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Flavia S. Pelegrino, Cintia S. De Paiva, Stephen C. Pflugfelder; Low Humidity Stress Induces Cornification of Corneal Epithelium in Mice. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3759.
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To investigate the effects of low humidity stress (LHS) on corneal barrier function and cornifield envelope proteins in mice.
C57BL6 aged 6-8 weeks were exposed to an air draft for 15 or 30 days at a relative humidity <30%RH. Untreated (UT) mice were used as control kept in a separate room with relative humidity (>50%). Eyes and adnexae were surgically excised for paraffin or frozen sections. Oregan green dextran (OGD, 70kDa) uptake was used as a measurement of corneal barrier function. Goblet cell density was counted in PAS stained conjunctival sections. Expression of small proline rich protein (SPRR)-2a and metalloproteinase (MMP)-9 was evaluated in cornea sections. Whole mount corneas from each group were immunostained and visualized by laser scanning confocal microscopy. Digital images were acquired and mean apical cell area was measured using LSM Digital analysis software. MMP-9 activity was evaluated by in situ zymography. Epidermal growth factor concentration in tears was measured using a commercial ELISA kit.
Exposure to low humidity stress for 15 days disrupted corneal barrier function, increased expression of MMP-9 and SPRR-2 protein in the corneal epithelium, and decreased the number of PAS+ cells in the conjunctiva. Increased MMP-9 activity was observed in apical layers of the cornea epithelium. Increased desquamation of apical epithelium and decreased apical cell area were observed in whole mount corneas stained with occludin. Tear EGF levels were significantly decreased at 15 days of LHS. All these parameters, except mean cell area, returned to control levels at 30 days.
Low Humidity stress is capable of altering corneal barrier function and stimulating production of cornified envelope precursor protein by the corneal epithelium.
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