Abstract
Sorsby Fundus Dystrophy (SFD) is a rare form of macular degeneration that is clinically similar to age-related macular degeneration (AMD). SFD results from mutations found in the tissue inhibitor of metalloproteinase 3 (TIMP3) gene. TIMP3 is secreted by the retinal pigmented epithelium (RPE) into the underlying Bruch’s membrane (BrM), and it plays a critical role in maintaining extracellular matrix (ECM) homeostasis. A characteristic feature of post-mortem SFD globes is a thick layer of sub-RPE deposits overlying a disorganized BrM. Although likely central to the pathogenesis of SFD, no animal models have reproduced this phenotype. We generated induced pluripotent stem cell (iPSC)-derived RPE lines from SFD family members with the S204C TIMP3 mutation and observed that SFD RPE have highly dysregulated ECM and form large basal deposits by ~30 days in culture. The sub-RPE deposits are similar in ultrastructure and composition when compared to SFD family member globes. Mutant TIMP3 correction by CRISPR-Cas9 gene editing in SFD iPSC RPE cells resulted in the reversal of sub-RPE calcium deposition. We found that SFD TIMP3 has decreased inhibition of secreted matrix metalloproteinases. ECM dysfunction substantially impacts cellular metabolism. Targeted metabolomics data showed that intracellular 4-hydroxyproline, a major breakdown product of collagen, is significantly elevated in SFD RPE. Further, SFD RPE also has decreased intracellular reduced glutathione and is more vulnerable to oxidative stress. These findings suggest that key elements of SFD pathology can be recapitulated in culture which may lead to insights into disease mechanisms and potential treatments.
Significance Statement This study demonstrates that retinal pigmented epithelial (RPE) cells generated from patients with Sorsby Fundus Dystrophy (SFD) produce highly dysregulated extracellular matrices. SFD RPE form large basal deposits in culture that are similar in composition to what is observed in donated SFD post-mortem globes from family members. Further, SFD RPE demonstrate high levels of 4-hydroxyproline, a major breakdown product of collagen. SFD RPE are also more vulnerable to oxidative stress. Our studies indicate that key elements of SFD pathology can be recapitulated in culture, and ECM dysregulation may lead to metabolic changes detrimental to RPE health.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Abbi Engel: Collection and/or assembly of data, data analysis and interpretation, manuscript writing Yekai Wang: Collection and/or assembly of data, data analysis and interpretation, Thomas Khuu: Collection and/or assembly of data, Emily Worrall: Collection and/or assembly of data, data analysis and interpretation Megan Manson: Collection and/or assembly of data, Kaitlen Knight: Collection and/or assembly of data, data analysis and interpretation Aya Yanagida: Collection and/or assembly of data, data analysis and interpretation Jian Hua Qi: Collection and/or assembly of data, data analysis and interpretation Aravind Ramakrishnan: Provision of study material or patients, Richard Weleber: Provision of study material or patients Michael Klein: Provision of study material or patients David Wilson: Provision of study material or patients, Bela Anand-Apte: Data analysis and interpretation, manuscript writing, final approval of manuscript James Hurley: Conception and design, manuscript writing, final approval of manuscript, Jianhai Du: Conception and design, provision of study material or patients, collection and/or assembly of data, data analysis and interpretation, manuscript writing, final approval of manuscript, Jennifer Chao: Conception and design, provision of study material or patients, collection and/or assembly of data, data analysis and interpretation, manuscript writing, final approval of manuscript