Identification of PGC-1β as promising therapeutic target of neovascular AMD

Abstract

Purpose : RPE dysfunction and choroidal neovascularization (CNV) are the major hallmarks of neovascular AMD (nAMD). We previously identified PGC-1β, a master regulator of mitochondrial function, as a novel stress response gene in RPE positively associated with nAMD. However, the unique pathologic functions of PGC-1β in RPE during nAMD remained unclear. We hypothesize that PGC-1β promotes CNV and nAMD by driving RPE toward a pro-angiogenic and pro-inflammatory profile.

Methods : Expression of PGC-1β in human AMD and age-matched control eyes was analyzed by immunohistochemical staining. Time-course expression of PGC-1β was measured in murine RPE/choroid in the model of laser-induced CNV. PGC-1β was overexpressed in RPE of adult WT mice using subretinal injection of pLV-PGC1B. Funduscopy, SD-OCT, TEM, F-actin and IB4 staining of whole mount RPE was performed 4 and 8 weeks after injection. PGC-1β was induced in matured ARPE-19s using a Tet-responsive adenovirus and doxycycline exposure. Conditioned media collected on PGC-1β expressing RPE was analyzed using protein arrays.

Results : PGC-1β was strongly induced in RPE surrounding the fibrovascular lesions in nAMD eyes while no expression could be detected in RPE of both control and atrophic AMD samples. Following laser induction of CNV in mice, PGC-1β was rapidly induced in the RPE/choroid complex at day 3 (n=6, P<0.05), peaking at day 7 (n=6, P<0.001) post-laser. PGC1B overexpression in the RPE of adult mice led to reduction in total retinal thickness (n=5, P<0.05), pigmentary changes and RPE disorganization characterized by pathological morphology (89% VS 8%, n=4) and larger area (n=4, P<0.05) when compared to pLV-GFP controls. Ultrastructural analysis of PGC-1β induced RPE showed disordered apical microvilli, shorten basal infoldings, reduced melanosomes and accumulation of undigested outer segments. Vascular leakage and spontaneous CNV were observed in 20% of pLV-PGC-1β injected eyes (n=15). Analysis of secreted proteins from PGC-1β expressing RPE revealed the induction of the pro-angiogenic and pro-inflammatory factors AREG (P<0.05), HB-EGF (P<0.05), bFGF (P<0.05), IL8 (P<0.0001) and prolactin (P<0.01) (n=4).

Conclusions : We identify PGC-1β as a novel biomarker of nAMD. Pathological induction of PGC1B promotes RPE dysfunction and secretion of pro-angiogenic factors, leading to nAMD-like retinal degeneration and CNV in mice.

This is a 2021 ARVO Annual Meeting abstract.