Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
Neuroscience Center Zurich (ZNZ), University of Zurich, Zurich, Switzerland.
Mol Neurodegener. 2018 Mar 7;13(1):12. doi: 10.1186/s13024-018-0243-y.
Degeneration of cone photoreceptors leads to loss of vision in patients suffering from age-related macular degeneration (AMD) and other cone dystrophies. Evidence, such as choroidal ischemia and decreased choroidal blood flow, implicates reduced tissue oxygenation in AMD pathology and suggests a role of the cellular response to hypoxia in disease onset and progression. Such a chronic hypoxic situation may promote several cellular responses including stabilization of hypoxia-inducible factors (HIFs).
To investigate the consequence of a chronic activation of the molecular response to hypoxia in cones, von Hippel Lindau protein (VHL) was specifically ablated in cones of the all-cone R91W;Nrl mouse. Retinal function and morphology was evaluated by ERG and light microscopy, while differential gene expression was tested by real-time PCR. Retinal vasculature was analyzed by immunostainings and fluorescein angiography. Two-way ANOVA with Šídák's multiple comparison test was performed for statistical analysis.
Cone-specific ablation of Vhl resulted in stabilization and activation of hypoxia-inducible factor 1A (HIF1A) which led to increased expression of genes associated with hypoxia and retinal stress. Our data demonstrate severe cone degeneration and pathologic vessel growth, features that are central to AMD pathology. Subretinal neovascularization was accompanied by vascular leakage and infiltration of microglia cells. Interestingly, we observed increased expression of tissue inhibitor of metalloproteinase 3 (Timp3) during the aging process, a gene associated with AMD and Bruch's membrane integrity. Additional deletion of Hif1a protected cone cells, prevented pathological vessel growth and preserved vision.
Our data provide evidence for a HIF1A-mediated mechanism leading to pathological vessel growth and cone degeneration in response to a chronic hypoxia-like situation. Consequently, our results identify HIF1A as a potential therapeutic target to rescue hypoxia-related vision loss in patients.
视锥细胞的变性导致年龄相关性黄斑变性（AMD）和其他视锥营养不良患者视力丧失。证据表明，脉络膜缺血和脉络膜血流减少，暗示 AMD 病理中的组织缺氧，并表明细胞对缺氧的反应在疾病发病和进展中起作用。这种慢性缺氧情况可能会促进几种细胞反应，包括缺氧诱导因子（HIFs）的稳定。
为了研究视锥细胞中对缺氧的分子反应的慢性激活的后果，专门在全视锥 R91W；Nrl 小鼠的视锥细胞中敲除了 von Hippel Lindau 蛋白（VHL）。通过 ERG 和光镜评估视网膜功能和形态，通过实时 PCR 测试差异基因表达。通过免疫染色和荧光血管造影分析视网膜血管。使用双向 ANOVA 进行统计分析，并采用 Šídák 的多重比较检验。
Vhl 特异性敲除导致缺氧诱导因子 1A（HIF1A）的稳定和激活，从而导致与缺氧和视网膜应激相关的基因表达增加。我们的数据表明严重的视锥细胞变性和病理性血管生长，这些是 AMD 病理的核心特征。脉络膜新生血管伴有血管渗漏和小胶质细胞浸润。有趣的是，我们在衰老过程中观察到组织金属蛋白酶抑制剂 3（Timp3）的表达增加，该基因与 AMD 和 Bruch 膜完整性有关。Hif1a 的额外缺失可保护视锥细胞，防止病理性血管生长并维持视力。
我们的数据为 HIF1A 介导的机制提供了证据，该机制导致慢性缺氧样情况下病理性血管生长和视锥细胞变性。因此，我们的结果表明 HIF1A 是一种潜在的治疗靶点，可以挽救与缺氧相关的患者视力丧失。
