Michael J. Moore - US grants

DESCRIPTION (provided by applicant): Disorders of the central nervous system are often associated with little or no recovery due to in part to poor neural regenerative capacity, damaging mechanisms that persist after initial neuronal injury, and inhibitory properties intrinsic to myelin. Regenerative medicine strategies that utilize synthetic or natural materials as permissive environments for maximizing axonal extension may not be sufficient for restoration of sight because axons that extend from each retina cross at the optic chiasm and selectively project to both hemispheres of the brain. Protein ligands, such as ephrin-B2, activate receptors on retinal ganglion cells to induce directional axon growth in order to form the divergent neural projections during embryogenesis. Development ligands such as these may be able to guide regenerating axons when engineered into biomaterials for tissue engineering. However, there is a critical need for physiologically- and translationally-relevant culture models that support the systematic investigation of structural and molecular parameters that may influence tissue growth. The overall goal of this project is to develop a 3D tissue culture model to study the guidance of retinal neurites in response to engineered cues that mimic the spatial distribution of ligands found at the optic chiasm during development. Specifically, we hypothesize that ephrin-B2, immobilized in a spatially-specific manner within a synthetic three-dimensional matrix, will selectively direct neurite outgrowth from embryonic retinal explants in a structural configuration that mimics the optic chiasm. In order to evaluate this hypothesis, we propose the following specific aims: Aim 1: Synthesize a photo-labile peptide hydrogel for localized immobilization of protein ligands. Aim 2: Develop a dual hydrogel platform for 3D retinal neurite outgrowth and incorporation of immobilized protein ligands. Aim 3: Evaluate the efficacy of ephrin-B2, locally immobilized in a 3D peptide hydrogel, to selectively direct neurite outgrowth from embryonic retinal explants. The techniques developed from this work will allow for the systematic manipulation of the spatial arrangement of structural and molecular cues for directing neuronal growth. Thus, it is anticipated that this work will establish a new experimental platform to study neural growth and guidance and also suggest potential treatment strategies to be explored in future studies. Disorders of the central nervous system, including optic neuropathies, are difficult to treat due to a poor capacity for nerves there to regenerate. In the optic nerve, even maximizing nerve axon regeneration may not lead to restoration of sight because nerves from each eye cross at the optic chiasm and project to specific regions at either side of the brain. The use of functional biomaterials that are able to selectively guide growing axons may suggest new treatment strategies for optic nerve and other central nervous system disorders.

1055990, Moore

Proper functioning of the central nervous system is dependent on accurate connections between nerve cells. During both development and repair, nerves navigate toward intended targets by responding to numerous physical and molecular signals from their microenvironment. For example, it has been shown that nerve cells from the retina are attracted toward the optic tract by a chemical called netrin-1 that diffuses through the tissue forming a concentration gradient. These same nerve cells are later influenced to follow a path toward one side of the brain or the other by repulsion from another chemical called ephrin-B2 that is bound to the tissue in a specific location. The precise mechanisms by which cells integrate multiple signals remain unclear, partly because the experimental methods to test such mechanisms have relied heavily upon difficult cell preparations. Synthetic biomaterials are poised as means to more easily and quantitatively control the spatial distribution of physical and molecular guidance cues. The purpose of this proposal is to make use of new photoreactive biomaterials along with computer simulation to develop an integrated model of nerve growth in response to structural and molecular cues in the microenvironment. The models developed will enable unprecedented control of multiple guidance cues, enabling further investigation into how they influence axon guidance.

The research proposed in this application may benefit society by enabling quantitative, more readily-implementable techniques that may aid discovery of biological mechanisms important for embryonic development, neurological disorders, and regeneration processes. Further, the novel biomaterials developed may find use in many unforeseen applications. Educational impacts will also be realized by this proposal. Numerous graduate and undergraduate students will be educated in the investigator?s laboratory, and the techniques developed will be introduced into a course taken by graduate and undergraduate students. The research lab will also serve as a hub for promoting career opportunities in science, engineering, technology, and mathematics to students and teachers in underrepresented minority-serving schools in Louisiana. This will be accomplished through summer research experiences provided to undergraduate students in underrepresented groups as well as to high school teachers in minority-serving high schools in the New Orleans area.

The technology described in this project represents a significant leap forward in the development of a neural 'organ-on-a-chip'. The ability to engineer a biomimetic 3D nerve model will allow for rapid screening of neurotoxicity, neuroprotection, as well as the tailoring of the microenvironment to mimic critical disease models. To this point, only 2D in vitro cell cultures and animal models have been available as pre-clinical tools for drug discovery. Unfortunately, neither of these options translates well to in vivo clinical applications, which is apparent looking at the current failure rates of drugs as well as skyrocketing R&D expenses. This advanced model will allow both academic and industrial scientists to further study underlying mechanisms and therapies related to neurodegenerative pathologies in a uniquely cost effective and timely manner. This technology should increase the molecular understanding of axonal degeneration, neurotoxic consequences and neuroprotective mechanisms.

Successful commercialization of the proposed technology will result in a service-based product marketed towards pharmaceutical testing. The PI has demonstrated that microengineered peripheral neural tissues conduct electrically-evoked compound action potentials and filed a provisional patent related to the fabrication and application of the cell culture model. With this discovery as a foundation, the PI proposes to validate a prototype by demonstrating pathophysiological signatures in microengineered rat tissues. By contacting potential customers, the PI and his team will assess the readiness of the prototype and identify further benchmarks and design criteria. Two critical components will include refining the most effective outputs utilized for preclinical screenings and identifying maximally exploitable experimental paradigms.