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Aubrey Hargrave, Paul Landry, Bryce Lewellen, Wanyu Zhang, Zhijie Li, Wayne Smith, Alan Robert Burns; The Role of c-kit in Epithelial Recovery and Nerve Regeneration Following Corneal Abrasion in the Mouse. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4723.
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Corneal abrasion elicits an acute inflammatory response that benefits wound healing, including epithelial recovery and nerve regeneration. Recently, the corneal epithelium was shown to express the c-kit receptor and its ligand, stem cell factor. After corneal abrasion, the absence of epithelial c-kit appears to delay epithelial wound closure but not to diminish cell proliferation. Whether the absence of the c-kit receptor delays epithelial restratification and nerve regeneration is unknown.
Anesthetized wild type C57BL6 and c-kit mutant KitW-sh/W-sh mice received a 2.0 mm central corneal epithelial abrasion using a golf-club spud and were euthanized after 96 hours for epithelial thickness measurements or after 4 weeks for nerve analysis. Age matched uninjured mice served as controls. Excised corneas were labeled with nerve-specific anti-tubulin β III antibody and imaged by immunofluorescence microscopy. A custom Matlab program was used to evaluate epithelial and subbasal nerve density, tortuosity, beading, and branching. For epithelial thickness measurements, excised corneas were fixed, embedded in plastic, transversely sectioned (0.5 μm), stained with toluidine blue, and imaged. Data analysis was performed using analysis of variance and Tukey’s post-test. A P value of <0.05 was considered significant.
Epithelial restratification (thickness and number of cell layers) was not different between wild-type and KitW-sh/W-sh mice at baseline, and both strains of mice showed full restratification by 96 hours after injury. Corneal nerve morphology was not different between mouse strains at baseline. At 4 weeks post-injury in both mouse strains, epithelial nerve density had returned to baseline, while subbasal nerve density was only 40% recovered. Subbasal nerve tortuosity increased for both wild-type and KitW-sh/W-sh mice at 4 weeks post-injury (both 9.62 radians/μm) as compared to uninjured controls (1.03 and 0.74 radians/μm, respectively).
Collectively, from a morphological perspective, the data suggest corneal epithelial structure and innervation are not dependent on c-kit receptor expression. While it has been shown that c-kit is necessary for efficient epithelial wound closure after corneal abrasion, c-kit receptor expression does not appear to be essential for subsequent epithelial restratification or nerve regeneration.
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