Characterization of fatty acid binding protein 7 (FABP7) in the murine retina

Abstract

PURPOSE. To characterize the mouse retina lacking fatty acid binding protein (FABP7_/_). METHODS. Immunohistochemistry (IHC) was performed in 8-week-old mice to localize FABP7 in the retina. Retinal thickness was measured using image-guided spectral-domain optical coherence topography images. Electroretinography was carried out to assess retinal function. Fundus photography and fundus fluorescein angiography were performed on FABP7_/_ and littermate wild-type (WT) mice, and retinal vascular changes were calculated using Singapore I Vessel Assessment (SIVA) analysis. Blood glucose levels were measured in the 8-week-old WT and FABP7_/_ mice. In addition, retina was processed for trypsin digestion and retinal flat mounts for isolectin staining. Transcript levels of FABP7, VEGF, GFAP, and NaþKþATPase were quantified using real-time PCR, and protein expression was analyzed by IHC and Western blot. RESULTS. Fatty acid binding protein 7 is expressed in the inner nuclear layer, outer plexiform layer, and photoreceptor inner segments. No significant difference in retinal thickness and ERG responses was observed between FABP7-deficient and WT retinas. FABP7_/_ mice have significantly decreased retinal venular caliber retinal arteriolar fractal dimension compared with WT littermates. FABP7_/_ mice showed significant increased areas of fluorescein leakage in the retina. FABP7_/_ mice exhibited elevated high blood glucose levels compared with WT mice. Trypsin digested FABP7_/_ mice retina showed increased acellular strands and endothelial cell drop outs, and reduced microvasculature branching compared with WT retina. FABP7_/_ mice retina also have increased GFAP and VEGF expression. CONCLUSIONS. Fatty acid binding protein 7 is expressed in the retina and might play an important role in maintaining retinal vasculature.