Arthur Weber - US grants

Primary open-angle glaucoma (POAG) is a leading cause of blindness. Clinically, most cases of POAG are characterized by an increase in intraocular pressure (IOP), progressive changes in the structure of the optic disc, and visual field defects. While numerous studies have focused on the degenerative effects that chronic elevation of IOP has on fibers in the optic nerve, few data are available concerning the pattern or the time course of glaucomatous neuropathy that occurs within the primate retina or its central target, the dorsal lateral geniculate nucleus (LGN). The overall goal of the proposed research is to define the temporal relation between the onset and progression of glaucoma measured clinically, and the degeneration of retinal ganglion cells and LGN neurons. Since no previous glaucoma-related study has examined the morphology of single ganglion cells, a necessary first step is to identify those structural features that characterize ganglion cell degeneration in the glaucomatous eye. To do this, the somata and dendritic fields of ganglion cells in the retinae of normal monkeys and monkeys with clinically well-defined, experimentally-induced, glaucoma will be compared by labeling single ganglion cells intracellularly in an in vitro retinal preparation. Once the structural features characteristic of ganglion cell degeneration are defined, the next series of experiments will determine the duration of increased intraocular pressure that produces the earliest detectable changes in ganglion cell morphology. Single ganglion cells will be injected in the retinae of monkeys that have had the pressure in one eye elevated for a period of time ranging from 2 weeks to 3 months. The focus of these experiments, which is the central goal of the proposed studies, is to define the temporal relation between clinically recognizable glaucomatous neuropathy and the onset and progression of retinal ganglion cell degeneration, thus establishing the level of neuronal damage that may precede, as well as accompany, the clinical stages of the disease. The proposed work also will address the possibility that glaucoma affects different classes of ganglion cells, and therefore different functional visual channels selectively. Previous studies, based on Niss1-staining of cell bodies, have suggested that large ganglion cells (presumably parasol cells-M pathway) may be more vulnerable than the smaller, midget, ganglion cells (P pathway). Since intracellular dye injection stains not only the cell body but also the dendritic tree of ganglion cells, the proposed experiments make it possible to determine unequivocally whether parasol cells are affected preferentially during the early stages of glaucoma. Further, since midget and parasol cells project to different layers of the LGN, comparison of the neuronal changes in the parvo- and magnocellular layers of the LGN, which receive input from midget and parasol ganglion cells respectively, will provide additional information regarding possible selective effects of glaucoma. Because the M and P pathways subserve different visual functions, the results of these experiments have the potential to direct the future development of more sensitive and specific tests for the early detection of glaucoma. The results also will serve as the basis for later exploring new treatments aimed at mitigating or preventing glaucoma-induced ganglion cell degeneration, by delivering neuroprotectants to the glaucomatous eye.

DESCRIPTION (Adapted from applicant's abstract): Primary open-angle glaucoma (POAG) is a leading cause of blindness in the United States. In many cases, the disease is characterized by an elevation of intraocular pressure (IOP), progressive changes in the appearance of the optic disc and retinal nerve fiber layer, and visual field defects. Over the past several years, a number of studies have described the degenerative effects that chronic elevation of IOP and glaucoma have on fibers in the optic nerve, as well as the concomitant loss of ganglion cells that occurs within the retina itself. More recently, the applicants have combined the monkey model of experimental glaucoma with intracellular staining techniques to examine the morphological changes that characterize glaucomatous neuropathy at the single cell level. These studies showed, for the first time, that the earliest signs of glaucoma-related retinal ganglion cell (RGC) degeneration involves structural abnormalities associated with the dendritic arbors of these neurons. Since retinal ganglion cells receive all of their input from more distal retinal elements through their dendrites, abnormalities in dendritic structure suggest a reduction in synaptic efficacy, and early fractional deficits at the single cell level. A primary goal of the studies proposed here is to use combined anatomical and electrophysiological techniques to determine the extent to which glaucoma-related changes in ganglion cell structure might correlate with changes in ganglion cell function. A second important outcome of the investigator's previous years of work was the finding that morphological changes at the level of the cell body occur later than those at the dendritic tree. This suggests that there is a "window of opportunity" during which the application of neuroprotectants to the diseased visual system might serve to slow or reverse ganglion cell death. Thus, a second goal of the proposed studies is to determine, using a cat optic nerve crush model of retinal ganglion cell atrophy, the extent to which different doses, delivery routes, and delivery rates of brain-derived neurotrophic factor (BDNF), a known neuroprotectant in the small rat eye, might also serve to enhance the survival of ganglion cells in primate-sized eyes and their primary target neurons in the thalamus of the brain.

