背景 N-甲基-N-亚硝基脲(MNU)诱导的大鼠光感受器细胞凋亡可用于研究视网膜变性类疾病,但视网膜变性类疾病早期基因水平的研究尚未见报道. 目的 应用基因芯片技术研究MNU诱导的视网膜变性大鼠早期基因表达谱的变化.方法 6周龄雌性SD大鼠50只分为正常组20只、12h模型组20只和24 h模型组10只.模型组大鼠皮下注射MNU(40 mg/kg),正常组大鼠皮下注射等容量的生理盐水作为对照.分别于造模后12、12、24 h处死正常组和12h模型组、24 h模型组大鼠,大鼠右眼球进行常规视网膜组织病理学检查,正常组和12h模型组大鼠左眼的新鲜视网膜用基因芯片技术检测差异基因的表达,用荧光实时定量PCR(real-time PCR)法验证基因芯片技术检测出的差异表达率≥2.0的基因mRNA表达水平. 结果 全层视网膜厚度测量表明,24 h模型组大鼠的厚度值明显低于正常组大鼠和12h模型组大鼠,差异均有统计学意义(t=9.926,P=0.002;t2.736,P=0.028).24 h模型组大鼠外核层厚度值为(26.58±2.90) μm,明显低于正常组的(38.11±1.01)μm和12h模型组的(35.07±3.03) μm,差异均有统计学意义(t=6.028,P=0.009;t=6.839,P=0.006),正常组与12h模型组间大鼠全层视网膜厚度和外核层厚度值比较差异均无统计学意义(全层厚度:t=1.541,P=0.324;外核层厚度:t=2.040,P=0.134).大鼠cDNA基因芯片技术检测结果表明,12h模型组大鼠全部17 000个基因的表达谱中涉及生物过程的基因为142个,涉及分子功能的基因为94个,排除重复基因共有74个基因,差异表达基因主要涉及丝裂原活化蛋白激酶(MAPK)通路、Toll样受体通路和细胞凋亡通路.对基因芯片技术检测的差异表达率≥2.0的基因进行的real-time PCR定量分析表明,CCL2、IL-1b、CCL3、c-fos、c-myc、p53和MMP3基因mRNA表达值与基因芯片技术检测的表达趋势一致. 结论 MNU诱导的视网膜变性早期有明显的基因表达改变.基因芯片检测的基因表达改变结果与real-time PCR定量分析结果一致.%Background The rat model of N-methyl-N-nitrosourea (MNU)-induced photoreceptor cell apoptosis is often used to study retinal degeneration.But the changes in the gene expression patterm in retinal degeneration in rats have not been reported.Objective This study was undertaken to investigate regulation of gene expression in the retina of MNU-induced retinal degeneration in rats by performing microarray analysis of retinal RNA.Methods Fifty 6-week-old SD rats were numbered and randomized into the normal group and the model group.The retinal degeneration model was established by a single hypodermic injection of 40 mg/kg of MNU,and the rats in the normal group received equivalent volume of physiological saline in the same way.The rats were sacrificed 12 hours or 24 hours after injection.Retinal sections from the right eyes were prepared for the measurement of the retinal thickness by histopathological examination,and retinas from the left eyes were used to confirm the differential gene expression as detected by microarray (normal group and 12 hours model group).Genes exhibiting changes in expression by ≥2.0 folds were further confirmed using real-time PCR.Results The whole thickness of the retina declined in the rats from the 24 hours model group compared to the normal group and 12 hours model group (t =9.926,P=0.002;t=2.736,P=0.028).The thickness of the outer nuclear layer was (26.58±2.90) μm in the 24 hours model group,showing a significant decrease in comparison with (38.11 ± 1.01) μm in the normal group and (35.07t3.03) μm in the 12 hours model group (t=6.028,P=0.009;t=6.839,P=0.006).However,there was no significant difference in retinal thickness between the normal group and the 12 hours model group (whole thickness:t=1.541,P=0.324;outer nuclear layer thickness:t=2.040,P=0.134).Microarray analysis of the rat genes showed that out of 17 000 genes,142 genes involved in biological process and 94 genes involved in molecular functions were differentially expressed,where most of them participate in the mitogen activated protein kinase signaling pathway,Tolllike receptor signaling pathway and apoptosis pathway.Real-time PCR analysis demonstrated that the expression of CCL2,IL-1b,CCL3,c-fos,c-myc,p53 and MMP3 were consistently up-regulated,conforming with the results from microarray analysis.Conclusions The changes in gene expression pattern appear in the early stage of MNUinduced retinal degeneration.These microarray results provided clues to understanding the molecular pathways underlying photoreceptor degeneration and indicating the directions for future studies.
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