This project seeks to develop new treatments for glaucoma based on protection of retinal ganglion cells (RGC) from intraocular pressure (IOP) related stress at the optic nerve head (ONH). The PI recently published that oral losartan?s inhibition of transforming growth factor ? decreases RGC death in experimental glaucoma. The present work uses related sartans, but delivers them by periocular injection in sustained delivery form. Further drugs will be screened by a new test using inhibition of pERK and thrombospondin in immunoblot after short-term IOP elevation in mice. Human neuroprotection trials will have all persons undergoing IOP-lowering and some assigned to neuroprotection. We will do this in glaucoma animals, to improve the translation of animal to human research. IOP lowering in rodents will be done by innovative sustained delivery of dorzolamide and latanoprost, developed in our lab by collaborators in this proposal, Ian Pitha and Justin Hanes, eliminating daily eyedrop treatment for patients and mice. To identify the pathways of early RGC glaucoma damage and to test beneficial effects of sartans, we developed two new ex vivo ocular models. First, mouse eye ONH and sclera are studied in transgenic mice with fluorescent astrocytes under controlled IOP conditions, viewed from posteriorly with optic nerve removed to study the ONH-sclera mechanical behavior by second harmonic generation and 2P confocal imaging. IOP is raised and its effects on ONH- sclera unit modeled using 3D DVC and finite element analysis in collaboration with mechanical engineer, Vicky Nguyen. The effects of age, mouse strain, past glaucoma exposure, connective tissue modification, and drug treatment will each be evaluated. This will improve understanding of glaucoma pathogenesis and identify better drug candidates for RGC protection. The second explant allows study of longitudinal view of the optic nerve head and nerve viewed after enucleation by confocal 2P microscopy in transgenic mice, 2 strains with selective RGC axon fluorescence, one with fluorescent amyloid precursor protein (APP), 2 have fluorescent mitochondria, and 2 fluorescent astrocytes. In mitochondria, we measure quantitative changes in their density, speed of axonal transport and free radical content. Axon damage is quantified by assessment of APP transport and axon integrity index. Glaucoma?s initial injury occurs in this ONH zone, allowing development of uniquely new information in real time video on axon damage. Comparing sustained delivery drug-treated and control animals, we can find candidate beneficial drugs later to be tested in full chronic glaucoma models.
To improve the highly prevalent loss of vision due to glaucoma, we will develop the first sustained delivery method for improving the ocular response to eye pressure. Beginning with the sartans, which have already shown definitive protective effect, we will investigate other agents that produce similar or new beneficial effects on the sclera?s response to elevated IOP in mouse models. New explant systems for study of glaucoma injury and its treatment will investigate living nerve axons and astrocytes at the site of glaucoma injury.
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