[unreadable] DESCRIPTION (provided by applicant): Glaucoma is a disease of the visual system often characterized by pressure-induced damage to the optic nerve. This results not only in a loss of ganglion cells from the retina, but also degeneration of their target neurons in the lateral geniculate nucleus (LGN) of the thalamus. While numerous studies have shown that direct application of neurotrophic factors to the eye can reduce ganglion cell loss following optic nerve injury, an important issue that has not been addressed is whether 'rescued' neurons retain their normal structural and functional properties, and thus were worth saving. The first specific aim of this proposal is to compare the morphologies and visual response properties of ganglion cells from normal eyes with those from eyes that have received either an optic nerve injury alone, or nerve injury combined with intraocular treatment of brain-derived neurotrophic factor (BDNF), a potent neuroprotectant in the eye. [unreadable] [unreadable] The basic mechanism underlying the progressive neuropathy that characterizes glaucoma is thought to be a reduction in the level of trophic material retinal ganglion cells receive from their target neurons in the LGN due to the nerve injury. This results not only from pressure-induced blockage of axonal transport within the nerve, but also the progressive loss of target neurons, and thus trophic factor levels, within the LGN itself. At present, however, no data are available concerning the extent to which treatment beyond the eye might enhance and/or prolong ganglion cell survival compared with treatment of the eye alone. The second specific aim of this study will examine the neuroprotective effects that application of BDNF to both the eye and thalamus has on retinal ganglion cell and LGN neuron survival following different durations post nerve injury. [unreadable] [unreadable] In all cases, the structural and functional integrity of the retina, as well as the entire central visual pathway, will be assessed using non-invasive electroretinographic and visual evoked methods, and with intracellular recording and labeling of single ganglion cells using our isolated, living retina, preparation. [unreadable] [unreadable] The proposed studies represent a continuation of our previous work concerning optic nerve injury and retinal ganglion cell degeneration. They will provide new and important information concerning the functional integrity of ganglion cells following trophic factor-based rescue, and they will advance our understanding of the extent to which new treatment strategies for long-term ganglion cell survival and central visual pathway stability also should include treatment beyond the eye itself. [unreadable] [unreadable]

PI: Li

Proposal No: 1264772

Technical Description and Intellectual Merit: Optic nerve injuries due to diseases (e.g. glaucoma) or trauma often result in lifelong disabilities, and at present most are incurable. Retrograde degeneration of ganglion cells following optic nerve injuries is believed to result primarily from a reduction in the transport of neurotrophic materials these neurons obtain from their target neurons in the visual thalamus. Current neurotrophic factor-based treatments are inadequate to provide long-term neuroprotection and can produce abnormal dendritic morphology in both transduced and non-transduced nerve cells. The objective of this proposed research is to investigate an innovative strategy for treatment of optic nerve injuries, combining neurotrophic therapy of the eye with optical stimulation of the visual cortex to promote endogenous neuroprotection and preservation of retinal ganglion cells (RGC) and retinal function. It is hypothesized that combined treatment of both the eye and visual cortex provides a more significant and sustained level of neuroprotection as compared to treating the eye alone. Specifically, optical stimulation of cortical neurons across different layers will be achieved via a novel three-dimensional (3-D) Opto-µECoG (electrocorticography) interface, which consists of multiple micro light emitting diode (µ-LED) light sources, out-of-plane microscale polymer waveguides, and transparent µECoG electrodes on a single flexible polymer platform. Integration of individually addressable µ-LED chips with waveguides will help minimize the LED light scattering within brain tissue to achieve high-spatial resolution and precise light delivery to the target neurons. The transparent epidural ECoG electrodes will permit real-time monitoring of light-induced neural activity in visual cortex. The functionality and reliability of the engineered Opto-µECoG interface will be evaluated using both in-vitro primary cortical slices and in vivo rat models. Light-induced activation of the visual thalamus will be assessed, as indicated by enhanced electrical activity of neurons in the visual thalamus as well as up-regulated levels of BDN Fandits associated anti-apoptotic proteins (ERK 1,2, PI3K/Akt, and CREB).Enhanced neuroprotection and preservation of vision following the combined treatment will also be investigated ina rat model with optic nerve trauma, by comparing electroretinographic responses from animal eyes and vision-evoked potentials from visual cortex. The ultimate goal is the development of optogenetics-based treatment strategies not only for optic neuropathies, but also for other brain injuries in general. The PIs have established collaborations and complementary research expertise in the areas of biomedical microelectrome chanical systems (BioMEMS), neural engineering, and neurophysiology, which make this project viable in its execution.

