Microarray expression analysis of the N-methyl-N-nitrosourea-induced retinal degeneration in rat / 中华实验眼科杂志

ABSTRACT

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.