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P. Jha, B. Matta, R. Tytarenko, P. S. Bora, N. S. Bora; Complement Activation in Chronic Ocular Hypertension Model. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2649.
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To examine the role of complement activation in a chronic ocular hypertension model.
Intraocular pressure (IOP) was elevated in left eye of Lewis rats by laser photocoagulation (two treatments, 7 days apart) of episcleral and limbal veins. The right eye was left untreated and served as control. Rats were sacrificed (n=3/time point) at day 14, 21, 28, 35, 42 and 49 post-laser. The retina was harvested from laser-treated eyes as well as untreated control eyes and processed for paraffin embedding, RNA extraction and protein extraction. Paraffin sections were used for immunostaing for glial fibrillary acidic protein (GFAP), MAC, C3 and TUNNEL. Complement activation in retina were monitored by semi-quantitative Western blot for C3 split products. In some experiments Lewis rats were injected with cobra venom factor (CVF, >30 units/rat, i.p.) at day 7, 14, 21 and 28 post-laser, to deplete complement. These animals were sacrificed on day 30.
Increased deposition of C3 split products and MAC was observed (using immunohistological analysis) in the retina of the animals with increased IOP compared to the animals with normal IOP. Increased deposition of MAC also correlated strongly with increased GFAP staining. Complement activation as observed by C3 split products followed the same trend as the increase in IOP. No change in C3 levels was observed in the control eyes and the level remained at baseline level. Depletion of complement by CVF resulted in decrease in GFAP, C3 and MAC staining in retina of the animals with elevated IOP. Drastic decrease in C3 split products, and MAC in the retina of CVF treated Lewis rats was further demonstrated by Western blot analysis. Additionally, CVF treatment resulted in reduction of TUNNEL staining in ganglionic cell layer.
Our results provide strong evidence that complement activation contributes to loss of retinal ganglion cells in the eyes with increased IOP.
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