AAV2-driven endothelin induces chronic reduced retinal blood flow/retinal ganglion cell loss in rats

Dysfunction of ocular blood flow (BF) is believed to be one of the causes of glaucomatous pathology. However, whether this dysfunction is indeed a cause or is actually a consequence of optic nerve degeneration remains controversial. Here, we established a new animal model of chronic BF reduction in the retina to mimic glaucoma. We found that retinal BF in rats, as measured with laser speckle flowgraphy, was significantly reduced 3 wk after an intravitreal injection of AAV2-human endothelin-1 (AAV2-hEDN1). The number of retinal ganglion cells was also reduced in rats that received AAV2-hEDN1 injection. Immunostaining signals for GFAP and the endothelin-B receptor were enhanced in the rat retinas after AAV2-hEDN1 injection. Moreover, mRNA levels of <i>Ripk1</i>/<i>Ripk3</i> and <i>Tnf</i> in the retina increased, and glutathione levels in the aqueous humor decreased in rats that received AAV2-hEDN1 injection. Our findings demonstrate that endothelin-induced chronic retinal BF reduction leads to increased astrocyte activation and oxidative stress, which in turn induces retinal ganglion cell necroptosis. This suggests that methods to improve ocular BF have potential as novel therapies for glaucoma.