Abstract
Purpose :
Subretinal fibrosis is a prominent pathological feature of neovascular age-related macular degeneration (nAMD), responsible for permanent vision loss, and remains untreatable. Although anti-VEGF therapy effectively inhibits choroidal neovascularization (CNV) in most patients with nAMD, repetitive anti-VEGF treatments may increase the risk of subretinal fibrosis. Accumulating evidence suggests that RPE metabolism disturbance may be responsible, at least in part, for promoting CNV and fibrogenesis. The purpose of this study was to elucidate the underlying mechanism between the dysfunction of RPE metabolism and subretinal fibrosis in the nAMD.
Methods :
Very low-density lipoprotein receptor knock-out (Vldlr KO) mice were utilized as the experimental model since Vldlr KO mice manifest multiple nAMD-like phenotypes. A single-cell RNA sequencing (scRNA-seq) was performed to compare the transcriptomic profiles of RPE cells from age-matched wild-type (WT) and Vldlr KO mice. The identified gene changes in the scRNA-seq analysis, levels of fibrosis markers, and other proteins in the associated signaling pathway were measured by Western blot analysis, immunohistochemistry, and qRT-PCR. Vldlr-deficiency-induced metabolic reprogramming was examined using a Seahorse analyzer in primary RPE cells from Vldlr KO, WT control mice, and humans. The adeno-associated virus-mediated intervention was performed to explore the role of carnitine palmitoyltransferase 1A (CPT1A) in subretinal fibrosis in Vldlr KO mice.
Results :
scRNA sequencing and qRT-PCR analyses revealed the down-regulation of CPT1A and other essential genes in fatty acid oxidation in RPE cells of Vldlr KO mice compared to age-matched WT controls. Mechanistically, we found that TGFβ2-induced fibrosis was triggered by metabolic reprogramming from mitochondrial metabolism to glycolysis through downregulation of CPT1A in an ERK-dependent manner. In addition, VLDLR selectively interacted with unglycosylated TGFβ receptor II and blocked the formation of the TGFβ receptor I/II complex. We further demonstrated that over-expression of CPT1A suppressed the expression of fibrosis markers in the RPE of Vldlr KO mice.
Conclusions :
This finding identified a new regulation mechanism for RPE metabolism and the role of VLDLR in suppressing fibrosis. CPT1A may be a new therapeutic target for treating subretinal fibrosis.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.