Complement Factor H deficiency results in decreased neuroretinal expression of Cd59a in aged mice

Purpose: The complement system is closely linked to the pathogenesis of age-related macular degeneration (AMD). Several complement genes are expressed in retinal pigment epithelium (RPE), and complement proteins accumulate in drusen. Further, a common variant of complement factor H (CFH) confers increased risk of developing AMD. Because the mechanisms by which changes in the function of CFH influence development of AMD are unclear, we examined ocular complement expression as a consequence of age in control and CFH null mutant mice. Methods: Gene expression in neuroretinas and RPE/choroid from young and aged WT and Cfh-/- C57BL/6J mice was analysed by microarrays. Expression of a wide range of complement genes was compared to expression in splenocytes and in liver tissue by qRT-PCR. Results: An age-associated increased expression of complement, particularly C1q, C3 and Factor B, in the RPE/choroid coincided with increased expression of the negative regulators Cfh and Cd59a in the neuroretina. Young mice deficient in CFH expressed Cd59a similar to WT, but failed to upregulate Cd59a expression with age. Both hepatic and splenic expression of Cd59a increased with age regardless of Cfh genotype. Conclusions: While the connection between CFH deficiency and failure to up-regulate CD59a remains unknown, these results suggest that expression of CD59 is tissue-specific and that neuroretinal regulation depends on CFH. This could contribute to the visual functional deficits and morphological changes in the Cfh-/- mouse retina that occur with age, and further suggests that deficient neuroretinal regulation of complement could represent an early event in AMD. Gene expression in neuroretinas and RPE/choroid from young and aged WT and Cfh-/- mice, 4 biological replicates in each group.研究目的：补体系统与年龄相关性黄斑变性(age-related macular degeneration, AMD)的发病机制密切相关。已有研究证实，多种补体基因在视网膜色素上皮(retinal pigment epithelium, RPE)中表达，且补体蛋白可在玻璃膜疣(drusen)中沉积。此外，补体因子H(complement factor H, CFH)的常见变异型会升高AMD的发病风险。由于CFH功能改变影响AMD发生的具体机制尚未阐明，本研究以野生型(WT)及Cfh-/- C57BL/6J小鼠为模型，探究正常与衰老状态下眼部补体系统的表达特征。实验方法：通过微阵列(microarrays)分析年轻与老年WT、Cfh-/- C57BL/6J小鼠的神经视网膜及RPE/脉络膜组织的基因表达水平；采用实时定量聚合酶链式反应(qRT-PCR)，对比多种补体基因在脾细胞与肝脏组织中的表达差异。实验结果：RPE/脉络膜中补体系统（尤其是C1q、C3及因子B）的表达随年龄增长显著上调，这一现象与神经视网膜中负调控因子Cfh及Cd59a的表达升高相吻合。CFH敲除的年轻小鼠Cd59a表达水平与WT小鼠无明显差异，但随年龄增长无法上调Cd59a的表达。无论CFH基因型如何，小鼠肝脏与脾组织中Cd59a的表达均随年龄增加而升高。研究结论：尽管CFH缺乏与Cd59a无法随年龄上调之间的关联仍不明确，但本研究结果表明，CD59的表达具有组织特异性，且神经视网膜的补体调控依赖于CFH。这一发现或可解释Cfh-/-小鼠视网膜随衰老出现的视觉功能缺陷与形态学变化，同时提示神经视网膜补体调控缺陷可能是AMD发生的早期事件。本数据集涵盖年轻与老年WT及Cfh-/-小鼠的神经视网膜、RPE/脉络膜组织的基因表达数据，每组设置4个生物学重复样本。