目的：观察C57BL/6N(Crb1^rd8/rd8)小鼠早期视网膜变性以及小胶质细胞的活化情况。

方法：取雄性SPF级C57BL/6N小鼠15只、C57BL/6J小鼠15只，正常饲养。分别在入组时，入组4、8、12 wk，使用Micron-Ⅲ小动物视网膜影像系统进行双眼彩色眼底照相检查计算病变数量、病变面积。观察结束后处死小鼠，摘取右侧眼球制备视网膜组织切片，进行HE染色后光镜下观察视网膜组织形态； 采用免疫组织化学染色分析两组小鼠视网膜CX3CR1的表达水平及位置。摘取左侧眼球分离视网膜，使用Western-Blot检测CD86、CD206的表达情况，使用电化学发光法测定视网膜中IL-1β、IL-6、TNF-α、IL-4、IL-10炎性因子含量水平。

结果：眼底彩照结果显示在入组4、8、12 wk，C57BL/6N组眼底病变数量均较入组时显著增加，与C57BL/6J组同时间点变化量比较均有差异(均P<0.05)； 眼底病变面积变化量两组间入组12 wk有差异(P<0.05)，各组内变化量比较均无差异(均P>0.05)； 视网膜组织HE染色示：C57BL/6N组视网膜结构异常，细胞排列疏松、紊乱，光感受器层向视网膜内侧明显的玻璃膜疣样凸起，C57BL/6J组视网膜结构清晰，细胞排列有序，无明显异常； 免疫组化结果示：C57BL/6N组视网膜中CX3CR1高表达于神经节细胞层、内外丛状层、感光细胞层及病灶处位置，平均光密度为0.285±0.056，C57BL/6J组为0.189±0.084(P<0.05)； Western-Blot结果显示：与C57BL/6J组相比，C57BL/6N组视网膜CD86、CD206蛋白有不同程度升高，两组CD86蛋白表达有差异(P<0.05)； 细胞因子检测结果显示：C57BL/6N组IL-1β、TNF-α水平显著高于C57BL/6J组，而IL-10含量则明显较低(均P<0.05)。

结论：C57BL/6N(Crb1^rd8/rd8)小鼠视网膜变性进展缓慢，随年龄呈进行性加重，病灶部位视网膜结构紊乱，伴有以M1型极化为主的小胶质细胞浸润。

METHODS:Totally 15 male SPF C57BL/6N mice and 15 male SPF C57BL/6J mice were raised normally, and fundus photography examinations were performed by Micron-Ⅲ at the time of 0, 4, 8, 12 wk of enrollment to calculate the number and area of retinopathy. At the end of experiment, all mice were sacrificed and the right eyeballs were removed to prepare retinal tissue slices. After HE staining, the retinal tissue morphology was observed under optical microscope while the location and level of CX3CR1 expression were detected in immunohistochemical staining. The left eyeballs were removed to isolate retina, then Western-Blot was used to analyze the expression of CD86 and CD206 proteins in retina, and the concentration of IL-1β, IL-6, TNF-α, IL-4 and IL-10 in retina was detected by electrochemiluminescence.

RESULTS:The result of fundus photography examinations showed that the number of retinopathy in the C57BL/6N significantly increased at 4, 8, and 12 wk, and there were differences in variations compared with the C57BL/6J at the same time point(all P<0.05). In the changes in area of retinopathy, there was a difference between two groups at 12 wk(P<0.05), but no difference in variations within groups(both P>0.05). HE staining of retinal tissue showed that the retinal structure of C57BL/6N mice was abnormal, with loose and disordered cell arrangement, and the photoreceptor layer was obviously protruding to the inner side of retina with a drusen-like protrusion. The retinal structure of C57BL/6J mice was clearer, with orderly cell arrangement and no obvious abnormality. Immunohistochemical results showed that CX3CR1 was highly expressed in ganglion cell layer, inner and outer plexiform layer, photoreceptor cell layer and lesion in the retina of C57BL/6N mice, with a mean density of 0.285±0.056 in C57BL/6N and 0.189±0.084 in C57BL/6J mice(P<0.05). The results of Western-Blot showed that the expression of CD86 and CD206 in retina of C57BL/6N increased compared with that in C57BL/6J to varying degrees, and the difference of CD86 was statistically significant(P<0.05). The results of cytokine detection showed that the level of IL-1β, TNF-α in C57BL/6N was significantly higher than that of C57BL/6J, while IL-10 was significantly lower(all P<0.05).

CONCLUSION: The retinal degeneration of C57BL/6N(Crb1^rd8/rd8)mice progressed slowly and gradually aggravated with age. The retinal structure of the lesion was disordered and accompanied by microglial infiltration dominated by M1 polarization.