Submitted to: Investigative Ophthalmology and Visual Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2007
Publication Date: 11/28/2007
Citation: Petrescu, M.S., Larry, C.L., Bowden, R.A., Williams, G.W., Gagen, D., Li, Z., Smith, C.W., Burns, A.R. 2007. Neutrophil interactions with keratocytes during corneal epithelial wound healing: A role for CD18 integrins. Investigative Ophthalmology and Visual Science. 48(11):5023-5029. Interpretive Summary: In response to corneal epithelial injury, emigrated leukocytes (neutrophils) facilitate wound healing but the mechanism of leukocyte migration within the corneal stroma is poorly understood. Using a mouse model of corneal epithelial scrape injury, Petrescu and colleagues found that neutrophils form close surface contacts not only with the extracellular matrix (e.g., collagen) but also with keratocytes. Moreover, the leukocyte integrin adhesion molecule, CD18, mediates neutrophil contact with keratocytes, but not collagen. Since keratocytes form a cellular network within the stroma, this study identifies a novel role for the keratocyte network as a "cellular highway" for leukocyte trafficking during corneal inflammation.
Technical Abstract: The purpose of this study was to determine the role of keratocytes and leukocyte beta(2) (CD18) integrins in neutrophil (PMN) migration through the corneal stroma after epithelial scrape injury. Using C57BL/6 wild-type and CD18(-/-) mice, corneas were excised at 6 hours (wild-type) or 24 hours (CD18(-/-)) after central corneal epithelial abrasion, time points determined previously to have similar levels of emigrated PMNs. Corneas were prepared for ultrastructural morphometric analysis of PMNs, keratocyte networks, and collagen. Transmission electron microscopy revealed intact keratocyte networks within the paralimbus that were morphometrically similar, regardless of epithelial injury or mouse genotype. Secondary to epithelial abrasion, extravasated PMNs within the paralimbus developed close contacts with keratocytes and collagen. In wild-type mice, 40% of the PMN surface was in contact with the keratocyte surface, and this value decreased to 10% in CD18(-/-) mice. PMN contact with collagen was similar in wild-type and CD18(-/-) mice, with approximately 50% of the PMN surface contacting the collagen fibrils. Since corneal edema resulting from scrape injury was similar, regardless of genotype and did not involve structural changes in collagen fibrils, these data favor a direct role for CD18 in mediating PMN contact with keratocytes. The data show that in response to epithelial scrape injury, PMN migration in the corneal stroma involves close contact between keratocytes and collagen. Although PMN-keratocyte contacts require CD18 integrins, contact with collagen is CD18 independent. Fundamentally, PMN migration along keratocyte networks constitutes the beginning of a new experimental concept for understanding leukocyte migration within the wounded cornea.