Selection of two types of rat strains for easily diabetic retinopathy

Abstract

Background Streptozotocin (STZ)-induced type 1 diabetic model is an acceptable model and is often used to the study of diabetic retinopathy (DR).However,the model is often established using retinal digest preparation in vitro in albino rats,and therefore it is difficult to evaluate the change of retinal vessels by fundus fluorescein angiography (FFA) in vivo.Recently,pigmented rats are being used as the DR model.But the study on the comparison between albino rat model and pigmented rat model is seldom.Objective This study was to observe and compare the manifestations of FFA and retinal digest preparation in early diabetic pigmented diabetic rat and albino diabetic rat,and to select the right model of DR using FFA.Methods Type 1 diabetic models were induced in 15 six-week-old health male BN rats and 15 six-week-old health male SD rats by the injection of STZ (55 mg/kg) via tail vein.The models were thought to be successful in the rats with the blood glucose level ≥ 16.7 mmol/L.The right eyes of the rats were extracted 6 weeks after injection of STZ.Lens were examined by slit lamp microscope.Retinal vascular changes were examined by fundus photography,FFA and periodic acid Schiff staining of retinal digest preparation.The manifestations of FFA and retinal digest preparation were contrasted between BN rats and SD rats.The number of eyes with lens opacification was compared by Chi-square test and the ratio of vascular endothelial cells and perithelial cells (E/P) was compared between BN rats and SD rats.The use and care of experimental animals complied the Statement of Ethic Committee of Tianjin Medicine University.Results Six weeks after injection of STZ,11 BN rats and 10SD rats were included in this study.The blood levels were (24.73±2.98) mmol/L and (22.36±3.65) mmol/L in BN rats and SD rats,respectively,without significant difference between the 2 types of rats (t =7.873,P＞0.05).Lens opacification occurred in 6 BN rats and in 5 SD rats (P=0.717).FFA showed the clear retinal vascular under the brown background.Evident vessel disorder and fluorescence leakage like background stage of DR were seen in 9 eyes.However,in the SD rats,retinal vessel abnormality could not exhibited owing to the interference of choroid fluorescent light from choroidal vessels and vortex vein.Retinal digest preparation exhibited that unevenness of vessel diameter,decrease of perithelial cells and increase of endothelial cells in both types of rats.The E/P values were 11.50±3.68in the BN rats and 12.86±3.94 in the SD rats,without significant difference between them (t=9.785,P＞0.05).Conclusions The abnormality of fundus vascular morphology can be better displayed in pigmented diabetic rats than albino rats by FFA in vivo. Key words: Diabetic retinopathy; Fundus fluorescein angiography; Animal model; Rat strain/ Brown-Norway rat, Sprague-Dawley rat; pigment