Abnormal vascularization in mouse retina with dysregulated retinal cholesterol homeostasis

Abstract

Several lines of evidence suggest a link between age-related macular degeneration and retinal cholesterol maintenance. Cytochrome P450 27A1 (CYP27A1) is a ubiquitously expressed mitochondrial sterol 27-hydroxylase that plays an important role in the metabolism of cholesterol and cholesterol-related compounds. We conducted a comprehensive ophthalmic evaluation of mice lacking CYP27A1. We found that the loss of CYP27A1 led to dysregulation of retinal cholesterol homeostasis, including unexpected upregulation of retinal cholesterol biosynthesis. Cyp27a1 -/-mice developed retinal lesions characterized by cholesterol deposition beneath the retinal pigment epithelium. Further, Cyp27a1-null mice showed pathological neovascularization, which likely arose from both the retina and the choroid, that led to the formation of retinal-choroidal anastomosis. Blood flow alterations and blood vessel leakage were noted in the areas of pathology. The Cyp27a1 -/-retina was hypoxic and had activated Müller cells. We suggest a mechanism whereby abolished sterol 27-hydroxylase activity leads to vascular changes and identify Cyp27a1 -/-mice as a model for one of the variants of type 3 retinal neovascularization occurring in some patients with age-related macular degeneration.

Retinal Hypercholesterolemia Triggers Cholesterol Accumulation and Esterification in Photoreceptor Cells

“…TEM and SD-OCT-These procedures were as described (72,73) and utilized a 1200EX transmission electron microscope (JEOL Ltd.) and the 840HHP SD-OCT system (Bioptigen). Tissue fixation for TEM was as described (36) and included sequential incubations in 3% glutaraldehyde in 0.1 M sodium cacodylate buffer, pH 7.4, 1% OsO 4 in the same buffer, 1% tannic acid in 0.05 M sodium cacodylate, pH 7.4, and 1% paraphenylenediamine in 70% ethanol.…”

“…Immunohistochemistry-The preparation of frozen and paraffin retinal sections was as described (3,27,72), except mice underwent cardiac perfusion with 30 ml of phosphate-buffered saline to remove blood from the retina. Prior to immunohistochemistry, paraffin sections were deparaffinized followed by heat-induced antigen retrieval in a microwave three times for 6 min with 10 mM sodium citrate buffer, pH 6.0, containing 0.05% Tween 20.…”

Pathways of cholesterol homeostasis in mouse retina responsive to dietary and pharmacologic treatments

“…We used WT mice as well as Cyp27a1 Ϫ / Ϫ mice ( 16 ) lacking the major enzyme, CYP27A1, metabolizing cholesterol in the retina (17)(18)(19). The Cyp27a1 Ϫ / Ϫ retina has increased cholesterol content and vascular lesions associated with focal deposits of cholesterol ( 20 ). The pathways of cholesterol input and output are uncoupled in the Cyp27a1 Ϫ / Ϫ retina ( 20 ); hence,…”

“…The Cyp27a1 Ϫ / Ϫ retina has increased cholesterol content and vascular lesions associated with focal deposits of cholesterol ( 20 ). The pathways of cholesterol input and output are uncoupled in the Cyp27a1 Ϫ / Ϫ retina ( 20 ); hence,…”

Pretreatment with Pyridoxamine Mitigates Isolevuglandin-associated Retinal Effects in Mice Exposed to Bright Light

“…Transverse cryosections (5 m thick) of the central retina were prepared as described (60). Slides were equilibrated to room temperature for 20 min, rinsed in PBS twice, and incubated in PBS containing 0.3% Triton X-100 for 20 min.…”