Neuronal damage and impaired vision in different retinal disorders are induced, among other factors, by ischemia/reperfusion (I/R). Since the mechanisms and the progression of ischemic injury are still not completely clarified, a timeline of this retinal degeneration is needed. In this study, we investigated protein and mRNA alterations at 2, 6, 12, and 24 h as well as 3 and 7 days after ischemia to determine the course of an ischemic insult through the whole retina. Moreover, functional analyses were performed at later stages. We detected a significant functional loss of cells in the inner nuclear layer and photoreceptors at 3 and 7 days. Additionally, the thickness of the whole retina was decreased at these points in time, indicating a severe degradation of all retinal layers. Immunohistological and qRT-PCR analyses of retinal ganglion cells (RGCs), glial cells, AII amacrine, cone and rod bipolar as well as cone and rod photoreceptor cells confirmed this first assumption. Our results show that all investigated cell types were damaged by ischemia induction. Especially RGCs, cone bipolar cells, and photoreceptor cones are very sensitive to I/R. These cells were lost shortly after ischemia induction with a progressive course up to 7 days. In addition, Müller cell gliosis was observed over the entire period of time. These results provide evidence, that I/R induces damage of the whole retina at early stages and increases over time. In conclusion, our study could demonstrate the intense impact of an ischemic injury. The ischemic defect spreads across the whole retina right up to the outer layers in the long-term and thus seems to impair the visual perception already during the stimulus processing. In addition, our findings indicate that the cone pathway seems to be particularly affected by this damage.

Retinal ischemia is an important factor in several eye disorders. To investigate the impact of VEGF inhibitors, as a therapeutic option, we studied these in a retinal ischemia animal model. Therefore, animals received bevacizumab or ranibizumab intravitreally one day after ischemia induction. Via electroretinography, a significant decrease in a- and b-wave amplitudes was detected fourteen days after ischemia, but they were reduced to a lesser extent in the ranibizumab group. Ischemic and bevacizumab retinae displayed fewer retinal ganglion cells (RGCs), while no significant cell loss was noted in the ranibizumab group. Apoptosis was reduced after therapy. More autophagocytotic cells were observed in ischemic and bevacizumab eyes, but not in ranibizumab eyes. Additionally, more microglia, as well as active ones, were revealed in all ischemic groups, but the increase was less prominent under ranibizumab treatment. Fewer cone bipolar cells were detected in ischemic eyes, in contrast to bevacizumab and ranibizumab-treated ones. Our results demonstrate a reduced apoptosis and autophagocytosis rate after ranibizumab treatment. Furthermore, a certain protection was seen regarding functionality, RGC, and bipolar cell availability, as well as microglia activation by ranibizumab treatment after ischemic damage. Thus, ranibizumab could be an option for treatment of retinal ischemic injury.

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