Submitted to: Investigative Ophthalmology and Visual Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2006
Publication Date: 5/1/2006
Citation: Li, Z., Burns, A.R., Smith, C.W. 2006. Two waves of neutrophil emigration in response to corneal epithelial abrasion: Distinct adhesion molecule requirements. Investigative Opthalmology and Visual Science. 47:1947-1955. Interpretive Summary: We have recently found (unpublished data) that in diet-induced obesity, mice exhibit poor wound healing in the cornea. The current paper provides the basic research on the mechanisms of corneal wound healing needed to carry out future studies of reduced wound healing in obese animals. Here we demonstrate that neutrophils (an abundant type of white blood cell) are a key cell type responding to corneal wounds, and they participate in the healing response. Animals deficient in the neutrophil response exhibit reduced wound healing.
Technical Abstract: PURPOSE: Corneal abrasion results in an inflammatory response characterized by leukocyte emigration into the corneal stroma. Adhesion molecules play a critical role in leukocyte emigration to wound sites, but differences are evident in different vascular beds. In this study, the contributions of two families of adhesion molecules to neutrophil emigration into the cornea were investigated. METHODS: Re-epithelialization, patterns of neutrophil influx and CXC chemokine production were assessed in C57Bl/6 mice after removal of a 2-mm diameter area of central corneal epithelium. Comparisons were made between wild-type (WT) mice and mice with targeted deletions of genes for CD18 (CD18(-/-)) or P- and E-selectin (P/E-sel(-/-)) or in mice with antibody-induced neutropenia. RESULTS: Wild-type mice exhibited neutrophil emigration in two waves, the first peaking at 18 hours and the second at 30 hours after wounding, 6 hours after epithelial wound closure and peak levels of corneal CXCL1. In CD18(-/-) animals, only a single wave of neutrophil influx was seen, and it was temporally and quantitatively equivalent to the second wave in WT. In P/E-sel(-/-) mice, neutrophil influx was markedly depressed throughout the 48-hour observation period. Re-epithelialization was significantly delayed in mice with adhesion molecule deletions and in neutropenic animals. Transfer of wild-type leukocytes into CD18(-/-) mice resulted in neutrophil emigration into the injured cornea within 18 hours of wounding and improved closure of the epithelium. CONCLUSIONS: Neutrophil emigration into corneal stroma after epithelial abrasion occurs in two waves. The first is dependent on CD18 integrins and selectins, whereas the second is CD18-independent but requires selectins. Early leukocyte emigration appears to promote re-epithelialization.