Neutrophil interactions with keratocytes during corneal epithelial wound healing: a role for CD18 integrins.
OBJECTIVE
To determine the role of keratocytes and leukocyte beta(2) (CD18) integrins in neutrophil (PMN) migration through the corneal stroma after epithelial scrape injury.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Petrescu
Matei S
MS
Department of Pediatrics, Critical Care Section, Baylor College of Medicine, Houston, TX 77030, USA.
Larry
Chonna L
CL
Bowden
Robert A
RA
Williams
George W
GW
Gagen
Debjani
D
Li
Zhijie
Z
Smith
C Wayne
CW
Burns
Alan R
AR
D000818:Animals; D018821:CD18 Antigens / Q000502:physiology*; D054441:Cell Migration Assays, Leukocyte; D003094:Collagen / Q000648:ultrastructure; D003319:Corneal Stroma / Q000648:ultrastructure*; D004195:Disease Models, Animal; D019573:Epithelium, Corneal / Q000293:injuries* / Q000648:ultrastructure; D005131:Eye Injuries / Q000378:metabolism* / Q000473:pathology; D005347:Fibroblasts / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D020556:Neutrophil Infiltration / Q000502:physiology; D009504:Neutrophils / Q000502:physiology* / Q000648:ultrastructure; D014945:Wound Healing / Q000502:physiology*; D014949:Wounds, Nonpenetrating / Q000378:metabolism* / Q000473:pathology
D018821:CD18 Antigens; D003094:Collagen