Furthermore, we predict that the ability of progranulin to promote BBB integrity will relate to its ability to preserve expression and endothelial cleft localisation of VE-cadherin, in addition to promoting its interaction with the actin cytoskeleton via β-catenin.  The ability of progranulin treatment to effectively reduce brain injury at extended time points after stroke will greatly increase the therapeutic potential of this agent.

 

Jackman et al., J Neurosci (2013) 33:19579) Jackman et al., Meth Mol Biol (2011) 793:195

Clinical Cognitive Neuroscience Laboratory

In the Clinical Cognitive Neuroscience Laboratory, we study network degeneration following brain injury (e.g., ischaemic stroke) and have a particular interest in vascular contributions to cognitive impairment both in aging and in a range of neurodegenerative diseases, such as Alzheimer’s disease (AD). The latter is the most common cause of dementia in the western world and is associated with profound impairments in cognition and activities of daily living. Our research seeks to investigate neuroimaging correlates of cognitive decline; the effects of post-stroke exercise interventions on brain volume and cognitive function; and the accuracy and accessibility of imaging modalities in the diagnosis of dementia.  The ultimate goal of our research is to increase our understanding of two of the major causes of death, disability, and reduced quality of life in our society: dementia and stroke. Our team is headed by Associate Professor Amy Brodtmann, stroke and cognitive neurologist, Director of the Eastern Cognitive Disorders Clinic, and Heart Foundation Research Fellow.

We are collaborating with dementia and stroke researchers, clinicians, and neuroscientists, in Australia, and overseas, including Professor Martin Dichgans and Dr Marco During of the DEMDAS study in Munich Germany, Professor Charles DeCarli at the University of California Davis in the US, and Professor Vladimir Hachinski at the University of Western Ontario, Canada. These researchers are experts in their respective fields.

Our primary interest is to understand whether stroke and ischaemic brain injury cause neurodegeneration. This is currently being investigated in one of our major research projects, the NHMRC-funded, Cognition and Neocortical Volume After Stroke (CANVAS) Study, which is now in its fifth year of data collection.  In this study, stroke participants undergo an MRI scan and cognitive assessment within a few weeks of their events, and again, 3 months, 1 year, 3 years, and 5 years later. By comparing their results with a healthy, age-matched control group with no history of stroke or dementia, we can determine whether brain volume change is associated with post-stroke dementia and elucidate potential causal mechanisms, including genetic markers, amyloid deposition and vascular risk factors.

Another interest of our lab is to examine the association between exercise and rates of brain volume loss and cognitive decline after stroke.  In the Post Ischaemic Stroke Cardiovascular Exercise Study (PISCES), we seek to determine whether aerobic exercise after stroke is associated with preservation of brain volume and function, cognition, and greater physical and psychological well-being. One of the most important elements of this research study is its translatable novelty – our data will contribute to an applicable intervention-based approach.

All Projects by this Lab

Network disruptions following brain infarction: cognition, behaviour and regional brain volume changeExploring the therapeutic potential of progranulin for the treatment of strokeIs stroke neurodegenerative? A longitudinal study of changes in brain volume and cognition after stroke (CANVAS: Cognition And Neocortical Volume After Stroke)Evaluating Imaging Methods in Dementia (TIMID)Motor Speech Disorders in Degenerative Brain DiseaseBereavement and Grief in Neurodegenerative Disease (BAGINS)Post Ischaemic Stroke Cardiovascular Exercise Study (PISCES)

Behavioural Neuroscience

The Division of Behavioural Neuroscience focuses on the use and development of models that reflect aspects of human disorders such as addiction, anxiety, depression, schizophrenia, autism and neurodegenerative conditions such as Huntington’s disease. The Cognitive Neuroscience group additionally studies cognitive disorders caused by diseases such as stroke (cerebrovascular disease), Alzheimer's disease and other dementias from a clinical perspective.

All Labs that operate in this Division

Addiction Neuroscience LaboratoryClinical Cognitive Neuroscience LaboratoryDevelopmental Psychobiology LaboratoryEpigenetics and Neural Plasticity LaboratoryGenes Environment and Behaviour LaboratoryInhalant Addiction LaboratoryMidbrain Dopamine Plasticity LaboratorySynapse Biology and Cognition LaboratoryVascular Neurodegeneration Research Laboratory