Abstract
Abstract: :
Purpose: To determine whether early diabetes induces retinal ganglion cell (RGC) apoptosis and inhibits neurite regeneration in streptozotocin (STZ)–induced diabetic rats. Methods: Four of seven rats were injected with STZ (55 mg/kg body weight) into the tail vein to induce diabetes. Glucose concentration in blood and urine was checked to confirm diabetes status in the animals. After 3 weeks of diabetes, retinas were isolated and retinal explants were cultured in serum–free medium. After six days in culture, the number of neurites was counted in explants obtained from control and diabetic rat retinas. To identify neuronal cells undergoing apoptosis, retinas were fixed, cryosections prepared, and TdT–dUTP terminal nick–end labeling (TUNEL) staining performed. Furthermore, the expression of Bax, a proapoptotic factor, was determined by immunohistochemistry and co–staining with rabbit anti–Bax (P–19) antibody and 4, 6–diamidino–2–phenyl–indole (DAPI) in these sections. Also, Western blot analysis for Bax expression was performed with total protein extracted from the rat retinas. Results: In the diabetic rats, TUNEL and Bax positive cells were increased in the retinal ganglion cell layer compared to those of control rats, (22.7 ± 13.4 vs 33.2 ± 8.5; p = 0.0256, 19.6 ± 7.5 vs 28.4 ± 7.0; p = 0.0389). Furthermore, the number of regenerating neurites from diabetic retinas was decreased compared to control retinas (19.3 ± 12.6 vs 13.4 ± 12.7; p = 0.0441). Western blot analysis of Bax protein level in diabetic retinas showed increased level (189.5% of control) compared to the control retinas. Conclusions: Diabetes accelerates retinal neuronal cell death and reduces the number of regenerating neurites in rat retinas. Bax dependent pathways may be activated in neuronal cell death in diabetic rat retinas.
Keywords: diabetes • apoptosis/cell death • diabetic retinopathy