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Wanyu Zhang, Clifton Smith, Zhijie Li, Alan Burns; A Role for Macrophage-derived Interleukin-20 in Mouse Corneal Epithelial Wound Healing. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5235. doi: https://doi.org/.
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After corneal epithelial injury, the ensuing inflammatory response is necessary for efficient wound healing. While beneficial healing effects are attributed to recruited neutrophils and platelets, this study will determine if corneal macrophages (MΦs) and macrophage-derived IL-20 contribute to wound healing.
Anesthetized adult female wildtype C57BL/6 mice received 2.0 mm wide central corneal epithelial abrasions with a golf-club spud. Injured corneas were topically treated every 4h up to 24h with 10ul of neutralizing IL-20 antibody (200ug/ml) or control antibody (non-immune isotype matched IgG). To examine the effects of recombinant IL-20 (rIl-20) on epithelial wound healing, wildtype mice with and without neutrophil depletion (anti-Ly6G) and mutant mice known to have reduced neutrophil infiltration (γδ T cell deficient mice (TCR-/-) and CD11a deficient mice (CD11a-/-)) received 10µL of rIL-20 dissolved in phosphate buffered saline (200ng/mL) every 4h up to 24h, while appropriate control mice received buffer only. The rate of corneal wound closure, the number of dividing basal epithelial cells, number of infiltrating neutrophils and density of epithelial nerves were evaluated. Some corneas were prepared for immunofluorescence microscopy to localize IL-20 and its receptor, IL-20R1.
Topical application of neutralizing IL-20 antibody markedly delayed epithelial wound closure between 8 and 24h post-injury (P<0.05) and, unlike control mice, the wound remained open at 24h. In addition, fewer dividing epithelial cells were detected across the cornea (P<0.05) and epithelial nerve recovery was also markedly depressed by anti-IL-20 treatment, while neutrophil infiltration increased (P<0.05). In wildtype mice, topical application of rIL-20 had no effect on wound closure, but accelerated wound closure, increased epithelial cell division and enhanced nerve recovery were observed in injured neutropenic, TCR-/- and CD11a-/- mice. The already low neutrophil infiltration in TCR-/- mice was further inhibited by rIL-20 treatment (P<0.05). Prior to injury, immunostaining confirmed IL-20R1 was expressed on WT corneal epithelial cells and perivascular limbal MΦs showed positive staining for IL-20.
The data suggest MΦ-derived IL-20 plays a beneficial role in mouse corneal epithelial wound healing and may negatively regulate neutrophil recruitment.
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