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Jie Ma, Yu Sun, Gianna C Teague, Kameran Lashkari; Temporal-Spatial Expression of RGC Markers as Indicators of RGC Loss in Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5630.
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© ARVO (1962-2015); The Authors (2016-present)
Accurate quantification of retinal ganglion cells (RGCs) is an important measurement to estimate RGC loss and evaluate the progression of glaucoma. The present study aims to clarify the temporal-spatial features of RGC loss across the retina in the microbead-induced model of murine glaucoma.
Four-month old C57BL/6 mice (n = 60) were injected with microbeads (15 µm diameter, 3 µl) in their anterior chambers to induce elevated IOP. IOP was measured every 3 days. Mice were sacrificed every two weeks for up to 3 months. Retinal flatmounts were prepared and subjected to immunohistochemistry (IHC) or flow cytometry (FC) for expression of RGC markers, β-III Tubulin and Brn3a. For IHC the expression of these markers was evaluated across peripheral, intermediate and central retina. FC determined that total number of cells expressing these markers. Statistical analysis included ANOVA and two-tailed Student’s t-test.
Microbead injection resulted in reproducible IOP elevation from 11.55 ± 0.05 at baseline to 28.06 ± 1.40 at week 2, decreasing to 21.44 ± 1.01 at week 5 (mmHg, P<0.05). Between baseline and 3 months, the densities of β-III Tubulin+ and Brn3a+ cells decreased respectively from by 34% (from 3104 to 2036 cell/mm2) and 33% (from 2674 to 1914) at periphery; 21% (from 2174 to 1452) and 28% (from 1120 to 918) at intermediate; 18% (from 2710 to 2141) and 9% (from 3492 to 3171) at center of retina. Temporally, RGC loss represented by the two biomarkers showed a linear correction (both P<0.05). Spatially, β-III Tubulin+ cells were more prevalent than Brn3a+ cells at periphery (P<0.05), even at intermediate (P>0.05) and less frequent in central retina (P<0.001).
Microbead model of glaucoma is a reproducible model of RGC. IOP elevation induces a temporal-spatial loss of RGC cells. Overall, there was a graded loss of RGCs from peripheral to central retina with an earlier and more profound loss of both β-III Tubulin+ than Brn3a+ cells in peripheral retina. In peripheral and central retina, equal ratios of both β-III Tubulin+ than Brn3a+ cell loss were observed. In intermediate retina, higher ratio was observed of β-III Tubulin+ over Brn3a+ cell loss. These findings suggest that elevated IOP induces a temporal-spatial pattern to RGC loss in glaucoma.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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