Retinal Ganglion Cells Protective Effect Of Astragalus Polysaccharides In Ocular Hypertension Rat Model

Objective: Glaucoma,one of the worlds leading causes of blindness,is characterizedby the atrophy of optic disc and characteristic defect of visual field. Pathogenesis ofglaucoma, optic atrophy is not very clear, there are two theories: the theory ofmechanical pressure and vascular ischemia theory traditionally.Mechanical pressure onthe theory that the intraocular pressure in the sieve compression of the optic nerve fibers,hindering the transport of axoplasmic flow, reduce the formation of axonal protein andmobile, resulting in impaired cell metabolism. Vascular ischemia theory emphasizes theoptic nerve fiber damage due to ischemia and hypoxia and loss of the protection of thesurrounding tissue.That mechanical pressure and blood supply to participate in theglaucoma damage to the optic nerve, intraocular pressure increased, further increasingthe self-mechanism of the retinal nerve vascular dysregulation contributed to thedamage of the optic nerve. Prevent optic nerve damage, protect visual function mainlythrough drugs and surgery to reduce intraocular pressure (IOP), in order to reduce thepressure on the optic nerve damage, and significant results, this approach has been aconsensus. However, simply lowering the intraocular pressure and can not completelystop the glaucomatous optic nerve damage. There are still things visual field and opticnerve of the proportion of patients continues to be damaged.Therefore, there is growingconcern to strengthen the treatment of optic nerve protection, to find a drug that canprotect the optic nerve, blocking and/or delay the ganglion cells of primary orsecondary injury has become the focus of glaucoma research today and hotspots.Retinal ganglion cell apoptosis is a highly regulated cell death is the final pathwayof glaucomatous optic nerve damage. In this study, through the production of highintraocular pressure rat model to investigate the protective effects of Astragaluspolysaccharides on the retinal ganglion cells in rats with acute ocular hypertension, which reveals some herbs with the effect of blood circulation in the microcirculation,and improve the antioxidant capacity, improve the glaucomatous optic axis plasma flowhas a significant effect, experimental and theoretical basis for the treatment of clinicaloptic nerve protection.Methods:60female SD rats supplied by Dalian Medical University ExperimentalAnimal Center were randomly divided into four groups, normal group (C), highintraocular pressure model control group (M), low concentrations of astragaluspolysaccharides treatment group (N), high concentrations of polysaccharide treatmentgroup (H group), each15respectively. Rats in each group daily treatments as follows: Cand M groups intragastric administration with2.5ml normal saline, Astragaluspolysaccharide500mg/kg2.5ml instead of saline was used in N group, while2000mg/kg2.5ml in H group. Two weeks later, established acute ocular hypertensionmodel except for the normal group by anterior chamber injected with methyl celluloseproduction. The model rats were confirmed on the fifth day by tonometer and sacrificedby excessive anesthesia and followed by eye ball enucleating. After4%PFA fixation,the paraffin sections were made. Compared retinal morphology by HE staining.Furthermore, immunohistochemistry assay detect caspase-3expression, TUNELstaining to evaluate apoptosis. To measure retinal thickness and nerve fiber layerthickness and count the positive staining cells by Image Pro Plus5.1software. Finally,calculate the percentage of positive staining of ganglion cells. The data was analyzed bySPSS16.0statistical package for the single-factor analysis of variance (ANOVA)between groups and pair wise comparisons were statistically analyzed using t tests, P<0.05for a significant difference.Results：Group C rat retina demonstrate a clear organizational structure, RGCsdense arrangement, clear boundary nuclei, minimal caspase-3expression. M groupretina and nerve fiber layer show a dramatic edema, loose RGCs, swelling nucleus,large caspase-3expression in retinal ganglion cell layer. N group retina structure isrelative clear. Ganglion cells are neat and dense. Notably, caspase-3expression in theretinal ganglion cell layer are significantly reduced compared to M group (P <0.001). Hgroup retinal internal and external granular layer cell matrix are still edema, nerve fiberlayer thickness had no significant improvement compared to M group(P>0.05). Thereis significant difference between group H and M in caspase-3positive cells and RGCsapoptosis ratio (P <0.05, P <0.001).Conclusion:1、High intraocular pressure can lead to retinal ganglion cell apoptosis. 2、appropriate concentration of the APS has a significant protective effect on retinalganglion cells.3、High concentrations of the APS could partially rescue the apoptosis of retinalganglion cells, but there are still some toxic effects.