ROCK inhibition reduces morphological and functional damage to rod synapses after retinal injury

Retinal detachment (RD) causes damage, including disjunction, of the rod photoreceptor-bipolar synapse, which disrupts vision and may contribute to the poor visual recovery observed after retinal reattachment surgery. We created a model of iatrogenic RD in adult female pigs to study damage to the rod-bipolar synapse after injury and the ability of a highly specific Rho-kinase (ROCK) inhibitor to preserve synaptic structure and function. This model mimics procedures used in humans when viral vectors or cells are injected subretinally for treatment of retinal disease. Synaptic disjunction by retraction of rod spherules, quantified by image analysis of confocal sections, was present 2 h after detachment and remained 2 days later even though the retina had spontaneously reattached by then. Moreover, spherule retraction occurred in attached retina 1-2 cms from detached retina. Synaptic damage was significantly reduced by ROCK inhibition in detached retina whether injected subretinally or intravitreally. Dark-adapted full-field electroretinograms were recorded in reattached retinas to assess rod-specific function. Reduction in synaptic injury correlated with increases in rod-driven responses in drug-treated eyes. Thus, ROCK inhibition helps prevent synaptic damage and improves functional outcomes after retinal injury and may be a useful adjunctive treatment in iatrogenic RD and other retinal degenerative diseases.