Neurodegeneration in the Retina: Effect of the Glial Pigment Epithelium-Derived Factor (PEDF)

糖尿病患者的视网膜经历了血管和神经系统的慢性退行性变化，最终可能导致不可逆转的视力丧失。本项目重点研究色素上皮衍生因子(PEDF)的调节和作用，它主要存在于视网膜中，因为它是由视网膜神经胶质(Müller)细胞产生的。PEDF既是一种抗血管生成因子，又是一种神经营养/保护因子。鉴于这些活性，PEDF是防止视网膜新生血管和神经元变性的合适候选分子。为了提高我们对这些特定的PEDF固有功能的理解，需要建立转基因动物，使其能够操控米勒细胞来源的PEDF的过度表达。在迄今开展的工作中，我们开发了实现这一目标所需的适当结构。我们预计，涉及这些动物的拟议实验将阐明代谢应激暴露的神经元(和内皮细胞)的存活如何受到胶质细胞PEDF产生的调节。我们已经产生的体外数据表明，在低氧条件下，Müller细胞释放的PEDF增加，PEDF上调受HIF-1和血管内皮生长因子的控制。我们发现PEDF可以支持视网膜神经节细胞的存活(在低氧条件下，视网膜神经节细胞的存活明显减弱)；此外，它的活性还抑制了低氧诱导的Müller细胞产生血管内皮生长因子。最后，我们的研究发现了一个新的结合分子，可能是视网膜微血管内皮细胞上的PEDF受体，这表明PEDF可能干扰了PlGF和VEGF与这些细胞的结合，为其抗血管生成活性提供了新的解释。在这里，我们建议通过我们的项目中的进一步工作来研究是否短暂的低氧，随后的复氧，导致Müller细胞来源的PEDF产量的增加。最后，进一步的实验工作将致力于阐明我们鉴定的新的PEDF结合分子是否参与了刺激的视网膜内皮细胞发生的信号机制。

The retina of diabetic patients undergoes chronic degenerative changes in both the vascular and the neuronal system, which may ultimately lead to irreversible loss of vision. This project places emphasis on the regulation and effects of pigment epithelium-derived factor (PEDF), which mainly occurs in the retina due to its production by retinal glial (Müller) cells. PEDF plays important roles as an anti-angiogenic as well as a neurotrophic/ -protective factor. Given these activities, PEDF is an appropriate candidate molecule to prevent both neovascularization and neuronal degeneration in the retina. To improve our understanding of these particular PEDF-inherent functions, transgenic animals are to be generated which allow to manipulate Müller-cell derived PEDF expression towards an overexpression. In the course of hitherto performed work we have developed appropriate constructs required to accomplish this goal. We anticipate that the proposed experiments involving these animals will shed light on how survival of metabolic stress-exposed neurons (and endothelial cells) is modulated by glial PEDF production. We have generated in vitro data indicating an increased PEDF release from Müller cells under hypoxia, with a PEDF upregulation that was controlled by HIF-1 und VEGF. PEDF was shown by us to support retinal ganglion cell survival (which was markedly attenuated under hypoxia); furthermore, its activity inhibited the hypoxia-induced VEGF production by Müller cells. Finally, our studies identified a new binding molecule as a putative PEDF receptor on retinal microvascular endothelial cells which suggests that PEDF may interfere with PlGF and VEGF binding to these cells, providing a new explanation for its anti-angiogenic activity. Here we propose to investigate by further work in our project whether transient hypoxia, followed by re-oxygenation, causes an increase of Müller-cell derived PEDF production. Finally, further experimental work will be aimed at elucidating whether the novel PEDF binding molecule identified by us, is involved in signaling mechanisms occurring in stimulated retinal endothelial cells.