Robert E. Gross - US grants

DESCRIPTION (provided by applicant): We are interested in developing strategies for the reconstitution of the dopaminergic (DA) nigrostriatal (NS) pathway that degenerates in Parkinson's disease, an important goal because of the inadequacy of current long-term treatments. Attempts to reconstruct this pathway through transplantation of precursor cells or neurons into the nigra of the adult fail, likely as a result of 1) the presence of inhibitory molecules and/or 2) the absence of trophic and guidance molecules in the adult CNS. Here we propose that an understanding of the molecular events that regulate the development of the nigrostriatal pathway will provide insights for strategies designed to improve NS pathway regeneration in the adult milieu. We propose - and have exciting preliminary data to support - that axon guidance molecules (AGMs), important molecules that direct the development of other projection pathways in the CNS, are expressed in the developing DA NS pathway. A series of experiments are proposed to elucidate the role played by AGMs and their receptors in the development of the NS pathway. Our specific aims are to: 1) Define those AGMs whose receptors are expressed in the developing axons of nigral DA neurons;2) Define the expression of AGM ligands in relation to the developing NS pathway;3) For those AGMs that are expressed in an appropriate anatomical relationship to influence NS development, and whose receptors are expressed in developing DA neurons, directly demonstrate chemotropic effects on fetal nigral DA neurons in vitro, and their importance in the development of the NS pathway with blocking studies ex vivo. The outcome of the experiments outlined in this proposal will hopefully be the refinement of means to counteract the inhibitory milieu of the adult injured nervous system, and recapitulate the attractive and repulsive factors that direct axonal outgrowth during development, thereby paving the way for novel reconstructive and regenerative strategies to ameliorate the symptoms of Parkinson's disease. The insights derived from these studies may also have applicability in other neurodegenerative diseases, brain injury and stroke. The research outlined is part of a customized five-year plan of training and career development for the Principal Investigator. The proposal includes active mentoring by experienced scientists, access to diverse resources, and an environment uniquely suited to help the PI develop as an independent neurosurgeon-neuroscientist.

DESCRIPTION (provided by applicants): Abstract Uncontrolled epileptic seizures plague more than one million Americans, despite the best medical and surgical treatments available. Novel therapies are desperately needed. We have formed a productive collaboration between a biomedical engineer and a translational clinician-scientist to pioneer a novel approach to suppressing generation of seizures using direct closed-loop multielectrode microstimulation of the epileptic focus. The method is based on our exciting in vitro work in which epileptiform activity in neuronal cultures was completely blocked by low voltage, low frequency microstimulation, distributed across multiple electrodes. The goal of the present project is to translate these results in vivo. We have manufactured a novel custom-designed system to simultaneously stimulate and record from chronically implanted microelectrodes in a closed-loop feedback fashion. We will optimize the parameters and materials to effectively maintain the firing rate of neurons in the epileptic focus in a range from which bursts of action potential - which underlie epileptic seizures - are prevented from occurring. Our success will be measured by demonstrating modulation of electrographic (EEG) and behavioral seizure activity in our rat model of focal onset seizures. If successful, this work will lead to a new treatment for patients disabled by intractable focal onset seizures. PUBLIC HEALTH RELEVANCE: To treat intractable focal-onset epileptic seizures, we propose a novel approach in which electrical stimulation - continuously delivered to the epileptic focus through arrays of microelectrodes - is tuned to maintain neural activity in a range from which epileptic seizures cannot arise. In this approach, which is based on our ability to completely suppress epileptiform bursts of action potentials in a cell culture model, state-control methodology prevents seizures from arising, rather than attempting to abort seizures after they arise. This translational research in a rodent focal epilepsy model hopefully will lead to a much needed novel treatment for patients with disabling, intractable focal-onset seizures.

