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D. Gagen, S. Dieffenbaugher, E. Brown, Z. Li, C. W. Smith, M. Petrescu, A. R. Burns; Corneal Epithelial Abrasion and Wound Healing in the Mouse: Kinetics of Keratocyte and Stromal Recovery. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3931.
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Corneal epithelial abrasions are among the most common patient complaints presented to ophthalmologists. Because epithelial lesions typically heal in 2-3 days, little attention has been focused on sub-epithelial sequelae. This is surprising since studies in animals reveal epithelial abrasion is accompanied by keratocyte death and stromal edema. Because detailed information on keratocyte and stromal recovery after epithelial abrasion is lacking, we undertook a study to 1) evaluate keratocyte densities and distributions within the normal mouse stroma and 2) assess the kinetics of keratocyte and stromal recovery following a central non-penetrating corneal epithelial abrasion.
2 mm central epithelial abrasion without damage to the basal lamina was performed on right corneas of C57Bl/6 mice. Corneas were excised at 0, 0.25, 1, 4, 14 and 28 days post-injury. Whole mount corneas were stained with a FITC-conjugated leukocyte antibody cocktail plus 100 ug/ml DAPI. The entire whole mount thickness was imaged and keratocyte counts (DAPI positive, FITC negative) were made at central, paracentral, and paralimbal regions using a DeltaVision Spectris inverted microscope.
In the uninjured cornea, more keratocytes (~55%) were distributed in the anterior half of the stroma, across all regions of the cornea. Six hours after epithelial abrasion, there was a 20% increase in stromal thickness due to edema (p<0.05). By 24 hours, the abrasion was covered by a thin layer of epithelial cells. However, as expected, few keratocytes were visible in the anterior half of the central stroma. Full epithelial thickness was restored by 4 days, and central anterior keratocyte density began to recover. As well, keratocyte density in the posterior half increased above baseline by 60% (p<0.05). Stromal edema was no longer evident, and the central corneal stroma had collapsed to 80% of baseline thickness (p<0.05). While corneal stromal thickness rebounded to baseline by 14 days, central anterior keratocytes only recovered to 80% of baseline values (p<0.05) and anterior keratocyte density did not increase further by 4 weeks.
The data show epithelial abrasion induces long lasting and profound changes in stromal organization. While keratocyte recovery in the central anterior stroma is initially rapid, it is also incomplete, and plateaus at 2-4 weeks. Longer studies will be needed to determine if complete keratocyte recovery is possible.
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