Streptozotocin (STZ)-induced Diabetic Retinopathy (DR) Model Establishment
A total of 45 specific pathogen-free (SPF) grade male Sprague-Dawley (SD) rats aged 8 weeks old with an average weight of 250 - 300 g were purchased from Hunan SJA Laboratory Animal Co., Ltd. (Changsha, China). The STZ induced DR model was established according to the following methods: STZ was dissolved with 0.1 mol/L citrate buffer (PH = 4.5) and 60 mg/kg of the mixture was injected intraperitoneally into rats after 12 h of fasting. After 72 h, blood samples were taken from the tail vein and blood glucose level was measured. The model was considered as successfully established when blood glucose level exceeded 16.7 mmol/L. Rats were then grouped into the sham, STZ, and CMS + STZ groups (with 15 rats in each group). Rats in the sham group were intraperitoneally injected with an equal dose of normal saline. Rats in the CMS + STZ group were treated with CMS as follows: from the day of establishment of STZ rat model, STZ induced DR rats were injected subcutaneously with 10 mg/kg, 50 mg/kg and 100 mg/kg CMS for 8 weeks, respectively, while rats in the sham and STZ groups were injected with equal doses of normal saline. 60 d after modeling, the rats were euthanatized and bilateral eyeballs were removed to detaching retinas. Retinas were homogenized using appropriate amount of phosphate buffer solution (PBS) immediately and centrifuged at 4°C for 20 min (12,000 rpm). Then the supernatant was transferred into another 1.5 mL centrifugal tube and stored at -80°C.