Abstract
Abstract: :
Purpose: Glaucoma pathology involves the death of retinal ganglion cells and degeneration of the optic nerve head. We investigated changes in mRNA levels in the rat retina after experimentally-induced optic nerve and retinal damage. Methods: Degeneration of the retinal ganglion cell layer and optic nerve head was induced unilaterally either by hypertonic saline solution injection into the episcleral vein, or by optic nerve transection. After episcleral vein injection, intraocular pressure (IOP) was measured daily in awake animals. Rats were sacrificed 6 weeks after surgery, and the degree of optic nerve damage was estimated. Total RNA was extracted from control and experimental retinas and used for cDNA and cRNA synthesis. Complimentary RNA was hybridized to Affymetrix rat U34A arrays, and the results were analyzed using Affymetrix version 4.0 software. The observed differences in mRNA levels were confirmed by semi-quantitative RT-PCR. Results: After experimental elevation of intraocular pressure, 66 genes out of 8,000 present on the array, consistently changed their expression pattern. Sixty-one of these genes were up-regulated, and only 5 genes were down-regulated. More than 50% of the identified genes have been previously implicated in cell death, inflammation, and stress responses. Thirty-five identified genes were selected for confirmation by semi-quantitative RT-PCR and for analysis of their expression during optic nerve transection-induced retinal degeneration. Changes in expression detected by array hybridization were confirmed by semi-quantitative RT-PCR in all cases. With one exception, similar changes in mRNA levels detected after elevation of IOP were also observed after optic nerve transection. Conclusion: Similar molecular pathways may be involved in retinal degeneration, induced by both elevated IOP or by the optic nerve transection. Elevated IOP may stimulate genes normally associated with inflammation and the immune response.
Keywords: 316 animal model • 417 gene/expression • 554 retina