DESCRIPTION (provided by applicant): Approximately 20-40% of patients with epilepsy have refractory seizures unresponsive to pharmacotherapy. There is therefore a need to develop alternative treatments for this large population of people who are at higher risk of developing epilepsy-related disabilities. Optogenetics - which provides a powerful approach to excite and/or inhibit neural activity in a cell-type specific manner - possesses great potential to limit or abolish the spread of the pathological neural activity underlying epileptic seizures. Despite this therapeutic potential, the use of optogenetics faces many technical challenges that limit its usefulness and translatability to the clinical setting. In this proposal, we present a hihly innovative solution to these problems by combining the use of optogenetics with bioluminescent reporters. Calcium-sensitive luciferases are a kind of bioluminescent reporter that has been successfully used for imaging neural activity in vivo. These luciferases respond to depolarization-associated calcium influx by emitting light that is compatible with the absorption spectrum of various inhibitory light-sensitive ion channels. We propose to use these reporters to create what we term an autonomous biologic controller capable of driving optogenetic feedback to control pathological activity. In our proposed model, calcium-sensitive luciferases would report neural activity in the form of light, inhibitory opsins would be activated by the emitted liht, and propagation of activity would be inhibited as the cell is hyperpolarized by the opsin. This autonomous, biological feedback of epileptic activity provides a novel solution to the technical limitations of optogenetics by eliminating the need for an external light source and offering a means for autonomous closed-loop feedback control. We suggest that this research is highly innovative and has the potential of accelerating the use of optogenetics as a tool to develop new therapies for epilepsy.

DESCRIPTION (provided by applicant): The Emory MSTP prepares highly gifted and motivated students to pursue careers as physician-scientists and leaders in biomedical research. The seven to eight year training process leads to both M.D. and Ph.D. degrees. The M.D./ Ph.D. Executive Committee, comprised of institutional leadership representing the many academic units involved in training, is responsible for oversight of the program. Selection of applicants is highly competitive and is made by the M.D./ Ph.D. Admissions Committee after extensive evaluation of prior scholarship and research experience, review of letters of recommendation, and in-depth interviews to assess motivation and determine the potential for success as physicians-scientists. The program allows for flexibility in program affiliation, as wel as the sequence and duration of clinical or research training, but most trainees pursue the following course of study. Students engage in laboratory research in the summer prior to the first year of Medical School. Following the Foundations phase of Medical School, each trainee begins his/her graduate training in advanced study. Trainees pursue dissertation research in a variety of outstanding graduate programs, including any of eight interdisciplinary training programs in the Emory Graduate School Division of Biological and Biomedical Sciences, in the Biomedical Engineering Program offered by the unique combined Department of Biomedical Engineering of Georgia Tech/Emory, in new programs in Biostatistics and Epidemiology offered by the Emory Rollins School of Public Health, or in one of several other scientific disciplines offered by the Graduate School of Arts and Sciences. Each trainee completes at least 14 months of clinical training after defending his/her thesis. The dramatic expansion of the research and clinical infrastructure at Emory and increased institutional support has facilitated the successful growth and development of the MSTP.

DESCRIPTION (provided by applicant): Stroke remains a leading cause of human death and disability while very few effective treatments are available for stroke patients. Stem cell transplantation therapy provides the possibility to regenerate and repair damaged brain tissues after ischemic stroke. The investigation takes a comprehensive and unprecedented approach to promote both trophic supports as well as cell replacement potential of pluripotent stem cells to develop a highly effective stem cell therapy for ischemic stroke. We propose that enhancing the survival and regenerative properties of transplanted cells as well as an improved host environment are critical for a successful stem cell stroke therapy. To reach this goal, our previous and preliminary studies have demonstrated a marked protective effect and increased functional benefits of combining hypoxia preconditioning (HP) and other regenerative strategies including optogenetic techniques and up regulated multiple trophic factors in the ischemic brain promoted by peripheral stimulation. Our central hypothesis is that a combination strategy of HP-primed NPCs subjected to optogenetic manipulations and improved host environment will allow better survival of transplanted as well as endogenous cells, enhance neurogenesis/angiogenesis via both exogenous and endogenous mechanisms, and results in optimal tissue repair and functional recovery after stroke. In neural progenitor cells (NPCs) derived from mouse induced pluripotent stem (iPS) cells, we will express the blue light- sensitive channelrhodopsin (ChR) channels and test the possibility that activation of ChRs by blue light stimuli or by the luciferase/ChR proten (luminopsis) substrate coelenterazine (CTZ) is a feasible and effective method to improve and evaluate neuronal differentiation, integration into host neural networks and neuronal connections after transplantation into the ischemic brain. We will examine the strategies to promote tissue repair and provide evidence for the morphological and functional restoration of ischemic brain structures in the unique barrel cortex ischemic stroke model of mice. We will demonstrate the feasibility and benefits of expression/activation of ChR channels in iPS-NPCs in vitro (Specific Aim 1) and after implantation into the post-ischemic barrel cortex (Aim 2). Based on the well-defined whisker- thalamus-barrel cortex pathway, structural and functional restoration of disrupted whisker-barrel activities will be evaluated usin a combination of cell specific and neuronal pathway specific measurements, including optogenetic, electrophysiological and optical imaging recordings (Aim 3). The proposal is from three research laboratories with complementary expertise in biophysics, electrophysiology, cellular/molecular biology and clinical neurosciences. The demonstration of cellular and tissue repairing benefits of iPS-NPCs in a particular brain structure is critical for the development of mechanism based cell transplantation therapy and the strategies will have great impacts on pre-clinical and clinical studies.

