Caspase activation in an experimental model of retinal detachment

PURPOSE: To test for apoptotic photoreceptor cell death and caspase activation as a function of time after induction of an experimental retinal detachment. METHODS: Retinal detachments were created in Brown Norway rats by injecting 10% hyaluronic acid into the subretinal space using a transvitreous approach. Light microscopy and terminal dUTP-biotin nick end-labeling (TUNEL) was performed at 1, 3, 5, and 7 days after detachment to assess for the morphologic features associated with apoptosis. Western blot analysis of retinal protein extracts was performed using antibodies against caspase-3, -7, and -9 and poly-ADP ribose-polymerase (PARP) at 1, 3, and 5 days after detachment. RESULTS: Light microscopic analysis of detached retinas showed the presence of pyknotic nuclei in the outer nuclear layer and disruption of the normal organization of the photoreceptor outer segments. TUNEL-staining was positive in the outer nuclear layer only in the detached portions of the retina. Western blot analysis confirmed the time-dependent activation of caspase-3, -7, and -9 and PARP in the detached retinas. No morphologic stigmata of apoptosis or caspase activation was detected in attached retinas. CONCLUSIONS: The apoptotic photoreceptor cell death in experimental retinal detachments is associated with caspase activation.