Expression of factors related with lymph‐/hem‐angiogenesis in the cornea and conjunctiva during dry eye induction

Abstract

AbstractPurposeCorneal lymphangiogenesis is known to play an important role in the pathogenesis of dry eye disease (DED). And the low‐grade inflammation associated with DED is known as an inducer of lymphangiogenesis without accompanying hemangiogenesis. This study is to evaluate the expression of known factors related with lymph‐/hem‐angiogenesis in the cornea and conjunctiva in the murine DED model.MethodsDED was induced by housing 8‐week‐old female C57BL/6 mice in a controlled environmental chamber that allowed for the relative low humidity (< 25%), continuous regulation of airflow, and temperature (21 to 23ºC) for 3 weeks. Corneal fluorescein score was evaluated to confirm the efficacy of DED induction. Fluorescence images from the corneal whole mounts after immunohistochemical stain for lymphatic vessel endothelial hyaluronan receptor (lyve)‐1 were used for analysis. The expression of m‐RNA of the VEGF‐A, VEGF‐C, VEGF‐D (Figf), Angiopoietin‐2 (Angpt2), and VEGFR3 (flt4) were evaluated by real‐time PCR in the cornea and conjunctiva.ResultsPercentage of the area of lyve‐1+ area of the whole corneal area increased significantly in DED group (5.55 ± 1.45% in DED group versus 3.88 ± 0.74% in control, P=0.015, Mann‐Whitney U test). The expression of Angiopoietin‐2 increased significantly in the cornea (1.38 folds, 95% confidence interval [CI]: 1.03~1.84) and in the conjunctiva (1.36 folds, 95% CI: 1.04~1.77). And the expression of VEGF‐C increased significantly only in the conjunctiva (1.64 folds, 95% CI: 1.21~2.21). However, the expression of VEGF‐D significantly decreased both in the cornea (0.40 folds, 95% CI: 0.32~0.49) and in the conjunctiva (0.44 folds, 95% CI: 0.37~0.52).ConclusionsUnique lymphangiogenesis without hemangiogenesis in DED may be associated with increased expression of Angiopoietin‐2 and VEGF‐C and decreased expression of VEGF‐D. However, the exact interaction of these key factors should be studied further.