Desiccating stress decreases apical corneal epithelial cell size - Modulation by the metalloproteinase inhibitor doxycycline

Purpose: We investigated the effects of desiccating stress on murine corneal apical epithelial cell area and desquamation by using 4 defined parameters and evaluated the effects of the metalloproteinase inhibitor doxycycline on this process. Methods: C57BL/6 mice were subjected to experimental dry eye (EDE) for 5 days without or with topical therapy with doxycycline 0.025% or 0.0025% or vehicle 4 times a day. C57BL/6 mice that were not exposed to desiccating stress served as controls. Whole mount corneas from each group were immunostained for occludin and visualized by laser scanning confocal microscopy. The images were analyzed in a masked fashion, and mean individual cell area, apical cell density, average cell number loss, and average percent loss were recorded. Results: EDE caused a significant decrease in apical corneal cell area (1073 +/- 135.9 mu m(2)), an increase in apical cell density (895.8 +/- 115.4 cells per mm(2)) and a greater percent of epithelial loss (21.29% +/- 13.40%) than controls (1341 +/- 95.28 mu m(2), 714.4 +/- 55.60 cells per mm(2). 2.897% +/- 3.452%, P < 0.001 for all, respectively). Treatment with 0.025% doxycycline preserved cell area (1337 +/- 144.6 mu m(2)) and the apical cell density (721.0 +/- 91.62 cells per mm2) and decreased percentage loss (5.117% +/- 6.757%) compared with the vehicle control group (1154 +/- 88.10 mu m(2), 830.2 +/- 49.76 cells per mm(2), 22.14 +/- 9.616%, P < 0.001 for all, respectively). Conclusions: Desiccating stress decreases apical corneal epithelia] cell area, increases apical cell density, and promotes epithelial cell loss. Treatment with the metalloproteinase inhibitor doxycycline during desiccating stress preserves cell area and apical cell density and prevents EDE-induced corneal epithelial cell loss. These findings suggest that metalloproteinases mediate apical corneal epithelial loss during desiccating stress.