Analysis of gene expression in ischemic neuroretinas: genome‐wide screen discriminating occlusion versus laser effects in rats

Purpose Identification of genes differentially expressed in rat neuroretinas submitted to experimental acute BRVO, to laser treatment, or to light exposure Methods Using an in vivo experimental model of BRVO in rat retinas, we induced acute ischemia by argon laser photocoagulation of venous sites near the ONH in the right eye of one group of animals. In a second group, right eye retinas were exposed to laser treatment at sites located between major vessels. A third group of animals had their right eye exposed to light through a slit lamp. Untreated left eyes served as controls in each animal. Total RNA was extracted from neuroretinas, 30 min and 6 h post treatments, and processed for global gene analysis with Affymetrix microarrays. Genome‐wide comparison of transcriptomes was then performed Results At 30 min, data did not reveal any sequence differentially expressed for the 3 treated groups. At 6 h, light exposure was definitively excluded as an impacting factor. However, the expression of 627 and 113 sequences changed, respectively post BRVO and post laser treatment. When comparing transcriptomes of both groups, we identified, respectively, 396 and 21 genes specifically modified. Interestingly, around 80 genes, all upregulated, were common to both groups. The majority of differentially regulated genes encode proteins involved in different aspects of a large number of complex pathways, among which we retained: inflammation, angiogenesis, apoptosis and neuroprotection Conclusion Microarray analysis revealed changes in gene expression bearing similarities to results from other ischemia models. Furthermore, it revealed that laser treatment may have unreported and specific impacts on retina’s metabolism