Targeting Ferrochelatase For Treating Of Retinal Neovascularization

Abstract

BackgroundPathological retinal neovascularization (RNV) is a common microvascular complication in several retinal diseases including retinopathy of prematurity, proliferative diabetic retinopathy, and central retinal vein occlusion. RNV is currently treated by inhibition of vascular endothelial growth factor (VEGF), with some therapeutic success, but some patients do not respond to anti‐VEGF treatment, calling for additional means to block RNV. We previously identified the heme biosynthesis enzyme ferrochelatase (FECH) as an angiogenesis mediator. FECH inhibition is, therefore, a promising therapeutic approach for blocking RNV in the eye. Here, we investigated the inhibition of FECH using chemical and genetic approaches in the mouse oxygen‐induced retinopathy (OIR) model of RNV.MethodsIn the OIR model, newborn wild‐type or Fechm1Pas mice (with a partial loss‐of‐function mutation) are exposed to 75% oxygen at postnatal day 7 (P7) for 5 days, causing retinal vascular regression. At P12, upon return to normoxia, the retina becomes ischemic, forming RNV. Vascular pathology was assessed at P17 using Isolectin B4 staining. In a chemical approach, FECH inhibitor N‐methyl protoporphyrin (NMPP), was intravitreally injected in OIR mice at P12 and RNV assessed at P17. Pimonidazole hydrochloride and 5‐ethynyl‐2′‐deoxyuridine (EdU) were administered intraperitoneally at different time points to monitor hypoxia and cell proliferation in retinal tissue. Temporal expression of FECH was analyzed at various ages in mouse OIR retinas using immunoblot and immunostaining.ResultsRetinal flat mounts of the OIR model, which features central avascular retina, exhibit co‐localization of hypoxic, pimonidazole‐adduct immunostaining and neovascular tufts across the retina using Isolectin B4 immunostaining. Temporal FECH upregulation was observed in mouse OIR retinas by immunoblot, and immunostaining revealed that FECH is colocalized with neovascular tufts. A partial loss of function allele in the Fech m1Pas mouse significantly reduced pathological RNV (****P<0.0001, N=8–15 eyes) and cell proliferation (****P<0.0001, N=4–6 eyes) in the OIR model compared to wild‐type littermates. In another approach, chemical inhibition of FECH by NMPP treatment significantly suppressed the RNV and cell proliferation (****P<0.0001, N=8 eyes) and also significantly promoted physiological angiogenesis compared to vehicle treatment in the OIR mouse model.ConclusionsMutation of Fech and chemical inhibition using NMPP reduces pathological RNV and intriguingly, also promotes physiological angiogenesis, suggesting a dual effect on vascular repair upon FECH inhibition. Together, these findings suggest that FECH inhibitors could be used to treat neovascularization in ocular diseases.Support or Funding InformationNIH/NEI R01EY025641This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.