Microglial activation and ganglion cells damages in the rat retina with early stage streptozotocin-induced diabetes

Abstract

Objective To observe the relationship between retinal microglial activations and ganglion cell (RGC) damages in early-stage diabetic rats. Methods A total of 20 Sprague-Dawley(SD)rats were randomly divided into 4 groups (each with 5 rats): 1 month control group, 1 month diabetes group, 3 month control group, 3 month diabetes group. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). The RGCs of all rats were retrograde labeled by carbocyanine dye DiI injected at the superior colliculi. Microglial cells and RGCs in retinal flat-mounts and sections were stained immunohistochemically and recorded under confocal microscope. Results The diabetic microglial cells were amoeboid and ovoid with fewer processes on retinal flat-mounts. The density of microglial cells which phagocytosed Dil particles in the RGC layer significantly increased in the 3-month diabetes group(P<0.01). The density of microglial cells in the RGC layer significantly increased in the 1- and 3- month diabetes group (P<0. 05). However there were more microglial cells in the RGC layer in the 3-month diabetes group than the 1-month diabetes group (P < 0.0001 ). Significant correlation was found between the amount of microglial cells and that of RGCs in the early-stage of diabetes. Conclusions Microglial cell activation has close relationship with the RGC damages in early-stage diabetic rats. Key words: Diabetic retinopathy/Phisiopathology; Microglia/physiology; Retinal ganglion cells/physiology; Diabetes mellitus, experimental