Desialylation as trigger of microglia responses in the aging and degenerating retina

年龄相关性视网膜变性是导致视力丧失和失明的主要原因。通常由小胶质细胞协调的慢性促炎环境是这些疾病的标志。小胶质细胞和巨噬细胞产生和释放的活性氧(ROS)和补体成分(C1q、C3)被认为与视网膜变性的进展有关。唾液酸化是控制补体系统和小胶质细胞反应的主要检查点。在人类中，唾液酸化的量随着年龄的增长而显著减少，但它与补体和小胶质细胞相关的疾病，包括年龄相关性黄斑变性(AMD)的相关性尚不清楚。在这个项目中，我们将研究减少唾液酸化对Gne+/-小鼠视网膜小胶质细胞状态的影响，并将这种表型与AMD背景下的人类视网膜衰老和退化进行比较。GNE+/-小鼠将与CX3CR1-GFP报告动物杂交，小鼠将受到急性白光照射的挑战。无创光谱域光学相干断层扫描(SD-OCT)和共聚焦扫描激光眼底镜(SLO)将被用于受控的时间分析视网膜的光感受器死亡和小胶质细胞的反应。此外，我们将分析来自AMD患者和老年对照组的人死后视网膜组织的唾液酸化状态、小胶质细胞表型和基于RNAseq的转录组。将这些对小鼠的活体分析与小鼠和人类的视网膜原位免疫组织化学和RNAseq分析相结合，将使我们能够确定唾液酸轻微丧失就会警告小胶质细胞并触发视网膜退化的关键时间点。这些实验有助于阐明在衰老过程中渴望作为小胶质细胞反应的触发因素的相关性，并可能突出这一生化途径作为年龄相关性视网膜疾病的潜在治疗靶点。

Age-dependent retinal degeneration are major causes for vision loss and blindness. A chronic pro-inflammatory environment often orchestrated by microglia is a hallmark of these diseases. Reactive oxygen species (ROS) and complement components (C1q, C3) produced and released by microglia and macrophages have been postulated to contribute to the progression of retinal degeneration. Sialylation is a major checkpoint for the control of the complement system and microglial responses. The amount of sialylation significantly reduces with aging in humans, but its relevance for complement- and microglia-associated disease including age-related macular degeneration (AMD) is unclear. In this project we will study the effect of reduced sialylation on the microglial state in the retina of Gne+/- mice and compare this phenotype to the aging and degenerating human retina in the context of AMD. Gne+/- mice will be crossed with Cx3cr1-GFP reporter animals and mice will be challenged with acute white light exposure. Non-invasive spectral domain optical coherence tomography (SD-OCT) and confocal scanning laser ophthalmoscopy (SLO) will then be used for a controlled temporal analysis of photoreceptor demise and microglia responses in the retina. In addition, we will analyze the sialylation state, microglial phenotype and RNAseq-based transcriptome of human post-mortem retinal tissue derived from AMD patients and aged controls. Combining these in vivo analyses of mice with retinal in situ immunohistochemistry and RNAseq analysis of mice and humans will enable us to define the critical time points when a slight loss of sialylation alerts microglia and triggers retinal degeneration. These experiments can aid to elucidate the relevance of desialylation as trigger of microglia responses in mice and humans during aging and may highlight this biochemical pathway as potential therapy target for age-related retinal diseases.