? DESCRIPTION: Pathways in the adult central nervous system (CNS) are unable to regenerate after injury, leaving victims of traumatic nerve damage or degenerative disease severely disabled. Improving the regenerative capacity of the CNS may improve functional recovery, quality of life, as well as decrease overall healthcare costs for many of these patients. A major hurdle, however, is the non-permissive nature of the CNS to axon regeneration. Elucidation of the molecular signaling cascades that inhibits axon re- growth has identified the pivotal role of a common intracellular 'molecular switch' - RhoA GTPase. C3 transferase, a bacterial exoenzyme, inhibits RhoA via ADP- ribosylation and its local application promotes axon re-growth in various CNS injury models. This method of delivery is however limited to a duration of several days, likely insufficient for the regeneration of long axons and sustained neuron survival. To address these issues, we have engineered viral vectors to allow continuous delivery of C3 via gene therapy. A cell-permeable and secretable version of C3 has been developed for more widespread and effective RhoA inactivation. Our objective is to test a variety of different approaches of viral vector - mediated C3 expression to identify the most effective delivery and therapeutic window for CNS axon regeneration in a model of optic nerve injury, the optic nerve crush (ONC). The successful results of these experiments will lay the foundation for the extension of our approach to treat other neuropathology's including spinal cord injury, brain injury, and stroke and neurodegenerative diseases.

Abstract

Optogenetic control of neuronal activity has become a driving force in neuroscience research but its clinical application has been limited due to the fact that delivery of physical light into the brain poses a technical burden. This proposal aims to develop novel optogenetic probes that can report neuronal activity in a non-invasive manner and provide neuromodulation throughout the brain.

This project will develop layers of spatiotemporal control over optogenetic activation by a diffusible chemical (drug) in combination with activity-dependent expression and activation. Neuromodulation will be delivered to neurons autonomously only when and where it is needed. These new reagents will offer two new versatile methods of probing neural circuitry in a noninvasive manner: optically reporting neural activity via bioluminescence and perturbing neural circuitry in a closed-loop fashion. This will be particularly important for conducting long term invivo studies and future clinical translation.

PROJECT SUMMARY Epilepsy, occurring in 1 percent of the world?s population, is associated with disability, injury, cognitive and neurological dysfunction, depression, loss of productivity, socioeconomic decline and even death. Of this population, 30 percent of epilepsy cases are medically intractable, leaving surgical interventions as the only option for treatment. Whereas open resection, the current surgical standard of treatment, can yield seizure freedom rates as high as 60-80 percent, these are often associated with cognitive dysfunction and focal neurological deficits. Particularly, patients with dominant hemisphere mesial temporal lobe epilepsy (MTLE), the target population for this proposal, are at risk for significant decline in memory and associated disability. The only option for these patients at present is electrical neuromodulation which, although effective at reducing seizures, only achieves seizure freedom in ~10% of patients. We have recently found that delivering asynchronous pulses distributed across a multielectrode array of 16 microelectrodes, and stimulated at low (theta) frequency, is more effective than macrostimulation in controlling seizures in a rodent model of MTLE. The objective of the proposed project is to optimize asynchronous distributed multielectrode stimulation (ADMES) in a realistic large animal model of epilepsy - non-human primates (NHP) that have been administered penicillin (PCN) in the hippocampus to induced repeated spontaneous seizures. This research will capitalize on the availability of a new commercial neurostimulation system (RC+S, Medtronic) that uniquely allows our novel approach to be implemented. We will also exploit the novel bi-directional feature of this unit to optimize our therapy with both open-loop and closed-loop approaches to ADMES. We will first implement ADMES in our NHP model and quantify effects on seizure frequency and length, and rule out adverse effects on recognition memory. In parallel, we will characterize the response of physiological biomarkers such as synchrony to adjustment of ADMES stimulation in an externalized system. This will allow us to develop both open-loop and closed-loop control policies to optimize these biomarkers as a proxy for seizure control. The most effective stimulation parameters will be implemented in 8 NHPs using the RC+S neurostimulator and benefit on seizure frequency and effects on memory will be evaluated. If seizure reduction is ?50% then we will advance to an early clinical feasibility study. For this, we will first identify electrophysiological biomarkers and characterize the effects of stimulation parameters informed from our NHP study on those biomarkers during invasive monitoring of MTLE patients and then move to an early feasibility trial of ADMES in 6 patients. The final stimulation parameters will be implemented in RC+S and behavioral seizure reduction and memory testing for safety will be quantified over 12 months. At the completion of this aim we will have demonstrated the feasibility of using ADMES and the RC+S; positive results should lay the foundation for a larger clinical trial for MTLE, with possible application to the other epilepsies. This research capitalizes on a strong academic/industry/national laboratory collaboration between clinicians, scientists and engineers, and a rational, stepwise translational approach through a realistic animal model to early feasibility testing in patients, to bring new neurotechnology and control theory applications to bear on a major health concern.

