Abstract
Purpose:
A hallmark of acute inflammation is vasodilation. The extravasation of neutrophils and platelets after corneal abrasion is beneficial to wound healing. In mast cell deficient mice (Kitw-sh/w-sh), limbal venule expansion is blunted, there is a marked delay in neutrophil extravasation, and little or no platelet extravasation. The purpose of this study was to examine the relationship between venule expansion and platelet extravasation.
Methods:
Adult C57BL/6 mice were anesthetized and a 2mm central corneal abrasion was made using a golf-club spud or Alger brush. Prior to injury, one group of wild type mice was treated with anti-Ly6G antibody to deplete neutrophils which in turn limits platelet recruitment. A second group had reduced leukocyte CD18 expression (CD18 mutant) with normal neutrophil extravasation but limited platelet recruitment. The third group of wild type injured mice received topical treatment with rIL-20 (200 ng/ml) once every 4h for 24h which inhibits neutrophil and platelet extravasation. A control group of injured wild type mice received phosphate buffered saline topically. At 24h post-injury, excised corneas were immunostained for vessels and platelets. Limbal venule diameters were evaluated and analyzed using the Kolmogorov-Smirnov test.
Results:
Prior to injury, limbal venule diameters were not different across mouse groups. At 24h post-injury, in wild type mice, the average limbal venule diameters increased from 15 μm to 25 μm (p<0.05 compared to uninjured baseline). Injured CD18 mutant mice and mice treated with anti-Ly6G or rIL-20 showed a marked reduction (>70%) in platelet extravasation compared to injured wild type mice. The average venule diameters in injured CD18 mutant mice and mice treated with anti-Ly6G or rIL-20 were similar across the groups, increasing to ~20 μm which was significantly less than that observed in injured wild type mice.
Conclusions:
In three experimental models that significantly reduce platelet extravasation following corneal injury, limbal venule expansion was significantly reduced, suggesting possible functional links between venule expansion and platelet extravasation.