Abstract:  Objective  To assess the expression of GFAP, GLAST, GS and NT-3 in Müller cells and the apoptosis of retinal nerve cells in rats with diabetes mellitus (DM) and to discuss the mechanisms of retinal nerve cell injury in DM rats. Design Experimental study. Paticipants 82 Sprague-Dawley (SD) rats. Methods  Diabetic model in rats was induced by streptozotocin method. The rats are randomly divided into 2 groups: model group and normal group. The expression of GFAPmRNA in retina was measured by RT-PCR. LSAB method was used to measured the expression level of GFAP, GLAST, GS, NT-3 in retinal Müller cells. Apoptosis of retinal nerve cells was measured by TUNEL assay and apoptosis cells were counted. Immunological histochemistry assay was used for quantitative analysis. Main Outcome Measures The expression of GFAP, CLAST, GS, and NT-3; the number of apoptotic cells in inner nuclear layer and RGC layer. Results Compared with normal group (1.00±0.02), the positive expression of GFAP in the retina of diabetic rats (5.22±1.34) was increased significantly(P=0.000). The positive apoptotic retinal cells were only expressed in RGCs and inner nuclear layer. The numbers of apoptotic cells in RGCs and inner nuclear layer of diabetic rats (36.00±6.02 and 11.48±2.08) were significantly higher than that of normal group (16.33±2.34 and 5.34±0.52) (all P=0.000). Compared with normal group (0.29±0.08), the expression of GFAPmRNA in the retina of diabetic rats （7.00±0.37） was enhanced significantly (P=0.000). The number of apoptotic RGCs and cells in inner nuclear layer was correlated positively with the positive expression level of GFAP （r=0.88, 0.85, P=0.021, 0.028）, and was negatively correlated with the expression of GLAST, GS and NT-3 （r=-0.74~-0.93, -0.71~-0.90; all P<0.05）. Conclusion  The number of apoptosis of retinal nerve cell is closely related to the active proliferation of glial reactive state in retinal Müller cells and the deficiency of neurotrophic factors. The  excitotoxicity of high concentrations of glutamate and the deficiency of neurotrophic factors are important mechanism of retinal nerve cell injury in diabetes.

Key words: Müller cells, retinal ganglion cells, glutamate-aspartate transporters, glutamine synthetase, glial fibrillary acidic protein, apoptosis, diabetes mellitus