Abstract
Purpose :
Elucidating the molecular landscape of the aging retinal pigment epithelium (RPE) is a primary focus in our effort to decode the pathogenic mechanisms of age-related macular degeneration. While many studies in model organisms have unraveled the impact of epigenetic changes on cellular aging, a comprehensive understanding of these epigenomic transformations with the aging RPE is currently lacking. This study performed a comparative transcriptome analysis of young and aged RPE/choroid tissues to elucidate the epigenomic landscape of aging RPE.
Methods :
The transcriptional profiles of RPE/choroid from young (1-2 months) and aged (22-24 months) C57BL/6J mice were compared to identify the changes in the expression patterns of histone genes and regulatory factors that control epigenome. Changes in histone expression and epigenetic regulatory factors were validated using qPCR, IHC, and Western blot (WB). Levels of histone deacetylases and histone acetyltransferases (HATs) were compared between young and aged RPE using qPCR and WB. Metabolomic analysis, by mass spectrometry, was done to evaluate the acetyl CoA level in young and aged RPE. Human RPE isolates (n=3) were grown to replicative exhaustion, and the expression levels of histones were compared in young and senescent cells using qPCR and WB analysis. IHC was performed to compare the histone levels in young and aged human RPE.
Results :
Our data demonstrated a dramatic loss of global histone expression in the aging RPE/choroid, along with significant differential expression of 132 epigenetic regulatory factors. Global loss of histones with aging was accompanied by the downregulation of transcription factors like HinfP and NPAT that regulate histone gene expression. Furthermore, there was a significant depletion of histone H3 and H4 acetylation and altered patterns of specific histone acetyl marks between the young and aged RPE. Metabolomic analysis revealed that aged RPE has a decreased level of acetyl CoA, a primary substrate for HAT. Human eye sections showed loss of histones and acetyl histones in aged RPE. Senescent hRPE cells showed downregulation of histones, mimicking the in vivo expression pattern of aging RPE.
Conclusions :
Our results show the complex epigenomic remodeling and metabolic changes that occur in the aging RPE, which could lead to loss of retinal homeostasis and the development of age-related diseases like AMD.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.