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N. Sugi, M.C. Kamradt, S. Mukai, M.S. Gregory, B.R. Ksander; The Role Of Small Heat Shock Proteins In Glial Scarring Of The Mouse Retina Following Laser Photocoagulation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2583.
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Laser induced retinal burns trigger gliosis that results in retinal scarring. αB–crystallin is a small heat shock protein that is expressed in the retina and can function as an anti–apoptotic signal and/or a pro–inflammatory signal. We hypothesize that αB–crystallin participates in gliosis by triggering the activation of RPE and infiltrating inflammatory cells.
Groups of C57BL/6 mice received 4 laser burns (spot size: 125 µm, duration time: 100 msec, and energy: 100 mW) one disc diameter from the optic nerve. The mice were sacrificed and the eyes enucleated on days 0, 1, 3, 7, and 14. Immunohistochemistry was performed using specific antibodies for αB–crystallin and GFAP on: (i) frozen sections of sensory retina and (ii) whole retinal flat mounts. The tissue was analyzed by epifluorescent and confocal microscopy.
Within 24 hrs after laser photocoagulation, at the burn site there were: (i) thinning and loss of RPE cells, (ii) disruption of Bruch’s membrane, (iii) proliferation of cells in the choroid, and (iv) loss of cells in the ONL and minor loss of INL. αB–crystallin was expressed at the highest levels in the RPE cells surrounding the site of laser–induced RPE destruction. In addition, αB–crystallin was also expressed at high levels in the sensory retina at the site of the laser burn. The expression of αB–crystallin was highest in these cells immediately after the laser burn and preceded the infiltration of inflammatory cells into the lesion. The expression of αB–crystallin decreased steadily in intensity over the next two weeks. By 72 hrs, RPE cells were observed migrating into the area where RPE cells were lost and also migrating into the ONL. At this time we observed increased expression of GFAP in Müller cells, suggesting the activation of Müller cells within the laser burn.
Our results indicate that the up–regulation of αB–crystallin in the cells surrounding the retinal burn precedes the activation of Müller cells and infiltration of inflammatory cells. DOD PR033243.
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