原纤维蛋白-2(FBN2)抗体玻璃体内注射对小鼠视网膜变性的影响

目的　探讨原纤维蛋白-2（fibrillin-2，FBN2）抗体玻璃体内注射对小鼠视网膜变性的影响。方法　选取18只8周龄C57BL/6J小鼠，随机分为3组:正常对照组、PBS组、FBN2抗体组，每组6只。正常组小鼠不做任何处理，PBS组小鼠双眼玻璃体内注射4 μL PBS溶液，FBN2抗体组小鼠双眼玻璃体内注射4 μL FBN2抗体（0.2 g·L^-1），每周注射1次，连续3周。利用眼底照相和视网膜电流图（ERG）分别检测3组小鼠眼底改变和视网膜功能。PAS染色法观察小鼠视网膜形态并测量眼球后极部视网膜、外核层以及内核层厚度，采用实时定量PCR和ELISA检测小鼠视网膜中FBN2 mRNA和蛋白的表达。结果　眼底照相显示:FBN2抗体组小鼠眼底出现明显渗出，黄白色似玻璃膜疣样沉积物以及色素沉着的病理改变，且随时间延长病理改变加重。ERG结果显示:每次注射后FBN2抗体组暗适应视杆细胞反应b波和暗适应混合细胞反应a波振幅均低于正常对照组和PBS组，差异均有统计学意义(均为P＜0.05)，且两者振幅在抗体注射3次后均最低，分别为(13.28±3.41)μV和(21.67±8.81)μV；在注射2次和3次后，FBN2抗体组暗适应混合细胞反应b波振幅均低于正常对照组和PBS组，差异均有统计学意义（均为P＜0.05），且该波振幅在抗体注射2次时最低为(59.12±18.00)μV；正常对照组和PBS组之间，各振幅差异均无统计学意义（均为P＞0.05）。PAS染色结果表明:FBN2抗体组视网膜厚度和外核层厚度 ［（129.33±15.38）μm、（23.39±3.93）μm］均低于正常对照组［(197.68±13.50）μm、（46.54±7.44）μm］和PBS组［（198.27±8.28）μm、（38.92±2.39）μm］，差异均有统计学意义（均为P＜0.05）；正常对照组和PBS组之间比较，差异均无统计学意义（均为P＞0.05）。ELISA检测显示:FBN2抗体组视网膜中FBN2蛋白的相对表达［(0.15±0.01）ng·mg^-1］低于正常组［(0.17±0.01）ng·mg^-1］和PBS组［(0.17±0.02）ng·mg^-1］ （均为P＜0.05）。PCR结果显示:FBN2抗体组视网膜中FBN2 mRNA的相对表达低于正对照组和PBS组。结论　玻璃体内注射FBN2抗体能够降低小鼠视网膜中FBN2蛋白的表达，引起小鼠发生视网膜变性 。

Effect of intravitreal injection of FBN2 antibody on retinal degeneration in mice

Objective To investigate the effect of intravitreal injection of fibrillin-2(FBN2)antibody on retinal degeneration in mice.Methods Eighteen 8-week-old C57BL/6J mice were randomly divided into three groups the normal control group,the PBS group,and the FBN2 antibody group,with six mice in each group.Mice in the normal group did not receive any treatment,mice in the PBS group were injected with 4μL PBS solution in binocular vitreous body,and mice in the FBN2 antibody group were injected with 4μL FBN2 antibody(0.2 g·L-1)in binocular vitreous body,once a week for 3 consecutive weeks.Fundus photography and electroretinogram(ERG)were used to detect fundus changes and retina function in the three groups of mice,respectively.PAS staining was used to observe the retinal morphology of mice and measure the thickness of retina at the posterior pole of the eyeball,outer nuclear layer and inner nuclear layer.Real-time quantitative PCR and enzyme-linked immunosorbent assay were used to detect the expression of FBN2 mRNA and protein in the retina of mice.Results Fundus photographs showed that the fundus of mice in FBN2 antibody group had obvious exudation,yellow-white vitreous film wart-like deposits,and pathological changes of pigmentation,which became worse with time.ERG results showed that the amplitude of b wave for dark-adaptive rod response and a wave for dark-adaptive mixed cell response in the FBN2 antibody group were lower than that of the normal control group and the PBS group after each injection,and the differences were statistically significant(both P<0.05),and the amplitudes of both were the lowest after three injections of antibody,(13.28±3.41)μV and(21.67±8.81)μV,respectively.After two and three times of injections,the amplitudes of b-waves for the dark-adapted mixed cell response in the FBN2 antibody group were lower than those in the normal control group and the PBS group,and the differences were statistically significant(both P<0.05).When the antibody was injected twice,the amplitudes of minimum value was(59.12±18.00)μV;there was no statistically significant difference in amplitude between the normal control group and the PBS group(all P>0.05).The PAS staining results showed that the thickness of the retina and outer nuclear layers(129.33±15.38)μm,(23.39±3.93)μm of the FBN2 antibody group were lower than those of the normal control group(197.68±13.50)μm,(46.54±7.44)μm and PBS group(198.27±8.28)μm,(38.92±2.39)μm,the differences were statistically significant(all P<0.05);there was no statistically significant difference between the normal control group and the PBS group(all P>0.05).The ELISA test showed that the relative expression of FBN2 protein in the retina of the FBN2 antibody group(0.15±0.01)ng·mg-1 was lower than that in the normal group(0.17±0.01)ng·mg-1 and PBS group(0.17±0.02)ng·mg-1(both P<0.05).The PCR results showed that the relative expression of FBN2 mRNA in the retina of the FBN2 antibody group was lower than that of the positive control group and the PBS group.Conclusion Intravitreal injection of FBN2 antibody can reduce the expression of FBN2 protein in the retina of mice and cause retinal degeneration in mice.