Identification of miRNAs in a Model of Retinal Degenerations.

Purpose: We investigated the expression profile of and identify all microRNAs (miRNAs) that potentially regulate inflammation in a light-induced model of focal retinal degeneration.

Methods: Sprague Dawley (SD) rats aged 90 to 140 postnatal days were exposed to 1000 lux white fluorescent light for 24 hours. At 24 hours, and 3 and 7 days after exposure, the animals were euthanized and retinas processed for RNA. Expression of 750 miRNAs at 24 hours of exposure was assessed using low density array analysis. Significantly modulated miRNAs and their target mRNAs were used to assess the potential biological effects. Expression of seven miRNAs, potentially modulating inflammation, was investigated across a protracted time course after light exposure using quantitative PCR. Photoreceptor cell death was analyzed using TUNEL.

Results: Intense light exposure for 24 hours led to differential expression of a number of miRNAs, 37 of which were significantly modulated by 2-fold or more. Of those, 19 may potentially regulate the inflammatory immune response observed in the model. MicroRNAs -125-3p, -155, -207, -347, -449a, -351, and -542-3p are all upregulated at 24 hours of exposure along with peak photoreceptor cell death. The MiRNAs -542-3p and -351 reached maximum expression at 7 days after exposure, while -125-3p, -155, -207, -347, and -449 reached a peak expression at 3 days.

Conclusions: The results of the study show that miRNAs are modulated in response to light damage (LD). These miRNAs potentially regulate the inflammatory immune response, triggered as a result of the acute retinal damage, which is a key mediator of retinal degeneration in this model and age-related macular degeneration.