Abstract
Purpose :
Aging is a major factor in the development and progression of macular disease whether age-related or heritable. The choroid contributes to the homeostasis of the retina, and age-related changes in choroid structure and function are thought to contribute to these diseases. The purpose of this study was to identify the major effects of age on the choroid in wild type (Wt) mice and in mouse models of late onset retinal degeneration (L-ORD) due to mutations in C1qtnf5/Ctrp5.
Methods :
The proteomes of the choroids of wild type C57BL6 and Ctrp5S163R mutant mice were determined at 4.5 and 19 mo and at 4.5 and 18 mo, respectively. The choroid/Bruch’s membrane was dissected, proteins solubilized and separated on SDS gels. After in-gel trypsin digestion, peptides were separated and peptide masses analyzed using mass spectrometry. MaxQuant software was used for database searching, peptide and protein identification and quantification. Principal component analysis (PCA) was done using SOLO, Eigen Vector. IHC was used to localize specific proteins.
Results :
PCA showed strong clustering by age for both genotypes. About 24% of the 3700 proteins identified were significantly altered with age in Wt mice. Specific markers for mast cells, endothelial cells and melanocytes showed statistically significant changes in each cell type with age. The decrease in plasmalemma vesicle-associated protein, the major component in fenestrae, an endothelial substructure, suggested structural changes in the choriocapillaris. Tyrosinase, the rate limiting enzyme in melanin synthesis decreased 3 fold. These age-related changes occurred to the same extent in Wt and mutant mice. Of the 250 proteins of the innate immune system 60 underwent changes with age. The most remarkable changes were the 4 mast cell proteases which were increased over 3-4 fold in Wt and 10-12 fold in Ctrp5S163R mutant mice, the 5 fold increase in the carboxypeptidase A inhibitor, latexin, in mutant mice and cathepsin S which was increased 5 fold in Wt and 15 fold in mutant mice.
Conclusions :
Each of the aging changes identified correlate with processes that are reported to be factors in macular disease. Loss of melanin, changes in choriocapillaris function and immune activation with age will negatively impact retinal homeostasis in both genotypes. The excess immune system activation in Ctrp5S163R mutant mice may be a major factor in the pathobiology of L-ORD.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.