Huang Hu, Liu Ying, Wang Lei, Li Wen
The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
Aier Eye Hospital of Changsha, Hunan, China.
PLoS One. 2017 Mar 10;12(3):e0173716. doi: 10.1371/journal.pone.0173716. eCollection 2017.
The role of chemokine receptor in age-related macular degeneration (AMD) remains elusive. The objective of this study is to investigate the role of chemokine receptor Cxcr5 in the pathogenesis of AMD. Cxcr5 gene expression levels (mRNA and protein) are higher in the retina and retinal pigment epithelium (RPE) of aged C57BL/6 wild type mice than younger ones. Vascular and glial cells express Cxcr5 and its ligand Cxcl13 in mouse retina. Aged Cxcr5 knockout (-/-) mice develop both early and late AMD-like pathological features. White and yellow spots, which look like drusen in humans, were identified with fundscopic examination. Drusen-like sub-RPE deposits with dome-shaped morphology were characterized on the sections. RPE vacuolization, swelling, and sub-RPE basal deposits were illustrated with light and transmission electron microscope (TEM). TEM further illustrated degenerated and disorganized RPE basal infoldings, phagosomes and melanosomes inside RPE, as well as abnormal photoreceptor outer segments. Lipofuscin granules and lipid droplets in the subretinal space, RPE, and choroid were revealed with fluorescence microscope and oil-red-O staining. Increased IgG in RPE/choroid were determined with Western blots (WB). WB and immunofluorescence staining determined RPE zona occuldens (ZO)-1 protein reduction and abnormal subcellular localization. TUNEL staining, outer nuclear layer (ONL) measurement and electroretinogram (ERG) recording indicated that photoreceptors underwent apoptosis, degeneration, and functional impairment. Additionally, spontaneous neovascularization (NV)-like lesions develop in the subretinal space of aged Cxcr5-/- mice. The underlying mechanisms are associated with increased subretinal F4/80+ immune cells, some of which contain RPE marker RPE65, and up-regulation of the multifunctional cytokine tumor necrosis factor-alpha (TNF-α) in RPE/choroid and retina. These findings suggest that Cxcr5 itself may be involved in the protection of RPE and retinal cells during aging and its loss may lead to AMD-like pathological changes in aged mice.
趋化因子受体在年龄相关性黄斑变性(AMD)中的作用仍不清楚。本研究的目的是探讨趋化因子受体Cxcr5在AMD发病机制中的作用。老年C57BL/6野生型小鼠视网膜和视网膜色素上皮(RPE)中的Cxcr5基因表达水平(mRNA和蛋白质)高于年轻小鼠。血管和神经胶质细胞在小鼠视网膜中表达Cxcr5及其配体Cxcl13。老年Cxcr5基因敲除(-/-)小鼠出现早期和晚期AMD样病理特征。通过眼底检查发现了白色和黄色斑点,类似于人类的玻璃膜疣。在切片上对具有圆顶状形态的玻璃膜疣样RPE下沉积物进行了特征描述。用光镜和透射电子显微镜(TEM)显示了RPE空泡化、肿胀和RPE下基底沉积物。TEM进一步显示了RPE基底褶皱退化和紊乱、RPE内的吞噬体和黑素体,以及异常的光感受器外段。用荧光显微镜和油红O染色显示视网膜下间隙、RPE和脉络膜中的脂褐素颗粒和脂滴。用蛋白质免疫印迹法(WB)测定RPE/脉络膜中IgG增加。WB和免疫荧光染色确定RPE紧密连接(ZO)-1蛋白减少和亚细胞定位异常。TUNEL染色、外核层(ONL)测量和视网膜电图(ERG)记录表明光感受器发生凋亡、退化和功能损害。此外,老年Cxcr5-/-小鼠的视网膜下间隙出现自发性新生血管(NV)样病变。其潜在机制与视网膜下F4/80+免疫细胞增加有关,其中一些细胞含有RPE标记物RPE65,以及RPE/脉络膜和视网膜中多功能细胞因子肿瘤坏死因子-α(TNF-α)的上调。这些发现表明,Cxcr5本身可能在衰老过程中参与对RPE和视网膜细胞的保护,其缺失可能导致老年小鼠出现AMD样病理变化。