?-Synucleinopathies are neurodegenerative diseases characterized by intracellular inclusions of ?-synuclein (?- syn) aggregates and they include conditions such as Parkinson?s Disease (PD) and Dementia with Lewy Bodies (DLB). A prevailing view is that disease-associated factors such as aging compromise the ability of neurons to efficiently clear abnormally folded proteins which leads to the formation of intracellular aggregates and neurodegeneration. While enhancing the clearance of misfolded ?-syn is a potential therapeutic strategy for PD, current methods to activate cellular mechanisms for protein degradation rely mostly on pharmacological inducers or conventional gene delivery interventions. A translational roadblock in these approaches is the lack of control over dosage, precise time of intervention, and undesirable effects associated with the broad and sustained modulation of cellular degradation pathways. To address these therapeutic needs, we propose to develop a responsive gene therapy for the self-sufficient delivery of a neuroprotective therapy targeting the clearance of misfolded ?-syn species. In a cellular model of ?-syn seeded aggregation, we will demonstrate that our gene therapy approach can detect biological responses associated with the accumulation of ?-syn (Aim 1) and respond by modulating protein degradation pathways accordingly (Aim 2). We expect the outcomes of this project to enable a strategy where a therapy is produced as needed by the affected brain regions, opening the possibility to intervene at an early stage for the treatment of otherwise intractable neurodegenerative conditions such as PD. This project has the potential to be transformative as it introduces a modular platform technology with translational potential for other neurological targets linked to the neurotoxic behavior of misfolded proteins (e.g. amyloid-?, tau).

PROJECT SUMMARY/ABSTRACT Epileptic seizures can be characterized as concerted and synchronized activity of neurons across the brain for an extended period of time. We hypothesize that, as for other normal brain-controlled behavior, epileptic seizures are not caused by random activity of neurons, but rather arise from activity in a specific, organized brain network. Our overarching goal is to elucidate such a seizure-specific network in the brain and to deliver genetic neuromodulation specifically to such a seizure-generating network for tailored seizure suppression. In our proposal, we first identify all the critical brain cells that make up that seizure network in acute and chronic rodent models of epilepsy. Then, we will manipulate such a network to stop seizure occurrence. We will identify and visualize brain structures and cells responsible for generation of seizures in the whole brain by labeling these cells with a fluorescent protein tag utilizing sophisticated gene expression techniques in genetically modified mice (Specific Aim 1). This seizure-specific labelling of neurons occurs when they exhibit extensive activity in the presence of a chemical in the system during a seizure episode. This labelling procedure will be repeated to examine if the same neuronal populations become active in two separate episodes of seizures. The cells labeled with the fluorescence reporter will be examined by fluorescence microscopy. Overlapped labelling of neurons between two seizure episodes will support our hypothesis that the same subset of neurons is repeatedly involved in generation of seizures. We will then employ a similar strategy to deliver genetic neuromodulation to a seizure-generating network (Specific Aim 2). We engineered a viral vector that carries a molecular tool that suppress neuronal activity when an activating drug is injected into the animal. This viral vector will be injected into a brain region responsible for generation of seizures in the rodent models of epilepsy we will use. We expect that such manipulation will suppress subsequent seizures. Our hypothesis views and treats epileptic seizures as a network function in the brain. Together with robust network-specific suppression of seizures in mouse models of epilepsy, this will change the way we view and treat this disease.