Apoptosis in UV-exposed rabbit corneas

Purpose. Apoptosis was studied in rabbit corneas as a possible mechanism of cell death after photokeratitis induced by different UV wavelengths. Metho d. Fourteen albino rabbit corneas were exposed to 280- and 310-nm UV radiat ion (UVR) in 10-nm full wavebands at doses that cause biomicroscopically si gnificant keratitis (0.12 J/cm(2) for 280 nm and 0.47 J/cm(2) for 310 nm). Animals were killed 24 and 76 h after exposure. Corneas were processed for light and transmission electron microscopy and in situ end labeling of frag mented DNA by using a modification of the TUNEL technique. Results. Corneas exposed to 280-nm UVR showed TUNEL-positive staining only in epithelial ce lls and superficial keratocytes at 24 and 76 h after irradiation. Twenty-fo ur hours after 310-nm UVR exposure, TUNEL-positive staining was present in the epithelial cells, keratocytes throughout the entire thickness of the ce ntral stroma, and in endothelial cells. Seventy-six hours after exposure to 310-nm UVR, keratocytes disappeared throughout the whole thickness of the damaged stroma. Only a few epithelial cells were TUNEL positive at that tim e. Transmission electron microscopy (TEM) verified the occurrence of apopto tic nuclei and cells. Conclusion. Apoptosis appears to be a mechanism of co rneal cell death after WR. The 310-nm UVR caused more extensive damage to t he corneal stroma and endothelium than did the 280-nm UVR.