Expression of Angiogenic Growth Factors in VLDL Receptor Knockout Mouse Retina With Spontaneous Subretinal Neovascularization

Abstract

Abstract: : Purpose: Gene knockout of very low density lipoprotein receptor (VLDLR) results in spontaneous subretinal neovascularization (NV) in mouse. To study the molecular mechanisms of subretinal NV, we examined the expression of angiogenic growth factors which may be involved in the development of subretinal NV in this vldlr–/– mouse. Methods: Development of subretinal NV in the vldlr–/– mouse was monitored using ophthalmoscopy, fundus photography, fluorescein angiography and histology. C57/BL6 mice of the same age were used as normal controls. VLDL receptor expression in the retina was determined in the knockout and control mice using immunocytochemistry. Vascular endothelium growth factor (VEGF) and basic fibroblast growth factor (bFGF) mRNA expressions were examined using RT–PCR and in situ hybridization. Results: In the vldlr–/– mouse retina, subretinal NV begins at 3–4 weeks and progressively worsens as the animal ages. Immunocytochemistry showed that VLDL receptor was localized in the vascular endothelium in wildtype retina and choroids, but its expression was absent in the vldlr–/– mouse retina or choroids. RT–PCR and in situ hybridization studies showed that there appeared no difference in VEGF expression in the retinas between the vldlr–/– and wildtype mice. However, bFGF mRNA expression was significantly elevated in the vldlr–/– mouse retina than in the wildtype. Conclusions: Our studies confirm that the VLDLR knockout is associated with spontaneous development of subretinal NV in mouse. VLDL receptor is normally localized in the vascular endothelium of retina and choroids. Our results demonstrate that bFGF mRNA expression is significantly elevated in the vldlr–/– mouse retina. This suggests that bFGF may play a critical role in the development of subretinal NV in this animal model.

Keywords: retinal neovascularization • transgenics/knock-outs • lipids