SIRT3-Dependent Metabolic Switch Governs Transition from Pathological to Physiological Angiogenesis

Abstract

Purpose : Proliferative retinopathies (PRs) are leading causes of blindness resulting from an initial loss of blood vessels (ischemia) which provokes an angiogenic response and the formation of pathological neovascular tufts (NVTs). While most treatments target NVTs directly, promoting faster regeneration of the avascular region could reduce ischemic stress and thus NVTs indirectly. However, the molecular mechanisms promoting physiological revascularisation without inducing pathological angiogenesis remain undefined in PRs.

Methods : We used a multi-omics approach to study the molecular traits of physiological and pathological angiogenesis in PR. We first compared the metabolomic profile of human vitreous from diabetic patients with PR to a classical mouse model of oxygen-induced retinopathy (OIR). We then performed single-cell RNAseq analyses on endothelial-enriched cell suspension from OIR and normoxic retina and confirmed the localization of new endothelial cell (EC) markers histologically. Finally, we shifted retinal metabolism by deleting Sirtuin-3 in mice (Sirt3-/-), a global mitochondrial regulator of FAO and respiration, and examined the impact on retinal metabolism, vascular growth, and vision.

Results : FAO metabolites, such as acylcarnitines, accumulated both in human PR vitreous collected adjacent to leaky NVTs and in the murine OIR retina. In this later, we observed a unique transcriptional signature for NVTs, defined partly by the abundant expression of aquaporin 1 (Aqp1). In addition, NVTs were metabolically distinct from physiological tip cells by their preferential reliance on FAO instead of glycolysis. Deleting FAO regulator Sirt3 limited the formation of NVTs and promoted faster physiological revascularization of the ischemic retina. Mechanistically, Sirt3-deletion acted as a metabolic switch, shifting EC metabolism from FAO to glycolysis and driving the expression of a physiological tip cell-like fate instead of NVTs. In OIR, faster vascular regeneration of the ischemic Sirt3-/- retina rescued visual function.

Conclusions : Here we define a specific molecular and metabolic signature for pathological neovessels and physiological tip cells in a model of proliferative retinopathy. We identify an actionable metabolic switch governed by Sirt3 that fosters physiological revascularization of the ischemic retina at the expense of pathological angiogenesis to improve vision.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.