Delineating the role of TIMP3 in macular degeneration

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ABSTRACT The retinal pigment epithelium-choriocapillaris (RPE-CC) complex is the primary site of disease pathogenesis in several eye diseases, including age-related macular degeneration (AMD) and related macular dystrophies, like Sorsby’s fundus dystrophy (SFD). Notably, sub-RPE accumulation of tissue inhibitor of metalloproteinase 3 (TIMP3) is a prominent feature of SFD/AMD. However, it is not known “how” sub-RPE TIMP3 accumulation promotes SFD/AMD pathology. This is partially because the RPE-CC is a functional composite making it difficult to study the contribution of spatial changes in RPE versus CC layer during disease development in vivo. Furthermore, the lack of a representative model of the RPE-CC in vitro has significantly impacted our ability to study RPE-CC interaction in vitro. Using induced pluripotent stem cells (iPSCs), we have developed an iPSC- RPE-CC model that recapitulate key features of both healthy and AMD/SFD eyes. Specifically, iPSC-RPE-CC shows evidence of fenestrated CC-like vasculature and Bruch’s membrane like ECM. Similarly, SFD iPSC-RPE- CC displays two central hallmarks of SFD/AMD, drusen and choroidal neovascularization (CNV)-like pathology. Notably, longitudinal analyses of control versus SFD iPSC-model showed that sub-RPE TIMP3 accumulation occurs relatively early and precedes maculopathy cellular events. Furthermore, our preliminary proof of concept studies shows that sub-RPE TIMP3 accumulation in the SFD iPSC model promotes pro-maculopathy cellular changes via dysregulated lipid metabolism and sterile inflammation. Based on these strong preliminary studies, the overall goal of this proposal is to establish the independent contribution of sub-RPE TIMP3 accumulation to AMD/SFD pathology development. We will perform spatial (RPE versus CC) and temporal (e.g., prior and after drusen formation) manipulation of TIMP3 expression/activity in i) SFD iPSC-RPE-CC and ii) control iPSC-RPE- CC cultures (iPSCs derived from healthy subjects with normal vision) to test the hypotheses that sub-RPE TIMP3 accumulation leads to dysregulated lipid metabolism and sterile inflammation and consequently i) drusen beneath the RPE monolayer and ii) CC atrophy and CNV. From a therapeutic standpoint, we will pharmacologically target dysregulated lipid metabolism and sterile inflammation in SFD/AMD iPSC models.