Abstract
Purpose: :
Vesicants inflict injury to the corneal epithelial-stromal junction. Activation of matrix metalloproteinases (MMPs) may delay healing of vesicant wounds. Our goal was to characterize mild and moderate mustard injury in a rabbit corneal organ culture model system to determine whether the application of MMP inhibitors for 22 hr after injury would improve healing.
Methods: :
Corneas were dissected from rabbit eyes (PelFreez) and placed in air lifted organ culture. Medium was added up to the corneal-scleral junction. Injuries were induced by applying 20 µl of 10 mM half mustard (CEES), or 10 µl of 10 mM nitrogen mustard to the central cornea. After 2 hours, medium was removed and replaced with either fresh medium or medium plus a counteragent, applying it dropwise to the central cornea. Such media were reapplied 3 times over the couse of the following 22 hours. Corneas were then analyzed by light or electron microscopy (EM).
Results: :
24 hr after exposures, suprabasal epithelial cell nuclei stained well with a modified H&E stain, but basal cells and their nuclei were paler than non-exposed controls. By EM, hemidesmosomes, the basement membrane and the anterior stromal ECM showed distinct signs of degradation. With the matrix metalloproteinase inhibitor Ilomastat, corneas showed improved basal cell-stromal adhesion after vesicant exposure, but adverse effects were not totally ameliorated. Treatment with the tetracycline derivatives sancycline and t-butyl sancycline improved histology on the mild mustard injury incurred by CEES exposure, but did not have a great effect on the moderate or severe nitrogen mustard injuries. Dedimethylamino tetracycline appeared to aggravate vesicant injury.
Conclusions: :
Even mild mustard injury causes some degree of damage to the basal epithelial cells, the basement membrane and the stromal ECM. Sancycline, t-butyl sancycline and Ilomastat treatment improved histology of corneas after 24 hr compared to vesicant-exposed corneas that received no therapeutic agent.
Keywords: cornea: basic science • wound healing • ocular irritancy/toxicity testing