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Timothy Daniel Holley, Mary Tapia, Jae Lee, Richard Lee; Reactive Fibroblasts in Response to Retinal Ganglion Cell Injury. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5637.
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© ARVO (1962-2015); The Authors (2016-present)
The factors which prevent axonal regeneration after optic nerve damage in glaucoma are poorly understood. Using an experimental model of laser-induced damage to retinal ganglion cells (RGCs), we tested the hypothesis that fibrotic scar formation in the retina is one of these inhibitory factors in axonal regeneration.
Transgenic mice which express GFP upon activation of the collagen 1α1 promoter were used (N=7). Baseline and weekly in vivo imaging consisted of spectral domain optical coherence tomography (SD-OCT, Bioptigen, Durham, NC) of the retina with manual segmentation of the retinal ganglion cell layer, confocal scanning laser ophthalmoscopy (CSLO, Heidelberg Engineering, Heidelberg, Germany) detection of GFP-expressing monocytic fibroblastic cells, fluorescein angiography, and direct fundus photography. After baselines measurements, GFP-col1a1 mice were exposed to Nd:YAG photodistruptive laser in one eye (0.3mJ per spot); the alternate eye was used as a control. After 8 weeks, mice were sacrificed and the eyes enucleated and placed into fixative for retinal whole mounts or embedding into paraffin block and sectioned for immunostaining. Immunostaining was for GFP and retinal monocyte and RGC markers.CSLO imaging was used to determine where fluorescence-producing active fibroblasts were in the mouse retina. SD-OCT images were processed through a MATLAB-based program to generate a manually segmented thickness map for the RGC layer of the retina. Measurements were compared against baseline over time and against counterpart control eyes.
CSLO imaging showed baseline fluorescence around large vessels. After injury, a sharp circular increase of fluorescence (corresponding to laser spots) was observed, followed by a gradual decrease suggesting recruitment of fibroblasts acutely to areas of retinal damage.SD-OCT generated topographic retinal thickness maps showed areas of thinning in the RGC layer in the focal areas of Nd:YAG photodisruption.
Our results are consistent with the hypothesis that reactive fibroblast are recruited into areas of RGC damage or death and these cells are involved in scar formation in the retina following damage to the RGC layer. However, which layer(s) of the retina where these cells migrate to, or from where they originate is unknown. Further experiments will be better delineate the pathophysiologic changes observed in response to RGC injury.
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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