Centre for Vision and Vascular Science, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, Northern Ireland, UK.
PLoS One. 2013 Apr 18;8(4):e61381. doi: 10.1371/journal.pone.0061381. Print 2013.
Previous studies have shown that CCL2/CX3CR1 deficient mice on C57BL/6N background (with rd8 mutation) have an early onset (6 weeks) of spontaneous retinal degeneration. In this study, we generated CCL2(-/-)CX3CR1(GFP/GFP) mice on the C57BL/6J background. Retinal degeneration was not detected in CCL2(-/-)CX3CR1(GFP/GFP) mice younger than 6 months. Patches of whitish/yellowish fundus lesions were observed in 17∼60% of 12-month, and 30∼100% of 18-month CCL2(-/-)CX3CR1(GFP/GFP) mice. Fluorescein angiography revealed no choroidal neovascularisation in these mice. Patches of retinal pigment epithelium (RPE) and photoreceptor damage were detected in 30% and 50% of 12- and 18-month CCL2(-/-)CX3CR1(GFP/GFP) mice respectively, but not in wild-type mice. All CCL2(-/-)CX3CR1(GFP/GFP) mice exposed to extra-light (∼800lux, 6 h/day, 6 months) developed patches of retinal atrophy, and only 20-25% of WT mice which underwent the same light treatment developed atrophic lesions. In addition, synaptophysin expression was detected in the outer nucler layer (ONL) of area related to photoreceptor loss in CCL2(-/-)CX3CR1(GFP/GFP) mice. Markedly increased rhodopsin but reduced cone arrestin expression was observed in retinal outer layers in aged CCL2(-/-)CX3CR1(GFP/GFP) mice. GABA expression was reduced in the inner retina of aged CCL2(-/-)CX3CR1(GFP/GFP) mice. Significantly increased Müller glial and microglial activation was observed in CCL2(-/-)CX3CR1(GFP/GFP) mice compared to age-matched WT mice. Macrophages from CCL2(-/-)CX3CR1(GFP/GFP) mice were less phagocytic, but expressed higher levels of iNOS, IL-1β, IL-12 and TNF-α under hypoxia conditions. Our results suggest that the deletions of CCL2 and CX3CR1 predispose mice to age- and light-mediated retinal damage. The CCL2/CX3CR1 deficient mouse may thus serve as a model for age-related atrophic degeneration of the RPE, including the dry type of macular degeneration, geographic atrophy.
先前的研究表明，CCL2/CX3CR1 缺陷型小鼠（带有 rd8 突变）在 C57BL/6N 背景下会出现自发性视网膜变性的早期发病（6 周）。在本研究中，我们在 C57BL/6J 背景下生成了 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠。在 6 个月以下的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠中未检测到视网膜变性。在 12 个月时，17∼60%的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠和 18 个月时 30∼100%的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠中观察到灰白色/黄色眼底病变斑块。这些小鼠的荧光素血管造影未显示脉络膜新生血管形成。在 30%和 50%的 12 个月和 18 个月的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠中分别检测到视网膜色素上皮 (RPE) 和光感受器损伤斑块，但在野生型小鼠中未检测到。所有暴露于强光（约 800lux，每天 6 小时，持续 6 个月）的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠均出现视网膜萎缩斑块，而仅接受相同光处理的 20-25%WT 小鼠出现萎缩性病变。此外，在 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠中与光感受器丧失相关的区域的外核层（ONL）中检测到突触小体蛋白表达。在年龄较大的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠的视网膜外层中观察到视紫红质显著增加，但视锥细胞 arrestin 减少。在年龄较大的 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠的视网膜内层中 GABA 表达减少。与年龄匹配的 WT 小鼠相比，CCL2(-/-)CX3CR1(GFP/GFP) 小鼠中观察到明显的 Müller 胶质细胞和小胶质细胞激活。与 CCL2(-/-)CX3CR1(GFP/GFP) 小鼠相比，巨噬细胞的吞噬作用降低，但在缺氧条件下表达更高水平的 iNOS、IL-1β、IL-12 和 TNF-α。我们的结果表明，CCL2 和 CX3CR1 的缺失使小鼠易发生年龄和光介导的视网膜损伤。CCL2/CX3CR1 缺陷型小鼠可能因此成为与年龄相关的 RPE 萎缩性变性（包括干性黄斑变性、地图状萎缩）的模型。
