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Yik Tung Tracy Ling, Mary Ellen Pease, Harry A Quigley, Thao D Nguyen; Actin and GFAP Network of Mouse Optic Nerve Head and Alterations with IOP. Invest. Ophthalmol. Vis. Sci. 2020;61(7):998.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the network structure of the mouse astrocytic lamina after 3-day (3d) IOP elevation and its association with the degree of IOP change.
IOP elevation was induced in the left eyes of 6-month old GFP-GLT1 mice by microbead injection (n=6). The contralateral right eyes were untreated controls. Mice were anesthetized after 3 days, and the pre-sacrifice IOP was measured. The difference in pre-sacrifice IOP between the treated and control eyes of each mice was recorded as the IOP difference (ΔIOP). Optic nerve (ON) of 1mm length were separated from the posterior eye wall using a razor blade and cryopreserved. The ON segments were cryo-sectioned serially into 8 or 10μm slices. GFAP, Actin and cell nuclei were stained and imaged with a confocal microscope (Fig 1a&b). A Matlab program was developed to analyze the staining in the unmyelinated region of the ON, which extends to 240µm posterior from the Bruch’s membrane opening. The ratio between 3d IOP and control lamina of each measured outcome was averaged every 40µm to represent the difference between the two groups, and its correlation with IOP was analyzed using a general linear model.
Larger lamina (17.8%), GFAP (13.7%) and actin (16.3%) area were observed after 3d IOP elevation (p≤ 0.001, Fig 1a-c&g). However, the area densities of GFAP (p=0.005, Fig 1g) and actin (p=0.08) decreased by 3.74% and 1.1% respectively in the glaucoma group. The GFAP processes were on average thinner in the central region than in the peripheral and rim region of the lamina (p≤0.01, Fig 1d-f), while the processes in both the central and peripheral region were thinner after 3d IOP elevation (p<0.01, Fig 1f). The axonal area, measured as the lamina area minus actin and nuclear areas, and the number of separated axonal compartments also increased after 3d IOP elevation (p<0.01, Fig 1i). Further, larger difference between 3d IOP and untreated eyes was associated with greater ΔIOP for the following outcomes, the lamina, GFAP and actin area (p≤0.001); total axonal area (p=0.02) and number of axonal compartments (p=0.002, Fig 2). Actin fibers were also more aligned with greater ΔIOP (p=0.001).
Astrocytic processes were thinner after 3d IOP elevation but the overall lamina, GFAP, actin and axonal area increased. The extent of these alterations may be associated with the degree of IOP elevation but more specimens are needed to verify the effects of ΔIOP.
This is a 2020 ARVO Annual Meeting abstract.
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