To Study Retinal Ganglion Cell Damage In Rat Chronic Elevated Intraocular Pressure Model

Objective To establish a consistent long-time chronic elevated intraocular pressure glaucoma model in rat was in order to study the effects of retinal glial cell on glaucomatous retinal ganglion cell damage, and to study the mechanism of damage of selective retinal ganglion cell in glaucoma.Methods.1 .Rats were rendered elevated intraocular pressure by ligating 2 episcleral veins with subconjunctival injection 5-Fu.2.Glial cell densities were determined in flatmounted retinas or transverse semithin sections. Expression of glial fibrillary acidic protein(GFAP) was localized on frozen section or flatmounts by confocal microscopy. Microglial cells were visualized by OX42 staining on whole-mounts of retina.3.Fore weeks after operation, immuno-histological assays were carried out on cryostat sections. The co-expression of TNF-α-GFAP, TNF-α-OX42 , TNFR-1-GFAP ,and TNFR-1-NeuN were observed via a confocal laser scanning microscope respectively. 4.One week, fore weeks after operation, immuno-histological assays were carried out on whole-mounts of retina . The co-expression of GluR2 and NF-68 was observed via a confocal laser scanning microscope.Results.1.Elevated IOP was consistently maintained for up to 10 weeks in trial group. The survival rate of RGCs in operation eye was 90.16%, 83.50%, 75.01%, 62.37% of control eye at 1,4,6,10 weeks respectedly after operation.2.The activated microglial cells was appeared at 2 hour earlier than the activated Muller cells and astrocytes at 12 hours of operation compared with control group. The density of activated microglial cells was significantly increased at 1 week, but thedensity of astrocytes and Muller cells had no changes in trial group compared with control group.The actived astrocyte had structural disorder included disappeared star-structure of cell body, stiffness and shortness of cell processes.3. TNF-α and GFAP are co-expressed in actived Muller cells and astrocytes. TNF-α and OX42 are also co-expressed in actived retinal microglial cell.4. TNFR-1 and GFAP are co-expressed in actived retinal glial cells, but there are not co-expressed of TNFR-1 and NeuN in retina.5.There was no expression of GluR2 in larger ganglion cell both, but was in smaller and intermediate ganglion cell in control group. The expression of GluR2 was also absent in larger ganglion cell of lw operation rat, but was observed in larger ganglion cell of 4w operation rat. After 1w, 4w operation, smaller and intermediate ganglion cell have expression of GluR2.Conclusion.1.Microglial cells were the earliest in the retinal pathological changes of glaucoma.2. The actived astrocytes not only accelerated the damage of retina ganglion cell, butalso constructed disadvantageous microenvironment for resurrected axon of retinalganglion cell in glaucoma.3.TNF-α that actived retinal glial cells secrete may play important role inglaucomatous retinal ganglion cell damage.4.Glaucomatous selective degeneration of retinal ganglion cell was due to absenceexpression of GluR2. The sensitivity of larger retinal ganglion cell have inherentproperty in glaucoma.