ABSTRACT
Background Inherited retinal degeneration,one of the major causes of blindness worldwide,comprises a large number of disorders characterized by a slow and progressive retinal degeneration.Interleukin-1 (IL-1)was recognized to be involved in inherited retinal degeneration.Whether IL-1 receptor antagonist (IL-1ra) can arrest retinal degeneration is worthy of investigation.Objective This study was to investigate the effects of IL-1ra on photoreceptor apoptosis in Royal College of Surgeons (RCS) rats.Methods The use of the animals complied with the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.The SPF RCS rats aged 9,15,16,25,30,35,40,50 and 60 postnatal days were collected,with 9 rats for each age group.Retinal sections were used for the TdT-mediated biotin-dUTP nick-end labeling (TUNEL) cell apoptosis assay.1 μl of IL-1ra (1.8 g/L) was intravitreally injected in the right eyes of 9 RCS rats aged 15 postnatal days and PBS was used in the same way in the fellow eyes.The injection procedure was repeated on the 20 th and 25 th day,respectively.The rats were sacrificed on the 30 th day and retinal sections were prepared for the TUNEL assay.The differences in the percentage of the positive cellular nuclei area among different ages of rats were compared by one-way ANOVA,and the differences in retinal layer thickness between IL-1ra injection group and PBS injection group were assessed by paired t test.Results Photoreceptor apoptosis appeared in 20-day-old RCS rats and progressed and peaked in 30 and 35-day-old rats and then reduced,showing a significant difference among rat of various age groups (F=28.020,P＜0.01).Images from TUNEL assay showed a weaker and less TUNEL staining in the IL-1ra injected eyes than the PBS injected eyes in 30-day-old rats.The total area and relative area of TUNEL positive nuclei were (223.052±153.092) μm2 and (2.206±1.531) ％ in the IL-1ra injected group,and those in PBS injected group were (1235.050±359.767) μm2 and (7.269± 1.624) ％,with a significant difference between them (t =4.370,t=3.250,P＜0.01).The cone and rod thickness was (15.324±9.035) μm in the IL-1ra injected group and (49.566±4.605)μm in the PBS injected group,showing a significant difference (t =22.674,P＜0.01).However,no significant difference was seen in the outer nuclear layer thickness between the two groups (t =0.268,P＞0.05).Conclusions IL-1 participates in the pathogenesis and development of inherited retinal degeneration of RCS rats.The use of IL-1ra might be a potential approach in the treatment of inherited retinal degeneration.