Aqueous humor induces lymphatic regression on the ocular surface

Purpose: This study is to investigate the potential effect of aqueous humor on already formed lymphatic vessels of the ocular surface including the conjunctiva and the cornea. Methods: Aqueous humor harvested from fresh bovine or murine eyeballs were used in the study. It was injected into the subconjunctival space of Prox-1-GFP (green fluorescent protein) transgenic mice. Pre-existing conjunctival lymphatics were observed in vivo using our advanced live imaging system. Additionally, ex vivo tissue cultures were performed in aqueous humor with normal conjunctival tissues or inflamed corneas with newly formed lymphatic vessels. Time lapse images were taken by an advanced live cell imaging system with an incubator. Moreover, human primary microdermal lymphatic endothelial cell culture system was employed to evaluate the effect of aqueous humor on lymphatic tube regression in vitro. Results: Aqueous humor induced lymphatic regression in both normal conjunctiva and inflamed corneas. It also led to the regression of formed lymphatic tubes by the lymphatic endothelial cells in vitro. Conclusions: This study provides the first direct and real time live imaging evidence showing that aqueous humor induces lymphatic regression. Further investigation promises for divulging new mechanisms and therapeutic strategies to treat lymphatic diseases that occur both inside and outside the eye.