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Dorota L. Stankowska, Alena Z. Minton, Shaoqing He, Raghu R. Krishnamoorthy; Neuroregenerative Properties Of Transcription Factor Brn3b In An Elevated IOP Rat Model Of Glaucoma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5370.
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Glaucoma is an optic neuropathy, commonly associated with an increase in intraocular pressure (IOP) leading to neurodegenerative changes in the optic nerve head and apoptosis of retinal ganglion cells. Insult to axons at the lamina cribrosa is an early event that precedes other neurodegenerative changes seen in various animal models of glaucoma. Hence, strategies to promote regeneration of the optic nerve have gained prominence in recent years. Brn3b is a class 4 POU domain transcription factor which has been shown to play key role in regulating retinal ganglion cell axon outgrowth and pathfinding during development in projection neurons. The purpose of this study was to determine if overexpression of Brn3b could promote an axonal regenerative response in the optic nerve in an elevated IOP rat model of glaucoma.
Adult male retired breeder Brown Norway (BN) rats were intravitrealy injected with adeno-associated virus encoding either Brn3b (AAV-Brn3b) or the empty vector (AAV-MCS). Experimental glaucoma was induced in rats by IOP elevation using the Morrison’s method (injection of hypertonic saline through episcleral veins). Transgene expression of Brn3b was assessed by immunohistochemistry using an anti-flag antibody. Two weeks following the injection with the viral vectors BN rats were sacrificed. Retinas sections through the optic nerve head were obtained and stained for Brn3b as well as neuroregenerative markers including growth associated protein 43 (GAP-43), actin binding LIM protein 1 (AbLIM) and acetylated tubulin alpha 1 (ac-Tuba-1) by immunofluorescence technique.
An increased immunostaining for Brn3b was observed two weeks post-intravitreal injection of AAV-Brn3b. An upregulation of the axon-specific GAP-43 protein within the retina as well as in the posterior region of optic nerve was observed after AAV-Brn3b injection. Overexpression of Brn3b promoted the upregulation of two other neuroregeneration markers namely, ac-Tuba-1 and AbLIM.
The AAV-mediated expression of Brn3b produced an increase in expression of markers of nerve regeneration in vivo in the Morrison’s elevated intraocular pressure (IOP) model of glaucoma in rats. AAV-Brn3b may be a suitable agent for promoting regeneration following axonal injury during glaucoma.
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