Broader Impacts: The scientific impacts of this research include: 1) investigation of a transformative treatment strategy for neural protection and restoration in eyes with glaucoma, 2) development of optogenetics-based engineering tools for seamless communication with neurons, and 3) in-depth understanding of the mechanisms of trauma-induced cellular degeneration and neuroprotection. While it is specifically tailored for glaucoma treatment, the proposed treatment strategy can also be used to treat trauma-induced optic nerve injuries and other brain injuries such as sensory deficits, Parkinson's disease, and depression. The most pronounced long-term benefits of this work to society include a reduction of healthcare cost and quality of life improvement for a sizeable, and growing, population affected by the above conditions. In addition to its scientific impacts, this work will offer unique research experiences for undergraduate and graduate students to understand technical details of different disciplines and develop multiple, translational, biomedical skills. To reach larger audiences, the results will be shared with students through science fairs, with scientific communities through conference presentations and journal publications, and with the public through exhibits. The integrated outreach program will be very effective due to the visually appealing nature of microscale devices and systems. The curriculum development and improvement will provide tremendous opportunities to introduce interdisciplinary topics and hands-on experimental experiences to students at multiple levels. The results of the educational programs will be assessed through internal and external evaluators and disseminated through conferences (e.g. ASEE, FIE and MEMS) and in-house programs, such as Frontiers in Science, at MSU. These efforts will encourage more students to pursue careers in research and ultimately produce skilled and knowledgeable workforces for biomedical, neural science, and engineering.

ECCS Prop. No. 1407880

Proposal Title:

Implantable, Wireless, and Power-Efficient Trimodal Neural Interface for Electro-Optogenetic Manipulation of Visual Cortex in Small Freely Behaving Animals

Award Goal
This proposal aims to realize an integrated, wireless, trimodal opto-electro neural interface to tackle the critical challenge of high-resolution spatiotemporal mapping and closed-loop control of visual cortex, which will enable better understanding of the structure and function of brain networks during visual processing of small, freely behaving animals.

Nontechnical Abstract

Blindness has affected millions of people worldwide, and at present is incurable. A cortically-based visual prosthesis is believed to provide a therapeutic solution for all causes of blindness. However, restoration of visual senses to a useful level has not yet been achieved with cortical implants, mainly due to the complex organization of visual cortex and visual preprocessing in the retina and the lateral geniculate nucleus. Therefore, the objective of this proposal is to realize a novel neural interface for high-resolution stimulation and recording of neural activity in visual cortex, which will enable better understanding of the structure and function of neural networks during visual processing. The proposed technology development of this research will yield novel and enabling tools for seamless communication with brain networks of small animals, by which neuroscientists could significantly move fundamental neuroscience knowledge forward. The developed ultra-low-power microelectronics and advanced microfabrication techniques can be applicable to other implantable devices and biomedical systems. In addition, the proposed project will offer unique training opportunities for students at multiple levels. Integrated outreach activities will effectively convert state-of-the-art science and technologies into educational resources accessible to local K-12 schools and communities. To reach broader audiences, the results will be disseminated through science fairs, publication, workshops and conferences.

Technical Abstract
As the core of this proposal, a wireless, trimodal neural interface will be developed to form the most comprehensive interface with the central nervous system of awake, freely behaving animal subjects. In particular, a multichannel opto-electro array will incorporate epidural light emitting diodes, intracortical microscale waveguide, and microelectrodes in a single platform, capable of optogenetic/electrical stimulation and electrical recording of neural activity of specific cell populations. Implantable, ultra-low-power microelectronic system-on-a-chip will be able to receive and process neural recording data and drive the optical/electrical neural stimulating array. Wireless telemetry links will be implemented to transfer power and data efficiently between the external data-acquisition/control units and implanted neural interface. These key components will be integrated on a mechanically flexible substrate and encapsulated by a hybrid biopolymer package. The integrated wireless neural interface will be implanted and characterized in the primary visual cortex of anesthetized and freely behaving rats, in order to validate its efficacy for wireless neural recording and stimulation. The proposed research activities will be conducted by a collaborative team with complementary research expertise in the areas of bioMEMS, microelectronics, and neurophysiology. Achievement of the goals of this research will pave the road towards the development of a fully functional, cortically-based visual neuroprosthetic system capable of generating artificial vision for completely blind individuals. While the proposal is specifically tailored for studying the visual function of the brain, the developed technologies can also be used for functional mapping and controlling of other regions of the brain and nervous system, particularly those related to motor functions (e.g. spinal cord and peripheral nervous systems).