Corneal lymphangiogenesis facilitates ocular surface inflammation and cell trafficking in dry eye disease

Abstract

Purpose: While the normal cornea has limited innervation by the lymphatic system, chronic immune-inflammatory disorders such as dry eye (DE) can induce lymphangiogenesis in the ocular surface. Using a conditional knock-down murine model, Lyve-1(Cre);VEGFR2(flox) mice, this study investigated the role of lymphangiogenesis in the pathophysiology of DE. Methods: DE was induced in both wild type (WT) B6 and Lyve-1(Cre);VEGFR2(flox) mice. Tissue immunostaining and volumetric gross measurements were used to assess changes in the ocular surface, skin, and lymph nodes (LNs). The expression of lymphangiogenic factors (TNF-alpha, IL-6/-8/-12/-17, VEGF-C/-D, IFN-gamma, VEGFR-2/-3, Lyve-1, and podoplanin) and the frequency of immune cells (CD4, CD11b, and CD207) on the ocular surface and lacrimal glands were quantified by real-time polymerase chain reaction and flow cytometry. Results: Compared to WT mice, there were fewer lymphatic vessels and a reduction in lymphangiogenic markers in the ocular surface and skin of Lyve-1(Cre);VEGFR2(flox) mice. After DE induction, mRNA levels of TNF-alpha, IL-8, and IFN-gamma were significantly reduced in Lyve-1(Cre);VEGFR2(flox) mice compared to WT mice (p < .01). Surprisingly, the LNs from Lyve-1(Cre);VEGFR2(flox) mice with DE were significantly smaller and populated by fewer dendritic cells and effector T cells than those from WT mice (p < .001). Furthermore, immunostaining showed corneal nerves in the DE-induced Lyve-1(Cre);VEGFR2(flox) mice were notably intact like in the naive condition. Conclusions: Inhibition of lymphangiogenesis in the cornea effectively attenuates not only the inflammatory response including trafficking of immune cells but also preserves corneal nerves under desiccating stress. Corneal lymphangiogenesis might be a contributing factor in deterioration on the ocular surface homeostasis. (C) 2018 Elsevier Inc. All rights reserved.