Intraocular Gene Transfer of Pigment Epithelium-Derived Factor Protects the Retina from Ischemia Reperfusion Injury by Reducing Retinal Cell Apoptosis

Abstract

Abstract: : Purpose: To determine whether intraocular gene transfer of pigment epithelium-derived factor (PEDF) protects the retina from ischemia reperfusion injury. Methods: Four days prior to induction of pressure-induced ischemia, Lewis rats received intravitreous injection of 3x10⁹ particles of adenoviral vector expressing PEDF (AdPEDF.11) in one eye and 3x10⁹ particles of empty adenoviral vector (AdNull.11) in the contralateral eye. Seven days after reperfusion the eyes were enucleated and processed for morphometric analysis. In addition, cell death in the retina was examined using TUNEL stain and propidium iodide counter-stain. Results: Eyes treated with AdNull.11 showed numerous pyknotic cells in the outer nuclear layer (ONL) and a moderate number in the inner nuclear layer (INL) and ganglion cell layer (GCL). Retinal thickness and retina cell density in the GCL, INL and ONL were reduced in eyes treated by AdNull.11 as compared to AdPEDF.11. The preservation of cell counts in eyes treated with AdPEDF.11 was statistically significant in all cell layers; GCL (p=0.014), INL (p=0.008) and ONL (p=0.008). In eyes treated with intravitreous injection of AdNull.11 there were many TUNEL-positive cells in the GCL, INL and ONL which corresponded to pyknotic cells stained by propidium iodide. There were fewer TUNEL-positive and corresponding pyknotic cells, in AdPEDF.11 treated eyes. Conclusions: Adenovirus vector mediated, intraocular expression of PEDF, significantly increases retinal cell survival in a model of ischemia-reperfusion injury. We offer evidence that the protective effect results in part from inhibition of ischemia-induced apoptosis. This study provides proof of concept for a gene transfer approach to modulating retinal cell death resulting from ischemia-reperfusion injury and may suggest that gene transfer of PEDF is broadly applicable to modulating apoptosis in the retina.

Keywords: neuroprotection • apoptosis/cell death • ischemia