Abstract
Purpose :
Diseases that disrupt retinal blood supply, such as retinal vein occlusion (RVO) and diabetic retinopathy, are the leading causes of blindness in working-age adults. Despite available therapies, an estimated 50% of patients do not respond to treatment. To address the unmet need in treatment of retinal edema, we demonstrate efficacy of a novel therapeutic targeting caspase-9 in a mouse model of RVO.
Methods :
RVO was achieved in 2-4 month old mice by tail-vein injection of rose bengal, followed by laser photocoagulation of retinal veins. In vivo analyses – optical coherence tomography (OCT), fluorescein angiography (FA) and electroretinograms (ERG) - were conducted with the Micron IV system (Phoenix Research Labs). C57/BI6 male mice were purchased from Jackson Laboratories. Endothelial specific caspase-9 inducible knockout mice (C9 ECKO) were bred by crossing Caspase-9LoxP/LoxP and endothelial cell-CreERT2 mice. Caspase-9 inhibitor (Pen1-XBir3) was generated by crosslinking the Bir3 domain of XIAP (an endogenous inhibitor of caspase-9) to Penetratin-1, a cell permeant peptide. An ocular distribution study of Pen1-XBir3 eyedrops was performed by EyeCRO in adult female New Zealand White Rabbits.
Results :
Increased levels of activated caspase-9 were detected in endothelial cells after RVO. Compared to littermate controls, endothelial caspase-9 knockout (C9 ECKO) mice developed less edema, and sustained less retinal degeneration after RVO injury. To investigate pharmacological inhibition of caspase-9 as a therapeutic strategy, we developed a highly specific caspase-9 inhibitor (Pen1-XBir3), which can be delivered to the retina via eye drops. Treatment with Pen1-XBir3 conferred morphological and functional retinal protection from RVO. Treated eyes developed less fluorescein leakage, less retinal swelling and detachment, and had better preservation of retinal morphology after resolution of edema. Fewer hyperreflective foci, an indicator of inflammation associated with poor vision outcomes, were detected in the retina and vitreous of eyes treated with Pen1-XBir3. ERG analysis showed that Pen1-XBir3 protected retinal function after RVO injury.
Conclusions :
We identified caspase-9 as an essential mediator of edema. Our novel caspase-9 inhibitor eye drops reduce the edema and vision deficits associated with RVO, and may be a potential therapy for individuals suffering from vascular eye disease.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.