Abstract
Purpose::
Inflammation is thought to play a substantial role in the pathogenesis of age related macular degeneration (AMD). We aim to characterize gene expression patterns in white blood cells (WBCs) from patients with neovascular AMD (NVAMD) in order to identify candidate genes and pathways for involvement in the process.
Methods::
RNA was extracted from WBCs of 16 patients with NVAMD and 16 unaffected, age and gender matched controls. Microarray analysis was performed using oligonucleotide arrays containing 36,000 features, and by applying a reference sample design. Two distinct statistical algorithms were utilized to identify altered expression patterns: significance analysis for microarrays (SAM), and linear models for microarray data (LIMMA). Bioinformatics were applied to identify pathways which are associated with NVAMD. Results were validated using real time quantitative RT-PCR (QPCR) on a set of samples which were not tested by the arrays.
Results::
SAM analysis identified eight and 168 genes with NVAMD associated expression patterns at False Discovery Rate (FDR) of 0% and 10%, respectively. Four of the eight genes at FDR 0% were also detected by the LIMMA algorithm. The NVAMD associated gene list was enriched with genes involved in inflammation and antigen presentation. QPCR findings corroborated with microarray results for three of four genes which were tested. The mean increased expression levels in NVAMD patients compared with unaffected individuals for these three genes range between 1.8-fold to 5.3-fold.
Conclusions::
NVAMD is associated with altered expression level of several genes in WBCs. Such genes in general, and immune response related genes from this group in particular, are candidates for involvement in the pathogenesis of AMD. Ongoing studies assess if such alterations may serve as biomarkers for the disease, and test whether they are primary or secondary to the disease process.
Keywords: age-related macular degeneration • gene microarray • gene/expression