Integrin Alpha-9 Mediates Lymphatic Valve Formation in Corneal Lymphangiogenesis

PURPOSE. We recently reported that corneal lymphatic vessels develop integrin alpha-9 (Itga-9)-positive valves during inflammatory lymphangiogenesis. The purpose of this study was to further investigate the role of Itga-9 in corneal lymphatic valve formation in vivo and lymphatic endothelial cell (LEC) functions in vitro. METHODS. Standard murine suture placement model was used to study the effect of Itga-9 blockade on lymphatic valve formation in vivo using Itga-9 neutralizing antibody. Whole-mount corneas were harvested for immunofluorescent microscopic analysis. Additionally, human LEC culture system was used to examine the effect of Itga-9 gene knockdown on cell functions using small interfering RNAs (siRNAs). RESULTS. Itga-9 blockade in vivo significantly reduced the number of lymphatic valves formed in the inflamed cornea. Moreover, Itga-9 gene knockdown in human LECs suppresses cell functions of proliferation, adhesion, migration, and tube formation. CONCLUSIONS. Itga-9 is critically involved in corneal lymphatic valve formation. Further investigation of the Itga-9 pathway may provide novel strategies to treat lymphatic-related diseases occurring both inside and outside the eye.