The Norrie Gene Product Is Necessary for Regression of Hyaloid Vessels

Abstract

Abstract: : Purpose: 1)To investigate whether the vitreous membranes in mice with knock-out of the Norrie gene product (ND mice) consist of persistent hyaloid vessels. 2)To analyse whether lack of the ND gene product might influence endostatin expression in ND mice. Methods: Seventy eight eyes of ND mice of different age groups (P0-11 months) and 88 age-matched wild-type controls were fixed with paraformaldehyde or ITOs solution. In whole mounts of vitreous and retina, vessels were visualised by NADPH diaphorase staining and staining for smooth muscle alpha actin (SMAA). In addition, staining with antibodies against collagen XIII/endostatin was performed for light and electronmicroscopical investigations. Endostatin expression was also analysed by Western blot analysis. Results: NADPH diaphorase and SMAA stained vitreoretinal wholemounts as well as electron microscopic investigations revealed that the retrolental membranes described in ND mice were persistent hyaloid vessels. Their morphology did not change throughout life. Endostatin was expressed in ND mice. The distribution of staining for endostatin was the same in ND mice and age matched controls up to day 16. Endostatin was localised in the basement membranes of the hyaloid vessels and the inner limiting membrane of the retina. In older ND mice the persisting hyaloid vessels remained endostatin positive. The retina proper was unstained. Conclusions: Retrolental membranes in ND mice consist of persistant hyaloid vessels indicating that the ND gene product is necessary for regression of hyaloid vessels. Expression of endostatin is not influenced by the knock-out of ND gen. Lack of ingrowths of retinal vessels described in ND mice could secondarily be due to increased oxygen levels in the vitreous.

Keywords: retinal development • animal model • vascular cells