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Delaney CM Henderson, John Gobran, Balwantray C Chauhan; Characterizing longitudinal in vivo changes of RGC dendrites after injury. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2020.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal ganglion cell (RGC) death is preceded by retraction of dendrites and an overall loss of dendritic branch complexity. The aim of the present study was to characterize and contrast the effects of an acute (optic nerve transection, ONT) and a chronic (experimental glaucoma (EG) with magnetic microbead injection) injury on the structure of RGC dendritic arbors.
We used a transgenic mouse line with expression of yellow fluorescent protein (YFP) in <0.5% of RGCs (Thy-1 YFP, line H; Jackson Laboratories, ME) allowing for visualization of the entire dendritic arbor. Mice had either ONT (n=9) or EG (n=5) induced in one eye. Fluorescence confocal scanning laser ophthalmoscopy (Spectralis Multiline, Heidelberg Engineering) was used to perform longitudinal in vivo imaging of YFP+ RGCs to document the progression of injury. Sholl analysis was conducted on in vivo images to quantify dendritic complexity and arbor size changes of YFP+ RGCs over the time course of both injuries.
ONT caused a rapid and severe loss of RGCs over 3 weeks. Early time points were examined to characterize RGC dendritic arbors prior to cell death. Dendritic arbor radii retracted (mean (SD): 179 (33) vs. 160 (49) μm; baseline vs. day 11, n=20 cells) and the peak number of branch intersections at the corresponding time point also decreased (22 (5) vs. 10 (4)) after ONT. Four of the 20 RGCs followed entirely lost fluorescence and became non-detectable prior to day 11. In the EG animals, the mean (SD) IOP integral, an index of IOP elevation compared to the fellow control eye, at day 28 was 144(39) mmHg days. The RGC arbor radii reduced by a smaller amount and over a longer time period (169 (16) vs. 166 (18) μm; baseline vs. day 28 EG, n=9 cells) and peak number of intersections (25 (4) vs. 20 (4)) after prolonged IOP elevation. The area under the curve (AUC) of RGC Sholl profiles, a measure of dendritic complexity, decreased following both injuries; however, to a lesser degree in the EG group (64% vs. 21%, 11 days post-ONT vs. 28 days EG, Figure).
The present study demonstrates that longitudinal in vivo imaging and Sholl analysis can be used to track the progression of RGC injury prior to cell death. A prolonged chronic elevation of IOP resulted in a slower time course of dendritic retraction and loss of RGC arbor complexity compared to ONT.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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