Abstract
Purpose :
Aging is a major risk factor for a number of ocular diseases including macular degeneration, glaucoma, cataract, and dry eye. Despite its key role in eye disease, the ocular tissue aging signature has not been fully established. To establish the aging ocular tissue transcriptional landscape, we performed an RNA-Seq study and systematically investigated rats aged from 9 months to 27 months in limbal ring and retina.
Methods :
Eleven to twelve biological replicates per tissue (limbal ring and retina) per age group (9, 12, 15, 18, 24, and 27 months old) were collected from Sprague Dawley rats and RNA was extracted following RNeasy Plus Mini Kit protocol.
RNA-seq libraries were prepared by a Poly(a)+ selection method and sequenced with the Illumina HiSeq 2500 platform. The exon quantification pipeline was used for read alignment to the ENSEMBL rat genome (Rnor 6.0) and transcript quantification. Differential expression analysis by t-test was run using edgeR and limma R packages. A custom python script was used for a Kolmogorov-Smirnov-based gene set enrichment analysis.
Results :
Both genes and biological pathways were identified as aging signatures. Aging continuously affected expression of 522 genes in the limbal ring and 80 genes in the retina (log2FC >= 0.50; FDR <= 0.05). Biological pathways regulated between old and young rats included 113 pathways in the limbal ring and 98 pathways in the retina (|Mean log2FC| >= 0.2; -log10 p-value >=10). Common signatures included an upregulation of immune response and extracellular matrix gene sets and downregulation of mitochondria function, cell cycle, and mRNA processing gene sets by age.
Conclusions :
We identified an ocular tissue aging molecular signature at the gene and pathway levels. Limbal ring had more profound changes with aging, but common signatures were observed in both tissues, namely an upregulation of immune response and extracellular matrix genes and downregulation of mitochondria function, cell cycle, and mRNA processing genes. Interestingly, immune activation and mitochondrial dysfunction are also associated with ocular diseases like AMD and glaucoma. Further study is needed to determine whether these aging signatures increase susceptibility or are causative to disease.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.