The long-term goal of this project is to define the cellular and molecular mechanisms underlying hemodynamic abnormalities in glaucoma and to find a means to mitigate retinal ganglion cell damage. In this project, we will test a novel hypothesis that astrocytes are central to pressure-initiated ocular BF autoregulation, as they sense transmural pressure and tissue oxygen levels to coordinate the perivascular astrocytic network and feedback to vessels to modulate diameter and thus blood flow and that failure of this mechanism results in hemodynamic imbalance. The hypothesis will be tested in rat retina and monkey optic nerve head in three specific aims: (1) Pressure-initiated retinal astrocyte activation is independent of neuronal and metabolic activity. This will be achieved by elimination of retinal ganglion cell and application of systemic hyperoxia. (2) Astrocytes modulate retinal vascular tone and coordinate pressure-initiated autoregulation under modulation by tissue oxygen status. To test the hypothesis, all or a specific pathway of the proposed feedback mechanism in the astrocytes will be inhibited and tested under hyperoxia and normoxia to compare the hemodynamic parameter changes under the conditions. (3) Pharmacological interruption of astrocyte feedback mechanism impairs hemodynamic balance within the optic nerve head and this is further modified by the alteration of oxygen supply. The following techniques are used: (1) an ex vivo system that enables precise control of intravascular and extravascular pressures thus allowing simultaneous quantifying astrocytic Ca2+ (Fluo-4AM) and changes in vascular diameter. (2) In vivo imaging of astrocytic Ca2+ (Fluo-4AM, fluorescence) and vessel diameter (infrared) using a confocal scanning laser ophthalmoscope, while blood pressure and intraocular pressure are manipulated in both rats and nonhuman primates. (3) Combining pharmacological inhibitors and adeno-associated virus 8 vector delivery with an astrocyte-specific promotor inhibit either all the bioactivity of astrocytes or the key proteins in the proposed astrocytic feedback and propagation pathways. (4) In vivo assessment of BF autoregulation in retina and optic nerve by dynamic autoregulation analysis using laser speckle imaging techniques. The proposal is expected to elucidate a novel role for astrocytes in pressure-initiated BF autoregulation, thus significantly expanding our understanding of hemodynamic control in the central nervous system. This basic understanding provides a platform for future studies of novel therapeutic targets in diseases associated with autoregulation dysfunction, including glaucoma.

Public Health Relevance

This project will establish a novel role for astrocytes in maintaining hemodynamic homeostasis in the retina and ONH. We believe that this is mechanism of hemodynamic control that exists in both eye and brain. The outcome will also generate hypotheses for future studies of novel therapeutic targets in diseases associated with autoregulation dysfunction, including glaucoma.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY019939-08
Application #
9682506
Study Section
Diseases and Pathophysiology of the Visual System Study Section (DPVS)
Program Officer
Liberman, Ellen S
Project Start
2010-08-01
Project End
2021-01-31
Budget Start
2019-04-01
Budget End
2021-01-31
Support Year
8
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Legacy Emanuel Hospital and Health Center
Department
Type
DUNS #
050973098
City
Portland
State
OR
Country
United States
Zip Code
97232
Li, Hui; Bui, Bang V; Cull, Grant et al. (2017) Glial Cell Contribution to Basal Vessel Diameter and Pressure-Initiated Vascular Responses in Rat Retina. Invest Ophthalmol Vis Sci 58:1-8
Ing, Eliesa; Ivers, Kevin M; Yang, Hongli et al. (2016) Cupping in the Monkey Optic Nerve Transection Model Consists of Prelaminar Tissue Thinning in the Absence of Posterior Laminar Deformation. Invest Ophthalmol Vis Sci 57:2914–2927
Fortune, Brad; Hardin, Christy; Reynaud, Juan et al. (2016) Comparing Optic Nerve Head Rim Width, Rim Area, and Peripapillary Retinal Nerve Fiber Layer Thickness to Axon Count in Experimental Glaucoma. Invest Ophthalmol Vis Sci 57:OCT404-12
Fortune, Brad; Reynaud, Juan; Hardin, Christy et al. (2016) Experimental Glaucoma Causes Optic Nerve Head Neural Rim Tissue Compression: A Potentially Important Mechanism of Axon Injury. Invest Ophthalmol Vis Sci 57:4403-11
Wang, Lin; Cull, Grant A; Fortune, Brad (2015) Optic nerve head blood flow response to reduced ocular perfusion pressure by alteration of either the blood pressure or intraocular pressure. Curr Eye Res 40:359-67
Cull, Grant; Told, Reinhard; Burgoyne, Claude F et al. (2015) Compromised Optic Nerve Blood Flow and Autoregulation Secondary to Neural Degeneration. Invest Ophthalmol Vis Sci 56:7286-92
Cao, Li; Wang, Lin; Cull, Grant et al. (2015) Alterations in molecular pathways in the retina of early experimental glaucoma eyes. Int J Physiol Pathophysiol Pharmacol 7:44-53
Wang, Lin; Cull, Grant; Burgoyne, Claude F et al. (2014) Longitudinal alterations in the dynamic autoregulation of optic nerve head blood flow revealed in experimental glaucoma. Invest Ophthalmol Vis Sci 55:3509-16
Yu, Jintao; Liang, Yi; Thompson, Simon et al. (2014) Parametric transfer function analysis and modeling of blood flow autoregulation in the optic nerve head. Int J Physiol Pathophysiol Pharmacol 6:13-22
Wang, Lin; Burgoyne, Claude F; Cull, Grant et al. (2014) Static blood flow autoregulation in the optic nerve head in normal and experimental glaucoma. Invest Ophthalmol Vis Sci 55:873-80

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