| Objectives: Nonarteritic anterior ischemic optic neuropathy(NAION)is a common optic nerve disease,and more often occurred in the elderly with serious impact on patient’s visual function.Currently in clinical practice,there is no widely agreed effective treatment by all ophthalmologists to improve the visual function of the affected eye and prevent the incidence of contralateral eye.The exact pathogenesis of NAION is not entirely clear,and most scholars believed that it is caused by the blood supplying insufficiency of ciliary posterior short arteries,and lead to optic nerve infarction which including retinal ganglion cells(RGCs)axons,and RGCs apoptosis.Recent studies have shown that inflammatory mechanism is involved in the development of NAION and play an important role in optic nerve ischemic injury,but there is still a wide-ranging controversy on whether or not corticaosteroid treatment should be used in NAION.This is partly due to the lack of ideal NAION experimental animal model which may be used to accurately evaluate the therapeutic effect of corticosteroid.In recent years,the photodynamic method for the preparation of NAION experimental animal model has made great progress,which brought the feasibility on evaluation the therapeutic effect of corticosteroid.Some foreign studies have been performed and reported,but there was larger difference between them,so their clinical reference value are limited.In this study,NAION experimental animal model was prepared by advanced photodynamic method,and was used to observe the participation characteristics of inflammatory mechanism,and gave appropriate corticosteroid intervention in order to observe the effect of corticosteroid treastment in NAION,with a view to provide the foundation and basis for clinical application.Methods: Sixty-three SD rats were divided into three groups according to the complete randomization method,21 rats in blank control group,normal saline group and dexamethasone group respectively.The blank control group was not given NAION induction and any intervention throughout the observation period.The normal saline group and dexamethasone group were induced NAION model by using the Rose Bengal(RB)solution combined with multi-wavelength laser,with selection of wavelength 532 nm,power 75 mW,spot diameter 500μm spot,continuous exposure to the upper half of the disc area 15 s.In every groups,15 rats were used to observe the changes of ED1(+)cells at 1,3,7,14 and 28 days after induction with 3 rats at each time point,and six rats were used to observe the changes of RGCs at 14 and 28 days after inducction with 3 rats at each time point.The right eyes of all experimental animals were selected as the experimental eye.After rat NAION(rNAION)was successfully induced,rats in the normal saline group were given 0.2ml normal saline every day by intraperitoneal injection,until to the observed days,up to 14 days.Rats in the dexamethasone group were given daily administration of dexamethasone sodium phosphate injection by intraperitoneal injection,0.25 mg gradually reduced to withdrawal,until to the observe days,up to 14 days.The changes of fundus fluorescein angiography(FFA),macrophages in the optic nerve and RGCs number in the blank control group,normal saline group and dexamethasone group were observed at different time points after rNAION induction.Immunohistochemistry and fluorescence observation of optic nerve slices were performed by ED1(anti-CD68)antibody identified macrophages and RGCs samples was labeled with Brn3 a antibody.Immunofluorescence microscopy and laser confocal microscopy were used to observe and photograph,and the images were analyzed by Image J image analysis software,with final statistical analysis.Results:1 FFA observation of the optic disc and surrounding retina veinThere was no abnormal fluorescence change was observed at each timepoint during the whole observation period in the blank control group.In the normal saline group,the fluorescein leakage was heavier at the 1st and 3rd day after induction,and the tortuous and expansive retinal veins was obvious.In the dexamethasone group,the fluorescein leakage was lighter at the 1st and3 rd day after induction,and the tortuous and expansive retinal vein is not obvious.In the normal saline group,there was still obvious fluorescein leakage at the 7th day after induction.In the dexamethasone group,the fluorescein leakage was not obvious at the 7th day after induction.In the normal saline group and dexamethasone group at the 14 th and 28 th day after induction,the disc showed continuous low fluorescence with varied degree,suggesting the optic nerve atrophy.2 Changes of ED1(+)cells around the lamina cribrosa area of optic nerveThere was few ED1(+)cells around the lamina cribrosa area of optic nerve in the blank control group.In normal saline group,a small amount of ED1(+)cells were seen in the antrerior lamina cribrosa area and lamina cribrosa area of optic nerve at the 1st day after induction.At the 3rd day after induction,the number of ED1(+)cells in the lamina cribrosa area was significantly increased,and there were scattered ED1(+)cells in the posterior lamina cribrosa area.At the 7th day after inducition,the number of ED1(+)cells around the lamina crobrosa area was decreased,and ED1(+)cells were found to extend to the posterior lamina cribrosa area of optic nerve.At the14 th day after induction,the number of ED1(+)cells in the lamina cribrosa area was significantly decreased,but the number of ED1(+)cells in the posterior lamina cribrosa area was relatively increased,and the distribution was relatively sparse.At the 28 th day after induction,only a few ED1(+)cells were seen in the lamina cribrosa area of optic nerve,but there were still a few ED1(+)cells in the posterior lamina cribrosa area.The change of ED1(+)cells in the dexamethasone group was the same as that of the normal saline group,but the number of ED1(+)cells in the dexamethasone group was different to that in the normal saline group at different observation time points.On the number of ED1(+)cells surrounding the lamina cribrosa area of optic nerve,there were significant difference(P<0.05)between the normal saline group,the dexamethasone group and the blank control group at the 1st day after induction;however there was no significant difference between the normal saline group and dexamethasone group(P=0.16).There were significant differences between the three groups at the 3rd,7th,14 th and 28 th day after induction(P<0.05).There were significant differences in the mean number of ED1(+)cells between the three groups during the whole observation period(P <0.05).3 Changes on the density of RGCsAt the 14 th day after induction,the RGCs density in the normal saline group and dexamethasone group were significantly lower than those in the blank control group(P <0.05),and compared with the dexamethasone group,the normal saline group was also significantly decreased(P<0.05).At the 28 th day after induction,the RGCs density in the normal saline group and dexamethasone group were significantly lower than those in the blank control group(P<0.05),and compared with the dexamethasone group,the normal saline group was also significantly decreased(P<0.05).On the RGCs density,there was no significant difference between the 14 th day and 28 th day after induction in the blank control group(P>0.05),and there were significant difference in the normal saline group and dexamethasone group(P<0.05).Conclusion: There is the participation of inflammatory mechanism in the rNAION model,and corticosteroid treatment plays a certain extent role on the reduction of inflammation,rapid elimination of optic disc edema,and inhibition of RGCs apoptosis. |
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