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Jin-Hong Chang, Kyuyeon Han, Dimitri T Azar; Roles of VEGFR2 and R3 in the progression and regression of injury-induced corneal lymphangiogenesis. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4283.
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The lymphatic system is essential for fluid homeostasis and immune responses. Vascular endothelial growth factor receptor 2 (VEGFR2) and VEGFR3 have been shown to play major roles in modulating lymphangiogenesis. However, the molecular mechanisms by which these receptors regulate lymphatic growth and regression remain unclear. To characterize the kinetics of injury-induced blood and lymphatic vessel growth, we bred Prox1-GFP/Flt1-dsRed (PGFD) transgenic mice with VEGFR2lox and/or VEGFR3lox mice to generate mice in which we can conditionally delete VEGFR2 or R3 and then visualize injury-induced corneal lymphatic vessel progression and regression in live animals via fluorescence microscopy.
We bred PGFD mice with Prox1-CreERT2, VEGFR2lox and/or VEGFR3lox mice to generate Prox1-CreERT2/VEGFR2lox/PGFD, Prox1-CreERT2/VEGFR3lox/PGFD, and Prox1-CreERT2VEGFR2/3lox/PGFD mice. For lymphatic vessel progression assays, mice received tamoxifen injections (on 5 consecutive days) beginning 5 days prior to total corneal epithelial debridement. For regression assays, mice received tamoxifen (on 5 consecutive days) beginning on thesame day of injury or on day 7 after injury. Injured corneas were imaged using an Axiozoom V16 stereomicroscope and analyzed with Zeiss Zen imaging programs at day 1, 4, 7, 10 and 14. The areas of induced corneal blood and lymphatic vessels were calculated using Adobe Photoshop.
In the control group, without tamoxifen treatment, total corneal epithelial debridement resulted in enhanced corneal angiogenesis and lymphangiogenesis in all three mouse strains. In contrast, deletion of lymphatic endothelial VEGFR2 and/or VEGFR3 in the progression assay abolished the injury-induced corneal lymphangiogenesis in all three mouse strains. In the regression assay with tamoxifen treatment 7 days after corneal injury, no injury-induced corneal lymphangiogenesis was observed in mice with conditional deletion of VEGFR3 and those with conditional deletion of both receptors. However, injury-induced corneal lymphangiogenesis was observed in the mice with VEGFR2 deletion.
Lymphatic endothelial VEGFR2 and VEGFR3 are required for the onset of injury-induced corneal lymphangiogenesis. However, VEGFR2 may not be critical for prevention of pre-existing lymphatic vessel growth.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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