Abstract
Purpose: :
Retinal detachment initiates a cascade of cellular changes that include photoreceptor outer segment degeneration followed by significant modification of their synaptic terminals and in some cases apoptotic cell death. In addition, second- and third-order neurons sprout neurites, Müller cells become reactive, macrophages invade the subretinal space, and microglia become activated and migrate to the outer retina. The purpose of this project was to study, over time, the changes in patterns of gene expression that may lead to an understanding of the molecular mechanisms underlying these cellular changes.
Methods: :
Retinal detachments were created in the right eyes of C57BL/6J mice. Left eyes were used as controls. Eyes were enucleated at 1, 3, 7, 28, and 180 days post detachment. Total RNA was extracted with Ambion’s mirVANA mRNA isolation kit. The extracted mRNA integrity was analyzed with Agilent’s bioanalyzer 2100. Microarray analysis was performed using Agilent’s 4x44K mouse whole genome array kit.
Results: :
Among the hundreds of genes that were upregulated at least 2 fold, waves of activition can be seen across the time-course of the study, especially among those genes involved in signaling pathways. While several changes in gene expression are initiated early and persist for 28 days, most others are transient (i.e. occur at only one time-point) or occur across two time-points. Only 1 gene (Calca) was upregulated at all detachment times. Several of these upregulated genes coincide with changes in protein expression already determined to occur after detachment by immunohistochemistry, including GFAP, vimentin, and CD44. Examples of signaling pathways activated by detachment include the complement pathway, JAK/STAT, TNF and FAS pathways, as well as several initiated by cytokines, growth factors, and antigen presentation.
Conclusions: :
Microarray analysis reveals several changes in gene expression that can be associated with many cell types in the retina. Many of these are involved in important signaling pathways. The results suggest that future direction should include determining how these changes in various signaling pathways produce the complex cellular responses initiated by detachment such as photoreceptor degeneration and cell death, glial scar formation, neuronal remodeling, and proliferative vitreoretinopathy.
Keywords: retinal detachment • gene microarray • signal transduction