The antilymphangiogenic effect of aqueous humour

Abstract

Purpose: The cornea, which is free of blood and lymphatic vessels bathes on the endothelial site in the Aqueous humor (AqH). Because of the direct contact of AqH to the cornea, we wanted to know whether it could prevent ingrowths of blood and, especially, lymphatic vessels into the cornea. Methods: In vitro: quantifying lymphatic endothelial cell (LEC) proliferation with a colorimetric (BrdU) proliferation ELISA with 5 or 20 μl of human AH and as control EGM‐2MV medium. In vivo: murine model of inflammatory corneal neovascularization; treatment group (n=5) received 3 μl of murine AH once a day at day of surgery and for the following three days(control saline solution). After five days, mice were sacrificed. Corneal flat mounts were stained with LYVE‐1 as a specific lymphatic vascular endothelial marker and CD31 as panendothelial marker. Morphometry of blood and lymphatic vessels was performed with the image analysis software analySIS^B. Results: Human AH inhibited the proliferation of the lymphatic endothelial cells in vitro in a dose dependent manner (5μl: p>0.0847 n.s; 20μl: p< 0.0001). The topical application of aqueous humour inhibited the outgrowth of blood vessels significant (P < 0.006) in comparison to the control. The outgrowth of lymphatic vessels was also inhibited significant (P< 0.0002). Conclusions: AH inhibits the proliferation of lymphatic endothelial cells in vitro and the outgrowth of blood and lymphatic vessels in the cornea in vivo. Tissues like the cornea, the iris and the ciliary body are naturally free of blood and, moreover, lymphatic vessels. Therefore, the aqueous humour seems to play an important role to avoid the ingrowths of blood and lymphatic vessels into the anterior chamber and its adjacent tissues.