Transforming growth factor-β expression in rat eyes with mechanical debridement of corneal epithelium or epithelial flap

PURPOSE: To compare corneal haze and transforming growth factor (TGF)-beta expression in rat eyes with mechanical debridement of corneal epithelium or a chemically induced epithelial flap. SETTING: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea. METHODS: Sixty corneas from 60 Sprague-Dawley rats were treated in 1 of 4 ways using a 2.0 mm trephine: corneal epithelium mechanically removed (Group 1), central cornea exposed to 20% ethanol for 30 seconds (Group 2), corneal epithelial flap made by applying 20% ethanol for 30 seconds and flap amputated (Group 3), corneal epithelial flap repositioned after ethanol-assisted detachment of epithelium as in Group 3 (Group 4). Corneal haze was graded. The TGF-beta expression was measured in corneas and lacrimal glands using reverse transcription polymerase chain reaction and immunohistochemistry until day 30. Semiquantitative analysis was done in a density ratio of TGF-beta/beta-actin with image analyzer and densitometry. RESULTS: Corneal haze was more severe in Groups 1 and 3 than in Groups 2 and 4. By day 7, mRNA expression of TGF-beta2 and type II receptor in corneas had increased more in Groups 1 and 3 than in Groups 2 and 4. In lacrimal glands, only TGF-beta1 in Group 3 increased until day 7. In corneas, staining of both TGF-beta1 and beta2 increased, more prominently in Groups 1 and 3. Lacrimal gland staining was more intense in Groups 1 and 3. CONCLUSION: Well-positioned corneal epithelial flaps may decrease corneal haze by reducing expression of TGF-beta; inadvertent removal of an epithelial flap made by ethanol seems to exacerbate haze by increasing TGF-beta.