GDNF对视神经轴突切断后大鼠视网膜EAAT-1和GS表达的影响

The Effect of GDNF on the Expression of Retinal EAAT-1 and GS of Rats after Optic Nerve Axotomy

目的:研究玻璃体腔注射外源性胶质细胞源神经营养因子(Glial cell derived neurotrophic factor, GDNF)对视神经轴突切断(optic nerve axotomy, ONA)大鼠视网膜兴奋性氨基酸转运蛋白-1(Excitatory Amino Acid Transporter-1, EAAT-1)和谷氨酰胺合酶(Glutamine synthetase, GS)表达影响。方法:建立Sprague-Dawley (SD)大鼠单眼视神经轴突切断模型56只,并随机分为4组,各组16只SD大鼠。伤后即刻、7 d玻璃体腔内分别注射GDNF(Glial cell derived neurotrophic factor) 1 µg (实验组1)、2 µg (实验组2)、3 µg (实验组3)和0.1 M磷酸缓冲液(阴性对照组),阴性对照组大鼠的对侧眼作为正常对照组。各组于术后7 d随机选择2只大鼠上丘脑逆行标记荧光金视神经轴突切断状况。术后14 d、21 d随机选择6只实验大鼠,免疫组织化学分析视网膜EAAT-1和GS的表达。结果:视网膜神经节细胞逆行标记显示视神经夹伤后视神经轴突被完全切断。ONA后14 d、21 d,正常对照组、实验组2的EAAT-1、GS表达均高于阴性对照组;ONA后14 d,实验组3的GS表达高于阴性对照组。ONA后21 d,实验组1的EAAT-1、GS表达低于正常对照组。结论:玻璃体腔注射适当剂量的外源性GDNF能促进视神经损伤后大鼠视网膜EAAT-1、GS的表达。

Objective: To investigate the effect of exogenous Glial cell derived neurotrophic factor (GDNF) on the expression of retinal excitatory amino acid transporter-1 (EAAT-1) and glutamine synthetase (GS) of rats after optic nerve axotomy. Methods: Right unilateral optic nerve crush (ONA) model of Sprague-Dawley rats (56) was established, and divided into 4 groups randomly. Right eyes of each group were injected intravitreously 1 µg (test 1 group), 2 µg (test 2 group ), 3 µg ( test 3 group) GDNF, and 0.1 M phosphate buffered saline (negative control group) after ONA immediately. Injec-tions were repeated 7 days after ONA. The left eyes of negative control group were intact, and served as normal control group. FluoroGold was injected into the superior colliculi of 2 rats out of each group to retrogradely label retinal ganglion cells in order to examine the optic nerve axotomy. The expression of GS, EAAT-1 of each group was tested with immnohistochemisty 14 and 21 days after ONA. Results: Retinal ganglion cells axotomy were confirmed by FluoroGold retrogradely labeling. The expression of EAAT-1, GS of normal control group and test 2 group was high significantly than that of negative control group at 14, 21 days after ONA. The expression of GS of test 3 group was also high significantly than that of negative control group at 14 days after ONA. The expression of EAAT-1, GS of test 1 group was lower than that of normal control group at 21 days after ONA. Conclusion: Exogenous GDNF injected intravitreously with adequate dose can enhance the expression of EAAT-1, GS after optic nerve axotomy.