Abstract
Purpose: :
To characterize the retinal phenotype of CYP27A1-/-CYP46A1-/ - mice with aberrant enzyme-mediated cholesterol removal.
Methods: :
Knockout (KO) and wild-type (WT) mouse retinas were evaluated in vivo by high-resolution spectral-domain optical coherence tomography (SD-OCT), fluorescein angiography (FA), histological staining for morphologic changes and electroretinography (ERG) for visual function.
Results: :
Starting at the age of 6 weeks, OCT revealed multiple small hyper-reflective structures distributed throughout the inferior retina as well as surrounding the optic nerve of CYP27A1-/-CYP46A1-/- mice. Histological staining with H&E showed pronounced structural retinal abnormalities including formation of multiple rosettes affecting several layers; outer nuclear layer (ONL), outer plexiform layer (OPL) and inner nuclear layer (INL). The pattern of these lesions varies, with some lesions starting at the choroid and protruding upward affecting the RPE, photoreceptors, ONL, OPL and the INL. Fluorescein angiography shows leakage suggesting neovascularization and hemorrhage in CYP27A1-/-CYP46A1-/- as compared to WT mice. Staining with filipin shows deposition of unesterified cholesterol in the choroidal blood vessels as well as in Bruch’s membrane and sub-retinal space. Furthermore, Oil Red O stain for neutral lipids shows enhanced staining within Bruch’s membrane. Evaluation by ERG shows a statistically significant decrease in the amplitude of scotopic a-wave and photopic b-wave in 6-month CYP27A1-/-CYP46A1-/- males and females as compared to WT mice suggesting an abnormal visual function.
Conclusions: :
Combined deficiency in CYP27A1 and CYP46A1 leads to profound changes in retinal structure as well as abnormal lipid deposition and vascularization with severe hemorrhages. Profiling of genes involved in lipoprotein signaling, cholesterol metabolism and angiogenesis is underway.
Keywords: retina • drusen • neovascularization