Purpose.: To elucidate the role of signals mediated by EphB4 receptor tyrosine kinase and its transmembrane ephrinB2 ligand in corneal lymphatic capillaries.

Methods.: To detect expression of ephrinB2 and EphB4 in mouse corneas, immunohistochemistry of flat-mount corneas from 6-to 10-week-old wild-type, Efnb2-lacZ, and Ephb4-lacZ mice on a C57BL/6 background was performed. To induce formation of new blood vessels and lymphatic vessels, mouse corneal epithelia were swabbed with 0.1 M sodium hydroxide. To antagonize endogenous receptor–ligand interactions in corneal lymphatic vessels, recombinant EphB4/Fc proteins were injected into the subconjunctival spaces. To visualize the corneal lymphatic flow, FITC-dextran was injected subconjunctivally.

Results.: In lymphatic capillaries of adult mouse corneas, EphB4 was intensively expressed in lymphatic endothelial cells (LECs) of funnel-shaped valves, which were segregated from ephrinB2-expressing LECs. The number of corneal lymphatic valves was significantly decreased by Efnb2 haploinsufficiency, and subconjunctival EphB4/Fc injections resulted in the deformation of preexisting valves of corneal lymphatic capillaries. In alkali-burn corneas, ephrinB2 and EphB4 were highly expressed in LECs of valve-forming areas. Subconjunctival EphB4/Fc injections perturbed the morphologic maturation of new lymphatic valves, leading to reflux of FITC-dextran to peripheral lymphatic branches.

Conclusions.: The results demonstrate a pivotal role of ephrinB2–EphB4 signals in the formation and maintenance of funnel-shaped valves in corneal lymphatic capillaries, and further suggest the potential of ephrinB2–EphB4 signals as a target to therapeutically manipulate corneal lymphangiogenesis.