Abstract
Purpose :
Sorsby Fundus Dystrophy (SFD) is a rare autosomal-dominant, early-onset macular degeneration linked to mutations in the tissue inhibitor of matrix metalloproteinases-3 (TIMP3) gene. Matrix metalloproteinases (MMPs) are proteolytic enzymes that digest extracellular matrix (ECM) components to regulate matrix turnover. MMPs lie under the control of tissue inhibitors of matrix metalloproteinases (TIMPs), a family of proteins that reversibly bind MMPs to inhibit matrix breakdown. This project characterizes the matrix alterations observed in TIMP3 mutant SFD in two in vivo murine models: (1) a TIMP3 s179c mutant knock in model and (2) a TIMP3 knockout model.
Methods :
Utilization of an unbiased proteomics approach characterized the “matrisome”—ensemble of ECM and ECM-associated proteins—of the RPE-choroid from both, TIMP3 s179c mutant and TIMP3 knockout models. RPE-choroid-sclera complexes dissected from murine tissues were homogenized and separated into cellular compartmental fractions (cytoplasmic, nuclear, membrane, cytoskeletal, and ECM). Isolated ECM fractions were prepared for LC-MS/MS proteomic analyses.
Results :
In the TIMP3 s179c model, we find increased levels of highly expressed drusen components, vitronectin (female: p=0.0020, male: p=0.027), clusterin (female: p=0.0012, male: p=0.033) and metalloproteinase inhibitor 3 (female: p=0.0012, male: p=0.047), as compared to sex-specific pooled controls. TIMP3 s179c male mice, alone, exhibit downregulation of laminin subunit alpha-1 (p=0.027). In the TIMP3 knockout model, male mice show significant differences in the expression of 42 matrix-related proteins (p<0.05), as compared to the sex-specific pooled control. In comparison, female TIMP3 knockout mice do not demonstrate any significant changes. Lastly, we observed in two groups—TIMP3 s179c mutant females (p=0.0225) and TIMP3 knockout males (p=0.0107)—statistically significantly decreased levels of endogenous antioxidant, Parkinson disease protein homolog-7/protein deglycase-1 (PARK7/DJ-1).
Conclusions :
Results of this study contribute to a more comprehensive understanding of the matrix changes observed with TIMP3 alterations in experimental murine models. This data will facilitate future mechanistic investigation to understand the role of the ECM in the pathophysiology of SFD and possibly, closely related disease process, age-related macular degeneration.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.