Abstract
Purpose :
Ferrochelatase (FECH) is the terminal enzyme in the heme biosynthesis pathway. We previously showed that FECH is required for endothelial cell growth in vitro and choroidal neovascularization in vivo. But the role of the FECH gene has not been explored in retinal neovascularization, which underlies diseases like proliferative diabetic retinopathy and retinopathy of prematurity. Here, we investigated the inhibition of FECH using genetic and direct chemical approaches in the ischemia-driven retinal angiogenesis of the oxygen-induced retinopathy (OIR) mouse model.
Methods :
In murine OIR, postnatal day 7 (P7) mice from C57BL6/J or Fechm1Pas mutants were exposed to hyperoxia (75% O2) and at P12, were returned to normoxia and euthanized at P17. FECH inhibitor, N-methyl protoporphyrin (NMPP) was intravitreally injected at P12, and retinal flatmounts or sections were analyzed at P17 using isolectin B4 immunostaining and confocal microscopy. 5-ethynyl-2′-deoxyuridine (EdU) and pimonidazole hydrochloride were administered i.p. at various time points to monitor vascular cell proliferation and hypoxia in the retina, respectively. mRNA and protein expression of FECH in OIR retina was assessed at different OIR time points by qPCR, immunoblot, and immunostaining.
Results :
In murine OIR, FECH mRNA and protein expression were upregulated over time and co-localized with neovascular tufts in the vascular pathology but did not associate with areas of hypoxia. Partial loss-of-function Fechm1Pas mutant mice, both homo- and heterozygotes, showed reduced pathological retinal neovascularization, vaso-obliteration, and endothelial cell proliferation in the OIR model, as well as reduced hypoxic area compared to wild-type littermates. Pharmacological inhibition of FECH by NMPP significantly reduced retinal neovascularization, vaso-obliteration, and cell proliferation as well.
Conclusions :
Mutation of Fech and chemical inhibition using NMPP reduces retinal neovascularization and promotes physiological angiogenesis, suggesting a normalizing effect on vasculature upon FECH inhibition. Exploration of the mechanisms of this process is underway. Together, these findings suggest that FECH inhibition should be further explored to treat retinal neovascularization.
This is a 2020 ARVO Annual Meeting abstract.