Abstract
Purpose :
Ocular trauma is the most common injury of modern wartime but there are no therapies available for promoting protection from, or reversal of, blast-related ocular injuries. To address this critical deficit, we developed a whole-organism screening platform for identifying compounds that promote long-term ocular tissue survival and sustained photoreceptor function in a zebrafish model of ocular trauma.
Methods :
To model ocular trauma in zebrafish, we developed an inducible ocular tissue ablation system; transgenic zebrafish lines in which yellow fluorescent protein (YFP) and the prodrug converting enzyme nitroreductase (NTR) are co-expressed in rod photoreceptors. Specific NTR substrates, such as CB1954, exhibit so-called bystander effects whereby rod cells and surrounding tissues are ablated upon exposure to prodrug, resulting in ocular edema. We use this in a phenotypic screen to identify drugs that protect the larval zebrafish eye from CB1954-induced edema. Each drug is assessed across a titration series spanning six different concentrations at a sample size of 12 per condition. To test for neuroprotective effects of hit compounds showing anti-edema effects, YFP-expressing rod cell numbers are quantified using an automated fluorescent plate reader platform we developed for whole-organism HTS (ARQiv) and high-resolution confocal imaging.
Results :
In a pilot screen using previously implicated cytoprotective compounds, we confirmed 10 out of 35 drugs that diminished CB1954-induced edema in zebrafish. Further, we identified one compound, panobinostat (LBH589), which completely abrogated CB1954-induced edema and protected rod photoreceptors from cell death. Panobinostat, thus serves as a positive control for a large-scale screen of ~3,300 FDA-approved drugs aimed at identifying new potential therapies for protecting ocular tissues and retinal cells from traumatic injury.
Conclusions :
Combining an easily visualized phenotypic assay with automated detection of photoreceptor numbers via ARQiv is an effective method for discovering drugs that protect, or stimulate regeneration of, ocular cells following traumatic injuries in zebrafish. Drugs that protect, and/or stimulate the regeneration of, ocular tissues and photoreceptor cells in zebrafish and across other model species have the potential to provide improved therapeutic strategies for ocular trauma patients.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.