Establishment of chronic ocular hypertension model by anterior chamber injection of polystyrene microspheres in mouse / 中华实验眼科杂志

ABSTRACT

Background Many methods of ocular hypertension modeling have been used before,but these models remain short-duration ocular hypertension only.A new method of elevating intraocular pressure in mice by anterior chamber injection of polystyrene microspheres was reported abroad.However,this model is rarely used in China.Objective This study was to evaluate the application value of anterior chamber injection of polystyrene microspheres to establish glaucoma model in mice.Methods Forty-two SPF adult female C57BL/6L mice were divided into three groups according to random number table.Polystyrene microspheres (2 μl) were injected into the anterior chamber monocularly in the microspheres group,and the equal amount of PBS was used in the same way in the PBS group.No intervene was performed in the normal control group.The eyes of mice were examined by slit lamp microscope,and the intraocular pressure (IOP) was measured with TonoLab rebound tomometer in a 3-day interval after injection.Ocular histological sections were prepared 2 and 4 weeks after injection,and the anterior chamber angle was examined under the optical microscope.Neurons retrograde labeling was performed by 4％ fluorogold to calculate the survival number of retinal ganglion cells (RGCs) and the nerve fiber density was detected to assess the degree of RGCs and axon damage in retinal flat mounts,and the β-Ⅲ-tubulin-positive cells in the RGCs layer were examined by immnofluorescence method.The use and care of the animals complied with the instruction of Association for Research in Vision Ophthalmology (ARVO).Results IOP was significantly higher in the mice of the microspheres group than that in the normal control group or PBS group 2 and 4 weeks (all at P＜0.05).In the microspheres group,IOP reached peak in 2 weeks after injection and was significantly higher than that of 4 weeks after injection ([29.67±2.34] mmHg versus[15.71±1.23] mmHg) (all at P＜0.05).In 2 and 4 weeks after the anterior chamber injection of polystyrene,corneal edema was found under the slit lamp microscope,and under the optical microscope,microspheres accumulated at the anterior chamber angle.Additionally,in 2 and 4 weeks after injection,the number of survival RGCs was (4 542.82 ± 653.72)/mm2 and (3 623.12 ± 628.79)/mm2,respectively in the microspheres group,which showed significantly decrease in comparison with (6 979.33 ± 678.49)/mm2 and (6963.91 ±497.29)/mm2 in the normal control group (t =17.729,28.569,both at P＜0.05) and (6 843.21 ±573.42)/mm2 and (6 937.53±465.24)/mm2in the PBS group (t =16.975,29.145,both at P＜0.05).The number of RGCs was significantly less in the fourth week compared with second week after injection (t =6.951,P＜0.05).The β-Ⅲ-tubulin positive RGCs were (4 576.36± 479.64)/mm2 and (3 712.90 ± 660.31)/mm2 in 2 and 4 weeks in the microspheres group,respectively,which were significantly decreased in comparison with (6 725.94 ± 619.42)/mm2 and (6 741.90±663.60)/mm2 of the normal control group (t =18.811,22.182,both at P ＜ 0.05) or (6 757.85 ±463.59)/mm2 and (6 773.17± 471.35)/mm2 in the PBS group (t =18.953,22.605,both at P＜0.05),and in the microspheres group,β-Ⅲ-tubulin positive cells in the fourth week were decreased than those in the second week after injection (t=7.253,P＜0.05).The neural fiber density in the microspheres group in 2 and 4 weeks after injection was (193.08 ±32.75)/mm2 and (139.O0 ±38.24)/mm2,respectively,with a significant decline in comparison with (305.57±81.21)/mm2 and (297.46±52.60)/mm2(t=8.900,16.883,both at P＜0.05) of the normal control group or (312.63±70.62)/mm2 and (269.37±61.63)/mm2 of the PBS group (t=7.731,15.959,both at P＜0.05),and the neural fiber density was significantly lower in the fourth week than that in the second week after injection (t =7.442,P＜0.05).Conclusions Single injection of polystyrene microspheres into the anterior chamber can induce chronic ocular hypertension in mouse,which leads to the progressive damage of RGCs and neural fibers.This animal model shows a similar chronic pathogenic process to human glaucomatous eye.