Evidence of corneal lymphangiogenesis in dry eye disease: A potential link to adaptive immunity?

Objective: To determine the effect of desiccating stress on corneal angiogenic responses in dry eye disease (DED) using a murine model. Methods: Dry eye was induced in murine eyes using high-flow desiccated air. Corneas were double stained with CD31 (panendothelial marker) and LYVE-1 (lymphatic endothelial marker). Real-time polymerase chain reaction was performed to quantify expression of vascular endothelial growth factors (VEGF-A, VEGF-C, and VEGF-D) and their receptors (VEGFR-2 and VEGFR-3) in the cornea on days 6, 10, and 14. Enumeration of CD11b⁺/LYVE-1⁺ monocytic cells was performed in corneas with DED on day 14. Flow cytometric evaluation of the draining lymph nodes in normal mice and mice with DED was performed to determine whether DED is associated with homing of mature (major histocompatibility complex class II^hi) antigen-presenting cells to the lymphoid compartment. Results: Lymphatic vessels unaccompanied by blood vessels were seen growing toward the center of corneas with DED. Significant increases in lymphatic area (P<.001) and lymphatic caliber (P<.02) were seen on day 14 of disease. Lymphangiogenic-specific VEGF-D and VEGFR-3 levels increased earliest on day 6 followed by increased VEGF-C, VEGF-A, and VEGFR-2 levels. Increased recruitment of CD11b⁺/LYVE-1⁺ monocytic cells to the cornea and homing of mature CD11b⁺ antigen-presenting cells to the draining lymph nodes were also associated with DED. Conclusion: Low-grade inflammation associated with DED is an inducer of lymphangiogenesis without accompanying hemangiogenesis.